Second generation PFBC systems R and D - Phase 2 and Phase 3. Monthly technical report, 08/01/1999--08/31/1999

Abstract

When DOE funds were exhausted in March 1995, all Phase 2 activities were placed on hold. In February 1996 a detailed cost estimate was submitted to the DOE for completing the two remaining Phase 2 Multi Annular Swirl Burner (MASB) topping combustor test campaigns; in August 1996 release was received from FETC to proceed with the two campaigns to: (1) test the MASB at proposed demonstration plant full to minimum load operating conditions; (2) identify the lower oxygen limit of the MASB; (3) demonstrate natural gas to carbonizer fuel gas switching; and (4) demonstrate operation with low temperature compressor discharge air rather than high temperature ({approx} 1,600 F) vitiated air. The 18 in. MASB was last tested at the University of Tennessee Space Institute (UTSI) in a high-oxygen configuration and must be redesigned/modified for low oxygen operation. A second-generation PFB combustion plant incorporating an MASB based topping combustor will be constructed at the City of Lakeland's McIntosh Power Plant under the US DOE Clean Coal V Demonstration Plant Program. This plant will require the MASB to operate at oxygen levels that are lower than those previously tested. Preliminary calculations aimed at defining the operating envelope of the demonstration plant MASB have been completed. Phase 3--Commercial plant design update: The Second-Generation PFB Combustion Plant conceptual design prepared in 1987 is being updated to reflect the benefit of pilot plant test data and the latest advances in gas turbine technology. The updated plant is being designed to operate with 95% sulfur capture and a single Westinghouse 501G gas turbine. The 1987 study investigated two coal feeding arrangements, e.g., dry and paste feed. Paste feeding resulted in a lower cost of electricity. Paste, however, increases the water content of the carbonizer generated syngas; this increases the equilibrium partial pressure of hydrogen sulfide gas over calcium oxide/calcium carbonate and thereby reduces the carbonizer sulfur capture efficiency. Recognizing that the carbonizer and the CPFBC work together to control the plant overall sulfur capture efficiency, the higher CPFBC efficiency can compensate for the carbonizer's lower sulfur capture efficiency depending upon the amount of coal and/or char being fed to each unit. Since the latter are determined by the overall plant heat and material balance, they prepared a balance for each feed case to enable selection of the plant coal feed system.