A kind of pta production waste water comprehensive treatment reuse method

Abstract

The invention discloses a comprehensive treating and recycling method for PTA (purified terephthalic acid) production wastewater. According to the method, a primary filtration-extraction-ion exchange-reverse osmosis integrated process is adopted to treat the PTA production wastewater. The method comprises the following steps: the wastewater from a refining unit of a PTA device is subjected to primary filtration, and solid aromatic acid organic matters which are filtered out return to an oxidation unit for use; refined wastewater after filtration is subjected to extraction with a carboxylic acid alkyl ester extracting agent in a mixer, and extracted substances return to the oxidation unit for use; a raffinate phase enters an ion exchange system and is subjected to resin adsorption and ion exchange for recovery of a cobalt and manganese metal catalyst, and the recovered metal catalyst returns to the oxidation unit for use; finally, through two stages of reverse osmosis systems, penetrated water is taken as process water to return to the refining unit for use; a small amount of concentrate is sent to a sewage treatment system for treatment. The water treating and recycling rate reaches 70%-85%. The method has the advantages of little investment, low energy consumption, high wastewater treating and recycling rate and the like and has remarkable economic benefit.

Description

technical field [0001] The invention relates to a method for comprehensive treatment and reuse of PTA production wastewater. The wastewater comes from a refining unit of a purified terephthalic acid (PTA) production device, and belongs to the technical field of chemical production industrial water treatment. Background technique [0002] Purified Terephthalic Acid (PTA) is an important organic chemical raw material, mainly used in the production of polyethylene terephthalate (PET), and further production of synthetic resin, polyester fiber, etc. The typical production process of PTA is divided into two steps. The first step is the PX oxidation unit, which uses p-xylene (PX) as raw material, Co 2+ / Mn 2+ / Br - As a catalyst, acetic acid (HAC) as a solvent, PX reacts with oxygen in the air (reaction temperature 191~201°C, pressure 1.25~1.65MPa), and oxidizes to generate crude terephthalic acid (TA). The second step is the TA refining unit, which adds water to TA at high tem...

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Problems solved by technology

The above documents are all based on the combination process based on PX extraction. Although the reuse of treated water has been realized, there are the following disadvantages: ① PX is used as the extraction agent in the extraction process, which increases the consumption of raw material PX; ② The extraction agent PX If the dosage is too small (CN101544429B: PX / wastewater=1 / 5~1 / 10, wt), the extraction effect is not good; ③ a small amount of PX will be dissolved in the raffinate phase, and it is difficult to remove the extractant PX in the subsequent process, causing secondary pollution ; ④ A small amount of PX in the raffinate phase water is likely to cause damage to the reverse osmosis membrane

⑤ When the treated water is reused, a small amount of PX in the water will affect the hydrofining unit and affect the quality of PTA

Therefore, it is difficult to realize industrial large-scale PTA production wastewater treatment with the combined process mainly based on PX extraction.

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