The present invention is directed to a process for producing ultra clean liquid fuel from abandoned mine waste. A feedstock is prepared from water and coal mine waste having relatively high ash (non-carbonaceous matter) content. Foundry slag is added to the feedstock as a fluxant to adjust the melting behavior of the ash in the feedstock. Preferably, the fluxant is blast furnace slag provided in a particle size of less than about 150 μm and is provided in an amount sufficient to lower the melting point of the ash in the feedstock by at least about 200° F. The feedstock is admitted with a flow of oxygen into a pressurized chamber of an entrained flow gasifier in which the feedstock and oxygen are heated to produce a synthetic gas from a coal component of the feedstock and molten slag from the ash and fluxant components of the feedstock. The molten slag is of a viscosity to freely flow out of the gasifier through an exit port in the bottom of the gasifier. The synthetic gas can be used to produce paraffin from which ultra clean liquid fuel can be produced.