Biomass Gasification Options to Maximize Resource Use Efficiency

Transcription

1 Biomass Gasification Options to Maximize Resource Use Efficiency > R.A. Knight, A. Basu, B. Bryan, V. Bush, M. Onischak (Gas Technology Institute) > 2009 TAPPI International Bioenergy & Bioproducts Conference, October Memphis, Tennessee

2 Biomass will be used, but how? >Estimates of biomass potential vary >But demand for biomass energy will certainly grow >Competition for resources will result >Key stakeholders must ensure wise utilization 5.3 to 16.0 QBtu potential* 1.3 to 2.9 QBtu is woody biomass * From Climate 2030 Blueprint, Union of Concerned Scientists Footer goes here 2

3 Follow the path of least resistance? >Policymakers will push adoption faster than the market >Path of least resistance Satisfy mandates and regulation Lowest up-front investment Lowest technical risk >Co-firing wood with coal will look attractive >But is it the best option? Footer goes here 3

4 Take a closer look >Alternative routes for woody biomass Use the resource more efficiently Provide more flexibility in energy delivery Maximize GHG mitigation benefits Footer goes here 4

5 Consider renewable natural gas Biomass CCS * option CO 2 NGCC for power NG vehicles OTF sales Gasification Cleanup & condition CH 4 synthesis RNG industrial commercial residential natural gas pipeline * Carbon capture & sequestration Footer goes here 5

6 What is gasification? >Carbonaceous fuel reacts with O 2, H 2 O, and CO 2 >Suite of reactions produce syngas: Biomass + O 2 CO 2 + H 2 O + heat Biomass + heat C, CO, H 2, H 2 O, CO 2, CH 4, etc. 2C + O 2 2 CO C + H 2 O CO + H 2 C + CO 2 2CO CO + H 2 O CO 2 + H 2 C + 2H 2 CH 4 CH 4 + 2H 2 O 3H 2 + CO 2 Footer goes here 6

7 The RNG process BIOMASS GASIFIER TAR REFORMER FILTER QUENCH WATER GAS SHIFT COMPRESSOR CO 2 ACID GAS REMOVAL (AGR) DEHYDRA TION H 2 S RNG 93.8% METHANE STEAM ASH OXYGEN STEAM CO 2 Dry the biomass with waste heat Feed dry biomass to gasifier Remove tars and dust Shift to get H 2 :CO ratio = 3:1 Compress to pipeline pressure Remove acid gases including CO 2 Convert syngas to 93.8% methane Remove remaining moisture METHANATION PLANT Footer goes here 7

8 Gasification makes CO 2 easier to recover >CO 2 capture is an integral part of the RNG process > Acid gas removal (AGR) > Some CO 2 can be recycled to gasifier to assist fluidization > Remainder can be compressed and sequestered > 90%+ CO 2 from process is much easier to capture than 10% CO 2 from boiler flue gas Footer goes here 8

9 Useable products >Pipeline-quality renewable natural gas Fungible product >Steam Waste heat boiler(s) to raise steam for the gasifier, shift reactor, glycol stripping, etc. Excess HP steam available for on-site power generation >Waste heat recovery Biomass drying Component RNG CH4, mol% N CO CO 0.01 H HHV, Btu/scf 952 LHV, Btu/scf 862 Footer goes here 9

10 Baseline RNG plant 890 ton CO 2 BIOMASS 1,600 tons 50% moisture 12,597 MMBtu WOOD DRYING a GASIFI- CATION b METHAN -ATION c RNG d 1,073 kscf 9,249 MMBtu 73.4% efficiency 2,100 MMBtu 331 ton O MWh a Wood is dried to 20% moisture b includes syngas cleanup and water gas shift c Includes compression and acid gas removal d 93.8% methane, 952/862 Btu/scf (HHV/LHV) at 775 psig Footer goes here 10

11 Integration with existing mill beneficial >Integration with mill decreases life-cycle cost Oxygen Thermal integration Infrastructure Utilities Expertise Footer goes here 11

12 The co-firing case to compare 1,484 ton CO 2 BIOMASS 1,600 tons 50% moisture 12,597 MMBtu COAL-FIRED POWER PLANT Efficiency a 26.0% POWER 960 MWh 3,275 MMBtu e Biomass-to-energy 26.0% efficiency lb CO 2 -eq/mmbtu output 906 a Based on Mann & Spath, Clean Prod Processes 3 (2001) % substitution of wood for Illinois #6 coal on HHV basis Efficiency represents wood portion only Footer goes here 12

13 Pros and cons of co-firing >Co-firing reduces GHG impact by 31.5% a >Capital investment is low >But CO 2 capture is difficult >And biomass use efficiency is low a Compared to 100% power from coal plus landfilling/mulching of wood waste, as cited in Mann & Spath, Clean Prod Processes 3 (2001). Footer goes here 13

14 Analyzed four RNG cases 1. RNG baseline plant NGCC (standalone) 2. RNG baseline plant pipeline combustion (standalone) 3. RNG baseline plant NGCC (integrated with mill) 4. RNG baseline plant pipeline combustion (integrated with mill) Footer goes here 14

15 RNG case 1: standalone w/ngcc 890 ton CO ton CO 2 BIOMASS 1,600 tons 50% moisture 12,597 MMBtu RNG PLANT Efficiency 73.4% RNG 1.2 MWh 50 MW NGCC a Efficiency 50.0% POWER 1,254 MWh 4,279 MMBtu e 331 tons O 2 2,100 MMBtu 100 MWh ASU Biomass-to-energy efficiency 34.0% lb CO 2 -eq/mmbtu output b 694 (278) a Gas Turbine World 2009 Handbook, GE Aero LM2500+G4PC b Value in parentheses is for sequestration of CO 2 from AGR unit in RNG plant Footer goes here 15

16 RNG case 2: standalone to pipeline 1,004 ton CO ton CO 2 BIOMASS 1,600 tons 50% moisture 12,597 MMBtu RNG PLANT Efficiency a 52.3% tons O 2 MMBtu ASU 100 MWh RNG 765 kscf 6,594 MMBtu 1.2 MWh GT b 875 MMBtu NG FIRING Efficiency 82.0% 56 ton CO 2 HEAT 5,407 MMBtu Biomass-to-energy efficiency 42.9% lb CO 2 -eq/mmbtu output c 549 (220) a Part of product is burned for biomass drying b Gas Turbine World 2009 Handbook, Solar Mercury MW, 39.0% LHV efficiency c Value in parentheses is for sequestration of CO 2 from AGR unit in RNG plant Footer goes here 16

17 RNG case 3: integrated w/ngcc 890 ton CO ton CO 2 BIOMASS 1,600 tons 50% moisture 12,597 MMBtu RNG PLANT Efficiency 73.4% RNG 1.2 MWh 50 MW NGCC a Efficiency 50.0% POWER 1,254 MWh 4,279 MMBtu e 331 tons O 2 from mill 2,100 MMBtu 675 MMBtu to mill 100 MWh to mill Biomass-to-energy efficiency 39.3% lb CO 2 -eq/mmbtu output b 599 (276) a Gas Turbine World 2009 Handbook, GE Aero LM2500+G4PC b Value in parentheses is for sequestration of CO 2 from AGR unit in RNG plant Footer goes here 17

18 RNG case 4: integrated to pipeline 890 ton CO ton CO 2 BIOMASS 1,600 tons 50% moisture 12,597 MMBtu RNG PLANT Efficiency 73.4% RNG 1,073 kscf 9,249 MMBtu NG FIRING Efficiency 82.0% HEAT 7,584 MMBtu 2,100 MMBtu from mill 331 tons O 2 from mill 1.2 MWh from mill Biomass-to-energy efficiency a 60.1% lb CO 2 -eq/mmbtu output b,c 422 (187) a After deducting power purchase from the mill b Value in parentheses is for sequestration of CO 2 from AGR unit in RNG plant c Includes CO 2 from purchased power to satisfy oxygen demand Footer goes here 18

19 Compare LHV efficiency >RNG route to power is 31% to 55% more efficient than cofiring >RNG to pipeline gas is 65% to 131% more efficient Integrated RNG to pipeline Integrated RNG to power Standalone RNG to pipelline Standalone RNG to power Co-firing wood with coal LHV efficiency, % Footer goes here 19

20 Compare GHG emissions Emissions source CASE 1A Integrated RNG to pipeline CASE 2A Integrated RNG to power CASE 3A Standalone RNG to pipeline CASE 4A Standalone RNG to power CASE 5 Co firing wood with coal CASE 6 No biomass energy a GHG to atmosphere, lb CO 2 eq/million Btu Wood dryer 42 RNG plant Power generation Combustion Bio decomposition 652 TOTAL ,323 TOTAL with CCS b ,323 a Equivalent power generated from coal only b Carbon capture & sequestration from AGR section of RNG plant Footer goes here 20

21 GHG side-by-side comparison EXCLUDE CO 2 capture from RNG plant INCLUDE CO 2 capture from RNG plant Integrated RNG to pipeline Integrated RNG to pipeline Integrated RNG to power Integrated RNG to power Standalone RNG to pipelline Standalone RNG to power Standalone RNG to pipelline Standalone RNG to power Co-firing wood with coal Co-firing wood with coal No biomass energy ,000 1,500 lb CO 2 -eq per MMBtu usable energy Decomposition Dryer RNG plant Power generation Combustion No biomass energy ,0 1,2 1, lb CO 2 -eq per MMBtu usable energy Decomposition Dryer RNG plant Power generation Combustion Footer goes here 21

22 Conclusions >Converting biomass to renewable natural gas as a way of using wood resources offers some attractive features High flexibility from a fungible product (pipeline gas) High efficiency to increase the usable energy output per ton of biomass An easier path to CO 2 capture and sequestration The resource will go farther THANK YOU! Footer goes here 22