Effect of pressure on ash formation during pulverised coal combustion and gasification

The effects of the operating pressure on ash formation during pulverized coal combustion and gasification presented in the open literature were presented. The operating pressure significantly influenced the size and the chemistry of ash generated through its effects on the structure of chars generated. Char particles generated at elevated pressures have high porosity. These char particles experienced more extensive fragmentation during the combustion and gasification, which led to finer ash particles compared to that formed at low pressures. At high pressure, the char particles burned faster. The char structure also determined the ash liberation for the different combustion stages. The particle size distribution (PSD) of ash was less sensitive to pressure during gasification process. Larger population of Group 1 chars were formed at higher pressure and finer ash particles were to be generated due to the formation of more porous chars. The formation mechanism for the finer ash during combustion results from more significant fragmentation and less coalescence of included minerals within the porous chars.