Shale retorting with supplemental combustion fuel

Claim 1

In a process for retorting lean oil shale wherein the process involves the steps of mixing raw oil shale with hot spent shale in the upper portion of a vertically elongated retorting vessel characterized by internal means to limit substantial vertical backmixing of solids passing downward therethrough; passing the mixture of raw shale and spent shale downward through the retorting vessel as a continuous moving bed of material; retorting the raw shale in the presence of a generally countercurrent flow of a stripping gas entering the bottom of the retorting vessel to carry away shale oil vapor and fines present in the retorting vessel; and burning the residual carbonaceous material adhering to the retorted shale in a liftpipe to heat the spent shale, the improvement comprising concentrating said fines in a portion of the shale oil liquid product; and combusting said portion of the shale oil liquid product with the residual carbonaceous material adhering to the retorted shale.