Formation Mechanism and Model of the Initial Slag Layer on the Wall during the First-Time Start-Up Slagging Process in an Entrained Flow Gasifier

The formation of the initial slag layer during the first-time start-up serves as an essential step triggering subsequent overall slag deposition, which is critical for ensuring a safe and stable slagging process in a gasifier. The formation mechanism of the initial slag layer was analyzed in an entrained-flow gasifier. The results indicate that the formation of the initial slag layer primarily resulted from the condensation of alkali metal sulfate and chloride vapors, and the thermophoresis of these components occurs upon their formation into aerosol particles. The initial slag layer deposition rate is on the order of 10^-1 g/(m²·s), and the characteristic time for its formation is approximately on the scale of tens of minutes in the 2000 t/d coal consumption GSP gasifier. Besides, the influence of potassium and sodium content on both the initial slag layer deposition rate and the degree of deposition thickness nonuniformity varies considerably at different drying temperatures. In general, lower drying temperatures of the first-time start-up and higher alkali metal content in the feed coal promote the rapid formation of a relatively uniform initial slag layer.