Abstract: In processes for retorting oil shale using recycled heat carrying ceramic balls having a critical heat flux value, efficient operation, without heat shock damage to the balls, is obtained by operating at a weight ratio of balls to shale which is greater than but substantially equal to the ratio corresponding to the critical heat flux value; and this ratio is a function of both the heat transfer coefficient at the inlet to the retort and also the difference in temperature between the heat carrying balls and the oil shale. Implementing apparatus includes arrangements for controlling the ratio of heat carrying balls to shale, as by ball feed control apparatus and/or oil shale feed control apparatus, in accordance with the difference in temperature between the ceramic balls and the shale.

Abstract: In processes for retorting oil shale using recycled heat carrying ceramic balls having a critical heat flux value, efficient operation, without heat shock damage to the balls, is obtained by operating at a weight ratio of balls to shale which is greater than but substantially equal to the ratio corresponding to the critical heat flux value; and this ratio is a function of both the heat transfer coefficient at the inlet to the retort and also the difference in temperature between the heat carrying balls and the oil shale. Implementing apparatus includes arrangements for controlling the ratio of heat carrying balls to shale, as by ball feed control apparatus and/or oil shale feed control apparatus, in accordance with the difference in temperature between the ceramic balls and the shale.