Process for treating oil shale

A process for producing a crude shale oil and a high BTU gas comprising

• feeding a mixture of a major amount of crushed oil shale and a minor amount of coal, sufficient to provide process heat which is needed in excess of that supplied by burned char, to a rotary preheater,
• heating said mixture to a temperature less than that at which decomposition of kerogen begins, said heating by direct contact of said mixture with a flow of hot gases,
• passing said preheated mixture to a rotary retort,
• indirectly heating said mixture to a temperature in the range of 850.degree. to 1050.degree.F. with said hot gases, said hot gases indirectly heating said rotary prior to contacting said mixture in said preheater,
• taking off a vaporous overhead comprising shale oil and tar oil and leaving a char on said shale,
• passing said retorted mixture to a hopper,
• removing residual shale oil by sweeping said hopper with superheated steam,
• passing said vaporous overhead and stripped shale oil residual to a high temperature condenser,
• condensing an oil fraction at a temperature above 212.degree.F from said vaporous overhead and said hopper residual shale oil,
• passing the uncondensed gases from said high temperature condenser to a low temperature condenser,
• condensing water from said uncondensed gas,
• recovering a high BTU gas,
• passing said mixture from said hopper to a furnace, and burning said char and unvolatized coal to produce said hot gases, which pass from said furnace, first contacting said rotary retort and then directly contacting said mixture in said preheater.