Research ArticleInhibition Effect of Phosphorus Flame Retardants onthe Fire Disasters Induced by Spontaneous Combustion of Coal

Yibo Tang12

1College of Mining Technology Taiyuan University of Technology Taiyuan 030024 China2State Key Laboratory of Coal Resources and Safe Mining China University of Mining and Technology Xuzhou Jiangsu 221116 China

Correspondence should be addressed to Yibo Tang tangyibo11126com

Received 24 October 2016 Accepted 4 January 2017 Published 31 January 2017

Academic Editor Vincenza Crupi

Copyright copy 2017 Yibo Tang This is an open access article distributed under the Creative Commons Attribution License whichpermits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

Coal spontaneous combustion (CSC) generally induces fire disasters in underground mines thus causing serious casualtiesenvironmental pollution and property loss around the world By using six P-containing additives to process three typical coalsamples this study investigated the variations of the self-ignition characteristics of the coal samples before and after treatmentTheanalysis was performed by combining thermogravimetric analysisdifferential scanning calorimetry (TGDSC) Fourier transforminfrared spectrometer (FTIR) and low temperature oxidation Experimental results showed that P-containing inhibitors couldeffectively restrain the heat emitted in the combustion of coal samples and therefore the ignition temperature of the coal sampleswas delayed at varying degrees The combustion rate of the coal samples was reduced as well At the temperatures ranging from50∘C to 150∘C the activation energy of the coal samples after the treatment was found to increase which indicated that the coalsamples were more difficult to be oxidized After being treated with phosphorus flame retardants (PFRs) the content of severalactive groups represented by the C-O structure in the three coal samples was proved to be obviously changed This suggested thatPFRs could significantly inhibit the content of CO generated by the low temperature oxidation of coal and the flame-retardantefficiency grew with the increasing temperature At 200∘C the maximal inhibition efficiency reached approximately 85

1 Introduction

Coal-mine fire hazards caused by CSC have always been oneof the main disasters found in underground mines [1 2]During 2001ndash2013 hundreds of serious fire accidents haveoccurred in China resulting in over 800 casualties [3] It iswell known that the CSC is one of main reasons responsiblefor underground mine fire [4] According to reports firedisasters aroused by CSC in goafs have occurred in a vast areareaching 5659 km2 in Shanxi China at present Accordingly240 million tons of coal resource is lost leading to a directeconomic loss over 15 billion dollars [5 6] CSC can notonly consume valuable coal resource but also generate a largeamount of fumes including CO CO

2 SO2 and NO

119883[7ndash

9] As a consequence it significantly damages and influencesthe atmospheric environment vegetation water and landresources and also induces various geologic hazards [9 10]To prevent such disasters people have developed variousfire preventing and extinguishing methods [11] Initially

yellow mud or sand was used to mix with water to preparegrouting [12] However this kind of material showed poorperformance in some harsh environment Subsequently peo-ple adopted gel [13] foams [14] and so on to control thelow temperature oxidation of coal and prevent fire disastersin goafs But these materials are expensive and the fireextinguishment efficiency mainly depends on the isolationof coal from air In terms of chemical flame retardants thecommonly used ones are inorganic salt including MgCl

2and

CaCl2[15] So far there are few studies on the effects of

P-containing inhibitors Characterized by halogen-free lowsmoke and low toxicity PFRs show a high efficiency in fewamounts and can be used in various fields As a result theyhave been rapidly developed in recent years With excellentthermostability PFRs can generate glassy substances withrich phosphor after dehydration by continuous heatingTheseglassy substances cover the surface of base materials thusisolating the air to hinder the continuous combustion ofmaterial Compounds including ammonium polyphosphate

HindawiJournal of SpectroscopyVolume 2017 Article ID 7635468 10 pageshttpsdoiorg10115520177635468

2 Journal of Spectroscopy

Table 1 Technical parameters of experimental coal samples

Name Proximate analysis Elemental analysis Calorific valueMJsdotkgminus1 Coal rank

Moisture Ash Volatile Fixed carbon C H O N SZhaotong coal 801 2016 4893 3091 5229 392 3066 171 016 1825 LigniteBulianta coal 498 644 3231 6333 8105 413 1346 096 040 3210 SubbituminousXiqu coal 046 1064 2118 7048 9112 476 230 148 043 2732 Bituminous

Table 2 Additives used in the experiment

Name Chemical formula Purity ManufacturerZinc phosphate Zn

3(PO4)2

gt99 Sinopharm Group Co LtdPotassium dihydrogen phosphate KH

2PO4

gt99 Sinopharm Group Co LtdSodium hydrogen phosphate Na

2HPO4

gt99 Sinopharm Group Co LtdAmmonium phosphate (NH

4PO3)n gt98 Taixing Chemical Co Ltd

Trichloroethyl phosphate C6H12Cl3O4P gt99 Chemical amp Materials Co Ltd

Diphenyl hydrogen phosphate C12H11O4P gt99 Chemical amp Materials Co Ltd

and phosphate have been widely used in plastic industry andcan help to improve the flame-retarding properties of plasticsWang et al used microencapsulated red phosphorus andaluminium hypophosphite to jointly inhibit the combustionof polyethylene Based on the obtained results they foundthat using P-containing compounds can reduce the heatemitted in the combustion and enhance the thermostabilityof polyethylene [16] Luo et al synthesized a kind of P-containing epoxy resin with high performance throughaddition reaction showing good inflaming retarding andmechanical properties [17] Hence by using P-containingadditives to deal with coal samples this research studied theinfluence of P-containing additives on the CSC and exploredthe chemical inhibition mechanism of PFRs

2 Experiments

In this study lignite (ZT) collected from Zhaotong in Yun-nan subbituminous coal (BLT) acquired from Bulianta inInner Mongolia and bituminous coal (XQ) from Xiqu inShanxi China were served as the coal samples The specificparameters of these samples are shown in Table 1 To beginwith the fresh coal lump was broken into pieces to selectthe lumps broken with the length in a range of 018ndash025mmas the specimens Then these specimens were dried in avacuum drying oven at 50∘C until their masses maintainedunchanged Next six kinds of P-containing agents were usedas additives (as demonstrated in Table 2) to prepare thesolution with a concentration of 5 Afterwards 100 g of coalsamples were immersed in 500ml solution for 24 h followedby conducting repeated drying FTIR with the wavenumbervarying from 500 to 4000 cmminus1 was used to analyze thecoal samples before and after the treatment Meanwhileexperiments were carried out using TGDSC to analyze thethermal change of the coal samples in the combustion processin the air at a heating rate of 10∘Cmin In addition atemperature programming device (as illustrated in Figure 1)was used to test the generation of CO in the coal samplesbefore and after the treatment with P-containing agents as

well as to evaluate the inhibition effects Air was flowed at20mlmin into this devicewith the temperature ranging from60∘C to 200∘C at a heating rate of 1∘Cmin

3 Results and Discussion

31 Infrared Spectroscopic Analysis As demonstrated in Fig-ure 2 the absorption peaks of the infrared absorptionspectrum for the BLT coal mainly included the out-of-planestretching vibration induced in case heteroatoms at 508ndash872replaced C-H the C-O vibration between 1077 and 1374the vibration of aromatic-ring C=C band at 1591ndash1601 cmminus12851 cmminus1 and the vibration of -CH

2- at 2921 cmminus1 as well as

the vibration of OH-stretching bands at 3006ndash3537 cmminus1 Forthe infrared absorption spectrum of the XQ coal the stretch-ing vibration of heteroatoms between 555 and 914 cmminus1 theC-O vibration at 1008 cmminus1 the vibration of aromatic-ringC=C bands at 1437ndash1607 cmminus1 and the vibration of -CH

2- at

2847ndash2919 cmminus1 were primarily contained In addition thefollowing absorption peaks were observed in the infraredspectrum for the ZT coal the absorption peak of heteroatomsat 561ndash795 cmminus1 the stretching vibration of C-O at 1003ndash1342 cmminus1 and the vibration ofOH-stretching bands at 3025ndash3697 cmminus1 After the treatment using P-containing additivesobvious changes happened to the infrared absorption spectraof these three coal samples For example the absorptionpeak for the OH structure of the ZT coal at 3464 cmminus1 wasenhanced to varying degrees while the content of the C-O was apparently reduced As to the BLT coal the numberof -CH

2- and C-O structures was obviously lowered As to

the XQ coal new absorption peaks representing the OHstructure occurred at 3349 cmminus1 meanwhile the absorptionpeaks for the stretching vibration of C-O were weakened at1054 cmminus1 In general the C=C structures in these three coalsamples exhibited moderate variation while the content ofthe C-O structure reduced The C-O structure is the criticalstructure influencing the low temperature oxidation of coal[18] which revealed that phosphorous flame retardants can

Journal of Spectroscopy 3

Recorder

Injector port

Detector

Con

trol v

alve

Thermodetector

Reactor

Sensor

Con

trol p

anel

Dry

air

Carr

ier g

as

Control valve

Furnace Column oven

Figure 1 The experimental setup

Coal-BDPCoal-TCEPCoal-APPCoal-K

Coal-NaCoal-ZnRaw coal

OH-CH2-

C=C

C-O

Wavenumber (cmminus1)5001000150020002500300035004000

40

60

80

100

120

Tran

smitt

ance

()

(a) ZT coal

Coal-BDPCoal-TCEPCoal-APPCoal-K

Coal-NaCoal-ZnRaw coal

OH

-CH2-

C=C

C-O

Wavenumber (cmminus1)5001000150020002500300035004000

20

40

60

80

100

Tran

smitt

ance

()

(b) BLT coal

Coal-BDPCoal-TCEPCoal-APPCoal-K

Coal-NaCoal-ZnRaw coal

OH -CH2-

C=C

C-O

Wavenumber (cmminus1)5001000150020002500300035004000

60

70

80

90

100

110

Tran

smitt

ance

()

(c) XQ coal

Figure 2 The FTIR of coal samples before and after treatment

4 Journal of Spectroscopy

200 400 600 800

Temperature (∘C)

0

20

40

60

80

100

Mas

s (

)

Coal-DBP

Coal-TCEPCoal-APPCoal-K

Coal-NaCoal-Zn

Raw coal

T1

T2

T3

(a) ZT coal

200 400 600 800

Temperature (∘C)

Coal-BDP

Coal-TCEPCoal-APPCoal-K

Coal-NaCoal-Zn

Raw coal

0

20

40

60

80

100

Mas

s (

)

T1

T2

T3

(b) BLT coal

200 400 600 800

Temperature

0

20

40

60

80

100

Mas

s (

)

Coal-BDP

Coal-TCEPCoal-APPCoal-K

Coal-NaCoal-Zn

Raw coal

T1

T2

T3

(c) XQ coal

Figure 3 The TG curves of coal samples before and after treatment

weaken the active structures including oxygen-containingfunctional groups in coal thus affecting the low temperatureoxidation of coal

32 Thermal Analysis Based on the thermal analysis it wasfound that after the treatment using P-containing additivesthe thermogravimetric curves of the coal samples varied indifferent degrees According to Figure 3 the combustionof coal can be divided into three stages precombustioncombustion and stabilization Before 200∘C all three coalsamples show similar trend in TG and DSC curves The P-containing inhibitors play a significant role on the control-ling of low temperature oxidation And this phenomenon

remains with the temperature increasing For the ZT browncoal raw coal was gradually oxidized with the increasingtemperature before 200∘C while it was rapidly combustedand decomposed when the temperature varied from 250∘C to300∘C After the temperature reached 600∘C the combustionbasically stopped and the mass of the coal maintained stableAfter the addition of the P-containing inhibitors the coalwas slowly burned and it can be found that both the criticaltemperature 119879

1and combustion temperature 119879

2of the coal

were obviously postponed and the mass loss rate of the coalwas also slowed down Similarly as shown in Figure 4 thedifferential scanning calorimetry (DSC) curve of the ZT coalindicated that the heat emitted by the treated coal sample

Journal of Spectroscopy 5

352∘C 401

∘C503

∘C

464∘C

DSC

(mW

mg)

015

010

005

000

minus005

minus010

200 400 600 800

Temperature (∘C)

Coal-DBP

Coal-TCEPCoal-APPCoal-K

Coal-NaCoal-Zn

Raw coal

(a) ZT coalD

SC (m

Wm

g)

200 400 600 800

Temperature (∘C)

Coal-BDP

Coal-TCEPCoal-APPCoal-K

Coal-NaCoal-Zn

Raw coal

505∘C

551∘C

686∘C

14

12

10

8

6

4

2

0

minus2

minus4

(b) BLT coal

200 400 600 800

Temperature

Coal-BDP

Coal-TCEPCoal-APPCoal-K

Coal-NaCoal-Zn

Raw coal

DSC

(mW

mg)

14

12

10

8

6

4

2

0

minus2

minus4

735∘C

669∘C 680

∘C

(c) XQ coal

Figure 4 The DSC curves of coal samples before and after treatment

was also changed not only the heat released reduced butalso the temperature at which the greatest exothermic peakdelayed occurred In contrast the BLT and XQ coal alsoshowed similar rules that is the heat released by the coalafter the treatment was significantly lowered For examplethe exothermic peak of ZT raw coal in DSC curve is 352∘CAfter the treatment by BDP this temperature postpones to503∘C The masses of these two kinds of coal samples wereslightly changed owing to the addition of P-containing flameretardants before 200∘C Between 200 to 400∘C this tendencyhas been further strengthened At 300∘C the heat flux of XQraw coal is 1486mWmg while the date of coal treated byTCEP is only 0263mWmg However after the temperature

reaches 400∘C the coal samples were burned and thereforeremarkable difference was shown to the mass loss rates of thecoal samples before and after the treatment

This suggested that PFRs can be used to effectively controlthe combustion of coal

The oxygenolysis of coal was a typical gas-solid reactionAssuming that reaction order of coal was 1 according tochemical reaction kinetics the activation energy of thecoal was calculated by adopting the Coats-Redfern integralformula [19]

ln [119892 (119886)1198792 ] = ln [119860119877120573119864119886

(1 minus 2119877119879119864119886

)] minus 119864119877119879 (1)

6 Journal of Spectroscopy

Untreated ZTZT-KZT-NaZT-Zn

Zn-APPZT-BDPZT-TCEP

40 60 80 100 120 140 160 180 200 220

0

2000

4000

6000

8000

10000

12000

14000

16000

CO em

issio

n (p

pm)

Temperature (∘C)

(a) ZT coal

40 60 80 100 120 140 160 180 200 220

Untreated BLTBLT-KBLT-NaBLT-Zn

BLT-APPBLT-BDPBLT-TCEP

0

2000

4000

6000

8000

10000

12000

14000

CO em

issio

n (p

pm)

Temperature (∘C)

(b) BLT coal

40 60 80 100 120 140 160 180 200 220

Untreated XQXQ-KXQ-NaXQ-Zn

XQ-APPXQ-BDPXQ-TCEP

0

2000

4000

CO em

issio

n (p

pm)

Temperature (∘C)

(c) XQ coal

Figure 5 The CO emission of coal samples before and after treatment

where 119886 represented transformation percentage of coal inoxygenolysis process 120573 represented heating rate and 119892(119886)was integral formula of function model which reflectedmechanism of oxidation reaction of coal 119892(119886) = minus ln(1 minus119886) Meanwhile 119905 was reaction time 119879 was reaction tem-perature 119860 was preexponential factor 119864

119886was activation

energy induced by oxygenolysis of coal and 119877 representedgas constant Based on mechanism of the chemical reactionkinetics the construction on 119897119879 was performed by utilizingln(minus ln(1 minus 119886)1198792) Besides according to the obtained slopeactivation energy 119864

119886of the reaction was expected to be

calculated According to Table 3 the activation energy of thecoal samples after the treatment was improved to differentdegrees when the temperature varied from 50∘C to 150∘C

in comparison with those before the treatment After thetreatment using inorganic phosphorus agents the coal dealtwith zinc phosphate showed a significant change to theactivation energy In contrast the optimal effects were foundto the coal treated with the organic phosphorus agent tris(2-chloroethyl) phosphate (TCEP) The improvement of theactivation energy indicated that the higher the energy neededfor the low temperature oxidation of coal is themore difficultthe reaction happens

33 Oxidation Products As seen in Figure 5 as an index gasof CSC the CO released in the oxidation of coal samplespresented increased concentrations with the temperatureHowever after the treatment using PFRs the concentrations

Journal of Spectroscopy 7

Table 3 Activation energy of the coal samples before and after treatment

Coal samples Activation energy(kJsdotmolminus1)Raw coal Coal-K Coal-Na Coal-Zn Coal-BDP Coal-APP Coal-TCEP

ZT 746 764 773 757 981 814 1146BLT 761 832 783 805 821 906 1152XQ 1198 1301 1247 1265 1319 1426 1789

of CO caused by the combustion of coal samples apparentlyvaried For the XQ coking coal before the treatment 259 ppmof CO was generated in the oxidation process at 100∘CHowever after the treatment the concentration of CO pro-duced reduced to 156 ppm at minimum With the increasingtemperature the coal samples treated with TCEP generated493 ppm of CO at 200∘C Similar rules were also shown tothe BLT and ZT coal At 200∘C the concentrations of COreleased by the BLT coal before and after the treatment were10994 ppm and 1345 ppm separately while those emitted bythe ZT coal were 15732 ppm at maximum and 2240 ppm atminimumThe inhibiting efficiency is expressed as shown inthe following formula

119864 = Cr minus CtCrtimes 100 (2)

where 119864 is the inhibiting rate of the inhibitor to the coalsample Cr denotes the amount of CO released from theraw coal in the experiment with the unit of 10minus6 Ct showsthe amount of CO released from the coal treated with theinhibitor under the same condition with the unit of 10minus6

According to the results calculated using formula (2) themaximal inhibiting rates of the phosphorous flame retardantsto the ZT BLT and XQ coal were shown to be 535 529and 396 at 100∘C respectively While these values changedto 857 871 and 864 at 200∘C separatelyThis revealedthat compared with the combustion at a temperature lowerthan 100∘C the phosphorous flame retardants show moreobvious inhibition effects on the CSC at a high temperatureBesides comparing with the CO production the CO

2and

C2H4emission show the similar performance after the

treatment of PFRs (Figures 6 and 7) For example the ZT coaltreated by TCEP has only 5527 ppm CO

2emission at 200∘C

while the raw coal peaks at 39343 ppm At 200∘C the C2H4

yield of BLT coal climbs to 432 ppm but the coal treated byammonium phosphate (APP) only reaches 141 ppm

34 Flame-Retardant Mechanism With the application ofPFRs phosphorus compounds were decomposed in thecombustion process of polymers with P-containing flameretardants owing to the effect of heat accompanying with thefollowing changes [20]

P-containing compoundsheating997888997888997888997888997888rarr

phosphoric acidheating997888997888997888997888997888rarr metaphosphoric acid

heating997888997888997888997888997888rarrpolymetaphosphate

(3)

Polymetaphosphate as a nonvolatile stable compound coverson the surface of the polymer thus forming a charring layerSince no flaming evaporative combustion or decomposi-tion combustion would happen to simple substance carbonpolymetaphosphate can inhibit the combustion In additionsince phosphoric acid and polymetaphosphate show strongdehydration properties carbonized films were formed on thesurface of the polymer thus inhibiting the combustion Thisis the flame-retardant mechanism of PFRs in the condensedphase of polymers PFRs are also a kind of radical scavengersThe mass-spectrometric technique revealed that PO wasgenerated in any P-containing compounds in the combustionof polymers It can combine with the hydrogen atoms in theflaming area thus restraining the flaming [21] The specificaction is expressed as

POlowast +Hlowast 997888rarr HPOlowast (4)

HPOlowast +Hlowast 997888rarr H2+ POlowast (5)

The phosphorus could inhibit the self-ignition of coal effi-ciently Superabundant phosphorus in coal also work againstthe clean and efficient utilization of coal When the coal wasadopted as boiler fuel P-containing compounds in coal willdecompose at high temperature and then form sedimentswhich are difficult to clear on the heating surface of boilerMoreover during the iron-making and steel-making processthe existence of phosphorus elementwill influence the qualityof iron and steel As the results the content of phosphorus incoal is strictly limited around the world Considering safetyfactors phosphorus flame retardants could be widely appliedin the abandoned area of colliery such as gob goaf and coalwaste heap However we still need comprehensively assess-ment before being utilized in storage and transportation ofcoal

4 Conclusions

It is essential to use effective flame retardants for the pre-vention of CSC so as to further guarantee the mine safetyAlthough PFRs have played a significant role in the industrialproduction of polymers more exploration is still neededin its role in the inhibition of CSC Laboratorial researchwas attempted to explore the inhibition mechanism of PFRson the organic functional groups in coal molecules Theexperimental results revealed that phosphorus could effec-tually inhibit CSC at a high temperature interval Althoughcertain effects could also be emerged at a low temperaturerange they were less obvious compared with that at a hightemperature with a maximal inhibiting rate above 80

8 Journal of Spectroscopy

0

5000

10000

15000

20000

25000

30000

35000

40000

45000

CO2

emiss

ion

(ppm

)

Untreated ZTZT-KZT-NaZT-Zn

Zn-APPZT-BDPZT-TCEP

40 60 80 100 120 140 160 180 200 220

Temperature (∘C)

(a) ZT coalCO

2em

issio

n (p

pm)

40 60 80 100 120 140 160 180 200 220

28000

24000

20000

16000

12000

8000

4000

0

Untreated BLTBLT-KBLT-NaBLT-Zn

BLT-APPBLT-BDPBLT-TCEP

Temperature (∘C)

(b) BLT coal

CO2

emiss

ion

(ppm

)

40 60 80 100 120 140 160 180 200 220

0

2000

4000

6000

8000

Untreated XQXQ-KXQ-NaXQ-Zn

XQ-APPXQ-BDPXQ-TCEP

Temperature (∘C)

(c) XQ coal

Figure 6 The CO2emission of coal samples before and after treatment

The results obtained using the FTIR indicated that for thecoal samples with different coal ranks the C-O structuresin the coal after the treatment were obviously weakenedSimilar results were also obtained in the thermal analysis andtemperature programming experiment using P-containingcompounds can reduce the heat released in the combustion ofcoal and increase the difficulty in the reaction between coaland oxygen This research provides a favorable reference tothe application of P-containing inhibitors

Competing Interests

The author declares that they have no competing interests

Acknowledgments

This study is funded by the Project of China National NaturalScience Foundation (no 51604185) Open Projects of StateKey Laboratory of Coal Resources and Safe Mining CUMT

Journal of Spectroscopy 9C 2

H4

emiss

ion

(ppm

)

1000

800

600

400

200

0

Untreated ZTZT-KZT-NaZT-Zn

Zn-APPZT-BDPZT-TCEP

40 60 80 100 120 140 160 180 200 220

Temperature (∘C)

(a) ZT coal

40 60 80 100 120 140 160 180 200 220

minus100

0

100

200

300

400

500

C 2H

4em

issio

n (p

pm)

Untreated BLTBLT-KBLT-NaBLT-Zn

BLT-APPBLT-BDPBLT-TCEP

Temperature (∘C)

(b) BLT coal

40 60 80 100 120 140 160 180 200 220

minus50

0

50

100

150

200

250

C 2H

4em

issio

n (p

pm)

Untreated XQXQ-KXQ-NaXQ-Zn

XQ-APPXQ-BDPXQ-TCEP

Temperature (∘C)

(c) XQ coal

Figure 7 The C2H4emission of coal samples before and after treatment

(SKLCRSM15KF07) and the Research Project Supported byShanxi Scholarship Council of China (2015-037)

References

[1] J Zhang W Choi T Ito K Takahashi and M Fujita ldquoMod-elling and parametric investigations on spontaneous heating incoal pilerdquo Fuel vol 176 pp 181ndash189 2016

[2] C Avila T Wu and E Lester ldquoPetrographic characterizationof coals as a tool to detect spontaneous combustion potentialrdquoFuel vol 125 pp 173ndash182 2014

[3] Q Deng YWang andM Liu ldquoStatistic analysis and enlighten-ment on coal mine accident of China from 2001sim2013 periodsrdquoCoal Technology vol 33 no 9 pp 73ndash75 2014

[4] Y Tang and S Xue ldquoLaboratory study on the spontaneouscombustion propensity of lignite undergone heating treatmentat low temperature in inert and low-oxygen environmentsrdquoEnergy amp Fuels vol 29 no 8 pp 4683ndash4689 2015

[5] R Song ldquoGeological exploration and treatment method ofspontaneous combustion of coal seamrdquo in Coal Geology Bureauof Shanxi Province Taiyuan pp 65ndash68 2012

[6] J Liu E Wang D Song S Wang and Y Niu ldquoEffect of rockstrength on failuremode andmechanical behavior of compositesamplesrdquo Arabian Journal of Geosciences vol 8 no 7 pp 4527ndash4539 2015

[7] Y Tang ldquoSources of underground CO crushing and ambienttemperature oxidation of coalrdquo Journal of Loss Prevention in theProcess Industries vol 38 pp 50ndash57 2015

10 Journal of Spectroscopy

[8] J C Hower J M K OrsquoKeefe K R Henke et al ldquoGaseousemissions and sublimates from the Truman Shepherd coal fireFloyd County Kentucky a re-investigation following attemptedmitigation of the firerdquo International Journal of Coal Geology vol116-117 pp 63ndash74 2013

[9] G B Stracher and T P Taylor ldquoCoal fires burning out of controlaround the world thermodynamic recipe for environmentalcatastropherdquo International Journal of Coal Geology vol 59 no1-2 pp 7ndash17 2004

[10] C L Dias M L S Oliveira J C Hower S R Taffarel R MKautzmann and L F O Silva ldquoNanominerals and ultrafineparticles from coal fires from Santa Catarina South BrazilrdquoInternational Journal of Coal Geology vol 122 pp 50ndash60 2014

[11] B Taraba and Z Pavelek ldquoInvestigation of the spontaneouscombustion susceptibility of coal using the pulse flow calori-metric method 25 years of experiencerdquo Fuel vol 125 pp 101ndash105 2014

[12] Y Yang Z Li S Hou F Gu S Gao and Y Tang ldquoThe shortestperiod of coal spontaneous combustion on the basis of oxidativeheat release intensityrdquo International Journal of Mining Scienceand Technology vol 24 no 1 pp 99ndash103 2014

[13] Y Lu and B Qin ldquoMechanical properties of inorganic solidifiedfoam for mining rock fracture fillingrdquoMaterials Express vol 5no 4 pp 291ndash299 2015

[14] L Zhang B Qin B Shi Q Wu and J Wang ldquoThe fire extin-guishing performances of foamed gel in coal minerdquo NaturalHazards vol 81 no 3 pp 1957ndash1969 2016

[15] Y-B Tang Z-H Li Y I Yang D-J Ma and H-J Ji ldquoEffect ofinorganic chloride on spontaneous combustion of coalrdquo Journalof the Southern African Institute of Mining and Metallurgy vol115 no 2 pp 87ndash92 2015

[16] D K Wang H He and P Yu ldquoFlame-retardant and thermaldegradation mechanism of low-density polyethylene modifiedwith aluminum hypophosphite and microencapsulated redphosphorusrdquo Journal of Applied Polymer Science vol 133 no 13Article ID 43225 2016

[17] Q Luo Y Yuan C Dong S Liu and J Zhao ldquoHighperformance fire-retarded epoxy imparted by a novelphenophosphazine-containing antiflaming compound atultra-low loadingrdquoMaterials Letters vol 169 pp 103ndash106 2016

[18] Y Tang ldquoAnalysis of coals with different spontaneous com-bustion characteristics using infrared spectrometryrdquo Journal ofApplied Spectroscopy vol 82 no 2 pp 316ndash321 2015

[19] Y Tang ldquoA laboratorial study of spontaneous combustioncharacteristics of the oil shale in Fushun Chinardquo CombustionScience and Technology vol 188 no 6 pp 997ndash1010 2016

[20] E D Weil and S V Levchik ldquo13-Overview of modes of actionand interaction of flame retardantsrdquo in Flame Retardants pp323ndash338 Hanser 2nd edition 2016

[21] Y Tang ldquoInhibition of low-temperature oxidation of bitumi-nous coal using a novel phase-transition aerosolrdquo Energy ampFuels vol 30 no 11 pp 9303ndash9309 2016

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CatalystsJournal of

Journal of Spectroscopy 3

Recorder

Injector port

Detector

Con

trol v

alve

Thermodetector

Reactor

Sensor

Con

trol p

anel

Dry

air

Carr

ier g

as

Control valve

Furnace Column oven

Figure 1 The experimental setup

Coal-BDPCoal-TCEPCoal-APPCoal-K

Coal-NaCoal-ZnRaw coal

OH-CH2-

C=C

C-O

Wavenumber (cmminus1)5001000150020002500300035004000

40

60

80

100

120

Tran

smitt

ance

()

(a) ZT coal

Coal-BDPCoal-TCEPCoal-APPCoal-K

Coal-NaCoal-ZnRaw coal

OH

-CH2-

C=C

C-O

Wavenumber (cmminus1)5001000150020002500300035004000

20

40

60

80

100

Tran

smitt

ance

()

(b) BLT coal

Coal-BDPCoal-TCEPCoal-APPCoal-K

Coal-NaCoal-ZnRaw coal

OH -CH2-

C=C

C-O

Wavenumber (cmminus1)5001000150020002500300035004000

60

70

80

90

100

110

Tran

smitt

ance

()

(c) XQ coal

Figure 2 The FTIR of coal samples before and after treatment

4 Journal of Spectroscopy

200 400 600 800

Temperature (∘C)

0

20

40

60

80

100

Mas

s (

)

Coal-DBP

Coal-TCEPCoal-APPCoal-K

Coal-NaCoal-Zn

Raw coal

T1

T2

T3

(a) ZT coal

200 400 600 800

Temperature (∘C)

Coal-BDP

Coal-TCEPCoal-APPCoal-K

Coal-NaCoal-Zn

Raw coal

0

20

40

60

80

100

Mas

s (

)

T1

T2

T3

(b) BLT coal

200 400 600 800

Temperature

0

20

40

60

80

100

Mas

s (

)

Coal-BDP

Coal-TCEPCoal-APPCoal-K

Coal-NaCoal-Zn

Raw coal

T1

T2

T3

(c) XQ coal

Figure 3 The TG curves of coal samples before and after treatment

weaken the active structures including oxygen-containingfunctional groups in coal thus affecting the low temperatureoxidation of coal

32 Thermal Analysis Based on the thermal analysis it wasfound that after the treatment using P-containing additivesthe thermogravimetric curves of the coal samples varied indifferent degrees According to Figure 3 the combustionof coal can be divided into three stages precombustioncombustion and stabilization Before 200∘C all three coalsamples show similar trend in TG and DSC curves The P-containing inhibitors play a significant role on the control-ling of low temperature oxidation And this phenomenon

remains with the temperature increasing For the ZT browncoal raw coal was gradually oxidized with the increasingtemperature before 200∘C while it was rapidly combustedand decomposed when the temperature varied from 250∘C to300∘C After the temperature reached 600∘C the combustionbasically stopped and the mass of the coal maintained stableAfter the addition of the P-containing inhibitors the coalwas slowly burned and it can be found that both the criticaltemperature 119879

1and combustion temperature 119879

2of the coal

were obviously postponed and the mass loss rate of the coalwas also slowed down Similarly as shown in Figure 4 thedifferential scanning calorimetry (DSC) curve of the ZT coalindicated that the heat emitted by the treated coal sample

Journal of Spectroscopy 5

352∘C 401

∘C503

∘C

464∘C

DSC

(mW

mg)

015

010

005

000

minus005

minus010

200 400 600 800

Temperature (∘C)

Coal-DBP

Coal-TCEPCoal-APPCoal-K

Coal-NaCoal-Zn

Raw coal

(a) ZT coalD

SC (m

Wm

g)

200 400 600 800

Temperature (∘C)

Coal-BDP

Coal-TCEPCoal-APPCoal-K

Coal-NaCoal-Zn

Raw coal

505∘C

551∘C

686∘C

14

12

10

8

6

4

2

0

minus2

minus4

(b) BLT coal

200 400 600 800

Temperature

Coal-BDP

Coal-TCEPCoal-APPCoal-K

Coal-NaCoal-Zn

Raw coal

DSC

(mW

mg)

14

12

10

8

6

4

2

0

minus2

minus4

735∘C

669∘C 680

∘C

(c) XQ coal

Figure 4 The DSC curves of coal samples before and after treatment

was also changed not only the heat released reduced butalso the temperature at which the greatest exothermic peakdelayed occurred In contrast the BLT and XQ coal alsoshowed similar rules that is the heat released by the coalafter the treatment was significantly lowered For examplethe exothermic peak of ZT raw coal in DSC curve is 352∘CAfter the treatment by BDP this temperature postpones to503∘C The masses of these two kinds of coal samples wereslightly changed owing to the addition of P-containing flameretardants before 200∘C Between 200 to 400∘C this tendencyhas been further strengthened At 300∘C the heat flux of XQraw coal is 1486mWmg while the date of coal treated byTCEP is only 0263mWmg However after the temperature

reaches 400∘C the coal samples were burned and thereforeremarkable difference was shown to the mass loss rates of thecoal samples before and after the treatment

This suggested that PFRs can be used to effectively controlthe combustion of coal

The oxygenolysis of coal was a typical gas-solid reactionAssuming that reaction order of coal was 1 according tochemical reaction kinetics the activation energy of thecoal was calculated by adopting the Coats-Redfern integralformula [19]

ln [119892 (119886)1198792 ] = ln [119860119877120573119864119886

(1 minus 2119877119879119864119886

)] minus 119864119877119879 (1)

6 Journal of Spectroscopy

Untreated ZTZT-KZT-NaZT-Zn

Zn-APPZT-BDPZT-TCEP

40 60 80 100 120 140 160 180 200 220

0

2000

4000

6000

8000

10000

12000

14000

16000

CO em

issio

n (p

pm)

Temperature (∘C)

(a) ZT coal

40 60 80 100 120 140 160 180 200 220

Untreated BLTBLT-KBLT-NaBLT-Zn

BLT-APPBLT-BDPBLT-TCEP

0

2000

4000

6000

8000

10000

12000

14000

CO em

issio

n (p

pm)

Temperature (∘C)

(b) BLT coal

40 60 80 100 120 140 160 180 200 220

Untreated XQXQ-KXQ-NaXQ-Zn

XQ-APPXQ-BDPXQ-TCEP

0

2000

4000

CO em

issio

n (p

pm)

Temperature (∘C)

(c) XQ coal

Figure 5 The CO emission of coal samples before and after treatment

where 119886 represented transformation percentage of coal inoxygenolysis process 120573 represented heating rate and 119892(119886)was integral formula of function model which reflectedmechanism of oxidation reaction of coal 119892(119886) = minus ln(1 minus119886) Meanwhile 119905 was reaction time 119879 was reaction tem-perature 119860 was preexponential factor 119864

119886was activation

energy induced by oxygenolysis of coal and 119877 representedgas constant Based on mechanism of the chemical reactionkinetics the construction on 119897119879 was performed by utilizingln(minus ln(1 minus 119886)1198792) Besides according to the obtained slopeactivation energy 119864

119886of the reaction was expected to be

calculated According to Table 3 the activation energy of thecoal samples after the treatment was improved to differentdegrees when the temperature varied from 50∘C to 150∘C

in comparison with those before the treatment After thetreatment using inorganic phosphorus agents the coal dealtwith zinc phosphate showed a significant change to theactivation energy In contrast the optimal effects were foundto the coal treated with the organic phosphorus agent tris(2-chloroethyl) phosphate (TCEP) The improvement of theactivation energy indicated that the higher the energy neededfor the low temperature oxidation of coal is themore difficultthe reaction happens

33 Oxidation Products As seen in Figure 5 as an index gasof CSC the CO released in the oxidation of coal samplespresented increased concentrations with the temperatureHowever after the treatment using PFRs the concentrations

Journal of Spectroscopy 7

Table 3 Activation energy of the coal samples before and after treatment

Coal samples Activation energy(kJsdotmolminus1)Raw coal Coal-K Coal-Na Coal-Zn Coal-BDP Coal-APP Coal-TCEP

ZT 746 764 773 757 981 814 1146BLT 761 832 783 805 821 906 1152XQ 1198 1301 1247 1265 1319 1426 1789

of CO caused by the combustion of coal samples apparentlyvaried For the XQ coking coal before the treatment 259 ppmof CO was generated in the oxidation process at 100∘CHowever after the treatment the concentration of CO pro-duced reduced to 156 ppm at minimum With the increasingtemperature the coal samples treated with TCEP generated493 ppm of CO at 200∘C Similar rules were also shown tothe BLT and ZT coal At 200∘C the concentrations of COreleased by the BLT coal before and after the treatment were10994 ppm and 1345 ppm separately while those emitted bythe ZT coal were 15732 ppm at maximum and 2240 ppm atminimumThe inhibiting efficiency is expressed as shown inthe following formula

119864 = Cr minus CtCrtimes 100 (2)

where 119864 is the inhibiting rate of the inhibitor to the coalsample Cr denotes the amount of CO released from theraw coal in the experiment with the unit of 10minus6 Ct showsthe amount of CO released from the coal treated with theinhibitor under the same condition with the unit of 10minus6

According to the results calculated using formula (2) themaximal inhibiting rates of the phosphorous flame retardantsto the ZT BLT and XQ coal were shown to be 535 529and 396 at 100∘C respectively While these values changedto 857 871 and 864 at 200∘C separatelyThis revealedthat compared with the combustion at a temperature lowerthan 100∘C the phosphorous flame retardants show moreobvious inhibition effects on the CSC at a high temperatureBesides comparing with the CO production the CO

2and

C2H4emission show the similar performance after the

treatment of PFRs (Figures 6 and 7) For example the ZT coaltreated by TCEP has only 5527 ppm CO

2emission at 200∘C

while the raw coal peaks at 39343 ppm At 200∘C the C2H4

yield of BLT coal climbs to 432 ppm but the coal treated byammonium phosphate (APP) only reaches 141 ppm

34 Flame-Retardant Mechanism With the application ofPFRs phosphorus compounds were decomposed in thecombustion process of polymers with P-containing flameretardants owing to the effect of heat accompanying with thefollowing changes [20]

P-containing compoundsheating997888997888997888997888997888rarr

phosphoric acidheating997888997888997888997888997888rarr metaphosphoric acid

heating997888997888997888997888997888rarrpolymetaphosphate

(3)

Polymetaphosphate as a nonvolatile stable compound coverson the surface of the polymer thus forming a charring layerSince no flaming evaporative combustion or decomposi-tion combustion would happen to simple substance carbonpolymetaphosphate can inhibit the combustion In additionsince phosphoric acid and polymetaphosphate show strongdehydration properties carbonized films were formed on thesurface of the polymer thus inhibiting the combustion Thisis the flame-retardant mechanism of PFRs in the condensedphase of polymers PFRs are also a kind of radical scavengersThe mass-spectrometric technique revealed that PO wasgenerated in any P-containing compounds in the combustionof polymers It can combine with the hydrogen atoms in theflaming area thus restraining the flaming [21] The specificaction is expressed as

POlowast +Hlowast 997888rarr HPOlowast (4)

HPOlowast +Hlowast 997888rarr H2+ POlowast (5)

The phosphorus could inhibit the self-ignition of coal effi-ciently Superabundant phosphorus in coal also work againstthe clean and efficient utilization of coal When the coal wasadopted as boiler fuel P-containing compounds in coal willdecompose at high temperature and then form sedimentswhich are difficult to clear on the heating surface of boilerMoreover during the iron-making and steel-making processthe existence of phosphorus elementwill influence the qualityof iron and steel As the results the content of phosphorus incoal is strictly limited around the world Considering safetyfactors phosphorus flame retardants could be widely appliedin the abandoned area of colliery such as gob goaf and coalwaste heap However we still need comprehensively assess-ment before being utilized in storage and transportation ofcoal

4 Conclusions

It is essential to use effective flame retardants for the pre-vention of CSC so as to further guarantee the mine safetyAlthough PFRs have played a significant role in the industrialproduction of polymers more exploration is still neededin its role in the inhibition of CSC Laboratorial researchwas attempted to explore the inhibition mechanism of PFRson the organic functional groups in coal molecules Theexperimental results revealed that phosphorus could effec-tually inhibit CSC at a high temperature interval Althoughcertain effects could also be emerged at a low temperaturerange they were less obvious compared with that at a hightemperature with a maximal inhibiting rate above 80

8 Journal of Spectroscopy

0

5000

10000

15000

20000

25000

30000

35000

40000

45000

CO2

emiss

ion

(ppm

)

Untreated ZTZT-KZT-NaZT-Zn

Zn-APPZT-BDPZT-TCEP

40 60 80 100 120 140 160 180 200 220

Temperature (∘C)

(a) ZT coalCO

2em

issio

n (p

pm)

40 60 80 100 120 140 160 180 200 220

28000

24000

20000

16000

12000

8000

4000

0

Untreated BLTBLT-KBLT-NaBLT-Zn

BLT-APPBLT-BDPBLT-TCEP

Temperature (∘C)

(b) BLT coal

CO2

emiss

ion

(ppm

)

40 60 80 100 120 140 160 180 200 220

0

2000

4000

6000

8000

Untreated XQXQ-KXQ-NaXQ-Zn

XQ-APPXQ-BDPXQ-TCEP

Temperature (∘C)

(c) XQ coal

Figure 6 The CO2emission of coal samples before and after treatment

The results obtained using the FTIR indicated that for thecoal samples with different coal ranks the C-O structuresin the coal after the treatment were obviously weakenedSimilar results were also obtained in the thermal analysis andtemperature programming experiment using P-containingcompounds can reduce the heat released in the combustion ofcoal and increase the difficulty in the reaction between coaland oxygen This research provides a favorable reference tothe application of P-containing inhibitors

Competing Interests

The author declares that they have no competing interests

Acknowledgments

This study is funded by the Project of China National NaturalScience Foundation (no 51604185) Open Projects of StateKey Laboratory of Coal Resources and Safe Mining CUMT

Journal of Spectroscopy 9C 2

H4

emiss

ion

(ppm

)

1000

800

600

400

200

0

Untreated ZTZT-KZT-NaZT-Zn

Zn-APPZT-BDPZT-TCEP

40 60 80 100 120 140 160 180 200 220

Temperature (∘C)

(a) ZT coal

40 60 80 100 120 140 160 180 200 220

minus100

0

100

200

300

400

500

C 2H

4em

issio

n (p

pm)

Untreated BLTBLT-KBLT-NaBLT-Zn

BLT-APPBLT-BDPBLT-TCEP

Temperature (∘C)

(b) BLT coal

40 60 80 100 120 140 160 180 200 220

minus50

0

50

100

150

200

250

C 2H

4em

issio

n (p

pm)

Untreated XQXQ-KXQ-NaXQ-Zn

XQ-APPXQ-BDPXQ-TCEP

Temperature (∘C)

(c) XQ coal

Figure 7 The C2H4emission of coal samples before and after treatment

(SKLCRSM15KF07) and the Research Project Supported byShanxi Scholarship Council of China (2015-037)

References

[1] J Zhang W Choi T Ito K Takahashi and M Fujita ldquoMod-elling and parametric investigations on spontaneous heating incoal pilerdquo Fuel vol 176 pp 181ndash189 2016

[2] C Avila T Wu and E Lester ldquoPetrographic characterizationof coals as a tool to detect spontaneous combustion potentialrdquoFuel vol 125 pp 173ndash182 2014

[3] Q Deng YWang andM Liu ldquoStatistic analysis and enlighten-ment on coal mine accident of China from 2001sim2013 periodsrdquoCoal Technology vol 33 no 9 pp 73ndash75 2014

[4] Y Tang and S Xue ldquoLaboratory study on the spontaneouscombustion propensity of lignite undergone heating treatmentat low temperature in inert and low-oxygen environmentsrdquoEnergy amp Fuels vol 29 no 8 pp 4683ndash4689 2015

[5] R Song ldquoGeological exploration and treatment method ofspontaneous combustion of coal seamrdquo in Coal Geology Bureauof Shanxi Province Taiyuan pp 65ndash68 2012

[6] J Liu E Wang D Song S Wang and Y Niu ldquoEffect of rockstrength on failuremode andmechanical behavior of compositesamplesrdquo Arabian Journal of Geosciences vol 8 no 7 pp 4527ndash4539 2015

[7] Y Tang ldquoSources of underground CO crushing and ambienttemperature oxidation of coalrdquo Journal of Loss Prevention in theProcess Industries vol 38 pp 50ndash57 2015

10 Journal of Spectroscopy

[8] J C Hower J M K OrsquoKeefe K R Henke et al ldquoGaseousemissions and sublimates from the Truman Shepherd coal fireFloyd County Kentucky a re-investigation following attemptedmitigation of the firerdquo International Journal of Coal Geology vol116-117 pp 63ndash74 2013

[9] G B Stracher and T P Taylor ldquoCoal fires burning out of controlaround the world thermodynamic recipe for environmentalcatastropherdquo International Journal of Coal Geology vol 59 no1-2 pp 7ndash17 2004

[10] C L Dias M L S Oliveira J C Hower S R Taffarel R MKautzmann and L F O Silva ldquoNanominerals and ultrafineparticles from coal fires from Santa Catarina South BrazilrdquoInternational Journal of Coal Geology vol 122 pp 50ndash60 2014

[11] B Taraba and Z Pavelek ldquoInvestigation of the spontaneouscombustion susceptibility of coal using the pulse flow calori-metric method 25 years of experiencerdquo Fuel vol 125 pp 101ndash105 2014

[12] Y Yang Z Li S Hou F Gu S Gao and Y Tang ldquoThe shortestperiod of coal spontaneous combustion on the basis of oxidativeheat release intensityrdquo International Journal of Mining Scienceand Technology vol 24 no 1 pp 99ndash103 2014

[13] Y Lu and B Qin ldquoMechanical properties of inorganic solidifiedfoam for mining rock fracture fillingrdquoMaterials Express vol 5no 4 pp 291ndash299 2015

[14] L Zhang B Qin B Shi Q Wu and J Wang ldquoThe fire extin-guishing performances of foamed gel in coal minerdquo NaturalHazards vol 81 no 3 pp 1957ndash1969 2016

[15] Y-B Tang Z-H Li Y I Yang D-J Ma and H-J Ji ldquoEffect ofinorganic chloride on spontaneous combustion of coalrdquo Journalof the Southern African Institute of Mining and Metallurgy vol115 no 2 pp 87ndash92 2015

[16] D K Wang H He and P Yu ldquoFlame-retardant and thermaldegradation mechanism of low-density polyethylene modifiedwith aluminum hypophosphite and microencapsulated redphosphorusrdquo Journal of Applied Polymer Science vol 133 no 13Article ID 43225 2016

[17] Q Luo Y Yuan C Dong S Liu and J Zhao ldquoHighperformance fire-retarded epoxy imparted by a novelphenophosphazine-containing antiflaming compound atultra-low loadingrdquoMaterials Letters vol 169 pp 103ndash106 2016

[18] Y Tang ldquoAnalysis of coals with different spontaneous com-bustion characteristics using infrared spectrometryrdquo Journal ofApplied Spectroscopy vol 82 no 2 pp 316ndash321 2015

[19] Y Tang ldquoA laboratorial study of spontaneous combustioncharacteristics of the oil shale in Fushun Chinardquo CombustionScience and Technology vol 188 no 6 pp 997ndash1010 2016

[20] E D Weil and S V Levchik ldquo13-Overview of modes of actionand interaction of flame retardantsrdquo in Flame Retardants pp323ndash338 Hanser 2nd edition 2016

[21] Y Tang ldquoInhibition of low-temperature oxidation of bitumi-nous coal using a novel phase-transition aerosolrdquo Energy ampFuels vol 30 no 11 pp 9303ndash9309 2016

Submit your manuscripts athttpswwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Inorganic ChemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

International Journal ofPhotoenergy

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Carbohydrate Chemistry

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

Physical Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom

Analytical Methods in Chemistry

Journal of

Volume 2014

Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

SpectroscopyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Medicinal ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chromatography Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Applied ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Theoretical ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Spectroscopy

Analytical ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Quantum Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Organic Chemistry International

ElectrochemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CatalystsJournal of

4 Journal of Spectroscopy

200 400 600 800

Temperature (∘C)

0

20

40

60

80

100

Mas

s (

)

Coal-DBP

Coal-TCEPCoal-APPCoal-K

Coal-NaCoal-Zn

Raw coal

T1

T2

T3

(a) ZT coal

200 400 600 800

Temperature (∘C)

Coal-BDP

Coal-TCEPCoal-APPCoal-K

Coal-NaCoal-Zn

Raw coal

0

20

40

60

80

100

Mas

s (

)

T1

T2

T3

(b) BLT coal

200 400 600 800

Temperature

0

20

40

60

80

100

Mas

s (

)

Coal-BDP

Coal-TCEPCoal-APPCoal-K

Coal-NaCoal-Zn

Raw coal

T1

T2

T3

(c) XQ coal

Figure 3 The TG curves of coal samples before and after treatment

weaken the active structures including oxygen-containingfunctional groups in coal thus affecting the low temperatureoxidation of coal

32 Thermal Analysis Based on the thermal analysis it wasfound that after the treatment using P-containing additivesthe thermogravimetric curves of the coal samples varied indifferent degrees According to Figure 3 the combustionof coal can be divided into three stages precombustioncombustion and stabilization Before 200∘C all three coalsamples show similar trend in TG and DSC curves The P-containing inhibitors play a significant role on the control-ling of low temperature oxidation And this phenomenon

remains with the temperature increasing For the ZT browncoal raw coal was gradually oxidized with the increasingtemperature before 200∘C while it was rapidly combustedand decomposed when the temperature varied from 250∘C to300∘C After the temperature reached 600∘C the combustionbasically stopped and the mass of the coal maintained stableAfter the addition of the P-containing inhibitors the coalwas slowly burned and it can be found that both the criticaltemperature 119879

1and combustion temperature 119879

2of the coal

were obviously postponed and the mass loss rate of the coalwas also slowed down Similarly as shown in Figure 4 thedifferential scanning calorimetry (DSC) curve of the ZT coalindicated that the heat emitted by the treated coal sample

Journal of Spectroscopy 5

352∘C 401

∘C503

∘C

464∘C

DSC

(mW

mg)

015

010

005

000

minus005

minus010

200 400 600 800

Temperature (∘C)

Coal-DBP

Coal-TCEPCoal-APPCoal-K

Coal-NaCoal-Zn

Raw coal

(a) ZT coalD

SC (m

Wm

g)

200 400 600 800

Temperature (∘C)

Coal-BDP

Coal-TCEPCoal-APPCoal-K

Coal-NaCoal-Zn

Raw coal

505∘C

551∘C

686∘C

14

12

10

8

6

4

2

0

minus2

minus4

(b) BLT coal

200 400 600 800

Temperature

Coal-BDP

Coal-TCEPCoal-APPCoal-K

Coal-NaCoal-Zn

Raw coal

DSC

(mW

mg)

14

12

10

8

6

4

2

0

minus2

minus4

735∘C

669∘C 680

∘C

(c) XQ coal

Figure 4 The DSC curves of coal samples before and after treatment

was also changed not only the heat released reduced butalso the temperature at which the greatest exothermic peakdelayed occurred In contrast the BLT and XQ coal alsoshowed similar rules that is the heat released by the coalafter the treatment was significantly lowered For examplethe exothermic peak of ZT raw coal in DSC curve is 352∘CAfter the treatment by BDP this temperature postpones to503∘C The masses of these two kinds of coal samples wereslightly changed owing to the addition of P-containing flameretardants before 200∘C Between 200 to 400∘C this tendencyhas been further strengthened At 300∘C the heat flux of XQraw coal is 1486mWmg while the date of coal treated byTCEP is only 0263mWmg However after the temperature

reaches 400∘C the coal samples were burned and thereforeremarkable difference was shown to the mass loss rates of thecoal samples before and after the treatment

This suggested that PFRs can be used to effectively controlthe combustion of coal

The oxygenolysis of coal was a typical gas-solid reactionAssuming that reaction order of coal was 1 according tochemical reaction kinetics the activation energy of thecoal was calculated by adopting the Coats-Redfern integralformula [19]

ln [119892 (119886)1198792 ] = ln [119860119877120573119864119886

(1 minus 2119877119879119864119886

)] minus 119864119877119879 (1)

6 Journal of Spectroscopy

Untreated ZTZT-KZT-NaZT-Zn

Zn-APPZT-BDPZT-TCEP

40 60 80 100 120 140 160 180 200 220

0

2000

4000

6000

8000

10000

12000

14000

16000

CO em

issio

n (p

pm)

Temperature (∘C)

(a) ZT coal

40 60 80 100 120 140 160 180 200 220

Untreated BLTBLT-KBLT-NaBLT-Zn

BLT-APPBLT-BDPBLT-TCEP

0

2000

4000

6000

8000

10000

12000

14000

CO em

issio

n (p

pm)

Temperature (∘C)

(b) BLT coal

40 60 80 100 120 140 160 180 200 220

Untreated XQXQ-KXQ-NaXQ-Zn

XQ-APPXQ-BDPXQ-TCEP

0

2000

4000

CO em

issio

n (p

pm)

Temperature (∘C)

(c) XQ coal

Figure 5 The CO emission of coal samples before and after treatment

where 119886 represented transformation percentage of coal inoxygenolysis process 120573 represented heating rate and 119892(119886)was integral formula of function model which reflectedmechanism of oxidation reaction of coal 119892(119886) = minus ln(1 minus119886) Meanwhile 119905 was reaction time 119879 was reaction tem-perature 119860 was preexponential factor 119864

119886was activation

energy induced by oxygenolysis of coal and 119877 representedgas constant Based on mechanism of the chemical reactionkinetics the construction on 119897119879 was performed by utilizingln(minus ln(1 minus 119886)1198792) Besides according to the obtained slopeactivation energy 119864

119886of the reaction was expected to be

calculated According to Table 3 the activation energy of thecoal samples after the treatment was improved to differentdegrees when the temperature varied from 50∘C to 150∘C

in comparison with those before the treatment After thetreatment using inorganic phosphorus agents the coal dealtwith zinc phosphate showed a significant change to theactivation energy In contrast the optimal effects were foundto the coal treated with the organic phosphorus agent tris(2-chloroethyl) phosphate (TCEP) The improvement of theactivation energy indicated that the higher the energy neededfor the low temperature oxidation of coal is themore difficultthe reaction happens

33 Oxidation Products As seen in Figure 5 as an index gasof CSC the CO released in the oxidation of coal samplespresented increased concentrations with the temperatureHowever after the treatment using PFRs the concentrations

Journal of Spectroscopy 7

Table 3 Activation energy of the coal samples before and after treatment

Coal samples Activation energy(kJsdotmolminus1)Raw coal Coal-K Coal-Na Coal-Zn Coal-BDP Coal-APP Coal-TCEP

ZT 746 764 773 757 981 814 1146BLT 761 832 783 805 821 906 1152XQ 1198 1301 1247 1265 1319 1426 1789

of CO caused by the combustion of coal samples apparentlyvaried For the XQ coking coal before the treatment 259 ppmof CO was generated in the oxidation process at 100∘CHowever after the treatment the concentration of CO pro-duced reduced to 156 ppm at minimum With the increasingtemperature the coal samples treated with TCEP generated493 ppm of CO at 200∘C Similar rules were also shown tothe BLT and ZT coal At 200∘C the concentrations of COreleased by the BLT coal before and after the treatment were10994 ppm and 1345 ppm separately while those emitted bythe ZT coal were 15732 ppm at maximum and 2240 ppm atminimumThe inhibiting efficiency is expressed as shown inthe following formula

119864 = Cr minus CtCrtimes 100 (2)

where 119864 is the inhibiting rate of the inhibitor to the coalsample Cr denotes the amount of CO released from theraw coal in the experiment with the unit of 10minus6 Ct showsthe amount of CO released from the coal treated with theinhibitor under the same condition with the unit of 10minus6

According to the results calculated using formula (2) themaximal inhibiting rates of the phosphorous flame retardantsto the ZT BLT and XQ coal were shown to be 535 529and 396 at 100∘C respectively While these values changedto 857 871 and 864 at 200∘C separatelyThis revealedthat compared with the combustion at a temperature lowerthan 100∘C the phosphorous flame retardants show moreobvious inhibition effects on the CSC at a high temperatureBesides comparing with the CO production the CO

2and

C2H4emission show the similar performance after the

treatment of PFRs (Figures 6 and 7) For example the ZT coaltreated by TCEP has only 5527 ppm CO

2emission at 200∘C

while the raw coal peaks at 39343 ppm At 200∘C the C2H4

yield of BLT coal climbs to 432 ppm but the coal treated byammonium phosphate (APP) only reaches 141 ppm

34 Flame-Retardant Mechanism With the application ofPFRs phosphorus compounds were decomposed in thecombustion process of polymers with P-containing flameretardants owing to the effect of heat accompanying with thefollowing changes [20]

P-containing compoundsheating997888997888997888997888997888rarr

phosphoric acidheating997888997888997888997888997888rarr metaphosphoric acid

heating997888997888997888997888997888rarrpolymetaphosphate

(3)

Polymetaphosphate as a nonvolatile stable compound coverson the surface of the polymer thus forming a charring layerSince no flaming evaporative combustion or decomposi-tion combustion would happen to simple substance carbonpolymetaphosphate can inhibit the combustion In additionsince phosphoric acid and polymetaphosphate show strongdehydration properties carbonized films were formed on thesurface of the polymer thus inhibiting the combustion Thisis the flame-retardant mechanism of PFRs in the condensedphase of polymers PFRs are also a kind of radical scavengersThe mass-spectrometric technique revealed that PO wasgenerated in any P-containing compounds in the combustionof polymers It can combine with the hydrogen atoms in theflaming area thus restraining the flaming [21] The specificaction is expressed as

POlowast +Hlowast 997888rarr HPOlowast (4)

HPOlowast +Hlowast 997888rarr H2+ POlowast (5)

The phosphorus could inhibit the self-ignition of coal effi-ciently Superabundant phosphorus in coal also work againstthe clean and efficient utilization of coal When the coal wasadopted as boiler fuel P-containing compounds in coal willdecompose at high temperature and then form sedimentswhich are difficult to clear on the heating surface of boilerMoreover during the iron-making and steel-making processthe existence of phosphorus elementwill influence the qualityof iron and steel As the results the content of phosphorus incoal is strictly limited around the world Considering safetyfactors phosphorus flame retardants could be widely appliedin the abandoned area of colliery such as gob goaf and coalwaste heap However we still need comprehensively assess-ment before being utilized in storage and transportation ofcoal

4 Conclusions

It is essential to use effective flame retardants for the pre-vention of CSC so as to further guarantee the mine safetyAlthough PFRs have played a significant role in the industrialproduction of polymers more exploration is still neededin its role in the inhibition of CSC Laboratorial researchwas attempted to explore the inhibition mechanism of PFRson the organic functional groups in coal molecules Theexperimental results revealed that phosphorus could effec-tually inhibit CSC at a high temperature interval Althoughcertain effects could also be emerged at a low temperaturerange they were less obvious compared with that at a hightemperature with a maximal inhibiting rate above 80

8 Journal of Spectroscopy

0

5000

10000

15000

20000

25000

30000

35000

40000

45000

CO2

emiss

ion

(ppm

)

Untreated ZTZT-KZT-NaZT-Zn

Zn-APPZT-BDPZT-TCEP

40 60 80 100 120 140 160 180 200 220

Temperature (∘C)

(a) ZT coalCO

2em

issio

n (p

pm)

40 60 80 100 120 140 160 180 200 220

28000

24000

20000

16000

12000

8000

4000

0

Untreated BLTBLT-KBLT-NaBLT-Zn

BLT-APPBLT-BDPBLT-TCEP

Temperature (∘C)

(b) BLT coal

CO2

emiss

ion

(ppm

)

40 60 80 100 120 140 160 180 200 220

0

2000

4000

6000

8000

Untreated XQXQ-KXQ-NaXQ-Zn

XQ-APPXQ-BDPXQ-TCEP

Temperature (∘C)

(c) XQ coal

Figure 6 The CO2emission of coal samples before and after treatment

The results obtained using the FTIR indicated that for thecoal samples with different coal ranks the C-O structuresin the coal after the treatment were obviously weakenedSimilar results were also obtained in the thermal analysis andtemperature programming experiment using P-containingcompounds can reduce the heat released in the combustion ofcoal and increase the difficulty in the reaction between coaland oxygen This research provides a favorable reference tothe application of P-containing inhibitors

Competing Interests

The author declares that they have no competing interests

Acknowledgments

This study is funded by the Project of China National NaturalScience Foundation (no 51604185) Open Projects of StateKey Laboratory of Coal Resources and Safe Mining CUMT

Journal of Spectroscopy 9C 2

H4

emiss

ion

(ppm

)

1000

800

600

400

200

0

Untreated ZTZT-KZT-NaZT-Zn

Zn-APPZT-BDPZT-TCEP

40 60 80 100 120 140 160 180 200 220

Temperature (∘C)

(a) ZT coal

40 60 80 100 120 140 160 180 200 220

minus100

0

100

200

300

400

500

C 2H

4em

issio

n (p

pm)

Untreated BLTBLT-KBLT-NaBLT-Zn

BLT-APPBLT-BDPBLT-TCEP

Temperature (∘C)

(b) BLT coal

40 60 80 100 120 140 160 180 200 220

minus50

0

50

100

150

200

250

C 2H

4em

issio

n (p

pm)

Untreated XQXQ-KXQ-NaXQ-Zn

XQ-APPXQ-BDPXQ-TCEP

Temperature (∘C)

(c) XQ coal

Figure 7 The C2H4emission of coal samples before and after treatment

(SKLCRSM15KF07) and the Research Project Supported byShanxi Scholarship Council of China (2015-037)

References

[1] J Zhang W Choi T Ito K Takahashi and M Fujita ldquoMod-elling and parametric investigations on spontaneous heating incoal pilerdquo Fuel vol 176 pp 181ndash189 2016

[2] C Avila T Wu and E Lester ldquoPetrographic characterizationof coals as a tool to detect spontaneous combustion potentialrdquoFuel vol 125 pp 173ndash182 2014

[3] Q Deng YWang andM Liu ldquoStatistic analysis and enlighten-ment on coal mine accident of China from 2001sim2013 periodsrdquoCoal Technology vol 33 no 9 pp 73ndash75 2014

[4] Y Tang and S Xue ldquoLaboratory study on the spontaneouscombustion propensity of lignite undergone heating treatmentat low temperature in inert and low-oxygen environmentsrdquoEnergy amp Fuels vol 29 no 8 pp 4683ndash4689 2015

[5] R Song ldquoGeological exploration and treatment method ofspontaneous combustion of coal seamrdquo in Coal Geology Bureauof Shanxi Province Taiyuan pp 65ndash68 2012

[6] J Liu E Wang D Song S Wang and Y Niu ldquoEffect of rockstrength on failuremode andmechanical behavior of compositesamplesrdquo Arabian Journal of Geosciences vol 8 no 7 pp 4527ndash4539 2015

[7] Y Tang ldquoSources of underground CO crushing and ambienttemperature oxidation of coalrdquo Journal of Loss Prevention in theProcess Industries vol 38 pp 50ndash57 2015

10 Journal of Spectroscopy

[8] J C Hower J M K OrsquoKeefe K R Henke et al ldquoGaseousemissions and sublimates from the Truman Shepherd coal fireFloyd County Kentucky a re-investigation following attemptedmitigation of the firerdquo International Journal of Coal Geology vol116-117 pp 63ndash74 2013

[9] G B Stracher and T P Taylor ldquoCoal fires burning out of controlaround the world thermodynamic recipe for environmentalcatastropherdquo International Journal of Coal Geology vol 59 no1-2 pp 7ndash17 2004

[10] C L Dias M L S Oliveira J C Hower S R Taffarel R MKautzmann and L F O Silva ldquoNanominerals and ultrafineparticles from coal fires from Santa Catarina South BrazilrdquoInternational Journal of Coal Geology vol 122 pp 50ndash60 2014

[11] B Taraba and Z Pavelek ldquoInvestigation of the spontaneouscombustion susceptibility of coal using the pulse flow calori-metric method 25 years of experiencerdquo Fuel vol 125 pp 101ndash105 2014

[12] Y Yang Z Li S Hou F Gu S Gao and Y Tang ldquoThe shortestperiod of coal spontaneous combustion on the basis of oxidativeheat release intensityrdquo International Journal of Mining Scienceand Technology vol 24 no 1 pp 99ndash103 2014

[13] Y Lu and B Qin ldquoMechanical properties of inorganic solidifiedfoam for mining rock fracture fillingrdquoMaterials Express vol 5no 4 pp 291ndash299 2015

[14] L Zhang B Qin B Shi Q Wu and J Wang ldquoThe fire extin-guishing performances of foamed gel in coal minerdquo NaturalHazards vol 81 no 3 pp 1957ndash1969 2016

[15] Y-B Tang Z-H Li Y I Yang D-J Ma and H-J Ji ldquoEffect ofinorganic chloride on spontaneous combustion of coalrdquo Journalof the Southern African Institute of Mining and Metallurgy vol115 no 2 pp 87ndash92 2015

[16] D K Wang H He and P Yu ldquoFlame-retardant and thermaldegradation mechanism of low-density polyethylene modifiedwith aluminum hypophosphite and microencapsulated redphosphorusrdquo Journal of Applied Polymer Science vol 133 no 13Article ID 43225 2016

[17] Q Luo Y Yuan C Dong S Liu and J Zhao ldquoHighperformance fire-retarded epoxy imparted by a novelphenophosphazine-containing antiflaming compound atultra-low loadingrdquoMaterials Letters vol 169 pp 103ndash106 2016

[18] Y Tang ldquoAnalysis of coals with different spontaneous com-bustion characteristics using infrared spectrometryrdquo Journal ofApplied Spectroscopy vol 82 no 2 pp 316ndash321 2015

[19] Y Tang ldquoA laboratorial study of spontaneous combustioncharacteristics of the oil shale in Fushun Chinardquo CombustionScience and Technology vol 188 no 6 pp 997ndash1010 2016

[20] E D Weil and S V Levchik ldquo13-Overview of modes of actionand interaction of flame retardantsrdquo in Flame Retardants pp323ndash338 Hanser 2nd edition 2016

[21] Y Tang ldquoInhibition of low-temperature oxidation of bitumi-nous coal using a novel phase-transition aerosolrdquo Energy ampFuels vol 30 no 11 pp 9303ndash9309 2016

Submit your manuscripts athttpswwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Inorganic ChemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

International Journal ofPhotoenergy

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Carbohydrate Chemistry

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

Physical Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom

Analytical Methods in Chemistry

Journal of

Volume 2014

Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

SpectroscopyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Medicinal ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chromatography Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Applied ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Theoretical ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Spectroscopy

Analytical ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Quantum Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Organic Chemistry International

ElectrochemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CatalystsJournal of

Journal of Spectroscopy 5

352∘C 401

∘C503

∘C

464∘C

DSC

(mW

mg)

015

010

005

000

minus005

minus010

200 400 600 800

Temperature (∘C)

Coal-DBP

Coal-TCEPCoal-APPCoal-K

Coal-NaCoal-Zn

Raw coal

(a) ZT coalD

SC (m

Wm

g)

200 400 600 800

Temperature (∘C)

Coal-BDP

Coal-TCEPCoal-APPCoal-K

Coal-NaCoal-Zn

Raw coal

505∘C

551∘C

686∘C

14

12

10

8

6

4

2

0

minus2

minus4

(b) BLT coal

200 400 600 800

Temperature

Coal-BDP

Coal-TCEPCoal-APPCoal-K

Coal-NaCoal-Zn

Raw coal

DSC

(mW

mg)

14

12

10

8

6

4

2

0

minus2

minus4

735∘C

669∘C 680

∘C

(c) XQ coal

Figure 4 The DSC curves of coal samples before and after treatment

was also changed not only the heat released reduced butalso the temperature at which the greatest exothermic peakdelayed occurred In contrast the BLT and XQ coal alsoshowed similar rules that is the heat released by the coalafter the treatment was significantly lowered For examplethe exothermic peak of ZT raw coal in DSC curve is 352∘CAfter the treatment by BDP this temperature postpones to503∘C The masses of these two kinds of coal samples wereslightly changed owing to the addition of P-containing flameretardants before 200∘C Between 200 to 400∘C this tendencyhas been further strengthened At 300∘C the heat flux of XQraw coal is 1486mWmg while the date of coal treated byTCEP is only 0263mWmg However after the temperature

reaches 400∘C the coal samples were burned and thereforeremarkable difference was shown to the mass loss rates of thecoal samples before and after the treatment

This suggested that PFRs can be used to effectively controlthe combustion of coal

The oxygenolysis of coal was a typical gas-solid reactionAssuming that reaction order of coal was 1 according tochemical reaction kinetics the activation energy of thecoal was calculated by adopting the Coats-Redfern integralformula [19]

ln [119892 (119886)1198792 ] = ln [119860119877120573119864119886

(1 minus 2119877119879119864119886

)] minus 119864119877119879 (1)

6 Journal of Spectroscopy

Untreated ZTZT-KZT-NaZT-Zn

Zn-APPZT-BDPZT-TCEP

40 60 80 100 120 140 160 180 200 220

0

2000

4000

6000

8000

10000

12000

14000

16000

CO em

issio

n (p

pm)

Temperature (∘C)

(a) ZT coal

40 60 80 100 120 140 160 180 200 220

Untreated BLTBLT-KBLT-NaBLT-Zn

BLT-APPBLT-BDPBLT-TCEP

0

2000

4000

6000

8000

10000

12000

14000

CO em

issio

n (p

pm)

Temperature (∘C)

(b) BLT coal

40 60 80 100 120 140 160 180 200 220

Untreated XQXQ-KXQ-NaXQ-Zn

XQ-APPXQ-BDPXQ-TCEP

0

2000

4000

CO em

issio

n (p

pm)

Temperature (∘C)

(c) XQ coal

Figure 5 The CO emission of coal samples before and after treatment

where 119886 represented transformation percentage of coal inoxygenolysis process 120573 represented heating rate and 119892(119886)was integral formula of function model which reflectedmechanism of oxidation reaction of coal 119892(119886) = minus ln(1 minus119886) Meanwhile 119905 was reaction time 119879 was reaction tem-perature 119860 was preexponential factor 119864

119886was activation

energy induced by oxygenolysis of coal and 119877 representedgas constant Based on mechanism of the chemical reactionkinetics the construction on 119897119879 was performed by utilizingln(minus ln(1 minus 119886)1198792) Besides according to the obtained slopeactivation energy 119864

119886of the reaction was expected to be

calculated According to Table 3 the activation energy of thecoal samples after the treatment was improved to differentdegrees when the temperature varied from 50∘C to 150∘C

in comparison with those before the treatment After thetreatment using inorganic phosphorus agents the coal dealtwith zinc phosphate showed a significant change to theactivation energy In contrast the optimal effects were foundto the coal treated with the organic phosphorus agent tris(2-chloroethyl) phosphate (TCEP) The improvement of theactivation energy indicated that the higher the energy neededfor the low temperature oxidation of coal is themore difficultthe reaction happens

33 Oxidation Products As seen in Figure 5 as an index gasof CSC the CO released in the oxidation of coal samplespresented increased concentrations with the temperatureHowever after the treatment using PFRs the concentrations

Journal of Spectroscopy 7

Table 3 Activation energy of the coal samples before and after treatment

Coal samples Activation energy(kJsdotmolminus1)Raw coal Coal-K Coal-Na Coal-Zn Coal-BDP Coal-APP Coal-TCEP

ZT 746 764 773 757 981 814 1146BLT 761 832 783 805 821 906 1152XQ 1198 1301 1247 1265 1319 1426 1789

of CO caused by the combustion of coal samples apparentlyvaried For the XQ coking coal before the treatment 259 ppmof CO was generated in the oxidation process at 100∘CHowever after the treatment the concentration of CO pro-duced reduced to 156 ppm at minimum With the increasingtemperature the coal samples treated with TCEP generated493 ppm of CO at 200∘C Similar rules were also shown tothe BLT and ZT coal At 200∘C the concentrations of COreleased by the BLT coal before and after the treatment were10994 ppm and 1345 ppm separately while those emitted bythe ZT coal were 15732 ppm at maximum and 2240 ppm atminimumThe inhibiting efficiency is expressed as shown inthe following formula

119864 = Cr minus CtCrtimes 100 (2)

where 119864 is the inhibiting rate of the inhibitor to the coalsample Cr denotes the amount of CO released from theraw coal in the experiment with the unit of 10minus6 Ct showsthe amount of CO released from the coal treated with theinhibitor under the same condition with the unit of 10minus6

According to the results calculated using formula (2) themaximal inhibiting rates of the phosphorous flame retardantsto the ZT BLT and XQ coal were shown to be 535 529and 396 at 100∘C respectively While these values changedto 857 871 and 864 at 200∘C separatelyThis revealedthat compared with the combustion at a temperature lowerthan 100∘C the phosphorous flame retardants show moreobvious inhibition effects on the CSC at a high temperatureBesides comparing with the CO production the CO

2and

C2H4emission show the similar performance after the

treatment of PFRs (Figures 6 and 7) For example the ZT coaltreated by TCEP has only 5527 ppm CO

2emission at 200∘C

while the raw coal peaks at 39343 ppm At 200∘C the C2H4

yield of BLT coal climbs to 432 ppm but the coal treated byammonium phosphate (APP) only reaches 141 ppm

34 Flame-Retardant Mechanism With the application ofPFRs phosphorus compounds were decomposed in thecombustion process of polymers with P-containing flameretardants owing to the effect of heat accompanying with thefollowing changes [20]

P-containing compoundsheating997888997888997888997888997888rarr

phosphoric acidheating997888997888997888997888997888rarr metaphosphoric acid

heating997888997888997888997888997888rarrpolymetaphosphate

(3)

Polymetaphosphate as a nonvolatile stable compound coverson the surface of the polymer thus forming a charring layerSince no flaming evaporative combustion or decomposi-tion combustion would happen to simple substance carbonpolymetaphosphate can inhibit the combustion In additionsince phosphoric acid and polymetaphosphate show strongdehydration properties carbonized films were formed on thesurface of the polymer thus inhibiting the combustion Thisis the flame-retardant mechanism of PFRs in the condensedphase of polymers PFRs are also a kind of radical scavengersThe mass-spectrometric technique revealed that PO wasgenerated in any P-containing compounds in the combustionof polymers It can combine with the hydrogen atoms in theflaming area thus restraining the flaming [21] The specificaction is expressed as

POlowast +Hlowast 997888rarr HPOlowast (4)

HPOlowast +Hlowast 997888rarr H2+ POlowast (5)

The phosphorus could inhibit the self-ignition of coal effi-ciently Superabundant phosphorus in coal also work againstthe clean and efficient utilization of coal When the coal wasadopted as boiler fuel P-containing compounds in coal willdecompose at high temperature and then form sedimentswhich are difficult to clear on the heating surface of boilerMoreover during the iron-making and steel-making processthe existence of phosphorus elementwill influence the qualityof iron and steel As the results the content of phosphorus incoal is strictly limited around the world Considering safetyfactors phosphorus flame retardants could be widely appliedin the abandoned area of colliery such as gob goaf and coalwaste heap However we still need comprehensively assess-ment before being utilized in storage and transportation ofcoal

4 Conclusions

It is essential to use effective flame retardants for the pre-vention of CSC so as to further guarantee the mine safetyAlthough PFRs have played a significant role in the industrialproduction of polymers more exploration is still neededin its role in the inhibition of CSC Laboratorial researchwas attempted to explore the inhibition mechanism of PFRson the organic functional groups in coal molecules Theexperimental results revealed that phosphorus could effec-tually inhibit CSC at a high temperature interval Althoughcertain effects could also be emerged at a low temperaturerange they were less obvious compared with that at a hightemperature with a maximal inhibiting rate above 80

8 Journal of Spectroscopy

0

5000

10000

15000

20000

25000

30000

35000

40000

45000

CO2

emiss

ion

(ppm

)

Untreated ZTZT-KZT-NaZT-Zn

Zn-APPZT-BDPZT-TCEP

40 60 80 100 120 140 160 180 200 220

Temperature (∘C)

(a) ZT coalCO

2em

issio

n (p

pm)

40 60 80 100 120 140 160 180 200 220

28000

24000

20000

16000

12000

8000

4000

0

Untreated BLTBLT-KBLT-NaBLT-Zn

BLT-APPBLT-BDPBLT-TCEP

Temperature (∘C)

(b) BLT coal

CO2

emiss

ion

(ppm

)

40 60 80 100 120 140 160 180 200 220

0

2000

4000

6000

8000

Untreated XQXQ-KXQ-NaXQ-Zn

XQ-APPXQ-BDPXQ-TCEP

Temperature (∘C)

(c) XQ coal

Figure 6 The CO2emission of coal samples before and after treatment

The results obtained using the FTIR indicated that for thecoal samples with different coal ranks the C-O structuresin the coal after the treatment were obviously weakenedSimilar results were also obtained in the thermal analysis andtemperature programming experiment using P-containingcompounds can reduce the heat released in the combustion ofcoal and increase the difficulty in the reaction between coaland oxygen This research provides a favorable reference tothe application of P-containing inhibitors

Competing Interests

The author declares that they have no competing interests

Acknowledgments

This study is funded by the Project of China National NaturalScience Foundation (no 51604185) Open Projects of StateKey Laboratory of Coal Resources and Safe Mining CUMT

Journal of Spectroscopy 9C 2

H4

emiss

ion

(ppm

)

1000

800

600

400

200

0

Untreated ZTZT-KZT-NaZT-Zn

Zn-APPZT-BDPZT-TCEP

40 60 80 100 120 140 160 180 200 220

Temperature (∘C)

(a) ZT coal

40 60 80 100 120 140 160 180 200 220

minus100

0

100

200

300

400

500

C 2H

4em

issio

n (p

pm)

Untreated BLTBLT-KBLT-NaBLT-Zn

BLT-APPBLT-BDPBLT-TCEP

Temperature (∘C)

(b) BLT coal

40 60 80 100 120 140 160 180 200 220

minus50

0

50

100

150

200

250

C 2H

4em

issio

n (p

pm)

Untreated XQXQ-KXQ-NaXQ-Zn

XQ-APPXQ-BDPXQ-TCEP

Temperature (∘C)

(c) XQ coal

Figure 7 The C2H4emission of coal samples before and after treatment

(SKLCRSM15KF07) and the Research Project Supported byShanxi Scholarship Council of China (2015-037)

References

[1] J Zhang W Choi T Ito K Takahashi and M Fujita ldquoMod-elling and parametric investigations on spontaneous heating incoal pilerdquo Fuel vol 176 pp 181ndash189 2016

[2] C Avila T Wu and E Lester ldquoPetrographic characterizationof coals as a tool to detect spontaneous combustion potentialrdquoFuel vol 125 pp 173ndash182 2014

[3] Q Deng YWang andM Liu ldquoStatistic analysis and enlighten-ment on coal mine accident of China from 2001sim2013 periodsrdquoCoal Technology vol 33 no 9 pp 73ndash75 2014

[4] Y Tang and S Xue ldquoLaboratory study on the spontaneouscombustion propensity of lignite undergone heating treatmentat low temperature in inert and low-oxygen environmentsrdquoEnergy amp Fuels vol 29 no 8 pp 4683ndash4689 2015

[5] R Song ldquoGeological exploration and treatment method ofspontaneous combustion of coal seamrdquo in Coal Geology Bureauof Shanxi Province Taiyuan pp 65ndash68 2012

[6] J Liu E Wang D Song S Wang and Y Niu ldquoEffect of rockstrength on failuremode andmechanical behavior of compositesamplesrdquo Arabian Journal of Geosciences vol 8 no 7 pp 4527ndash4539 2015

[7] Y Tang ldquoSources of underground CO crushing and ambienttemperature oxidation of coalrdquo Journal of Loss Prevention in theProcess Industries vol 38 pp 50ndash57 2015

10 Journal of Spectroscopy

[8] J C Hower J M K OrsquoKeefe K R Henke et al ldquoGaseousemissions and sublimates from the Truman Shepherd coal fireFloyd County Kentucky a re-investigation following attemptedmitigation of the firerdquo International Journal of Coal Geology vol116-117 pp 63ndash74 2013

[9] G B Stracher and T P Taylor ldquoCoal fires burning out of controlaround the world thermodynamic recipe for environmentalcatastropherdquo International Journal of Coal Geology vol 59 no1-2 pp 7ndash17 2004

[10] C L Dias M L S Oliveira J C Hower S R Taffarel R MKautzmann and L F O Silva ldquoNanominerals and ultrafineparticles from coal fires from Santa Catarina South BrazilrdquoInternational Journal of Coal Geology vol 122 pp 50ndash60 2014

[11] B Taraba and Z Pavelek ldquoInvestigation of the spontaneouscombustion susceptibility of coal using the pulse flow calori-metric method 25 years of experiencerdquo Fuel vol 125 pp 101ndash105 2014

[12] Y Yang Z Li S Hou F Gu S Gao and Y Tang ldquoThe shortestperiod of coal spontaneous combustion on the basis of oxidativeheat release intensityrdquo International Journal of Mining Scienceand Technology vol 24 no 1 pp 99ndash103 2014

[13] Y Lu and B Qin ldquoMechanical properties of inorganic solidifiedfoam for mining rock fracture fillingrdquoMaterials Express vol 5no 4 pp 291ndash299 2015

[14] L Zhang B Qin B Shi Q Wu and J Wang ldquoThe fire extin-guishing performances of foamed gel in coal minerdquo NaturalHazards vol 81 no 3 pp 1957ndash1969 2016

[15] Y-B Tang Z-H Li Y I Yang D-J Ma and H-J Ji ldquoEffect ofinorganic chloride on spontaneous combustion of coalrdquo Journalof the Southern African Institute of Mining and Metallurgy vol115 no 2 pp 87ndash92 2015

[16] D K Wang H He and P Yu ldquoFlame-retardant and thermaldegradation mechanism of low-density polyethylene modifiedwith aluminum hypophosphite and microencapsulated redphosphorusrdquo Journal of Applied Polymer Science vol 133 no 13Article ID 43225 2016

[17] Q Luo Y Yuan C Dong S Liu and J Zhao ldquoHighperformance fire-retarded epoxy imparted by a novelphenophosphazine-containing antiflaming compound atultra-low loadingrdquoMaterials Letters vol 169 pp 103ndash106 2016

[18] Y Tang ldquoAnalysis of coals with different spontaneous com-bustion characteristics using infrared spectrometryrdquo Journal ofApplied Spectroscopy vol 82 no 2 pp 316ndash321 2015

[19] Y Tang ldquoA laboratorial study of spontaneous combustioncharacteristics of the oil shale in Fushun Chinardquo CombustionScience and Technology vol 188 no 6 pp 997ndash1010 2016

[20] E D Weil and S V Levchik ldquo13-Overview of modes of actionand interaction of flame retardantsrdquo in Flame Retardants pp323ndash338 Hanser 2nd edition 2016

[21] Y Tang ldquoInhibition of low-temperature oxidation of bitumi-nous coal using a novel phase-transition aerosolrdquo Energy ampFuels vol 30 no 11 pp 9303ndash9309 2016

Submit your manuscripts athttpswwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Inorganic ChemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

International Journal ofPhotoenergy

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Carbohydrate Chemistry

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

Physical Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom

Analytical Methods in Chemistry

Journal of

Volume 2014

Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

SpectroscopyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Medicinal ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chromatography Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Applied ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Theoretical ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Spectroscopy

Analytical ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Quantum Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Organic Chemistry International

ElectrochemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CatalystsJournal of

6 Journal of Spectroscopy

Untreated ZTZT-KZT-NaZT-Zn

Zn-APPZT-BDPZT-TCEP

40 60 80 100 120 140 160 180 200 220

0

2000

4000

6000

8000

10000

12000

14000

16000

CO em

issio

n (p

pm)

Temperature (∘C)

(a) ZT coal

40 60 80 100 120 140 160 180 200 220

Untreated BLTBLT-KBLT-NaBLT-Zn

BLT-APPBLT-BDPBLT-TCEP

0

2000

4000

6000

8000

10000

12000

14000

CO em

issio

n (p

pm)

Temperature (∘C)

(b) BLT coal

40 60 80 100 120 140 160 180 200 220

Untreated XQXQ-KXQ-NaXQ-Zn

XQ-APPXQ-BDPXQ-TCEP

0

2000

4000

CO em

issio

n (p

pm)

Temperature (∘C)

(c) XQ coal

Figure 5 The CO emission of coal samples before and after treatment

where 119886 represented transformation percentage of coal inoxygenolysis process 120573 represented heating rate and 119892(119886)was integral formula of function model which reflectedmechanism of oxidation reaction of coal 119892(119886) = minus ln(1 minus119886) Meanwhile 119905 was reaction time 119879 was reaction tem-perature 119860 was preexponential factor 119864

119886was activation

energy induced by oxygenolysis of coal and 119877 representedgas constant Based on mechanism of the chemical reactionkinetics the construction on 119897119879 was performed by utilizingln(minus ln(1 minus 119886)1198792) Besides according to the obtained slopeactivation energy 119864

119886of the reaction was expected to be

calculated According to Table 3 the activation energy of thecoal samples after the treatment was improved to differentdegrees when the temperature varied from 50∘C to 150∘C

in comparison with those before the treatment After thetreatment using inorganic phosphorus agents the coal dealtwith zinc phosphate showed a significant change to theactivation energy In contrast the optimal effects were foundto the coal treated with the organic phosphorus agent tris(2-chloroethyl) phosphate (TCEP) The improvement of theactivation energy indicated that the higher the energy neededfor the low temperature oxidation of coal is themore difficultthe reaction happens

33 Oxidation Products As seen in Figure 5 as an index gasof CSC the CO released in the oxidation of coal samplespresented increased concentrations with the temperatureHowever after the treatment using PFRs the concentrations

Journal of Spectroscopy 7

Table 3 Activation energy of the coal samples before and after treatment

Coal samples Activation energy(kJsdotmolminus1)Raw coal Coal-K Coal-Na Coal-Zn Coal-BDP Coal-APP Coal-TCEP

ZT 746 764 773 757 981 814 1146BLT 761 832 783 805 821 906 1152XQ 1198 1301 1247 1265 1319 1426 1789

of CO caused by the combustion of coal samples apparentlyvaried For the XQ coking coal before the treatment 259 ppmof CO was generated in the oxidation process at 100∘CHowever after the treatment the concentration of CO pro-duced reduced to 156 ppm at minimum With the increasingtemperature the coal samples treated with TCEP generated493 ppm of CO at 200∘C Similar rules were also shown tothe BLT and ZT coal At 200∘C the concentrations of COreleased by the BLT coal before and after the treatment were10994 ppm and 1345 ppm separately while those emitted bythe ZT coal were 15732 ppm at maximum and 2240 ppm atminimumThe inhibiting efficiency is expressed as shown inthe following formula

119864 = Cr minus CtCrtimes 100 (2)

where 119864 is the inhibiting rate of the inhibitor to the coalsample Cr denotes the amount of CO released from theraw coal in the experiment with the unit of 10minus6 Ct showsthe amount of CO released from the coal treated with theinhibitor under the same condition with the unit of 10minus6

According to the results calculated using formula (2) themaximal inhibiting rates of the phosphorous flame retardantsto the ZT BLT and XQ coal were shown to be 535 529and 396 at 100∘C respectively While these values changedto 857 871 and 864 at 200∘C separatelyThis revealedthat compared with the combustion at a temperature lowerthan 100∘C the phosphorous flame retardants show moreobvious inhibition effects on the CSC at a high temperatureBesides comparing with the CO production the CO

2and

C2H4emission show the similar performance after the

treatment of PFRs (Figures 6 and 7) For example the ZT coaltreated by TCEP has only 5527 ppm CO

2emission at 200∘C

while the raw coal peaks at 39343 ppm At 200∘C the C2H4

yield of BLT coal climbs to 432 ppm but the coal treated byammonium phosphate (APP) only reaches 141 ppm

34 Flame-Retardant Mechanism With the application ofPFRs phosphorus compounds were decomposed in thecombustion process of polymers with P-containing flameretardants owing to the effect of heat accompanying with thefollowing changes [20]

P-containing compoundsheating997888997888997888997888997888rarr

phosphoric acidheating997888997888997888997888997888rarr metaphosphoric acid

heating997888997888997888997888997888rarrpolymetaphosphate

(3)

Polymetaphosphate as a nonvolatile stable compound coverson the surface of the polymer thus forming a charring layerSince no flaming evaporative combustion or decomposi-tion combustion would happen to simple substance carbonpolymetaphosphate can inhibit the combustion In additionsince phosphoric acid and polymetaphosphate show strongdehydration properties carbonized films were formed on thesurface of the polymer thus inhibiting the combustion Thisis the flame-retardant mechanism of PFRs in the condensedphase of polymers PFRs are also a kind of radical scavengersThe mass-spectrometric technique revealed that PO wasgenerated in any P-containing compounds in the combustionof polymers It can combine with the hydrogen atoms in theflaming area thus restraining the flaming [21] The specificaction is expressed as

POlowast +Hlowast 997888rarr HPOlowast (4)

HPOlowast +Hlowast 997888rarr H2+ POlowast (5)

The phosphorus could inhibit the self-ignition of coal effi-ciently Superabundant phosphorus in coal also work againstthe clean and efficient utilization of coal When the coal wasadopted as boiler fuel P-containing compounds in coal willdecompose at high temperature and then form sedimentswhich are difficult to clear on the heating surface of boilerMoreover during the iron-making and steel-making processthe existence of phosphorus elementwill influence the qualityof iron and steel As the results the content of phosphorus incoal is strictly limited around the world Considering safetyfactors phosphorus flame retardants could be widely appliedin the abandoned area of colliery such as gob goaf and coalwaste heap However we still need comprehensively assess-ment before being utilized in storage and transportation ofcoal

4 Conclusions

It is essential to use effective flame retardants for the pre-vention of CSC so as to further guarantee the mine safetyAlthough PFRs have played a significant role in the industrialproduction of polymers more exploration is still neededin its role in the inhibition of CSC Laboratorial researchwas attempted to explore the inhibition mechanism of PFRson the organic functional groups in coal molecules Theexperimental results revealed that phosphorus could effec-tually inhibit CSC at a high temperature interval Althoughcertain effects could also be emerged at a low temperaturerange they were less obvious compared with that at a hightemperature with a maximal inhibiting rate above 80

8 Journal of Spectroscopy

0

5000

10000

15000

20000

25000

30000

35000

40000

45000

CO2

emiss

ion

(ppm

)

Untreated ZTZT-KZT-NaZT-Zn

Zn-APPZT-BDPZT-TCEP

40 60 80 100 120 140 160 180 200 220

Temperature (∘C)

(a) ZT coalCO

2em

issio

n (p

pm)

40 60 80 100 120 140 160 180 200 220

28000

24000

20000

16000

12000

8000

4000

0

Untreated BLTBLT-KBLT-NaBLT-Zn

BLT-APPBLT-BDPBLT-TCEP

Temperature (∘C)

(b) BLT coal

CO2

emiss

ion

(ppm

)

40 60 80 100 120 140 160 180 200 220

0

2000

4000

6000

8000

Untreated XQXQ-KXQ-NaXQ-Zn

XQ-APPXQ-BDPXQ-TCEP

Temperature (∘C)

(c) XQ coal

Figure 6 The CO2emission of coal samples before and after treatment

The results obtained using the FTIR indicated that for thecoal samples with different coal ranks the C-O structuresin the coal after the treatment were obviously weakenedSimilar results were also obtained in the thermal analysis andtemperature programming experiment using P-containingcompounds can reduce the heat released in the combustion ofcoal and increase the difficulty in the reaction between coaland oxygen This research provides a favorable reference tothe application of P-containing inhibitors

Competing Interests

The author declares that they have no competing interests

Acknowledgments

This study is funded by the Project of China National NaturalScience Foundation (no 51604185) Open Projects of StateKey Laboratory of Coal Resources and Safe Mining CUMT

Journal of Spectroscopy 9C 2

H4

emiss

ion

(ppm

)

1000

800

600

400

200

0

Untreated ZTZT-KZT-NaZT-Zn

Zn-APPZT-BDPZT-TCEP

40 60 80 100 120 140 160 180 200 220

Temperature (∘C)

(a) ZT coal

40 60 80 100 120 140 160 180 200 220

minus100

0

100

200

300

400

500

C 2H

4em

issio

n (p

pm)

Untreated BLTBLT-KBLT-NaBLT-Zn

BLT-APPBLT-BDPBLT-TCEP

Temperature (∘C)

(b) BLT coal

40 60 80 100 120 140 160 180 200 220

minus50

0

50

100

150

200

250

C 2H

4em

issio

n (p

pm)

Untreated XQXQ-KXQ-NaXQ-Zn

XQ-APPXQ-BDPXQ-TCEP

Temperature (∘C)

(c) XQ coal

Figure 7 The C2H4emission of coal samples before and after treatment

(SKLCRSM15KF07) and the Research Project Supported byShanxi Scholarship Council of China (2015-037)

References

[1] J Zhang W Choi T Ito K Takahashi and M Fujita ldquoMod-elling and parametric investigations on spontaneous heating incoal pilerdquo Fuel vol 176 pp 181ndash189 2016

[2] C Avila T Wu and E Lester ldquoPetrographic characterizationof coals as a tool to detect spontaneous combustion potentialrdquoFuel vol 125 pp 173ndash182 2014

[3] Q Deng YWang andM Liu ldquoStatistic analysis and enlighten-ment on coal mine accident of China from 2001sim2013 periodsrdquoCoal Technology vol 33 no 9 pp 73ndash75 2014

[4] Y Tang and S Xue ldquoLaboratory study on the spontaneouscombustion propensity of lignite undergone heating treatmentat low temperature in inert and low-oxygen environmentsrdquoEnergy amp Fuels vol 29 no 8 pp 4683ndash4689 2015

[5] R Song ldquoGeological exploration and treatment method ofspontaneous combustion of coal seamrdquo in Coal Geology Bureauof Shanxi Province Taiyuan pp 65ndash68 2012

[6] J Liu E Wang D Song S Wang and Y Niu ldquoEffect of rockstrength on failuremode andmechanical behavior of compositesamplesrdquo Arabian Journal of Geosciences vol 8 no 7 pp 4527ndash4539 2015

[7] Y Tang ldquoSources of underground CO crushing and ambienttemperature oxidation of coalrdquo Journal of Loss Prevention in theProcess Industries vol 38 pp 50ndash57 2015

10 Journal of Spectroscopy

[8] J C Hower J M K OrsquoKeefe K R Henke et al ldquoGaseousemissions and sublimates from the Truman Shepherd coal fireFloyd County Kentucky a re-investigation following attemptedmitigation of the firerdquo International Journal of Coal Geology vol116-117 pp 63ndash74 2013

[9] G B Stracher and T P Taylor ldquoCoal fires burning out of controlaround the world thermodynamic recipe for environmentalcatastropherdquo International Journal of Coal Geology vol 59 no1-2 pp 7ndash17 2004

[10] C L Dias M L S Oliveira J C Hower S R Taffarel R MKautzmann and L F O Silva ldquoNanominerals and ultrafineparticles from coal fires from Santa Catarina South BrazilrdquoInternational Journal of Coal Geology vol 122 pp 50ndash60 2014

[11] B Taraba and Z Pavelek ldquoInvestigation of the spontaneouscombustion susceptibility of coal using the pulse flow calori-metric method 25 years of experiencerdquo Fuel vol 125 pp 101ndash105 2014

[12] Y Yang Z Li S Hou F Gu S Gao and Y Tang ldquoThe shortestperiod of coal spontaneous combustion on the basis of oxidativeheat release intensityrdquo International Journal of Mining Scienceand Technology vol 24 no 1 pp 99ndash103 2014

[13] Y Lu and B Qin ldquoMechanical properties of inorganic solidifiedfoam for mining rock fracture fillingrdquoMaterials Express vol 5no 4 pp 291ndash299 2015

[14] L Zhang B Qin B Shi Q Wu and J Wang ldquoThe fire extin-guishing performances of foamed gel in coal minerdquo NaturalHazards vol 81 no 3 pp 1957ndash1969 2016

[15] Y-B Tang Z-H Li Y I Yang D-J Ma and H-J Ji ldquoEffect ofinorganic chloride on spontaneous combustion of coalrdquo Journalof the Southern African Institute of Mining and Metallurgy vol115 no 2 pp 87ndash92 2015

[16] D K Wang H He and P Yu ldquoFlame-retardant and thermaldegradation mechanism of low-density polyethylene modifiedwith aluminum hypophosphite and microencapsulated redphosphorusrdquo Journal of Applied Polymer Science vol 133 no 13Article ID 43225 2016

[17] Q Luo Y Yuan C Dong S Liu and J Zhao ldquoHighperformance fire-retarded epoxy imparted by a novelphenophosphazine-containing antiflaming compound atultra-low loadingrdquoMaterials Letters vol 169 pp 103ndash106 2016

[18] Y Tang ldquoAnalysis of coals with different spontaneous com-bustion characteristics using infrared spectrometryrdquo Journal ofApplied Spectroscopy vol 82 no 2 pp 316ndash321 2015

[19] Y Tang ldquoA laboratorial study of spontaneous combustioncharacteristics of the oil shale in Fushun Chinardquo CombustionScience and Technology vol 188 no 6 pp 997ndash1010 2016

[20] E D Weil and S V Levchik ldquo13-Overview of modes of actionand interaction of flame retardantsrdquo in Flame Retardants pp323ndash338 Hanser 2nd edition 2016

[21] Y Tang ldquoInhibition of low-temperature oxidation of bitumi-nous coal using a novel phase-transition aerosolrdquo Energy ampFuels vol 30 no 11 pp 9303ndash9309 2016

Submit your manuscripts athttpswwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Inorganic ChemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

International Journal ofPhotoenergy

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Carbohydrate Chemistry

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

Physical Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom

Analytical Methods in Chemistry

Journal of

Volume 2014

Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

SpectroscopyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Medicinal ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chromatography Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Applied ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Theoretical ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Spectroscopy

Analytical ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Quantum Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Organic Chemistry International

ElectrochemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CatalystsJournal of

Journal of Spectroscopy 7

Table 3 Activation energy of the coal samples before and after treatment

Coal samples Activation energy(kJsdotmolminus1)Raw coal Coal-K Coal-Na Coal-Zn Coal-BDP Coal-APP Coal-TCEP

ZT 746 764 773 757 981 814 1146BLT 761 832 783 805 821 906 1152XQ 1198 1301 1247 1265 1319 1426 1789

of CO caused by the combustion of coal samples apparentlyvaried For the XQ coking coal before the treatment 259 ppmof CO was generated in the oxidation process at 100∘CHowever after the treatment the concentration of CO pro-duced reduced to 156 ppm at minimum With the increasingtemperature the coal samples treated with TCEP generated493 ppm of CO at 200∘C Similar rules were also shown tothe BLT and ZT coal At 200∘C the concentrations of COreleased by the BLT coal before and after the treatment were10994 ppm and 1345 ppm separately while those emitted bythe ZT coal were 15732 ppm at maximum and 2240 ppm atminimumThe inhibiting efficiency is expressed as shown inthe following formula

119864 = Cr minus CtCrtimes 100 (2)

where 119864 is the inhibiting rate of the inhibitor to the coalsample Cr denotes the amount of CO released from theraw coal in the experiment with the unit of 10minus6 Ct showsthe amount of CO released from the coal treated with theinhibitor under the same condition with the unit of 10minus6

According to the results calculated using formula (2) themaximal inhibiting rates of the phosphorous flame retardantsto the ZT BLT and XQ coal were shown to be 535 529and 396 at 100∘C respectively While these values changedto 857 871 and 864 at 200∘C separatelyThis revealedthat compared with the combustion at a temperature lowerthan 100∘C the phosphorous flame retardants show moreobvious inhibition effects on the CSC at a high temperatureBesides comparing with the CO production the CO

2and

C2H4emission show the similar performance after the

treatment of PFRs (Figures 6 and 7) For example the ZT coaltreated by TCEP has only 5527 ppm CO

2emission at 200∘C

while the raw coal peaks at 39343 ppm At 200∘C the C2H4

yield of BLT coal climbs to 432 ppm but the coal treated byammonium phosphate (APP) only reaches 141 ppm

34 Flame-Retardant Mechanism With the application ofPFRs phosphorus compounds were decomposed in thecombustion process of polymers with P-containing flameretardants owing to the effect of heat accompanying with thefollowing changes [20]

P-containing compoundsheating997888997888997888997888997888rarr

phosphoric acidheating997888997888997888997888997888rarr metaphosphoric acid

heating997888997888997888997888997888rarrpolymetaphosphate

(3)

Polymetaphosphate as a nonvolatile stable compound coverson the surface of the polymer thus forming a charring layerSince no flaming evaporative combustion or decomposi-tion combustion would happen to simple substance carbonpolymetaphosphate can inhibit the combustion In additionsince phosphoric acid and polymetaphosphate show strongdehydration properties carbonized films were formed on thesurface of the polymer thus inhibiting the combustion Thisis the flame-retardant mechanism of PFRs in the condensedphase of polymers PFRs are also a kind of radical scavengersThe mass-spectrometric technique revealed that PO wasgenerated in any P-containing compounds in the combustionof polymers It can combine with the hydrogen atoms in theflaming area thus restraining the flaming [21] The specificaction is expressed as

POlowast +Hlowast 997888rarr HPOlowast (4)

HPOlowast +Hlowast 997888rarr H2+ POlowast (5)

The phosphorus could inhibit the self-ignition of coal effi-ciently Superabundant phosphorus in coal also work againstthe clean and efficient utilization of coal When the coal wasadopted as boiler fuel P-containing compounds in coal willdecompose at high temperature and then form sedimentswhich are difficult to clear on the heating surface of boilerMoreover during the iron-making and steel-making processthe existence of phosphorus elementwill influence the qualityof iron and steel As the results the content of phosphorus incoal is strictly limited around the world Considering safetyfactors phosphorus flame retardants could be widely appliedin the abandoned area of colliery such as gob goaf and coalwaste heap However we still need comprehensively assess-ment before being utilized in storage and transportation ofcoal

4 Conclusions

It is essential to use effective flame retardants for the pre-vention of CSC so as to further guarantee the mine safetyAlthough PFRs have played a significant role in the industrialproduction of polymers more exploration is still neededin its role in the inhibition of CSC Laboratorial researchwas attempted to explore the inhibition mechanism of PFRson the organic functional groups in coal molecules Theexperimental results revealed that phosphorus could effec-tually inhibit CSC at a high temperature interval Althoughcertain effects could also be emerged at a low temperaturerange they were less obvious compared with that at a hightemperature with a maximal inhibiting rate above 80

8 Journal of Spectroscopy

0

5000

10000

15000

20000

25000

30000

35000

40000

45000

CO2

emiss

ion

(ppm

)

Untreated ZTZT-KZT-NaZT-Zn

Zn-APPZT-BDPZT-TCEP

40 60 80 100 120 140 160 180 200 220

Temperature (∘C)

(a) ZT coalCO

2em

issio

n (p

pm)

40 60 80 100 120 140 160 180 200 220

28000

24000

20000

16000

12000

8000

4000

0

Untreated BLTBLT-KBLT-NaBLT-Zn

BLT-APPBLT-BDPBLT-TCEP

Temperature (∘C)

(b) BLT coal

CO2

emiss

ion

(ppm

)

40 60 80 100 120 140 160 180 200 220

0

2000

4000

6000

8000

Untreated XQXQ-KXQ-NaXQ-Zn

XQ-APPXQ-BDPXQ-TCEP

Temperature (∘C)

(c) XQ coal

Figure 6 The CO2emission of coal samples before and after treatment

The results obtained using the FTIR indicated that for thecoal samples with different coal ranks the C-O structuresin the coal after the treatment were obviously weakenedSimilar results were also obtained in the thermal analysis andtemperature programming experiment using P-containingcompounds can reduce the heat released in the combustion ofcoal and increase the difficulty in the reaction between coaland oxygen This research provides a favorable reference tothe application of P-containing inhibitors

Competing Interests

The author declares that they have no competing interests

Acknowledgments

This study is funded by the Project of China National NaturalScience Foundation (no 51604185) Open Projects of StateKey Laboratory of Coal Resources and Safe Mining CUMT

Journal of Spectroscopy 9C 2

H4

emiss

ion

(ppm

)

1000

800

600

400

200

0

Untreated ZTZT-KZT-NaZT-Zn

Zn-APPZT-BDPZT-TCEP

40 60 80 100 120 140 160 180 200 220

Temperature (∘C)

(a) ZT coal

40 60 80 100 120 140 160 180 200 220

minus100

0

100

200

300

400

500

C 2H

4em

issio

n (p

pm)

Untreated BLTBLT-KBLT-NaBLT-Zn

BLT-APPBLT-BDPBLT-TCEP

Temperature (∘C)

(b) BLT coal

40 60 80 100 120 140 160 180 200 220

minus50

0

50

100

150

200

250

C 2H

4em

issio

n (p

pm)

Untreated XQXQ-KXQ-NaXQ-Zn

XQ-APPXQ-BDPXQ-TCEP

Temperature (∘C)

(c) XQ coal

Figure 7 The C2H4emission of coal samples before and after treatment

(SKLCRSM15KF07) and the Research Project Supported byShanxi Scholarship Council of China (2015-037)

References

[1] J Zhang W Choi T Ito K Takahashi and M Fujita ldquoMod-elling and parametric investigations on spontaneous heating incoal pilerdquo Fuel vol 176 pp 181ndash189 2016

[2] C Avila T Wu and E Lester ldquoPetrographic characterizationof coals as a tool to detect spontaneous combustion potentialrdquoFuel vol 125 pp 173ndash182 2014

[3] Q Deng YWang andM Liu ldquoStatistic analysis and enlighten-ment on coal mine accident of China from 2001sim2013 periodsrdquoCoal Technology vol 33 no 9 pp 73ndash75 2014

[4] Y Tang and S Xue ldquoLaboratory study on the spontaneouscombustion propensity of lignite undergone heating treatmentat low temperature in inert and low-oxygen environmentsrdquoEnergy amp Fuels vol 29 no 8 pp 4683ndash4689 2015

[5] R Song ldquoGeological exploration and treatment method ofspontaneous combustion of coal seamrdquo in Coal Geology Bureauof Shanxi Province Taiyuan pp 65ndash68 2012

[6] J Liu E Wang D Song S Wang and Y Niu ldquoEffect of rockstrength on failuremode andmechanical behavior of compositesamplesrdquo Arabian Journal of Geosciences vol 8 no 7 pp 4527ndash4539 2015

[7] Y Tang ldquoSources of underground CO crushing and ambienttemperature oxidation of coalrdquo Journal of Loss Prevention in theProcess Industries vol 38 pp 50ndash57 2015

10 Journal of Spectroscopy

[8] J C Hower J M K OrsquoKeefe K R Henke et al ldquoGaseousemissions and sublimates from the Truman Shepherd coal fireFloyd County Kentucky a re-investigation following attemptedmitigation of the firerdquo International Journal of Coal Geology vol116-117 pp 63ndash74 2013

[9] G B Stracher and T P Taylor ldquoCoal fires burning out of controlaround the world thermodynamic recipe for environmentalcatastropherdquo International Journal of Coal Geology vol 59 no1-2 pp 7ndash17 2004

[10] C L Dias M L S Oliveira J C Hower S R Taffarel R MKautzmann and L F O Silva ldquoNanominerals and ultrafineparticles from coal fires from Santa Catarina South BrazilrdquoInternational Journal of Coal Geology vol 122 pp 50ndash60 2014

[11] B Taraba and Z Pavelek ldquoInvestigation of the spontaneouscombustion susceptibility of coal using the pulse flow calori-metric method 25 years of experiencerdquo Fuel vol 125 pp 101ndash105 2014

[12] Y Yang Z Li S Hou F Gu S Gao and Y Tang ldquoThe shortestperiod of coal spontaneous combustion on the basis of oxidativeheat release intensityrdquo International Journal of Mining Scienceand Technology vol 24 no 1 pp 99ndash103 2014

[13] Y Lu and B Qin ldquoMechanical properties of inorganic solidifiedfoam for mining rock fracture fillingrdquoMaterials Express vol 5no 4 pp 291ndash299 2015

[14] L Zhang B Qin B Shi Q Wu and J Wang ldquoThe fire extin-guishing performances of foamed gel in coal minerdquo NaturalHazards vol 81 no 3 pp 1957ndash1969 2016

[15] Y-B Tang Z-H Li Y I Yang D-J Ma and H-J Ji ldquoEffect ofinorganic chloride on spontaneous combustion of coalrdquo Journalof the Southern African Institute of Mining and Metallurgy vol115 no 2 pp 87ndash92 2015

[16] D K Wang H He and P Yu ldquoFlame-retardant and thermaldegradation mechanism of low-density polyethylene modifiedwith aluminum hypophosphite and microencapsulated redphosphorusrdquo Journal of Applied Polymer Science vol 133 no 13Article ID 43225 2016

[17] Q Luo Y Yuan C Dong S Liu and J Zhao ldquoHighperformance fire-retarded epoxy imparted by a novelphenophosphazine-containing antiflaming compound atultra-low loadingrdquoMaterials Letters vol 169 pp 103ndash106 2016

[18] Y Tang ldquoAnalysis of coals with different spontaneous com-bustion characteristics using infrared spectrometryrdquo Journal ofApplied Spectroscopy vol 82 no 2 pp 316ndash321 2015

[19] Y Tang ldquoA laboratorial study of spontaneous combustioncharacteristics of the oil shale in Fushun Chinardquo CombustionScience and Technology vol 188 no 6 pp 997ndash1010 2016

[20] E D Weil and S V Levchik ldquo13-Overview of modes of actionand interaction of flame retardantsrdquo in Flame Retardants pp323ndash338 Hanser 2nd edition 2016

[21] Y Tang ldquoInhibition of low-temperature oxidation of bitumi-nous coal using a novel phase-transition aerosolrdquo Energy ampFuels vol 30 no 11 pp 9303ndash9309 2016

Submit your manuscripts athttpswwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Inorganic ChemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

International Journal ofPhotoenergy

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Carbohydrate Chemistry

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

Physical Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom

Analytical Methods in Chemistry

Journal of

Volume 2014

Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

SpectroscopyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Medicinal ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chromatography Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Applied ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Theoretical ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Spectroscopy

Analytical ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Quantum Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Organic Chemistry International

ElectrochemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CatalystsJournal of

8 Journal of Spectroscopy

0

5000

10000

15000

20000

25000

30000

35000

40000

45000

CO2

emiss

ion

(ppm

)

Untreated ZTZT-KZT-NaZT-Zn

Zn-APPZT-BDPZT-TCEP

40 60 80 100 120 140 160 180 200 220

Temperature (∘C)

(a) ZT coalCO

2em

issio

n (p

pm)

40 60 80 100 120 140 160 180 200 220

28000

24000

20000

16000

12000

8000

4000

0

Untreated BLTBLT-KBLT-NaBLT-Zn

BLT-APPBLT-BDPBLT-TCEP

Temperature (∘C)

(b) BLT coal

CO2

emiss

ion

(ppm

)

40 60 80 100 120 140 160 180 200 220

0

2000

4000

6000

8000

Untreated XQXQ-KXQ-NaXQ-Zn

XQ-APPXQ-BDPXQ-TCEP

Temperature (∘C)

(c) XQ coal

Figure 6 The CO2emission of coal samples before and after treatment

The results obtained using the FTIR indicated that for thecoal samples with different coal ranks the C-O structuresin the coal after the treatment were obviously weakenedSimilar results were also obtained in the thermal analysis andtemperature programming experiment using P-containingcompounds can reduce the heat released in the combustion ofcoal and increase the difficulty in the reaction between coaland oxygen This research provides a favorable reference tothe application of P-containing inhibitors

Competing Interests

The author declares that they have no competing interests

Acknowledgments

This study is funded by the Project of China National NaturalScience Foundation (no 51604185) Open Projects of StateKey Laboratory of Coal Resources and Safe Mining CUMT

Journal of Spectroscopy 9C 2

H4

emiss

ion

(ppm

)

1000

800

600

400

200

0

Untreated ZTZT-KZT-NaZT-Zn

Zn-APPZT-BDPZT-TCEP

40 60 80 100 120 140 160 180 200 220

Temperature (∘C)

(a) ZT coal

40 60 80 100 120 140 160 180 200 220

minus100

0

100

200

300

400

500

C 2H

4em

issio

n (p

pm)

Untreated BLTBLT-KBLT-NaBLT-Zn

BLT-APPBLT-BDPBLT-TCEP

Temperature (∘C)

(b) BLT coal

40 60 80 100 120 140 160 180 200 220

minus50

0

50

100

150

200

250

C 2H

4em

issio

n (p

pm)

Untreated XQXQ-KXQ-NaXQ-Zn

XQ-APPXQ-BDPXQ-TCEP

Temperature (∘C)

(c) XQ coal

Figure 7 The C2H4emission of coal samples before and after treatment

(SKLCRSM15KF07) and the Research Project Supported byShanxi Scholarship Council of China (2015-037)

References

[1] J Zhang W Choi T Ito K Takahashi and M Fujita ldquoMod-elling and parametric investigations on spontaneous heating incoal pilerdquo Fuel vol 176 pp 181ndash189 2016

[2] C Avila T Wu and E Lester ldquoPetrographic characterizationof coals as a tool to detect spontaneous combustion potentialrdquoFuel vol 125 pp 173ndash182 2014

[3] Q Deng YWang andM Liu ldquoStatistic analysis and enlighten-ment on coal mine accident of China from 2001sim2013 periodsrdquoCoal Technology vol 33 no 9 pp 73ndash75 2014

[4] Y Tang and S Xue ldquoLaboratory study on the spontaneouscombustion propensity of lignite undergone heating treatmentat low temperature in inert and low-oxygen environmentsrdquoEnergy amp Fuels vol 29 no 8 pp 4683ndash4689 2015

[5] R Song ldquoGeological exploration and treatment method ofspontaneous combustion of coal seamrdquo in Coal Geology Bureauof Shanxi Province Taiyuan pp 65ndash68 2012

[6] J Liu E Wang D Song S Wang and Y Niu ldquoEffect of rockstrength on failuremode andmechanical behavior of compositesamplesrdquo Arabian Journal of Geosciences vol 8 no 7 pp 4527ndash4539 2015

[7] Y Tang ldquoSources of underground CO crushing and ambienttemperature oxidation of coalrdquo Journal of Loss Prevention in theProcess Industries vol 38 pp 50ndash57 2015

10 Journal of Spectroscopy

[8] J C Hower J M K OrsquoKeefe K R Henke et al ldquoGaseousemissions and sublimates from the Truman Shepherd coal fireFloyd County Kentucky a re-investigation following attemptedmitigation of the firerdquo International Journal of Coal Geology vol116-117 pp 63ndash74 2013

[9] G B Stracher and T P Taylor ldquoCoal fires burning out of controlaround the world thermodynamic recipe for environmentalcatastropherdquo International Journal of Coal Geology vol 59 no1-2 pp 7ndash17 2004

[10] C L Dias M L S Oliveira J C Hower S R Taffarel R MKautzmann and L F O Silva ldquoNanominerals and ultrafineparticles from coal fires from Santa Catarina South BrazilrdquoInternational Journal of Coal Geology vol 122 pp 50ndash60 2014

[11] B Taraba and Z Pavelek ldquoInvestigation of the spontaneouscombustion susceptibility of coal using the pulse flow calori-metric method 25 years of experiencerdquo Fuel vol 125 pp 101ndash105 2014

[12] Y Yang Z Li S Hou F Gu S Gao and Y Tang ldquoThe shortestperiod of coal spontaneous combustion on the basis of oxidativeheat release intensityrdquo International Journal of Mining Scienceand Technology vol 24 no 1 pp 99ndash103 2014

[13] Y Lu and B Qin ldquoMechanical properties of inorganic solidifiedfoam for mining rock fracture fillingrdquoMaterials Express vol 5no 4 pp 291ndash299 2015

[14] L Zhang B Qin B Shi Q Wu and J Wang ldquoThe fire extin-guishing performances of foamed gel in coal minerdquo NaturalHazards vol 81 no 3 pp 1957ndash1969 2016

[15] Y-B Tang Z-H Li Y I Yang D-J Ma and H-J Ji ldquoEffect ofinorganic chloride on spontaneous combustion of coalrdquo Journalof the Southern African Institute of Mining and Metallurgy vol115 no 2 pp 87ndash92 2015

[16] D K Wang H He and P Yu ldquoFlame-retardant and thermaldegradation mechanism of low-density polyethylene modifiedwith aluminum hypophosphite and microencapsulated redphosphorusrdquo Journal of Applied Polymer Science vol 133 no 13Article ID 43225 2016

[17] Q Luo Y Yuan C Dong S Liu and J Zhao ldquoHighperformance fire-retarded epoxy imparted by a novelphenophosphazine-containing antiflaming compound atultra-low loadingrdquoMaterials Letters vol 169 pp 103ndash106 2016

[18] Y Tang ldquoAnalysis of coals with different spontaneous com-bustion characteristics using infrared spectrometryrdquo Journal ofApplied Spectroscopy vol 82 no 2 pp 316ndash321 2015

[19] Y Tang ldquoA laboratorial study of spontaneous combustioncharacteristics of the oil shale in Fushun Chinardquo CombustionScience and Technology vol 188 no 6 pp 997ndash1010 2016

[20] E D Weil and S V Levchik ldquo13-Overview of modes of actionand interaction of flame retardantsrdquo in Flame Retardants pp323ndash338 Hanser 2nd edition 2016

[21] Y Tang ldquoInhibition of low-temperature oxidation of bitumi-nous coal using a novel phase-transition aerosolrdquo Energy ampFuels vol 30 no 11 pp 9303ndash9309 2016

Submit your manuscripts athttpswwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Inorganic ChemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

International Journal ofPhotoenergy

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Carbohydrate Chemistry

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

Physical Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom

Analytical Methods in Chemistry

Journal of

Volume 2014

Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

SpectroscopyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Medicinal ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chromatography Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Applied ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Theoretical ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Spectroscopy

Analytical ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Quantum Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Organic Chemistry International

ElectrochemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CatalystsJournal of

Journal of Spectroscopy 9C 2

H4

emiss

ion

(ppm

)

1000

800

600

400

200

0

Untreated ZTZT-KZT-NaZT-Zn

Zn-APPZT-BDPZT-TCEP

40 60 80 100 120 140 160 180 200 220

Temperature (∘C)

(a) ZT coal

40 60 80 100 120 140 160 180 200 220

minus100

0

100

200

300

400

500

C 2H

4em

issio

n (p

pm)

Untreated BLTBLT-KBLT-NaBLT-Zn

BLT-APPBLT-BDPBLT-TCEP

Temperature (∘C)

(b) BLT coal

40 60 80 100 120 140 160 180 200 220

minus50

0

50

100

150

200

250

C 2H

4em

issio

n (p

pm)

Untreated XQXQ-KXQ-NaXQ-Zn

XQ-APPXQ-BDPXQ-TCEP

Temperature (∘C)

(c) XQ coal

Figure 7 The C2H4emission of coal samples before and after treatment

(SKLCRSM15KF07) and the Research Project Supported byShanxi Scholarship Council of China (2015-037)

References

[1] J Zhang W Choi T Ito K Takahashi and M Fujita ldquoMod-elling and parametric investigations on spontaneous heating incoal pilerdquo Fuel vol 176 pp 181ndash189 2016

[2] C Avila T Wu and E Lester ldquoPetrographic characterizationof coals as a tool to detect spontaneous combustion potentialrdquoFuel vol 125 pp 173ndash182 2014

[3] Q Deng YWang andM Liu ldquoStatistic analysis and enlighten-ment on coal mine accident of China from 2001sim2013 periodsrdquoCoal Technology vol 33 no 9 pp 73ndash75 2014

[4] Y Tang and S Xue ldquoLaboratory study on the spontaneouscombustion propensity of lignite undergone heating treatmentat low temperature in inert and low-oxygen environmentsrdquoEnergy amp Fuels vol 29 no 8 pp 4683ndash4689 2015

[5] R Song ldquoGeological exploration and treatment method ofspontaneous combustion of coal seamrdquo in Coal Geology Bureauof Shanxi Province Taiyuan pp 65ndash68 2012

[6] J Liu E Wang D Song S Wang and Y Niu ldquoEffect of rockstrength on failuremode andmechanical behavior of compositesamplesrdquo Arabian Journal of Geosciences vol 8 no 7 pp 4527ndash4539 2015

[7] Y Tang ldquoSources of underground CO crushing and ambienttemperature oxidation of coalrdquo Journal of Loss Prevention in theProcess Industries vol 38 pp 50ndash57 2015

10 Journal of Spectroscopy

[8] J C Hower J M K OrsquoKeefe K R Henke et al ldquoGaseousemissions and sublimates from the Truman Shepherd coal fireFloyd County Kentucky a re-investigation following attemptedmitigation of the firerdquo International Journal of Coal Geology vol116-117 pp 63ndash74 2013

[9] G B Stracher and T P Taylor ldquoCoal fires burning out of controlaround the world thermodynamic recipe for environmentalcatastropherdquo International Journal of Coal Geology vol 59 no1-2 pp 7ndash17 2004

[10] C L Dias M L S Oliveira J C Hower S R Taffarel R MKautzmann and L F O Silva ldquoNanominerals and ultrafineparticles from coal fires from Santa Catarina South BrazilrdquoInternational Journal of Coal Geology vol 122 pp 50ndash60 2014

[11] B Taraba and Z Pavelek ldquoInvestigation of the spontaneouscombustion susceptibility of coal using the pulse flow calori-metric method 25 years of experiencerdquo Fuel vol 125 pp 101ndash105 2014

[12] Y Yang Z Li S Hou F Gu S Gao and Y Tang ldquoThe shortestperiod of coal spontaneous combustion on the basis of oxidativeheat release intensityrdquo International Journal of Mining Scienceand Technology vol 24 no 1 pp 99ndash103 2014

[13] Y Lu and B Qin ldquoMechanical properties of inorganic solidifiedfoam for mining rock fracture fillingrdquoMaterials Express vol 5no 4 pp 291ndash299 2015

[14] L Zhang B Qin B Shi Q Wu and J Wang ldquoThe fire extin-guishing performances of foamed gel in coal minerdquo NaturalHazards vol 81 no 3 pp 1957ndash1969 2016

[15] Y-B Tang Z-H Li Y I Yang D-J Ma and H-J Ji ldquoEffect ofinorganic chloride on spontaneous combustion of coalrdquo Journalof the Southern African Institute of Mining and Metallurgy vol115 no 2 pp 87ndash92 2015

[16] D K Wang H He and P Yu ldquoFlame-retardant and thermaldegradation mechanism of low-density polyethylene modifiedwith aluminum hypophosphite and microencapsulated redphosphorusrdquo Journal of Applied Polymer Science vol 133 no 13Article ID 43225 2016

[17] Q Luo Y Yuan C Dong S Liu and J Zhao ldquoHighperformance fire-retarded epoxy imparted by a novelphenophosphazine-containing antiflaming compound atultra-low loadingrdquoMaterials Letters vol 169 pp 103ndash106 2016

[18] Y Tang ldquoAnalysis of coals with different spontaneous com-bustion characteristics using infrared spectrometryrdquo Journal ofApplied Spectroscopy vol 82 no 2 pp 316ndash321 2015

[19] Y Tang ldquoA laboratorial study of spontaneous combustioncharacteristics of the oil shale in Fushun Chinardquo CombustionScience and Technology vol 188 no 6 pp 997ndash1010 2016

[20] E D Weil and S V Levchik ldquo13-Overview of modes of actionand interaction of flame retardantsrdquo in Flame Retardants pp323ndash338 Hanser 2nd edition 2016

[21] Y Tang ldquoInhibition of low-temperature oxidation of bitumi-nous coal using a novel phase-transition aerosolrdquo Energy ampFuels vol 30 no 11 pp 9303ndash9309 2016

Submit your manuscripts athttpswwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Inorganic ChemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

International Journal ofPhotoenergy

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Carbohydrate Chemistry

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

Physical Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom

Analytical Methods in Chemistry

Journal of

Volume 2014

Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

SpectroscopyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Medicinal ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chromatography Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Applied ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Theoretical ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Spectroscopy

Analytical ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Quantum Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Organic Chemistry International

ElectrochemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CatalystsJournal of

10 Journal of Spectroscopy

[8] J C Hower J M K OrsquoKeefe K R Henke et al ldquoGaseousemissions and sublimates from the Truman Shepherd coal fireFloyd County Kentucky a re-investigation following attemptedmitigation of the firerdquo International Journal of Coal Geology vol116-117 pp 63ndash74 2013

[9] G B Stracher and T P Taylor ldquoCoal fires burning out of controlaround the world thermodynamic recipe for environmentalcatastropherdquo International Journal of Coal Geology vol 59 no1-2 pp 7ndash17 2004

[10] C L Dias M L S Oliveira J C Hower S R Taffarel R MKautzmann and L F O Silva ldquoNanominerals and ultrafineparticles from coal fires from Santa Catarina South BrazilrdquoInternational Journal of Coal Geology vol 122 pp 50ndash60 2014

[11] B Taraba and Z Pavelek ldquoInvestigation of the spontaneouscombustion susceptibility of coal using the pulse flow calori-metric method 25 years of experiencerdquo Fuel vol 125 pp 101ndash105 2014

[12] Y Yang Z Li S Hou F Gu S Gao and Y Tang ldquoThe shortestperiod of coal spontaneous combustion on the basis of oxidativeheat release intensityrdquo International Journal of Mining Scienceand Technology vol 24 no 1 pp 99ndash103 2014

[13] Y Lu and B Qin ldquoMechanical properties of inorganic solidifiedfoam for mining rock fracture fillingrdquoMaterials Express vol 5no 4 pp 291ndash299 2015

[14] L Zhang B Qin B Shi Q Wu and J Wang ldquoThe fire extin-guishing performances of foamed gel in coal minerdquo NaturalHazards vol 81 no 3 pp 1957ndash1969 2016

[15] Y-B Tang Z-H Li Y I Yang D-J Ma and H-J Ji ldquoEffect ofinorganic chloride on spontaneous combustion of coalrdquo Journalof the Southern African Institute of Mining and Metallurgy vol115 no 2 pp 87ndash92 2015

[16] D K Wang H He and P Yu ldquoFlame-retardant and thermaldegradation mechanism of low-density polyethylene modifiedwith aluminum hypophosphite and microencapsulated redphosphorusrdquo Journal of Applied Polymer Science vol 133 no 13Article ID 43225 2016

[17] Q Luo Y Yuan C Dong S Liu and J Zhao ldquoHighperformance fire-retarded epoxy imparted by a novelphenophosphazine-containing antiflaming compound atultra-low loadingrdquoMaterials Letters vol 169 pp 103ndash106 2016

[18] Y Tang ldquoAnalysis of coals with different spontaneous com-bustion characteristics using infrared spectrometryrdquo Journal ofApplied Spectroscopy vol 82 no 2 pp 316ndash321 2015

[19] Y Tang ldquoA laboratorial study of spontaneous combustioncharacteristics of the oil shale in Fushun Chinardquo CombustionScience and Technology vol 188 no 6 pp 997ndash1010 2016

[20] E D Weil and S V Levchik ldquo13-Overview of modes of actionand interaction of flame retardantsrdquo in Flame Retardants pp323ndash338 Hanser 2nd edition 2016

[21] Y Tang ldquoInhibition of low-temperature oxidation of bitumi-nous coal using a novel phase-transition aerosolrdquo Energy ampFuels vol 30 no 11 pp 9303ndash9309 2016

Submit your manuscripts athttpswwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Inorganic ChemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

International Journal ofPhotoenergy

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Carbohydrate Chemistry

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

Physical Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom

Analytical Methods in Chemistry

Journal of

Volume 2014

Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

SpectroscopyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Medicinal ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chromatography Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Applied ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Theoretical ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Spectroscopy

Analytical ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Quantum Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Organic Chemistry International

ElectrochemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CatalystsJournal of

Submit your manuscripts athttpswwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Inorganic ChemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

International Journal ofPhotoenergy

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Carbohydrate Chemistry

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

Physical Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom

Analytical Methods in Chemistry

Journal of

Volume 2014

Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

SpectroscopyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Medicinal ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chromatography Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Applied ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Theoretical ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Spectroscopy

Analytical ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Quantum Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Organic Chemistry International

ElectrochemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CatalystsJournal of