Simulations of Second Generation of Pressurized Fluidized Circulating Bed Combined Cycle
[1]
Hossin Omar, Mechanical Engineering Department, University of Benghazi, Benghazi, Libya.
The performance of the second generation of the Pressurized Fluidized Circulating Bed (PFCB) combined cycle is presented in this chapter. The second generation of PFCB combined cycle consists of gas turbine cycle and steam turbine cycle including reheat. Simulations to balance the energy between the elements of the unit where conducted. The PFCB is as a combustor of solid fuel (coal) and it is a steam generator at the same time. The small pieces of coal motion behaves as fluid when it exposes to a compressed air, which enters from the bottom of the PFCB unit. The small pieces of coal air mixture flow through the fluidizer, which is a big disk has small holes allows the mixture to flow up uniformly. This uniform motion of solid fuel air mixture accelerates the combustion and increases its efficiency, and this in turn increases the efficiency of the unit. The heat release inside the PFCB unit exchange with water flow in tubes inside the unit to produce super-heated steam to operate two stage steam turbines. The remaining heat energy in a form of hot gases exits from the PFCB unit enters to a cyclone to separate the solid pieces in form of ash. While the filtered hot gases operates a gas turbine. The simulations were carried out for PFCB combined cycle plant. It was found that increasing of the steam inlet pressure results in an increase in the steam and the combined cycle efficiencies. The flue gases of the gas turbine flue gases inlet temperature results in an increase in the gas turbine and in the combined cycle thermal efficiencies. The peak of the PFCB based combined cycle thermal efficiency occurs at a compression ratio of approximately 18. The simulations were carried out for only one fuel composition and for a compression ratio ranges between 1 to 40.
Pressurized Fluidized Circulating Bed (PFCB), Higher Heating Value (HHV), Atmospheric Circulating Fluidized Bed (ACFB)
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