Shale retorting process

Claim 1

A continuous process for retorting oil shale which comprises: (a) introducing a solid heat-transfer material at an elevated temperature in the range 1000° to 2000° F and oil shale into a lower portion of a first vertically elongated vessel at a weight ratio of said heat-transfer material to said oil shale of greater than 0.1 and less than 5; (b) passing a lift gas containing less than 1 volume percent free oxygen upwardly through said first vessel at a linear velocity of 20 to 200 feet per second and sufficient to entrain and convey said oil shale and said heat-transfer material upwardly through said vessel, whereby said oil shale and said heat-transfer material are intermixed and said oil shale is rapidly heated to an elevated temperature between 700° F and 1200° F, vaporizing a first portion comprising less than 30 weight percent of the hydrocarbons in said oil shale, said oil shale having a residence time in said first vessel of less than 5 seconds; (c) separating from said lift gas a solid fraction comprising said heat-transfer material and oil shale; (d) introducing said solid fraction into the upper portion of a second vertically elongated vessel forming a downwardly moving bed of solids wherein additional heat is transferred from said heat-transfer material to said oil shale, vaporizing a second portion of the hydrocarbons in said oil shale; (e) withdrawing retorted solids and said heat-transfer material from a lower portion of said second vessel; (f) passing a stripping gas upwardly through said second vessel which entrains said vaporous second portion of hydrocarbons; (g) separating condensable hydrocarbons from said lift gas and said stripping gas; and (h) introducing retorted solids into a lift pipe combustor and combusting residual carbon in said retorted shale, forming spent shale at an elevated temperature in the range from 1000° F to 1600° F, and introducing said spent shale into said first vessel to provide said heat-exchange material.