Coal-to-Liquids: Can CO 2 emissions be significantly reduced?

Transcription

1 Coal-to-Liquids: Can CO 2 emissions be significantly reduced? Harko Mulder Sasol Technology (Pty) Ltd

2 Outline Sasol Overview Coal-to-Liquids (CTL) flow scheme Why does CTL have this CO 2 footprint? CTL CO 2 Reduction Opportunities: Process Efficiencies Improvements Carbon Free Utility Generation Alternative H 2 Production CCS Conclusions

3 Sasol Overview

4 Sasol (1) Founded in 1950 to commercialise coal-to-liquids technology in South Africa Listed on NYSE and JSE 2008 Financial highlights: Turnover R130 billion ($ 17,8 billion) Operating Profit R33billion ($4.6 billion) Market Cap R312billion ($39.9 billion) employees worldwide (Africa, USA, Europe, Middle East, India/Asia)

5 Sasol (2) Largest producer of synthetic liquid fuels: CTL: bbl/day GTL: bbl/day Growth Drivers: Expanding through our proprietary GTL and CTL technologies Growing our chemical portfolio Exploiting complementary upstream hydrocarbon opportunities

6 Sasol BUT... Total CO 2 equivalent emissions ~ 73 million t/a (2008) ~ 1 t CO 2 / bbl product The Culprit? Coal-to-Liquids Thermal Efficiency: 38-42% (depending on coal and flow sheet)

7 CTL Flow scheme

8 What is CTL? Air ASU Reforming O 2 Steam CO 2 Gasification and Gas Conditioning CO 2 Fischer-Tropsch Coal Steam Gasification Water Gas Shift Rectisol Fischer Tropsch Benfield Cold Separation Ash CO 2 Refinery Products Air Coal Utilities Steam Electricity Ash ASU = Air Separation Unit

9 Why does CTL have this CO 2 footprint? Simplistic CTL Gasification Fischer-Tropsch Coal Carbon C H 2 O 0.67 CO CO + 2H 2 -CH 2 -+ H 2 O Products -CH H CO 2 H = -152MJ/kmol CO H = 117MJ/kmol C Coal Carbon Utilities C + O 2 CO 2 H = -394 MJ/kmol C Steam Electricity

10 Why does CTL have this CO 2 footprint? Overall reaction: C H 2 O 0.67 CO H CO CH H 2 O CO 2 0,3 C + 0,3 O 2 0,3 CO 2 Thus: 1,3 kmol C produces 0.67 kmol product and 0,63 kmol CO 2 Maximum Theoretical Carbon Efficiency = 52 % t Product t DAF Coal t CO 2 t Product = 0,6 = 3,0 Although very simplified, it demonstrates the issues: Low Carbon Efficiency due to H 2 Production, Energy needs and Process Inefficiencies

11 Typical CTL CO 2 Emissions Process CO 2 Utility CO 2

12 CTL CO 2 Reduction Opportunities

13 CTL CO 2 Reduction Opportunities 1) Process Efficiency Improvements Reduce Utility Demand 2) Carbon Free Utility Generation Hydroelectricity Solar Nuclear 3) Alternative H 2 Production Water Splitting 4) Carbon Capture and Storage Rectisol CO 2 Utility CO 2 Note: Co-feeding of hydrogen rich feeds (e.g natural gas) can reduce CO2 emissions not discussed here

14 1. Process Efficiency Improvements Higher Efficiency = more responsible use of limited resources Responsible technology choices (e.g. boiler selection) Investigate heat integration opportunities Improve selectivities Technology Pulverised Feed (PF) Boilers Supercritical PF Boilers Integrated Gasification Combined Cycle (IGCC) Thermal Efficiency (%) 35.9 (EPA) 35.4 (DOE) 38.3 (EPA) 39.8 (DOE) 41.8 (EPA) 39.2 (DOE) Limited in significant CO 2 reduction potential, but important References 1. EPA - Environmental footprints and costs of coal-based integrated gasification and combined cycle gasification and pulverised coal technologies July DOE - Power plant water usage and loss study NETL, August 2005

15 2. Carbon Free Utility Generation Typical utility requirements for an bbl/day CTL: Total 2840 MW thermal Typical steam quality required: suitable for gasification Alternative Energy Options: Hydroelectricity Solar Nuclear

16 2.1 Hydroelectricity Limited by location Inga Project: Democratic Republic of the Congo Inga I 350 MW (commissioned) Inga II MW (commissioned) Inga III MW (feasibility studies) Grand MW (being studied by WEC) Limited to electricity supply Relatively cheap electricity Inga III target = 2c/kWh Limited opportunities in typical CTL locations World Energy Council, How to make the Garand Inga Hydropower Project happen for Africa, March 2007

17 2.2 Solar Diluted energy source Sunbelt: 900 W/m 2 peak Need energy storage solution Focus limited to CSP (Concentrating Solar Power) Can supply electricity and steam But for steam must be located at CTL facility Prominent technologies for large scale: Parabolic troughs Tower Typical Efficiencies = 16% (assuming 900 W/m 2 peak) To supply typical bbl/day CTL plant with utilities, will require km 2 Interesting, but opportunistic, option. Maybe for electricity.

18 2.3 Nuclear (1) Limited to Pressurised Water Reactors 265 commercial units worldwide Commercial technologies: EPR: Areva 1600 MWe(4590 MWt) 77.6barg AP1000: Westinghouse 1117 MWe(3400 MWt) 57.6barg Can supply electricity and steam

19 2.3 Nuclear (2) Currently no major PHP (process heat plant) applications for PWR s, but technically feasible A single PWR reactor can supply all utilities for a bbl/day CTL PWR on line availability: Average US capacity factor: 91% (2007) Worldwide capacity factor: 83% Outage: days every months Outages due to refuelling (4%) and unplanned shutdowns (4-5%)

20 3. Alternative H 2 Production H 2 Requirement for bbl/day CTL ~ 120 t/hr Carbon free production via electrolytic water splitting: H 2 O H 2 + ½ O 2 H = 286 MJ / kmol H 2 Minimum Theoretical Energy Requirement for 120 t/hr = 4800 MW Need to be combined with carbon free energy source probably nuclear StatoilHydro Alkaline Electrolysers Type 5040: Capacity per unit: 485 Nm 3 /h (43 kg/h) 500 units worldwide largest installation = Nm 3 /h (2.6 t/h) ca 80% efficiency H 2 Purity: 99.9% (after guard beds: %) O 2 Purity: 99.5%

21 3. Alternative H 2 Production: Flow Sheet Impact ASU CO 2 ATR Gasification Shift Rectisol FischerTropsch Benfield/Cold Sep Utilities / H 2 via Coal MWe Utilities MWt Electricity CO 2 Steam CO 2 CO 2 CO 2 ATR Gasification Rectisol FischerTropsch Benfield/Cold Sep O 2 Utilities / H 2 via Nuclear MWe 5 PWR s MWt Electrolysis (2700) H 2 O 2 CO 2

22 4. Carbon Capture and Storage CO 2 emissions Capture Compression Transmission Injection CCS Attractiveness for CTL: Process CO 2 : 45-60% of CO 2, already captured (up to 98% CO 2 ). Utility CO 2 : 22-52% of CO 2, diluted (ca 15% CO 2 ) Potential capture technologies: Process CO 2 : e.g. Selective Rectisol (Linde, Lurgi); Selexsol (UOP) Benfield (UOP) Utility CO 2 : e.g. Linde PCC technology; Alstom s Chilled Ammonia Process; CANSOLV Amine Process; Praxair s MEA-MDEA solvent

23 4. Carbon Capture and Storage Examples DGC Weyburn EOR Project (1 2 Mt CO 2 /a) Sleipner Project 1 Mt CO 2 /a Current day volumes still relatively low compared to CTL requirements, but will probably increase CTL site selection to include CCS requirements

24 Relative Costs: CCS, Nuclear, H 2 Production X LWR Electrolysis 600 Relative Cost ** x LWR / Electrolysis 1 x LWR Rectisol & Utility CCS Rectisol CCS CCS LWR % CO 2 Avoided **: $/t CO 2 relative to Rectisol CCS

25 Conclusions

26 Conclusions (1) CO 2 footprint due to utility generation (energy needs, process inefficiencies) and H 2 production Opportunities to avoid Utility CO 2 production significantly: Improved process efficiencies limited Alternative energy for utility generation Nuclear Straight forward integration for electricity supply Integration for steam supply more challenging, but possible Main hurdle: on-line availability Hydroelectricity: Limited sites Limited to electricity supply Affordable electricity Solar: CSP most attractive solar technology Can supply electricity and steam Limited sites (especially for steam)

27 Conclusions (2) Process CO 2 can be largely avoided by H 2 production via water splitting Hurdles: Energy cost and electrolyser scale Carbon Capture and Storage More attractive option for dealing with Process CO 2

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