Treatment method and system applied to waste gas containing high-concentration dichloromethane

Abstract

The invention relates to the technical field of waste gas treatment, and particularly discloses a method and system for treating waste gas containing high-concentration dichloromethane, the system comprises a precooler, an absorption system, a regeneration system and a receiving tank, the absorption system is composed of an absorption tower, a heat exchanger and a recooler, and the precooler is connected with a lower inlet pipeline of the absorption tower; a booster fan is arranged in a pipeline through which the precooler is communicated with the absorption tower, a bottom outlet of the absorption tower is connected with a first inlet pipeline of the heat exchanger, a gas discharge port is formed in the top of the absorption tower, the regeneration system comprises a regeneration tower, a condenser and a reboiler, and a first outlet of the heat exchanger is connected with a middle inlet pipeline of the regeneration tower. The device has the characteristics that high-concentration dichloromethane waste gas can be stably and continuously treated, the absorbent does not need to be replaced, and energy conservation and consumption reduction are realized.

Description

Technical Field

[0001] The invention relates to the technical field of waste gas treatment, and in particular to a method and a system for treating waste gas containing high concentration of dichloromethane. Background Art

[0002] Dichloromethane is a commonly used solvent, widely used in industries such as medicine and fine chemicals. The characteristics of waste gas emissions in this industry are intermittent emissions and extremely high concentrations, which can even reach saturated concentrations. The current mainstream treatment processes are activated carbon / resin adsorption + water vapor desorption, etc. Although activated carbon and resin can effectively adsorb dichloromethane, their treatment efficiency is usually not enough to cope with high-concentration or large-flow waste gas, which means that under high load conditions, the adsorption material may need to be frequently replaced or regenerated, thereby increasing operating costs; after the adsorption process is completed, the saturated activated carbon or resin needs to be desorbed. Although water vapor desorption can recover some dichloromethane, the wastewater generated in this process may contain high concentrations of organic matter or other pollutants, which may cause secondary pollution problems and increase the complexity and cost of subsequent treatment.

[0003] The use of conventional regenerative heat incinerators will bring the problem of dioxin, a strong carcinogen that has serious impacts on the environment and health. Therefore, additional treatment measures are needed to control its generation. Incineration will produce a large amount of HCl, which is highly corrosive and requires special corrosion-resistant materials for equipment manufacturing. The equipment has high requirements for materials and huge investments. In addition, intermittent and unstable emissions pose a major safety hazard. Summary of the invention

[0004] In order to solve the above problems existing in the prior art, the present invention provides a method and system for treating waste gas containing high concentration of dichloromethane, which has the characteristics of being able to stably and continuously treat high concentration of dichloromethane waste gas without replacing absorbent and saving energy and reducing consumption.

[0005] The purpose of the present invention can be achieved through the following technical solutions: A system for treating waste gas containing high concentration of dichloromethane comprises a precooler, an absorption system, a regeneration system and a receiving tank, wherein the absorption system consists of an absorption tower, a heat exchanger and a recooler, the precooler is connected to the lower inlet pipeline of the absorption tower, a booster fan is arranged in the pipeline communicating between the precooler and the absorption tower, the bottom outlet of the absorption tower is connected to the first inlet pipeline of the heat exchanger, the regeneration system comprises a regeneration tower, a condenser and a reboiler, the first outlet of the heat exchanger is connected to the middle inlet pipeline of the regeneration tower, the top outlet of the regeneration tower is connected to the inlet pipeline of the condenser, and the outlet of the condenser is connected to the receiving tank pipeline.

[0006] Preferably, the first bottom outlet of the regeneration tower is connected to the second inlet pipeline of the heat exchanger, the second outlet of the heat exchanger is connected to the inlet pipeline of the subcooler, and the outlet of the subcooler is connected to the upper inlet pipeline of the absorption tower.

[0007] Preferably, the second bottom outlet of the regeneration tower is connected to the inlet pipeline of the reboiler, and the outlet of the reboiler is connected to the bottom inlet pipeline of the regeneration tower.

[0008] Preferably, a feed inlet is provided at the upper portion of the reboiler, and a discharge port is provided at the lower portion of the reboiler.

[0009] Preferably, the top outlet of the absorption tower is connected to a gas exhaust pipeline.

[0010] Preferably, a sprayer is provided at the inner top of the absorption tower.

[0011] A method for treating waste gas containing high concentration of dichloromethane comprises the following steps: Treatment of dichloromethane waste gas: S1: passing the dichloromethane waste gas into a precooler for preliminary condensation; S2: The dichloromethane waste gas after preliminary condensation is introduced into the absorption tower through a booster fan, and the sprayer at the top of the absorption tower sprays the absorbent down. The absorbent captures and absorbs the dichloromethane waste gas after preliminary condensation and then falls into the bottom of the absorption tower to obtain absorbent rich liquid and exhaust gas, which is discharged through a gas exhaust pipeline; S3: The absorbent rich liquid is passed into the heat exchanger for heat exchange heating, and then passed into the regeneration tower; S4: The regeneration tower uses steam generated and introduced through a reboiler to further heat the heated absorbent rich liquid, desorbing dichloromethane from the absorbent rich liquid to obtain dichloromethane and absorbent; S5: passing the dichloromethane into a condenser for condensation to obtain liquefied dichloromethane, and passing the liquefied dichloromethane into a receiving tank for recovery; Recycling absorbent: S6: the absorbent obtained in S4 is reintroduced into the heat exchanger, and the absorbent exchanges heat with the absorbent rich liquid for cooling; S7: The absorbent after heat exchange and cooling is passed into a recooler for further cooling, and then passed into an absorption tower for recycling.

[0012] Preferably, in S1, the dichloromethane waste gas is preliminarily condensed to a temperature of -15 to 15°C, and in S4, the temperature of the heating analysis in the regeneration tower is 70 to 110°C.

[0013] Preferably, in S5, dichloromethane is condensed to a temperature of -10 to 10°C, and in S7, the absorbent is further cooled to a temperature of -15 to 10°C.

[0014] Preferably, in S2, the absorbent comprises 30-50% by mass of alkyl benzoate, 10-20% by mass of fatty alcohol polyoxyethylene alcohol and 30-60% by mass of long carbon chain amide.

[0015] The device of the present invention uses a circulation system, and there is no need to replace the absorbent when the device is working. The absorbent captures and absorbs dichloromethane waste gas in the absorption tower to obtain an absorbent rich liquid, which is preliminarily heated through a heat exchanger and heated and resolved in a regeneration tower to obtain dichloromethane and absorbent. At this time, the absorbent is recycled and passed into the heat exchanger again, and the subsequent absorbent rich liquid is heated by heat exchange while the absorbent itself is cooled by heat exchange, which reduces the time and energy required for cooling the absorbent in the recooler. The absorbent rich liquid is first heated in the heat exchanger and then passed into the regeneration tower for heating and resolution again, which also reduces the time and energy required for heating the absorbent rich liquid in the regeneration tower, improves the overall processing efficiency of the device, and can reduce energy consumption.

[0016] The present invention uses an absorbent composed of alkyl benzoate, fatty alcohol polyoxyethylene alcohol and long carbon chain amide for dichloromethane waste gas, and has the characteristics of low viscosity, high boiling point, low freezing point and high miscibility with dichloromethane. Alkyl benzoate has good solubility and lipophilicity, and can form a stable mixture with dichloromethane. Fatty alcohol polyoxyethylene alcohol helps to reduce the surface tension of dichloromethane through its surface activity, thereby improving the absorption efficiency; long carbon chain amide can provide a large surface area due to its long carbon chain structure, increase the contact area with dichloromethane, thereby improving the absorption effect, and the synergistic effect of these components enables the absorbent to efficiently absorb dichloromethane.

[0017] The configuration of the present invention ensures that the exhaust gas obtained after the dichloromethane waste gas is absorbed by the absorbent in the absorption tower can meet the emission standards, can continuously, stably and efficiently absorb and treat the dichloromethane waste gas, and can subsequently recover the dichloromethane through simple treatment, which has high economic benefits. The present invention recovers and treats the dichloromethane by means of absorbent absorption, condensation and steam heating, and basically has no secondary pollution, so the present invention is suitable for industrial application.

[0018] The beneficial effects of the present invention are: The device of the present invention uses a circulation system, and there is no need to replace the absorbent when the device is working. The absorbent can be recycled and heat-exchanged to heat the absorbent rich liquid, and heat-exchanged to cool itself, thereby reducing the time and energy required for cooling the absorbent in the recooler, and also reducing the time and energy required for heating the absorbent rich liquid in the regeneration tower, thereby improving the overall processing efficiency of the device and reducing energy consumption.

[0019] The present invention uses an absorbent comprising alkyl benzoate, fatty alcohol polyoxyethylene alcohol and long carbon chain amide for dichloromethane waste gas, and the absorbent has the characteristics of low viscosity, high boiling point, low freezing point and high miscibility with dichloromethane. The synergistic effect between the components enables the absorbent to efficiently absorb dichloromethane.

[0020] The configuration of the present invention ensures that the exhaust gas obtained after the dichloromethane waste gas is absorbed by the absorbent in the absorption tower can meet the emission standards, can continuously, stably and efficiently absorb and treat the dichloromethane waste gas, and can subsequently recover the dichloromethane through simple treatment, which has high economic benefits. The present invention recovers and treats the dichloromethane by means of absorbent absorption, condensation and steam heating, and basically has no secondary pollution, so the present invention is suitable for industrial application. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to facilitate understanding by those skilled in the art, the present invention is further described below with reference to the accompanying drawings.

[0022] Figure 1 It is a schematic diagram of the processing flow of the device of the present invention; Description of main component symbols: In the figure: 1. Precooler; 2. Absorption tower; 3. Heat exchanger; 4. Regeneration tower; 5. Condenser; 6. Receiving tank; 7. Reboiler; 8. Recooler. DETAILED DESCRIPTION

[0023] In order to further explain the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the specific implementation methods, structures, features and effects of the present invention are clearly and completely described below in combination with the accompanying drawings and preferred embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0024] In the description of the present application, it should be understood that the orientation or position relationship indicated by "inside" or "outside" is based on the orientation or position described in the drawings, which is only for the convenience of describing the present application and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, specific orientation structure and operation, and therefore cannot be understood as a limitation on the present application.

[0025] Example 1 Reference Figure 1 The present invention discloses a system for treating waste gas containing high concentration of dichloromethane, comprising a precooler 1, an absorption system, a regeneration system and a receiving tank 6. The absorption system consists of an absorption tower 2, a heat exchanger 3 and a recooler 8. The precooler 1 is connected to the lower inlet pipeline of the absorption tower 2. A booster fan is arranged in the pipeline connecting the precooler 1 and the absorption tower 2. The bottom outlet of the absorption tower 2 is connected to the first inlet pipeline of the heat exchanger 3. The regeneration system comprises a regeneration tower 4, a condenser 5 and a reboiler 7. The first outlet of the heat exchanger 3 is connected to the middle inlet pipeline of the regeneration tower 4, the top outlet of the regeneration tower 4 is connected to the inlet pipeline of the condenser 5, and the outlet of the condenser 5 is connected to the receiving tank 6 pipeline.

[0026] Reference Figure 1 The first bottom outlet of the regeneration tower 4 is connected to the second inlet pipeline of the heat exchanger 3, the second outlet of the heat exchanger 3 is connected to the inlet pipeline of the subcooler 8, and the outlet of the subcooler 8 is connected to the upper inlet pipeline of the absorption tower 2; the second bottom outlet of the regeneration tower 4 is connected to the inlet pipeline of the reboiler 7, and the outlet of the reboiler 7 is connected to the bottom inlet pipeline of the regeneration tower 4; a feed inlet is provided at the upper part of the reboiler 7, and a discharge port is provided at the lower part of the reboiler 7; the top outlet of the absorption tower 2 is connected to the gas exhaust pipeline; a sprayer is provided at the top of the absorption tower 2.

[0027] Example 2 The absorbent used in this embodiment is composed of 40% by mass of alkyl benzoate, 20% by mass of fatty alcohol polyoxyethylene alcohol and 40% by mass of long carbon chain amide.

[0028] A method for treating waste gas containing high concentration of dichloromethane, using the system in Example 1, comprises the following steps: Treatment of dichloromethane waste gas: the waste gas volume of dichloromethane is 1000 m³ / h, and the dichloromethane content is 50000~100000ppm; S1: passing the dichloromethane waste gas into the precooler 1 for preliminary condensation to -10°C; S2: The dichloromethane waste gas after preliminary condensation is introduced into the absorption tower 2 through the booster fan, and the sprayer at the top of the absorption tower 2 sprays the absorbent down, and the absorbent captures and absorbs the dichloromethane waste gas after pre-cooling and falls into the bottom of the absorption tower 2 to obtain the absorbent rich liquid and exhaust gas, and the exhaust gas is discharged through the gas exhaust pipeline; S3: The absorbent rich liquid is passed into the heat exchanger 3 for heat exchange heating, and then passed into the regeneration tower 4; S4: The heated absorbent rich liquid is further heated by using steam generated and introduced into the regeneration tower 4 via the reboiler 7 to decompose dichloromethane from the absorbent rich liquid. The heating decomposition temperature is 100° C. to obtain dichloromethane and absorbent. S5: passing the dichloromethane into the condenser 5 for condensation to -5°C to obtain liquefied dichloromethane, and passing the liquefied dichloromethane into the receiving tank 6 for recovery; Recycling absorbent: S6: the absorbent obtained in S4 is introduced back into the heat exchanger 3, and the absorbent exchanges heat with the absorbent rich liquid to reduce the temperature; S7: The absorbent after heat exchange and cooling is passed into the recooler 8 to be further cooled to -10°C, and then passed into the top of the absorption tower 2 for recycling.

[0029] In this embodiment, the dichloromethane in the exhaust gas is less than 50 mg / m³.

[0030] Example 3 The absorbent used in this embodiment is composed of 40% by mass of alkyl benzoate, 20% by mass of fatty alcohol polyoxyethylene alcohol and 40% by mass of long carbon chain amide.

[0031] Treatment of dichloromethane waste gas: dichloromethane waste gas volume 2000m³ / h, dichloromethane content 1000~2000ppm, outlet dichloromethane content <30mg / m³; S1: passing the dichloromethane waste gas into the precooler 1 for preliminary condensation to -5°C; S2: The dichloromethane waste gas after preliminary condensation is passed into the absorption tower 2 through the booster fan, and the sprayer at the top of the absorption tower 2 sprays the absorbent down, and the absorbent captures and absorbs the dichloromethane waste gas after pre-cooling treatment and then falls into the bottom of the absorption tower 2 to obtain the absorbent rich liquid and exhaust gas, and the exhaust gas is discharged through the gas exhaust pipeline; S3: The absorbent rich liquid is passed into the heat exchanger 3 for heat exchange heating, and then passed into the regeneration tower 4; S4: The heated absorbent rich liquid is further heated by using steam generated and introduced into the regeneration tower 4 via the reboiler 7 to decompose dichloromethane from the absorbent rich liquid. The heating decomposition temperature is 100° C. to obtain dichloromethane and absorbent. S5: passing the dichloromethane into the condenser 5 for condensation to -5°C to obtain liquefied dichloromethane, and passing the liquefied dichloromethane into the receiving tank 6 for recovery; Recycling absorbent: S6: the absorbent obtained in S4 is introduced back into the heat exchanger 3, and the absorbent exchanges heat with the absorbent rich liquid to reduce the temperature; S7: The absorbent after heat exchange and cooling is passed into the recooler 8 to be further cooled to -5°C, and then passed into the top of the absorption tower 2 for recycling.

[0032] In this embodiment, the dichloromethane in the exhaust gas is less than 30 mg / m³.

[0033] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technical personnel in this field can make some changes or modify the technical contents disclosed above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any brief modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A system for treating waste gas containing high concentration of dichloromethane, characterized in that: The invention comprises a precooler (1), an absorption system, a regeneration system and a receiving tank (6), wherein the absorption system comprises an absorption tower (2), a heat exchanger (3) and a recooler (8), wherein the precooler (1) is connected to the lower inlet pipeline of the absorption tower (2), a booster fan is arranged in the pipeline connecting the precooler (1) and the absorption tower (2), the bottom outlet of the absorption tower (2) is connected to the first inlet pipeline of the heat exchanger (3), the regeneration system comprises a regeneration tower (4), a condenser (5) and a reboiler (7), the first outlet of the heat exchanger (3) is connected to the middle inlet pipeline of the regeneration tower (4), the top outlet of the regeneration tower (4) is connected to the inlet pipeline of the condenser (5), and the outlet of the condenser (5) is connected to the pipeline of the receiving tank (6).

2. The method according to claim 1, wherein the method is applied to a system for treating waste gas containing high concentration of dichloromethane, characterized in that: The first bottom outlet of the regeneration tower (4) is connected to the second inlet pipeline of the heat exchanger (3), the second outlet of the heat exchanger (3) is connected to the inlet pipeline of the subcooler (8), and the outlet of the subcooler (8) is connected to the upper inlet pipeline of the absorption tower (2).

3. The method according to claim 2 is applied to a system for treating waste gas containing high concentration of dichloromethane, characterized in that: The second bottom outlet of the regeneration tower (4) is connected to the inlet pipeline of the reboiler (7), and the outlet of the reboiler (7) is connected to the bottom inlet pipeline of the regeneration tower (4).

4. The method according to claim 1, wherein the method is applied to a system for treating waste gas containing high concentration of dichloromethane, characterized in that: The upper portion of the reboiler (7) is provided with a feed inlet, and the lower portion of the reboiler (7) is provided with a discharge outlet.

5. The method according to claim 1, wherein: The top outlet of the absorption tower (2) is connected to a gas exhaust pipeline.

6. The method according to claim 5, wherein the method is applied to a system for treating waste gas containing high concentration of dichloromethane, characterized in that: A sprayer is provided at the top of the interior of the absorption tower (2).

7. A method for treating waste gas containing high concentration of dichloromethane, which is implemented based on a system for treating waste gas containing high concentration of dichloromethane as claimed in any one of claims 1 to 6, characterized in that: The steps include: Treatment of dichloromethane waste gas: S1: passing the dichloromethane waste gas into a precooler (1) for preliminary condensation; S2: The dichloromethane waste gas after the preliminary condensation is introduced into the absorption tower (2) through a booster fan, and the sprayer at the top of the absorption tower (2) sprays the absorbent down, and the absorbent captures and absorbs the dichloromethane waste gas after the preliminary condensation and then falls into the bottom of the absorption tower (2), thereby obtaining an absorbent-rich liquid and exhaust gas, and the exhaust gas is discharged through a gas exhaust pipeline; S3: passing the absorbent rich liquid into the heat exchanger (3) for heat exchange heating, and then passing it into the regeneration tower (4); S4: the regeneration tower (4) uses steam generated and introduced via the reboiler (7) to further heat the heated absorbent rich liquid, thereby desorbing dichloromethane from the absorbent rich liquid to obtain dichloromethane and absorbent; S5: passing dichloromethane into a condenser (5) for condensation to obtain liquefied dichloromethane, and passing the liquefied dichloromethane into a receiving tank (6) for recovery; Recycling absorbent: S6: the absorbent obtained in S4 is introduced back into the heat exchanger (3), and the absorbent exchanges heat with the absorbent rich liquid to reduce the temperature; S7: The absorbent after heat exchange and temperature reduction is passed into a recooler (8) for further cooling, and then passed into an absorption tower (2) for recycling.

8. The method for treating waste gas containing high concentration of dichloromethane according to claim 7, characterized in that: In the S1, the dichloromethane waste gas is preliminarily condensed to a temperature of -15 to 15°C. In the S4, the temperature of the heating analysis in the regeneration tower is 70 to 110°C.

9. The method for treating waste gas containing high concentration of dichloromethane according to claim 7, characterized in that: In the step S5, dichloromethane is condensed to a temperature of -10 to 10°C, and in the step S7, the absorbent is further cooled to a temperature of -15 to 10°C.

10. The method for treating waste gas containing high concentration of dichloromethane according to claim 7, characterized in that: In the S2, the absorbent includes 30-50% by mass of alkyl benzoate, 10-20% by mass of fatty alcohol polyoxyethylene alcohol and 30-60% by mass of long carbon chain amide.

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