Sulfur Transformation in the Process of Circulating Fluidized Bed Combustion Combined with Coal Pyrolysis

Abstract

The transformation of sulfur was experimentally investigated in a polygeneration process that integrated coal combustion and pyrolysis. High-sulfur Yanzhou coal was pyrolyzed together with circulating ash in a fixed bed. The circulating ash not only fixed some of gaseous sulfur but also decreased the sulfur remained in char compared with coal pyrolysis alone. This unexpected decrease of sulfur in char was due to the rapidly absorption of active sulfur by circulating ash, which effectively inhibited the reactions between active sulfur and organic matrix or mineral matters in coal. The amount of sulfur fixed in ash was increased by raising the pyrolysis temperature and decreasing the ash particle size, while only part of it was secondly released during combustion. The desulfurization burden of circulating fluidized bed boiler was reduced by about 34% in the polygeneration process when pyrolysis and combustion temperatures were 650 and 950 °C, respectively.