| 摘要 |
PURPOSE:To obtain p-xylene (PX) in high efficiency reducing the consumption of coolant, by separating PX from a mixture composed mainly of 8C aromatic hydrocarbons by 3-stage crystallization process, wherein separations in the 2nd stage and the recovering stage are carried out by using a specific means. CONSTITUTION:A mixture of 8C aromatic hydrocarbons is cooled by a 1st stage crystallizer 1 to attain an outlet temperature of -60--75 deg.C and PX cake is separated from the mother liquor in the 1st stage separation zone 4. The 1st stage PX cake is dissolved in a 2nd stage mother liquor in a dissolution tank 6 and cooled by a 2nd stage crystallizer 2 to attain an outlet temperature of -15-0 deg.C. The cooled liquid is separated into PX cake and dilute solution by a liquid cyclone and the PX cake is separated into the 2nd stage PX cake (product) and a 2nd stage mother liquor by a centrifugal separator 5 and the 2nd stage mother liquor is circulated to the dissolution tank 6. The dilute solution is cooled to a temperature between the above temperatures by a recovery stage crystallizer 3 and separated by a liquid cyclone 8. The PX cake is circulated to the dissolution tank 6 and the recovered dilute solution is returned to the 1st stage crystallizer 1.
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