Clean Coal Needs Another Look
Some in the coal industry have been promoting Integrated Gasification Combined Cycle (IGCC) power plants as the future for “clean coal”.
They should probably change their tune.
IGCC plants gasify coal, separating the CO2 from its combustible components, primarily hydrogen, and then burning the combustible components in a gas turbine, with the exhaust heat from the gas turbine used to produce steam for use in a turbine generator.
This schematic illustrates the complexity of an IGCC power plant.
The primary reason for building IGCC plants is to capture the CO2 so it can be sequestered underground.
The coal industry has been hard hit by EPA regulations that effectively prevent constructing new coal-fired power plants unless they emit less than 1,000 pounds CO2 per MWh.
IGCC plants can meet this requirement if the CO2 is captured and sequestered underground.
Three IGCC plants have been, or are being, built in the United States.
The Southern Company recently announced that the IGCC plant being built in Kemper, Mississippi, is over budget by around $1 billion.
This brings its cost to $5,876 per KW, nearly the same as the cost of a new nuclear power plant.
The second IGCC plant, built in Edwardsport, Indiana, cost around $5,340 per KW.
The third plant, built by Tampa Electric Company in 1996, under an agreement with the Department of Energy (DOE), was the first IGCC plant built in the United States.
The Tampa plant was about half the size of the two newer plants and cost around $4,000 per KW, adjusted for inflation. Tampa Electric cancelled plans for a second IGCC power plant.
None of these plants have been equipped to capture CO2 once it’s been separated from the gas stream, so the cost of this additional equipment would have to be added to the costs mentioned here, for the plants to stop emitting CO2 into the atmosphere.
The best strategy for the coal industry is to educate the EPA and the public on ultra-supercritical (USC)1 coal-fired power plants that are nearly as clean as natural gas combined cycle (NGCC) power plants. USC plants can meet EPA regulations except for CO2 emissions.
The improved efficiency of USC plants means that less coal is burned per MWh generated. Referring to the schematic, only about six components would replace all of those shown in the schematic2.
This might be a workable approach for the coal industry since the EPA is on legal thin ice in the way it approached the 1,000 pounds CO2 per MWh standard. This is because the EPA lumped natural gas and coal-fired power plants into the same source category.
Ultra-supercritical coal-fired power plants are being built in Europe and China, and should be the type of plant that’s referred to as “clean coal”.
If the EPA is going to establish limits on CO2 emissions they should be such that USC plants can be built, and then allow market forces to determine whether natural gas, coal, nuclear or renewable power plants are built.
The EPA is so focused on attempting to cut CO2 emissions 80% to meet the UN’s mandate, that it’s doubtful it would acquiesce to allowing any coal-fired power plant to be built, even the most modern and efficient USC plants, unless forced to do so.
- Pulverized coal plants with USC parameters of 4350 psi, and 1112/1112°F can be realized today, resulting in efficiencies of 44% (HHV) and higher vs 32% for the existing fleet of coal-fired power plants. The key to this performance are metals that can withstand these temperatures and pressures.
- A USC power plant would consist of a steam turbine, a generator, a condenser with a condensate pump, and a boiler with a boiler feed water pump. Ancillary components not shown in the schematic or in this list include items such as the vacuum system for the condenser and pollution control equipment for the boiler.
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