Recovery method of terephthalic acid/isophthalic acid refinement mother liquor

Abstract

The invention discloses a recycling method of mother liquor, particularly a method for recycling refined mother liquor of phthalic acid / m-phthalic acid. The method comprises the steps: the mother liquor in a mother liquor tank is pumped into a mother liquor cooling tank, and the cooling tank is vacuumized, the air after flash evaporation is pumped into a cooler, after condensation, the gas returns back to the mother liquor cooling tank; the mother liquor after cooling in the mother liquor cooling tank is pumped into a filter for filtering; after filtering of the mother liquor, the filtering liquor is put into a filtering liquor collecting tank and then pumped into an incinerator for tail gas drenching; after a filter cake is formed on the inner surface of the filter element of the filter, the filtering liquor at the upper part of the tube plate of the filter is discharged; the filtering liquor at the inner lower side of the filter element and lower part of the tube plate of the filter is discharged to a buffer tank; the filter cake blow-dried by oxydic tail gas is pressed into a pulping tank; and deionized water is added into the filter to wash the undischarged filter cake to the pulping tank. By adopting filtering technology with high accuracy, the method recovers the useful components in the centrifuger mother liquor, reduces the values of solidity and chemical oxygen demand (COD) of filtering liquor, and improves the environment.

Description

technical field [0001] The invention relates to a method for recovering mother liquor, in particular to a method for recovering mother liquor for refining terephthalic acid / isophthalic acid. Background technique [0002] The purified terephthalic acid (PTA) unit of the Polyester Division of Yanshan Petrochemical Company was built in the late 1970s by introducing the patented technology of the American Amoco Company, with a design capacity of 36,000 tons per year. In 1997, the original terephthalic acid plant tried to produce isophthalic acid. In 1998, it officially switched to producing isophthalic acid. The design capacity is 25,000 tons / year. [0003] The purpose of the hydrogenation reaction in the refining unit of the isophthalic acid plant is to remove harmful impurities in the crude isophthalic acid (CIA) in the oxidation unit, so that the quality of the final product can reach the specified standard. The impurities in CIA are mainly the intermediates and side reactio...

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Problems solved by technology

Considering the production process of (isophthalic acid / terephthalic acid) PIA / PTA, it will not be the most economical and reasonable to return to the oxidation unit if the mother liquor in the centrifuge of the hydrofining unit / p-toluic acid content is not high In addition, if returning to the oxidation unit, it is necessary to adjust the ratio of the materials in the oxidation batching system accordingly, and the instability of the mother liquor recovery system will directly affect the normal operation of the oxidation batching system, the process is complicated, and it is not conducive to the stability of the oxidation unit run

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