| 摘要 |
A method of treating a solid carbonaceous material comprising essentially lignite or bituminous or subbituminous coal to provide therefrom finely dispersed solid particles substantially free of ash and sulfur, by mixing the solid material with a liquid aqueous alkaline solution comprising essentially a sodium, potassium, or ammonium hydroxide, hydrosulfide, or carbonate, or a plurality thereof; dissolving the material by heating the resulting mixture to a temperature in the range of about 125 DEG C to the critical temperature, at a pressure of at least about 25 psig, while maintaining a substantial portion of the mixture in the liquid state; separating from the resulting solution any undissolved coal, ash, and other solids; reducing the pH of the solution to less than about 9 to precipitate therefrom a powder comprising the carbonaceous material, with a substantial proportion of the ash and sulfur that had been in the starting material now remaining in solution; and separating the precipitated powder from the solution. Typically either the pH of the solution is gradually reduced to less than about 2 during a time of at least about 5 minutes, or the precipitated powder is washed with an acid solution having a pH of less than about 2.
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