High-temp. retorting of oil shale - with preliminary partial dehydration to maximise retorting capacity and inhibit pitch deposition

摘要

In the prodn. of shale oil and other products from oil shale by reheating at 800-1000 degrees F in a rotating, horizontal, cylindrical vessel, the improvement comprises subjecting the subdivided shale, prior to the retorting, to a preliminary partial dehydration in (i) a fixed-shell, vertical, cylindrical vessel or (ii) a rotating, horizontal, cylindrical vessel of lower volume capacity than the retorting vessel. The partial dehydration is effected at 212-550 degrees F to remove free and combined water from the shale. Both the preliminary dehydration and the subsequent retorting operation are carried out by indirect heat exchange with hot combustion and flue gases. The preliminary partial dehydration removes a sizeable burden from the retorting stage and thus increases its capacity. The tendency for pitch to deposit on the inner sides of the retorting step is avoided.