| 摘要 |
In a process for recovering liquid and gaseous products from an in situ oil shale retort containing a fragmented permeable mass of particles containing oil shale, a heated zone is established in an upper portion of the fragmented mass. For a period of normal retorting operation, an oxygen containing gas is introduced to the fragmented mass on the trailing side of the heated zone at a sufficient rate for advancing the heated zone downwardly through the fragmented mass and liquid products and a relatively lean off gas containing gaseous products are withdrawn from the bottom of the retort. Thereafter, for a period of post-retorting operation, the introduction of gas to the fragmented mass is reduced to a rate such that a relatively rich off gas is withdrawn from the retort. The rich withdrawn off gas preferably has a heating value of at least about 75 BTU/SCF. The reduced rate of introduction includes substantial closing of an end of the retort or introduction of gas at a rate less than about 10% of the rate of introduction of gas to the retort during normal retorting operation. Relatively rich off gas from post-retorting operation is preferably withdrawn from the top of the retort and can be used for igniting another retort or for sustaining a secondary combustion zone in a second retort.
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