Combined process for treatment of PTA (pure terephthalic acid) refined waste water

Abstract

A combined process for treatment of PTA (pure terephthalic acid) refined waste water comprises the following steps: firstly, aromatic acid in the PAT refined waste water is extracted in an extraction column by using para-xylene into an extract phase, and the extract phase is conveyed to an oxidation unit to serve as a reaction raw material; a raffinate phase is conveyed to a micro-filtration membrane separation device, so that solid suspension particles in the raffinate phase are removed; and a penetrating fluid enters a resin adsorption device and an ion exchange device, so that residual aromatic acid and metal ions in the penetrating fluid are removed, and treated water meets the water standard of a PAT refining unit. According to the method, the water and the aromatic acid therein are recycled, so as to reduce the unit consumption of products and water consumption, and bring remarkable economic benefits.

Description

technical field [0001] The invention belongs to the field of waste water treatment, and in particular relates to a treatment method for terephthalic acid refining waste water. technical background [0002] PTA is one of the important basic organic chemical raw materials, mainly used in the production of polyester fiber, polyester film and so on. The production of PTA generally uses p-xylene as a raw material, acetic acid as a solvent, catalytic oxidation at a certain temperature and pressure to generate crude terephthalic acid (TA), and then refined into high-purity PTA. In the TA hydrorefining process, a large amount of water needs to be used as the dissolving water of TA. After crystallization and centrifugal filtration, a large amount of waste water will be generated. The waste water contains the incompletely reacted intermediate product p-toluic acid (PT acid), P-carboxybenzaldehyde and its product terephthalic acid have the characteristics of high COD, low pH, many imp...

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Problems solved by technology

[0004] In recent years, there have been patent reports on the method of recycling useful components in wastewater in the process of treating PTA refining wastewater. CN102139970A discloses a method for recycling purified terephthalic acid production wastewater, which uses microfiltration-membrane extraction-resin adsorption The combined process treats the PTA refined wastewater to make the wastewater meet the water standard of the refining unit, but the unpretreated PTA refined wastewater contains more solid suspended particles, which makes the operating load of the microfiltration membrane larger and the operation cycle shorter; and in the membrane The extraction step needs to add an extraction accelerator, which will contain the accelerator in the treated water, and if it is reused, it will affect the purity of the product

CN101723531B provides a method for the treatment and reuse of purified terephthalic acid wastewater, using "neutralization + solid-liquid separation" as pre-membrane pretreatment, and adopting "ultrafiltration + two-stage reverse osmosis" double-membrane process for membrane treatment, so that the treated wastewater meets the water requirements of the refining unit of the production system, but the neutralization reaction of this process requires the addition of lye, which introduces more sodium ions, which increases the difficulty of subsequent treatment, and does not consider the reuse of aromatic acids. serious waste of resources

CN101544429B has introduced a kind of method of extraction-ultrafiltration-reverse osmosis combination treatment PTA refining wastewater, adopt p-xylene to extract the purified wastewater of purified terephthalic acid, the extraction phase is returned in the preparation process of purified terephthalic acid, and the raffinate phase After ultrafiltration and reverse osmosis treatment, the permeated water reaches the reuse standard. However, since the PX dissolved in the water is not treated in this method, returning to the system will affect the hydrogenation reaction and thus affect the product purity.

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