Influences of phosphorus on ash fusion characteristics of coal and its regulation mechanism

A large quantity of livestock manure and sewage sludges produced annually in China, and the co-gasification with coal provides a promising way for these clean and large-scale utilization. The livestock manure and sewage sludges generally contain high phosphorus content. To explore the influences of phosphorus on the fusion temperatures (AFTs) of different coals and their mechanisms, the ash fusion variation behaviours of high aluminum Shajuzi coal (SJZ) and high calcium Zhundong coal (ZD) or Yimi coal (YM)) with different mass ratio phosphorus pentoxides (P2O5) were investigated by an AFT tester, x-ray diffraction, and FactSage software. The P2O5 addition could change the AFTs of three coals effectively, however the changing trend was different due to the difference in their ash-composition. With increasing P2O5 mass ratio, low melting point (MP) berlinite formation and high MP mullite content decrease resulted in decreases in the AFTs of SJZ mixture; while high MP calcium phosphates formation led to the AFTs of ZD or YM mixture increase. At high temperature the silicon in silicate or silicaluminate in ash compositions was gradually substituted by phosphorus with increasing P2O5 mass ratio and transformed into different MP phosphates because the ionic potential of P5+ (147 nm(-1)) was higher than that of Si4+(95 nm(-1)), which resulted in different variation behaviours in the AFTs of mixture.