Effect of ash components and atmospheres on slagging characteristics of high-AAEM lignite gasification

Two kinds of high alkali and alkaline earth metal (AAEM) lignite (TTc and ZDc) were used as fuels, and three atmospheres of CO2, CO/CO2, and H2O (g) were used in the horizontal tube furnace experiments to simulate the gasification conditions in different parts of the boilers. The relevant thermodynamic calculations on the atmospheres and ash compositions were conducted in FactSage 7.2. The results show that both two coals have a high risk of slagging. Decreasing the relative content of SiO2 or increasing the relative content of Al2O3 can increase the ash fusion temperatures (AFTs) of TTc; increasing the relative content of CaO can increase the AFTs of ZDc. Besides, it is not recommended to adjust the relative content of Fe2O3. The proportion of the liquid phase of ZDc ash in CO/CO2 atmosphere is much higher than that of CO2 and H2O (g) in a typical circulating fluidized bed (CFB) gasification temperature interval, while the generation of liquid phase of TTc ash is less affected by atmospheres. The bottom of boilers is the most severe slagging zone, and purging with H2O (g) is a good way to alleviate the low-temperature slagging of the return feeder.