VOC Condensation Recovery Method

Abstract

The present invention provides a method for condensing and recovering VOC. The method for condensing and recovering VOC includes the steps of: sequentially performing primary precooling treatment, secondary condensation treatment, and tertiary final cooling treatment on the VOC gas stream, and finally generating a clean gas stream; after the VOC gas stream undergoes the primary precooling treatment, a first split is performed to divide it into two or more sub-gas streams, which respectively and sequentially undergo the secondary condensation treatment and the tertiary final cooling treatment; in the tertiary final cooling treatment, a refrigerant is used as the cold source, and after passing through the tertiary final cooling treatment, the cold source forms a secondary cold source and is used as the refrigerant for the primary precooling treatment; the clean gas stream is used as the refrigerant for the secondary condensation treatment. The cold source can be used multiple times, and the cold energy of the clean gas stream can also be utilized, so that the cold energy is fully utilized and energy is saved; the temperature of the VOC gas stream gradually decreases, reducing the frosting phenomenon caused by too rapid a temperature decrease, and enabling harmful substances to be more comprehensively condensed to form a solvent, with good treatment effects.

Description

[0001] This application is a divisional application. The application number of the original application is: "202211295327.7", the application date is: "October 21, 2022", and the invention title is: "VOC Condensation Recovery System and Corresponding VOC Condensation Recovery Method". Technical Field

[0002] The present invention relates to the field of volatile gas treatment, and particularly relates to a VOC condensation recovery method. Background Art

[0003] VOC is the English abbreviation of volatile organic compounds. In the general sense, VOC refers to volatile organic compounds; but in the environmental protection sense, it refers to the active type of volatile organic compounds, that is, the type of volatile organic compounds that will cause harm. Therefore, VOC needs to be purified before being discharged.

[0004] In the prior art, when purifying VOC, a cold source is used to condense and collect harmful substances in the VOC. When the cold source is used for heat exchange with the VOC gas stream, since the temperature of the VOC gas stream drops too fast, frosting is likely to occur, thereby reducing the treatment speed and even causing blockage, affecting the purification treatment of VOC; at the same time, the cold source is discharged after being used once, resulting in insufficient utilization of cold energy and waste. Summary of the Invention

[0005] The present invention provides a VOC condensation recovery method, which can improve the treatment effect and make full use of cold energy.

[0006] The present invention provides a VOC condensation recovery method for condensing and recovering a VOC gas stream, including the following steps:

[0007] The VOC gas stream is successively subjected to primary precooling treatment, secondary condensation treatment, and tertiary final cooling treatment, and finally a clean gas stream is generated; after the VOC gas stream undergoes the primary precooling treatment, it is first split into two or more sub-gas streams, which are respectively successively subjected to the secondary condensation treatment and the tertiary final cooling treatment; solvents are generated during the primary precooling treatment, secondary condensation treatment, and tertiary final cooling treatment of the VOC gas stream.

[0008] In the tertiary final cooling treatment, the refrigerant is a cold source, and the cold source forms a secondary cold source after the tertiary final cooling treatment, and the secondary cold source is used as the refrigerant for the primary precooling treatment; the clean gas stream is used as the refrigerant for the secondary condensation treatment.

[0009] Wherein, in the step that solvents are generated during the primary precooling treatment, secondary condensation treatment, and tertiary final cooling treatment of the VOC gas stream, the solvents are collected in a solvent storage tank.

[0010] Among them, the VOC condensation recovery method further includes a defrosting treatment step; when frosting occurs during the purification treatment of one of the sub-airflows, the defrosting treatment step is executed; the defrosting treatment step includes: closing the discharge channel of this sub-airflow, interrupting the cold source supply in the three-stage final cooling treatment of this sub-airflow, and performing a second split on the other sub-airflow to split out a defrosting air flow, and the defrosting air flow flows reversely along the purification route of this sub-airflow for defrosting treatment.

[0011] Among them, the defrosting treatment step further includes: directly discharging the secondary cold source formed after the three-stage final cooling treatment, and interrupting the refrigerant supply of the first-stage pre-cooling treatment.

[0012] Among them, the defrosting treatment step further includes: heating the VOC air flow before the first split.

[0013] Among them, the defrosting treatment step further includes:

[0014] When the frosting phenomenon is eliminated, close the split channel between the VOC air flow and the other sub-airflow to stop supplying the defrosting air flow;

[0015] Restore the cold source supply in the three-stage final cooling treatment of the sub-airflow where the frost is eliminated, and the sub-airflow where the frost is eliminated flows along the purification route for purification treatment. The purified clean air flow enters the purification route of the other sub-airflow along the reverse route of the defrosting air flow;

[0016] After running for a preset duration, open the discharge channel of the sub-airflow where the frost is eliminated, and close the channel through which the defrosting air flow reversely enters the secondary condensation treatment;

[0017] Restore the split channel between the VOC air flow and the other sub-airflow.

[0018] In the VOC condensation recovery method provided by the present invention, the cold source connected to the cold source inlet can be used multiple times, and the cold energy of the purified clean air flow can also be utilized in the condensation device, so that the cold energy is fully utilized and energy is saved; the VOC air flow sequentially passes through the condensation air flow channel, the final cooling air flow channel, and the condensation cold air channel, and the temperature gradually decreases, reducing the frosting phenomenon caused by too rapid temperature decrease, and enabling harmful substances to be more comprehensively condensed into solvents, with good treatment effects. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following briefly introduces the drawings required to be used in the embodiments. The drawings in the following description are only the corresponding drawings of some embodiments of the present invention.

[0020] Figure 1 Schematic diagram of the VOC condensation recovery system provided by the first embodiment of the present invention;

[0021] Figure 2 Schematic diagram of the VOC condensation recovery system provided by the second embodiment of the present invention;

[0022] Figure 3 is Figure 2 Schematic diagram of the VOC condensation recovery system during defrosting treatment in

[0023] Figure 4 is Figure 2 Schematic diagram of the VOC condensation recovery system when it returns to normal processing after eliminating defrosting. Detailed implementation manners

[0024] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative efforts shall fall within the protection scope of the present invention.

[0025] In the present invention, unless otherwise clearly defined and limited, the terms "installation", "connection", "connection", "fixation" and other terms should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or integrated; it can be a mechanical connection or an electrical connection; it can be directly connected, or indirectly connected through an intermediate medium, and it can be the communication inside two components or the interaction relationship between two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0026] Please refer to Figure 1 , the first embodiment of the present invention provides a VOC condensation recovery system for condensing and recovering VOC gas flow, including a precooling device 10, a condensation device 20, a final cooling device 30, a cold source inlet 41, a gas flow inlet 51, a gas flow discharge port 52, a cold source discharge port 42, and a solvent storage tank 60. The cold source inlet 41 is used to connect the cold source for condensing the VOC gas flow, the gas flow inlet 51 is used to connect the VOC gas flow. After the VOC gas flow passes through the precooling device 10, the condensation device 20, and the final cooling device 30, a solvent and a clean gas flow are formed. The solvent enters the solvent storage tank 60, and the clean gas flow is discharged through the gas flow discharge port 52. After the cold source is used, it is discharged through the cold source discharge port 42.

[0027] A blower 53 for accelerating the outflow of the gas flow is provided at the gas flow discharge port 52 to increase the gas flow velocity.

[0028] The pre-cooling device 10 is provided with a pre-cooling air flow channel 101 and a pre-cooling cold source channel 102 for heat exchange. The air flows inside the pre-cooling air flow channel 101 and the pre-cooling cold source channel 102 can undergo heat exchange in the pre-cooling device 10. The condensation device 20 is provided with a condensation air flow channel 201 and a condensation cold air channel 202 for heat exchange. The air flows inside the condensation air flow channel 201 and the condensation cold air channel 202 can undergo heat exchange in the condensation device 20. The final cooling device 30 is provided with a final cooling air flow channel 301 and a final cooling cold source channel 302 for heat exchange.

[0029] The air flow inlet 51 is used to access the VOC air flow, and the air flow outlet 52 is used to discharge the clean air flow generated after the purification of the VOC air flow. The air flow inlet 51, the pre-cooling air flow channel 101, the condensation air flow channel 201, the final cooling air flow channel 301, the condensation cold air channel 202, and the air flow outlet 52 are connected in series in sequence; the cold source inlet 41 can be connected to the cold source device 40 to access the cold source, and the cold source outlet 42 is used to discharge the cold source after heat exchange treatment. The cold source inlet 41, the final cooling cold source channel 302, the pre-cooling cold source channel 102, and the cold source outlet 42 are connected in series in sequence.

[0030] The VOC air flow is cooled and condensed by passing through the pre-cooling air flow channel 101, the condensation air flow channel 201, and the final cooling air flow channel 301 in sequence. Among them, the cold source accessed by the cold source inlet 41 undergoes heat exchange with the VOC air flow in the final cooling air flow channel 301 in the final cooling cold source channel 302. Since the cold source accessed by the cold source inlet 41 is in the lowest temperature state in the final cooling cold source channel 302, the temperature of the VOC air flow in the final cooling air flow channel 301 can be reduced to the lowest, so that the harmful substances in the VOC air flow are fully condensed to form a solvent, and a clean air flow is formed. This clean air flow has a lower temperature and enters the condensation cold air channel 202, serving as a refrigerant to cool the VOC air flow in the condensation air flow channel 201, which can fully utilize the cold energy, and then is discharged through the air flow outlet 52 to save energy.

[0031] The cold source accessed by the cold source inlet 41 can enter the pre-cooling cold source channel 102 after heat exchange in the final cooling cold source channel 302 to preliminarily cool the VOC air flow in the pre-cooling air flow channel 101, so that the cold source accessed by the cold source inlet 41 can be fully utilized in the pre-cooling device 10 before being discharged to save energy.

[0032] When the VOC gas stream, which has been preliminarily cooled by the pre-cooling device 10, passes through the condensation gas stream channel 201 of the condensation device 20, it can exchange heat with the cleaner gas stream at a lower temperature in the condensation cold gas channel 202. The temperature of the VOC gas stream is reduced again, and some harmful substances are condensed to form a solvent. Finally, the VOC gas stream exchanges heat with the cold source at the lowest temperature in the final cooling gas stream channel 301, the temperature is reduced to the lowest, and the remaining harmful substances are all condensed to form a solvent, and a clean gas stream is discharged.

[0033] The cold source in the condensation device 20 can be used multiple times, and the cold energy of the cleaner gas stream at a lower temperature can also be utilized in the condensation device 20, so that the cold energy of the condensation device 20 is fully utilized and energy is saved. The VOC gas stream passes through the condensation gas stream channel 201, the final cooling gas stream channel 301, and the condensation cold gas channel 202 in sequence, and the temperature gradually decreases, enabling harmful substances to be more comprehensively condensed to form a solvent, and the treatment effect is good.

[0034] The condensation gas stream channel 201, the final cooling gas stream channel 301, and the condensation cold gas channel 202 are all connected to the solvent storage tank 60 to guide the solvent formed after the condensation of the VOC gas stream to the solvent storage tank 60. The formed solvent can be collected and then processed through the solvent storage tank 60.

[0035] A stop valve is provided at the gas stream input port 51. The stop valve can be used to control the opening and access or suspension of access of the VOC gas stream. The stop valve is preferably a pneumatic stop valve. One or more of a flame arrester, a temperature sensor, and a pressure sensor are provided on the pipeline from the pre-cooling gas stream channel 101 to the gas stream input port 51. The flame arrester can prevent fires, and the temperature sensor and the pressure sensor can detect the temperature and pressure of the input VOC gas stream in real time.

[0036] Corresponding to the first embodiment of the VOC condensation recovery system, the present invention also provides a VOC condensation recovery method, including the following steps.

[0037] The VOC gas stream is subjected to primary pre-cooling treatment, secondary condensation treatment, and tertiary final cooling treatment in sequence, and finally a clean gas stream is generated. Solvents are generated and collected during the primary pre-cooling treatment, secondary condensation treatment, and tertiary final cooling treatment of the VOC gas stream. The primary pre-cooling treatment is carried out in the pre-cooling device 10, the secondary condensation treatment is carried out in the condensation device 20, and the tertiary final cooling treatment is carried out in the final cooling device 30. The solvent is collected in the solvent storage tank 60.

[0038] In the tertiary final cooling treatment, the refrigerant is a cold source, and this cold source is directly led out from the cold source access port 41. The cold source access port 41 is connected to the cold source device 40, the cold source is liquid nitrogen, and the cold source device 40 can be a liquid nitrogen tank.

[0039] After the cold source undergoes three - stage final cooling treatment, a secondary cold source is formed. The secondary cold source serves as the refrigerant for the first - stage pre - cooling treatment; the clean air stream serves as the refrigerant for the second - stage condensation treatment.

[0040] In the final cooling device 30, the cold source is located in the final - cooling cold - source pipeline. After heat exchange, a secondary cold source is formed and guided to the pre - cooling cold - source channel in the pre - cooling device as the refrigerant for the first - stage pre - cooling treatment, enabling the secondary utilization of the cold source and improving the cold - energy utilization rate.

[0041] After the VOC air stream undergoes the first - stage pre - cooling treatment in the pre - cooling terminal, its temperature drops by one level. Then it enters the condensation device 20 for the second - stage condensation treatment, and the temperature drops again. Finally, it undergoes the third - stage final cooling treatment in the final cooling device 30, reducing the temperature of the VOC air stream to the lowest level, enabling harmful substances to fully condense to form solvents, and generating a clean air stream. The gradually decreasing temperature of the VOC air stream can reduce frosting caused by rapid cooling. The clean air stream serves as the refrigerant for the second - stage condensation treatment, which can fully utilize the cold energy of the clean air stream and improve the cold - energy utilization rate.

[0042] After the VOC air stream undergoes the first - stage pre - cooling treatment, it can be divided into multiple sub - air streams to sequentially undergo the second - stage condensation treatment and the third - stage final cooling treatment. That is, the condensation device and the final cooling device can be more than two, and the two are connected in one - to - one correspondence. A condensation subsystem formed by a set of condensation device and final cooling device corresponds to one sub - air stream to improve the condensation effect.

[0043] The pre - cooling device 10, the condensation device 20, and the final cooling device 30 can use the same heat exchanger for easy maintenance. A buffer device (not shown in the figure) can be provided between the bottom of the heat exchanger and the solvent storage tank. Taking the pre - cooling device as an example to illustrate the buffer device, the buffer device includes a buffer three - way valve, a buffer pipe, and a check valve. The pre - cooling air - flow channel, the buffer three - way valve, the buffer pipe, the check valve, and the solvent storage tank are connected in sequence. The three interfaces of the buffer three - way valve are respectively connected to the air - flow input port, the pre - cooling air - flow pipe, and one end of the buffer pipe. The check valve is connected between the other end of the buffer pipe and the solvent storage tank.

[0044] The buffer three - way valve has a buffer state and a recovery state: when the buffer three - way valve is in the buffer state, the air - flow input port, the pre - cooling air - flow pipe, and the buffer pipe are connected, the check valve is in the closed state, and the buffer pipe is used to buffer the solvent flowing out of the pre - cooling air - flow pipe; when the buffer three - way valve is in the recovery state, the connection between the buffer three - way valve and the buffer pipe is closed, the check valve is in the open state, so that the solvent in the buffer pipe flows into the solvent storage tank. Through the cooperation of the buffer three - way valve and the check valve, when the buffer pipe is full of solvent, the solvent is then guided to the solvent storage tank, enabling the self - flowing recovery of the condensed solvent and preventing the VOC air stream from entering the solvent storage tank.

[0045] The bottom of the condensation device 20 and the final cooling device 30 are both provided with the above-mentioned buffer devices, and their structures are the same as those described above, so they will not be elaborated here.

[0046] Please refer to Figure 2 , a second embodiment of the present invention provides a VOC condensation recovery system for condensing and recovering VOC gas flow, including a precooling device 10, a cold source inlet 41, a gas flow inlet 51, a gas flow outlet 52, a cold source outlet 42, and a solvent storage tank 60. The cold source inlet 41 is used to access the cold source for condensing the VOC gas flow, the gas flow inlet 51 is used to access the VOC gas flow. The VOC gas flow forms a solvent and a clean gas flow after passing through the precooling device 10 and the condensation subsystem. The solvent enters the solvent storage tank 60, and the clean gas flow is discharged through the gas flow outlet 52. After the cold source is used, it is discharged through the cold source outlet 42. A blower for accelerating the outflow of the gas flow is provided at the gas flow outlet 52 to increase the gas flow velocity.

[0047] The precooling device 10 is provided with a precooling gas flow channel 101 and a precooling cold source channel 102 for heat exchange. The gas flows inside the precooling gas flow channel 101 and the precooling cold source channel 102 can exchange heat in the precooling device 10.

[0048] A condensation device and a final cooling device are connected to form a condensation subsystem, and there are two condensation subsystems. For the convenience of description, the two condensation subsystems are respectively the first condensation subsystem 91 and the second condensation subsystem 92. The condensation device and the final cooling device in the first condensation subsystem 91 are respectively the first condensation device 21 and the first final cooling device 31. The condensation device and the final cooling device in the second condensation subsystem 92 are respectively the second condensation device 22 and the second final cooling device 32.

[0049] The first condensation device 21 is provided with a first condensation gas flow channel 211 and a first condensation cold air channel 212 for heat exchange. The first final cooling device 31 is provided with a first final cooling gas flow channel 311 and a first final cooling cold source channel 312 for heat exchange. The first condensation gas flow channel 211, the first final cooling gas flow channel 311, and the first condensation cold air channel 212 are connected in sequence.

[0050] The second condensation device 22 is provided with a second condensation gas flow channel 221 and a second condensation cold air channel 222 for heat exchange. The second final cooling device 32 is provided with a second final cooling gas flow channel 321 and a second final cooling cold source channel 322 for heat exchange. The second condensation gas flow channel 221, the second final cooling gas flow channel 321, and the second condensation cold air channel 222 are connected in sequence.

[0051] The input end of the pre-cooling air flow channel 101 is connected to the air flow input port 51. One end of the first condensing air flow channel 211, which is far from the first final cooling air flow channel 311, and one end of the second condensing air flow channel 221, which is far from the second final cooling air flow channel 321, are both connected to the output end of the pre-cooling air flow channel 101.

[0052] The input ends of both the first final cooling heat source channel 312 and the second final cooling heat source channel 322 are connected to the heat source access port 41, and the output ends are both connected to the input end of the pre-cooling heat source channel 102. The output end of the pre-cooling heat source channel 102 is connected to the heat source discharge port 42.

[0053] The VOC air flow first passes through the pre-cooling air flow channel 101, and then is divided into two sub-air flows, the first sub-air flow and the second sub-air flow, which respectively enter the first condensing air flow channel 211 and the second condensing air flow channel 221. The output heat source accessed by the heat source access port 41 is divided into two parts, which respectively enter the first final cooling heat source channel 312 and the second final cooling heat source channel 322.

[0054] The first sub-air flow after passing through the first condensing air flow channel 211 enters the first final cooling air flow channel 311, and exchanges heat with the heat source in the first final cooling heat source channel 312 in the first final cooling air flow channel 311. The heat source input into the first final cooling heat source channel 312 is the heat source directly accessed from the heat source access port 41, and its temperature is in the lowest state. Therefore, in the first final cooling device 31, the temperature of the VOC air flow can be reduced to the lowest state, so that the harmful substances in the VOC air flow can be fully condensed to form a solvent in the first final cooling air flow channel 311 of the first final cooling device 31, and a first clean air flow is formed. The temperature of this clean air flow is relatively low. It is guided to the first condensing cold air channel 212 to cool the VOC air flow in the first condensing air flow channel 211 as a refrigerant, which can make full use of the cold energy, and then is discharged through the air flow discharge port 52 to save energy.

[0055] The condensation process of the second sub-air flow entering the second condensing air flow channel 221 is carried out in the second condensing subsystem, which is similar to the condensation process of the first sub-air flow. The second sub-air flow enters the second final cooling air flow channel 321 through the second condensing air flow channel 221, and exchanges heat with another heat source in the second final cooling heat source channel 322 in the second final cooling device 32 to generate a solvent and a second clean air flow. The second clean air flow enters the second condensing cold air channel 222 to cool the second sub-air flow in the second condensing air flow channel 221.

[0056] After the two cold sources pass through the first final cold source channel 312 and the second final cold source channel 322 respectively for heat exchange, they converge and then enter the pre-cooling cold source channel 102 to preliminarily cool the VOC gas flow in the pre-cooling gas flow channel 101. This can enable the cold source connected to the cold source access port 41 to be fully utilized in the pre-cooling device 10 and then discharged, so as to save energy.

[0057] In the first condensation subsystem 91 and the second condensation subsystem 92, the VOC gas flow may frost in the pipelines of the two subsystems due to too low temperature, which will affect the passing speed of the VOC gas flow, and will also cause the VOC gas flow to not fully conduct heat exchange to form a solvent. The VOC gas flow cannot be fully condensed and recovered, resulting in environmental pollution. Therefore, it is necessary to deal with the frosting problem. The following is the solution in this embodiment.

[0058] The output port of the pre-cooling gas flow channel 101 is connected to the main gas flow pipe 110. The input port of the first condensation gas flow channel 211 is connected to the first sub-gas flow pipe 111, and the input port of the second condensation gas flow channel 221 is connected to the second sub-gas flow pipe 112. The first sub-gas flow pipe 111 and the second sub-gas flow pipe 112 are arranged in parallel and are both connected to the main gas flow pipe 110. The first sub-gas flow pipe 111, the second sub-gas flow pipe 112, and the main gas flow pipe 110 can be connected through a shunt three-way valve 113. The shunt three-way valve 113 can be used to control the on-off between the three pipelines. Here, the three pipelines can also be connected through a three-way valve.

[0059] A first defrosting three-way valve 71 is provided on the pipeline between the first condensation cold air channel 212 and the air flow discharge port 52. The three interfaces of the first defrosting three-way valve 71 are respectively connected to the first condensation cold air channel 212, the air flow discharge port 52, and the second sub-gas flow pipe 112 of the second condensation subsystem 92. More specifically, the first defrosting three-way valve 71 can be connected to the second sub-gas flow pipe 112 through a first defrosting pipe. A three-way pipe is provided in the middle of the second sub-gas flow pipe 112, and this three-way pipe is connected to the first defrosting pipe.

[0060] The first defrosting three-way valve 71 has a normal state and a defrosting state.

[0061] As Figure 2 shown, when the first defrosting three-way valve 71 is in the normal state, the pipeline between the first condensation cold air channel 212 and the air flow discharge port 52 is connected through the first defrosting three-way valve 71, and the connection between the first defrosting three-way valve 71 and the second sub-gas flow pipe 112 of the second condensation subsystem 92 is closed. At this time, the air flow flowing out of the first condensation cold air channel 212 can be discharged through the air flow discharge port 52.

[0062] As Figure 3As shown, when the first defrosting three-way valve 71 is in the defrosting state, the first condensate cold air channel 212 is connected to the second sub-airflow pipe 112 of the second condensation subsystem 92 through the first defrosting three-way valve 71, and the connection between the first defrosting three-way valve 71 and the air discharge port 52 is closed. At this time, the airflows from the first condensate cold air channel 212 and the second sub-airflow pipe 112 will not be discharged through the air discharge port 52, and the VOC airflow can circulate between the first condensate cold air channel 212 and the second sub-airflow pipe 112.

[0063] A second defrosting three-way valve 72 is provided on the pipeline between the second condensate cold air channel 222 and the air discharge port 52. The three interfaces of the second defrosting three-way valve 72 are respectively connected to the second condensate cold air channel 222, the air discharge port 52, and the first sub-airflow pipe 111 of the first condensation subsystem 91. More specifically, the second defrosting three-way valve 72 can be connected to the first sub-airflow pipe 111 through the second defrosting pipe. A three-way pipe is provided in the middle of the first sub-airflow pipe 111, and this three-way pipe is connected to the second defrosting pipe.

[0064] The second defrosting three-way valve 72 has a normal state and a defrosting state. When the second defrosting three-way valve 72 is in the normal state, the pipeline between the second condensate cold air channel 222 and the air discharge port 52 is connected through the second defrosting three-way valve 72, and the connection between the second defrosting three-way valve 72 and the first sub-airflow pipe 111 of the first condensation subsystem 91 is closed. At this time, the airflow flowing out of the second condensate cold air channel 222 can be discharged through the air discharge port 52. When the second defrosting three-way valve 72 is in the defrosting state, the second condensate cold air channel 222 is connected to the first sub-airflow pipe 111 of the first condensation subsystem 91 through the first defrosting three-way valve 71, and the connection between the second defrosting three-way valve 72 and the air discharge port 52 is closed. At this time, the airflows from the second condensate cold air channel 222 and the first sub-airflow pipe 111 will not be discharged through the air discharge port 52, and the VOC airflow can circulate between the second condensate cold air channel 222 and the first sub-airflow pipe 111.

[0065] A first cold source valve 411 is provided between the first final cold source channel 312 and the cold source access port 41. The first cold source valve 411 is used to control the connection and disconnection between the first final cold source channel 312 and the cold source access port 41. The first cold source valve 411 has a connected state and a closed state: As Figure 2 shown, when the first cold source valve 411 is in the connected state, the first final cold source channel 312 is connected to the cold source access port 41 through the first cold source valve 411. At this time, after the cold source access port 41 is connected to the cold source device 40, it can provide a cold source to the first final cold source channel 312; As Figure 3As shown, when the first cold source valve 411 is in the closed state, the first final cold source channel 312 is closed from the cold source access port 41 via the first cold source valve 411. At this time, the cold source access port 41 stops providing cold source to the first final cold source channel 312.

[0066] A second cold source valve 412 is provided between the second final cold source channel 322 and the cold source access port 41. The second cold source valve 412 is used to control the on-off between the second final cold source channel 322 and the cold source access port 41. The second cold source valve 412 has a connected state and a closed state: when the second cold source valve 412 is in the connected state, the second final cold source channel 322 is connected to the cold source access port 41 via the second cold source valve 412. At this time, the cold source access port 41 can provide cold source to the second final cold source channel 322; when the second cold source valve 412 is in the closed state, the second final cold source channel 322 is closed from the cold source access port 41 via the second cold source valve 412. At this time, the cold source access port 41 stops providing cold source to the second final cold source channel 322.

[0067] As Figure 2 shown, when the first condensation subsystem 91 is operating normally, the first cold source valve 411 is in the connected state and the first defrosting three-way valve 71 is in the normal state. When the second condensation subsystem 92 is operating normally, the second cold source valve 412 is in the connected state and the second defrosting three-way valve 72 is in the normal state.

[0068] When frosting occurs in the first condensation subsystem 91, as Figure 3 shown, the first cold source valve 411 is in the closed state and the first defrosting three-way valve 71 is in the defrosting state. At this time, the first final cold source channel 312 is closed from the cold source access port 41 via the first cold source valve 411, so that the cold source access port 41 no longer provides cold source to the first final cold source channel 312, and the condensation process of the first condensation subsystem 91 stops; the first condensation cold air channel 212 is in the closed state between the air flow discharge port 52 via the first defrosting three-way valve 71, so that the first stream of clean air cannot be discharged through the first defrosting three-way valve 71 and the air flow discharge port 52; the second sub-air flow pipe 112 of the second condensation subsystem 92 is in the connected state with the first condensation cold air channel 212 via the first defrosting three-way valve 71, so that the VOC air flow can enter the first condensation cold air channel 212, the first final cold air channel 311, and the first condensation air channel 211 in sequence through the second sub-air flow pipe 112 of the second condensation subsystem 92 for defrosting.

[0069] By using the first defrost three-way valve 71, the VOC gas flow that has not been condensed by the two condensation subsystems and is still at a relatively high temperature can flow reversely along the purification route in the first condensation subsystem 91, successively passing through the first condensation cold air channel 212, the first final cooling gas flow channel 311, and the first condensation gas flow channel 211 in the first condensation subsystem 91, so as to use the relatively high-temperature VOC gas flow for defrosting operations; the VOC gas flow for defrosting flows out from the first condensation gas flow channel 211 and enters the second condensation subsystem 92 through the first sub-gas flow pipe 111 and the second sub-gas flow pipe 112. At this time, the second condensation subsystem 92 is in a normal working state, and the VCO gas flow for defrosting can be processed in the second condensation subsystem 92 to form a clean gas flow and then discharged. When frosting occurs in the first condensation subsystem 91, the first cold source valve 411, the first defrost three-way valve 71, and the second condensation subsystem 92 can ensure the continuous treatment of the VOC gas flow.

[0070] When frosting occurs in the second condensation subsystem 92, the second cold source valve 412 is in the closed state, and the second defrost three-way valve 72 is in the defrost state. At this time, defrosting operations can be carried out on the second condensation subsystem 92, and the VOC gas flow can continue to be processed through the first condensation subsystem 91. Its defrosting process is similar to that of the first condensation subsystem 91 and will not be elaborated here.

[0071] In order to further improve the defrosting effect: the output ports of both the first final cooling cold source channel 312 and the second final cooling cold source channel 322 are connected to the pre-cooling cold source delivery pipe 33. A pre-cooling three-way valve 43 is provided between the pre-cooling cold source delivery pipe 33 and the input port of the pre-cooling cold source channel 102. The two cold source gas flows that have undergone superheat exchange in the first final cooling cold source channel 312 and the second final cooling cold source channel 322 converge into the pre-cooling cold source delivery pipe 33, and are transported to the pre-cooling three-way valve 43 through the pre-cooling cold source delivery pipe 33. Through the pre-cooling three-way valve 43, the cold source gas flow in the pre-cooling cold source delivery pipe 33 enters the pre-cooling cold source channel 102 or is directly discharged through the cold source discharge port 42.

[0072] The three interfaces of the pre-cooling three-way valve 43 are respectively connected to the pre-cooling cold source delivery pipe 33, the input port of the pre-cooling cold source channel 102, and the cold source discharge port 42. The pre-cooling three-way valve 43 has a pre-cooling state and a discharge state.

[0073] As Figure 2 shown, when the pre-cooling three-way valve 43 is in the pre-cooling state, the pre-cooling cold source delivery pipe 33 and the input port of the pre-cooling cold source channel 102 are connected through the pre-cooling three-way valve 43, and the connection between the pre-cooling three-way valve 43 and the cold source discharge port 42 is closed. At this time, the cold source gas flow in the pre-cooling cold source delivery pipe 33 enters the pre-cooling cold source channel 102 to pre-cool the VOC gas flow and will not be discharged outside through the cold source discharge port 42.

[0074] AsFigure 3 As shown, when the precooling three-way valve 43 is in the discharge state, the precooling cold source delivery pipe 33 is communicated with the cold source discharge port 42 through the precooling three-way valve 43, and the connection between the precooling three-way valve 43 and the input port of the precooling cold source passage 102 is closed. At this time, the cold source air flow entering the precooling cold source delivery pipe 33 does not pass through the precooling cold source passage 102, but is directly discharged through the cold source discharge port 42.

[0075] When both the first condensation subsystem 91 and the second condensation subsystem 92 are operating normally, the precooling three-way valve 43 is in the precooling state to make secondary use of the cold energy of the cold source. When frosting occurs in any one of the first condensation subsystem 91 and the second condensation subsystem 92, the precooling three-way valve 43 is in the discharge state, so that the cold source connected to the cold source inlet 41 is no longer used for secondary use, that is, the VOC air flow is no longer precooled by the precooling device 10. The air flow entering the main air flow pipe 110 does not pass through precooling and its temperature is relatively higher than that of the precooled air flow. By using this VOC air flow to enter the condensation subsystem where frosting occurs, the defrosting efficiency and defrosting effect can be improved.

[0076] Furthermore, the VOC condensation recovery system may further include a defrosting device 80. The defrosting device 80 is arranged on the main air flow pipe 110 and is used to heat up the VOC air flow entering each condensation subsystem. When frosting occurs in any one of the condensation subsystems, the defrosting device 80 can be turned on. The defrosting device 80 is in an operating state, and the defrosting device 80 heats the VOC air flow in the main air flow pipe 110 to increase the temperature of the VOC air flow entering the condensation subsystem, thereby further improving the defrosting efficiency and defrosting effect. Here, in other embodiments, the defrosting device 80 may also be arranged on the pipeline between the precooled air flow passage 101 and the air flow inlet 51, as long as it can heat up the VOC air flow entering each condensation subsystem.

[0077] The VOC condensation recovery system further includes a control module (not shown in the figure). At least one of the condensation cold air passage 202, the final cooling air flow passage 301, and the condensation air flow passage 201 of the same condensation subsystem is provided with a frosting sensor. That is, at least one of the first condensation cold air passage 212, the first final cooling air flow passage 311, and the first condensation air flow passage 211 is provided with a frosting sensor (not shown in the figure), and at least one of the second condensation cold air passage 222, the second final cooling air flow passage 321, and the second condensation air flow passage 221 is provided with a frosting sensor for sensing the frosting state.

[0078] The frost sensor, defrosting device 80, first defrosting three-way valve 71, second defrosting three-way valve 72, first cold source valve 411, second cold source valve 412, and pre-cooling three-way valve 43 are all electrically connected to the control module. The control module is used to receive the signal from the frost sensor and control the states of the defrosting device 80, first defrosting three-way valve 71, second defrosting three-way valve 72, first cold source valve 411, second cold source valve 412, and pre-cooling three-way valve 43, etc.

[0079] The frost sensor can be one or a combination of a temperature sensor, a flow sensor, a flow velocity sensor, and a pressure sensor. When frosting occurs in each condensation subsystem, the temperature, flow rate, and pressure of the air flow in the three pipelines of the condensation cold air channel 202, the final cold air flow channel 301, and the condensation air flow channel 201 all change. By detecting the change of the air flow through the control module, if the induction signal of the frost sensor exceeds the frosting threshold, it means that frosting occurs in the condensation subsystem, and then the states of the defrosting device 80, the defrosting three-way valve, the cold source valve, and the pre-cooling three-way valve 43 are changed.

[0080] The frosting threshold includes a first threshold and a second threshold. The frosting phenomenon is more serious in the second threshold state than in the first threshold state. If the frost sensor is a temperature sensor, the frosting threshold is a temperature value, and the first threshold is greater than the second threshold, that is, the lower the temperature, the more serious the frosting phenomenon. If the frost sensor is a flow sensor, the frosting threshold is the flow value passing through per unit time, and the first threshold is greater than the second threshold, that is, the smaller the flow passing through per unit time, the more serious the frosting phenomenon. If the frost sensor is a flow velocity sensor, the frosting threshold is the flow velocity value of the air flow, and the first threshold is greater than the second threshold, that is, the lower the flow velocity, the more serious the frosting phenomenon. If the frost sensor is a pressure sensor, the frosting threshold is the pressure value in the pipeline, and the first threshold is less than the second threshold, that is, the greater the pressure, the more serious the frosting phenomenon.

[0081] Taking the first condensation subsystem 91 as an example, when frosting occurs and the induction signal of the frost sensor exceeds the first threshold, at this time the frosting phenomenon is not very serious. The control module can control the first defrosting three-way valve 71 to be in the defrosting state, the pre-cooling three-way valve 43 to be in the discharge state, and the first cold source valve 411 to be in the closed state, so that the first condensation subsystem 91 stops condensing, and the VOC air flow that has not been pre-cooled is directly passed through the first condensation subsystem 91 in the reverse direction to perform defrosting treatment on it.

[0082] When the induction signal of the frost sensor exceeds the second threshold, at this time the frosting phenomenon is relatively serious, or, if the defrosting effect after the above defrosting treatment does not reach the expectation within a certain period of time, the control module can further control the defrosting device 80 to be in the operating state on the above basis. After heating the VOC air flow, it is passed through the second condensation subsystem 92 in the reverse direction to improve the defrosting effect.

[0083] A defrost temperature sensor may be provided on the main air flow pipe 110 to detect the heating effect of the defrost device 80 . The defrost temperature sensor may be electrically connected to a control module to control the heating power of the defrost device 80 according to a signal of the defrost temperature sensor.

[0084] Here, it can be understood that, as other implementation methods, the first threshold value and the second threshold value may not be set. When frosting occurs, the control module directly controls the first defrost three-way valve 71 to be in a defrost state, the pre-cooling three-way valve 43 to be in a discharge state, the first cold source valve 411 to be in a closed state, and the defrost device 80 to be in an operating state, so as to increase the defrost speed.

[0085] When frosting occurs in the first condensation subsystem 91, the first defrost three-way valve 71 is first controlled to be in a defrost state, and then the first cold source valve 411 is controlled to be in a closed state to prevent the unpurified VOC airflow from being discharged through the first defrost three-way valve 71 after the first cold source valve 411.

[0086] In this embodiment, the main airflow pipe 110 is connected to the first sub-airflow pipe 111 and the second sub-airflow pipe 112 via a diverting three-way valve 113. The diverting three-way valve 113 has a diverting state and a purifying state.

[0087] When the diversion three-way valve 113 is in the diversion state, the main airflow pipe 110 and the first sub-airflow pipe 111 and the second sub-airflow pipe 112 are all connected, so that the VOC airflow can be divided into two streams through the diversion three-way valve 113 and enter the first sub-airflow pipe 111 and the second sub-airflow pipe 112 respectively.

[0088] When the diverter three-way valve 113 is in the purification state, the main air flow pipe 110 is connected to the sub-air flow pipe of the condensation subsystem that has completed defrosting through the diverter three-way valve 113, and the diverter three-way valve 113 is closed to the sub-air flow pipe of the condensation subsystem where no frosting occurs.

[0089] For example, when frost occurs in the first condensation subsystem 91 and the defrosting process is completed, the internal pipelines thereof return to normal. Figure 4As shown, at this time, control the first cold source valve 411 to be in the open state, the shunt three-way valve 113 to be in the purification state, and the defrosting device 80 to be in the closed state, so that the first defrosting three-way valve 71 maintains the defrosting state. The main air flow pipe 110 is connected to the first sub-air flow pipe 111 and disconnected from the second sub-air flow pipe 112, so that the VOC air flow in the main air flow pipe 110 enters the first condensation subsystem 91 through the first sub-air flow pipe 111 for purification treatment. The treated clean air flow can enter the second condensation subsystem 92 through the first defrosting three-way valve 71, so that the VOC air flow remaining in the first condensation cold air channel for defrosting is purified in the second condensation subsystem 92. After running for a period of time, at this time, there is no untreated VOC air flow in the first condensation cold air channel, and then control the first defrosting three-way valve 71 to be in the normal state to restore the normal operation of the first condensation subsystem.

[0090] Here, it can be judged whether the defrosting operation is completed by whether the signal of the frost sensor returns to normal.

[0091] In this embodiment, the control module is used to control the state switching of components such as the precooling three-way valve, the defrosting device, the defrosting three-way valve, and the cold source valve. In other embodiments, these components can also be manually operated manually. The frost sensor can be connected to an audible and visual alarm device to prompt the operator to operate and process the above components.

[0092] In the above embodiment, the shunt three-way valve 113 is used to remove the VOC air flow remaining in the first condensation cold air channel for defrosting. Here, an air flow reversing device can also be provided between the first defrosting three-way valve and the second sub-air flow pipe, and the air flow direction between the first defrosting three-way valve and the second sub-air flow pipe is controlled to clean the VOC air flow for defrosting. For example, when removing the frost in the first condensation subsystem, control the air flow reversing device so that the air flow direction is from the second sub-air flow pipe to the first defrosting three-way valve to guide the VOC air flow for defrosting into the first condensation subsystem; when the frost is removed, switch the air flow reversing device so that the air flow direction is from the first defrosting three-way valve to the second sub-air flow pipe, so that the VOC air flow for defrosting enters the second sub-air flow pipe and is purified by the second condensation subsystem.

[0093] In the above embodiments, the number of condensation subsystems is one or two. Of course, in other embodiments, the number of condensation subsystems can also be three or more. As can be seen from the second embodiment, when there are more than two condensation subsystems, the condensation air flow channels, the final cooling air flow channels, and the condensation cold air channels within the same condensation subsystem are connected in series in sequence; all the condensation air flow channels in the condensation devices are connected to the pre-cooling air flow channel, all the condensation cold air channels in the condensation devices are connected to the pre-cooling air flow channel, and all the final cooling source channels in the final cooling devices are connected to the cold source device; the input ports of the respective condensation cold air channels are connected with sub-air flow pipes, and all the sub-air flow pipes are arranged in parallel and are all connected to the main air flow pipe; the defrosting three-way valves and the sub-air flow pipes of the condensation subsystems can be connected in sequence in a cycle, so as to convey VOC air flow to the defrosting three-way valves and their channels of the condensation subsystem where frosting occurs through the sub-air flow pipes of other condensation subsystems for defrosting treatment.

[0094] For example, when there are three condensation subsystems, that is, on the basis of the second embodiment, a third condensation subsystem is further included. One interface of the first defrosting three-way valve 71 of the first condensation subsystem 91 is connected to the second sub-air flow pipe 112 of the second condensation subsystem 92, one interface of the second defrosting three-way valve 72 of the second condensation subsystem 92 is connected to the third sub-air flow pipe of the third condensation subsystem, and one interface of the third defrosting three-way valve of the third condensation subsystem is connected to the first sub-air flow pipe 111 of the first condensation subsystem 91. In this way, when frosting occurs in the first condensation subsystem 91, the VOC air flow in the second sub-air flow pipe 112 can be used to defrost each pipeline in the first condensation subsystem 91; when frosting occurs in the second condensation subsystem 92, the VOC air flow in the third sub-air flow pipe can be used to defrost each pipeline in the second condensation subsystem 92; when frosting occurs in the third condensation subsystem, the VOC air flow in the first sub-air flow pipe 111 can be used to defrost each pipeline in the third condensation subsystem. When there are more than four condensation subsystems, it is similar to the case of three, and they can be connected in sequence in a cycle, so that when one or two condensation subsystems have frosting, effective defrosting treatment can be carried out.

[0095] Combined with the second embodiment of the VOC condensation recovery system, the present invention also provides another VOC condensation recovery method, including the following steps.

[0096] The VOC gas stream is subjected to primary precooling treatment, secondary condensation treatment, and tertiary final cooling treatment in sequence, and finally a clean gas stream is generated. Solvents are generated and collected during the primary precooling treatment, secondary condensation treatment, and tertiary final cooling treatment of the VOC gas stream. The primary precooling treatment is carried out in the precooling device 10, the secondary condensation treatment is carried out in the first and second condensation devices, and the tertiary final cooling treatment is carried out in the first and second final cooling devices. The solvent is recovered into the solvent storage tank 60. The temperature of the VOC gas stream gradually decreases, which can reduce frosting caused by excessive rapid cooling. The clean gas stream is used as the refrigerant for the secondary condensation treatment, which can make full use of the cold energy of the clean gas stream and improve the cold energy utilization rate.

[0097] In the tertiary final cooling treatment, the refrigerant is used as the cold source, and this cold source is directly connected from the cold source inlet 41. The cold source is liquid nitrogen, and the cold source device 40 connected to the cold source inlet 41 can be a liquid nitrogen tank. After passing through the tertiary final cooling treatment, the cold source forms a secondary cold source, that is, the gas flow flowing out from the first and second final cooling source channels is the secondary cold source, and the secondary cold source is used as the refrigerant for the primary precooling treatment; the clean gas stream is used as the refrigerant for the secondary condensation treatment. In the first and second final cooling devices, the cold source is located in the first and second final cooling source pipelines. After heat exchange, a secondary cold source is formed and guided into the precooling device as the refrigerant for the primary precooling treatment, so that the cold source can be reused and the cold energy utilization rate can be improved.

[0098] In the steps of sequentially subjecting the VOC gas stream to primary precooling treatment, secondary condensation treatment, and tertiary final cooling treatment, after the VOC gas stream undergoes the primary precooling treatment, the first shunt is performed to divide it into two or more sub gas streams, which are respectively and sequentially subjected to secondary condensation treatment and tertiary final cooling treatment; that is, they enter each condensation subsystem for treatment. For example, after the VOC gas stream undergoes the primary precooling treatment, it flows out from the precooling device 10 and is divided into two sub gas streams, namely the first sub gas stream and the second sub gas stream. The first sub gas stream enters the first condensation subsystem 91, and the second sub gas stream enters the second condensation subsystem 92. During the condensation recovery process of each sub gas stream in its condensation subsystem, the route passed through in sequence is its purification route. For example, during the condensation recovery of the first sub gas stream in the first condensation subsystem 91, the purification route of the first sub gas stream is the first condensation gas flow channel 211, the first final cooling gas flow channel, and the first condensation gas flow channel 211.

[0099] The VOC condensation recovery method further includes the following defrosting treatment steps. When frosting occurs during the purification treatment of one of the sub gas streams, the defrosting treatment steps are executed to solve the frosting phenomenon.

[0100] The defrosting treatment steps include: closing the discharge channel of this sub gas stream and interrupting the supply of the cold source in the tertiary final cooling treatment of this sub gas stream, performing a second shunt on the other sub gas stream to separate a defrosting gas stream, and the defrosting gas stream flows reversely along the purification route of this sub gas stream for defrosting treatment until the frosting phenomenon is eliminated.

[0101] Combined with the second embodiment of the VOC condensation recovery system, when frosting occurs in the first sub-airflow within the first condensation subsystem 91, the discharge channel of the first sub-airflow is closed, and the discharge of the first sub-airflow is stopped, that is, the first defrosting three-way valve 71 is controlled to be in the defrosting state; the cold source supply of the first final cooling device 31 in the three-stage final cooling treatment is interrupted, that is, the first cold source valve 411 is closed, so that the cold source cannot enter the first final cooling cold source channel in the first final cooling device 31, thereby realizing the supply of the cold source in the three-stage final cooling treatment.

[0102] The second sub-airflow is secondarily split to separate a first defrosting airflow, and the first defrosting airflow flows reversely along the purification route of the first sub-airflow for defrosting treatment, that is, it sequentially passes through the first condensation airflow channel, the first final cooling airflow channel 311, and the first condensation airflow channel 211. Since the first defrosting airflow has not been purified by the second condensation subsystem 92, its temperature is still in a relatively high state, and it can raise the temperature of each pipeline of the first condensation subsystem 91, thereby achieving the purpose of defrosting.

[0103] In order to improve the defrosting effect, the secondary cold source formed after the three-stage final cooling treatment is directly discharged, and the refrigerant supply for the first-stage pre-cooling treatment is interrupted, that is, the pipeline between the first final cooling cold source channel 312 and the pre-cooling cold source channel 102 is closed, and the first final cooling cold source channel 312 is directly connected to the cold source discharge port 42, so that the secondary cold source flowing out of the first final cooling cold source channel 312 is directly discharged without secondary utilization. So that the VOC airflow skips the first-stage pre-cooling treatment and its temperature will not decrease, thereby enabling the first condensation subsystem 91 to be defrosted at a relatively high temperature.

[0104] Furthermore, when frosting occurs in the first sub-airflow, the VOC airflow before the first split is heated to make the VOC airflow reversely entering the first condensation subsystem 91 have a higher temperature, thereby accelerating the defrosting efficiency. In this step, the VOC airflow can be heated and raised in temperature by the defrosting device 80 in the main airflow pipe 110 or before entering the first-stage pre-cooling treatment.

[0105] Here, interrupting the refrigerant supply for the first-stage pre-cooling treatment and heating the VOC airflow before the first split, the two treatment processes can be carried out simultaneously or alternatively.

[0106] After the frosting phenomenon is eliminated, the normal operation of the VOC airflow is restored. In order to avoid the discharge of unpurified VOC airflow, the defrosting treatment step of the present invention also includes: when the frosting phenomenon is eliminated, the shunt channel between the VOC airflow and another sub-airflow is closed to stop the supply of the defrosting airflow; the supply of the cold source in the three-stage final cooling treatment of the sub-airflow that eliminates the frosting is restored, and the sub-airflow that eliminates the frosting flows along the purification route for purification treatment, and the purified clean airflow enters the purification route of another sub-airflow along the reverse route of the defrosting airflow. After running for a preset period of time, the discharge channel of the sub-airflow that eliminates the frosting is opened, the channel for the defrosting airflow to reversely enter the secondary condensation treatment is closed, and finally the shunt channel between the VOC airflow and another sub-airflow is restored.

[0107] More specifically, for example, after the frosting phenomenon of the first condensation subsystem 91 is eliminated, the diversion channel between the VOC airflow and the second sub-airflow is closed, and the diversion three-way valve 113 is in a purification state, so that the second sub-airflow will not be divided to form the first defrosting airflow. The first airflow flows along its own purification route into the first condensation subsystem 91 for purification treatment to form a clean airflow, which enters the purification route of the second sub-airflow along the reverse route of the first defrosting airflow, that is, enters the second condensation subsystem 92. After running for a preset time, it can be ensured that there is no unpurified first defrosting airflow in the first condensation cold air channel 212, and then the discharge channel of the first airflow is opened, and at the same time, the channel for the first defrosting airflow to enter the first condensing device 21 is closed, and finally the diversion channel between the VOC airflow and the second sub-airflow is opened, and the diversion three-way valve 113 is in a diversion state. At this time, the normal processing of the VOC airflow is restored, and the defrosting process is completed.

[0108] When frosting occurs in the second sub-airflow, the first sub-airflow is split for a second time to separate a second defrosting airflow, and the second defrosting airflow is used to defrost the purification channel of the second sub-airflow. The process is the same as that when frosting occurs in the first airflow, and will not be repeated here.

[0109] In summary, although the present invention has been disclosed as above in terms of preferred embodiments, the above preferred embodiments are not intended to limit the present invention. A person skilled in the art may make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be based on the scope defined in the claims.

Claims

1. A method for VOC condensation recovery, which is used for condensing and recovering VOC gas flow, characterized in that, it includes the following steps: The VOC gas flow is successively subjected to primary precooling treatment, secondary condensation treatment, and tertiary final cooling treatment, and finally a clean gas flow is generated; after the VOC gas flow is subjected to the primary precooling treatment, it is first split to be divided into two or more sub-gas flows, which are respectively and successively subjected to the secondary condensation treatment and the tertiary final cooling treatment; solvents are generated during the primary precooling treatment, secondary condensation treatment, and tertiary final cooling treatment of the VOC gas flow, and the solvents are collected into a solvent storage tank; In the tertiary final cooling treatment, the refrigerant is used as a cold source, and the cold source forms a secondary cold source after passing through the tertiary final cooling treatment, and the secondary cold source is used as the refrigerant for the primary precooling treatment; the clean gas flow is used as the refrigerant for the secondary condensation treatment; The VOC condensation recovery method further includes a defrosting treatment step; when frosting occurs during the purification treatment of one of the sub-gas flows, the defrosting treatment step is executed; the defrosting treatment step includes: closing the discharge channel of the sub-gas flow, and interrupting the cold source supply in the tertiary final cooling treatment of the sub-gas flow, splitting the other sub-gas flow a second time to separate a defrosting gas flow, and the defrosting gas flow flows reversely along the purification route of the sub-gas flow to perform defrosting treatment.

2. The VOC condensation recovery method according to claim 1, characterized in that, The defrosting treatment step further includes: directly discharging the secondary cold source formed after passing through the tertiary final cooling treatment, and interrupting the refrigerant supply for the primary precooling treatment.

3. The VOC condensation recovery method according to claim 1 or 2, characterized in that, The defrosting treatment step further includes: heating the VOC gas flow before the first splitting.

4. The VOC condensation recovery method according to claim 1, characterized in that, The defrosting treatment step further includes: When the frosting phenomenon is eliminated, close the splitting channel between the VOC gas flow and the other sub-gas flow to stop supplying the defrosting gas flow; Restore the cold source supply in the tertiary final cooling treatment of the sub-gas flow with the eliminated frosting, and the sub-gas flow with the eliminated frosting flows along the purification route for purification treatment. The purified clean gas flow enters the purification route of the other sub-gas flow along the reverse route of the defrosting gas flow; After running for a preset duration, open the discharge channel of the sub-gas flow with the eliminated frosting, and close the channel for the defrosting gas flow to enter the secondary condensation treatment reversely; Restore the splitting channel between the VOC gas flow and the other sub-gas flow.

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