OCR Text |
Show APPLICATION EXPERIENCE ON A WOOD FIRED eFB BOILER The THERMAL DENOX Process has been operating since 1989 at the Ultrapower Malaga Cogeneration Plant located in Fresno, California. The circulating fluidized bed boiler fires up to 380 MBTU/hr of wood waste containing water between 30 to 50% by weight, produces 220,000 lb/hr steam at 1270 psia & 955 OF, and has an untreated NOx emission of 120 PPMv at maximum conditions, or 160 PPMv dry. In addition to the THERMAL DENOx system for NOx reduction, the Malaga plant includes a multiclone and an electrostatic precipitator for particulate removal. MALAGA THERMAL DENOX SYSTEM DESIGN The Malaga THERMAL DENOx system was designed and guaranteed to achieve an outlet emission below 27.5 Lb NOx/hr. The worst case conditions were defined as those which result from maximum firing of wood waste fuel containing 50% H20 by weight. At the worst case with an untreated NOx value of 120 PPMv at conditions ( 160 PPMv dry, or .23 Lb NOx/MBTU), a 68% NOx reduction was required to meet the limit of 27.5 lb NOx/hr leaving the stack (50 PPMv dry, or 0.07 Lb NOx/MBTU). The Malaga boiler design conditions were for operations at essentially 100 % base load for perhaps 300 day runs. The steady operation, and the low fluctuation of fluegas temperature and composition allowed for a relatively simple choice for injection configuration. Installation of nozzles downstream of the cyclone provided su ffi cient residence time for the mixing and reactions to take place. One 12,000 Gallon anhydrous ammonia storage provides 30 days storage and a 13.7 KW ammonia vaporizer provides ammonia vapor to the injectors. One 143 BHP air compressor delivers 1170 SCFM air for use as a carrier to assist in mixing of the ammonia with the NOx. The design also includes separate controls for the air and ammonia. Air is controlled by a pressure control valve as a function of boiler load. Ammonia flow is controlled by a flow control valve as . a function of steam production, fluegas 02 concentration and temperature. Ammonia trim is provided via a stack NOx signal. MALAGA PROCESS PERFORMANCE The Figure and data in table below were provided by Ultrasystems, and show data taken on October 26, 1990. The data shows that NOx reduction from an untreated value in the range of 125 PPMv dry down to values between 40 and 50 PPMv dry was easily achievable with Ammonia Injection on the order of 35 Lb/hr. The THERMAL DENOx process achieved a 64% NOx reduction for these conditions. Additionally, the table shows that Carbon Monoxide (CO) and Carbon Dioxide (C02) values are basically unaffected by the NH3 injection in the THERMAL DENOx Process. This is consistent with other studies which show that Selective Non Catalytic Reduction with Ammonia as the reductant does not increase CO or C02 emissions to any great extent, while using urea as a reductant can have a measurable increasing effect on the CO, &/or C02 emissions from the stack. MALAGA FLUE GAS COMPOSITION @ AIR PREHEATER OtITLET -VARIOUS OPERATIONS D[I CQnSlilUknlS OPERATING 02 CO2 00 NO CONDmON % % PPMv PPMv NH3 Injection 7.4 13.7 10.3 126.2 = 0.0 Lb/hr NH3 Injection 7.3 13.9 10.0 43.2 = 35 Lb/hr NH3 Injection 6.2 14.7 10.8 126.2 = 0.0 Lb/hr & Low Excess 02 NH3 Injection 6.5 14.7 11.1 51.5 = 35 LB/hr & Low Excess 02 |