| 摘要 |
A fragmented permeable mass of formation particles containing oil shale and carbonates of calcium and magnesium is formed in an in situ oil shale retort. A combustion zone is advanced through the fragmented mass, whereby kerogen in oil shale in the fragmented mass is decomposed in a retorting zone on the advancing side of the combustion zone to produce gaseous and liquid products including shale oil. The combustion zone also converts the magnesium values in the particles of retorted oil shale to a more leachable form such as magnesium oxide. Magnesium values are selectively leached from the combusted particles, with respect to calcium compounds, with an aqueous solution of a purgeable, acid-forming gas such as carbon dioxide and a minor amount of a polyelectrolyte such as polyacrylic acid, polysulfonic acid, polyphosphonic acid, or the salts thereof. An enriched solution containing magnesium values is withdrawn from the fragmented mass and magnesia is recovered from such enriched solution.
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