Decarbonization of Fossil Fuels for the Production of Fuels and Electricity OUTLINE OF PRESENTATION

Transcription

1 Decarbonization of Fossil Fuels for the Production of Fuels and Electricity Robert H. Williams Princeton Environmental Institute Princeton University Clean Coal Technology Roadmap Workshop s Calgary, Alberta, Canada 20 March 2003 OUTLINE OF PRESENTATION Energy policy context (esp. climate change mitigation) to motivate: Separate consideration of markets for electricity and fuels used directly Electricity + Hydrogen Economy Can atmospheric CO 2 be stabilized at ~ ppmv without abandoning fossil fuels? Issues: Is geological storage of CO 2 viable in wide applications? Can CO 2 capture/storage be realized at competitive costs? Challenges and opportunities for coal CO 2 capture/storage for electric generation on path to H 2 CO 2 capture/storage in H 2 manufacture Carbon-based coal-derived fuels in climate-constrained world? Focus on cost comparisons for decarbonization: Coal vs natural gas Electricity vs H 2 1

2 Context for Technological Transformation of Energy Supply System Radical technological change needed to transform energy system, to cope adequately with challenges posed by BAU energy futures: pollution (esp. health damages from small particles) Energy supply insecurity (overdependence on Middle East oil) Climate change from buildup of GHGs in atmosphere as a result of fossil fuel burning Climate change most daunting challenge but technologies/strategies for dealing simultaneously with all challenges desirable Fine structure of distribution of global CO 2 emissions is helpful in prioritizing activities aimed at radically transforming energy system CO 2 EMISSIONS FROM FOSSIL FUELS, BAU (IPCC s IS92a Scenario: pop 2X; GWP 12X, ) 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% Distribution of CO2 Emissions from Fossil Fuel Consumption by Activity (%) U.S World 3. IPCC s IS92a Scenario for U.S. in IPCC s IS92a Scenario for World in 2100 Other (%) Transportation (%) Electricity Generation (%) Global CO 2 emissions: Total: 6.2 GtC/y, 1997(37% coal) 20 GtC/y, 2100 (88% coal) From electricity: 1.9 GtC/y, GtC/y, 2100 From fuels used directly: 4.3 GtC/y, GtC/y, 2100 Cum emissions, : ~ 1500 GtC Primary energy use/capita up 2.0X, ( 1/3 US level in 1997) Electricity use/capita up 2.6X, ( ½ US level in 1997) Direct use of fuels/capita up 1.4X, ( ¼ of US level in 1997) 2

3 ALLOWABLE CUMULATIVE CO 2 EMISSIONS FOR ALTERNATIVE STABILIZATION TARGETS 550 ppmv Ä cum emissions relative to IS92a ~ 450 GtC, annual emissions ~ 5 GtC/y in 2100 (vs. 20 GtC/y in IS92a) 450 ppmv: Ä cum emissions relative to IS92a ~ 800 GtC, annual emissions < 3 GtC/y in 2100 (vs. 20 GtC/y in IS92a) COAL: CHALLENGE AND OPPORTUNITY Coal = main problem w/r to climate change: If only remaining fossil fuels = conventional oil, natural gas (NG), atmospheric CO 2 would stabilize at 350 ppmv Adding unconventional NG (3X as much as conventional NG) ~ 500 ppmv Unconventional oil resources also problematic (tar sands, heavy oils) Coal also creates severe air pollution problems, mining hazards Coal not likely to be abandoned because of: Its abundance (~ 2000 y supply at current use rate) Prices are low, non-volatile Can technology make coal environmentally acceptable? Gasification strategies near-zero air pollutant/ghg emissions (H 2 from coal with geological storage of CO 2 coproduct potentially lowcost solution to fuels used directly component of climate problem) Residual environmental, health, safety problems of coal mining 3

4 CO 2 CAPTURE/STORAGE FOR FOSSIL FUEL POWER GENERATION With CO 2 vented, coal IGCC faces stiff competition from coal SCS and coal UCS technologies efficiencies and costs comparable but more familiar steam technologies will often be favored by electricity providers Pre-combustion CO 2 capture for coal IGCC = preferred CO 2 capture technology for new coal plants least incremental cost Also IGCC = stepping stone to H 2 from coal for longer term: Good prospects that coal-derived H 2 with CO 2 capture/storage will be among least costly options for fueling H 2 economy In industrialized countries,promising strategy for introducing H 2 from coal will be at sites of IGCC repowering of old coal steam-electric plants Competition between coal IGCC and NGCC under climate constraint warrants close attention risk of losing coal infrastructure that will be needed later to provide H 2 from coal Coal IGCC Electricity with CO 2 Capture CO-rich raw syngas High temp. Quench + scrubber CO2-lean gases Low temp. Saturated steam H2- and CO2-rich syngas Regeneration, Claus, SCOT Lean/rich solvent H 2S physical absorption Solvent regeneration Lean/rich solvent CO 2 physical absorption H2-rich syngas CO 2 drying + compression Supercritical CO2 to storage Coal slurry O2-blown coal gasifier Heat recovery steam generator Syngas expander 95% O2 Steam turbine Turbine separation unit N2 for (NOx control) Gas turbine GHGT-6 conv. electricity, CO2 seq. ( ) 368 MW $1737/kW e, η = 34.8%, 6.4 /kwh includes cost of transporting CO km and aquifer storage 2 km underground vs 407 MW e, $1326/kW e, η = 41.8% and 4.5 /kwh w/co 2 vented 4

5 COMPARING NGCC AND COAL IGCC COSTS UNDER CLIMATE CONSTRAINT Is it cost-effective to capture/store CO 2 for NGCCs? At what natural gas price can coal IGCCs w/co 2 capture/storage compete with NGCCs? Economics of NGCC with Carbon Storage 7 Electricity Cost ( /kwh) NGCC with CO 2 capture NGCC with "Crossover point" for CO 2 storage (292 $/tonne C at 3.0 $/GJ NG) Carbon Tax ($/tonne C) Carbon tax needed to induce CO 2 storage is extremely high. NGCC with CO 2 capture is not considered further. 5

6 Economics of Coal IGCC with Carbon Storage 7.0 Electricity Cost ( /kwh) Coal IGCC with CO 2 storage Coal IGCC with Carbon Tax ($/tonne C) CO 2 storage crossover: (93 $/tonne C) Tax needed to induce CO 2 storage in coal IGCC is much lower than NGCC. But, how does coal IGCC+CO 2 storage compete with NGCC+... The Breakeven NG Price to Induce CO 2 Storage 7.0 Electricity Cost ( /kwh) Coal IGCC with CO 2 storage NGCC with Coal IGCC with CO 2 storage crossover: (93 $/tonne C, 5.9 $/GJ NG) Carbon Tax ($/tonne C) In addition to the carbon tax, the NG price must exceed ~6 $/GJ for coal IGCC+CO 2 storage to be cost competitive with NGCC + CO 2 venting 6

7 Outlook for Fossil Fuel Competition in Power Markets in Climate-Constrained World IGCC favored technology for new coal power plants in climate-constrained world For IGCC, worthwhile to capture/store CT ~ $100/tC << than required to decarbonize NGCC Still, primary energy and generation cost penalties are significant for coal IGCC w/capture/storage (~ 20% and 40%, respectively) Not urgent to decarbonize new NGCC plants (w/venting, emissions < ½ for IGCC) At CT ~ $100/tC, IGCC not competitive with NGCC/venting until P NG $6/GJ P NG =$3/GJ-$4/GJ reducing IGCC capital cost w/capture/storage 35%-20% Severe climate policy constraint shift to NG at expense of coal in power markets Potential loss of coal energy infrastructure deleterious long-term impact because of coal s promise in serving H 2 markets H 2 IN CLIMATE-CONSTRAINED WORLD: Wide interest in H 2 as energy carrier especially as transport fuel Many H 2 fuel cell bus demonstration projects World s major auto makers in race to develop H 2 fuel cell cars Small number of prototypes being produced annually Market launch targeted for In United States: Freedom Car Initiative, Freedom Fuel Initiative Huge demand-side challenges to be overcome, esp: Current high cost of fuel cell vehicles Low volumetric energy density of H 2 If H 2 can be successfully introduced as energy carrier, how will H 2 be made? If geological storage of CO 2 proves to be a viable option in wide applications, H 2 from fossil fuels based on present H 2 production technologies will be far less costly than H 2 from renewable or nuclear technologies for decades to come Currently, H 2 derived mainly from natural gas via steam-reforming of natural gas (but extensive experience in making H 2 using modern coal gasifiers in China s NH 3 manufacturing industry) What is prospective cost competition between: H 2 from coal via gasification H 2 from natural gas via steam reforming 7

8 H 2 Production from Coal with CO 2 Capture CO-rich raw syngas Coal slurry High temp. Quench + scrubber O2-blown coal gasifier CO2-lean gases Low temp. Saturated steam H2- and CO2-rich syngas Heat recovery steam generator Regeneration, Claus, SCOT Lean/rich solvent H 2S physical absorption Solvent regeneration Lean/rich solvent CO 2 physical absorption Pressure swing adsorption Purge gas CO 2 drying + compression High purity H2 product Supercritical CO2 to storage 95% O2 Steam turbine Turbine separation unit N2 for (NOx control) Gas turbine GHGT-6 conv. hydrogen, CO2 seq. ( ) 1200 MW th H $7.5/GJ, η = 68.0% includes cost of transporting CO km and aquifer storage 2 km underground vs 1200 MW $6.2/GJ, η = 71.6% w/co 2 vented Economics of H 2 from Coal with Carbon Storage 9.0 Hydrogen Cost ($/GJ, HHV) H 2 from NG with CO 2 storage H 2 from coal with H 2 from NG with CO 2 storage crossover (38 $/tonne C, 4.1 $/GJ NG, 4.6 /kwh NGCC) H 2 from coal with CO 2 storage Carbon Tax ($/tonne C) Both the carbon tax and breakeven NG price needed to induce coal H 2 with CO 2 storage are much lower than those for electric power. Industrial H 2 from coal might be the earliest CO 2 storage opportunity. 8

9 Breakdown of Incremental Capital Cost for CO 2 Capture Coal IGCC ( $/kw e ) 3% Other H 2 from Coal ( $/kw th H 2 HHV) 24% CO 2 drying, compression s, heat exchangers 37% Selexol CO 2 absorption, and stripping CO 2 drying, compression 36% 100% Incremental cost for CO 2 capture is less for hydrogen than electricity because much of the equipment is already needed for a H 2 plant. Capture (and Co-store) H 2 S with CO 2 CO-rich raw syngas Coal slurry High temp. Quench + scrubber O2-blown coal gasifier CO2-lean gases Low temp. Saturated steam H2- and CO2-rich syngas Heat recovery steam generator Regeneration, Claus, SCOT Lean/rich solvent H 2 S physical absorption Solvent regeneration Lean/rich solvent CO 2 physical absorption Pressure swing adsorption Purge gas CO 2 drying + compression High purity H2 product Supercritical CO2 to storage 95% O2 Steam turbine Turbine separation unit N2 for (NOx control) Gas turbine GHGT-6 conv. hydrogen, CO2 seq. ( a) Remove the traditional acid gas recovery (AGR) unit. 9

10 Conventional H 2 Production with CO 2 /H 2 S Capture Solvent regeneration Quench + scrubber High temp. Low temp. H2- and CO2-rich syngas Lean/rich solvent CO 2/H 2S physical absorption CO 2 /H 2 S drying and compression CO2 + H2S to storage CO-rich raw syngas Coal slurry O2-blown coal gasifier CO2-lean gases Saturated steam Heat recovery steam generator Pressure swing adsorption Purge gas High purity H2 product 95% O2 Turbine separation unit N2 for (NOx control) Steam turbine Gas turbine GHGT-6 conv. hydrogen, co-seq. ( ).FH10 Resulting system is simpler and cheaper. Economics of H 2 from Coal with H 2 S-CO 2 Co-Storage Hydrogen Cost ($/GJ, HHV) H 2 from NG with CO 2 storage Co-storage crossover (19 $/tonne C, 3.9 $/GJ NG, 4.3 /kwh NGCC) H 2 from coal with H 2 from NG with H 2 from coal with H 2S-CO 2 co-storage Carbon Tax ($/tonne C) H 2 S-CO 2 co-storage further reduces both the crossover carbon tax and breakeven NG price. 10

11 Breakeven NG Prices vs. Carbon Tax Breakeven NG Price ($/GJ HHV) Coal IGCC: H 2 from Coal: CO 2 storage H 2S-CO 2 co-storage CO 2 storage H 2S-CO 2 co-storage Carbon Tax ($/tonne C) Breakeven NG prices for coal H 2 mirror those for IGCC (but are lower). Outlook for Fossil Fuel Competition in Making H 2 in Climate-Constrained World As for electricity, needed (CT) coal H2 << (CT) NG H2 for inducing capture/storage Unlike electricity, good prospects that coal H 2 w/capture/storage competitive with NG H 2 w/venting for P NG ~ $3.5-$4.0/GJ Making H 2 is outstanding (long-term) opportunity for coal in energy markets Transition to coal H 2 difficult because of market threat to coal power industry from NG in early years of transition to low C energy economy 11

12 WHILE WAITING FOR A H 2 ECONOMY H 2 won t be widely used as energy carrier for at least years But H 2 use in chemical/refining industries ~ 1% of global primary energy Gasification-based H 2 production at refineries/tar sands conversion plants (via gasification of coke, pitch) and NH 3 plants might be exploited as low-cost source of CO 2 for megascale demonstration projects of CO 2 storage in various geological media Such demonstration projects might be considered for China as well as for industrialized countries in light of China s deep involvement with NH 3 production via gasification [China produces 5 million t/y of H 2 (98% at NH 3 plants), compared to the world production rate of 40 million t/y] Plant-Gate CO 2 Costs with CO 2 Capture Plant type Plant output CO 2 disposal rate Plant-gate CO 2 cost ($/t) NGCC (store) 311 MW e 118 t/h 58 Coal UCS (store) 367 MW e 335 t/h 33 NG H 2 (store) 1000 MW H2 204 t/h 24 CGCC (store) 379 MW e 301 t/h 15 CGCC (co-store) 379 MW e 301 t/h 11 Coal H 2 (store) 1210 MW H2 549 t/h 5.6 Coal H 2 (co-store) 1210 MW H2 549 t/h

13 3 rd Energy Carrier for Climate-Constrained World? Though promising as energy carrier for urban areas, w/o H 2 storage technology breakthrough, H 2 too costly for low energy use density (rural) regions also need new liquid C-based fuel Fossil-fuel-derived C-based energy carrier OK even under severe climate constraint ( ppmv CO 2 stablization goal) because: Long-term goal is low not zero CO 2 emissions Areas characterized by low energy use densities account for very small fraction of total use of energy by humans High H/C ratio designer fuels (FT-liquids, DME) derived from coal via polygeneration would be suitable for climate-constrained and air-quality constrained world Coal polygeneration general scheme coal H 2O Gasification and clean up air ASU 0.85 CO CO H 2 oxygen CO CO + H 2 O = H 2 + CO 2 Water Gas Shift Synthesis H Separation 2 Carbonylation methanol Separation Gas Turbine CC Acetic acid Methanol DME F-T liquids Town gas Electricity O 2 enhanced resource recovery or aquifer sequestration CO 2 CO 2 As in H 2 case, producing high H/C ratio fuels (e.g., H/C = 3 for DME) from coal (H/C = 0.8) relatively pure CO 2 coproduct and low cost CO 2 capture/storage. Note: : Consider using in compression-ignited ignited ICEVs DME from coal + underground storage of CO 2 ~ 1/3 less lifecycle CO 2 emissions than petroleum-derived gasoline used in spark-ignited ICEVs 13

14 CAPITAL-SAVINGS VIA POLYGENERATION F u e ls E le c tric ity C h e m ic a ls 0 H o u rs p e r Ye a r P olygeneration Figure 1 ( ).fh10 Capital cost savings via polygeneration two ways: Greater utilization of capital-intensive intensive system components Once-through s for fuels/chemicals production GASIFICATION ACTIVITY WORLDWIDE Gasification technology for making chemicals in market by 1970 Cool Water demonstration of coal IGCC power, GW th cum syngas capacity: By activity: 24 GW th chemicals 23 GW th power 14 GW th synfuels By region: 19 GW th W Europe 18 GW th Asia/Australia 10 GW th N America 10 GW th Africa/ME 3 GW th E Europe/FSU 1 GW th Latin America By feedstock: 27 GW th pet residuals 27 GW th coal 6 GW th NG 1 GW th biomass Source: SFA Pacific, Gasification Worldwide Use and Acceptance, prepared for the US DOE, January 2000 New syngas capacity being 3 GW th /y Most power at refineries via polygeneration Coal power growth constrained by NGCC competition 14

15 CONCLUSIONS Coal is main climate challenge posed by fossil fuels Promising long-term future for coal if Coal is gasified rather than burned H 2 can be successfully established as energy carrier (daunting demand-side challenges) Geological storage of CO 2 proves to be viable at large scales Daunting near-term challenges to decarbonized coal IGCC from NGCC competition some combination of higher NG prices, IGCC technological improvement, and subsidies needed to establish gasification in market via IGCC on path to H 2 economy Industrial H 2 produced via gasification offers promising low cost CO 2 for megascale geological storage demo projects in near term 15