Coal Gasification: Edward S. Rubin Department of Engineering and Public Policy Carnegie Mellon University Pittsburgh, Pennsylvania

Transcription

1 Coal Gasification: The Technology and Its Viability as a Future Energy Source Edward S. Rubin Department of Engineering and Public Policy Carnegie Mellon University Pittsburgh, Pennsylvania Presentation to the Group Against Smog and Pollution (GASP) Pittsburgh, Pennsylvania April 6, 2006

2 Outline of Talk What is coal gasification? How does it work? Why the interest? Where does it stand? Where is it headed?

3 What is Coal? (Ill.#6) Carbon (wt%) 61.2 Hydrogen 4.20 Oxygen 6.02 Sulfur 3.25 Nitrogen 1.16 Chlorine 0.17 Ash 11.0 Moisture 13.0 Mercury (ppm,dry) 0.12 HHV (Btu/lb) 10,900 Bituminous Subbituminous (PRB) ,335

4 Coal vs. Other Fossil Fuels COAL C:H ~ 1:1 C H + H = synthetic oil + H H = synthetic gas PETROLEUM C:H ~ 1:2 C H H NATURAL GAS C:H ~ 1:4 C H H H H

5 What Is Gasification? Gasification is a process that converts carbonaceous materials, such as fossil fuels and biomass, into a mixture of mostly hydrogen and carbon monoxide (called synthesis gas, or syngas) Other gaseous species (including some potential air pollutants) also are formed; amounts depend on the fuel composition and process conditions The syngas can be burned as a fuel, or processed to produce chemicals and other fuels

6 Not a New Technology Coal gas was first used in London in 1790 for gas lights Later used for fuel gas in Europe and North America in the 19 th and early 20 th century Used to produce coal-derived transportation fuels in Germany during WWII Many different gasification processes have been proposed, employing different schemes for fuel feed, reactor design, etc. Current generation of gasifiers are much cleaner and more efficient than earlier designs

7 Gasification Basics Coal gasification is carried out at high temperature (and pressure, usually) to decompose the coal and create new products via addition of hydrogen The source of heat for these reactions is the partial oxidation (combustion) of the coal, which requires some addition of oxygen The source of hydrogen is water (H 2 O), added either as a liquid or vapor (steam) The source of oxygen is either air, or nearly-pure oxygen (supplied by an air separation unit)

8 Gasification Chemistry Gasification processes use one or more common reactions: Thermal decomposition HC + heat = H 2 + C + organics Reaction with oxygen (partial oxidation) HC + O = H 2 + CO + heat Reaction with steam (reforming) HC + H 2 O + heat = 3/2H 2 + CO Reaction with hydrogen (hydrogasification) HC + H 2 = CH 4 + heat

9 A Typical Coal Gasifier Coal %C, H, S, O, N, Cl %Ash Hydrogen H 2 O Oxygen Air or O 2 Slag Syngas (raw) % CO % H 2 % CO 2 % H 2 O % CH 4 % COS % H 2 S % HCl % NH 3 % N 2 % Ash

10 Uses of Syngas After cleanup for removal of impurities, syngas can be used for: Electric power generation Steam generation Process heat Chemicals production Liquid fuels production All of the above

11 Chemicals and Fuels from Syngas Acetic Anhydride Ethene & Propene VAM Terephthalic Acid p-xylene Acetic Acid n-butylene n-butyl Acetate Gasoline & Fuels MTBE Isobutylene Methanol SNG Formaldehyde Aniline Phosgene Acetylene MDI Lubricants & Wax Ethanol & Isobutanol CO + H 2 Hydrogen 1,4-Butanediol Ammonium Phosphate & Diammonium Phosphate Phosphoric Acid Ammonia Nitric Acid Urea Sulphuric Acid Ammonium Sulphate Ammonium Nitrate Source: Gunal-Akgol, U.Waterloo

12 Why the Current Interest? Process Considerations Offers a way to utilize low-value feedstocks or wastes (such as petroleum coke) in a variety of refinery and petrochemical processes Can produce multiple products (polygeneration) Growing interest for industrial application in the face of high natural prices in recent years

13 Worldwide Gasification Capacity Source: SFA Pacific /DOE, 2001

14 Gasification by Global Region Source: SFA Pacific /DOE, 2001

15 Gasification Applications Source: SFA Pacific /DOE, 2001

16 Primary Gasification Feedstock Source: SFA Pacific /DOE, 2001

17 Source: SFA Pacific /DOE, 2001 Gasifier Technologies

18 Pet Coke Gasification to H 2 and CO 2 for Ammonia and Urea Farmland Industries, Coffeyville, Kansas

19 Why the Current Interest? Process Considerations Offers a way to utilize low-value products or wastes (such as petroleum coke) in a variety of refinery and petrochemical processes Can produce multiple products (polygeneration) Growing interest for industrial application in the face of high natural prices in recent years Environmental Considerations Lower emission rates than current coal-fired plants Lower cost of carbon capture as climate change mitigation option

20 An Integrated Gasification Combined Cycle (IGCC) Power Plant Feeds Gasification Gas Refining End-products Oxygen Power Block Combustion Turbine Alternatives: Natural Gas Any Oil Tar/Asphalt Petroleum Coke Coal Wastes/ by-products Biomass Syngas CO 2 H 2 S Syngas GAS SEPARATION SULFUR RECOVERY Steam Turbine Syngas HRSG Electricity Hydrogen Chemicals Ammonia Fuel Cells Fischer- Tropsch Co-products: Sulfur Solids Source: Adapted from Chevron-Texaco, 2003

21 Polk Power Station IGCC Plant (Tampa Electric, 250 MW)

22 Integrated Coal Gasification Combined Cycle (IGCC) Plant Wabash River, Indiana Source: Global Energy, 2002

23 Source: EPRI, 2005

24 IGCC w/ CO 2 Capture O 2 Coal/H 2 O Gasification Cooling and Particulate removal WGS reaction CO 2 to storage Selexol for CO 2 capture Sulfur removal and recovery Combined cycle GT ST HRSG To stack

25 Industrial CO 2 Capture Systems (Source: Mitsubishi Heavy Industries) (Source: Dakota Gasification Post-Combustion Capture (gas-fired power plant, Malaysia) Pre-Combustion Capture (coal gasification plant, USA)

26 EOR at Weyburn Coal-to-Gas Plant Supplying CO 2 for Enhanced Oil Recovery (EOR) and CO 2 Sequestration Regina Weyburn SaskatchewanCanada USA SaskatchewanCanada USA North Dakota Dakota Coal Gasification Plant Sources: USDOE; NRDC CO 2 Bismarck

27 Geological Storage Projects Sleipner (Norway) Source: Statoil In Salah /Krechba (Algeria) Source: BP

28 Cost of Alternative Options 120 Cost of Electricity ($ / MWh) Wind, Biomass Coal and Gas Plants with CO 2 Capture Natural Gas Combined Cycle Coal Plants (combustion, gasification) IGCC PC CO 2 Emission Rate (kg / MWh)

29 Conclusion Growing interest in IGCC for power generation, and in gasification to produce liquids and natural gas Several proposed new power plants in the U.S. Cost and reliability are the main issues Potential for lower cost of CO 2 capture wrt PC plants DOE FutureGen project moving ahead to demonstrate and improve IGCC with CCS