rmh & grinding

8/18/2019 Rmh & Grinding

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RAW MATERIAL HANDLING

AND GRINDING


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INTRODUCTION

In a cement plant the Cement Manufacturing Process consists of the

following:

Raw material handling

Raw Material Grinding

Coal handling

Coal GrindingPyro – Process

Cement Grinding

Cement PackingThese processes are are shown in the flow chart.


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Raw Material

andling

Raw Material

Grinding

Coal

andling

Coal

Grinding

Pyro ! Process

Cement

Grinding

Cement Packing


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Raw Material Handling

The raw materials used in cement plants are mainly limestone"

laterite" #au$ite and iron ore. The ma%or raw material is

limestone" which is supplied from limestone mines. The

limestone supplied from mines is of si&e up to one cu#ic meter

and therefore re'uires crushing for reducing to the re'uired

si&es. (ther raw materials are normally of re'uired si&e. The

raw material handling consists of the following operations and

is shown #y flow chart..

)imestone crushing

)imestone *tacking and *torage

)imestone Reclaiming

+eeding to limestone and additi,e hoppers


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)imestone Crushing

-elt con,eyors

)imestone

*tacking *torage

)imestone

Reclaiming

-elt con,eyors

)imestone opper

/dditi,e *tockyard

-elt con,eyors

/dditi,e

opper no.0/dditi,e

opper no.1


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Raw Material Crushing

)imestone mined from limestone mines ha,ing si&e up to

one cu#ic meter ha,e to #e crushed to the re'uired si&esdepending on the type of raw material grinding system

a,aila#le in the plant. There are different types of crushing

as gi,en #elow.

*ingle stage crushing

Primary crushing

*econdary crushingTertiary crushing


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Different tyes !f "rushers used f!r li#est!ne "rushing are

gi$en %el!w&

2aw Crusher

Gyratory Crusher

2aw type Gyratory Crushers

Cone Crusher

Roll Crusher

ammer Crushers

Impact Crushers

Impact!hammer crusher


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Different Tyes Crushers

'( )aw Crusher: ! It is mainly designed for medium

hard to ,ery hard materials and usually installed as primary crusher. There are two types of %aw

crushers. *ingle toggle %aw crushers is ideally

suited to hard and tough" #ut not so a#rasi,e

materials. 3ou#le toggle %aw crusher are suited for

highly a#rasi,e e$tremely hard and tough material.

Capacities of 14 – 0566 tph are a,aila#le with a

reduction ratio of 7!8: 0. *pecific powerconsumption of this crusher is 6.1 – 6.9 wh per

ton of material.


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*( Gyrat!ry Crusher: ! In cement industry

gyratory crusher is used for primarycrushing of limestone of medium hard to

,ery hard for higher capacities of around

0866 tph. It has a two to three times

capacity of %aw crusher for the same si&es

of feed opening and discharge slot. The

reduction ratio of this crusher is ;:0 to

04:0. The specific power consumption ofthis crusher is 0.5 to 5.7 times more than

the %aw crusher.


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+( )aw tye Gyrat!ry Crushers& ,

These crushers are designed to handle e,en #igger feed lumps than the compara#le si&e of the

gyratory crusher with the same cone diameter.

These crushers can #e installed for single stage

crushing. These crushers can #e installed for

crushing all type of material from ,ery hard to

soft e$cept wet or sticky material.


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-( C!ne Crusher&

In this type of crusher" the positions of the crushingcone and conical crushing ring are ad%acent to each

other. These crushers are mainly installed as secondary

or tertiary crushers. The reduction ratio is in the order

of 8 to 0. It is used for hard to ,ery hard =moderatelya#rasi,e> to fria#le material. The specific power

consumption of this crusher is 6.5 – 6.9 wh per ton

of material.


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/( Ha##er Crushers& ,

These are widely used in cement industry. They areused for si&e reduction of hard to medium hard

limestone and sometimes for wet and sticky material.

ammer mills work with reduction ratios as high as

0:96 to 0:76 as primary and 04:0 as secondarycrushers. It can #e installed for single stage crushing"

primary crushing or secondary crushing. Two types

of hammer crushers are manufactured? single shaft

and dou#le shaft hammer crushers and work with theimpact effect of the hammers. Capacities up to 1666

tph are a,aila#le.


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0( I#a"t Crushers& ,

These crushers are suita#le for non!a#rasi,e" from soft

to hard" slightly wet materials. The predominant stressused is impact" howe,er cut and attrition are also used.

The ma$imum reduction ratios are 96:0. There are two

types? single rotor impact and dou#le rotor impact

crushers. The specific power consumption of this

crusher is 6.9 – 0.6 wh per ton of material


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Impact crushers are capa#le of capacities of more

than 1666 tph.

The si&e reduction work of impact crushers is

limited to certain 'uality characteristics of the

crusher feed. These limits are:

Compressi,e strength: !@ 54666 l# per s'.inch

MohAs hardness: ! @ 9.4

Moisture: ! ma$ 16BClay content: ! 6B


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C A O C 3 3 C O


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CRITERIA 2OR CRU3HER 3ELECTION

0. Material to #e crushed:

! nature

! a#rasi,eness =B of silica>

! resistance to compression =kg per cm1>

! hardness

! moisture content


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4RE,7LENDING O2 RAW MATERIAL


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4RE 7LENDING O2 RAW MATERIAL

Essentials !f 4re,%lending: ! Today with the technological

ad,ancements in cement industry and increase in the specific

kiln ,olumes" a uniform 'uality of kiln feed has #ecome pre!re'uisites not only for optimum kiln output #ut also for 'uality

of the clinker. +or getting uniform 'uality of kiln feed the

pneumatic homogeni&ation of ground raw meal alone is not

sufficient and hence it has #ecome necessary to prehomogenise the raw material #y pre!#lending" #efore it is

fed to the grinding mills. It has another ad,antage of pre!

homogeni&ation of raw materials from non!homogeneous

materials mined #y selecti,e mining" manual mining ormechani&ed mining o,er a wider area.


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Tyes !f 4re,%lenders& ,

Pre!#lending consists of stacking and reclaiming.3ta"5ing: ! The stacking is the process of

depositing material of non!uniform 'uality in

layers =longitudinal or circular> o,er a period of

time. The following are different methods of

stacking.


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' L!ngitudinal st!"5iles


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'( L!ngitudinal st!"5iles

a> Roof!type stockpiles =Che,ron – method>

#> )ine!type stacking =Dindow – method>

c> Com#ination of che,ron window method

d> *trata method

e> Conical method

f> )ayer method


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*( Cir"ular st!"5iles

a> *ection – style Che,ron method

#> Continuous che,ron stacking

c> )ayer method


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Ch M h d 8Li 9 I hi k


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Che$r!n Meth!d 8Linear9: ! In this" a stacker

continuously tra,els #ack and forth o,er the stockpile

along its length and deposits the material in coneshaped layers. The stockpiling is performed either #y a

#elt con,eyor tripper or #y a stacker with rigid #oom"

which mo,es alongside the stockpile.The material

dumped centrally o,er the ridge flows on each side ofthe pile to form the re'uired layers. The pile increases

uniformly up to its ma$imum height. (ne draw#ack of

this method is the segregation of the material into

larger and smaller particles as it tum#les down thesides of the pile. 3ue to simplicity of operation this is

the most commonly used method.

Wind!w Meth!d 8Linear9: ! In this method piles are


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p

#uilt!up in a num#er of rows of limited cross section

one a#o,e other. This method eliminates the

disad,antage of material segregation as in che,ronmethod" #ut it is less adopted due to re'uirement of

more ela#orate stacking arrangement.

C!#%inati!n !f Che$r!n 6 Wind!w #eth!d8Linear9: ! +rom the ,iew point of #lending

efficiency this is the #est" #ut is rarely adopted due to

comple$ity of stacking arrangement.

3trata Meth!d 8Linear9: ! *trata method is more

intended reclaiming #y the side acting scrapper.


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3e"ti!nal style Che$r!n 3ta"5ing 8Cir"ular9&


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3e"ti!nal,style Che$r!n 3ta"5ing 8Cir"ular9& ,

The stockpiling in circular #lending #ed is

performed #y a #elt con,eyor" which is swi,el!

mounted in the #edAs center point. The cross

section of a circular stockpile can either triangular

or trape&oidal.

*tacking in this method is relati,elystraightforward and can #e compared to

longitudinal #eds. owe,er" this method produces

su#stantial ,ariations in the 'uality in the transition

&ones from one section to other.


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0. *ide Reclaiming


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1. +ront end Reclaiming

a> )uffing *craper Chain /ssem#ly

#> ori&ontal *craper Chain

c> -ucket Dheel Reclaimer

d> -arrel Reclaimer

5. E$ca,ating

a> -ucket Dheel on Pi,oted -ooms

#> -ucket Chain *ystem


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'( 3ide Re"lai#ing: ! E'uipment for side reclaiming

i f li # di h il


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comprises of a tra,eling #oom e$tending o,er the pile

and reclaiming is achie,ed #y the scraping action of a

luffing scraper chain assem#ly on one face of the pile.The material rakes down the #ase of the pile where it is

remo,ed #y a longitudinal #elt con,eyor under floor or

to one side of the stockpile. *uch reclaiming is normally

used for stockpiles #ased on strata system or conicalsystem.

*( 2r!nt end Re"lai#ing: ! It comprises a tra,eling #ridge

operating on rail tracks on either side of the stockpile.

The reclaimed material is remo,ed #y a #elt con,eyor.The reclaiming in this case is done #y any of the

following methods


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iii> 7u"5et Wheel Re"lai#er: ! In this case one or

# k h l i % i i h


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more #ucket wheels operate in con%unction with a

raking down de,ice. The raking down de,ice dislodges

the material and #rings it down within the reach of #uckets. These two mo,e automatically across the face

of the pile and their direction of mo,ement is re,ersed

with the help of limit switches at the #ridge ends.

*imultaneously" the #ridge mo,es forward in thelongitudinal direction for a present distance. The

material scooped #y the #uckets is fed on to a #elt

con,eyor mounted on the #ridge and in turn on to a

longitudinal #elt con,eyor for onward transmission.


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i9 7u"5et Wheel !n 4i$!ted 7!!#s: ! In this the #ucket


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wheel itself #ites its way through the entire height of

the dump in certain num#er of slices depending on the

#ucket wheel diameter. This method is suited forcoarse!grained moist or sticky material.

ii9 7u"5et Chain 3yste#: ! +or certain materials" it is

prefera#le to go in for a storage pit instead of astockpile. /#o,e the pit two gantries run on tracks.

+rom the upper gantry" raw material is dumped into

the pit from a distri#ution #elt. Running on the lower

gantry is a #ucket ladder e$ca,ator" which remo,es thedumped material.


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4RE,7LENDING E22ICIENC


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Efficiency of pre!#lending stockpile is measured

#y the ratio of standard de,iation of CaC(5

content of input material to standard de,iation of

CaC(5 content of output material. It is possi#le to

achie,e a #lending efficiency of ;:0 to 06: 0.

2a"t!rs affe"ting 7lending Effi"ien"y: ! The

factors affecting the #lending efficiency are:

,ariation in the incoming material

method of formation of stockpile


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RAW MATERIAL GRINDING

The raw material grinding is a process" which in,ol,es


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The raw material grinding is a process" which in,ol,es

preparation of raw mi$ for making clinker. The crushed

limestone along with the additi,es such as laterite" #au$ite

or iron ore in the re'uired proportions are ground raw

mills for getting raw meal of re'uired fineness.

The right choice of a raw grinding system is influenced #y

a series of techno!economic considerations including thelocal conditions. The system which has the highest

operational economy" coupled with low in,estment cost

and high relia#ility" has to #e aimed at.


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C. (perating Cost


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i> Energy

ii> Dear

iii> Manpower

3. In,estment Costs

i> Plant and Machinery

ii> Electricals and control system

iii> Ci,il construction

E. En,ironmental Regulation


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g

i> 3ust

ii> Hi#ration

+. Maintaina#ility Relia#ility

i> 3amage and Replacement of compounds


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i> 3amage and Replacement of compounds

ii> *kill of plant operating staff

iii> Comple$ity of design" replacement and

a,aila#ility

The most important factors in relation to a

modern dry process plant are the moisture

and grinda#ility of raw material and

specific power consumption.


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The ,ertical roller mills are different types such as Ring Roller

Mills" Ring -all Mills" -owl Mills" etc. The characteristic of

th ill i th t th i d ti i ff t d # ll


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these mills is that the si&e reduction is effected #y rollers on

compara#le grinding elements tra,eling o,er a circular #ed of

material. The material after passing under the rollers is su#%ectedto a preliminary classifying action #y a stream of air sweeping

through the mill. The air at high ,elocity lifts the material to the

classifier" which separates the coarse and fine particles. The fine

particles are entrained and the separated coarse particles fall

#ack to the ta#le. The separator could #e either static or

dynamic. The fine particles are collected later in an E*P or -ag

+ilter. In Hertical roller mills with e$ternal recirculation" the

no&&le ring ,elocity is lower = 96!76 m.per sec> than the mills

without e$ternal recirculation =;6!86 m. per sec>.


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Raw Mi; 2ineness: !

The ad$antages !f in"reasing the raw #i; fineness are:

*h t ti i d f h ti f d d i i


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*horter time re'uired for preheating of suspended raw mi$ in

preheater.

+aster calcination and clinkeri&ation reactions.

Increase in clinker production rate.

Reduction in specific fuel consumption.

The disad$antages !f in"reasing the raw #i; fineness are:

Increase in specific power consumption of raw mi$ grinding.

3epending on chemical and physical characteristics of the raw mi$"

optimum fineness has to fi$ed #y considering all the a#o,e

mentioned factors.


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4r!"ess !f drying raw #aterials in Raw Mills

The characteristic feature of the drying!grinding process is that

two different processes are generally performed in the grinding

mill The heat re' ired for dr ing the ra material is s pplied #


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mill. The heat re'uired for drying the raw material is supplied #y

hot gases from preheater or cooler or hot air generator and #y theheat generated #y comminution in the grinding process.

In #all mills for drying of raw material a drying compartment is

arranged in front of the grinding compartment of the mill. The

drying cham#er is e'uipped with lifters" #ut has no grindingmedia.

In the traditional #all mill the drying capacity is limited #y its

geometry. E,en at sufficient hot gas amount it was difficult to get

all necessary gas flow to pass the mill. The gas flow and dryingcapacity was normally decreased with mill si&e =grinding

capacity>.


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Meth!d !f De,dusting raw #ill gases

3e!dusting of raw mill e$haust gases are done #y the

following methods:

Gra$ity settling "ha#%ers:


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y g

Cy"l!nes

Multi"l!nes

7ag 2ilters

Gra$el %ed filter

Ele"tr!stati" 4re"iitat!r


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C


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Cyclones are low cost dustcollectors and it consists of twosections? a cylindrical and conicalone. /t the top of the cylindricalsection the dust laden gas enterstangentially. It spirals along the

walls downward and upward to theoutlet thim#le. 3ust is separatedfrom the gases #y the centrifugalforces. The efficiency of cyclonesdecreases with decreasing particlesi&es and in,ersely proportional toits diameter. It is used as a pre!collector.

MULTICLONE3


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Multicyclones are units ofcyclones installed in

com#inations of series and

parallel for high throughput

and high efficiency. The

efficiency of multicyclones

is in the range of 84!9B.

2a%ri" 2ilters: ! These are generally of #ag type" i.e. tu#es

with 566 mm diameter or less" and up to 06 m high? they

consists of wo,en or felted cloth" made from natural or

synthetic fi#ers. +a#ric filters can handle small particles in the

su# micron range at high efficiencies of .4B. The dust laden


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gases flow through the porous medium of ! the filter fa#ric!and deposits particles in the ,oids. /fter filling the ,oids" a

cake starts to #uild up on the fa#ricAs surface" which does most

of the filtering. Dhen the dust layer #ecomes too thick" an

increase in pressure drop results? this re'uires cleaning of the

fa#ric. 3epending on the characteristic of the dust and type offa#rics" the following methods are applied for cleaning.

a> -ag swinging

#> Re,erse air

c> Pulse pressure

d> *onic cleaning


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Ele"tr!stati" 4re"iitat!r 8E349& ! The principle of dust

collection is #ased on the utili&ation of the effect of gas

ioni&ation in a strong electric field" which is formed #y discharge

electrodes =corona effect" negati,e> and #y collecting electrodes


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electrodes =corona effect" negati,e> and #y collecting electrodes

=positi,e>. Collection of efficiencies of .;4B is attaina#leunder fa,ora#le conditions.

The complete electrostatic precipitation process consists of fi,e

#asic steps that operate on a continuous #asis:

0. Gas distri#ution into treatment &one

1. Particle charging L corona discharge =gas conduction>

5. 3eposition of dust on collecting electrodes

9. /ccumulation of dust

4. Remo,al of the collected material


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The process condition in E*P ,aries during raw mill and coal mill

shutdowns and the E*P performance ,aries.

The tripping of E*Ps with increase in C( content in the kiln e$haust

gases due to process fluctuations are ,ery common


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gases due to process fluctuations are ,ery common.

The disad,antage of #ag filter is it can not withstand high

temperatures" which happens during plant start!up and upset

conditions.

-ag filter system re'uires regular maintenance of cleaning system

and timely replacement of filter #ags.

The disad,antage of E*P is the snapping of electrodes and plant

stoppage for its rectification.


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Tyes !f 7lending

omogeni&ation of cement raw mi$ can #e performed on a #atch

#asis as well as continuously


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#asis as well as continuously.

7at"h %lending: ! +or #atch system two #lending silos? normally

one is called as #lending silo and other as storage silo. The

homogeni&ation process starts during the filling of #lending silo.

/fter filling the #lending silo" homogeni&ation process continues for

a#out one hour. Then it is discharged to the storage silo normallylocated at the #ottom of the #lending silo" where it is homogeni&ed

continuously and e$tracted for kiln feed. -atch type homogeni&ation

is applied in cases where the 'uality of the raw material widely

fluctuates and in relati,ely long time inter,als.


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R!le !f 7lending 3il! in ?uality C!ntr!l !f Raw Mi;

-lending silos ha,e a ma%or role in achie,ing uniform and consistent

'uality of raw mi$" which is essentially re'uired for getting ma$imum

output from the kiln and optimi&ing specific fuel and power

consumption. -lending silos" #y #lending process reduces the 'uality


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,ariation in the raw mi$. There are ,arious types #lending silos ha,ing #lending factor from 7:0 to 04:0. The #asic principle of #lending

process is one or com#ination of the following mechanisms.

3istri#ution of input raw meal at the #lending silo top.

Pneumatic dry #lending #y aeration of raw meal #y the aerationunits placed at the #ottom of silo.

*egmental aeration =octant or 'uadrant system> with difference in

the pressure of air supplied for aeration of ,arious segments for

thorough mi$ing of raw mi$.

Method of e$traction to kiln feed


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7lending 2a"t!r

+or calculation of #lending factor of a silo" input and output raw meal

samples are to #e collected in regular inter,als and to #e tested for

CaC(5 content.


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*ilo input samples to #e collected for a period of one theoretical filling

of silo with an inter,al not e$ceeding 0.4 hours and a minimum 96

samples are to #e collected. +or optimum #lending efficiency silo should

#e filled more than ;6B. The output samples are to #e collected at an

inter,al of 5 to 4 minutes after the input samples are collected and aminimum of 16 samples are to #e collected.

The standard de,iation of the input samples as well as output samples

are to #e calculated. The #lending factor is the ratio of standard

de,iation of input raw meal to standard de,iation of output raw meal.

The more the #lending factor" the #lending is more effecti,e.


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Fui&

0.3escri#e the o,er all processes found in cement industry

1.Dhat is raw material handling 3escri#e it in #lock diagram

5.)ist at least three types of crushers

9.There are two types of crushing . 3escri#e in detail


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4.Dhat is pre#lending7.Mention the e'uipments used for pre#lending

;.Dhat is stacking

8.ow many methods of stacking are there Mention stackers under

them.Drite all types of #all mill

06.Dhat is separator

00.Is tandem mill air swept mill

01.Dhat is the ad,antage of ,ertical roller mill o,er #all mill05.Hertical roller mill is air swept mill. True or +alse

rmh & grinding

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