Low-concentration ethanol separation device and separation method

Abstract

The low-concentration ethanol separation device comprises a reboiler, a separation membrane, an ethanol storage tank and a heat pump, a raffinate discharge port of the reboiler is communicated with the bottom of the hot side of the separation membrane, the top of the hot side of the separation membrane is communicated with a raffinate feed port of the reboiler, the upper portion of the cold side of the separation membrane is communicated with the bottom of the ethanol storage tank, and the heat pump is communicated with the bottom of the ethanol storage tank. The lower part of the cold side of the separation membrane is communicated with a material inlet of the heat pump, a material outlet of the heat pump is communicated with the top of the ethanol storage tank, a heat exchange medium outlet of the heat pump is communicated with a heat exchange medium inlet of the reboiler, and a heat exchange medium outlet of the reboiler is communicated with a heat exchange medium inlet of the heat pump. Meanwhile, according to the separation method, the situation that the kettle residues have large heat and contain low-concentration ethyl alcohol at the same time is fully utilized, the low-concentration ethyl alcohol is further concentrated through the PDMS pervaporation membrane, meanwhile, heat of the ethyl alcohol can be recycled, and the method is energy-saving, environmentally friendly, green and efficient.

Description

Technical Field

[0001] The invention relates to the technical field of chemical equipment, and in particular to a low-concentration ethanol separation device and a separation method. Background Art

[0002] Distillation operation plays an important role in industrial production such as chemical industry, petrochemical industry, light industry, etc. Therefore, it is very important to master the gas-liquid phase equilibrium relationship and be familiar with the operating characteristics of various tower types in order to select, design and analyze various parameters in the separation process.

[0003] The working principle of the ethanol distillation tower is to control the different temperatures of each section of the tower according to the different vaporization points of each mixed gas to achieve the purpose of separation and purification. Chemical production often requires the separation of liquid mixtures to achieve the purpose of purification or recovery of useful components.

[0004] The bottom residue of the ethanol distillation tower has a large amount of heat and contains a low concentration of ethanol. The energy efficiency of further distilling these low-concentration ethanol is low, so these low-concentration ethanol can only be treated as waste liquid. Summary of the invention

[0005] The purpose of the present invention is to provide a low-concentration ethanol separation device and a separation method to solve one or more of the above-mentioned prior art problems.

[0006] On the one hand, a low-concentration ethanol separation device according to the present invention includes a reboiler, a separation membrane, an ethanol storage tank and a heat pump, the residual liquid discharge port of the reboiler is connected to the bottom of the hot side of the separation membrane, the top of the hot side of the separation membrane is connected to the residual liquid inlet of the reboiler, the upper part of the cold side of the separation membrane is connected to the bottom of the ethanol storage tank, the lower part of the cold side of the separation membrane is connected to the material inlet of the heat pump, the material outlet of the heat pump is connected to the top of the ethanol storage tank, the heat exchange medium outlet of the heat pump is connected to the heat exchange medium inlet of the reboiler, and the heat exchange medium outlet of the reboiler is connected to the heat exchange medium inlet of the heat pump.

[0007] In some embodiments, a residual liquid tank is further included, and the top of the hot side of the separation membrane is in communication with the residual liquid tank.

[0008] In some embodiments, a first circulation pump is provided between the residual liquid discharge port of the reboiler and the bottom of the hot side of the separation membrane.

[0009] In some embodiments, a second circulation pump is provided between the upper portion of the cold side of the separation membrane and the bottom of the ethanol storage tank.

[0010] In some embodiments, a third circulation pump is provided between the heat exchange medium outlet of the reboiler and the heat exchange medium inlet of the heat pump.

[0011] In some embodiments, a three-way valve is further included, wherein one port of the three-way valve is connected to the top of the hot side of the separation membrane, the second port of the three-way valve is connected to the residual liquid tank, and the third port of the three-way valve is connected to the residual liquid inlet of the reboiler.

[0012] In some embodiments, the separation membrane is a PDMS pervaporation membrane.

[0013] On the other hand, a method for separating low-concentration ethanol according to the present invention comprises the following steps:

[0014] S1, cold ethanol in the ethanol storage tank is passed into the upper part of the cold side of the separation membrane under the action of the second circulation pump, forming a circulation between the ethanol storage tank, the separation membrane and the heat pump;

[0015] S2, the low-concentration ethanol at the residual liquid outlet of the reboiler is passed into the bottom of the hot side of the separation membrane under the action of the first circulation pump, forming a circulation between the separation membrane and the reboiler;

[0016] S3. The ethanol vapor on the hot side of the separation membrane permeates to the cold side of the separation membrane. The ethanol vapor on the cold side is condensed into liquid after heat exchange by the heat pump and flows into the ethanol storage tank in a countercurrent manner under the action of the second circulation pump.

[0017] In some embodiments, the following steps are also included: the heat exchange medium of the reboiler is passed into the heat pump for heat exchange under the action of the third circulation pump, and the heat exchange medium of the heat pump is passed into the reboiler for heat exchange.

[0018] In some embodiments, the method further comprises the following step: passing ethanol with a concentration lower than 0.1% into the residual liquid tank from the top of the hot side of the separation membrane.

[0019] Beneficial effects:

[0020] The low-concentration ethanol separation device and separation method of the present invention fully utilize the fact that the kettle residue has a large amount of heat and contains a low concentration of ethanol, and the low-concentration ethanol is further concentrated through the PDMS pervaporation membrane. At the same time, the heat of the ethanol can be recovered for heating the reboiler, which is energy-saving, environmentally friendly, green and efficient. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a schematic structural diagram of a low-concentration ethanol separation device according to an embodiment of the present invention. DETAILED DESCRIPTION

[0022] The present invention will be further described in detail below in conjunction with the accompanying drawings.

[0023] like Figure 1 As shown:

[0024] A low-concentration ethanol separation device comprises a reboiler 10, a separation membrane 20, an ethanol storage tank 30, a heat pump 40, a residual liquid tank 50 and a three-way valve 70, wherein the residual liquid discharge port of the reboiler 10 is communicated with the bottom of the hot side of the separation membrane 20, the top of the hot side of the separation membrane 20 is communicated with the residual liquid inlet of the reboiler 10, the upper part of the cold side of the separation membrane 20 is communicated with the bottom of the ethanol storage tank 30, the lower part of the cold side of the separation membrane 20 is communicated with the material inlet of the heat pump 40, the material outlet of the heat pump 40 is communicated with the top of the ethanol storage tank 30, the heat exchange medium outlet of the heat pump 40 is communicated with the heat exchange medium inlet of the reboiler 10, the heat exchange medium outlet of the reboiler 10 is communicated with the heat exchange medium inlet of the heat pump 40, and the hot side top of the separation membrane 20 is communicated with the residual liquid tank 50;

[0025] Among them, a first circulation pump 61 is arranged between the residual liquid discharge port of the reboiler 10 and the bottom of the hot side of the separation membrane 20, a second circulation pump 62 is arranged between the upper part of the cold side of the separation membrane 20 and the bottom of the ethanol storage tank 30, a third circulation pump 63 is arranged between the heat exchange medium outlet of the reboiler 10 and the heat exchange medium inlet of the heat pump 40, one channel of the three-way valve 70 is connected to the top of the hot side of the separation membrane 20, the second channel of the three-way valve 70 is connected to the residual liquid tank 50, and the three-way of the three-way valve 70 is connected to the residual liquid inlet of the reboiler 10.

[0026] Specifically, the separation membrane 20 is a PDMS pervaporation membrane, which can be used to separate alcohols from water. For a 5 / 95wt% ethanol / water system, at 60°C, the flux is 3kgm 2 hr, separation factor>8.

[0027] A separation method of a low-concentration ethanol separation device comprises the following steps:

[0028] S1, the cold ethanol in the ethanol storage tank 30 is passed into the upper part of the cold side of the PDMS membrane under the action of the second circulation pump 62, and a circulation is formed between the ethanol storage tank 30, the PDMS membrane and the heat pump 40;

[0029] S2, ethanol with a temperature of about 90-95°C and a concentration of about 4% at the residual liquid outlet of the reboiler 10 is passed into the bottom of the hot side of the PDMS membrane under the action of the first circulation pump 61, and a circulation is formed between the PDMS membrane and the reboiler 10;

[0030] S3, since the residual liquid is in a state of ethanol heat saturation, ethanol vapor penetrates to the cold side of the PDMS membrane, and the ethanol vapor on the cold side is condensed into liquid after heat exchange by the heat pump, and then flows into the ethanol storage tank 30 in a countercurrent manner under the action of the second circulation pump 62;

[0031] S4, the heat exchange medium of the reboiler 10 is passed into the heat pump 40 for heat exchange under the action of the third circulation pump 63, the temperature of the heat exchange medium of the heat pump 40 reaches 105-110°C, the heat exchange medium of the heat pump 40 is passed into the reboiler 10 for heat exchange, the temperature of the hot ethanol at the residual liquid outlet of the reboiler 10 is about 90-95°C, and the heat obtained from the hot ethanol by the heat pump 40 can be used for heating the reboiler 10;

[0032] S5. If the ethanol concentration at the top outlet of the hot side of the PDMS membrane is lower than 0.1% by using a benchtop nuclear magnetic resonance, the three-way valve is opened to connect the top outlet of the hot side of the PDMS membrane with the residual liquid tank, and the ethanol with a concentration lower than 0.1% is discharged into the residual liquid tank 50.

[0033] The device and method of the embodiment of the present invention can be used for recovering the heat of the tower top steam and further concentrating the product.

[0034] The above are only preferred embodiments of the present invention. It should be pointed out that a person skilled in the art can make several similar modifications and improvements without departing from the inventive concept of the present invention, and these should also be regarded as within the protection scope of the present invention.

Claims

1. A low-concentration ethanol separation device, characterized in that: The invention comprises a reboiler (10), a separation membrane (20), an ethanol storage tank (30) and a heat pump (40), wherein the residual liquid discharge port of the reboiler (10) is connected to the bottom of the hot side of the separation membrane (20), the top of the hot side of the separation membrane (20) is connected to the residual liquid inlet of the reboiler (10), the upper part of the cold side of the separation membrane (20) is connected to the bottom of the ethanol storage tank (30), the lower part of the cold side of the separation membrane (20) is connected to the material inlet of the heat pump (40), the material outlet of the heat pump (40) is connected to the top of the ethanol storage tank (30), the heat exchange medium outlet of the heat pump (40) is connected to the heat exchange medium inlet of the reboiler (10), and the heat exchange medium outlet of the reboiler (10) is connected to the heat exchange medium inlet of the heat pump (40).

2. A low-concentration ethanol separation device according to claim 1, characterized in that: It also includes a residual liquid tank (50), and the top of the hot side of the separation membrane (20) is connected to the residual liquid tank (50).

3. A low-concentration ethanol separation device according to claim 1, characterized in that: A first circulation pump (61) is provided between the residual liquid discharge port of the reboiler (10) and the bottom of the hot side of the separation membrane (20).

4. A low-concentration ethanol separation device according to claim 1, characterized in that: A second circulation pump (62) is provided between the upper portion of the cold side of the separation membrane (20) and the bottom of the ethanol storage tank (30).

5. A low-concentration ethanol separation device according to claim 1, characterized in that: A third circulation pump (63) is provided between the heat exchange medium outlet of the reboiler (10) and the heat exchange medium inlet of the heat pump (40).

6. A low-concentration ethanol separation device according to claim 2, characterized in that: It also includes a three-way valve (70), one of which is connected to the top of the hot side of the separation membrane (20), the second of which is connected to the residual liquid tank (50), and the third of which is connected to the residual liquid inlet of the reboiler (10).

7. A low-concentration ethanol separation device according to claim 1, characterized in that: The separation membrane (20) is a PDMS pervaporation membrane.

8. A separation method for a low-concentration ethanol separation device, characterized in that: The following steps are involved: S1, cold ethanol in the ethanol storage tank (30) is passed into the upper part of the cold side of the separation membrane (20) under the action of the second circulation pump (62), so as to form a circulation between the ethanol storage tank (30), the separation membrane (20) and the heat pump (40); S2, the low-concentration ethanol at the residual liquid outlet of the reboiler (10) is passed into the bottom of the hot side of the separation membrane (20) under the action of the first circulation pump (61), and a circulation is formed between the separation membrane (20) and the reboiler (10); S3. The ethanol vapor on the hot side of the separation membrane (20) permeates to the cold side of the separation membrane (20). The ethanol vapor on the cold side is condensed into liquid after heat exchange by the heat pump (40), and flows into the ethanol storage tank (30) in a countercurrent manner under the action of the second circulation pump (62).

9. The separation method of a low-concentration ethanol separation device according to claim 8, characterized in that: The following steps are also included: The heat exchange medium of the reboiler (10) is passed into the heat pump (40) for heat exchange under the action of the third circulation pump (63), and the heat exchange medium of the heat pump (40) is passed into the reboiler (10) for heat exchange.

10. The separation method of a low-concentration ethanol separation device according to claim 8, characterized in that: The following steps are also included: Ethanol with a concentration lower than 0.1% is introduced into the residual liquid tank (50) from the top of the hot side of the separation membrane (20).

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