Abstract: A technique is described for igniting the oil shale rubble pile in an in situ oil shale retort. A gas-air burner is lowered through a hole to a plenum over the oil shale to be ignited. An excess of air is passed through the hole and around the burner so that it is kept cool as the flame from it impinges on the rubble pile and the air also provides oxygen for combustion of carbonaceous material in the shale. Preferably the burner is in a cylindrical housing having a refractory exit nozzle at its lower end so that a hot flame is ejected downwardly. Air is brought to the inlet of the nozzle through an outer feed tube in the housing and coaxial therewith. Combustible gas is introduced through an inner axial feed tube which terminates short of the inlet end of the nozzle in a mixing chamber. A mixing orifice is provided between the mixing chamber and the nozzle for thorough mixing of the gas and inhibition of travel of the flame back into the burner.

Abstract: A technique is described for igniting the oil shale rubble pile in an in situ oil shale retort. A gas-air burner is lowered through a hole to a plenum over the oil shale to be ignited. An excess of air is passed through the hole and around the burner so that it is kept cool as the flame from it impinges on the rubble pile. The air also transfers heat downwardly into the rubble pile and provides oxygen for combustion of carbonaceous material in the shale. Preferably the burner is in a cylindrical housing having a flame exit at its lower end so that a hot flame is ejected downwardly.

Abstract: An in situ oil shale retort in which a cavity filled with broken particles of oil shale is formed within the subsurface oil shale formation and air is forced down through the cavity to sustain combustion of the top layer of oil shale particles. The products of combustion are withdrawn through a plurality of transverse exhaust pipes at the bottom of the cavity, the exhaust pipes each being provided with a series of holes along the length of the pipes within the cavity, the holes being graded in size to compensate for the pressure drop along the length of the pipe so as to provide substantially equal volume of gas flow through each of the openings.