Highlights of CO 2 Capture. Robert Williams CMI Annual Meeting 10 February 2008

Transcription

1 Highlights of CO 2 Capture Robert Williams CMI Annual Meeting 10 February 2008

2 Systems Analysis for Synthetic Fuels Production the Major 2008 Activity of Energy Systems Analysis Group Impetus: request from National Research Council to develop detailed spreadsheet model to help Alternative Fuels Panel and other Panels of NRC s America s Energy Future study assess synthetic fuel and fossil fuel-based power systems under a carbon mitigation policy constraint Study team: Tom Kreutz Eric Larson Guangjian Liu (joined group March 2008 from Tsinghua University) Robert Williams

3 Context Seeking alternatives to oil imports and climate change mitigation are seemingly antagonistic objectives: High oil prices, abundance of domestic coal, availability of gasification/synfuel technologies have created much commercial interest in C-intensive coal synfuels Under serious C-mitigation policy GHG emission rates for transport fuels as well as electricity should be much less than at present by mid-century Our study provided a systematic comparison of 16 alternative system configurations for making synthetic diesel, jet fuel, and gasoline using commercial or near-commercial technologies to explore prospects for addressing these two challenges simultaneously by considering: CCS in synfuel energy systems Co-processing of biomass with coal in synfuel production Production of synfuels via thermochemical conversion of biomass only

4 Feedstock Assumptions Feedstock Type Delivered price, $/GJ HHV Coal Bituminous, Illinois #6 1.7 Biomass Switchgrass/mixed prairie grasses 5.0 Acronyms FTL CTL BTL CBTL RC OT V CCS Fischer-Tropsch liquids (synthetic diesel, jet fuel, gasoline) Coal to finished FTL and electricity Biomass to finished FTL and electricity Coal + biomass to finished FTL fuels and electricity FTL synthesis with recycle (RC) of unconverted syngas for maximum FTL output FTL synthesis with once through (OT) synthesis; unconverted syngas used to make coproduct power in a gas turbine/steam turbine combined cycle power plant Coproduct CO 2 is vented Coproduct CO 2 is captured and piped to underground storage site

5 Some of the 16 System Configurations Investigated CTL-RC-V CTL-RC-CCS CTL-OT-V CTL-OT-CCS BTL-RC-V BTL-RC-CCS CBTL-RC-V CBTL-RC-CCS CBTL-OT-V CBTL-OT-CCS CBTL2-OT-CCS 50,000 barrels/day of finished FTL fuels (diesel/jet and gasoline) Same coal input and same FTL outputs as CTL-RC-V Same coal input as CTL-RC-V Same coal input as CTL-RC-V, same FTL outputs as CTL-OT-V CBIR (Common Biomass Input Rate = 10 6 dry metric tonnes/yr processed) CBIR, same FTL outputs as BTL-RC-V; FTL with negative GHG emission rate CBIR, same coal input, FTL outputs as CBTL-RC-CCS CBIR, coal/biomass ratio that yields FTL with zero GHG emission rate CBIR, same coal input, FTL outputs as CBTL-OT-CCS CBIR, coal/biomass ratio that yields FTL with zero GHG emission rate CBIR, same FTL outputs as CTL-OT-CCS; FTL with GHG emission rate of crude oil products displaced The study gave focused attention to once-through polygeneration system configurations that generate electricity as a major FTL coproduct

6 Coal/Biomass Co-Processing + Once-Through FT Synthesis + CCS coal Grinding & Slurry Prep water biomass air Oxygen Plant oxygen Gasification & Quench slag Chopping & Lock hopper CO 2 Syngas Scrubber N 2 to gas turbine oxygen steam FB Gasifier & Cyclone dry ash Water Gas Shift Tar Cracking gas expander cooling gas cooling Filter Acid Gas Removal Flash CO 2 F-T Synthesis syngas Refinery H 2 Prod CO 2 raw FT product HC Recovery syncrude unconverted syngas + C 1 - C 4 FT gases CO 2 enriched methanol F-T Refining light ends 150 bar CO 2 to pipeline finished gasoline & diesel blendstocks N 2 Saturator CO 2 Removal GTCC Power Island flue gas net export electricity Flash Regenerator H 2 S + CO 2 To Claus/SCOT methanol Refrigeration Plant methanol Assumptions for FTL system options involves coprocessing coal and biomass: Separate gasifiers for coal and biomass Syngas streams are combined for downstream FT synthesis Both RC and OT systems with both CO 2 vented and CCS analyzed. Focused attention on OT systems with CCS (shown above) Presentation today focuses on systems with modest (0% - 10%) biomass inputs Tomorrow s focuses on systems with major (35% - 100%) biomass inputs

7 Major Findings Polygeneration [once-through (OT)] plants can provide FTL at much lower cost than recycle (RC) plants designed to maximize FTL output. Polygeneration plants can provide decarbonized electricity at far lower costs of GHG emissions avoided than standalone fossil fuel power plants. Coprocessing biomass with coal in polygeneration plants with CCS enables a major role for coal in providing synfuels in a C-constrained world (most discussion of this finding tomorrow). Polygeneration plants would be very competitive in economic dispatch markets for power thereby enabling replacement of existing coal power ( Big Old Dirties ) with decarbonized power.

8 Coproduct Electricity Value? 160 Cost of Electricity ($/MWh) Grid (avg) PC-V IGCC-CCS GHG Emissions Price ($/tonne CO 2eq ) Assumed value of electricity coproduct of FTL plants ( ) = average US grid price in value of 2007 US average grid GHG emission rate (636 kgco 2eq /MWh). For reference, generation costs are shown for: PC-V (pulverized coal supercritical steam-electric plant with CO 2 vented) IGCC-CCS (coal integrated gasifier combined cycle plant with CCS).

9 OT Options Outperform RC Options Economically Break Even Crude Oil Price ($/barrel) 110 CTL-RC-V CTL-RC-CCS 100 CTL-OT-V CTL-OT-CCS GHG Emissions Price ($/tonne CO 2eq ) Definitions: GHGI (GHG emissions index) = FTL emissions relative to emissions for COPD when electricity is assigned rate for coal IGCC with 90% capture COPD = crude oil products displaced CI (capture index) = CO 2 captured as fraction of feedstock C not in products BECOP = break-even crude oil price FTL System (same coal input rates for all) Outputs GHGI CI CAPEX $10 3 per B/D $10 9 CTL-RC-V 50,000 B/D, 427 MW e CTL-RC-CCS 50,000 B/D, 317 MW e CTL-OT-V 36,700 B/D, 1279 MW e CTL-OT-CCS 36,700 B/D, 1075 MW e At all GHG emissions prices, BECOP ~ $16/B less for CTL-OT-V than for CTL-RC-V!

10 Why Do OT Options Outperform RC Options? OT advantage due in part to high marginal efficiency (ME) of OT power generation. Consider OT & RC plants with same FTL outputs: ME = (Δ net electric output)/(δ coal input, LHV) For both CTL-OT-V and CTL-OT-CCS MEs for OT power are ~ 10 percentage points higher than for stand-alone power via coal IGCC. High MEs arise because gas turbine exhaust in downstream combined cycle power plant offers enough high-quality waste heat to both: Superheat for power generation saturated steam recovered from FT synthesis & other upstream exotherms, and Generate additional steam for power generation. High MEs manifest by ST/GT output ratios for OT FTL ~ compared to ~ 0.6 for typical stand-alone coal IGCC plant. In RC systems, not enough high-quality waste heat is available to superheat saturated steam from synthesis for power generation. Also, incremental capital for extra power << for stand-alone power

11 When Evaluating CTL-OT Systems As Power Generators Instead of Fuel Producers: Assign to FTL products: System-wide GHG emission rates for crude oil products displaced Economic worth = refinery-gate prices of crude oil-derived products displaced Assign to electricity: GHG emissions = (total CTL-OT system-wide GHG emissions) - (GHG emissions assigned to crude oil-derived products) Cost = (total CTL-OT cost) (economic worth of FTL products)

12 Polygeneration Power (via 36,700 B/D) vs Stand-Alone Power Polygeneration system CTL-OT-V CTL-OT-CCS Incremental power (CTL-OT power - CTL-RC power), MW e Marginal efficiency of power generation via CTL-OT, % PC-V efficiency, % 41 Coal IGCC-CCS efficiency (90% capture) 33 GHG emission rate for CTL-OT power relative to NGCC-V, % GHG emission rate for CTL-OT power relative to PC-V, % Capital cost for CTL-RC system displaced, $ per B/D 102, ,000 Capital cost for incremental power, $ per kw e Capital cost for PC-V, $ per kw e 1630 Capital cost for coal IGCC-CCS, $ per kw e 2640 Generation cost for PC-V, $ per MWh 58 Generation cost for coal IGCC-CCS, $ per MWh 94 Crude oil price, $ per barrel Electric generation cost via CTL-OT, $ per MWh Cost of GHG emissions avoided, $ per tonne of CO 2eq Via shift: CTL-OT-V CTL-OT-CCS Via shift: PC-V coal IGCC-CCS - 44 Via shift: written-off coal power coal IGCC-CCS - 72

13 Costs of GHG Emissions Avoided are Much Less for FTL OT than for Stand-Alone Power Options Levelized FTL Cost ($/GJ, LHV) CTL-RC-V CTL-RC-CCS CTL-OT-V CTL-OT-CCS GHG Emissions Price ($/tonne CO 2eq ) Cost of Electricity ($/MWh) PC-V PC-CCS IGCC-V IGCC-CCS Written-off coal plants GHG Emissions Price ($/tonne CO 2eq ) Cost of GHG emissions avoided (CEA) = [(Production cost with CCS) (production cost with CO 2 vented)] /[(GHG emissions with CO 2 vented) (GHG emissions with CCS)] CEA: CTL-RC-V CTL-RC-CCS CTL-OT-V CTL-OT-CCS PC-V coal IGCC-CCS Written-off coal coal IGCC-CCS

14 Why do OT Systems Out-Perform Stand-Alone Power Systems in Reducing GHG Emissions for Power? 70 CO2 Capture Cost, $/tonne of CO 2 Captured Total Water gas shift Acid gas removal (Rectisol) Reduced gross power generation N2 compressor for NOx control CO2 compression 0 CTL-RC-CCS CTL-OT-CCS IGCC-CCS PC-CCS NGCC-CCS FTL systems produce concentrated CO 2 streams as core element of synthesis process low capture cost: For CTL-RC-CCS, capture cost ~ $7/t for CO 2 drying/compression For CTL-OT-CCS, capture cost ~ $14/t most additional cost is for N 2 compression for NO x emissions control For FTL systems using Co catalyst OT capture cost likely to be not much more than for RC (Fe catalyst assumed for displayed FTL system)

15 Coprocessing < 10% Biomass Enables Low-Cost Decarbonization of Power While Providing GHG Emission Rate No Worse Than for COPD & Gaining Early Biomass Experience Break Even Crude Oil Price ($/bbl) CTL-RC-V CTL-OT-V CBTL2-OT-CCS GHG Emissions Price ($/tonne CO 2eq ) FTL System CTL-RC-CCS CTL-OT-CCS % Bio, HHV Assumed biomass supply = 1 x 10 6 dry tonnes/year, delivered Assumed biomass price = $5/GJ (3X coal $22/t CO 2eq, CBTL2-OT-CCS becomes the least costly option among 16 FTL systems investigated Outputs GHGI CI CAPEX $10 3 per B/D $10 9 CTL-RC-V 0 50,000 B/D, 427 MW e CTL-RC-CCS 0 50,000 B/D, 317 MW e CTL-OT-V 0 36,700 B/D, 1279 MW e CTL-OT-CCS 0 36,700 B/D, 1075 MW e CBTL2-OT-CCS ,700 B/D, 1113 MW e

16 How Can Such a Modest Biomass Input (< 9%) Have Such Significant Impacts in Reducing FTL GHG Emission Rate (~ 23%) and Production Cost? For FTL systems (RC or OT), ~ ½ of C in feedstock is available as CO 2 at high partial pressure in syngas and can be captured for geological storage at low cost. Biomass derived CO 2 stored underground represents negative emissions that can be used to offset positive CO 2 emissions from coal. Credit for decarbonized electricity coproduct increases with GHG emissions price FTL cost falls with GHG emissions price. Until very high GHG emission prices are reached (~ $120/t CO 2eq ) pursuing CCS for biomass via coprocessing is preferred to CCS for stand-alone biomass FTL plants because of: Economies of scale of coal conversion, and Lower average feedstock cost via coprocessing.

17 Polygeneration Plants Offer Market Mechanism for Backing Out Big Old Dirties Market determination of which plant on power grid gets dispatched first and thus a plant s capacity factor depends only on the short run marginal cost (SRMC) for a plant the capital cost is a sunk cost that does come into play. Power plant operators will bid to provide power in economic dispatch at power prices down to minimum dispatch cost (MDC), determined by Revenues = SRMC. OT FTL systems have two revenue streams: one from power sales + one from FTL sales. Because of the FTL revenue stream, OT FTL systems are competitive with existing coal plants in economic dispatch down to extremely low crude oil prices and thus are able to replace, via market forces, existing carbon-intensive coal power with decarbonized power.

18 Economic Dispatch Competition Minimum Required Revenues for Economic Dispatch and Short Run Marginal Costs for CBTL2-OT-CCS Plant $25/t CO 2eq $ per MWh $0/t CO 2eq Cost of GHG emissions Cost of CO2 transport and storage O&M cost Biomass cost Coal cost Revenues from FTL sales Revenues from power sales MDC CP SRMC MDC CP Crude Oil Price ($ per barrel ) or SRMC MDC for CBTL2-OT-CCS = MDC for coal $0/t CO 2eq and $25/t CO 2eq and $8/barrel For $35/barrel oil, MDC for CBTL2-OT-CCS = 42% of MDC for coal $0/t CO 2eq 29% of MDC for coal $25/t CO 2eq MDC for CBTL2-OT-CCS = $0/MWh for $0/t CO 2eq and $43/barrel $25/t CO 2eq and $46/barrel SRMC

19 Proposed DoD/DoE-Sponsored CCS Early Action Initiative Urgency to carry out demo megascale integrated CCS projects to ascertain if CCS is viable as gigascale C-mitigation option to satisfaction of many stakeholders G8 Summit (Japan 2008) Agreement to sponsor 20 projects globally (up & running ~ 2016) US made commitment to sponsor 10 Do economic crisis/budget deficit concern jeopardize G8 goal (governments would probably have to pay for large fraction of incremental cost of CCS)? CEAI would make it feasible to meet goal at low cost to government by Allowing polygeneration systems to compete alongside power only systems for subsidies Synfuels produced must be in compliance with Section 526 of EISA of 2007 Specifying that winning projects are those offering least cost of GHG emissions avoided For winning projects: Government would pay incremental cost for CCS Air Force would offer 20-year procurement contracts for jet fuel Cost to government for demos is likely to be much less than for alternative CCS early action schemes