Basic design studies for a 600 MWe CFB boiler (270b, 2 x 600 C)

Commercial CFB boilers are currently available in the 300 MWe equivalent range for use with international coal. Retrofitting of Provence 4 with a 250 MWe CFB boiler was an important step in CFB development. In light of the results obtained from two large French units--Emile Huchet 4 (125 MWe) and Provence 4 (250 MWe)--this paper focuses on the main technical points which are currently being studied in relation to the basic design of a 600 MWe CFB boiler, a project that has been undertaken by EDF. The general aim of this project is to demonstrate the competitiveness of a CFB boiler compared with a PF boiler. The main areas of focus in the design of this large CFB boiler with advanced steam conditions are described. These points are subjected to particular analysis from a design standpoint. The objective is to prepare the precise specifications needed to ensure a product which is optimized in terms of quality/cost or service/cost. Due to the present lack of theoretical understanding of the refined and complex two-phase flow, design is a challenge which has to be based on reliable and comprehensive data obtained from large plants in commercial operation. This will ensure that the advantagesmore » of CFB which arise from the hydrodynamics within the circulation loop are maintained. The major goals of maintaining good particle residence time and concentration in the furnace are described. Misunderstanding of CFB furnace bottom conditions is also pointed out, with cost reduction and better NO{sub x} capture certainly among the major new targets in relation to bottom furnace design. General problems associated with the heat exchanger arrangement, principally those linked to high steam conditions and, especially, the vaporization system, are discussed. Once again, comparison with PF in this area showed that CFB boilers appear more competitive. Finally, the main area in which there is a need for sharing of CFB experience among CFB users is pointed out.« less