Bed material agglomeration during fluidized bed combustion. Technical progress report, January 1, 1994--March 31, 1994

Abstract

Laboratory combustion tests conducted this quarter support the hypothesis that localized reducing conditions promote formation of agglomerates in the bed of fluidized bed boilers. These tests were designed to simulate localized reducing conditions found in commercial fluidized bed combustors. Localized reducing conditions may occur from either poor lateral bed mixing or oxygen-starved bed conditions due to the coal feed configuration. It was found-that agglomeration can occur at lower theoretical air values while operating temperatures are within the range of fluidized bed boilers. Cohesion of bed particles appears to take place very rapidly when theoretical air in the bed approaches 70%. These tests also indicate that bed temperature, pressure drop, oxygen and carbon dioxide concentrations are affected by agglomeration. Agglomeration appears to result in: (1) An increase in the frequency of pressure fluctuations (bed pressure drop). (2) An increase in the magnitude of pressure fluctuations (bed pressure drop.) (3) A possible decrease in bed pressure differential over time. In addition, there appears to be an increase in the amount of available oxygen and a decrease in CO{sub 2}. Agglomerates formed in the laboratory are being subjected to mineralogical analyses which will then be compared to similar analyses of agglomerates removed frommore » commercial boilers.« less