System and method for recycling hydrogen chloride

Abstract

Provided in the present invention are a system and a method for recycling hydrogen chloride. The system comprises an acid tank, a falling film absorber, a circulating pump, a reaction kettle, a condenser, a refrigerant system and an alkali liquor pool, and all the devices used are acid-proof devices. In the present invention, an alcohol is used as an absorption solvent; and an ice river refrigerant is used as a refrigerant. A waste gas containing hydrogen chloride is collected into the acid tank after being absorbed by a falling film; when the concentration reaches a certain value, the absorption liquid can be transferred into the reaction kettle by means of the circulating pump and is heated in the reaction kettle, such that hydrogen chloride and the alcohol are volatilized; and after a gaseous mixture is condensed by means of a multi-stage condenser, high-boiling-point ethanol is condensed into a liquid state, and low-boiling-point gaseous hydrogen chloride and other gaseous impurities cannot be condensed and are thus extracted from different positions of the condenser, thereby achieving separation. By means of the present invention, hydrogen chloride and ethanol can be recycled, the production cost is low, other by-products are not generated during the process, and the environmental pollution is relatively low.

Description

System and method for recycling hydrogen chloride

[0001] The present application claims priority to the Chinese patent application No. 202410408495.5, filed on April 7, 2024, and entitled "System and method for recycling hydrogen chloride", the content of which is incorporated herein by reference in its entirety. TECHNICAL FIELD

[0002] The present application relates to the field of recycling hydrogen chloride industrial exhaust gas, in particular to a system and method for recycling hydrogen chloride. BACKGROUND

[0003] During the hydrogen chloride rectification process, a large amount of hydrogen chloride waste gas is discharged. In addition to containing a large amount of hydrogen chloride, these waste gases also contain components such as CO, N2, CO2, H2, CH4, etc. If these hydrogen chloride-containing waste gases are not treated, they will cause great damage to the environment. At present, the treatment of hydrogen chloride-containing waste gas is mainly through the absorption of a traditional falling film absorber, and the product is mainly 30% or so concentrated hydrochloric acid. A large amount of water and lye is consumed during the absorption process, and the operating cost is high. Furthermore, using water as the absorbent, the cooling effect of the refrigerant is limited, and the solubility of hydrogen chloride in water cannot be further increased, and the concentration of the generated hydrochloric acid can only reach about 30%. In actual production process, the 30% hydrochloric acid generated often cannot be directly used due to high impurity content and other reasons, and subsequent secondary treatment is required, which not only increases the cost of secondary treatment, but also causes secondary pollution to the environment. SUMMARY

[0004] The present application aims to overcome the shortcomings of the prior art and provide a system and method for recycling hydrogen chloride industrial exhaust gas. By using an absorbent and a refrigerant for cooling, the solubility of hydrogen chloride is significantly increased. The absorption of the salt acid-ethanol solution is fully stirred, heated, and multi-stage condensed, which can realize the reuse of hydrogen chloride and ethanol, has low production cost, does not produce other by-products, and has less environmental pollution.

[0005] The technical solution adopted by the present application is as follows:

[0006] A system for recycling hydrogen chloride, comprising an acid tank, the acid tank is connected with a falling film absorber, the acid tank forms a closed loop with the falling film absorber through a first circulating pump, the acid tank is connected to a reaction kettle through the first circulating pump, a first valve is arranged between the first circulating pump and the falling film absorber, and a second valve is arranged between the first circulating pump and the reaction kettle.

[0007] The reactor is connected with a condenser, the upper part of the condenser is connected with a hydrogen chloride rectification tower, the lower part of the condenser is connected with an absorbent buffer tank, and the absorbent buffer tank is connected with an acid tank through a solvent recovery pipeline;

[0008] The falling film absorber and the condenser are both provided with a refrigerant system.

[0009] Preferably, a third valve and a second circulating pump are arranged between the absorbent buffer tank and the acid tank; and / or,

[0010] The top of the acid tank is provided with a vent valve connected with a lye absorption pool; and / or,

[0011] A heater is arranged on the reactor, and a stirrer is arranged in the reactor.

[0012] Preferably, a jacket is arranged on the acid tank, and a refrigerant is arranged in the jacket, and the temperature of the refrigerant is-30 to-10℃.

[0013] Preferably, the condenser is a multi-stage condenser, and a refrigerant water inlet and a refrigerant water return are arranged on the condenser; and / or,

[0014] The refrigerant system uses a refrigerant with a temperature of-85 to 0℃, and a refrigerant inlet and a refrigerant return are arranged on the falling film absorber.

[0015] A hydrogen chloride recycling method, which utilizes the hydrogen chloride recycling system as described above, comprises the following steps:

[0016] S1, closing the vent valve, the second valve and the third valve, opening the first valve, injecting the absorbent into the acid tank, cooling the absorbent in the acid tank by the refrigerant, reducing the temperature to-30 to-10℃, circulating the absorbent into the falling film absorber by the first circulating pump, and collecting the absorbed hydrogen chloride waste gas into the acid tank;

[0017] S2, after the hydrogen chloride-absorbent mass concentration in the acid tank is greater than or equal to 45%, closing the first valve, opening the second valve, and circulating the hydrogen chloride-absorbent solution into the reactor;

[0018] S3, adjusting the stirring speed of the stirrer in the reactor to 100 to 200 r / min, opening the heater, and maintaining the temperature of the absorbent in the reactor at 60 to 80℃;

[0019] S4, the hydrogen chloride and the absorbent enter the condenser, are separated according to the boiling points, the hydrogen chloride in the upper part of the condenser is sent to the hydrogen chloride rectification tower for rectification, and the absorbent is evaporated from the lower part of the condenser and is condensed and returned to the absorbent buffer tank.

[0020] Preferably, the step S4 is specifically: hydrogen chloride and the absorbent enter the condenser, and are separated according to the boiling points; the hydrogen chloride in the upper part of the condenser is sent to the hydrogen chloride rectification tower for rectification; the absorbent is evaporated from the lower part of the condenser and is condensed and returned to the absorbent buffer tank; when the liquid level in the absorbent buffer tank reaches 1 / 5 of the height, the third valve is opened, the second circulating pump is started, and the absorbent buffer tank is discharged into the acid tank; after stabilization, the outlet flow of the second circulating pump is adjusted to 20 kg / h; and / or,

[0021] The method further comprises a step S5: when the pressure in the acid tank reaches 0.2 MPa or above, the vent valve at the top of the acid tank is opened, and accumulated insoluble gas impurities are discharged to the lye absorption tank; when the pressure is reduced to 0.05 MPa, the vent valve is closed.

[0022] Preferably, when the absorbent in the system is insufficient, the absorbent is added and supplemented at the absorbent buffer tank.

[0023] Preferably, the absorbent is an alcohol, including methanol, ethanol, propanol and butanol; and / or,

[0024] The insoluble gas impurities in S5 include H2, O2 and N2.

[0025] Preferably, the absorbent accounts for 1 / 3-2 / 3 of the volume of the acid tank.

[0026] Preferably, the refrigerant is an ice river refrigerant.

[0027] The application provides a hydrogen chloride recycling method and system, comprising an acid tank, a falling film absorber, a circulating pump, a reaction kettle, a condenser, a refrigerant system and an alkali solution pool. All the used equipment is acid-resistant equipment. The application uses alcohol as the absorption solvent and ice river refrigerant as the refrigerant. After the hydrogen chloride-containing waste gas is absorbed by the falling film, the absorption liquid is collected in the acid tank. When the concentration reaches a certain value, the absorption liquid can be transferred to the reaction kettle by the circulating pump. The absorption liquid is heated in the reaction kettle, and the hydrogen chloride and alcohol are volatilized. The gaseous mixture is condensed by the multi-stage condenser. The high-boiling-point ethanol is condensed into liquid state, and the low-boiling-point gaseous hydrogen chloride and other gaseous impurities cannot be condensed, so they are collected from different positions of the condenser, so that separation is realized. The gaseous hydrogen chloride is collected from the upper part of the condenser and then returned to the hydrogen chloride rectification system again, and the liquefied and separated alcohol is transported to the acid tank again. The application uses alcohol as the absorption solvent and uses ice river refrigerant to cool the absorption solvent, so that the solubility of hydrogen chloride in ethanol is increased, the concentration of the prepared hydrogen chloride-ethanol solution is greater than or equal to 45%, and the absorption effect is obviously better than that of using water as the absorption agent. The prepared hydrochloric acid-ethanol solution is fully stirred, heated and multi-stage condensed, so that the gaseous hydrogen chloride and the liquid ethanol are separated. The gaseous hydrogen chloride and the liquid ethanol are returned to the rectification tower and the acid tank respectively and reused. The method can realize the reuse of hydrogen chloride and ethanol absorption agent, is low in cost, is environmentally friendly, avoids the use of a large amount of water in the traditional hydrogen chloride absorption, and solves the problem that a large amount of hydrochloric acid by-products are difficult to handle.

[0028] Compared with the prior art, the application has the following beneficial effects:

[0029] 1. By using ethanol as the absorption agent and using refrigerant to cool, the solubility of hydrogen chloride is increased, and the absorption effect is obviously better than that of using water as the absorption agent.

[0030] 2. The absorption of the hydrochloric acid-ethanol solution is stirred, heated and multi-stage condensed, so that the hydrogen chloride and the ethanol can be reused, and the operation cost is low.

[0031] 3. A large amount of other by-products are not generated in the whole process, secondary treatment of a large amount of by-products is not needed, the treatment cost is low, the environmental pollution is small. BRIEF DESCRIPTION OF DRAWINGS

[0032] In order to more clearly illustrate the specific embodiments and technical schemes of the application, the drawings in the specific embodiments and technical schemes will be briefly introduced below.

[0033] Fig. 1 is a schematic diagram of the overall structure of the system of the application.

[0034] In the figure, 1-acid tank, 2-the first circulating pump, 3-falling film absorber, 4-cold medium import, 5-cold medium return, 6-alkali absorption pool, 7-reactor, 8-heater, 9-stirrer, 10-condenser, 11-cold medium water inlet, 12-cold medium water return, 13-solvent recovery pipeline, 14-the second circulating pump, 15-absorbent buffer tank, 16-hydrogen chloride rectification column, 17-the first valve, 18-the second valve, 19-the third valve, 20-vent valve. DETAILED DESCRIPTION

[0035] As shown in Figure 1, a hydrogen chloride recycling system, comprising an acid tank 1, the acid tank 1 is provided with a jacket, the jacket is provided with a cold medium, the temperature of the cold medium is-30~ -10℃, the acid tank 1 and the falling film absorber 3 are connected, the acid tank 1 and the falling film absorber 3 form a closed loop through the first circulating pump 2, the acid tank 1 is connected to the reactor 7 through the first circulating pump 2, the first circulating pump 2 and the falling film absorber 3 are provided with the first valve 17, the first circulating pump 2 and the reactor 7 are provided with the second valve 18; The reactor 7 is provided with a heater 8, and the reactor 7 is provided with a stirrer 9;

[0036] The reactor 7 is connected with the condenser 10, the condenser 10 is a multi-stage condenser, the condenser 10 is provided with a cold medium water inlet 11 and a cold medium water return 12, the upper part of the condenser 10 is connected with the hydrogen chloride rectification column 16, the lower part of the condenser 10 is connected with the absorbent buffer tank 15, the absorbent buffer tank 15 is connected with the acid tank 1 through the solvent recovery pipeline 13, the absorbent buffer tank 15 and the acid tank 1 are provided with the third valve 19 and the second circulating pump 14;

[0037] The top of the acid tank 1 is provided with a vent valve 20, and the vent valve 20 is connected with the alkali absorption pool 6;

[0038] The falling film absorber 3 and the condenser 10 are both provided with a cold medium system, the cold medium system uses-85~0℃ cold medium, the falling film absorber 3 is provided with a cold medium import 4 and a cold medium return 5.

[0039] Method embodiment

[0040] A method for recycling hydrogen chloride, the steps are as follows:

[0041] S1, close the vent valve 20, the second valve 18 and the third valve 19, open the first valve 17, inject the absorbent into the acid tank 1, the absorbent in the acid tank 1 accounts for 1 / 3-2 / 3 of the volume of the acid tank 1, the ice river cold medium cools the absorbent in the acid tank 1, the temperature is reduced to-30~ -10℃, the first circulating pump 2 pumps the absorbent into the falling film absorber 3 and circulates all the time, the hydrogen chloride waste gas enters the falling film absorber 3 and is absorbed, and then is collected into the acid tank 1;

[0042] S2, after the hydrogen chloride-absorbent mass concentration of the acid tank 1 is greater than or equal to 45%, the first valve 17 is closed, the second valve 18 is opened, and the hydrogen chloride-absorbent solution is poured into the reaction kettle 7;

[0043] S3, the stirring speed of the reaction kettle 7 is adjusted to 100-200 r / min, the heater 8 is opened, and the absorbent temperature in the reaction kettle 7 is maintained at 60-80 ℃;

[0044] S4, the hydrogen chloride and the absorbent enter the condenser 10 and are separated according to the boiling points, the hydrogen chloride at the upper part of the condenser 10 is sent to the hydrogen chloride rectification tower 16 for rectification, the absorbent is evaporated from the lower part of the condenser 10 and is condensed and returned, when the liquid level in the absorbent buffer tank 15 reaches 1 / 5 of the height, the third valve 19 is opened, the second circulating pump 14 is opened, the absorbent buffer tank 15 is poured into the acid tank, and after stabilization, the outlet flow of the second circulating pump 14 is adjusted to 20 kg / h;

[0045] S5, when the pressure in the acid tank 1 reaches 0.2 MPa or above, the vent valve 20 at the top of the acid tank 1 is opened, and the accumulated insoluble gas impurities H2, O2 and N2 are discharged to the lye absorption tank 6, and after the pressure is reduced to 0.05 MPa, the vent valve 20 is closed.

[0046] When the absorbent in the system is insufficient, the absorbent buffer tank 15 is added and supplemented.

[0047] The following examples are implemented according to the process of the above method example, and the difference lies in that different absorbents are used.

[0048] Example 1

[0049] The scheme can realize the recycling of the absorbent and the hydrogen chloride, reduce pollution, and reduce production cost. When the absorbent in the present embodiment is 99.5% ethanol, the recovery rate of the hydrogen chloride-containing waste gas after passing through the recycling device can reach 80-85%, and the purity can be increased by about 10%-20%.

[0050] Example 2

[0051] When the absorbent in the present embodiment is 99.5% methanol, the hydrogen chloride recovery rate is 78%-85%. The purity can be increased by 10%-20%.

[0052] Example 3

[0053] When the absorbent in the present embodiment is other alcohol solvents or mixed solvents of alcohol solvents, the hydrogen chloride recovery rate is in the range of 50%-90%, and the purity is increased by 10%-25%.

[0054] Example 4

[0055] When the absorbent of the present embodiment is water, the recovery rate of hydrogen chloride is in the range of 20% to 30%, and hydrogen chloride and water cannot be separated because of the similar boiling points and cannot be recovered.

[0056] Of course, the above-mentioned content is only a preferred experimental example of the present application, and cannot be considered to limit the scope of the embodiments of the present application. The present application is also not limited to the above examples, and equivalent changes and improvements made by those skilled in the art within the essential scope of the present application should be attributed to the patent coverage of the present application.

Claims

1. A system for recovering and reusing hydrogen chloride, characterized in that: comprising an acid tank, the acid tank being connected to a falling film absorber, the acid tank forming a closed loop with the falling film absorber via a first circulation pump, the acid tank being connected to a reactor via the first circulation pump, a first valve being provided between the first circulation pump and the falling film absorber, and a second valve being provided between the first circulation pump and the reactor; The reactor is connected to a condenser, the upper part of the condenser is connected to a hydrogen chloride distillation tower, the lower part of the condenser is connected to an absorbent buffer tank, and the absorbent buffer tank is connected to an acid tank through a solvent recovery line; The falling film absorber and the condenser are both provided with a refrigerant system.

2. The system for recovering and reusing hydrogen chloride according to claim 1, characterized in that: A third valve and a second circulation pump are provided between the absorbent buffer tank and the acid tank; and / or, A vent valve is provided on the top of the acid tank, and the vent valve is connected to the alkali solution absorption tank; and / or, The reactor is provided with a heater, and the reactor is provided with a stirrer.

3. The hydrogen chloride recovery and reuse system according to claim 1 or 2, characterized in that: The acid tank is provided with a jacket, and a refrigerant is provided in the jacket. The temperature of the refrigerant is -30 to -10°C.

4. The system for recovering and reusing hydrogen chloride according to claim 1 or 2, characterized in that: The condenser is a multi-stage condenser, and is provided with a refrigerant water inlet and a refrigerant water return inlet; and / or, The refrigerant system uses a refrigerant at a temperature of -85 to 0°C, and the falling film absorber is provided with a refrigerant inlet and a refrigerant return port.

5. A method for recovering and reusing hydrogen chloride, characterized in that: The system for recovering and reusing hydrogen chloride as claimed in claim 2 comprises the following steps: S1. Close the vent valve, the second valve, and the third valve, open the first valve, and inject absorbent into the acid tank. The refrigerant cools the absorbent in the acid tank to -30 to -10°C. The first circulation pump pumps the absorbent into the falling film absorber and circulates it continuously. The hydrogen chloride waste gas enters the falling film absorber, is absorbed, and is then collected in the acid tank. S2. When the mass concentration of hydrogen chloride-absorbent in the acid tank is ≥45%, close the first valve, open the second valve, and inject the hydrogen chloride-absorbent solution into the reactor; S3. Adjust the agitator speed in the reactor to 100-200 r / min and turn on the heater to maintain the absorbent temperature in the reactor at 60-80°C; S4, hydrogen chloride and absorbent enter the condenser and are separated according to their boiling points. The hydrogen chloride at the top of the condenser is sent to the hydrogen chloride distillation tower for distillation, and the absorbent is evaporated from the bottom of the condenser and condensed and refluxed into the absorbent buffer tank.

6. The method for recovering and reusing hydrogen chloride according to claim 5, wherein: The step S4 specifically comprises: hydrogen chloride and absorbent enter a condenser and are separated according to their boiling points; hydrogen chloride in the upper portion of the condenser is sent to a hydrogen chloride distillation tower for rectification; absorbent evaporates from the lower portion of the condenser, condenses and refluxes into an absorbent buffer tank; when the liquid level in the absorbent buffer tank reaches 1 / 5 of the height, the third valve is opened, the second circulation pump is started, and the absorbent buffer tank is pumped into the acid tank; after stabilization, the outlet flow rate of the second circulation pump is adjusted to 20 kg / h; and / or, The method further includes step S5: when the pressure in the acid tank reaches above 0.2 MPa, opening the vent valve on the top of the acid tank to discharge the accumulated insoluble gas impurities into the alkali solution absorption tank; and closing the vent valve after the pressure drops to 0.05 MPa.

7. The method for recovering and reusing hydrogen chloride according to claim 5, wherein: When the absorbent in the system is insufficient, it is added to the absorbent buffer tank.

8. The method for recovering and reusing hydrogen chloride according to claim 6, wherein: The absorbent is an alcohol, including methanol, ethanol, propanol and butanol; and / or, The insoluble gaseous impurities in S5 include H2, O2 and N2.

9. The method for recovering and reusing hydrogen chloride according to claim 5, wherein: The absorbent injected into the acid tank accounts for 1 / 3-2 / 3 of the volume of the acid tank.

10. The method for recovering and reusing hydrogen chloride according to claim 5, characterized in that: The refrigerant is glacial refrigerant.

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