Production of solid fuel-water slurries

A process for improving the pumpability of a high solids content water slurry of a solid fuel selected from the group consisting os sub-bituminous coal and lignite which comprises forming a water slurry of said solid fuel containing at least 50% solids by weight, said slurry also containing NH.sub.4 OH in an amount between 0.1 and 5.0 weight percent and also containing an anionic surface-active agent comprising a salt of an organic sulfonic acid in an amount between 0.01 and 3.0 weight percent, said amounts being based on the final weight of the slurry.