Abstract: Deposits of flyslag on the walls of a heat exchange zone employed to quench and cool synthesis gas and flyslag particles produced from the gasification of coal may be reduced by (a) temporarily increasing the flow rate of the synthesis gas and flyslag particles during the process to a space velocity of greater than at least 12 meters per second; or (b) after a shutdown or incident where flyslag is deposited, utilizing a space velocity of the synthesis gas and flyslag of greater than 12 meters per second for a time sufficient to remove the deposits, and then utilizing flow rates which prevent or inhibit deposition of flyslag.