Method of design for vertical oil shale retorting vessels and retorting therewith

In a process of contacting a particulate oil shale with a gaseous treating agent is a vertical shaft vessel, wherein a gravity flow of particulate oil shale passes through said vessel maintaining a constant bed depth by feeding raw oil shale at the top and removing treated particulate oil shale at the bottom, and a first gas stream for treatment is introduced into the bottom of the particulate oil shale, at least a second gas stream is introduced through orificed distributors at a temperature of up to about 1,400.degree. F at a position intermediate the top and bottom of the bed of oil shale to cause pyrolysis of the same and off-gas is withdrawn from the vessel above said at least second gas injection the improvement comprising:

• a. establishing a total flow of gas through the vessel of from 8,000 to 25,000 standard cubic feet of gas per ton of particulate oil shale;
• b. proportioning said gases between a first point of introduction adjacent the bottom of the bed and into at least a second point of introduction located between the top and bottom of the bed, wherein a plurality of orifices spread the gas across the lateral extent of the bed, said orifices being fed by a stream of gas in a distributor conduit at a velocity of Vi feet per second;
• c. providing a sufficient quantity of the gas introduced at the bottom of the bed so that it flows upwardly through the bed a velocity of Vg in feet per second, calculated on the basis of an empty vessel;
• d. providing a quantity of gas through each said orifice at a sufficient velocity Vh of gas issuing from said orifices so as to mix with the uprising flow of gas from the bottom of the bed at a velocity Vh in the range of 80-100 feet per second;
• and
• e. proportioning the velocities of the introduced gases so that the ratio Vh/Vi is at least 2 and the ratio of Vh/Vg is at least 15 to control contact velocity between the gases and the particulate oil shale.