A dichlorobenzene exhaust gas purification and hydrochloric acid recovery system

Abstract

The application discloses a dichlorpinacol tail gas purification and hydrochloric acid recovery system, which comprises a workshop tail gas discharge pipe, wherein an acid mist demister for removing pinacol liquid drops is connected to the tail gas discharge pipe, a collecting tank is connected to a liquid outlet end of the first acid mist demister, a gas outlet end is communicated with a first washing circulating device, the first washing circulating device is further communicated with a second washing circulating device, the first washing circulating device and the second washing circulating device are of the same structure, the second washing circulating device is communicated with a water circulating absorption device for recovering hydrochloric acid, the water circulating absorption device comprises a first-stage water circulating absorption device, a second-stage water circulating absorption device and a third-stage water circulating absorption device, the devices are of the same structure and are sequentially communicated, water outlets and water inlets are arranged on the first-stage water circulating absorption device, the second-stage water circulating absorption device and the third-stage water circulating absorption device, and an alkali absorption device is further communicated with the third-stage water circulating absorption device; and the system can reduce the organic matter content of hydrogen chloride gas and improve economic benefits.

Description

TECHNICAL FIELD

[0001] The application relates to a dichlorpinacol tail gas purification and hydrochloric acid recovery system, BACKGROUND

[0002] Dichlorpinacol is an important chemical raw material intermediate, which is widely used in the production process of medicines and pesticides. The main raw material is pinacolone and chlorine. The reaction process is a chlorination reaction. At present, in the production process of dichlorpinacol, tail gas is generated. The tail gas mainly contains hydrogen chloride and part of gaseous pinacolone. The current recovery system mainly includes two-stage condensation recovery devices and three-stage water circulation absorption devices. The two-stage condensation recovery device mainly condenses the pinacolone in the gas to form a liquid state through condensation. The components in the condensed tail gas are mainly hydrogen chloride. Then, the three-stage water circulation absorption device is used to recover the hydrogen chloride in the tail gas to form by-product hydrochloric acid. The by-product hydrochloric acid has a deep color and a high COD, that is, the content of the entrained organic matter is too high. The pinacolone below the dew point also enters the water circulation absorption device with the hydrogen chloride. With the increase of the concentration of the hydrochloric acid in the water circulation absorption device, the pinacolone is also dissolved in the first-stage water circulation absorption device, thereby causing poor quality of the by-product hydrochloric acid. SUMMARY

[0003] The technical problem to be solved by the application is to provide a dichlorpinacol tail gas purification and hydrochloric acid recovery system, which can reduce the content of organic matter in hydrogen chloride gas and improve economic benefits.

[0004] To solve the above technical problems, the technical scheme of the application is as follows: a dichlorpinacol tail gas purification and hydrochloric acid recovery system, which comprises a workshop tail gas discharge pipe, the tail gas discharge pipe is connected with a first acid mist eliminator for removing pinacolone droplets, the liquid outlet end of the first acid mist eliminator is connected with a collection tank for collecting pinacolone droplets, the gas outlet end of the first acid mist eliminator is communicated with a first washing circulation device, the first washing circulation device is in communication with a second washing circulation device, the first washing circulation device and the second washing circulation device are the same in structure, the first washing circulation device and the second washing circulation device use the circulating saturated hydrochloric acid solution to wash and absorb pinacolone in the tail gas; the second washing circulation device is communicated with a water circulation absorption device for recovering hydrochloric acid, the water circulation absorption device comprises a first-stage water circulation absorption device, a second-stage water circulation absorption device and a third-stage water circulation absorption device, the first-stage water circulation absorption device, the second-stage water circulation absorption device and the third-stage water circulation absorption device are the same in structure and are sequentially communicated, the first-stage water circulation absorption device, the second-stage water circulation absorption device and the third-stage water circulation absorption device are each provided with a water outlet and a water inlet, and the third-stage water circulation absorption device is further communicated with an alkali absorption device for further purifying the tail gas.

[0005] As a preferred scheme, the first washing circulation device comprises a first packing absorption tower, a first washing circulation tank and a first cooling device, which are sequentially connected to form a loop, the first washing circulation tank contains saturated hydrochloric acid solution, and the saturated hydrochloric acid solution flows in a circulation manner among the first washing circulation tank, the first cooling device and the first packing absorption tower; the gas outlet end of the first acid mist eliminator is communicated with the first packing absorption tower, and the first washing circulation tank is further provided with a liquid discharge port for conveniently discharging hydrochloric acid.

[0006] As a preferred scheme, the first-stage water circulation absorption device comprises a first cooling absorption device and a first-stage water washing absorption tank, which are sequentially connected to form a loop, and the first cooling absorption device has a gas inlet end at the upper end and is communicated with the gas outlet end of the packing absorption tower of the second washing circulation device.

[0007] As a preferred scheme, the alkali absorption device comprises a second packing absorption tower and an alkali absorption tank, which are sequentially connected to form a loop, the alkali absorption tank contains an alkaline liquid, and the second packing absorption tower is communicated with a pipeline for discharging the purified tail gas.

[0008] As a preferred scheme, the first cooling device comprises a graphite cooler, and the first cooling absorption device comprises a falling film absorber, and the graphite cooler and the falling film absorber are respectively connected with inlet and outlet cooling water pipelines at two ends.

[0009] As a preferred scheme, the second washing circulation device and the first-stage water circulation absorption device are also provided with a second acid mist eliminator, the gas inlet of the second acid mist eliminator is communicated with the gas outlet end of the packing absorption tower of the second washing circulation device, the gas outlet of the second acid mist eliminator is communicated with the gas inlet end of the upper end of the first cooling absorption device, and the liquid outlet end of the second acid mist eliminator is communicated with the washing circulation tank of the second washing circulation device through a reflux pipeline.

[0010] As a preferred scheme, the first-stage water washing absorption tank is provided with a recovery outlet, which is communicated with a recovery tank through a recovery pipeline, the first-stage water washing absorption tank is sequentially communicated with a second-stage water washing absorption tank of a second-stage water circulation absorption device and a third-stage water washing absorption tank of a third-stage water circulation absorption device through a transfer pipeline, the transfer pipeline is provided with a transfer pump, and the third-stage water washing absorption tank is communicated with a water inlet pipeline.

[0011] The effect of the present application is that, due to the dichlorofrethane tail gas purification and hydrochloric acid recovery system, including a workshop tail gas discharge pipe, the acid mist demister for removing frethane droplets is connected to the tail gas discharge pipe, the liquid outlet end of the acid mist demister is connected to a collection tank for collecting frethane droplets, the gas outlet end of the acid mist demister is communicated with the first washing circulating device, the first washing circulating device is further communicated with the second washing circulating device, the first and second washing circulating devices have the same structure, the first and second circulating devices use the circulating saturated hydrochloric acid solution to wash and absorb the frethane in the tail gas; the second washing circulating device is communicated with the water circulating absorption device for recovering hydrochloric acid, the water circulating absorption device includes a first, second and third water circulating absorption devices, the first, second and third water circulating absorption devices have the same structure and are sequentially communicated, the first, second and third water circulating absorption devices are each provided with a water outlet and a water inlet, and the third water circulating absorption device is further communicated with the alkali absorption device for further purifying the tail gas; the system first connects the first acid mist demister to the workshop tail gas discharge pipe to collect part of the frethane droplets, then the tail gas enters the first washing circulating device to filter the frethane, after passing through the first washing circulating device, the tail gas enters the second washing circulating device to be filtered, after the second washing circulating device is filtered, the tail gas enters the water circulating absorption device, and is sequentially filtered from the first, second and third water circulating absorption devices, while in any one of the first, second and third water circulating absorption devices, when the water absorbs enough hydrochloric acid, the water is discharged from the water outlet and then sufficient water is supplemented from the water inlet, finally the tail gas enters the alkali absorption device for final purification and is discharged; the system can reduce the organic content of hydrogen chloride gas, make the by-product hydrochloric acid reach the colorless and transparent standard and be effectively recovered, and improve the economic benefit.

[0012] Further, the first washing circulation device comprises a first packing absorption tower, a first washing circulation tank and a first cooling device, the first packing absorption tower, the first washing circulation tank and the first cooling device are sequentially connected to form a loop, the first washing circulation tank stores saturated hydrochloric acid solution, and the saturated hydrochloric acid solution flows in the first washing circulation tank, the first cooling device and the first packing absorption tower; the gas outlet end of the first acid mist eliminator is communicated with the first packing absorption tower, and the first washing circulation tank is further provided with a liquid discharge port for conveniently discharging hydrochloric acid; when the tail gas enters the first packing absorption tower, the packing in the first packing absorption tower fully contacts the tail gas to filter impurities in the tail gas, and the first washing circulation tank uses saturated hydrochloric acid solution with a concentration of more than 36%, so that it is difficult for the hydrochloric acid to absorb hydrogen chloride in the tail gas, and the pinacol in the tail gas is dissolved in the hydrochloric acid; the first washing device forms a loop to continuously purify the tail gas, maximizes the purification efficiency of the tail gas, and the first cooling device can also cool the tail gas to condense the tail gas, so that the pinacol in the tail gas can be fully absorbed, and the saturated hydrochloric acid solution in the first washing circulation tank can be taken out from the liquid discharge port for secondary use, further improving the efficiency.

[0013] Further, the first cooling device comprises a graphite cooler, and the first cooling absorption device comprises a falling film absorber, and the graphite cooler and the falling film absorber are respectively connected with inlet and outlet cooling water pipelines at two ends; in this way, different liquids with different temperatures can be introduced to achieve different degrees of cooling, thereby ensuring good cooling effect.

[0014] Further, the first cooling device comprises a graphite cooler, and the first cooling absorption device comprises a falling film absorber, and the graphite cooler and the falling film absorber are respectively connected with inlet and outlet cooling water pipelines at two ends; in this way, different liquids with different temperatures can be introduced to achieve different degrees of cooling, thereby ensuring good cooling effect.

[0015] Further, the first cooling device comprises a graphite cooler, and the first cooling absorption device comprises a falling film absorber, and the graphite cooler and the falling film absorber are respectively connected with inlet and outlet cooling water pipelines at two ends; in this way, different liquids with different temperatures can be introduced to achieve different degrees of cooling, thereby ensuring good cooling effect.

[0016] And the second acid mist eliminator is arranged between the second washing circulating device and the primary water circulating absorption device, the air inlet of the second acid mist eliminator is communicated with the air outlet of the packing tower of the second washing circulating device, the air outlet of the second acid mist eliminator is communicated with the air inlet of the upper end of the primary cooling absorption device, and the liquid outlet of the second acid mist eliminator is communicated with the washing circulating tank of the second washing circulating device through a reflux pipeline; since the tail gas is washed by the two-stage packing tower, part of hydrochloric acid in the tail gas can be further filtered out by the second acid mist eliminator, so that the dryness of the tail gas is ensured, and the filtered hydrochloric acid can directly enter the second washing circulating tank, so that the hydrochloric acid is fully utilized and the efficiency is improved.

[0017] And the recovery outlet is arranged on the primary water washing absorption tank, the recovery outlet is communicated with the recovery tank through a recovery pipeline, the primary water washing absorption tank is communicated with the secondary water washing absorption tank of the secondary water circulating absorption device and the tertiary water washing absorption tank of the tertiary water circulating absorption device through a transfer pipeline in sequence, a transfer pump is arranged on the transfer pipeline, and the tertiary water washing absorption tank is communicated with the water inlet pipeline; in this way, the primary water washing absorption tank, the secondary water washing absorption tank and the tertiary water washing absorption tank do not need to be provided with water outlets and water inlets, when the hydrochloric acid in the secondary water washing absorption tank and the tertiary water washing absorption tank reaches the recoverable condition, the hydrochloric acid enters the primary water washing absorption tank, and finally the hydrochloric acid is recovered, and then the water amount is supplemented from the water inlet pipeline of the tertiary water washing absorption tank, and the water enters the primary water washing absorption tank from the tertiary water washing absorption tank in sequence, so that the operation is convenient and the efficiency is improved. BRIEF DESCRIPTION OF DRAWINGS

[0018] The application will be further described below in combination with the drawings and examples.

[0019] Figure 1 is a structural schematic diagram of an embodiment of the application.

[0020] In the drawings: 1, workshop tail gas discharge pipe; 2, first acid mist eliminator; 3, collection tank; 4, first packing tower; 5, first washing circulating tank; 6, graphite cooler; 7, inlet and outlet cooling water pipeline; 8, second washing circulating tank; 9, liquid discharge port; 10, falling film absorber; 11, primary water washing absorption tank; 12, secondary water washing absorption tank; 13, tertiary water washing absorption tank; 14, transfer pump; 15, recovery pipeline; 16, water inlet pipeline; 17, second packing tower; 18, alkali absorption tank; 19, recovery tank; 20, third packing tower; 21, recovery outlet; 22, second acid mist eliminator. DETAILED DESCRIPTION

[0021] The application will be further described below in combination with the drawings and examples.

[0022] As Figure 1As shown, a dichlorpinacol tail gas purification and hydrochloric acid recovery system, comprising a workshop tail gas discharge pipe 1, the first acid mist eliminator 2 connected with the dichlorpinacol droplet removal, the first acid mist eliminator 2 liquid outlet end is connected with the collection tank 3 for collecting dichlorpinacol droplets, the first acid mist eliminator 2 gas outlet and the first washing circulating device are communicated, the first washing circulating device is further communicated with the second washing circulating device, the first washing circulating device and the second washing circulating device are the same structure, the first circulating device and the second circulating device utilize the circulating saturated hydrochloric acid solution and the tail gas to circulate washing and absorption of dichlorpinacol in the tail gas; the second washing circulating device is communicated with the water circulating absorption device for recovering hydrochloric acid, the water circulating absorption device includes a primary water circulating absorption device, a secondary water circulating absorption device and a tertiary water circulating absorption device, the primary water circulating absorption device, the secondary water circulating absorption device and the tertiary water circulating absorption device are the same structure and are communicated in sequence, the primary water circulating absorption device, the secondary water circulating absorption device and the tertiary water circulating absorption device are provided with water outlets and water inlets, and the tertiary water circulating absorption device is further communicated with the alkali absorption device for further purifying the tail gas.

[0023] In the embodiment, the first washing circulating device includes a first packing absorption tower 4, a first washing circulating tank 5 and a first cooling device, the first packing absorption tower 4, the first washing circulating tank 5 and the first cooling device are sequentially connected to form a loop, the first washing circulating tank 5 stores saturated hydrochloric acid solution, and the saturated hydrochloric acid solution circulates between the first washing circulating tank 5, the first cooling device and the first packing absorption tower 4; the gas outlet end of the first acid mist eliminator 2 is communicated with the first packing absorption tower 4, and the first washing circulating tank 5 is further provided with a liquid discharge port 9 for conveniently discharging hydrochloric acid; the packing absorption tower is a device for absorbing gas with a liquid absorbent, in order to make the liquid absorbent and the gas fully contact, when the tail gas enters the first packing absorption tower 4, the packing in the first packing absorption tower 4 fully contacts with the tail gas, and the first washing circulating tank 5 stores saturated hydrochloric acid solution, the concentration of the hydrochloric acid reaches more than 36%, so that it is difficult for the hydrochloric acid to absorb hydrogen chloride in the tail gas, and the dichlorpinacol in the tail gas is dissolved in the hydrochloric acid, the first washing device forms a loop to continuously purify the tail gas, so that the purification benefit is maximized, and the cooling device can also cool and cool the tail gas, so that the tail gas is condensed, and the water vapor in the tail gas is also condensed, so that the dichlorpinacol is more easily absorbed in the first washing circulating tank 5, the generated hydrochloric acid is stored in the first washing circulating tank 5, and the hydrochloric acid taken out from the liquid discharge port 9 can be used twice, further improving the benefit.

[0024] Further, the first and second washing circulation devices are of the same structure, and the second washing circulation device comprises a third packed tower 20, a second washing circulation tank 8 and a second cooling device, so that the tail gas is filtered by two rounds of pinacolone, effectively removing pinacolone in the tail gas, and facilitating the processing of the tail gas by the water absorption device.

[0025] In the embodiment, the primary water circulation absorption device comprises a first cooling absorption device and a primary water washing absorption tank 11, which are sequentially connected to form a loop, and the upper end of the first cooling absorption device is an air inlet end and is connected to the air outlet end of the packed tower of the second washing circulation device. Hydrogen chloride gas is dissolved in water to form hydrochloric acid, and a large amount of heat is generated at the same time. The first cooling absorption device can effectively cool down to ensure production safety. When the concentration of hydrochloric acid in the primary water washing absorption tank 11 is increased, the hydrochloric acid can be discharged for recycling. The tail gas can be further purified to improve economic benefits.

[0026] In the embodiment, the alkali absorption device comprises a second packed tower 17 and an alkali absorption tank 18, which are sequentially connected to form a loop. The alkali absorption tank 18 stores an alkaline liquid, and the second packed tower 17 is connected to a pipeline for discharging the purified tail gas. Since the tail gas is filtered by pinacolone and hydrochloric acid, the tail gas basically does not contain hydrogen chloride gas. Finally, the tail gas is subjected to an acid-base neutralization reaction by the alkaline liquid to ensure that the tail gas is qualified for discharge.

[0027] In the embodiment, the first cooling device comprises a graphite cooler 6, and the first cooling absorption device comprises a falling film absorber 10. The two ends of the graphite cooler 6 and the falling film absorber 10 are respectively connected to inlet and outlet cooling water pipelines 7. The graphite cooler 6 is a kind of heat exchange equipment for cooling fluid. Water is usually used as cooling water to remove heat. The graphite cooler 6 has stable properties, good corrosion resistance, high chemical stability, good heat conduction performance, and can effectively deal with hydrogen peroxide and pinacolone in the tail gas to ensure safety and sealing. The falling film absorber 10 is mainly used for absorbing hydrogen peroxide gas into hydrochloric acid and can also be used for recycling waste hydrogen chloride byproduct. The falling film absorption is carried out by flowing liquid film to absorb gas, and the heat is also removed by circulating the cooling water pipeline. The falling film absorber 10 has high absorption efficiency, corrosion resistance, no scaling, light weight, long service life, easy maintenance and other advantages. Different temperatures of liquid are introduced to achieve different degrees of cooling, so as to ensure good cooling effect.

[0028] Further, the second washing circulation device and the first water circulation absorption device are also provided with a second acid mist eliminator 22, the air inlet of the second acid mist eliminator 22 is communicated with the gas outlet end of the packing absorption tower of the second washing circulation device, the gas outlet of the second acid mist eliminator 22 is communicated with the air inlet of the upper end of the first cooling absorption device, and the liquid outlet end of the second acid mist eliminator 22 is communicated with the washing circulation tank of the second washing circulation device through a reflux pipeline; since the tail gas is washed by the two-stage packing absorption tower, there is part of hydrochloric acid or water vapor in the tail gas, the liquid hydrochloric acid can be removed by the acid mist eliminator, the dryness of the tail gas is ensured, and the filtered hydrochloric acid can directly enter the second washing circulation tank 8, so that the hydrochloric acid is fully utilized and the efficiency is improved.

[0029] In the embodiment, the first water washing absorption tank 11 is provided with a recovery outlet 21 which is communicated with a recovery tank 19 through a recovery pipeline 15, the first water washing absorption tank 11, the second water washing absorption tank 12 of the second water circulation absorption device and the third water washing absorption tank 13 of the third water circulation absorption device are sequentially communicated through a transfer pipeline, the transfer pipeline is provided with a transfer pump 14, and the third water washing absorption tank 13 is communicated with a water inlet pipeline 16; in this way, the first water washing absorption tank 11, the second water washing absorption tank 12 and the third water washing absorption tank 13 do not need to be provided with water outlets and water inlets, when the hydrochloric acid in the second water washing absorption tank 12 and the third water washing absorption tank 13 reaches the recoverable condition, the hydrochloric acid enters the first water washing absorption tank 11, and then the hydrochloric acid is recovered, and then the water is supplemented from the water inlet pipeline 16 of the third water washing absorption tank 13, and the water enters the first water washing absorption tank 11 from the third water washing absorption tank 13 in sequence, so that the operation is convenient and the efficiency is improved.

[0030] The working principle of the present application is as follows: firstly, the tail gas discharge pipe 1 is connected to the first acid mist eliminator 2 to recover pinacol droplets, then the tail gas enters the first packing absorption tower 4 of the first washing circulating device to contact with the packing in the first packing absorption tower 4, and then enters the first washing circulating tank 5 for further mixing, then enters the graphite cooler 6 along the pipeline, and cooling water is introduced to cool the tail gas, then enters the first packing absorption tower 4 again, at this time, the solution in the first packing absorption tower 4 is saturated hydrochloric acid solution, the concentration of hydrochloric acid reaches 36% or more, and pinacol in the tail gas is dissolved in hydrochloric acid, after repeated washing, the pinacol absorbed by the saturated hydrochloric acid solution reaches the required amount, and is discharged from the drain port 9, and new saturated hydrochloric acid solution is introduced, then the tail gas enters the second washing circulating device, the process is the same as the first washing circulating device, and the pinacol in the tail gas is further removed, then enters the second acid mist eliminator 22 to filter and recover the hydrochloric acid in the tail gas, and the dry tail gas enters the falling film absorber 10 of the primary water circulating absorption device, the filtered hydrochloric acid returns to the second washing circulating tank 8, the hydrogen chloride in the tail gas is cooled and condensed into hydrochloric acid by the falling film absorber 10, and is dissolved in water in the primary water washing absorption tank 11 and is repeatedly circulated, the falling film absorber 10 cools the tail gas by the flow of cooling water, when the concentration of hydrochloric acid in the primary water washing absorption tank 11 is greater than 36%, the tail gas enters the secondary water circulating absorption device in turn, and finally enters the tertiary water circulating absorption device, at the same time, when the concentration of hydrochloric acid in the tertiary water washing absorption tank 13 is greater than 36%, the tail gas is discharged into the secondary water washing absorption tank 12 in turn, and finally enters the primary water washing absorption tank 11, and is discharged by the transfer pump 14 and recovered to the storage tank, at the same time, water is supplemented to the tertiary water washing absorption tank 13, and finally enters the second packing absorption tower 17 of the alkali absorption device to make the tail gas fully undergo acid-base neutralization reaction in the alkali absorption tank 18, and is discharged after repeated circulation.

[0031] The above-described embodiments are only descriptions of the preferred embodiments of the present application, and do not limit the scope of the present application, and various modifications and improvements of the technical solutions of the present application made without departing from the design spirit of the present application shall fall within the protection scope determined by the claims of the present application.

Claims

1. A dichlorpinacol tail gas purification and hydrochloric acid recovery system, comprising a plant tail gas discharge pipe, characterized in that: The first acid mist eliminator is connected with a collecting tank for collecting pinacol liquid drops, and the gas outlet end of the first acid mist eliminator is communicated with a first washing circulating device, which is further communicated with a second washing circulating device. The second washing circulating device is communicated with a water circulating absorption device for recovering hydrochloric acid, which comprises a first-stage water circulating absorption device, a second-stage water circulating absorption device and a third-stage water circulating absorption device. The first washing circulating device comprises a first packed tower, a first washing circulating tank and a first cooling device, which are sequentially connected to form a loop.

2. The dichlorpinacol off-gas purification and hydrochloric acid recovery system of claim 1, wherein: The first-stage water circulating absorption device comprises a first cooling absorption device and a first-stage water washing absorption tank, which are sequentially connected to form a loop.

3. The dichlorpinacol off-gas purification and hydrochloric acid recovery system of claim 2, wherein: The alkali absorption device comprises a second packed tower and an alkali absorption tank, which are sequentially connected to form a loop.

4. The dichlorpinacol off-gas purification and hydrochloric acid recovery system of claim 3, wherein: The first cooling device comprises a graphite cooler, and the first cooling absorption device comprises a falling film absorber.

5. The dichlorpinacol off-gas purification and hydrochloric acid recovery system of claim 4, wherein: The second acid mist eliminator is also provided between the second washing circulating device and the first-stage water circulating absorption device.

6. The dichlorpinacol off-gas purification and hydrochloric acid recovery system of claim 5, wherein: The primary water washing absorption tank is provided with a recovery outlet which is communicated with a recovery tank through a recovery pipeline, and the primary water washing absorption tank is communicated with a secondary water washing absorption tank of a secondary water circulation absorption device and a tertiary water washing absorption tank of a tertiary water circulation absorption device through a transfer pipeline in sequence, the transfer pipeline is provided with a transfer pump, and the tertiary water washing absorption tank is communicated with a water inlet pipeline.

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