阅读说明：本技术 一种三氯蔗糖生产中三氯乙烷回收的方法 (Method for recovering trichloroethane in sucralose production ) 是由 杨志健 张正颂 付绪飞 于 2020-05-22 设计创作，主要内容包括：本发明涉及三氯蔗糖生产中三氯乙烷回收的方法,包括以下步骤：压滤除盐后的中和液送入分层器分层,分出水层入轻相槽,下层三氯乙烷层进入重相槽用泵连续送入三氯乙烷精馏塔,塔底物料用泵送至降膜蒸发器进行循环加热蒸发,气相进入塔底,由塔底上升与塔中进入的三氯乙烷进行换热后继续上升与塔顶回流进行换热后,从塔顶出来进入塔顶冷凝器进行两级冷凝得到三氯乙烷进入回流受槽,部分三氯乙烷用泵送至塔顶进行回流,部分采出至回收三氯乙烷受槽,得到纯度高达99.5%,水分小于500ppm的三氯乙烷成品直接返回氯化做溶剂。本发明与现有技术相比,三氯乙烷回收效率高,回收过程简单,同时大大降低了废水的产生量,节约蒸汽消耗,降低了生产成本,减少了污染。(The invention relates to a method for recovering trichloroethane in sucralose production, which comprises the following steps: delivering the neutralized liquid after filter pressing and desalting into a delayer for layering, separating a water layer into a light phase tank, allowing a lower trichloroethane layer to enter a heavy phase tank and continuously delivering the lower trichloroethane layer into a trichloroethane rectifying tower by using a pump, delivering materials at the bottom of the tower to a falling film evaporator for cyclic heating and evaporation, allowing a gas phase to enter the bottom of the tower, continuously ascending the tower after heat exchange with the trichloroethane entering the tower, performing heat exchange with reflux at the top of the tower, allowing the materials to exit from the top of the tower, performing two-stage condensation to obtain trichloroethane, delivering the trichloroethane to a reflux receiving tank, delivering part of the trichloroethane to the top of the tower for reflux, and partially extracting the trichloroethane to a recovered trichloroethane receiving tank to obtain a trichloroethane finished product with the purity of 99. Compared with the prior art, the method has the advantages of high trichloroethane recovery efficiency, simple recovery process, greatly reduced wastewater generation amount, saved steam consumption, reduced production cost and reduced pollution.)

1. A method for recovering trichloroethane in sucralose production comprises a chlorination neutralization step, and is characterized in that:

a. removing ammonium chloride salt from the chlorination neutralized liquid obtained in the chlorination neutralization step through a filter press;

b. feeding the chlorination neutralization solution subjected to filter pressing and desalting into a continuous layering device for layering, wherein the obtained upper light phase water layer enters a light phase tank, and the lower trichloroethane layer enters a heavy phase tank;

c. the trichloroethane heavy phase is continuously sent into a rectifying tower by a pump, the circulating material accumulated at the bottom of the rectifying tower is sent to a reboiler by a circulating pump for circulating heating evaporation, the gas phase produced by the reboiler returns to the lower part of the rectifying tower, the gas phase is subjected to heat exchange with the circulating material, then rises from the bottom of the tower to exchange heat with the trichloroethane heavy phase entering the tower, then continues to rise to enter a condenser at the top of the tower for condensation, and the gas phase is condensed to form trichloroethane liquid to enter a reflux tank;

d. part of trichloroethane liquid in the reflux tank is sent to the top of the rectifying tower by a reflux pump to carry out reflux, after the heat exchange is carried out between the refluxed trichloroethane liquid and the rising gas phase in the rectifying tower, the trichloroethane liquid falls back to the bottom of the tower to enter a reboiler for cyclic evaporation, and the gas phase after the heat exchange enters a condenser at the top of the tower to be condensed;

e. and extracting the residual trichloroethane liquid in the reflux tank to a trichloroethane finished product recovery tank to obtain a trichloroethane finished product with the purity of 99.5 percent and the water content of less than 500ppm, and directly returning the trichloroethane finished product to a chlorination working section to be used as a solvent.

2. The method for recovering the trichloroethane during the production of the sucralose according to claim 1, wherein the trichloroethane heavy phase is continuously pumped into a feeding port at the middle part of the rectifying tower, the lower part of the rectifying tower is connected with a gas phase outlet of a reboiler, a liquid phase inlet of the reboiler is connected to the bottom part of the rectifying tower through a circulating pump, and the circulating material at the lower part of the rectifying tower is subjected to forced evaporation circulation.

3. The method for recovering the trichloroethane during the production of the sucralose according to claim 1 or 2, wherein the gas phase trichloroethane is condensed to 0-5 ℃ by a condenser at the top of the rectifying tower to form liquid.

4. The method for recovering the trichloroethane during the production of the sucralose according to claim 3, wherein the condenser arranged at the top of the rectifying tower is a secondary condenser, the primary condenser condenses the gaseous phase of the trichloroethane to 25-30 ℃ by using circulating water, and the secondary condenser condenses the gaseous phase of the trichloroethane to 0-5 ℃ by using chilled water to become a liquid phase.

5. The method of claim 1, wherein the reflux liquid is pure trichloroethane, the purity is up to 99.5%, and the water content is less than 500 ppm.

6. The method of claim 1, wherein the reflux trichloroethane liquid: the total amount of trichloroethane liquid in the reflux tank is 1: 1-10.

7. The method for recovering the trichloroethane during the production of the sucralose according to claim 1 or 2, wherein the reboiler is a falling film evaporator.

Technical Field

The invention belongs to the technical field of chemical industry, and particularly relates to a method for recovering trichloroethane in sucralose production.

Background

Sucralose is a fresh sweetener, the sweetness of which is 800 times of that of sucrose, and the sweetness of which is pure and similar to that of sucrose, and sucralose is not absorbed by human body, has no bioaccumulation and high safety, so that the sucralose industry is rapidly developed in this year, production enterprises are gradually increased, and the yield is continuously improved. A large amount of trichloroethane is used as a solvent for chlorination reaction in the production process of sucralose, the using amount of trichloroethane is increased along with the increase of yield, the recovery and the recycling of the trichloroethane are inevitably generated in the existing production process, the traditional recovery method is to distill and desolventize chlorinated neutralization solution at one time, the trichloroethane is separated by layers after the desolventization is finished, the trichloroethane contains a great amount of impurities, the pure water is needed for washing, then the rectification and dehydration are needed to be continued, the operation process is complex, and the washing and the multiple evaporation are needed.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provide the method for recovering the trichloroethane in the production of the sucralose, which has the advantages of simple operation, high efficiency, high recovery rate and low cost.

In order to achieve the purpose, the invention adopts the following technical scheme:

a method for recovering trichloroethane in sucralose production comprises a chlorination neutralization step, and is characterized in that:

a. removing ammonium chloride salt from the chlorination neutralized liquid obtained in the chlorination neutralization step through a filter press;

b. feeding the chlorination neutralization solution subjected to filter pressing and desalting into a continuous layering device for layering, wherein the obtained upper light phase water layer enters a light phase tank, and the lower trichloroethane layer enters a heavy phase tank;

c. the trichloroethane heavy phase is continuously sent into a rectifying tower by a pump, circulating materials accumulated at the bottom of the rectifying tower are sent to a reboiler by the pump for circulating heating evaporation, gas phase (comprising trichloroethane, water and DMF) produced by the reboiler returns to the lower part of the rectifying tower, the gas phase is subjected to heat exchange with the circulating materials, then rises from the bottom of the tower to exchange heat with the trichloroethane heavy phase entering the tower, then continues to rise to enter a two-stage condenser at the top of the tower for two-stage condensation, and trichloroethane liquid is formed after the gas phase is condensed and enters a reflux tank;

d. part of trichloroethane liquid in the reflux tank is pumped to the top of the rectifying tower to carry out reflux, after the heat exchange is carried out between the refluxed trichloroethane liquid and the rising gas phase in the rectifying tower, the trichloroethane liquid falls back to the bottom of the tower to enter a reboiler for cyclic evaporation, and the gas phase after the heat exchange enters a two-stage condenser at the top of the tower to carry out two-stage condensation;

e. and extracting the residual trichloroethane liquid in the reflux tank to a trichloroethane finished product recovery tank to obtain a trichloroethane finished product with the purity of 99.5 percent and the water content of less than 500ppm, and directly returning the trichloroethane finished product to a chlorination working section to be used as a solvent.

The further technical scheme is that the trichloroethane heavy phase is continuously fed into a feeding port in the middle of the rectifying tower by a pump, the lower portion of the rectifying tower is connected with a gas phase outlet of a reboiler, a liquid phase inlet of the reboiler is connected to the bottom of the rectifying tower through a circulating pump, and forced evaporation circulation is carried out on circulating materials at the lower portion of the rectifying tower.

The further technical proposal is that the gas phase trichloroethane is condensed to 0-5 ℃ by a secondary condenser at the tower top to form liquid.

The further technical scheme is that the condenser arranged at the top of the tower is a secondary condenser, the primary condenser condenses the trichloroethane gas phase to 25-30 ℃ by adopting circulating water, and the secondary condenser condenses the trichloroethane gas phase to 0-5 ℃ by adopting chilled water to become a liquid phase.

The further technical scheme is that the reflux liquid is pure trichloroethane, the purity reaches 99.5%, and the moisture is less than 500 ppm. The reflux liquid is used for controlling the gas phase temperature at the top of the tower, so that the purity of the trichloroethane discharged from the tower meets the requirement.

The further technical proposal is that the reflux tank refluxes trichloroethane liquid: the reflux ratio of the total trichloroethane liquid in the reflux tank is 1: 1-10.

The further technical proposal is that the reboiler adopts a falling film evaporator.

Compared with the prior art, the method has the advantages that partial salt is removed by filter pressing, the trichloroethane is rectified and separated after layering, the finished trichloroethane with high purity and low moisture can be obtained by a rectification method, and can be directly applied to chlorination production.

Drawings

FIG. 1 is a process flow diagram of the process of the present invention;

fig. 2 is a schematic structural view of the rectifying column of fig. 1 connected with related equipment.

Detailed Description

To explain technical contents, structural features, achieved objects and effects of the technical solutions in detail, the following detailed description is given with reference to the accompanying drawings in combination with the specific embodiments.