Circulating fluidized bed boilers: Enhancing reagent utilization while maintaining proper SO{sub 2} removal

Conference · Wed Jul 01 04:00:00 EDT 1998

OSTI ID:20050954

Buecker, B; Wofford, J; DuBose, R; Ray, D

Circulating fluidized bed (CFB) combustion continues to be an emerging technology for a variety of reasons. The combustion chemistry and relatively low reaction temperature in the furnace minimize the production of sulfur and nitrogen oxides--both major pollutants of concern. In addition, CFBs can accommodate a wide variety of fuels, including those having low energy content, high sulfur, or both. Unit performance, and related operation and maintenance costs, is significantly affected by the sorbent selected for SO{sub 2} removal. While limestone is the typical reagent of choice, variations in limestone quality can have a dramatic impact on the reaction efficiency. The following article discusses the results of full-scale tests of high-quality limestone that were performed on the two, 50,000 lb/hr CFBs serving the University of North Carolina. The test were needed because the primary reagent being used at the facility was unreactive and caused ash handling problems. The report also discusses results from subsequent use of this better reagent. The test indicated that while limestone purity (CACO{sub 3} content) is an important factor in sorbent reactivity, crystalline structure and size distribution are just as important. The tests suggested that limestone consumption could be decreased by over 50% with the new stone. This conclusion was verified when the University began using the new stone on a permanent basis. Plant personnel were able to significantly reduce limestone costs and lower the amount of unreacted lime in the boiler ash. This latter item had caused problems with the public and environmental authorities, because clouds of water vapor were produced when the ash was wetted for hauling and disposal. Ash production volumes and the associated disposal costs were reduced as well. For present or prospective CFB managers, these results can easily justify the search for, and use of, limestones that otherwise would be considered too expensive or too distant from the plant. Benefits include increased SO{sub 2} removal efficiency, decreased ash production, and lower reagent costs.

• Research Organization: Burns and McDonnell Engineering Co. (US)
• OSTI ID: 20050954
• Report Number(s): CONF-971214--
• Country of Publication: United States
• Language: English

Related Subjects

01 COAL, LIGNITE, AND PEAT
20 FOSSIL-FUELED POWER PLANTS
AIR POLLUTION ABATEMENT
AIR POLLUTION CONTROL
ASHES
CALCIUM CARBONATES
CIRCULATING SYSTEMS
COAL
FLUIDIZED-BED COMBUSTORS
FOSSIL-FUEL POWER PLANTS
LIMESTONE
NITROGEN OXIDES
SORBENT INJECTION PROCESSES
SULFUR DIOXIDE