Construction and operation of the 4MWth twin-bed PFBC pilot plant for operation reliability test

Babcock-Hitachi (BHK) together with Hitachi, Ltd. has been involved in the development and planning of a large-scale coal fired PFBC combined cycle power plant. Based on its past experience in operating a 150KWth benchscale PFBC, a 2MWth PFBC of 4m bed height, and a 15MWth PFBC, several technological ideas are being incorporated into the design of large-scale PFBC boilers. These ideas include: (1) A twin-bed concept in the steam generator for improved efficiency. (2) Employment of SNCR and SCR for stringent NOx regulations. The former idea is to design a steam generator with two beds each contained in separate pressure vessels. One of the two beds of the same dimensions contains the evaporator and superheater, while the other bed contains the reheater and superheater. In this setup, reheater steam temperature can be controlled by adjusting the bed height independently from the other bed without the usual spray tempering strategy under steady state conditions, thus the loss caused by spraying can be eliminated and the overall plant efficiency improved. Aiming at demonstrating the operation and control of a PFBC that uses those technologies and also improving the unit operability, a 4MWth (two 2MWth beds) PFBC pilot plant with necessary auxiliary equipmentmore » such as a paste fuel system, an ash withdrawal system, and a gas cleaning system was planned and constructed in 1994. This paper presents the design features of the 4MWth PFBC pilot plant and operating experiences obtained during the initial test period. A brief review of a future large-scale PFBC boiler design concept is also included.« less