PROCESS INTEGRATION FOR THE RETORTING OF OIL SHALE FINES Rick - - PowerPoint PPT Presentation

PROCESS INTEGRATION FOR THE RETORTING OF OIL SHALE FINES

Rick Sherritt, Gwen Chia, Ian Ng Procom Consultants Pty Ltd 30th Oil Shale Symposium Golden CO 18-20 Oct 2010

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OBJECTIVE

Ò Solid heat carrier (SHC) with complete combustion Ò Description of plant-wide model Ò Example of heat integration Ò Some observations Ò Conclusions

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OUTLINE

• Show the capabilities of modern process simulator programs for design

and optimization of an oil shale surface retorting process

OIL EXTRACTION USING SOLID HEAT CARRIER (SHC) PROCESS

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• Hot solids (usually shale ash) are recycled from the combustion step to mix

with the oil shale and heat it to pyrolysis temperature.

• The technology may include drying and preheating of feed streams as

well as heat recovery from shale ash and combustion gases.

• Pyrolysis vapours are cooled to separate product oil, water and gas.

SHC WITH PARTIAL OR COMPLETE COMBUSTION OF SPENT SHALE

Ò SHC technologies such as ATP

and Galoter use partial combustion of the spent shale to heat the recycled solids.

Ò The air rate is regulated to burn

• nly enough char to maintain the

pyrolysis temperature.

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• An alternative approach is to

supply excess air/oxygen to ensure complete combustion of the spent shale.

• Surplus heat must be removed to

maintain the temperatures.

Complete Combustion Partial Combustion

SHC USING DUAL CIRCULATING FLUIDISED BEDS (DCFB)

Ò A circulating fluidized bed (CFB)

combustor is well-suited for SHC with complete combustion.

É

Excess heat is removed by generating steam in membrane wall and external cooler.

É

A wide particle size distribution (up to 6mm) is accepted.

É

CFB combustion proven at large-scale in power generation industry.

É

Achieves low NOx and SO2 emissions

Ò A second CFB can be used for the

pyrolysis reactor.

Ò Loop seals fluidized by steam pass

ash from combustor to pyrolyzer and spent shale from pyrolyzer to

• combustor. Reference: He et al.

(1991).

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STEPS FOR PROCESS INTEGRATION AND OPTIMIZATION

1.

Plant-wide process model

1.

Heat and mass balances

2.

Extract stream data

1.

Heat loads, heat capacities, supply and target temperatures

3.

Determine energy targets and pinch temperatures

4.

Design heat exchanger network

5.

Process change, design evolution

6.

Design evaluations

Reference: Kemp, I. (2007) Pinch Analysis and Process Integration 2nd Ed, Elsevier Ltd. UK.

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PLANT-WIDE PROCESS MODEL

Ò The plant is divided into 6 blocks using Aspen Plus hierarchy blocks Ò The current model does not include oil upgrading or sulphur and ammonia

recovery

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Dry Cooling Power Generation Oil Recovery Shale Processing Gas Treatment Water Treatment

HIERARCHY

COOLING

HIERARCHY

FUELGAS

HIERARCHY

OILRCVRY

HIERARCHY

POWERGEN

HIERARCHY

SHALPROC

HIERARCHY

WETWATR FLAREGAS FUELGAS1 VAPOUR HEAVYOIL SOURH2O1 NAPHTHA OFFGAS1 LTGASOIL CW400 ST300 POWER W CW600 OILSHALE PRI-AIR SEC-AIR FLD-AIR CON-AIR STACKGAS WETASH RAWWATR SWSOFFG WATER1 KEROGEN MINERALS FREE-H2O FEEDMIX

WET ASH TO MINE FLUE GAS TO ST ACK DIESEL & LIGHT GAS OIL TO ST ORAGE TANK NAPHT HA & KEROSENE TO ST ORAGE TANK OIL SHALE FROM CRUSHED ST OCKPILE GAS TO FLARE POWER TO TRANSMISSION LINE GAS TO FLARE

MAKE-UP WATER

AREA 300 AREA 400 AREA 600 AREA 500 AREA 700

AMBIENT AIR

SHALE PROCESSING BLOCK

Ò The shale processing block includes models for pyrolysis, combustion, heat

recovery, gas cleaning and wetting of ash.

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COMBUSTR

FBC

PYROLYSR

WHB 301 OILSHALE(IN) 330 WATER2(IN) 304 HEAVYOIL(IN) 342 FUELGAS2(IN) 328 PRI-AIR(IN) 340 SEC-AIR(IN) 341 FLD-AIR(IN) CON-AIR(IN) 306 VAPOUR(OUT) 334 STACKGAS(OUT) 331 WETASH(OUT) ST300 ST300(OUT) 307 308A 337 316 315 ST302 327 323 ST304 303A 317 339 329 321 ST303 308

ASHMX

QTOT 03-K01 03-K02 OSHTR PAHTR SAHTR

Spent Shale Recycled Ash Heat to power generation

Optiona l pre hea ting

GASCLEAN

Pyrolyser Combustor Waste Heat Boiler Ash Cooler Gas Cleaning Ash Moistening

PYROLYSER SUB-MODEL

Ò The pyrolyser sub-model includes stoichiometric reactors for heavy oil coking,

kerogen pyrolysis, mineral decomposition and vapour-phase cracking.

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Ò Particle attrition and dust entrainment

are included.

303 303A(IN) 315 315(IN) 304 304(IN) 307 307(OUT) 306 306(OUT) 305 305A 305B 305C 305D 305E 305G 305F 03-COKE 03-PYR1 03-PYR2 03-SEP1 03-CRAK1

SCREEN

SIZE5 DUPMIX 03-MIX1

Heavy oil coking Kerogen pyrolysis Mineral decomposition and particle attrition Vapour-phase cracking Dust entrainment Spent shale to CFB combustor Pyrolysis Vapour to Oil Recovery Oil Shale Recycled ash from combustor Recycled Heavy Oil

Vapour phase cracking Heavy oil coking Kerogen pyrolysis Mineral decomposition

CFB COMBUSTOR SUB-MODEL

Ò The CFB combustor sub-model includes dense bed, dilute phase freeboard, cyclone

and external cooler.

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HIERARCHY

RECCYCL 307 307(IN) 342 342(IN) 308 308A(IN) 309 309A(IN) 337 337(OUT) 316 316(OUT) 315 315(OUT) ST302 ST302(OUT) 310 311 307FINE 307COARS 308B 312 308A

SCREEN

03-PSDSP 03-FREEB 03-FLDBD FLDBDSPL

HEATER

RCOOLR

Ash to pyrolyser Flue Gas to Heat Recovery Heat to Power Generation Ash to Cooler Primary air from fan Secondary air from fan Spent shale from pyrolyser Fuel Gas Combustor dilute phase Combustor dense phase Combustor external cooler and seal Combustor cyclone

Char combustion Mineral oxidation Mineral decomposition Sulphur capture

POWER GENERATION BLOCK

Ò The power generation block includes a cascade of back-pressure power

turbines.

Ò Steam is expanded to sub-atmospheric pressure then condensed against

dry cooler.

Ò Boiler feed water is preheated with drawn off IP/LP steam Ò Self-contained and highly optimized

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BOILERS ST300 ST300(IN) WOUT POWER(OUT) CWPOWGEN CW600(OUT) TOECO TORH2 TORH1 FROMSH3 FROMRH2 S8A W1 S22 613A 613-2 613-2A W3 623 624 613-3 613-3A W4 625 613-4 614 614A W5 614-2 614-2A W6 614-3 614-3A W7 614-4 W8 S15 S16 635Z 635 636 634 634Z 633 633Z 618C 632 619 620A 620B S30 629 617 631 HP1 S1 IP1 IP2 S2 S3 IP3 S4 LP1 S5 LP2 S6 LP3 S7 LP4 CONDENSE FWH1 V1 M1 FWH2 M2 FWH3 M3 FWH4 P2 FWH5 M4 FWH6

W

TOTWRK CWP S620 DEAERATE IP4 M5 V5 W4A

Feedwater heaters Power turbines Condenser Economiser Evaporator Superheaters Reheaters Feedwater heaters Deaerator

MODEL COMPONENTS FOR GREEN RIVER OIL SHALE

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Stream Substream MIXED Substream CISOLID Pure Components Pseudo- components

Aspen Databank INORGANICS User-Defined Components

Kerogen Char H2O Free Water FeCO3 Siderite NaAlSi2O6•H2O Analcite CaO Calcium Oxide SiO2 Quartz CaMg(CO3)2 Dolomite

KAl2(Si3Al)O10(OH)2

Illite Fe2O3 Hematite NaAlSi3O8 Albite CaCO3 Calcite FeS2 Pyrite Al2O3 Corundum KAlSi3O8 K-Feldspar Fe3O4 Magnetite Fe0.875S Pyrrhotite NaAlO2 Sodium Aluminate NaAlSi2O6 Dehydrated Analcite MgO Magnesium Oxide FeS Troilite C5 – 150oC Light Naphtha 150oC – 205oC Heavy Naphtha 205oC – 260oC Kerosene 260oC – 315oC Light Gas Oil 315oC – 425oC Heavy Gas Oil 425oC – 600oC Vacuum Gas Oil 600oC+ Residuum H2O H2 CH4 N2 C2H4 O2 C2H6 Ar C3H6 CO2 C3H8 CO C4H8 H2S C4H10 NH3 SO2

Solids sub-stream is divided into 13 particle size intervals

PROPERTIES OF USER-DEFINED COMPONENTS

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[ ] [ ]

max min 4 5 3 4 2 3 2 1

K where K kJ/kmol T T T T c T c T c T c c Cp ≤ ≤ + + + + = ⋅ Kerogen n Cha har Fr FreeH2O Formula

CH1.5N0.025O0.05S0.005 CH0.42N0.056O0.02S0.008 H2O

Molecular weight, kg/kmol 14.833 13.795 18.015

Gross heat of combustion kJ/kg 39549 34042

• Standard heat of formation kJ/kg
• 1489.7

1115.9

• 15000

Standard heat of formation kJ/kmol

• 22097

15394

• 285929

Heat capacity

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 6.487·10-7 c5 Tmin, K 273 273 273 Tmax, K 750 1000 623

PYROLYSER STOICHIOMETRY (1)

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Reactant nt Reaction E n Equation n Extent nt Free water FreeH2O à H2O 1.0 Analcite NaAlSi2O6·H2O à NaAlSi2O6 + H2O 1.0 Dawsonite NaAlCO3(OH)2 à NaAlO2 + CO2 + H2O 0.5 Pyrite 0.875FeS2 + 0.75H2 à Fe0.875S + 0.75H2S 0.46 Siderite 3FeCO3 à Fe3O4 + CO + 2CO2 0.3 Pyrolyser reactors include reactions for oil shale drying and mineral decomposition

PYROLYSER STOICHIOMETRY (2)

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Oil = {l-naphtha, h-naphtha, kerosene, LGO, HGO, VGO, residuum} Gas = {H2, H2O, H2S, CO, CO2, CH4, C2H4, C2H6, C3H6, C3H8, C4H8, C4H10} Pyrolyser reactors also include reactions for kerogen pyrolysis, vapour phase cracking and heavy oil coking. Reaction n Stoichi hiome metry Kerogen pyrolysis Kerogen à gas + oil + char Singleton et al. (1986) Vapour phase cracking Oil à gas + lighter oil + coke Bistell et al. (1985) Heavy oil coking Oil à H2 +CH4 + coke Braun et al. (1992)

COMBUSTOR STOICHIOMETRY (1)

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Reactant nt Reaction E n Equation n Extent nt Char CHAR + 1.103O2 à CO2 + 0.21H2O + 0.28N2 + 0.008SO2 0.9 Magnetite 2Fe3O4 + 0.5O2 à 3Fe2O3 1.0 Pyrite 2FeS2 + 5.5O2 à Fe2O3 + 4SO2 1.0 Pyrrhotite 2Fe0.875S + 3.3125O2 à 0.875Fe2O3 + 2SO2 1.0 Siderite 3FeCO3 + 0.75 O2 à 1.5 Fe2O3 + 3CO2 1.0 Illite K(Al2)(Si3Al)O10(OH)2 à KAlSi3O8 + Al2O3 + H2O 1.0 Dolomite CaMg(CO3)2 à CaCO3 + MgO + CO2 0.5 Calcite CaCO3 à CaO + CO2 0.15 Anhydrite CaO + SO2 + 0.5O2 à CaSO4 1.0 Combustor reactor models include reactions for char combustion, mineral

• xidation and decomposition and sulphur capture.

COMBUSTOR STOICHIOMETRY (2)

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Reactant nt Reaction E n Equation n Extent nt Hydrogen H2 + 0.5O2 à H2O 1 Methane CH4 + 2O2 à CO2 + 2H2O 1 Ethane C2H6 + 3.5O2 à 2CO2 + 3H2O 1 Ethylene C2H4 + 3O2 à 2CO2 + 2H2O 1 Propane C3H8+ 5O2 à 3CO2 + 4H2O 1 Propylene C3H6 + 4.5O2 à 3CO2 + 3H2O 1 Butane C4H10 + 6.5O2 à 4CO2 + 5H2O 1 Butene C4H8 + 6O2 à 4CO2 + 4H2O 1 Ammonia 4NH3 + 3O2 à 2N2 + 6H2O 1 Carbon monoxide CO + 0.5O2 à CO2 1 Hydrogen sulphide H2S + 1.5O2 à SO2 + H2O 1 Combustor reactors also include reactions for combustion of fuel gas components.

BASE CASE

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Parame meter Valu lue Oil shale feed rate 250 t/h Feed free moisture 1.1 wt% Feed MFA oil yield 10.4 wt% (27 gal/ton) Ambient conditions 11oC, 82.1 kPa Pyrolyser temperature 500oC Combustor exit conditions 800oC, 6 vol% O2

Ò No oil shale dryer or air preheat Ò All retort gas is burned in spent shale combustor

CALIBRATION OF EXTENTS OF PYROLYSIS REACTIONS

Ò Published data from

TOSCO II (another SHC technology) is used to calibrate extent of vapour phase cracking, pyrite decomposition and carbonate decomposition

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MF MFA TO TOSCO MODE DEL (C1-C4)/C5+ ratio kg/kg 0.085 0.182 0.165 Gas composition wt% H2 CO H2S CO2 CH4 C2H4 C2H6 C3H6 C3H8 C4 3.3 5.7 8.9 41.1 17.4 2.8 10.9 4.2 4.7 1.1 1.5 3.5 5.2 33.1 11.9 8.7 8.4 11.1 5.5 11.2 2.2 7.2 5.1 27.5 10.9 7.4 9.2 8.7 6.1 14.1 Oil distillation wt% C5 – 204oC 204 – 510oC 510oC+ 11 72 14 17 60 23 12 74 14

HEAT RECOVERY AND STEAM GENERATION

Ò Data extracted from shale processing and power generation blocks are used

to construct hot and cold composite curves

Ò 83 MW of possible 104 MW can be converted to steam Ò Pinch temperature vs Delta T min Ò Plot

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WHB & FAC RC ECON EVAP SH & RH

HEAT INTEGRATION

Ò What happens if flue gas is used to preheat air?

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With air preheat No air preheat

HEAT INTEGRATION (WITH AIR PREHEAT)

Ò By preheating combustion air with flue gas, 95 MW of possible 100 MW can

be converted to steam

Ò Another option is to use hot ash to heat feed water instead of IP/LP steam.

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WHB & FAC ECON EVAP SH & RH RC

SOME OBSERVATIONS

Ò For compete combustion SHC process, preheating air or drying oil shale is only

beneficial if it improves integration or there is insufficient fuel to heat process.

Ò Green River oil shale below 25 gal/ton has insufficient char to provide all heat by

char combustion alone.

Ò The heat balance and CO2 generation is very sensitive to extent of carbonate

decomposition.

Ò Particles between 10 – 20 µm can accumulate in process if flue gas is used to dry

• il shale and dryer cyclone dust capture is higher efficiency than waste-heat-boiler.

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CONCLUSIONS

Ò Simulator such as Aspen Plus can simulate oil shale processes Ò Mineral and oil components in same model Ò Built-in unit model adequate Ò Particle size tracking to model attrition and entrainment Ò Allows user-defined components to represent unusual components such as kerogen Ò Hierarchy can be used to organize complex plant wide model Ò Green River oil shale composition, properties, reaction stoichiometry available in

literature

Ò Data for heat integration can be extracted from model

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