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REDUCTION OF CARBON EMISSIONS FROM COAL ENERGY PLANTS

 

March 23, 2001

 

Terry R. Galloway, PhD                      William L. Millerd, PhD, S.J.

President                                              Federal Relations

Intellergy Corp.                                    Georgetown University

Berkeley, CA                                       Washington, DC

 

ABSTRACT:

            A combination of new technology is proposed to be applied in the repowering of the smaller and older coal power plants in the U.S. using steam gasification instead of a coal combustion furnace/boiler and use syngas powered fuel cell- enhanced turbo-generators instead the simple turbo-generators.  This new technology allows the fuel-to-electricity generation efficiency to be increased from around 34% to around 55%-70%  while simultaneously producing specific hydrocarbon products to sequester the carbon dioxide and avoid greenhouse gas emissions. By aggressively retrofitting only 97 of our old 1000 MWe coal plants, a 15% carbon emission reduction of 302 million tons can be met by 2010 ? the goal of the European Nations.  The application of this new technology opportunity can reposition the coal industry to a futuristic position as producer of energy and chemical products in a future greenhouse gas-sensitive world.

 

BACKGROUND & NEED:

            As you know the research community continues to be focused on identifying commercially attractive gas separation technologies to remove carbon dioxide (CO2) from stack gases and use new chemistry to utilize this carbon dioxide as a raw material to manufacture useful products that sequester the carbon.  This has, indeed, been a very large challenge with poor successes as summarized by the review papers [1,2]. Trying to scrub the CO2 from nitrogen-rich stack gases and trying to chemically react the recovered CO2 dissolved in scrubber liquid clearly is not the right path of research because of the technical difficulty and the process expense of reacting a carbon dioxide feedstock.

              The new concepts presented here (for which Patent #6,187,465 has been awarded) use commercially available steam reforming/gasification technology combined with fuel cells to generate electricity at high efficiency while being able to recover the greenhouse gases for the production of useful chemical products; thus, sequestering the CO2.  In this way, a combustible fuel feed gas can be fully oxidized without having the final oxidation products comingled with each other and hard to separate.

             One of our projects underway is to upgrade a typical old coal plant to a first-of-its-kind coal plant of the future, where coal co-mixed with waste can be fully utilized as an important energy and chemical resource without any emissions of CO2 and without the typical problems of nitrogen oxides (NOx), sulfur, and other particulate emissions [3,4]. 

             Using these new concepts, energy production also has several options that involve producing power that is on-peak only, power that is produced by the fuel-cells that is base loaded, and a combination tailored to optimally fit the local utilities load-following needs.

             The chemical production options are: methanol, higher molecular weight middle distillates (i.e. kerosene), lubricating oil, highway asphalt-extender, inorganic concrete additives; the latter products would utilize the carbon source so as to eliminate any carbon dioxide emission and at the same time sequester the CO2 for longer periods or forever.   So we see that the fossil plant of the future can be an integrated and combined simple chemical plant and power plant.  Methanol or hydrogen/fuel cell vehicles are another sustainable futuristic element in this community plan capitalizing on this energy/chemical plant.

             Since the fuel cell/turbine combined cycle system will produce electricity at a very high efficiency up to 70% for heat and electricity, compared to the old coal plant's efficiency of about 34% ?? more than double; the plant will produce the same electric energy but will now have extra syngas to make co-products.  The recycled carbon dioxide from the fuel cells is used to augment the syngas so that a portion can be diverted for the production of methanol or other chemical co-products.  In this manner, about half of the plant's feedstock can be used to manufacture chemicals from 500 to 2000 tons/day and still supply electric power from 100 to 1200 MWe.  And from a carbon balance standpoint, the carbon going into the plant equals the carbon leaving the plant as the carbon-containing co-product, with no objectionable carbon emissions to the environment.

             With this new technology breakthrough, coal can be fully utilized as an important energy and chemical resource without troublesome emissions of CO2 and without the typical problems of NOx, sulfur, and other particulate emissions.  Coal production in the U.S. was a record 1.062 billion tons in 1996, with 873 million tons burned by U.S. public utilities (5) producing about 742 millions tons of greenhouse gases (GHG).  Additonally oil and natural gas is burned in power plants as well to produce 698 million tons of GHG (6).  At the Kyoto and following conferences, the toughest issue was assigning the fair share of GHG reductions between the developing and the developed industrial nations (7).  This was a particularly difficult task since the U.S. produces 23% or 1437 million tons of the world's total of carbon emissions of 6250 million tons (7).  The developed industrialized countries produced 2970 million tons (2700 million metric tons) of annual carbon emissions from burning fossil fuels (6,7) in 1990 and 3190 million tons in 1996 that was the basis for the Kyoto protocol reductions.  We believe, for the purpose of this paper, that the emissions have not increased significantly from 1996 to the present.

             The bases for calculating greenhouse gas reductions involve 15%  (instead of the U.S. proposed 7%) below 2900 million tons 1990 levels which is 21% below the 1996 level of 3190 million tons of annual carbon emissions from burning fossil fuels in the industrialized countries (6,7).   If we focus on the coal industry, the coal feed to U.S. coal plants has a carbon content of 85% and an energy content of about 12,000 Btu/lb, and these plants operate at about 34% efficiency (from coal energy content to electrical energy output).   Our proposed new coal plants with improved power generation trains and fuel cells would operate at 68-70% efficiency, which is possible as outlined (8). These old plants would be modified and restarted to provide the same electrical output as before.  Note that the U.S. 7% GHG-reduction goals can be more than met by coal-fired plants only.  This is a very reasonable retrofit program and it is certainly technically and economically feasible (9).  It is possible also to evolve to meet >15% GHG-reduction goals with a combination of coal plants, refineries, and chemical plants, so that a big hit on one industry could be avoided.  However, a DOE/EPA incentive program for upgrading our old sub-optimal coal plants could make these conversions attractive for the coal industry.

             The Kyoto concensus (with the U.S. objecting) was to have all of the global GHG reductions to be made by the developed industrial countries that have contributed the great majority of the GHG emissions.  An approach would be to address the entire world's carbon emissions level of 6250 million tons, of which 2900 million tons is from the developed industrialized countries.  The majority of developing countries at Kyoto insisted that they should not be responsible for restricting their growth by having to reduce GHG that were caused not by them but by the developed industrial countries.  The U.S. produces (0.23 x 6250) or 1440 million tons of carbon emissions.  This reduces GHG emissions from burning of all fossil fuels, not just GHG emissions from coal plants.   But we will show that just repowering the old coal-fired power plants can be a feasible solution for reducing GHG emissions from  the burning of all fossil fuels.  Thus, satisfying the demands of the developing countries for calculating greenhouse gas reductions would involve 15%  (instead of the U.S. proposed 7%) below  1990 levels which is 21% below the 1996 level of 1440 million tons for the U.S..   To drop today's carbon emissions 15% below 1990 levels amounts to reducing carbon emissions by (0.21 x 1440) or 302 million tons for the U.S..  Thus, the coal feed involved for the 302 million tons of carbon emissions will be (302/0.85) 355 million tons/yr for the plants' input energy flux of 8.51x1015 Btu/yr.  With an average plant efficiency of 34%, the plants' electrical output would be 2.89x1015 electrical Btu/yr or 8.51x1011 kWeh/yr or 97,020 MWe.  This totals 97 coal-fired plants of typical 1000 MWe size that would be modified and restarted.  Although this is an aggressive retrofit program, it is certainly technically and economically feasible.

             Deploying this kind of new "green" technology will also stimulate new market demands and lower component prices in fuel cells, efficient turbines, load-following plants, methanol/hydrogen production from syngas, energy storage, methanol/hydrogen vehicles, solar PV, etc.? all new directions toward which the world economy wants to transition.

 


REFERENCES:

  1. Halmann, M.H., Meyer Steinberg, "Greenhouse Gas Carbon Dioxide Mitigation - Science and Technology, Lewis Publishers, New York, 1999.
  2. Hileman, Bette, "Industry Considers CO2 Reduction Methods, Chem & Engin News, pg. 30, June 30, 1997).
  3. Kaiser, Jocelyn, "Getting a Handle on Air Pollution's Tiny Killers, "Science, 276, 33 (1997)
  4. Raber, Linda,"Applause, Censure for Air Standards," Chem. & Eng. News, 75, No. 27, 31 (1997)
  5. U. S. Energy Agency, "U.S. Energy 1997, Washington, DC 20006
  6. Dunn, S. in "Vital Signs" 1997; Starke,L, Ed. W. W. Norton & Co., New York, 1997, p.58
  7. Cooney, Catherine M., "Nationals Seek 'Fair' Greenhouse Gas Treaty in Kyoto," Environ. Sci. & Technol., 31, No. 11, 5126A - 518A (1997).
  8. T. R. Galloway, "Steam-Reforming of Fossil Fuels and Wastes to Produce Energy and Chemicals Without Greenhouse Gases," invited plenary paper for Fourth World Peace Conference, Washington, DC, November 27-30, 1997 and Intersociety Energy Conversion Engineering Conference, Colorado Springs, August 2-6, 1998
  9. Intellergy Corp. and Big Sky Economic Development Authority, "Fuel Cell Technology Demonstration Project, Billings Montana -- Phase II: Feasibility Study on Repowering of the Corette Coal Power Plant,"  under DOE Grant DE-OHE-July 24, 2000.

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