The efficient operation of entrained flow slagging gasifiers is dependent upon the mineral content of the coal supply that is used in the gasifier. When the gasifier is operated at the optimal temperature for gas production, the minerals must form a molten slag which has a viscosity low enough for the slag to flow down the lining of the gasifier without causing deposits that can plug the gasifier, yet not so low as to cause excessive erosion of the gasifier lining. This work details the use of new fluxing agents that can be used at low levels and are effective at lowering the viscosity of coal slags and expanding the range of coals that can effectively be used as gasifier fuels. (c) 2012 Elsevier B.V. All rights reserved.