Biomass Based Net CO2-negative Cogeneration – Performance

Study Using ASPEN Plus®

Kuntal Jana and Sudipta De*Department of Mechanical Engineering

Jadavpur UniversityKolkata- 700032

India

Some future options with fossil fuels………

• IGCC with carbon capture (pre-combustion or post-combustion)

Oxy-fuel combustion and CO2 capture and storage

Membranes specific for certain gases – O2, CO2, H2 etc. and integration with existing technology

Global Primary Bioenergy Supply

Global Bioenergy Electricity Generation 2000-10

Possible options ………..…..

• Biomass based power (CO2 – neutral).• Improving energy efficiency and environment

performance (Cogeneration, Gasification)• Reducing CO2 emission even more (net CO2 –

negative)

• Combining all these – possible future sustainable options with efficient and net CO2- negative power generation units.

• Challenges – technology maturity, scaling up….

Objective of the Present Work

Objective• Model development of biomass integrated

gasification combined cogeneration (BIGCC) with CO2 capture

• Simulation of the model by using ASPEN Plus®

• Defining a non-dimensional thermodynamic performance parameter- capture performance

• Finding the optimum degree of CO2 capture, based on thermodynamic performance, i.e., capture performance

Schematic of biomass integrated gasification combined cogeneration with post-combustion CO2 capture

AIR COMPRESSOR

GASIFIER

GAS COOLER

SYNGAS CLEANER

COMBUSTOR

SUPERHEATER-REHEATER

SYNGAS COMPRESSOR

GAS TURBINE

ECONOMIZER-EVAPORATOR

HEATER

PUMP

CONDENSER

Biomass

Air AshSyngas

Air

Water

STEAM TURBINE

Steam

DRIER

Gasification GT-Cycle

ST-Cycle

CO2 CAPTURE

CO2

Vent gas

CONDENSER

CO2 Product

ABSORBER

FLUE GAS COOLER

SOX REMOVAL UNIT

AMINE TREATMENT PLANT

RICH-LEAN AMINE HEAT EXCHANGER

STRIPPER

Flue gas

Flue gas (40oC)

PUMP

Make-up amine

Amine (40oC)

Rich-amine solution

Lean-amine solution

Vent-gas

Reboiler

CO2 Product

Schematic of amine based CO2 capture process

RSTOIC

DRY-FLSH

RYI ELD

RGIBBS

BIOMASS

WET-BIODRY-BI O

WATER

DECOMP

GIBS-OUT

Q-DECOMP

GASI -AIR

SEPARATE

SOLI D

SYN-GAS

COLD-SYN

GAS-SEP

H2S

AMONI A

GT-SYN

SYN-COMP

GT-COMB

COMP-SYN

AIR-COMP

GT-AIR

COMP-AI R

COMB-GAS GAS-TURB

HOT-FLUECOMP-WRK

SYN-COMW

GT-WORKW

SPRH

FLUE-OUT

RH-IN

RH-OUT

SPH-INSPH-OUT

HP-ST

ECO-EVAFLU-EXIT

LP-ST

PUMP

FEED-WTR

ECO-IN

LP-OUT

HP-WRKW

LP-WRKW

PUMP-W RK

COND

Q-COND

Q

FLU-EXHS

SYN-OUT

DRI ER

HOT-BI O

PR-WTRI N

PRW TROUT

C-SEPS3

C-ASH

B20TO-ATMP

S48

B18

PRO-HT

S5

ASPEN Plus® model of BIGCC

AB

LEANMEA

FLUEGAS

TREATGAS

RICHMEA

PUMP

POUT

HOUT

STRIP

CO2OUT

MEAOUT

Q-REB

Q

COOLER

COL-FLU

HX

COL-MEA

H2O-IN H2O-OUT

HEATER

STRIPIN

Q-MEAQ

ASPEN Plus® model of Post-combustion CO2 capture

Model development & Simulation

• Simulation Software – ASPEN Plus ® (Developed by MIT, DOE – USA)

• Biomass feed rate – 1000 kg/hr of sugarcane bagasse• Property methods:

1. Gasification and GT-power generation - Peng-Robinson equation of state with Boston Mathias alpha function (PR-BM)

2. Carbon capture process - Electrolyte Non Random Two Liquid (ELECNRTL)

3. Steam turbine power generation and process-steam generation - Steam table (STEAM TA)

Operating ParametersConfigurations Parameters Value

Reaction in gasification PressureEquivalence ratio

1atm 25% of stoichiometric air

Air compression,Syngas compression

Pressure ratioIsentropic efficiency

140.9

Combustion air Mass flow rate 25% excess of stoichiometric air

Gas cleaning Separation efficiency of solids particles 85%

Gas turbine combustor PressureHeat duty

14atm0

Gas turbine Discharge pressureIsentropic efficiency

1atm0.9

Superheater-Reheater HP stage temperatureHP stage pressure

LP stage temperatureLP stage pressure

5380C12.4MPa

5000C3.2MPa

Feed water for ST cycle TemperaturePressure

250C1atm

HP and LP Steam turbine Isentropic efficiencyLP-ST discharge pressure

0.92 0.07MPa

Lean amine solution TemperaturePressure

Amine concentration

400C1.7 bar

30% by mass

Lean loading CO2/amine (mole basis) 32%

Stripper column Calculation typeNo. of stages

Condenser typeCondenser pressure

Reboiler typeDistillate rateReflux ratio

Equilibrium20

Partial vapor10 psiaKettle

1000 Kg/hr0.10

Results

Heat consumption, Utility heat and net reboiler heat of BIGCC with post-

combustion CO2 capture

Variation of net-reboiler heat duty with carbon capture efficiency

Power output of BIGCC with post-combustion CO2 capture

NET GT-POWER (MW) LPST-POWER (MW) HPST-POWER (MW) TOTAL POWER (MW)0

0.5

1

1.5

2

2.5

REBOILER HEAT DUTY (MW)

UTILITY HEAT (MW)

NET REBOILER HEAT DUTY

(MW)

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

Variation of capture performance with carbon capture efficiency

Conclusions

• Reboiler heat duty increases sharply beyond 50% of CO2 capture

• For plants with CO2 capture, utility heat may be utilized for CO2 capture process

• For net CO2 negative plant, operational condition may be thermodynamically optimized with selection of suitable carbon capture efficiency (say, for this study 0-0.5).