【Weekly Topic】Coal with a high moisture content from pulverized coal pressurized gasification – what impacts does it have on the system?

Firstly, the high water content leads to a relative increase in the amount of water entering the downstream gas water treatment system； Furthermore, there is a minimum requirement regarding the moisture content of the water that enters the gasifier. If the moisture content in the coal is too high, it will prevent the dry distillation process from proceeding properly without adequate drying. When coal that has not been properly dried enters the gasification section, it lowers the temperature in that section, which in turn reduces the rate of methane formation as well as the reduction reactions of carbon dioxide and water vapor. This results in poorer conditions for gas production and a significant decline in the quality of the gas produced. Therefore, this type of gasification requires drying. The critical moisture content of lignite is 33~34%. In actual production, due to heat loss through radiation in all directions, the moisture content of the gasified lignite should generally not exceed 30%, and the temperature of the gas exiting the furnace must also be maintained at at least 250°C. If tar is returned to the furnace, the content of tar vapor in the gas increases; to prevent condensation, it is necessary to maintain a high temperature in the upper part of the furnace, with the temperature of the gas exiting the furnace needing to be kept above 350°C. Generally, gasification yields the best results when the moisture content in coal is around 20%. At this level, the dew point of the gas produced is approximately 190°C, while the temperature of the gas is 400°C; as a result, the sensible heat is low and heat loss is minimal.