Method of igniting in situ oil shale retort with fuel rich flue gas

摘要

A technique is provided for igniting one in situ oil shale retort with flue gas from an earlier retort. Towards the end of oil shale retorting the flue gas from an in situ retort has a substantial fuel value so that it can be burned for generating heat. This fuel gas is conveyed to the entrance to a second retort and burned to initiate retorting. Even after retorting of the bed of particles in the first retort is completed, a fuel rich flue gas can be obtained and used for ignition of a subsequent retort. In either case the prior retort has a large bed of hot spent oil shale particles through which air is passed to burn carbonaceous material therein. Hot flue gas from the earlier retort can also be used for preheating.