Patent ID: 8686186
Filing Date: 2014-04-01
Classification: C07C

Abstract:
1. A method of cooling a mother liquor stream, comprising: providing the mother liquor stream having a temperature of about 140 to 170° C. at a pressure of about 3.5 to 8 bar(a), wherein the mother liquor stream is a saturated solution including terephthalic acid and paratoluic acid in water, and contains less than about 1% w/w of fine solid particles of terephthalic acid; introducing the mother liquor stream to a flash tank where the pressure in the flash tank is about atmospheric pressure, wherein steam from the mother liquor stream is generated and removed from the flash tank; flowing the mother liquor stream to a cooler in a first pipe, wherein at a mixture point prior to the mother liquor stream entering the cooler, the mother liquor stream is mixed with a secondary mother liquor stream at about 40 to 60° C., wherein the mixture of the mother liquor stream and the secondary mother liquor stream forms the mother liquor mixture, wherein the mother liquor mixture is at about 60 to 80° C. after mixing the mother liquor stream and the secondary mother liquor stream, wherein prior to entering the cooler, a portion of the terephthalic acid and the paratoluic acid are precipitated from the mother liquor mixture; cooling the mother liquor mixture to about 40 to 60° C. in the cooler; flowing the mother liquor mixture out of the cooler towards a filter; flowing a first portion of the mother liquor mixture to the filter; and flowing a second portion of the mother liquor mixture, referred to as the secondary mother liquor stream, into a recycling pipe, wherein the recycling pipe intersects the first pipe at the mixture point.