阅读说明：本技术 醋酸浓缩的压缩式热泵精馏方法及其系统 (Compression type heat pump rectification method for acetic acid concentration and system thereof ) 是由 蒋俊彦 史少君 周岳 高卓鹏 李靖 李想 邹献奎 于 2019-10-12 设计创作，主要内容包括：一种醋酸浓缩的压缩式热泵精馏方法,包括：醋酸溶液从精馏塔中部进料,精馏塔对醋酸溶液进行精馏浓缩；精馏塔的一部分塔釜液作为塔底产品从精馏塔排出,另一部分塔釜液从精馏塔进入塔底再沸器；精馏塔的塔顶气体进入压缩机,经压缩机压缩升温后的蒸汽直接进入塔底再沸器,对进入塔底再沸器的塔釜液加热,蒸汽被冷凝,被加热的塔釜液回流到塔釜；蒸汽冷凝后的冷凝液进入回流罐中,一部分冷凝液作为塔顶产品从回流罐排出,另一部分冷凝液作为回流从回流罐返回到精馏塔的塔顶。本发明还公开了一种醋酸浓缩的压缩式热泵精馏系统。采用上述技术方案后,达到了以较低的成本实现节约能耗的目的。(A compression heat pump rectification method for acetic acid concentration comprises the following steps: feeding an acetic acid solution from the middle part of a rectifying tower, and rectifying and concentrating the acetic acid solution by the rectifying tower; discharging a part of tower bottom liquid of the rectifying tower as a tower bottom product from the rectifying tower, and feeding the other part of tower bottom liquid into a tower bottom reboiler from the rectifying tower; the tower top gas of the rectifying tower enters a compressor, the steam compressed and heated by the compressor directly enters a tower bottom reboiler, tower bottom liquid entering the tower bottom reboiler is heated, the steam is condensed, and the heated tower bottom liquid flows back to the tower bottom; and (3) feeding the condensate after the steam condensation into a reflux tank, discharging a part of the condensate as a product at the top of the reflux tank, and returning the other part of the condensate as reflux from the reflux tank to the top of the rectifying tower. The invention also discloses a compression type heat pump rectification system for acetic acid concentration. After the technical scheme is adopted, the purpose of saving energy consumption with lower cost is achieved.)

1. A compression type heat pump rectification method for acetic acid concentration is characterized by comprising the following steps:

Feeding an acetic acid solution from the middle part of a rectifying tower, and rectifying and concentrating the acetic acid solution by the rectifying tower;

discharging a part of tower bottom liquid of the rectifying tower as a tower bottom product from the rectifying tower, and feeding the other part of tower bottom liquid into a tower bottom reboiler from the rectifying tower;

the tower top gas of the rectifying tower enters a compressor, the steam compressed and heated by the compressor directly enters the tower bottom reboiler, the tower bottom liquid entering the tower bottom reboiler is heated, the steam is condensed, and the heated tower bottom liquid flows back to the tower bottom;

and (3) feeding the condensate after the steam condensation into a reflux tank, discharging a part of the condensate as a tower top product from the reflux tank, and returning the other part of the condensate as reflux from the reflux tank to the tower top of the rectifying tower.

2. The compression heat pump distillation method for acetic acid concentration as claimed in claim 1, wherein the operating pressure of the distillation column is 0.1-0.4MPa, the temperature at the top of the distillation column is 100-120 ℃, the temperature at the bottom of the distillation column is 130-150 ℃, and the reflux ratio is 2.0-8.0.

3. A compression heat pump distillation process of acetic acid concentration as recited in claim 1 wherein the compressor is a screw compressor.

4. the compression heat pump distillation method for acetic acid concentration as claimed in claim 3, wherein the inlet temperature of the screw compressor is 100-120 ℃, the inlet pressure is 0.1-0.2 MPa, the outlet temperature is 135-155 ℃, and the outlet pressure is 0.3-0.6 MPa.

5. A compression heat pump rectification method for acetic acid concentration according to claim 1, 3 or 4, characterized in that the inlet pressure and the outlet pressure of the compressor are respectively detected in real time when the compressor compresses the overhead gas, and the inlet pressure and the outlet pressure of the compressor are maintained stable by controlling the flow rate of the water vapor flowing to the inlet and the outlet of the compressor.

6. A compression heat pump rectification system for acetic acid concentration comprises a rectification tower, a tower bottom reboiler and a reflux tank; the top of the rectifying tower is provided with a gas phase outlet and a reflux port, the middle of the rectifying tower is provided with a raw material inlet, and the bottom of the rectifying tower is provided with a liquid outlet and a liquid inlet; the compression type heat pump rectification system for acetic acid concentration is characterized by comprising a compressor, wherein the compressor is arranged at the top of a rectification tower, and an inlet of the compressor is communicated with a gas-phase outlet of the rectification tower;

A hot end inlet of the tower bottom reboiler is communicated with an outlet of the compressor, and a hot end outlet of the tower bottom reboiler is communicated with an inlet of the reflux tank; a cold end inlet of the tower bottom reboiler is communicated with a liquid outlet of the rectifying tower, and a cold end outlet of the tower bottom reboiler is communicated with a liquid inlet of the rectifying tower;

The reflux tank is communicated with a reflux opening of the rectifying tower, and is used for discharging a part of liquid as a tower top product from the reflux tank, and returning the other part of liquid as reflux to the rectifying tower.

7. The acetic acid-concentrating, compression-type heat pump rectification system of claim 6, comprising a first regulating valve, a second regulating valve, a first pressure transmitter, a second pressure transmitter, and a controller;

An inlet of the first regulating valve and an inlet of the second regulating valve are respectively communicated with a water vapor pipeline, an outlet of the first regulating valve is communicated with an inlet of the compressor, and an outlet of the second regulating valve is communicated with an outlet of the compressor;

the first pressure transmitter is used for detecting the inlet pressure of the compressor, and the second pressure transmitter is used for detecting the outlet pressure of the compressor;

The controller is used for receiving valve state signals fed back by the first regulating valve and the second regulating valve and detection results sent by the first pressure transmitter and the second pressure transmitter, and controlling the opening degree of the first regulating valve and the second regulating valve so as to regulate the flow of the water vapor flowing into the inlet and the outlet of the compressor and maintain the inlet pressure and the outlet pressure of the compressor stable.

8. A compression heat pump rectification system with acetic acid concentration according to claim 6 or claim 7 wherein the compressor is a screw compressor.

9. The compression heat pump rectification system for acetic acid concentration according to claim 6, wherein the rectification column is a plate column or a packed column.

Technical Field

The invention relates to a rectification technology for acetic acid concentration.

Background

acetic acid is an important solvent, and is generally used as a solvent for the reaction in the process of producing terephthalic acid by oxidizing p-xylene. The oxidation reaction of p-xylene produces a large amount of water, resulting in dilution of the acetic acid solvent. In order to maintain the concentration of acetic acid in the aqueous acetic acid solution, the acetic acid is usually concentrated by distillation.

the boiling point of acetic acid is 118 ℃ and the boiling point of water is 100 ℃ under normal pressure, the relative volatility of an acetic acid-water system is low, and the acetic acid has strong association effect, so that the conventional rectification needs more tower plates and higher reflux ratio, and the energy consumption is higher. In order to save energy, the separation of acetic acid and water is realized by adopting an azeotropic distillation method in some processes, and the azeotropic agent is usually acetate. Although azeotropic distillation can reduce energy consumption, the acetate ester entrainer is expensive and is a flammable medium, thereby increasing the additional cost of separation. There are also processes that use multi-effect pump rectification or multi-effect heat pump rectification, but both of these approaches result in a substantial increase in equipment investment.

disclosure of Invention

The invention aims to provide a compression type heat pump rectification method and a compression type heat pump rectification system for acetic acid concentration, which reduce the energy consumption of acetic acid in the concentration process and have low implementation cost.

in order to solve the above technical problems, according to an aspect of the present invention, there is provided a compression heat pump rectification method for acetic acid concentration, comprising the steps of:

feeding an acetic acid solution from the middle part of a rectifying tower, and rectifying and concentrating the acetic acid solution by the rectifying tower;

Discharging a part of tower bottom liquid of the rectifying tower as a tower bottom product from the rectifying tower, and feeding the other part of tower bottom liquid into a tower bottom reboiler from the rectifying tower;

The tower top gas of the rectifying tower enters a compressor, the steam compressed and heated by the compressor directly enters a tower bottom reboiler, tower bottom liquid entering the tower bottom reboiler is heated, the steam is condensed, and the heated tower bottom liquid flows back to the tower bottom;

And (3) feeding the condensate after the steam condensation into a reflux tank, discharging a part of the condensate as a product at the top of the reflux tank, and returning the other part of the condensate as reflux from the reflux tank to the top of the rectifying tower.

According to another aspect of the invention, a compression type heat pump rectification system for acetic acid concentration is provided, which comprises a rectification tower, a tower bottom reboiler and a reflux tank; the top of the rectifying tower is provided with a gas phase outlet and a reflux port, the middle of the rectifying tower is provided with a raw material inlet, and the bottom of the rectifying tower is provided with a liquid outlet and a liquid inlet; the compression type heat pump rectification system for acetic acid concentration is characterized by comprising a compressor, wherein the compressor is arranged at the top of a rectification tower, and an inlet of the compressor is communicated with a gas-phase outlet of the rectification tower; the hot end inlet of the tower bottom reboiler is communicated with the outlet of the compressor, and the hot end outlet of the tower bottom reboiler is communicated with the inlet of the reflux tank; a cold end inlet of the tower bottom reboiler is communicated with a liquid outlet of the rectifying tower, and a cold end outlet of the tower bottom reboiler is communicated with a liquid inlet of the rectifying tower; the reflux tank is communicated with a reflux opening of the rectifying tower, and is used for discharging a part of liquid as a tower top product from the reflux tank, and returning the other part of liquid as reflux to the rectifying tower.

After the technical scheme is adopted, the invention has the following advantages:

1. The embodiment of the invention is additionally provided with the compressor on the basis of the existing acetic acid concentration rectifying tower, the compressor is used as a heat pump for pressurizing gas at the tower top, the compressor is used for directly compressing steam at the tower top, the pressure and the temperature of the steam at the tower top are greatly improved, and the pressurized steam at the tower top is used for directly supplying heat to a reboiler at the tower bottom of the rectifying tower, so that the aim of saving energy consumption with lower cost is fulfilled;

2. According to the embodiment of the invention, the inlet pressure and the outlet pressure of the compressor are controlled, so that the temperature of steam entering the tower bottom reboiler after being compressed and heated by the compressor can be kept stable, the concentration of an acetic acid product is also kept stable, and the quality of the rectified acetic acid product is ensured.

Drawings

Fig. 1 shows a schematic configuration diagram of an embodiment of a compression heat pump rectification system for acetic acid concentration according to the invention.

figure 2 shows a schematic block diagram of the pressure control system of an embodiment of a compression heat pump rectification system for acetic acid concentration according to the present invention.

Detailed Description

The invention is described in detail below with reference to the figures and specific embodiments.

Fig. 1 shows a schematic configuration diagram of an embodiment of a compression heat pump rectification system for acetic acid concentration according to the invention. Referring to fig. 1, a compression heat pump distillation system for acetic acid concentration according to an embodiment of the present invention includes a distillation column 1, a tower bottom reboiler 2, a reflux drum 3, and a compressor 4.

the top of the rectifying tower 1 is provided with a gas phase outlet and a reflux port, the middle part of the rectifying tower 1 is provided with a raw material inlet, and the bottom of the rectifying tower 1 is provided with a liquid outlet and a liquid inlet. The compressor 4 is arranged at the top of the rectifying tower 1, and the inlet of the compressor 4 is communicated with the gas-phase outlet of the rectifying tower 1.

A hot end inlet of the tower bottom reboiler 2 is communicated with an outlet of the compressor 4, and a hot end outlet of the tower bottom reboiler 2 is communicated with an inlet of the reflux tank 3; the cold end inlet of the tower bottom reboiler 2 is communicated with the liquid outlet of the rectifying tower 1, and the cold end outlet of the tower bottom reboiler 2 is communicated with the liquid inlet of the rectifying tower 1.

the reflux tank 3 is communicated with a reflux port of the rectifying tower 1, the reflux tank 3 is used for discharging a part of liquid as a tower top product from the reflux tank 3, and the other part of liquid returns to the rectifying tower 1 as reflux.

In this embodiment, the rectifying column 1 may be a plate column or a packed column, and is preferably a plate column. The plate number of the plate tower is 50-140. The compressor 4 is a screw compressor.

Please refer to fig. 2. Preferably, a compression heat pump rectification system for acetic acid concentration according to an embodiment of the present invention includes a first regulating valve 51, a second regulating valve 52, a first pressure transmitter 61, a second pressure transmitter 62 and a controller 7.

an inlet of the first regulating valve 51 and an inlet of the second regulating valve 52 are respectively communicated with the steam line 8, an outlet of the first regulating valve 51 is communicated with an inlet of the compressor 4, and an outlet of the second regulating valve 52 is communicated with an outlet of the compressor 4.

The first pressure transmitter 61 is used to detect the inlet pressure of the compressor 4 and the second pressure transmitter 62 is used to detect the outlet pressure of the compressor 4.

The controller 7 is configured to receive the valve state signals fed back by the first and second regulating valves 51 and 52 and the detection results sent by the first and second pressure transmitters 61 and 62, and control the opening degrees of the first and second regulating valves 51 and 52 to regulate the flow rates of the water vapor flowing into the inlet and the outlet of the compressor 4, so as to maintain the inlet pressure and the outlet pressure of the compressor 4 stable. The controller 7 may be a PLC controller.

In this embodiment, the controller 7 is configured to perform PID adjustment or PI adjustment on the opening of the first regulating valve 51 according to a difference between an inlet pressure set value and an inlet pressure detection value, so as to stabilize the inlet pressure of the compressor 4 at the inlet pressure set value, and perform PID adjustment or PI adjustment on the opening of the second regulating valve 52 according to a difference between an outlet pressure set value and an outlet pressure detection value, so as to stabilize the outlet pressure of the compressor 4 at the outlet pressure set value, thereby coping with system operation fluctuation, so that the pressure and temperature of steam entering the tower bottom reboiler 2 after being compressed and heated by the compressor 4 can be kept stable, further the concentration of an acetic acid product can be kept stable, and the quality of the rectified acetic acid product can be ensured.

According to one embodiment of the invention, the compression type heat pump rectification method for acetic acid concentration comprises the following steps:

Feeding an acetic acid solution from the middle part of a rectifying tower 1, and rectifying and concentrating the acetic acid solution by the rectifying tower 1;

Discharging a part of tower bottom liquid of the rectifying tower 1 as a tower bottom product from the rectifying tower 1, and feeding the other part of tower bottom liquid into a tower bottom reboiler 2 from the rectifying tower 1;

the gas at the top of the rectifying tower 1 enters a compressor 4, the steam compressed and heated by the compressor 4 directly enters a tower bottom reboiler 2, tower bottom liquid entering the tower bottom reboiler 2 is heated, the steam is condensed, and the heated tower bottom liquid flows back to the tower bottom;

And (3) feeding the condensate after the steam condensation into a reflux tank 3, discharging a part of the condensate as a tower top product from the reflux tank 3, and returning the other part of the condensate as reflux from the reflux tank 3 to the tower top of the rectifying tower 1.

Optionally, the operation pressure of the rectifying tower 1 is 0.1-0.4MPa, the tower top temperature is 100-120 ℃, the tower bottom temperature is 130-150 ℃, and the reflux ratio is 2.0-8.0.

Alternatively, the compressor 4 is a screw compressor. The inlet temperature of the screw compressor is 100-120 ℃, the inlet pressure is 0.1-0.2 MPa, the outlet temperature is 135-155 ℃, and the outlet pressure is 0.3-0.6 MPa. The compressor 4 can greatly increase the pressure and temperature of the steam.

the compressor 4 can be supplemented with steam according to the requirements of working conditions. When the compressor 4 compresses the tower top gas, the inlet pressure and the outlet pressure of the compressor 4 are respectively detected in real time, and the inlet pressure and the outlet pressure of the compressor 4 are kept stable by controlling the flow of the water vapor flowing to the inlet and the outlet of the compressor 4.

The following describes a specific flow and implementation steps of a compression heat pump rectification method for acetic acid concentration according to an embodiment of the present invention with reference to fig. 1 and a specific application example.

and a dilute acetic acid stream S1 with the acetic acid mass concentration of 40% enters the rectifying tower from the middle part of the rectifying tower 1, and after the dilute acetic acid stream S1 is concentrated in the rectifying tower 1, the mass concentration of acetic acid discharged from the top of the tower is lower than 0.1%, and the mass concentration of acetic acid discharged from the bottom of the tower is higher than 90%. The temperature of the bottom of the rectifying tower 1 is 130 ℃, the temperature of the top of the tower is 100 ℃, the operating pressure of the top of the tower is 0.11MPa, the operating pressure of the bottom of the tower is 0.19MPa, the reflux ratio of the top of the tower is 4.2, and the reflux ratio of the bottom of the tower is 6.5.

The steam at the top of the tower directly enters the compressor 4, the compressor 4 compresses the steam at the top of the tower, the temperature and the pressure of the steam are improved, the temperature of the steam at the outlet of the compressor is 135 ℃, and the outlet pressure is 0.35 MPa. The inlet and the outlet of the compressor 4 are both connected with a steam stream S2, the controller 7 performs PID adjustment or PI adjustment on the opening degree of the first regulating valve 51 according to the difference between the inlet pressure set value and the inlet pressure detection value to stabilize the inlet pressure of the compressor 4 at the inlet pressure set value, and performs PID adjustment or PI adjustment on the opening degree of the second regulating valve 52 according to the difference between the outlet pressure set value and the outlet pressure detection value to stabilize the outlet pressure of the compressor 4 at the outlet pressure set value to maintain the heat and pressure stability of the rectification system.

And introducing steam pressurized by the compressor 4 into the tower bottom reboiler 2 as heating steam to heat the tower bottom liquid entering the tower bottom reboiler 2. In the reboiler, heating steam passes through the shell pass, and tower bottoms pass through the tube pass. The shell side temperature is 135 ℃ and the pressure is 0.35 MPa. The tube pass temperature is 130 ℃ and the pressure is 0.19 MPa. After the steam exchanges heat with the tower bottom liquid, the steam is condensed into condensate in a tower bottom reboiler 2.

The condensate after the steam condensation enters the reflux tank 3. The discharge of the reflux tank 3 is divided into two parts, wherein one part of the stream S3 enters the subsequent flow as an overhead product, and the other part of the stream S4 returns to the top of the rectifying tower 1 as a reflux liquid.

the bottom discharge of the rectification column 1 is divided into stream S5 and stream S6. And the stream S5 is heated by a tower bottom reboiler 2 and then flows back to the tower bottom of the rectifying tower 1, and the stream S6 is used as a tower bottom product and enters a subsequent process.

The embodiment of the invention is additionally provided with the compressor on the basis of the existing acetic acid concentration rectifying tower, the compressor is used as a heat pump for pressurizing gas at the tower top, the compressor is used for directly compressing steam at the tower top, the pressure and the temperature of the steam at the tower top are greatly improved, and the pressurized steam at the tower top is used for directly supplying heat to a reboiler at the tower bottom of the rectifying tower, so that the aim of saving energy consumption with lower cost is fulfilled; compared with the existing rectification process, the process can reduce the energy consumption by 60-80% and has obvious energy-saving effect.