| 摘要 |
This invention discloses a staged process for drying wet carbonaceous materials such as sub-bituminous coal or lignite containing at least about 10 weight percent moisture, usually 15-50 weight percent moisture, by first heating the wet material under low partial pressure of moisture to permit the controlled rapid escape of surface moisture down to a critical moisture content of 8-12 weight percent. In a second step, the material is further heated at lower differential vapor pressure to provide for further moisture evolution at a slower controlled rate. This staged drying procedure permits wicking up of hydrocarbons contained in the coal to seal the surface of the dried coal product sufficient to prevent appreciable reabsorption of moisture and consequent heating and spontaneous ignition.
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