AGGLOMERATION AND DEFLUIDIZATION UNDER SIMULATED CIRCULATING FLUIDIZED-BED COMBUSTION CONDITIONS

The role of inorganic matter in causing agglomeration and defluidization during the circulating fluidized-bed combustion of high-sodium, high-sulfur low-rank coals was reported in a previous paper. It was found that the ash formed during the combustion of these coals is transferred to the surface of the bed particles. The ash coating thus formed contains a molten phase at the furnace temperature, which makes the bed particles sticky. During the experiments, the effects of temperature and coal quality on the extent of agglomeration were also measured. The results, reported here, show that the tendencies for agglomeration and defluidization to occur increase markedly at temperatures above the initial ash sintering temperature when the ash coating on the bed particles exceeds a critical thickness. The proportions of the melt-forming inorganic elements and mineral inclusions in the ash also have a pronounced effect on agglomeration and defluidization tendencies. The results are considered to be of significance in the development of mechanistic models for agglomeration and defluidization.