It was invented by Paul W. Tamm and Gordon E. Langlois in the Chevron Research Company laboratory in Richmond, California.
The oil shale moves downward through the retort as fluidized bed of particles.
A stripping gas is inserted from the bottom of retort, which carries oil vapors into solids separation section.
The fine particles are directed to the combustor while oil vapors are moved to the condenser.
In condenser, shale oil is separated from water vapor and product gases.