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29th Oil Shale SymposiumGolden Colorado19-23 October 2009
Advances in Steady-State Process Modeling of Oil Shale Retorting
Rick Sherritt, Jimmy JiaJim Schmidt, Meilani Purnomo
19 Oct 2009Page 2
Process Simulators
• Used to develop models of chemical processes that consist of unit operations connected by streams
• Complete mass and heat balance calculations to determine unknown stream flow rates, temperatures, pressures, and compositions.
• Contain built-in models for familiar unit operations
• Contain databank of components and methods to calculate thermodynamic properties
19 Oct 2009Page 3
Aspen Plus
• Steady-state process simulator with breadth of features needed to simulate oil shale retorting processes
• Built-in libraries of unit operations, components and property methods for both hydrocarbon and mineral processing
• Allows user to create oil shale specific components and define their thermodynamic properties
• Ability to track particle size distribution• Ability to specify kinetics rates for gas/solid
reactions
19 Oct 2009Page 4
Model Components forGreen River Oil Shale
Stream
SubstreamMIXED
SubstreamCISOLID
PureComponents
Pseudo-components
Aspen Databank
INORGANICS
User-DefinedComponents
Kerogen
Char
H2OFree Water
FeCO3
SideriteNaAlSi2O6•H2O
Analcite
CaOCalciumOxide
SiO2
Quartz
CaMg(CO3)2
DolomiteKAl2(Si3Al)O10(OH)2
Illite
Fe2O3
Hematite
NaAlSi3O8
Albite
CaCO3
CalciteFeS2
Pyrite
Al2O3
Corundum
KAlSi3O8
K-Feldspar
Fe3O4
MagnetiteFe0.875S
Pyrrhotite
NaAlO2
SodiumAluminate
NaAlSi2O6
DehydratedAnalcite
MgOMagnesium
Oxide
FeSTroilite
C5 – 150oCLight Naphtha
150oC – 205oCHeavy Naphtha
205oC – 260oCKerosene
260oC – 315oCLight Gas Oil
315oC – 425oCHeavy Gas Oil
425oC – 600oCVacuum Gas Oil
600oC+Residuum
H2O
H2
CH4
N2
C2H4
O2
C2H6
Ar
C3H6
CO2
C3H8
CO
C4H8
H2S
C4H10
NH3
SO2
19 Oct 2009Page 5
Properties of User-Defined Components
• Gross heat of combustion of kerogen and char by Boie (1952)
• Standard heat of formation from heat of combustion
6.439270.1117.10411627.351kJ/kg298 SONHco
c wdwwwwH
NSCHo
co
f wwwwHH 42.226.978.328.141kJ/kgkJ/kg 298298
iwi element ofpercent weight where
19 Oct 2009Page 6
Properties of User-Defined Components
Kerogen CharFormula from Singleton et al. 1986 CH1.5N0.025O0.05S0.005 CH0.42N0.056O0.02S0.008
Molecular weight, kg/kmol 14.833 13.795Elemental composition, wt%Carbon 80.972 87.066Hydrogen 10.193 3.069Nitrogen 2.361 5.686Oxygen 5.393 2.320Sulfur 1.081 1.860Gross heat of combustion, kJ/kg 39549 34042Standard heat of formation, kJ/kg -1489.7 1115.9Standard heat of formation, kJ/kmol -22097 15394
Green River Oil Shale
19 Oct 2009Page 7
Properties of User-Defined Components
• Green River kerogen and char – Camp (1987)
maxmin4
53
42
321 K whereKkJ/kmol TTTTcTcTcTccCp
Kerogen Char Free WaterMW, kg/kmol 14.833 13.795 18.015
c1 3.311∙100 -1.626∙100 5.084∙101
c2 7.793∙10-2 5.943∙10-2 2.131∙10-1
c3 -2.453∙10-5 -2.464∙10-5 -6.314∙10-4
c4 0 0 6.487∙10-7
c5 0 0 0
Tmin, K 273 273 273
Tmax, K 750 1000 623
• Heat capacity
19 Oct 2009Page 8
Data for Pseudo-components• Green River shale oil - Miknis (1988)
0
100
200
300
400
500
600
700
0 20 40 60 80 100
Weight % distilled
Tru
e b
oili
ng
tem
per
atu
re,
oC
0.70
0.75
0.80
0.85
0.90
0.95
1.00
1.05
1.10
0 20 40 60 80 100
Midpoint % distilled
Sp
ecif
ic g
ravi
ty, k
g/m
3
0.08
0.09
0.10
0.11
0.12
0.13
0.14
0 20 40 60 80 100
Midpoint % distilled
Hyd
rog
en m
ass
frac
tio
n
0.000
0.005
0.010
0.015
0.020
0.025
0.030
0.035
0 20 40 60 80 100
Midpoint % distilled
Nit
rog
en m
ass
frac
tio
n
0.004
0.005
0.005
0.006
0.006
0.007
0.007
0.008
0.008
0 20 40 60 80 100
Midpoint % distilled
Su
lfu
r m
ass
frac
tio
n
0.00
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0 20 40 60 80 100
Midpoint % distilled
Oxy
gen
mas
s fr
acti
on
19 Oct 2009Page 9
Generated Properties of Psuedo-components
Component FormulaMol. Weight
g/gmol
Lower Boiling Temperature
oC
Upper Boiling Temperature
oCLight naphtha C8.5H16.4N0.10O0.45S0.03 128.3 C5 150
Heavy naphtha C10.1H19.0N0.18O0.53S0.03 152.0 150 205
Kerosene C13.1H23.4N0.22O0.26S0.04 188.9 205 260
Light gas oil C15.9H27.6N0.37O0.34S0.04 231.4 260 315
Heavy gas oil C21.2H34.4N0.59O0.53S0.06 308.5 315 425
Vacuum gas oil C33.6H51.6N1.3O0.48S0.09 483.9 425 600
Residuum C40.7H56.8N1.4O2.5S0.11 609.5 600 700
• Green River shale oil
19 Oct 2009Page 10
Composition of Green River Oil Shale Brons & Siskin (1989)
Component FormulaMol. Weight
g/gmolwt%
dry basisKerogen 19.8
Siderite FeCO3 115.9 2.4
Dolomite CaMg(CO3)2 184.4 22.8
Calcite CaCO3 100.1 14.1
Illite K(Al2)(Si3Al)O10(OH)2 398.3 10.9
Analcime NaAlSi2O6·H2O 220.2 0.9
Dawsonite NaAlCO3(OH)2 144.0 0.6
Pyrite FeS2 120.0 1.6
Quartz SiO2 60.1 13.2
Albite NaAlSi3O8 262.2 13.7Total 100.0
19 Oct 2009Page 11
Example – Union B
• Developed by Unocal• Operating plant near Parachute CO• 1986 – 1991• 10,000 bbl/d design• 4.5 MM bbl shale oil• Reeg et al. 1990• Mathematical model (Braun & Lewis
1985)
19 Oct 2009Page 12
Union B
19 Oct 2009Page 13
Union B Simulation Flowsheet
28
15
16
1
18
2
7
9
5
6
11
10
12
33
34
14 35
4
8
13
17
3
1932
31
SCRUBBER
GASCOMPR
GASSPLIT
PYRORXTRPYROSEP
DEHYDSEPDEHYD
VAPSEP
BOTHX
FEEDMIXR
GASHTRCRACKING
FINALSEP
PRODTANK
Hot Gas
SpentShale
RetortVapour
Shale Oil
Kerogen
Raw OilShale
Mineral
Free Water
Water
Gas
19 Oct 2009Page 14
Mineral reaction stoichiometryand reaction temperature
Reactant Reaction EquationPeak
oCAnalcite NaAlSi2O6·H2O NaAlSi2O6 + H2O 150-400
Dawsonite NaAlCO3(OH)2 NaAlO2 + CO2 + H2O 300, 440
Pyrite 0.875FeS2 + 0.75H2 Fe0.875S + 0.75H2S 450-550
Siderite 3FeCO3 Fe3O4 + CO + 2CO2 500-600
Magnetite Fe3O4 + H2S FeS + Fe2O3 + H2O
Illite K(Al2)(Si3Al)O10(OH)2 KAlSi3O8 + Al2O3 + H2O 550, 900
Dolomite CaMg(CO3)2 CaCO3 + MgO + CO2 790
Calcite CaCO3 CaO + CO2 860-1010
19 Oct 2009Page 15
Kerogen Pyrolysis Stoichiometryfor Green River oil shale from Singleton et al.(1986)
Component
Molecularweightg/gmol
wt%of kerogen
moles per mole kerogen
Kerogen 14.83 -100.000 -1.00000Methane 16.04 1.399 0.01293Hydrogen 2.02 0.297 0.02189Carbon monoxide 28.01 0.564 0.00298
Carbon dioxide 44.01 3.542 0.01194Hydrogen sulfide 34.08 0.229 0.00099Water 18.01 1.208 0.00995Ethene 28.05 0.304 0.00161Ethane 30.07 0.894 0.00441
Propene 44.10 0.582 0.00205Propane 56.11 0.659 0.00222Butene 58.12 0.519 0.00137Butane 43.19 0.519 0.00132Gas subtotal 10.714
Light naphtha 128.3 0.985 0.00114Heavy naphtha 152.0 5.018 0.00490Kerosene 188.9 7.267 0.00571Light gas oil 231.4 9.001 0.00577Heavy gas oil 308.5 20.626 0.00992
Vacuum gas oil 483.9 22.814 0.00699Residuum 609.5 3.036 0.00074Oil subtotal 68.746
Char 13.80 20.539 0.22085
Assume Union B retort and laboratory assay have same stoichiometry due to similarity in heating rates and maximum temperatures.
19 Oct 2009Page 16
Oil Cracking in Hot Gas Recycle Furnace
• Stoichiometry based on Bissell et al. (1985), Burnham (1980) and Voge and Good (1949)
Light naphtha Heavy naphtha Kerosene
MWg/gmol
wt%of light
naphtha
moles per mole light naphtha
wt%of heavy naphtha
moles per mole heavy naphtha
wt%of kerosene
moles per mole
keroseneKERO 188.9 -100.0 -1.00000HNAP 152.0 -100.0 -1.00000 11.6 0.14383LNAP 128.3 -100.0 -1.00000 23.1 0.27411 11.6 0.17038CH4 16.04 5.8 0.46521 4.5 0.42352 4.5 0.52652
H2 2.02 1.9 1.20483 1.5 1.09686 1.5 1.36360
CO 28.01 3.4 0.15356 2.6 0.13980 2.6 0.17379C2H4 28.05 11.2 0.51132 8.6 0.46550 8.6 0.57871
C2H6 30.07 8.1 0.34454 6.2 0.31366 6.2 0.38994
C3H6 44.10 10.7 0.32540 8.2 0.29624 8.2 0.36828
C3H8 56.11 4.7 0.13767 3.6 0.12533 3.6 0.15581
C4H8 58.12 14.1 0.32353 10.9 0.29454 10.9 0.36616
C4H10 43.19 2.2 0.04897 1.7 0.04459 1.7 0.05543
Coke 13.80 37.9 3.52600 29.1 3.21003 29.1 3.99066
19 Oct 2009Page 17
Oil Cracking in Recycle Furnace
• Kinetic Model D from Bissell et al. (1985)• First-order with same activation energy for each fraction• Pre-exponential factor depends on average molecular weight
TEefk /1
1
Oil fraction
Averagemolecular weight
g/gmol
Relative cracking rate factorAi
Light naphtha 128.28 2.9
Heavy naphtha 151.97 4.5
Kerosene 188.92 7.6
iii kyA
dt
dy
f1 = 1.04∙108 s-1 and E1 = 19588 K
19 Oct 2009Page 18
Predicted effect of hot gas temperature and scrubber temperature on oil cracking
0.0%
0.2%
0.4%
0.6%
0.8%
1.0%
1.2%
1.4%
1.6%
1.8%
500 540 580 620
Hot gas temperature, C
Oil
yie
ld lo
ss
, wt% 68 C
60 C
50 C
40 C
30 C
19 Oct 2009Page 19
Predicted effect of hot gas temperature and scrubber temperature on compressor power
0
5
10
15
20
25
500 540 580 620
Hot gas temperature, C
Co
mp
res
so
r B
HP
, MW
68 C
60 C
50 C
40 C
30 C
19 Oct 2009Page 20
Predicted effect of hot gas temperature and scrubber temperature on gas heating and cooling
-200
-100
0
100
200
300
400
500 540 580 620
Hot gas temperature, C
He
ati
ng
an
d c
oo
ling
du
ty, M
W 30 C
40 C
50 C
60 C
68 C
68 C
60 C
50 C
40 C
30 C
Heating
Cooling
19 Oct 2009Page 21
Conclusions
• A general purpose process simulator is a useful tool for evaluating oil shale conversion processes
• A few oil shale specific components and their properties need to be supplied. Data is available in the literature.
• Built-in unit operation models are usually adequate for steady state mass and heat balances