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Method for recovering dilute acetic acid based on extraction/azeotropic distillation coupling process

A technology of azeotropic rectification and azeotropic rectification column is applied in the field of recovering dilute acetic acid based on the extraction/azeotropic rectification coupling process, which can solve the problems of complex process flow, increase entrainer, increase system energy consumption, etc. The effect of low energy consumption, reduced energy consumption, and reduced solvent circulation

Inactive Publication Date: 2019-08-23
EAST CHINA UNIV OF SCI & TECH
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Problems solved by technology

However, when the content of acetic acid in acetic acid wastewater is low, the amount of entrainer needs to be increased, which increases the energy consumption of the system
[0004] Chinese patent CN102267889 has reported a kind of extraction-azeotropic rectification coupled technological process, selected solvents such as n-butyl acetate, isobutyl acetate, isopropyl acetate and n-propyl acetate and their mixtures etc. from the bottom of the extraction tower Added, but the whole process is more complicated, and the feed needs to be added separately from the extraction tower and the azeotropic distillation tower

Method used

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  • Method for recovering dilute acetic acid based on extraction/azeotropic distillation coupling process

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Experimental program
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Embodiment 1

[0021] The specific flow chart of embodiment sees figure 1 . The material composition of this embodiment is based on mass fraction.

[0022] The flow rate of stream 1 is 5000 kg / h, the mass fraction of acetic acid is 30%, the mass fraction of water is 70%, the feed temperature is 40 °C, and the feed is fed from the top of the extraction tower T1. The extraction tower T1 is a packed tower with a diameter of 0.8 m, an operating temperature of 40°C, and operating under normal pressure, with a theoretical plate number of 26. The flow rate of stream 8 is 5403 kg / h, wherein the mass fraction of isopropyl acetate is 76.9%, the mass fraction of isopropanol is 19.2%, and the mass fraction of water is 3.9%. The feed position of logistics 2 is the 14th theoretical plate, the flow rate is 6724 kg / h, the mass fraction of water is 10%, the mass fraction of acetic acid is 22%, the mass fraction of isopropyl acetate is 61%, isopropanol The mass fraction is 7%. The mass flow rate of stream...

Embodiment 2

[0025] Keep the operating conditions of extraction tower T1 and solvent recovery tower T3 constant as embodiment 1, the reflux ratio of azeotropic rectification tower T2 is 1.4, other operating conditions are constant, change the content of isopropyl acetate and isopropanol in the extractant Ratio, the mass fraction of isopropyl acetate is 95%, and the mass fraction of isopropanol is 5%. The recovery rate of acetic acid after the separation of the whole process flow is 97%. The mass flow rate of acetic acid product stream 5 is 1461.26 kg / h, and the mass fraction of acetic acid is 99.8%. The mass flow rate of waste water stream 10 is 3539 kg / h, and the mass fraction of water is 99%.

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Abstract

The present invention relates to a process for recovering dilute acetic acid through extraction / azeotropic distillation coupling using a mixture of isopropyl acetate and isopropyl alcohol as a solvent. In this method, isopropyl acetate and isopropyl alcohol act as both extractants in an extraction column and azeotropic agent in an azeotropic distillation column. At first, that low-concentration acetic acid waste water and the solvent are contacted in the extraction column in a counter-current to generate liquid-liquid extraction. The extractive phase rich in acetic acid is sent to the azeotropic distillation column to obtain a high purity acetic acid product at the bottom of the azeotropic distillation column. The water-rich raffinate is fed to the top of the solvent recovery column for solvent recovery. The products at the top of azeotropic distillation tower and solvent recovery tower are sent to a phase separator for liquid-liquid phase separation, the organic phase is sent back tothe bottom of extraction tower for circulation, and the aqueous phase is sent to the solvent recovery tower. The invention uses the liquid-liquid extraction method for carrying out the pre-concentration operation, and the energy consumption is greatly reduced; at that same time, isopropyl acetate and isopropyl alcohol are adopted as a mixed solvent to reduce the circulating amount of the solvent,thereby reducing the equipment investment and further reducing the energy consumption. The invention has the characteristics of high separation efficiency and high recovery rate.

Description

technical field [0001] The invention relates to a method for recovering dilute acetic acid based on an extraction / azeotropic rectification coupling process, which belongs to a chemical separation process and is suitable for recovery of acetic acid in low-concentration acetic acid wastewater. Background technique [0002] Acetic acid is one of the most common organic acids and is widely used in industrial production processes as a solvent or a reactant. For example, in the production of terephthalic acid from the oxidation of p-xylene, it acts as a solvent for the reaction. At the same time, it is also an important raw material in organic synthesis industries such as acetic anhydride and aspirin. During the use of acetic acid, dilute acetic acid wastewater is usually produced, and the "National Industry Discharge Standard" stipulates that the content of acetic acid in wastewater discharge should be less than 2% (mass percentage), so the recovery of acetic acid in acetic acid...

Claims

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Application Information

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IPC IPC(8): C07C51/42C07C51/46C07C51/48C07C53/08
CPCC07C51/42C07C51/46C07C51/48C07C53/08
Inventor 曾作祥方鹏励沈劢尚梅华倩薛为岚金星宇
Owner EAST CHINA UNIV OF SCI & TECH
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