Sulfur release and transformation during the pyrolysis of lignite with different particle sizes

The release and transformation behavior of sulfur during the pyrolysis of lignite with different particle sizes were investigated. Results showed that reducing the particle size of lignite could promote the transfer of more sulfur into gaseous phase and then improved the desulfurization extent of char. With the reducing particle size of lignite, the release amount of H2S, COS and SO2 increased. The temperature at which pyrite was completely converted to pyrrhotite and troilite decreased. At 800 degrees C, reducing the particle size intensified the capture of sulfur-containing gases by the coal matrix and alkaline minerals, resulting in the content of inorganic sulfides in char increased from 0.7 % to 0.86 %. At temperatures of 400-600 degrees C, the retention of organic sulfides, sulfoxide sulfur and sulfone sulfur in char decreased with the reducing particle size. At temperatures of 700-800 degrees C, the retention of thiophene-S, sulfoxide sulfur and sulfone sulfur in small particles was lower than that of large particles, while organic sulfides tended to be enriched in small particles.