Fossil fuel power plants account for about a third of global carbon dioxide emissions. Coal is the major power-generation fuel, being used twice as extensively as natural gas (IEA, 2003). Moreover, on a global scale, coal demand is expected to double over the period to 2030; IEA estimates that 4500 GWe of new installed power will be required. Coal is expected to provide 40% of this figure. It is thus obvious that coal power plants must be operative to provide such amount of energy in the short term, at the same time reducing their CO2 emissions in a feasible manner and increasing their efficiency and capacity. However, the main technologies currently considered to effect CO2 capture, both post-and pre-combustion, introduce a great economic penalty and largely reduce the capacity and efficiency. One of these technologies involves the separation of CO2 from high temperature flue gases using the reversible carbonation reaction of CaO and the calcination of CaCO3. The process is able to simultaneously capture sulfur dioxide. The major disadvantage of this well-known concept is the great amount of energy consumption in the calcinator and auxiliary equipment. This paper proposes a new, feasible approach to supply this energy which leads to an optimal integration of the process within a conventional coal power plant. Calcination is accomplished in a kiln fired by natural gas, whereas a gas turbine is used to supply all the auxiliary power. Flue gases from the kiln and the gas turbine can substitute a significant part of the heat duty of the steam cycle heaters, thus accomplishing feed water repowering of the steam turbine. This novel CO2-capture cycle is proposed to be integrated with aging coal-fired power plants. The paper shows that an optimal integration of both elements represents one of the best methods to simultaneously achieve: a) an increase of specific generating capacity in a very short period of time, b) a significant abatement of CO2 emissions, and c) an increase of plant efficiency in a cost-effective way.

Volume Subject Area:
Advanced Energy Systems
Topics:
Carbon dioxide, Cycles, Fossil fuel power station, Coal, Emissions, Coal power, Flue gases, Gas turbines, Kilns, Natural gas, Carbon capture and storage, Combustion, Energy consumption, Energy generation, Feedwater, Fuels, Heat, High temperature, Power stations, Separation (Technology), Steam, Steam turbines, Sulfur
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