19-22 May 2014Dresden/Radebeul, Germany

Kinetic model of hydropyrolysis b d h d lbased on the CPD model

Qingliang Guan, Dapeng Bi, Weiwei Xuan, Jiansheng Zhang*Department of thermal engineering, Tsinghua university, China

IFC 2014

Outline

Background

Kinetic model of hydropyrolysis

Results and discussion

Conclusions

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Background

Natural gas consumption in ChinaBillion m3 %

25

30

300

350

400

consumptiongrowth rate

Billion m %

Coal abundance

15

20

200

250

g

Converting coal to NG

5

10

50

100

150

Demand for NG grow

00

Data source: NBSC NDRC

Natural gas

NG grow rapidly

Reserve is

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Data source: NBSC, NDRCrelatively low

3

Background

faceCH4 content Hydrogasification CH4: 60%

High thermal efficiencyof exit gas (vol.)

Supercritical water gasification CH4: 30%

No methanation reactor

Supercritical water gasification CH4: 30%

Catalytic gasification CH4: 20%Lurgi CH : 10%Lurgi CH4: 10%

a

GE/Shell CH4: 0%

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Background

Hydrogasification/Hydropyrolysis

Coal + H2

CH4 + (H2O/CO/CO2/...) + light oil + char

High heating rate800 1000℃ 70 100bar

CH4 (H2O/CO/CO2/...) light oil char

800-1000℃, 70-100bar

Promote coal conversion and CH4 production4

Kinetic model study

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Background Existing hydropyrolysis models

Single kinetic rate modelDistrib ted acti ation energ model

Empirical Distributed activation energy model Active species model Kinetic model accounts for gaseous products

Network devolatilization models Functional group, depolymerization, vaporization

and cross linking (FG DVC) model Not applied to and cross-linking (FG-DVC) model Chemical percolation devolatilization (CPD) model FLASHCHAIN model

pphydropyrolysis

CPD modelhydropyrolysis model

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Hydrogenation reactions6

Kinetic model of hydropyrolysis A brief introduction to CPD model (Grant. Energy&Fuel. 1989)

(b) Bridge scission mechanism

(a) Chemical structure of coal macromolecules

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(c) tar formation mechanism

7

Kinetic model of hydropyrolysis Chemical structure parameters of coal as input parameters

Mδ = average molecular weight of a side chainMcl = average molecular weight of an aromatic clusterp0 = the initial number of bridgesσ+1 = the coordination number

Chemical structure parameters

c0 = the initial number of char bridges

Chemical structure parameters 13C NMR experiments Correlated with coal analysis data (when the coal analysis data is in

the range of Table 1)the range of Table 1)

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Kinetic model of hydropyrolysis What is different when coal is heated in H2 ?

Comparison of pyrolysis and hydropyrolysis at 873K, 3MPa

H2 increase coal conversion, CH4 and H2O yield

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Kinetic model of hydropyrolysis

Metaplast (tar precursors) is a reactive fragment

The hydrogenation reaction is in competition with the crosslinking The hydrogenation reaction is in competition with the crosslinking

reaction

fi i l i i

Tar VaporLabile Bridge

Scission

Vapor-LiquidEquilibrium 2

hydH

cross=

Rp

Rdm E

Infinite Coal

MatrixFinite Fragments

(Metaplast)

Reattached Metaplast

Scission

Crosslinking

Hydrogenation

metahyd cross metaexp( )dm ER R A m

dt RT

2Hhyd meta

Hexp( )

1p ER A m

p RT

Methane

2

2

H

cross metaH

1

1 exp( )1

p RT

ER A mp RT

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Kinetic model of hydropyrolysis Gas composition

Use a light gas submodel developed by Genetti (1999)The ield of o gen containing species are corrected The yield of oxygen-containing species are corrected

Ultimate yield of oxygen-containing species: mol•(mol C)-1（Johnson and Tran,1980）

Oxygenated species O/C ≦ 0.1 O/C ﹥ 0.1CO 0.2[O/C] 0.02+0.1([O/C]-0.1)CO 0 0 2([O/C] 0 )

and Tran,1980）

CO2 0 0.2([O/C]-0.1)H2O 0.68[O/C] 0.068+0.4([O/C]-0.1)

Experimental data in wire-mesh Experimental data in wire mesh reactors Anthony and Howard. Fuel. 1976 Guell and Kandiyoti

VerifyHydropyrolysis model

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Guell and Kandiyoti. Energy&Fuel. 1993

Strugnell and Patrick. Fuel. 199511

Results and discussion Hydropyrolysis yield for coal from lignite to low rank bituminous

β=0.0035 atm-1

The model predictions agree ell ith the e perimental data The model predictions agree well with the experimental data Some deviations

70

80

gas +10%

20

CH4

40

50

60 -10% tar total

ld, d

af/%

10%

10

15 CO CO2

ld, d

af/%

+10%

10%

20

30

40

Pred

icte

d yi

e

5

10

Pred

icte

d yi

e -10%

0 10 20 30 40 50 60 70 800

10

P

Experimental yield, daf/%0 5 10 15 20

0

P

Experimental yield, daf/%

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Experiment (Strugnell and Patrick. Fuel. 1995): heating rate: 1000℃•s-1，final temperature: 1000℃holding time: 2s，pressure: 7MPa

Hollow: coal types not in the range shown in Tab. 1

12

Results and discussionTang. Fuel Processing Technology. 1999 Tang. Fuel Processing Technology. 1999

The effect of coal type Total yield vs. carbon content of parent coal

CH ield s H/C ratio of parent coal

total CH4

30

experiment

CH4 yield vs. H/C ratio of parent coal

80

experimentCarbon content

20

25experiment predicted

daf/%

70

experiment predicted

daf/%

Carbon contentH/C ratio

10

15

CH

4 yie

ld, d

50

60

Tota

l yie

ld,

0.7 0.8 0.9 1.0

5

H/C ratio of parent coal60 65 70 75 80 85 90

40

Carbon content of parent coal, daf/%

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p

Experiment (Strugnell and Patrick. Fuel. 1995): heating rate: 1000℃•s-1，final temperature: 1000℃holding time: 2s，pressure: 7MPa

Hollow: coal types not in the range shown in Tab. 1

13

Results and discussion

The effect of final temperature

β=0 004 atm-1 β 0.004 atm

80

100

﹜ pyrolysis, 69atmpyrolysis 1atm

tartotal60

70

hydropyrolysis, 69atmpyrolysis 69atm

60

d, d

af/%

pyrolysis, 1atm hydropyrolysis, 69atm

30

40

50

gas

d, d

af/%

pyrolysis, 69atmgas

20

40

Yie

ld

10

20

30

CH4

others

CH4Yie

ld

400 600 800 1000 12000

Temperature/℃400 600 800 1000 12000

CO4

Temperature/℃

H2O

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Experiment (Anthony and Howard. Fuel. 1976): coal: Pittsburgh No. 8, heating rate: 65~750℃•s-1，residence time: 2s

14

Results and discussion

The effect of hydrogen pressure (mixture of He/H2 at 69atm)

β=0 004 atm-1 β 0.004 atm

70 60

50

60

d, d

af/% 40

gas

daf/%

40 H2/He(ptotal=69atm)

Tota

l yie

ld

Anthony's experimentAnthony's model

H2

20others

CH4Yie

ld, d

0 10 20 30 40 50 60 7030

Hydrogen partial pressure/atm

Anthony s model This paper

0 10 20 30 40 50 60 700

COH2O

Hydrogen pressure/atm

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Experiment (Anthony and Howard. Fuel. 1976): coal: Pittsburgh No. 8, heating rate: 65~750℃•s-1，residence time: 2s

15

Results and discussion The effect of hydrogen pressure (pure H2)

Li b l β 0 004 t 1 Pitt b h N 8 l β 0 004 t 1

80

100

totalpyrolysis

tar﹜80

100

tar total﹜pyrolysis

Linby coal, β=0.004 atm-1 Pittsburgh No. 8 coal, β=0.004 atm-1

60

﹜

d, d

af/%

hydropyrolysis60

d, d

af/%

hydropyrolysis﹜﹜

20

40

Yie

ld20

40

Yie

ld

0 20 40 60 80 100 120 140 1600

Pressure/atm0 20 40 60 80 100 120 140 160

0

Pressure/atm

1

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Experiment (Guell and Kandiyoti. Energy&Fuel. 1993): heating rate: 1000℃•s-1, final temperature: 700℃, holding time: 2s

16

Conclusion A kinetic model of hydropyrolysis was proposed based on the CPD

network model. The model predictions of volatile yield and yield of methane agree with the experimental data β has a value ofmethane agree with the experimental data, β has a value of 0.0035~0.004 atm-1.

The model was used to investigate the effect of coal type final The model was used to investigate the effect of coal type, final temperature, and hydrogen pressure. The gas, tar and CH4 yield increase with temperature, and tar yield are constant at high temperatures The gas and CH4 yield increase with hydrogentemperatures. The gas and CH4 yield increase with hydrogen pressure while tar yield decrease with hydrogen pressure, which leads to a minimum of total yield at 10 bar. As the carbon content of the parent coal increases, volatile yield of hydropyrolysis first p , y y py yincrease slightly and then decrease when the carbon content of the parent coal is above 75%. Methane yield of hydropyrolysis increase slightly with the H/C ratio of the parent coal in the scope of this

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study.

17

THANK YOU FOR YOUR ATTENTION !

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