Pre-Combustion Technology for Coal-fired Power Plants

Transcription

1 Pre-Combustion Technology for Coal-fired Power Plants Thomas F. Edgar University of Texas-Austin IEAGHG International CCS Summer School July,

2 Introduction 2

3 CO 2 Absorption/Stripping of Power Plant Flue Gas Use 30% of power plant output Flue Gas With 90% CO 2 Removal Absorber Stripper LP Steam CO2 for Transport & Storage Flue Gas In Rich Solvent Lean Solvent 3

4 The Basic Chemistry of Gasification For example: C x H y + H 2 O + O 2 ah 2 + xco 4 CH + 2 H 2 O + O 2 4 H CO (Hydrocarbon) (Water) (Oxygen) (Hydrogen) (Carbon Monoxide) Water Shift Reaction: CO + H 2 O => CO 2 + H 2 Source: GE 4

5 Combustion vs. Gasification Combustion SO 2 is scrubbed out of stack gas reacted with limestone to form gypsum NO x controlled with low NO x burners and selective catalytic reduction (SCR) Fly ash removed via ESP or bag filters Hg can be removed by contacting flue gas with activated carbon Gasification H 2 S removed from syngas and converted to solid sulfur or sulfuric acid (Claus Process) NH 3 washes out of gas with water, thermal NO x controlled by diluent injection, optional SCR for deeper NO x removal Ash converted to inert glassy slag >90% of Hg removed by passing high pressure syngas thru activated carbon bed 5

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7 FutureGen Plant Schematic Syngas H 2 7

8 Coal Gasification Emissions Sulfur in coal reduced to H 2 S Elemental sulfur is recovered salable product 99.4% removal efficiencies, no sludge Nitrogen in fuel is converted to N 2, NH 3, and small amounts of HCN Metals either contained in glasslike slag or water stream 10x fewer air emissions 15-20% less CO 2 due to increased efficiencies 8

9 IGCC vs. Conventional Pulverized Coal Combustion (PCC) 20-50% lower water usage, compared to PCC CO 2 under pressure takes less energy to remove than from PCC flue gas (Gas volume is <1% of flue gas from same MW size PCC) 9

10 IGCC with CO 2 Capture 1 Fuel is gasified and a synthesis gas is produced. The gas primarily consists of CO, H 2, and H 2 O. Source: VATTENFALL 10

11 IGCC with CO 2 Capture 2 The synthesis gas is cleaned from residuals. Source: VATTENFALL 11

12 IGCC with CO 2 Capture 3 The CO and H 2 O are converted in a shift reactor to CO 2 and H 2. Source: VATTENFALL 12

13 IGCC with CO 2 Capture 4 The gas is cleaned from sulfur after the shift reactor. Source: VATTENFALL 13

14 IGCC with CO 2 Capture 5 Carbon dioxide is separated from the synthesis gas in an absorption process. The carbon dioxide is transported to a storage site. The remaining gas (mainly hydrogen) is combusted. Source: VATTENFALL 14

15 1st Generation Gasifiers 1. TYPE OF BED 2. OPERATING PRESSURE 3. SLAGGING, NON-SLAGGING LURGI (FIXED BED, HIGH P, NON-SLAGGING) KOPPERS-TOTZEK (ENTRAINED BED, LOW P, SLAGGING) WELLMAN-GALUSHA (FIXED, LOW P, NON-SLAGGING) WINKLER (FLUIDIZED, LOW P, NON-SLAGGING) 15

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17 Kellog Brown and Root (KBR) 17

18 Current Gasifier Types Manufacturer Gasifier type Application ConocoPhillips General Electric Energy (GE) Kellog Brown and Root (KBR) Mitsubishi Heavy Industry (MHI) Shell Coal- water slurry feed, Oxygen blown, refractory lined gasifier Coal-water slurry feed, O 2 blown, refractory lined gasifier dry feed, air blown transport reactor dry feed, air blown dry feed, coal is crushed, dried and fed into gasifier, oxygen blown, waterwall in gasifier wide range of coal bituminous coal, petcoke or blend of pet coke with low rank coal low rank coal low rank coal wide variety of feedstock 18

19 IGCC Plants in the US The Tampa Electric IGCC Project Mulberry, Florida, 1996 Using: GE Energy Gasification Output: 250 MWe The Wabash River IGCC Project West Terre Haute, Indiana, 1995 Using: The ConocoPhillips E-Gas Gasification process Output: 262 MWe 19

20 Implementing New Technologies Advanced Gasification Transport Gasifier in oxygen-blown mode Oxygen Separation Advanced ion transport membranes Hydrogen Production Membrane separation from CO 2 Gas Cleanup Remove sulfur, mercury, chlorides, ammonia Hydrogen Turbines Fuel Cells 20

21 Theoretical Limit Ceramic Vanes and Blades Ceramic Vanes Precooled Air Conventional Cooling IGCC station performance 21

22 Efficient Pollutant Removal Boiler Carbon Injection WESP Pre-Combustion PM, Hg, Su SCR ESP/ FF FF FGD CO 2 IGCC Gasification cleans the syngas before combustion High pressure & low volume provide favorable economics for pollutant removal IGCC offers increased fuel diversity, reduced emissions, and increased siting & permitting flexibility Pulverized coal Pollutants are removed after the coal is burned The gas volume treated is 300 times the gas volume of an IGCC plant Combustion produces large quantities of waste & consumes more water than IGCC Source: GE 22

23 IGCC Concluding Remarks Gasification is a well-known process The CO 2 is separated and the decarbonized gaseous fuel is used for the gas turbine Advantages Proven CO 2 separation technology Co-production of hydrogen for power and/or other uses Disadvantages IGCC is unfamiliar technology for electrical utilities IGCC without CO 2 capture has generally higher costs than pulverized coal combustion but could change in the future for new plants/new technology 23