| 摘要 |
In a coupled coal solvent liquefaction-gasification system wherein a recycle mineral residue-containing slurry is mixed with the raw coal feed slurry for the liquefaction zone, the resulting feed slurry is under a pumpability total solids level constraint. Where a coupled system is operating under such a total solids level contraint for the feed slurry, any increase in the mineral residue recycle rate relative to the coal feed rate advantageously provides a catalytic activity and selectivity advantage in favor of liquid coal product at the expense of higher and lower boiling products. It is shown herein that this activity and selectivity effect is enhanced with decreasing liquefaction zone residence times. In accordance with the present invention, the ratio of recycle mineral residue to feed coal is enhanced by recycling a second mineral residue-containing slurry to the liquefaction zone independently of the raw coal feed slurry. The amount of solids in the second recycle slurry can be established to compensate for a progressive reduction in solids level in the process slurry due to the dissolving of feed coal so that the process slurry continues to maintain the maximum total solids constraint in spite of progressive coal solvation. |
