principi di combustione e gassificazione di solidiwpage.unina.it/anddanna/capri/capri...

Piero Salatino, Osvalda SennecaPiero Salatino, Osvalda Senneca

DipartimentoDipartimento didi IngegneriaIngegneria ChimicaChimicaUniversitàUniversità deglidegli StudiStudi didi NapoliNapoli Federico IIFederico II

IstitutoIstituto di Ricerche sulla Combustione di Ricerche sulla Combustione ConsiglioConsiglio Nazionale delle Nazionale delle RicercheRicerche

PRINCIPI DI COMBUSTIONE E GASSIFICAZIONE DI SOLIDI

PRINCIPI DI COMBUSTIONE E GASSIFICAZIONE PRINCIPI DI COMBUSTIONE E GASSIFICAZIONE DI SOLIDIDI SOLIDI

Shrinkage,Secondary fragmentation

Swelling,Primary fragmentation

Size and morphological

changes

Thermal annealing(change of turbostratic carbon structure,

ash sintering/melting)

Oxidation by H2O, CO2, H2Oxidation by O2Coal depolymerization, Tar/gas release,

Metaplast cross-linking and resolidification

Chemical and microtextural

changes

Char gasificationChar combustionDevolatilization

OUTLINE OF THE STAGES OF COAL GASIFICATIONand related coal transformations

OUTLINE OF THE STAGES OF COAL GASIFICATIONOUTLINE OF THE STAGES OF COAL GASIFICATIONand related coal transformationsand related coal transformations

• Coal can be represented as reasonablyordered polyaromatic domains withamorphous aliphatic groups;

• Stage I of the coalification process movesfrom the nearly amorphous parent coalmaterial to yield ordered polycyclic lamellae(C%≅90), approaching a first coalificationpole;

• Stage II of the coalification process yieldscondensation of polyaromatic domains withhydrogen release approaching a second coalification pole;

PYROLYSIS VERSUS THERMAL ANNEALING:THE “TWO-COMPONENT” HYPOTHESIS

OF COAL STRUCTURE

PYROLYSIS VERSUS THERMAL ANNEALING:PYROLYSIS VERSUS THERMAL ANNEALING:THE THE ““TWOTWO--COMPONENTCOMPONENT”” HYPOTHESIS HYPOTHESIS

OF COAL STRUCTUREOF COAL STRUCTURE

Stage IStage II

van Krevelen diagram (taken from Hurt, 1998)

• Carbonization resembles (but does notreproduce) the coalification process, exhibiting a first and a secondcarbonization poles;

• Pyrolysis may be assumed as stage I of carbonization (C%<90);

• Thermal annealing represents stage II of the carbonization process, yieldingstacking and condensation of polyaromaticdomains with hydrogen release;

• Changes (sintering/melting) of mineral matter further add on the complexity of thethermally-activated transformations of coal.

after Fletcher (2005)

MODELLING DEVOLATILIZATION OF NON-SOFTENING COALS

MODELLING DEVOLATILIZATION MODELLING DEVOLATILIZATION OF NONOF NON--SOFTENING COALSSOFTENING COALS

FG DVC [Solomon & coworkers]

FLASHCHAIN [Niksa & coworkers]

CPD [Fletcher & coworkers]

Rates and yields of devolatilization products (char, tar, light gases) predicted accounting for: structural models of coal(assessed via NMR or inferred through elemental analysis), vapor pressure equilibria, kinetics of coal fragmentation, metaplastcross-linking and decomposition.

MODELLING THE CHEMISTRY OF COAL DEVOLATILIZATION: STRUCTURAL MODELS

MODELLING THE CHEMISTRY OF COAL MODELLING THE CHEMISTRY OF COAL DEVOLATILIZATION: STRUCTURAL MODELSDEVOLATILIZATION: STRUCTURAL MODELS

FRAGMENTATION OF THE COAL NETWORKDURING PRIMARY PYROLYSIS

FRAGMENTATION OF THE COAL NETWORKFRAGMENTATION OF THE COAL NETWORKDURING PRIMARY PYROLYSISDURING PRIMARY PYROLYSIS

after Fletcher (2005)

THE ROLE OF “METAPLASTS”THE ROLE OF THE ROLE OF ““METAPLASTSMETAPLASTS””

after Fletcher (2005)

DEVOLATILIZATION AT HIGH-PRESSUREDEVOLATILIZATION AT HIGHDEVOLATILIZATION AT HIGH--PRESSUREPRESSURE

after Yu et al. (2007)

after Suuberg (1977)

DEVOLATILIZATION AT HIGH-PRESSUREDEVOLATILIZATION AT HIGHDEVOLATILIZATION AT HIGH--PRESSUREPRESSURE

Retention and/or crosslinking

of tars

COAL SOFTENING AND “SWELLING”AT HIGH PRESSURE

COAL SOFTENING AND COAL SOFTENING AND ““SWELLINGSWELLING””AT HIGH PRESSUREAT HIGH PRESSURE

after Wall et al. (2002) after Zeng and Fletcher (2005)

• Smaller weight loss and comparativelyeven smaller tar yield as pressureincreases.

• Hindered tar release favours “metaplast” accumulation at moderately high pressureswhich, in turn, promotes coal softening and swelling.

• Secondary coking favoured by hindranceof tar vaporization and repolymerization of metaplasts.

COAL DEVOLATILIZATION AT HIGH PRESSURE: HIGHLIGHTS

COAL DEVOLATILIZATION AT HIGH COAL DEVOLATILIZATION AT HIGH PRESSURE: HIGHLIGHTSPRESSURE: HIGHLIGHTS

after Zeng & Fletcher (2005)

MODELLING DEVOLATILIZATION AT HIGH-PRESSUREMODELLING DEVOLATILIZATION AT HIGHMODELLING DEVOLATILIZATION AT HIGH--PRESSUREPRESSURE

MODELLING DEVOLATILIZATION OF SOFTENING COALS

MODELLING DEVOLATILIZATION MODELLING DEVOLATILIZATION OF SOFTENING COALSOF SOFTENING COALS

after Oh, Peters and Howard (1989)

after Yu et al. (2004)

MODELLING DEVOLATILIZATION OF SOFTENING COALS

MODELLING DEVOLATILIZATION MODELLING DEVOLATILIZATION OF SOFTENING COALSOF SOFTENING COALS

• Comprehensive models of devolatilization of non softeningcoals at atmospheric pressure are available, reasonably wellvalidated.

• Modelling of devolatilization at moderate/high pressure ismuch more immature and mostly qualitative.

• Additional focus is called on:– Plastic behaviour of softened coal– Enhanced metaplast cross-linking and resolidification– Coking during secondary pyrolysis

• Better assessment of the “memory” of devolatilization in charproperties:– Enhanced development of vescicular/cenospheric structures– Increased propensity to thermal annealing along with

gasification

MODELLING OF DEVOLATILIZATIONMODELLING OF DEVOLATILIZATIONMODELLING OF DEVOLATILIZATION

MODELLING PRIMARY FRAGMENTATION DURING DEVOLATILIZATION OF COALS

MODELLING PRIMARY FRAGMENTATION MODELLING PRIMARY FRAGMENTATION DURING DEVOLATILIZATION OF COALSDURING DEVOLATILIZATION OF COALS

PRIMARY FRAGMENTATION UNDER FBC CONDITIONS

PRIMARY FRAGMENTATION PRIMARY FRAGMENTATION UNDER FBC CONDITIONSUNDER FBC CONDITIONS

after Chirone and Massimilla (1989)

PRIMARY FRAGMENTATION IN PC FIRING (at atmospheric pressure)

PRIMARY FRAGMENTATION IN PC FIRING PRIMARY FRAGMENTATION IN PC FIRING (at atmospheric pressure)(at atmospheric pressure)

after Dacombe et al. (1999)

• There is a lack of primary fragmentation data and models suitable for application to high pressure.

• Smaller VM yield and larger coal plasticity duringpyrolysis might reduce the extent of primaryfragmentation, but experimental confirmation islacking.

• The formation of vescicular/cenospheric chars at high pressure might shift fragmentation from the devolatilization stage (primary) to the chargasification stage (secondary fragmentation)

PRIMARY FRAGMENTATIONPRIMARY FRAGMENTATIONPRIMARY FRAGMENTATION

MODELLING COMBUSTION AND GASIFICATION OF CHAR

MODELLING COMBUSTION AND GASIFICATION MODELLING COMBUSTION AND GASIFICATION OF CHAROF CHAR

Reazioni di combustione e gassificazione del char

ReazioniReazioni didi combustionecombustione e e gassificazionegassificazione del chardel char

Le reazioni di combustione del char sono: 1. C + ½ O2 → CO ∆H = -26.4 kcal/mol 2. C + O2 → CO2 ∆H = -94.2 kcal/mol cui si affianca la reazione in fase omogenea 3. CO + ½ O2 = CO2 ∆H = -67.6 kcal/mol

Le reazioni di gassificazione del char sono: 4. C + H2O = CO + H2 ∆H = 32.2 kcal/mol 5. C + CO2 = 2 CO ∆H = 41.4 kcal/mol 6. C + 2 H2 = CH4 ∆H = -20.2 kcal/mol

Cui vanno associate le seguenti reazioni in fase gas: 7. CO + H2O = H2 + CO2 ∆H = -9.2 kcal/mol 8. CO + 3 H2 = CH4 + H2O ∆H = -52.4 kcal/mol 9.H2 + ½ O2 = H2O ∆H = -58.6 kcal/mol

after Kajitani et al. (2002)

CINETICA INTRINSECA:APPROCCIO LUMPED

CINETICA INTRINSECA:CINETICA INTRINSECA:APPROCCIO LUMPEDAPPROCCIO LUMPED

• Lo schema lumped è inadeguato in condizioni estreme• I dati di cinetica intrinseca sono molto scatterati ed incerti• Equazioni di bilancio di materia e di energia (il problema del

trasporto)• Interazione tra fenomeni puramente termici e reazioni

eterogenee

MODELLI DI COMBUSTIONE/GASSIFICAZIONE DI

CHAR

MODELLI DI MODELLI DI COMBUSTIONE/GASSIFICAZIONE DI COMBUSTIONE/GASSIFICAZIONE DI

CHARCHAR

48

2

7

26

2

5

42

23

22

2

12

2

)(

)(

)(

)(

,)(

)(,)(

)(

CHHC

COOC

HOCOHC

COOC

COOCCOC

CCOCOOC

OCCOCOOOC

OCOC

→+

→

+→+

→

+→+

+→

+→+

→+

combustion

gasification

CINETICA INTRISECA SEMIDETTAGLIATACINETICA INTRISECA SEMIDETTAGLIATACINETICA INTRISECA SEMIDETTAGLIATA

CH

'6OH6CO

'4CO47

CO417CO C

)z(Pk)z(Pk)z(Pk)z(Pkk

)z(Pk)1(kR

222

2

2 +++++=

γγγ

2kPk

PkkPkkR

3O1

O312O21

O

2

22

2

+⋅

⋅+⋅=

CH

'6OH6CO

'4CO47

OH617OH C

)z(Pk)z(Pk)z(Pk)z(Pkk

)z(Pk)1(kR

222

2

2 +++++=

γγγ

CINETICA INTRISECA SEMIDETTAGLIATACINETICA INTRISECA SEMIDETTAGLIATACINETICA INTRISECA SEMIDETTAGLIATA

• Lo schema lumped è inadeguato in condizioni estreme• I dati di cinetica intrinseca sono molto scatterati ed incerti• Equazioni di bilancio di materia e di energia (il problema del

trasporto)• Interazione tra fenomeni puramente termici e reazioni

eterogenee

MODELLI DI COMBUSTIONE/GASSIFICAZIONE DI

CHAR

MODELLI DI MODELLI DI COMBUSTIONE/GASSIFICAZIONE DI COMBUSTIONE/GASSIFICAZIONE DI

CHARCHAR

0.001

0.01

0.1

1

10

100

1000

0.0004 0.0005 0.0006 0.0007 0.0008 0.0009

1/T, K-1

t gas

if, s

Liu et al.

Kajitani et al.

Tominaga et al., fast

Tominaga et al., slow

wen&chaung

boundary layer diffusion limit

@P=20bar; CO2=16%, H2O=50%, CO=H2=16%; dp=40µm

GASIFICATION TIME SCALESGASIFICATION TIME SCALESGASIFICATION TIME SCALES

rang

eof

res

iden

ce ti

mes

range of operating temperatures

• Lo schema lumped è inadeguato in condizioni estreme• I dati di cinetica intrinseca sono molto scatterati ed incerti• Equazioni di bilancio di materia e di energia (il problema del

trasporto)• Interazione tra fenomeni puramente termici e reazioni

eterogenee

MODELLI DI COMBUSTIONE/GASSIFICAZIONE DI

CHAR

MODELLI DI MODELLI DI COMBUSTIONE/GASSIFICAZIONE DI COMBUSTIONE/GASSIFICAZIONE DI

CHARCHAR

( )( )( )

( )εεερερρ

εεεε

−+=

−+=

−+=

−+=

1

1

1

1

sg

scgc

scgcc

sg

DDD

kkk

ccc

Solido pienoSv=1 cm2/g

Solido porosoSv=10-1000m2/g

Solido non poroso

1. Trasporto di materia per reagenti e prodotti attraverso lo strato limite gassoso 2. Trasporto di materia per reagenti e prodotti attraverso l’eventuale strato di

ceneri3. Reazione del gas sulla superficie del solido

Reagente gassoso A

Solido non poroso, ceneri incoerenti

( )

ASA

molg

AASAga

kcr

ScfL

DShk

rcckN

=

==

=−= ∞

"

"

)(Re,*

sm

moliA2

( )

ASA

molg

AASAog

kcr

ScfL

DShk

SrccSk

=

==

=−∞

"

"2

)(Re,*

Solido non poroso, ceneri coerenti

molg

g

g

gg

mol

g

DSc

Lv

D

LkSh

ρµµ

ρ

=

=

=

Re

In generale le reazioni eterogenee del tipo gas-solido sono caratterizzate da un network di processi chimici e fisici in serie-parallelo tra loro, ovvero:

1. Trasporto di materia per reagenti e prodotti attraverso lo strato limite gassoso 2. Trasporto di materia per reagenti e prodotti attraverso l’eventuale strato di ceneri3. Trasporto di materia all’interno dei pori del solido reagente4. Reazione del gas sulla superficie del solido

Solido poroso

Reagente gassoso A

Solido poroso

vAAA rxcDvct

c −∇⋅∇=⋅∇+∂

∂*

"AA rncD =⋅∇

A

z

y

Bilancio nella fase gas

Condizione al contorno sulla superficie solida

02 =∇ Ax

A

Ipotesi di unidimensionalità

vAA

eff kSrdz

cdD == "

2

2

)( ASAgA

eff cckdz

dcD −= ∞

z

y

Condizione al contorno sulla superficie solida

0=dz

dcD A

eff

A

3

2

223

2

][1

m

m

sm

mol

mm

mol

s

m =

Particella porosaipotesi di unidimensionalità

vAA

eff kSrdz

cdD == "

2

2

[ ]s

mDDeff

2

==τε

Dm=10-4-10-5 m2/sDK=10-6-10-7 m2/s

Datt=10-16-10-18 m2/s

323

33

2

223

2

1][

exp

exp

][][

m

mol

ssm

mol

cRT

Ekk

cRT

Ekk

sm

mol

m

m

sm

mol

mm

mol

s

m

Aov

nAov

=

−⋅=

−⋅=

==

k

)(

T

1

s

HDeff ∆−=β

Regime IIProfilo A”

Regime IProfilo A

>>1

Regime IIIProfilo C

<<1

>>1<<1Thiele

Biot/Sherwood( )

2

1

S

V 1

est

+⋅⋅=− n

D

Ck

eff

nAs

vϕ

eff

g

D

LkBi =

vseff

vA

eff

kHdz

Tdk

kdz

cdD

⋅∆−=

=

2

2

2

2

mol

g

D

LkSh=

Caso non isotermo

η<<1

η<0,5

η = 11/T

b II a

LnR

III I

Profili di concentrazione del reagente gassoso all’interno ed all’esterno di una

particella di char

Diagramma di Arrhenius

( )dX

XDXA

X

TkDShD

d

cdTcR

X

eash∫+

+

++

= ∞∞ *

0 )()(12

)(2

21

,,

αδα

( )[ ] ( ) ( )4412 ∞∞→→ −+−=∆−+∆ TTTT

d

NukHHR t

COCCOC σεαα

Apparent reaction kinetics for lumped kinetics(per unit external surface, linear kinetics, ϕ >>1):Apparent reaction kinetics for lumped kineticsApparent reaction kinetics for lumped kinetics

(per unit external surface, linear kinetics, (per unit external surface, linear kinetics, ϕ >>1):>>1):

• Lo schema lumped è inadeguato in condizioni estreme• I dati di cinetica intrinseca sono molto scatterati ed incerti• Equazioni di bilancio di materia e di energia (il problema del

trasporto)• Interazione tra fenomeni puramente termici e reazioni

eterogenee

MODELLI DI COMBUSTIONE/GASSIFICAZIONE DI

CHAR

MODELLI DI MODELLI DI COMBUSTIONE/GASSIFICAZIONE DI COMBUSTIONE/GASSIFICAZIONE DI

CHARCHAR

Shrinkage,Secondary fragmentation

Swelling,Primary fragmentation

Size and morphological

changes

Thermal annealing(change of turbostratic carbon structure,

ash sintering/melting)

Oxidation by H2O, CO2, H2Oxidation by O2Coal depolymerization, Tar/gas release,

Metaplast cross-linking and resolidification

Chemical and microtextural

changes

Char gasificationChar combustionDevolatilization

INTERAZIONE TRA FENOMENI PURAMENTE TERMICI E REAZIONI ETEROGENEE

INTERAZIONE TRA FENOMENI PURAMENTE INTERAZIONE TRA FENOMENI PURAMENTE TERMICI E REAZIONI ETEROGENEETERMICI E REAZIONI ETEROGENEE

FRAMMENTAZIONE SECONDARIAFRAMMENTAZIONE SECONDARIAFRAMMENTAZIONE SECONDARIA

After Wall et al. (2002)

after Kang et al. 1992

PERCOLAZIONEPERCOLAZIONEPERCOLAZIONE

PERCOLAZIONEPERCOLAZIONEPERCOLAZIONE

after Miccio, Salatino and Tina, 2000

increasing burn-off

PyrolysisPyrolysisCHARCHAR

GASIFICATIONGASIFICATIONPRODUCTSPRODUCTS

COALCOAL

HeterogeneousHeterogeneous gasificationgasification reactionsreactions

INTERAZIONE TRA FENOMENI PURAMENTE TERMICI E REAZIONI ETEROGENEEL’APPROCCIO CLASSICO

INTERAZIONE TRA FENOMENI PURAMENTE TERMICI E INTERAZIONE TRA FENOMENI PURAMENTE TERMICI E REAZIONI ETEROGENEEREAZIONI ETEROGENEELL’’APPROCCIO CLASSICOAPPROCCIO CLASSICO

PyrolysisPyrolysis

“YOUNG”YOUNG”CHARCHAR

GASIFICATIONGASIFICATIONPRODUCTSPRODUCTS

COALCOAL ““ ANNEALED”ANNEALED”CHARCHAR

AnnealingAnnealing

Purely thermally activated processes

HeterogeneousHeterogeneous gasificationgasification reactionsreactions

Interazione tra fenomeni puramente termici e reazioni eterogenee

L’approccio classico

Interazione tra fenomeni puramente termici e reazioni Interazione tra fenomeni puramente termici e reazioni eterogeneeeterogenee

LL’’approccioapproccio classicoclassico

PyrolysisPyrolysis

“YOUNG”YOUNG”CHARCHAR

GASIFICATIONGASIFICATIONPRODUCTSPRODUCTS

COALCOAL ““ ANNEALED”ANNEALED”CHARCHAR

AnnealingAnnealing

Purely thermally activated processes

HeterogeneousHeterogeneous gasificationgasification reactionsreactions

Interazione tra fenomeni puramente termici e reazioni eterogenee

L’approccio classico

Interazione tra fenomeni puramente termici e reazioni Interazione tra fenomeni puramente termici e reazioni eterogeneeeterogenee

LL’’approccioapproccio classicoclassico

volatile matter release

annealing

pyrolysis

stacking of graphene layers

change of carbon hybridization

course of heat-treatment, ξξξξ

crystallite growth

heterogeneous oxidation inhibited

heterogeneousoxidation

active

ξξξξ*

release of interlayer defects

release of in-plane defects

volatile matter release

annealing

pyrolysis

stacking of graphene layers

change of carbon hybridization

course of heat-treatment, ξξξξ

crystallite growth

heterogeneous oxidation inhibited

heterogeneousoxidation

active

ξξξξ*

release of interlayer defects

release of in-plane defects

after Senneca and Salatino, 2002

PYROLISI/ THERMAL ANNEALINGPYROLISI/ THERMAL ANNEALINGPYROLISI/ THERMAL ANNEALING

after Marsh and Griffiths (1982)

THERMAL ANNEALINGTHERMAL ANNEALINGTHERMAL ANNEALING

after Shim and Hurt, 2000

C-O2

A B

C D

0.05µm 0.05µm

0.05µm

0.05µm

900°C for 1 minin nitrogen

1350°C for 30 min in nitrogen

1165°C for 30 min in nitrogen

1165°C for 1 min in nitrogen after char oxidation

ORDINE CRISTALLOGRAFICO E TRATTAMENTO TERMICO

ORDINE CRISTALLOGRAFICO E ORDINE CRISTALLOGRAFICO E TRATTAMENTO TERMICOTRATTAMENTO TERMICO

Number distribution of angular orientations of frin ges in char samples subjected to different heat treatments.

Angle of orientation, deg

0 20 40 60 80 100 120 140 160 180

Num

ber

dist

ribut

ion,

%

0

5

10

15

20

25

30

900°C 1min

Angle of orientation, deg

0 20 40 60 80 100 120 140 160 180

Num

ber

dist

ribut

ion,

%

0

5

10

15

20

25

30

900°C 1min 1165°C 30min

Angle of orientation, deg

0 20 40 60 80 100 120 140 160 180

Num

ber

dist

ribut

ion,

%

0

5

10

15

20

25

30

900°C 1min 1165°C 30min

1350°C 30min

Angle of orientation, deg

0 20 40 60 80 100 120 140 160 180

Num

ber

dist

ribut

ion,

%

0

5

10

15

20

25

30

900°C 1min 1165°C 30min

1350°C 30min1165°C 30min with 1 oxygen pulse1165°C 30 min after char oxidation

ORDINE CRISTALLOGRAFICO E TRATTAMENTO TERMICO

ORDINE CRISTALLOGRAFICO E ORDINE CRISTALLOGRAFICO E TRATTAMENTO TERMICOTRATTAMENTO TERMICO

HT W/Ochar preoxidation

HT withchar preoxidation

INTERAZIONE TRA OSSIDAZIONE E ANNEALING INTERAZIONE TRA OSSIDAZIONE E ANNEALING INTERAZIONE TRA OSSIDAZIONE E ANNEALING

)E(FF

d)(RT

EexpAexp

F

F

RT

EexpFA

dt

dF

F,D

t

0

F,DD

0

F,DD

=

−⋅−=

−⋅⋅−=

∫ θθ

MODELLI DI THERMAL ANNEALINGDAEM model di Suuberg (1991)

MODELLI DI THERMAL ANNEALINGMODELLI DI THERMAL ANNEALINGDAEM model DAEM model didi SuubergSuuberg (1991)(1991)

( ) ( )[ ] )1n(1dd

0

tRTEexpA1n1RR

RR −−

∞

∞ −−+=−−

ξ annealing progress variable (0:young char; 1: annealed char)R reactivity of the heat treated charRo reactivity of the “young” charR∞ reactivity of the “fully annealed” charT heat treatment temperaturet time of heat treatment

( ) )RT/Eexp(Ak1kdt

ddd

n −⋅=−⋅= ξξ

MODELLI DI THERMAL ANNEALINGLa legge di potenza di Salatino e Senneca (1999)

MODELLI DI THERMAL ANNEALINGMODELLI DI THERMAL ANNEALINGLa La leggelegge didi potenzapotenza didi Salatino e Senneca (1999)Salatino e Senneca (1999)

MODELLI DI THERMAL ANNEALING“Diffusion” model di Bhatia et al. (2004)MODELLI DI THERMAL ANNEALINGMODELLI DI THERMAL ANNEALING“Diffusion” model “Diffusion” model didi Bhatia et al. (2004)Bhatia et al. (2004)

Senneca & Salatino, Combustion Flame 144 578 (2006)

Le scale temporaliLe scale temporaliLe scale temporali

Cy Ak

→ CA (1)

Cy* Ak

→ CA* (2)

2 Cy* + O2

y1

→ 2 Cy*(O) (3)

2 CA* + O2

A1

→ 2 CA*(O) (4)

Cy + O2 +Cy*(O) y2

→ CO2 + Cy*(O) (5)

Cy + C*y(O) y3

→ CO + Cy* (6)

CA + O2 +CA*(O) A2

→ CO2 + CA*(O) (7)

CA + CA*(O) A3

→ CO + CA* (8)

Un modello che include cinetica semidettagliata e thermal annealing

Un modello che include cinetica Un modello che include cinetica semidettagliatasemidettagliata e e thermalthermal annealingannealing

1/T [1/K]

0,0003 0,0004 0,0005 0,0006 0,0007 0,0008 0,0009 0,0010 0,0011

ln r

[1/s

]

-6

-4

-2

0

2

4

senza annealing (caso base)rid = 10rid = 100 (caso base)rid = 1000

Un modello che include cinetica semidettagliata e thermal annealing

Un modello che include cinetica Un modello che include cinetica semidettagliatasemidettagliata e e thermalthermal annealingannealing

Nagle, J., Strickland-Constable, R.F., Oxidation of carbon between 1000-2000°C, Proc. of Fifth Conf. Carbon, Vol. 1,

Macmillan, p.154 (1962)

GASIFICATION:TECHNOLOGY SURVEY

GASIFICATION:GASIFICATION:TECHNOLOGY SURVEYTECHNOLOGY SURVEY

gaseous fuels

hydrogenation

oxidation

slow pyrolysis

fast pyrolysis

steam reforming

Flow Regime moving bed fluidized bed entrained flow

Fuel type solids solids solids or liquids

fuel particle size 5 - 50 mm 0.5 - 5 mm < 500 microns

residence time 15 - 30 min 5 - 50 s 1 - 10 s

oxidizer air/oxygen air/oxygen oxygen

temperature at the exhaust

400 - 500 ºC 700 – 900 ºC 900 – 1400 ºC

ash handling slagging and non-slagging non-slagging always slagging

commercial technologies

Lurgi dry-ash (non-slagging), BGL (slagging)

GTI U-Gas, HT Winkler, KRW

GE Energy, Shell, Prenflo, ConocoPhillips, Noell

"moving" beds are mechanically stirred, fixed

beds are not

bed temperature lower than ash melting point

not suitable for high ash fuels

countercurrent flow suitable for high-ash fuelsnot suitable for poorly

grindable fuels

Note: The "transport" gasifier flow regime is between fluidized and entrained and can be air- or oxygen-blown.

Note

Oxygen Blown

• Entrained Flow– Texaco– E-GAS– Shell– Prenflo– Noell

• Fluidized Bed– HT Winkler– Foster Wheeler

• Moving Bed– British Gas Lurgi– Sasol– Lurgi

• Transport Reactor– Kellogg

Air Blown

• Fluidized Bed– HT Winkler– IGT “Ugas”– KRW– Foster Wheeler

• Spouted Bed– British Coal– Foster Wheeler

• Entrained Flow– Mitsubishi

• Transport Reactor– Kellogg

• Hybrid – Foster Wheeler– British Coal– ENERCON– FERCO/Silva

Slurry vs Dry

• Dry Feed Gasifier coupled with Waste Heat recoveryBoiler, (Shell gasification technology)

• Slurry Feed Gasifier coupled with Water Quench, (Texacogasification technology

DFG-WHB

SFG-WQ

DFGSFG

Slurry vs Dry

Syngas composition from entrained flow gasifiers

Availability of big IGCC plants:the learning curve

Availability of big IGCC plants:Availability of big IGCC plants:the learning curvethe learning curve

fuel pre-heating

gasifying agents pre-

heating

coaloxygensteam

DEVO sub-model(CPD Db)

COMBUSTIONsub-model (PFR)

GASIFICATIONsub-model (PFR)

.

.

i-th QUENCH(MIXER)

i-th HEATRECOVERY

.

.SEPARATION

syngas

waste water

slag

3 steps of quench / heat recovery

quench water

hot water

LP steam

pressurized water

HP hot water

material streams

heat streams

fuel pre-heating

biomass

DEVO sub-model(CHL Db)

COOLING SCREEN

COOLING JACKET

A “CHALLENGING” SYSTEMThe entrained flow gasifier

drying/devolatilizationswelling & primary fragmentation

particle-to-wall migration& slag buildup

gasification of suspended charsecondary fragmentation

wall gasification of char

VM and char combustion

ENTRAINED FLOW GASIFICATION: PHENOMENOLOGICAL HIGHL IGHTS