Chloromethane purification system

Abstract

The utility model discloses a chloromethane purification system, which is used for treating gas-phase chloromethane recovered in a methyl chlorosilane monomer process, and comprises: a chloromethane tower, in which pressurized gas-phase chloromethane enters the chloromethane tower for recovery; the acid treatment unit comprises at least one sulfuric acid tower, gas-phase chloromethane in the chloromethane tower is conveyed to the sulfuric acid tower, and olefin entrained in the gas-phase chloromethane is absorbed by the sulfuric acid tower; and the gas-phase chloromethane passing through the acid treatment unit is conveyed to the first condensing equipment to be condensed and recycled. According to the chloromethane recovery system provided by the invention, the recovered chloromethane has relatively high purity, so that the economic benefit is enhanced, the production cost is reduced, and the safety of the system is improved.

Description

Technical Field

[0001] This application relates to the field of organosilicon, specifically to a purification system for chloromethane. Background Technology

[0002] Methylchlorosilane monomers are a core raw material in the organosilicon industry, mainly used in the production of organosilicon products such as silicone oil, silicone rubber, and silicone resin. The synthesis process primarily employs a direct synthesis method, which involves reacting silicon powder and chloromethane as raw materials in a fluidized bed reactor under high temperature and pressure using a copper-based catalyst. Chloromethane is a crucial reaction medium, but due to its low single-pass conversion rate, unreacted chloromethane needs to be recovered and reused.

[0003] In the synthesis of methylchlorosilane monomers, the syngas output from the fluidized bed reactor first passes through a cyclone separator to remove solid particles such as silicon powder and copper powder. Subsequently, the syngas enters a scrubbing tower for further impurity removal through condensation and washing. However, the chloromethane recovered using existing technologies still contains a certain amount of impurities, which can affect the reactivity of subsequent reactions. Therefore, improving the quality of the recovered chloromethane is a problem that needs to be addressed. Summary of the Invention

[0004] One objective of this application is to improve the purity of recovered gaseous chloromethane, reduce production costs, and increase economic benefits.

[0005] Another objective of this application is to improve the safety and environmental friendliness of organosilicon production, which is beneficial to extending the service life of the production system.

[0006] To achieve the above objectives, the technical solution adopted in this application is: a chloromethane purification system for treating gaseous chloromethane recovered in the methylchlorosilane monomer process, comprising:

[0007] Chloromethane tower: Pressurized gaseous chloromethane enters the chloromethane tower for recovery;

[0008] An acid treatment unit includes at least one sulfuric acid tower, wherein gaseous chloromethane in the chloromethane tower is conveyed to the sulfuric acid tower, and olefins entrained in the gaseous chloromethane are absorbed by the sulfuric acid tower.

[0009] In the first condensation unit, the gaseous chloromethane from the acid treatment unit is transported to the first condensation unit for condensation and recovery.

[0010] In some embodiments, the purification system further includes a second condensation device connected to the chloromethane tower, which condenses and recovers chloromethane from the chloromethane tower when the acid treatment unit is out of service or malfunctions.

[0011] In some embodiments, the acid treatment unit includes a first sulfuric acid tower and a second sulfuric acid tower connected in series, wherein the concentration of sulfuric acid in the first sulfuric acid tower is less than the concentration of sulfuric acid in the second sulfuric acid tower, and the gaseous chloromethane from the chloromethane tower passes through the first sulfuric acid tower first and then through the second sulfuric acid tower.

[0012] In some embodiments, the first sulfuric acid tower is provided with an acid discharge port, and the second sulfuric acid tower is provided with a sulfuric acid replenishment port. The sulfuric acid replenishment port is used to input sulfuric acid into the sulfuric acid tower, and the acid discharge port is used to discharge the acid liquid in the sulfuric acid tower. The second sulfuric acid tower is connected to the first sulfuric acid tower so that the sulfuric acid in the second sulfuric acid tower can be replenished into the first sulfuric acid tower.

[0013] In some embodiments, the first sulfuric acid tower is equipped with a first acidity detection device, and a first switch valve is provided on the connecting pipeline between the second sulfuric acid tower and the first sulfuric acid tower. The first acidity detection device is communicatively connected to the first switch valve so that the first switch valve is opened when the sulfuric acid concentration in the first sulfuric acid tower is lower than a preset value.

[0014] In some embodiments, the second sulfuric acid tower is equipped with a second acidity detection device, which is communicatively connected to the switch valve of the sulfuric acid replenishment port so that when the sulfuric acid concentration in the second sulfuric acid tower is lower than a preset value, the switch valve of the sulfuric acid replenishment port is opened.

[0015] In some embodiments, the chloromethane tower is equipped with a reboiler for heat exchange, so that the temperature of the gaseous chloromethane input to the acid treatment unit is 35°C to 45°C.

[0016] In some embodiments, the acid treatment unit further includes a demister for receiving chloromethane discharged from the sulfuric acid tower and removing sulfuric acid from the chloromethane.

[0017] In some embodiments, a third condenser is connected to the top of the chloromethane tower, and the condensate from the third condenser is returned to the chloromethane tower, while the tail gas enters the tail gas treatment system.

[0018] Compared with the prior art, the beneficial effects of this application are as follows:

[0019] (1) The chloromethane purification system of this application, through the series of sulfuric acid towers of different concentrations connected in series and controlled in real time, effectively improves the removal efficiency of impurities in chloromethane, which is conducive to improving the purity of chloromethane, reducing production costs, and further enhancing economic benefits.

[0020] (2) The chloromethane purification system of this application, through the sulfuric acid tower, effectively improves the safety and environmental protection of the organosilicon production process, extends the service life of the system, and reduces maintenance costs. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the structure of a chloromethane purification system in one embodiment of this application.

[0022] In the diagram: 100, fluidized bed; 110, cyclone separation system; 200, washing tower; 210, compression equipment; 220, reboiler; 230, reflux equipment; 240, tail gas treatment equipment; 250, chloromethane tower; 310, first condenser; 320, second condenser; 330, third condenser; 340, fourth condenser; 410, first recovery equipment; 420, second recovery equipment; 510, first sulfuric acid tower; 520, second sulfuric acid tower; 610, first acidity detection equipment; 620, second acidity detection equipment; 700, sulfuric acid replenishment port; 800, acid discharge port; 900, demister. Detailed Implementation

[0023] The present application will be further described below with reference to specific embodiments. It should be noted that, without conflict, the various embodiments or technical features described below can be arbitrarily combined to form new embodiments.

[0024] In the description of this application, it should be noted that the terms "center", "lateral", "longitudinal", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc., which indicate the orientation and positional relationship based on the orientation or positional relationship shown in the accompanying drawings, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and should not be construed as limiting the specific protection scope of this application.

[0025] It should be noted that the terms "first," "second," etc., in the specification and claims of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence.

[0026] The terms “comprising” and “having”, and any variations thereof, in the specification and claims of this application are intended to cover non-exclusive inclusion, for example, a process, method, system, product, or device that includes a series of steps or units is not necessarily limited to those steps or units that are explicitly listed, but may include other steps or units that are not explicitly listed or that are inherent to such process, method, product, or device.

[0027] This invention relates to a chloromethane recovery system for organosilicon production processes. It treats the uncondensed gas produced after the fluidized bed reactor (100) has undergone washing and dust removal by a cyclone separator (110) and a scrubbing tower (200), and is subsequently condensed. The uncondensed gas includes incompletely condensed gaseous chloromethane, nitrogen, olefins, and alkanes. In existing technologies, multi-stage condensers are typically used to precisely control the condensation temperature to ensure effective condensation and separation of components such as gaseous chloromethane. However, excessively high or low condensation temperatures can affect the recovery efficiency of gaseous chloromethane, and multi-stage condensers require regular cleaning and maintenance to prevent fouling on the inner walls, which can impair heat transfer efficiency. Scale buildup leads to decreased condensation efficiency and further increases energy consumption. This separation method involves high equipment investment and maintenance costs, significant operational complexity, and limited recovery efficiency, making it difficult to recover high-purity gaseous chloromethane.

[0028] This application aims to provide a purification system for chloromethane, such as... Figure 1 As shown, the method for treating gaseous chloromethane recovered in the methylchlorosilane monomer process includes:

[0029] In chloromethane tower 250, pressurized gaseous chloromethane enters for recovery. It is understood that uncondensed gas is conveyed via compression device 210 to the fourth condensation device 340. The uncondensed gas is condensed and separated to obtain a mixture of chloromethane, nitrogen, and alkanes. The chloromethane is then sent to the recovery device, while the nitrogen and alkanes in the mixture are sent to the tail gas treatment device 240, further reducing environmental pollution, improving production safety, and increasing tail gas treatment efficiency, ensuring the safety and environmental friendliness of the tail gas treatment process. The mixture of chloromethane and olefins is sent to the acid treatment unit for separation of chloromethane and olefins, further improving the purity of the chloromethane, which is beneficial for recovery and reuse.

[0030] An acid treatment unit includes at least one sulfuric acid tower. Gaseous chloromethane in a chloromethane tower 250 is conveyed to the sulfuric acid tower, and olefins entrained in the gaseous chloromethane are absorbed by the sulfuric acid tower. The olefins in the first mixture are removed by sulfuric acid, which further improves the purity of the recovered chloromethane, making it easier to reuse in the production process and reducing costs.

[0031] In the first condensation unit 310, gaseous chloromethane from the acid treatment unit is transported to the first condensation unit 310 for condensation and recovery. It is understood that cooling the high-temperature gas to a lower temperature, causing it to partially or completely liquefy, facilitates separation.

[0032] The recycling equipment includes a first recycling device 410 and a second recycling device 420, wherein the first recycling device 410 is adapted to receive chloromethane obtained by condensation in a chloromethane tower 250, and the second recycling device 420 is adapted to receive chloromethane obtained after treatment in an acid treatment unit.

[0033] In some embodiments, the purification system further includes a second condenser 320 connected to the chloromethane tower 250. The second condenser 320 condenses and recovers chloromethane from the chloromethane tower 250 when the acid treatment unit is shut down or malfunctions. Specifically, the second condenser 320 is connected to the first recovery device 410 and can be considered a protection unit. When the acid treatment unit malfunctions, the chloromethane in the chloromethane tower 250 is directly recovered through this protection unit, further ensuring production safety.

[0034] In some embodiments, the acid treatment unit includes a first sulfuric acid tower 510 and a second sulfuric acid tower 520 connected in series. The concentration of sulfuric acid in the first sulfuric acid tower 510 is lower than that in the second sulfuric acid tower 520. The gaseous chloromethane from the chloromethane tower 250 first passes through the first sulfuric acid tower 510 and then through the second sulfuric acid tower 520. Specifically, by separately setting sulfuric acid towers with different sulfuric acid concentrations, the sulfuric acid concentration and flow rate distribution of the two towers can be flexibly adjusted according to the concentration changes of olefins in the input first mixture. The first sulfuric acid tower 510 first removes propylene, while the second sulfuric acid tower 520 deeply purifies major impurities such as butene and ethylene, avoiding the problem of insufficient selectivity of a single concentration of sulfuric acid for complex components, and is suitable for intermittent or variable operating scenarios in organosilicon production. In other words, the byproducts produced after reacting with various olefins in the two separately set sulfuric acid towers are different. Therefore, by staged reactions, the byproducts produced by different sulfuric acid towers can be collected in a targeted manner, such as the alkylation products of the first sulfuric acid tower 510 and the sulfate ester products of the second sulfuric acid tower 520, simplifying the subsequent recovery or treatment process.

[0035] In some embodiments, the sulfuric acid concentration in the first sulfuric acid tower 510 is 30 wt.% to 60 wt.%, and the sulfuric acid concentration in the second sulfuric acid tower 520 is 80 wt.% to 95 wt.%. Specifically, the sulfuric acid concentration in the first sulfuric acid tower 510 is 30 wt.%, 35 wt.%, 40 wt.%, 45 wt.%, 50 wt.%, 55 wt.%, or 60 wt.%. The sulfuric acid concentration in the second sulfuric acid tower 520 is 80 wt.% to 95 wt.%, specifically, the sulfuric acid concentration in the second sulfuric acid tower 520 is 80 wt.%, 81 wt.%, 82 wt.%, 83 wt.%, 84 wt.%, 85 wt.%, 86 wt.%, 87 wt.%, 88 wt.%, 89 wt.%, 90 wt.%, 91 wt.%, 92 wt.%, 93 wt.%, 94 wt.%, or 95 wt.%. By using two sulfuric acid towers connected in series, at least 90 wt.% of olefins can be removed from the first mixture.

[0036] It is understandable that olefins typically contain carbon-carbon double bonds (C=C), which are highly reactive and capable of undergoing addition reactions with sulfuric acid. The specific details of the reaction depend on the concentration of sulfuric acid and the reaction conditions. Specifically, the acid treatment unit includes a first sulfuric acid tower 510 with a lower sulfuric acid concentration and a second sulfuric acid tower 520 with a higher sulfuric acid concentration, connected in series. The first sulfuric acid tower 510 preferentially reacts with some of the more reactive olefins, such as propylene and butene, in alkylation or addition reactions, reducing the consumption of high-concentration sulfuric acid in the second sulfuric acid tower 520. This further reduces the risk of violent exothermic reactions or side reactions, such as polymerization or coking, caused by excessively high sulfuric acid concentrations, thus lowering the risk of runaway reactions. On one hand, because the first sulfuric acid tower 510 processes most of the olefins first, the consumption of high-concentration sulfuric acid in the second sulfuric acid tower 520 is significantly reduced, lowering raw material costs. On the other hand, by conducting more exothermic reactions in the first sulfuric acid tower 510, the violent reactions between high-concentration sulfuric acid and olefins in the second sulfuric acid tower 520 are avoided, reducing the risk of explosions or equipment damage and extending the equipment's service life.

[0037] In some embodiments, the first sulfuric acid tower 510 is provided with an acid discharge port 800, and the second sulfuric acid tower 520 is provided with a sulfuric acid replenishment port 700. The sulfuric acid replenishment port 700 is used to feed sulfuric acid into the sulfuric acid tower, and the acid discharge port 800 is used to discharge the acid liquid in the sulfuric acid tower. The second sulfuric acid tower 520 is connected to the first sulfuric acid tower 510 so that the sulfuric acid in the second sulfuric acid tower 520 can replenish the first sulfuric acid tower 510. It is understood that because the first sulfuric acid tower 510 reacts extensively with olefins, it consumes a significant amount of sulfuric acid while generating byproducts. Therefore, it is necessary to discharge the waste liquid in the tower to ensure the removal of olefins in the first sulfuric acid tower 510. On the other hand, because the sulfuric acid in the sulfuric acid tower is continuously consumed, it is necessary to add sulfuric acid to the sulfuric acid tower to ensure that the sulfuric acid is maintained at a certain concentration, which is beneficial for enhancing the removal of olefins. By connecting the second sulfuric acid tower 520 to the first sulfuric acid tower 510, the sulfuric acid in the second sulfuric acid tower 520 can be replenished to the first sulfuric acid tower 510, which helps to maintain the concentration in the first sulfuric acid tower 510, enhances the removal of olefins, and further increases the purity of the recovered chloromethane.

[0038] In some embodiments, the first sulfuric acid tower 510 is equipped with a first acidity detection device 610, and a first switching valve is provided on the connecting pipeline between the second sulfuric acid tower 520 and the first sulfuric acid tower 510. The first acidity detection device 610 is communicatively connected to the first switching valve so that the first switching valve is opened when the sulfuric acid concentration in the first sulfuric acid tower 510 is lower than a preset value. It is understood that by using the provided acidity detection device to monitor the sulfuric acid concentration in the first sulfuric acid tower 510 in real time, it is beneficial to accurately control the sulfuric acid concentration in the tower and enhance the removal of olefins.

[0039] In some embodiments, the second sulfuric acid tower 520 is equipped with a second acidity detection device 620, which is communicatively connected to the switch valve of the sulfuric acid replenishment port 700. This allows the switch valve of the sulfuric acid replenishment port 700 to be opened when the sulfuric acid concentration in the second sulfuric acid tower 520 falls below a preset value. It is understood that real-time monitoring of the sulfuric acid concentration in the sulfuric acid tower via the provided acidity detection device facilitates precise control of the concentration, enhances the removal of olefins, and allows for the simultaneous replenishment of sulfuric acid and the removal of waste liquid, further improving the purity of the recovered chloromethane. This enables the recovered chloromethane to be directly vaporized and fed into the fluidized bed 100 for use.

[0040] In some embodiments, the sulfuric acid replenishment port 700 and the acid discharge port 800 are communicatively connected, thereby controlling the quality of the acid discharged from the acid discharge port 800 based on the quality of sulfuric acid added through the sulfuric acid replenishment port 700. It is understood that because the first sulfuric acid tower 510 reacts extensively with olefins, it dilutes the sulfuric acid concentration within the tower while generating byproducts and consuming a significant amount of sulfuric acid. Therefore, it is necessary to discharge a certain amount of waste liquid from the tower and replenish sulfuric acid to maintain the sulfuric acid concentration in the tower at a certain level. This improves the removal of olefins from the sulfuric acid tower, further enhancing the purity of the recovered chloromethane, which is beneficial for reuse in the production process.

[0041] In some embodiments, the mass of acid discharged from the acid discharge port 800 is 1.0 to 1.2 times the mass of sulfuric acid added from the sulfuric acid replenishment port 700. More preferably, the mass of acid discharged from the acid discharge port 800 is 1.0 to 1.1 times the mass of sulfuric acid added from the sulfuric acid replenishment port 700. It is understood that because a significant amount of waste liquid reacts with olefins in the first sulfuric acid tower 510, the sulfuric acid concentration in the tower is diluted while generating byproducts, and a considerable amount of sulfuric acid is consumed. Therefore, it is necessary to discharge a certain amount of waste liquid from the tower and replenish sulfuric acid to maintain the sulfuric acid concentration in the sulfuric acid tower at a certain level. This is beneficial for improving the removal of olefins in the sulfuric acid tower, further enhancing the purity of the recovered chloromethane, and facilitating its reuse in the production process.

[0042] In some embodiments, the mass of acid discharged from the acid discharge port 800 is 1.0 to 1.1 times the mass of sulfuric acid added from the sulfuric acid replenishment port 700. It is understood that because the first sulfuric acid tower 510 reacts extensively with olefins, it generates byproducts that dilute the sulfuric acid concentration within the tower and consume a significant amount of sulfuric acid. Therefore, it is necessary to discharge a certain amount of waste liquid from the tower and replenish sulfuric acid to maintain the sulfuric acid concentration at a certain level. This improves the removal of olefins from the sulfuric acid tower, further enhancing the purity of the recovered chloromethane, and facilitating its reuse in the production process.

[0043] In some embodiments, the chloromethane tower 250 is equipped with a reboiler 220 for heat exchange, so that the temperature of the gaseous chloromethane entering the acid treatment unit is 35°C to 45°C. It is understood that the reboiler 220 maintains the mixture entering the acid treatment unit at a certain temperature suitable for reaction with sulfuric acid in the sulfuric acid tower, ensuring the smooth progress of the separation process.

[0044] It is understood that the temperature range of the mixture input to the acid treatment unit is 35℃~45℃, and more preferably, the temperature of the mixture input to the acid treatment unit is 40℃. When the temperature of the input mixture is too high, it will lead to an increased risk of side reactions, and the heat and mass transfer efficiency of the reaction system is difficult to control at high temperatures, easily leading to local overheating, further increasing the risk of side reactions. On the other hand, when the temperature of the input mixture is too low, it may lead to incomplete reaction, significantly reducing the reaction rate, further prolonging the reaction time, and thus reducing the efficiency of olefin removal. Therefore, it is necessary to select a mixture with a suitable temperature to react with sulfuric acid, so as to ensure the olefin removal effect while further improving the purity of the recovered chloromethane, which is beneficial for further reaction.

[0045] In some embodiments, the acid treatment unit further includes a demister 900 for receiving chloromethane discharged from the sulfuric acid tower and removing sulfuric acid from the chloromethane. The chloromethane treated by the sulfuric acid tower carries a certain amount of droplets and foam, and may contain acidic substances such as sulfuric acid or other corrosive components. It is understood that a demister can effectively remove droplets and foam from the chloromethane, reducing impurities, further improving the purity of the recovered gas, reducing the generation of side reactions, and thus improving the efficiency and selectivity of subsequent reactions. On the one hand, because the demister removes impurities containing corrosive components, it can reduce corrosion of downstream equipment, further extending the service life of downstream equipment and reducing maintenance costs. On the other hand, the demister can prevent liquid from accumulating in pipelines and equipment, reducing safety risks caused by liquid accumulation, such as blockages and explosions, and improving the safety of the production process.

[0046] In some embodiments, a third condenser 330 is connected to the top of the chloromethane tower 250. The condensate from the third condenser 330 is returned to the chloromethane tower 250, and the tail gas enters the tail gas treatment system. The third condenser 330 further increases the recovery efficiency and rate of chloromethane, thereby improving economic benefits.

[0047] In some embodiments, a reflux device 230 is provided between the third condenser 330 and the chloromethane tower 250, adapted to receive the condensate obtained by the third condenser 330 and then transport it to the chloromethane tower 250. The reflux device 230 further improves the recovery efficiency of chloromethane.

[0048] In some embodiments, the chloromethane in the recovery device enters the chloromethane vaporizer before entering the fluidized bed 100 to participate in the reaction. It is understood that the chloromethane recovered to the recovery unit is generally in liquid form, but gaseous chloromethane is used in the fluidized bed 100 for organosilicon monomer synthesis. Therefore, before reusing the recovered chloromethane, it needs to be passed through the chloromethane vaporizer to convert the liquid chloromethane into gaseous chloromethane before entering the fluidized bed 100 to participate in the reaction.

[0049] Example 1

[0050] A chloromethane purification system includes a first sulfuric acid tower and a second sulfuric acid tower connected in series, wherein the sulfuric acid concentration in the first sulfuric acid tower is 40 wt.% and the sulfuric acid concentration in the second sulfuric acid tower is 90 wt.%.

[0051] Example 2

[0052] A chloromethane purification system includes a first sulfuric acid tower and a second sulfuric acid tower connected in series, wherein the sulfuric acid concentration in the first sulfuric acid tower is 30 wt.% and the sulfuric acid concentration in the second sulfuric acid tower is 90 wt.%.

[0053] Example 3

[0054] A chloromethane purification system includes a first sulfuric acid tower and a second sulfuric acid tower connected in series, wherein the sulfuric acid concentration in the first sulfuric acid tower is 40 wt.% and the sulfuric acid concentration in the second sulfuric acid tower is 80 wt.%.

[0055] Example 4

[0056] A chloromethane purification system includes a first sulfuric acid tower and a second sulfuric acid tower connected in series, wherein the sulfuric acid concentration in the first sulfuric acid tower is 60 wt.% and the sulfuric acid concentration in the second sulfuric acid tower is 80 wt.%.

[0057] Example 5

[0058] A chloromethane purification system includes a first sulfuric acid tower and a second sulfuric acid tower connected in series, wherein the sulfuric acid concentration in the first sulfuric acid tower is 30 wt.% and the sulfuric acid concentration in the second sulfuric acid tower is 95 wt.%.

[0059] Performance testing

[0060] The olefin content of the chloromethane obtained after processing by the chloromethane recovery system in Examples 1-5 was determined, and the test results are shown in Table 1.

[0061] Table 1: Olefin Content Test of Recovered Chloromethane

[0062]

[0063] As can be understood from Examples 1-5, increasing the sulfuric acid concentration in the first sulfuric acid tower improves the removal efficiency of propylene, while increasing the sulfuric acid concentration in the second sulfuric acid tower further enhances the removal efficiency of ethylene and butene. It is worth noting that increasing the sulfuric acid concentration may increase production costs while simultaneously reducing the risk of explosions and equipment damage during production. Therefore, selecting an appropriate sulfuric acid concentration not only improves the purity of recovered chloromethane but also increases operational safety and further reduces production costs.

[0064] The basic principles, main features, and advantages of this application have been described above. Those skilled in the art should understand that this application is not limited to the above embodiments. The embodiments and descriptions in the specification are merely the principles of this application. Various changes and modifications can be made to this application without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claims. The scope of protection claimed by this application is defined by the appended claims and their equivalents.

Claims

1. A purification system for chloromethane, for treating gas phase chloromethane recovered in a methylchlorosilane monomer process, characterized in that, The application relates to a chloromethane recovery system. The system comprises: a chloromethane tower, into which pressurized gaseous chloromethane is fed for recovery; an acid treatment unit comprising at least one sulfuric acid tower, into which the gaseous chloromethane from the chloromethane tower is fed, and into which the olefins entrained in the gaseous chloromethane are absorbed; 2. The purification system of chloromethane as claimed in claim 1, wherein, a first condensing device, into which the gaseous chloromethane from the acid treatment unit is fed for condensation and recovery.

3. The purification system of chloromethane as claimed in claim 1, wherein, The system further comprises a second condensing device, which is connected to the chloromethane tower and is used to condense and recover the chloromethane in the chloromethane tower when the acid treatment unit is disabled or fails.

4. The purification system of claim 3, wherein, The acid treatment unit comprises a first sulfuric acid tower and a second sulfuric acid tower connected in series, the concentration of sulfuric acid in the first sulfuric acid tower is lower than that in the second sulfuric acid tower, and the gaseous chloromethane from the chloromethane tower is fed into the first sulfuric acid tower first and then into the second sulfuric acid tower.

5. The purification system of claim 4, wherein, The first sulfuric acid tower is provided with an acid outlet, the second sulfuric acid tower is provided with a sulfuric acid supplement inlet, the sulfuric acid supplement inlet is used to input sulfuric acid into the sulfuric acid tower, the acid outlet is used to discharge the acid liquid in the sulfuric acid tower, and the second sulfuric acid tower is connected to the first sulfuric acid tower so that the sulfuric acid in the second sulfuric acid tower can be supplemented into the first sulfuric acid tower.

6. The purification system of claim 4, wherein, The first sulfuric acid tower is provided with a first acidity detection device, a first switch valve is arranged on the connecting pipeline between the second sulfuric acid tower and the first sulfuric acid tower, and the first acidity detection device is in communication connection with the first switch valve, so that when the concentration of sulfuric acid in the first sulfuric acid tower is lower than a preset value, the first switch valve is opened.

7. The purification system of claim 1, wherein, The second sulfuric acid tower is provided with a second acidity detection device, and the second acidity detection device is in communication connection with the switch valve of the sulfuric acid supplement inlet, so that when the concentration of sulfuric acid in the second sulfuric acid tower is lower than a preset value, the switch valve of the sulfuric acid supplement inlet is opened.

8. The purification system of claim 1, wherein, The chloromethane tower is provided with a reboiler for heat exchange, so that the temperature of the gaseous chloromethane fed into the acid treatment unit is 35-45 DEG C.

9. The purification system of claim 1, wherein, The acid treatment unit further comprises a defoaming device for receiving the chloromethane discharged from the sulfuric acid tower and removing the sulfuric acid in the chloromethane. The top of the chloromethane tower is connected to a third condensing device, the condensed liquid of the third condensing device is returned to the chloromethane tower, and the tail gas enters a tail gas treatment system.

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