| 摘要 |
U.S. 762,548 In a coal gasification operation or similar conversion process carried out in the presence of an alkali metal-containing catalyst wherein solid particles containing alkali metal residues are produced, alkali metal constituents are recovered from the particles by mixing them with calcium oxide or a solid calcium-containing compound that decomposes upon heating to from calcium oxide, and heating the resultant mixture of solids to a temperature sufficiently high to cause calcium oxide to react with water insoluble alkali metal aluminosilicates in the alkali metal residues to produce reaction produces containing water soluble alkali metal aluminates and water insoluble calcium silicates. The reaction products are contacted with water, which leaches the alkali metal aluminates and other water soluble alkali metal constituents from the solids. The pH of the resultant aqueous solution is lowered by contacting it with a carbon dioxide-containing gas under conditions such that carbon dioxide reacts with the alkali metal aluminates to form a water insoluble precipitate containing aluminum hydroxide and an aqueous solution containing water soluble alkali metal carbonates. The aqueous solution is recycled to the gasification process where the alkali metal carbonates serves as at least a portion of the alkali metal constituents which comprise the alkali metalcontaining catalyst. This process permits increased recovery of alkali metal constituents, thereby decreasing the overall cost of the gasification process by reducing the amount of makeup alkali metal compounds necessary. |
