PTA production method and system with low energy consumption, material consumption and less waste discharge

Abstract

The invention relates to a Purified Terephthalic Acidproduction method with low energy consumption, low material consumption and low refuse discharge. The PTA production method comprises the following steps: tail gas of an oxidation reactor is outputted and passes through by-product steam of a first stage steam generator and is sent to an acetic acid regeneration tower for recycling acetic acid; a refined mother liquor is returned to the acetic acid regeneration tower, the original vacuum filtration filter is replaced by a pressure filter, and filter cakes are directly pulped and supplied to a refining section; through recovered acetic acid recovery extraction, an oxidized mother liquor is processed by extraction, and an acetic acid methyl ester removed tower top backflow liquid of the acetic acid regeneration tower is used for oxidizing, washing filter cakes of the refining section and blending slurries of the refining section. The method and system provided by the invention can effectively control acetic acid consumption in tail gas and waste water, recycle organic matters of the refined mother liquid, realize reuse of water, reduce consumption of steam and electric energy, reduce refuse discharge, and also can supply benzoic acid, mixed phthalic acids and other by-products. The invention has the advantages of short process flow, good operationality, low production cost and low apparatus investment.

Description

technical field [0001] The invention relates to a PTA production method. Compared with the traditional PTA production method, the consumption of raw materials, process solvents, catalysts and steam is significantly reduced, and is a novel PTA production process with low energy consumption and low material consumption. Background technique [0002] Purified Terephthalic Acid (PTA) is the main raw material for the production of polyester fibers and resins. It is a non-toxic and odorless white crystal or powder at room temperature. It is an important bulk chemical product and is closely related to people's daily life. [0003] At present, PTA is mainly produced by the air oxidation method of p-xylene (p-Xylene, referred to as PX). The process mainly includes two stages of oxidation and refining, and forms a complete process system with supporting processes such as oxidation mother liquor treatment and oxidation tail gas treatment. figure 2 Is a flowchart of an embodiment of the...

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Problems solved by technology

[0017] (2) The energy consumption of the dehydration system is high

However, since the relative volatility of acetic acid and water is close to 1, azeotropic distillation is generally used for dehydration. The removal of water requires 1.4-2.0t of water vapor per ton, and the energy consumption of steam is high, resulting in high energy consumption of the device.

[0018] (3) High energy consumption in the oxidation mother liquor removal process

In order to control the quality of PTA products, it is necessary to take out part of the oxidized mother liquor to remove the impurities in the mother liquor. The mother liquor is first concentrated by the acetic acid stripping tower, and then the acetic acid is further recovered by the thin film evaporator. The thin film evaporator needs to consume external high-pressure steam to heat, increasing the steam consumption of the device by 0.03t / tPTA

[0019] (4) Oxidation residues are not effectively utilized

[0020] (5) The refined mother liquor has not been effectively recycled

Refined mother liquor is usually treated by first flash cooling to 101°C, then cooling to about 45°C, and then filtering. The filtrate is directly discharged to the sewage station in the form of refined wastewater, and the discharged refined wastewater is equivalent to 2-3t / tPTA. Water also contains acetic acid of 300-600ppm (mass concentration), PT acid of 300-600ppm, 4-CBA of 10ppmw and TA of 200-500ppmw; Scaling in equipment and pipelines will seriously affect the continuous operation of the device. At the same time, the loss of PT acid will be caused during the cleaning process, equivalent to PX consumption of about 0.5kg / tPTA

There are also Chinese patents CN201210382308.8 and CN201210428330.1 respectively proposing to use adsorption ion exchange and extraction methods to recover organic matter, the cost of wastewater reuse is relatively high, and it is difficult to actually operate

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