A dual-gas sourced approach to methanol/power polygeneration:
system design and analysis
Prof. Zheng Li, Fen He, Minghua Wang
Tsinghua University
May 3rd, Dresden, Germany
4th International Freiberg Conference on IGCC & XtL Technologies
2
Outlines
Motivation of introducing dual gas source to polygeneration
Process description and simulation results
Discussion on system configuration design
CO2 emission comparison with coal to methanol process
3
Background and motivation China has abundant resources of coke gas,
but considerable amount is not used, leading to air pollution and energy waste.
Coke oven gas and coal derived syngashave supplementary characteristics in composition Coal derived syngas (CG) is rich in CO Coke oven gas (COG) is rich in H2 and
CH4
Water gas shift can be saved by adjusting the combination of CG and COG
Potential to use both CG and COG in polygeneration system: “dual-gas source”
Syngas H2 CO CO2 CH4 N2 Ar
COG 58.1 5.86 2.35 24.9 3.0 0.9
SCGP 29.8 62.9 2.1 0.04 4.3 0.9
Coking chamber
Oven
Coke oven gasCoking
coal
Emission 55%
Heat Recycle 45%
Coke Tar & others
0 5 10 15 20 25 30
others
Coking plant
City gas plant
Coke oven gas ( Billion Nm3)
used wasted
Steel plant
4
Basic idea of dual-gas sourced polygeneration Coal to Methanol
Coal Polygeneration
Dual-gas sourced Polygen.
Gasifier WGS
Gasifier/desulfur
CO2-CH4
Reformer
CG
CG
COG
CO2
Coal
Coal
MeOHSynthesis
Gasifier WGSCGCoal
Syngas Clean
SG SG
MeOH
TG
CO2
MeOHSynthesis
Syngas Clean
SG
MeOH
TG
SG GTCC
SG
Power
CO2
MeOHSynthesis
Syngas Clean
SG
MeOH
TG
SG GTCC
SG
Power
O2
5
Specification of key processes
Air separation unit LP operation, no air-side integration
Gasification Fluidized bed, dry feed (N2) @
30bar,1084C IP(33bar) & HP (133 bar) steam for
syngas cooling Acid gas removal
Methanol based physical absorption process (rectisol)
98 % CO2-removal; H2S < 0.1 ppm
No water gas shift process
Methanol synthesis Liquid phase reactor @66bar, 250C Once-through conversion without
recycle Gas turbine combined cycle
Scaleable E-class machine Fuel preheat, N2 dilution, No firing temperature reduction
GasificationIsland
CO2-CH4
Reformer
CG
COG
Coal
CO2
MeOHSynthesis
Syngas Clean
SGMeOH
Unconverted SG
SG
Gas turbine
SG
Power
HRSGSt.turbine
N2
Air
Air
O2
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Key process (1)Ash-agglomerating fluidized bed gasifier （AFBG）
Features of AFBG A local gasifier tech. Moderate gasification
pressure, much lower gasification temp.
Higher hydrogen content in syngas
Syngas(v.%)
AFBG
H2 39.7
CO 29.5
CO2 21.6
CH4 1.7
N2 6.5
Ar 0.9
Proximate Analysis (w%, air dry)
Moisture 2.52
Fixed carbon 62.91
Volatile 24.43
ASH 10.14
LHV (kJ/kg) 29.2
Ultimate Analysis (w%, air dry)
Carbon 69.94
ASH 12.66
Hydrogen 3.85
Nitrogen 0.36
Oxygen 12.73
Sulfur 0.46
Operation Parameters
Pressure/(bar) 30
Oxygen/coal (mass) 0.68
Steam/coal (mass) 1.7
Temp./( C) 1084
Carbon Conv. 95%
Cold gas efficiency 72%
GasifierCoal96.76%
Coal gas70.44%
LOSS17.83%
Slag8.72%
St1.55%
O20.90%
N20.23%
Wt0.56%
S0.53%
IPSt1.48%
HPSt1.53%
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Key process (2)High temperature catalytic CH4-CO2 reformer
Direct reforming
Steam reforming
CH4 partially oxidization
CH4 + CO2 = 2CO + 2H2 (∆Ho = 247 kJ/mol)
H2 + CO2 = H2O + CO (∆Ho = 35 kJ/mol)
CH4 + H2O = CO + 3H2 (∆Ho = 206 kJ/mol)
CO + H2O = CO2 + H2 (∆Ho = -41 kJ/mol)
CH4 + CO2 = 2CO + 2H2 (∆Ho = 247 kJ/mol)
CH4 + 0.5O2 = CO + 2H2 (∆Ho = -35.5 kJ/mol)
CH4 + CO2 = 2CO + 2H2 (∆Ho = 247 kJ/mol)
Strong endothermic process
Less strong endothermic process; steam is required
Moderate endothermic process, economy of stem use
Objective Identify proper ratio of coal gas,
coke oven gas, oxygen for a specified product gas with suitable H2/CO ratio
Challenge Detailed kinetic mechanism not
well known
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Key process (2)Modelling of the catalytic CH4-CO2 reformer Approach
3 possible pathways comparison Thermodynamic equilibrium assumption
Findings Similar results for pathway 1 & 3 CH4 content is mainly determined by O2 flow,
H2/carbon ratio by coke gas flow
Controllable variables Coke gas mass flow Oxygen mass flow
CCG
COG
R SG
CCG
COG
R SG
CCOG
CG
R SG
C
R
→
→
→
→
→
2 2 2
2 2
4 2 2 2
4 2 2 2 2
4 2 2
H +0.5O H O2CO+O 2COCH +2O CO +2H OCH +O CO +H O+H2CH +O 2CO+4H
4 2 2
4 2 2
4 2 2 2
CH +CO 2CO+2H OCH +H O CO+3HCH +2H O CO +4H
→
→
→
1% 2% 3% 4% 5%300
310
320
330
340
350
3601% 2% 3% 4% 5%
20
30
40
50
60
70
Coke
gas (
kmol
/hr)
CH4 in the product gas
Oxyg
en (k
mol
/hr)
(H2-CO2)/(CO+CO2)=2.1CH4 content <5%
Syngas from coal gasification @ 100kmol/hr
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Overall system exergy flow diagram
Feed in Product
Gasification coal / (t/d) 1822 Methanol / (kt/a) 216.4
Coke oven gas / (Nm3/h) 112430 Gross power / (MW) 437.75
Oxygen / (Nm3/h) 55950 Net power / (MW) 349
AUX power / (MW) 78.42 Sulfur / (t/a) 2391.3
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Discussion on system configuration design
0.60 0.65 0.70 0.75 0.80 0.85 0.900.44
0.45
0.46
0.47
0.48
0.49
0.5
1.0
1.5
2.0
2.5
3.0
3.5
0.35
0.40
0.45
0.50
η
xSPLIT
Efficiency η
R
mCoal
/mCOG
mCoal
/mCOG
Chemical to Power Ratio R
MeOH MeOH
COAL COAL COG COG
m LHV Powerm LHV m LHV
η ⋅ +=
⋅ +
CG CG/powerSPL totalITx m m=
Gasifier/desulfur
CO2-CH4
ReformerCG
COG
Coal
CO2
MeOHSynthesis
Syngas Clean
SG
MeOH
TG
SG GTCC
SG
Power
MeOH MeOHm LHVRPower⋅
=
Coal gas split ratio shapes the product portfolio and feedstock portfolio
Impact on configuration Portfolio of products R
Portfolio of feedstock:(mcoal / mCOG)
System thermal efficiency
Split Ratio
NOTE: coal input @1822 ton/day
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Comparison with coal to methanol process on CO2 emission
Sources of CO2 emission reduction Less coal consumption Better use of CO2 generated WGS process is spared
Shell Coal Gasifier
WGS
Gasifier/desulfer
CO2-CH4
Reformer
CG
CG
COG
CO2
Coal
Coal
MeOHSynthesis
Syngas Clean
SG SG MeOH
TG
CO2
MeOHSynthesis
Syngas Clean
SG
MeOH
TG
SG GTCC
SG
Power
CokingPlant
CokingCoal
CokeC to
MeO
H
Pol
ygen
.
CG/COG mole ratio：0.338
SCGP ABFG COG
Cold gas efficiency 76.30% 72.1% N/A
CO shift rate in WGS 61.1% N/A
Syngas efficiency 62.4% 83.9%
Coal assumption(kg/1000Nm3 syngas) 595.3 89.68 410.43
CO2 Emission(kg/1000Nm3 syngas) 757.99 121.23
Notes: 350Nm3 coke oven gas per ton of coke produced, AUX of ASU: 0.6 kWh/ Nm3 O2
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Conclusion and comments Merits of duel-gas sourced polygeneration
Improved efficiency without WGS, lower CO2 emission Utilization of coke oven gas
Consideration for the CH4-CO2 reformer CG/COG ratio determines the H2/carbon ratio of the outlet gas. Oxygen mass flow determines the CH4 content in the outlet gas
Findings through system simulation Coal gas split ratio shapes the product portfolio (electricity /methanol) and feedstock
portfolio (coke oven gas/coal gas) There’s an optimized coal gas split ratio corresponding to highest thermal efficiency The chemical process is relatively efficient process with much less exergy destruction
compared to the power generation process and gasification process.
Challengeable factors Despite of all the advantages regarding efficiency, resource utilization, CO2 emission
reduction potential, the economic performance is to be examined.
Thank you for your attention!
CONTACT INFORMATION
Prof. Li ZhengTsinghua BP Clean Energy Research and Education CenterTsinghua University, Beijing 100084, P.R. ChinaEmail: [email protected]
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Syngas89.28%
MeOH
MeOH, 33.66%
Flue gas61.41%
BFW0.25%
Compr.electricity
1.18%
S1.40%
CO20.41%
ST1.81%
Loss1.31%
Key process Once-through methanol synthesis reactor
Temperature / (oC) 250
Pressure/(bar) 66
Syngas compress work/(MW) 6.67
Syngas conversion rate /(mol.%) 38.7
Methanol content/(mol.%) 15.2
Crude methanol yield/(t/h) 30.33
33bar steam yield/(t/h) 29.1
Tail gas turbine work/(MW) 3.7
CO + 2H2 = CH3OHCO2 + 3H2 = CH3OH + H2OCO2+H2 = CO+H2OR
eact
ion
Feat
ure
Perf
orm
ance
Syngas219C|30bar
Heat Exchanger
LP MeOHReactor@66bar
COOLER1#
COOLER 2#
Split
Wash Tower
Tail gas
IP steam
Once-through liquid phase methanol synthesis reactor, without recycle of the tail gas
(H2-CO2)/(CO+CO2)=2.1
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Key process GTCC performance
Net Power346.9MW
Coal gas to GT45.3%
GTCC
Tail gas47.3%
Gross Power433MW56.90%
Loss 36.56%
Flue gas4.54%
ASU
Condenser2.58%
Air0.84%
To chemical processSteam from
chemical process
Stream Exergy/MW
In
GTFuel 705.91
GTAir 6.39
HST 14.55
B1IPST 9.64
B1HPST 9.98
GTN2 5.26
Out
Power 433.54
GT Tail 14.94
CondWT 34.88
Scaleable gas turbine E-Class machine type TIT=1100C, Tcomb=1350C, TAT=575C PR=17.8 N2 dillution, w/o air integration to ASU
3p Reheat HRSG 140/33/6 bar Approach 15C Pinch 10C
