Role of Coal in Modern Electricity Role of Coal in Modern - PowerPoint PPT Presentation

Role of Coal in Modern Electricity Role of Coal in Modern Electricity Generation Systems Generation Systems Energy and Environment Seminar Series Energy and Environment Seminar Series John Kramlich John Kramlich UW Mechanical Engineering UW Mechanical Engineering December 2, 2010 December 2, 2010

US Energy Usage (Quads=E+15 BTU) Transportation Heating Electricity Total Petroleum Natural Gas Nuclear Renewable Coal Total

US Energy Usage Transportation Heating Electricity Total Petroleum 26.3 10.3 0.4 37.1 Natural Gas Nuclear Renewable Coal Total

US Energy Usage Transportation Heating Electricity Total Petroleum 26.3 10.3 0.4 37.1 Natural Gas 0.7 16.2 6.9 23.8 Nuclear Renewable Coal Total

US Energy Usage Transportation Heating Electricity Total Petroleum 26.3 10.3 0.4 37.1 Natural Gas 0.7 16.2 6.9 23.8 Nuclear 0 0 8.5 8.5 Renewable Coal Total

US Energy Usage Transportation Heating Electricity Total Petroleum 26.3 10.3 0.4 37.1 Natural Gas 0.7 16.2 6.9 23.8 Nuclear 0 0 8.5 8.5 Renewable 0.8 2.7 4.1 7.7 Coal Total

US Energy Usage Transportation Heating Electricity Total Petroleum 26.3 10.3 0.4 37.1 Natural Gas 0.7 16.2 6.9 23.8 Nuclear 0 0 8.5 8.5 Renewable 0.8 2.7 4.1 7.7 Coal 0 1.8 20.5 22.5 Total 27.8 21.4 40.5 99.6

Historical Trends

US Energy Usage Transportation Heating Electricity Total Petroleum 0.4 Natural Gas 6.9 Nuclear 8.5 Renewable 4.1 ~1 cubic Coal 20.5 km/yr Total 40.5

Conventional Power Plant Scrubber for SO 2 Catalyst for NO Electrostatic Filter for Particles CO 2 H 2 O SO 2 Steam NO Particles Generator ~36% Air Coal: Cooling 100% Water ~64% Pump

The Achilles Heel • Huge thermodynamic irreversibility between flame and steam Research: Increase maximum metalurgical • Option 1: Plug the hole temperature with a new cycle • Option 2: Move the steam closer to the combustion

Insert a Second Cycle

Insert a Second Cycle • Second cycle is mercury • More heat accepted at Still under higher temperatures metallurgical limit • Several of these plants built and operated in the 1930’s-1940’s

Increase Steam Pressure • Supercritical Rankine • Many new boilers today Research: Corrosion resistance at high T and 30 MPa (300 atm)

Coal Composition • C • CO 2 • H • H 2 O • O • N (~1%) • N 2 or NO • S (0.5-6%) • SO 2 • Main Minerals • Ash (Si, Fe, Na, K, Mg, Ca, Al) • As, Se, Pb, etc., U, Hg • Trace Minerals

Environmental Cost Huge Scrubber cost at Centrailia: $200,000,000 for 1340 MW ($149/kW) Catalyst for NO control Research: Economical and effective Hg control Ash Control SO 2 Scrubber Hg Control

Mercury Problem • Original proposal: -38 tons by 2010 US Anthropogenic -18 tons by 2018 159 tons/yr • Vacated by court • New rule on the way US Coal 52 tons/yr

Environmental Fate Elemental - Hg: Oxidized - HgCl 2 : • Lifetime: 0.5-1.5 years • Lifetime: hours • Time to distribute • Falls in footprint worldwide downstream of source Emission at Surface

Health Effects • Water-soluble Hg to lakes • Bacteria convert oxidized Hg to methylmercury (highly absorbable, fat soluble, goes to brain) • This biochains up to fish, which are the main path for human exposure • Reference dose: 0.1 µ g/kg body weight/day (0.18 g/lifetime)

State of the Art 3. At furnace exit, oxidized vs. 1. All Hg in fuel is vaporized elemental varies. 2. All vaporized Hg is initially elemental 4. Fraction captured is highly variable (5-95%). Correlates with oxidized, but with scatter. Scrubber •Oxidized: >80% •Elemental: <30% Fuel 5. Spray dryer elemental: Air •~40% •With activated carbon /iodine: >90% 6. Force oxidation ahead of scrubber (meets interim regulation)

Oxidation Reactor

Competition: Gas Turbines Fuel Generator Air Pump Hot Exhaust Burner Turbine

Combined Cycle • Connects gas turbine and steam together CO 2 • Each solves the others problems • No environmental cleanup often needed Generator Natural Generator Gas Gas Turbine Hot Exhaust Air Cooling Water Generators recover ~58% of fuel energy ~42% Losses are ~42% No need for SO 2 , NO, particle cleanup Pump Still make CO 2

Not as Simple as it Seems; But still, why not gas?

Coal is Cheaper, Gas is Unstable 2005 2008 Retail gasoline: $22.5/million Btu 2001 Coal=2.5 Coal=1.25 $/Million Btu

Integrated Gasification Combined Cycle Coal for Combined Cycles Water Coal • Mass flow of air/products ~15x fuel flow • Cleanup much easier on fuel stream than product gas -Smaller equipment Air Air O 2 Gasifier -Larger driving forces for mass transfer Seperator • Currently, fuel cooled to room temperature for cleaning CO N 2 H 2 Fuel S, N 2 Cleaning Generator Generator Air Gas Turbine Hot Exhaust

Integrated Gasification Combined Cycle Coal for Combined Cycles Water Coal • Fuel cooling a thermodynamic loss • Research: Hot gas cleanup approaches Air Air O 2 Gasifier Seperator CO N 2 H 2 Fuel S, N 2 Cleaning Generator Generator Air Gas Turbine Hot Exhaust

Remaining Losses • In a well-optimized IGCC system, one of the largest remaining thermodynamic irreversibilities is the combustor • Approach is to replace the combustor with an adiabatic solid oxide fuel cell

Solid Oxide Cell System CO/H 2 CO/H 2 Research: Lower T, lower cost SOFC Combustor Solid Oxide Fuel Cell Electricity Compressor Turbine Compressor Turbine Air Air To Steam To Steam Cycle Cycle

Mountaineer West Virginia 1st Pilot Sequestration Plant 1.5% of Plant Output

Process Flow Chart

Spray Absorber (NH 4 ) 2 CO 3 + CO 2 + H 2 O -> 2(NH 4 )HCO 3

Regeneration 2 (NH 4 )HCO 3 -> (NH 4 ) 2 CO 3 + CO 2 + H 2 O Steam reverses the absorption reaction Releases pure CO 2 and H 2 O

CO 2 /H 2 O Compressor Station

Well Injection Point • Water/CO 2 mix pressurized to ~100 atm.

Injection to 8000 ft

Oxyfuel Alternative • Must pay for air separation • No need to process large gas flow through scrubber

Economics-New Capacity • Simple boiler, no environmental control: 2 ¢/kW-hr • Coal supercritical: 10.5 ¢/kW-hr, 14 ¢/kW-hr with 90% carbon capture • IGCC 11.5 ¢/kW-hr, with carbon capture 16 ¢/kW-hr • Gas combined cycle 9 ¢/kW-hr • Nuclear 12 ¢/kW-hr • Solar tower 12, solar trough 20, PV 16-20 ¢/kW-hr • Wind 6-11 ¢/kW-hr (including tax credits) http://www.ethree.com/clientlist.html http://bit.ly/Lazard2009 • Two years ago, people were looking at nuclear, supercritical Rankine coal • Now they are looking again at gas. If gas prices stay down, this could be a longer term direction.