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Coal is the primary fuel source for electricity in the United States and the rest of the world. In fact, coal is responsible for 40 percent of world electricity generation.
Advanced coal technologies (ACTs) will reduce air emissions and other pollutants from coal-based power plants. Developing ACTs with carbon capture and storage (CCS) will allow the United States to continue using coal in a carbon-constrained world. And, we can export these technologies around the world to help other countries reduce their GHG emissions.
ACTs include:
- Supercritical and ultra-supercritical
Coal plants using supercritical and ultra-supercritical technology operate at increasingly higher temperatures and pressures than conventional plants. This allows the systems to achieve higher efficiencies and achieve significant CO2 reductions.
- Circulating fluidized bed combustion
This technology builds upon fluidized bed combustion (FBC) technology, which is a method of burning coal (and/or other solid fuels) that is fluidized by an upward flow of air on a bed of either inert material (usually sand) or sorbent material (usually limestone). The velocity of the air is such that the gases and solid produce a 'bubbling' or 'circulating' mixture. In a bubbling bed design, the velocity is relatively low in order to minimize the solids carryover from the combustor.
Circulating FBCs, however, employ high velocities to promote circulation of the solids. The circulating FBC maintains a continuous, high-volume recycle rate that increases the residence time, compared to the bubbling bed design. Because of this feature, circulating FBCs often achieve higher combustion efficiencies and better sorbent utilization than bubbling bed units.
- Integrated gasification combined cycle (IGCC)
Coal gasified by steam and air under high pressure and temperatures produces a synthetic gas (syngas), which is used as a fuel in an IGCC power plant. This technology uses a combined-cycle process with a gas turbine driven by the combusted syngas. Since most of the electricity is generated from the gas turbine, IGCC shows promise in providing high system efficiencies with ultra-low pollution levels.
Challenges
The coal and electric utility industries are working with the U.S. Department of Energy and the Electric Power Research Institute to develop ACTs through several research programs. Substantial new funding is needed to complete the research, development, demonstration, and deployment of these technologies.
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