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