Coating line waste gas treatment device and method

Abstract

The invention discloses a coating line waste gas treatment device and method, and belongs to the technical field of paint mist waste gas treatment. The device comprises a spray absorption tower, a dry filter, an activated carbon adsorber, a catalytic combustion device, an exhaust chimney and a main fan, the spray absorption tower, the dry filter, the activated carbon adsorber and the exhaust chimney are sequentially connected, the main fan is connected with the exhaust chimney, and the catalytic combustion device is connected between the activated carbon adsorber and the exhaust chimney. The activated carbon adsorber comprises a first activated carbon adsorption bed, a second activated carbon adsorption bed, a third activated carbon adsorption bed and a fourth activated carbon adsorption bed which are sequentially and circularly connected end to end through a connecting pipeline, and an adsorption air inlet branch pipe and an adsorption exhaust branch pipe are arranged on the connecting pipeline between every two adjacent activated carbon adsorption beds; and three-way valves are arranged between the adsorption air inlet branch pipe and the connecting pipeline and between the adsorption exhaust branch pipe and the connecting pipeline. The service life and environmental protection of the activated carbon adsorption bed can be effectively considered.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of paint mist waste gas treatment, in particular to a coating line waste gas treatment device and method. BACKGROUND

[0002] At present, for the treatment of coating waste gas, the treatment process of “activated carbon adsorption + desorption combustion” is usually adopted, and the main process is as follows: the waste gas is introduced into the activated carbon adsorption bed, the volatile organic compounds in the waste gas are adsorbed by the activated carbon, and the purified gas is directly discharged into the atmosphere; when the activated carbon adsorption bed reaches saturation, the desorption mode is entered, the activated carbon adsorption bed is reversely swept by hot air, the volatile organic compounds are taken out to the catalytic combustion furnace, and the volatile organic compounds are decomposed into carbon dioxide and water in the catalytic combustion furnace by using high temperature and catalyst, and a large amount of heat is released.

[0003] However, the above-mentioned existing waste gas treatment method still has the problem of being unable to balance the service life of the activated carbon adsorption bed and environmental protection. SUMMARY

[0004] The present application relates to the technical field of paint mist waste gas treatment, in particular to a coating line waste gas treatment device and method.

[0005] The purpose of the present application is achieved by the following technical scheme:

[0006] A coating line waste gas treatment device, comprising a spray absorption tower, a dry filter, an activated carbon adsorber, a catalytic combustion device, an exhaust chimney and a main fan, the spray absorption tower, the dry filter, the activated carbon adsorber and the exhaust chimney are connected in sequence, the main fan is connected to the exhaust chimney, the catalytic combustion device is connected between the activated carbon adsorber and the exhaust chimney, the activated carbon adsorber comprises a first activated carbon adsorption bed, a second activated carbon adsorption bed, a third activated carbon adsorption bed and a fourth activated carbon adsorption bed which are connected in sequence by connecting pipes, and the connecting pipes between the adjacent two activated carbon adsorption beds are provided with an adsorption air inlet branch pipe and an adsorption air outlet branch pipe, and the adsorption air inlet branch pipe and the adsorption air outlet branch pipe are provided with a three-way valve between the connecting pipes.

[0007] As a preferred, the air inlet end and the air outlet end of each activated carbon adsorption bed are provided with a volatile organic compound concentration monitor.

[0008] As a preferred, the three-way valve is arranged close to the activated carbon adsorption bed.

[0009] As a preferred, the four adsorption air inlet branch pipes are connected to an adsorption air inlet main pipe, the four adsorption air outlet branch pipes are connected to an adsorption air outlet main pipe, the adsorption air inlet main pipe is connected to the dry filter, and the adsorption air outlet main pipe is connected to the exhaust chimney.

[0010] Preferably, an air inlet control valve is arranged between the air inlet branch pipe and the air inlet main pipe, and an air outlet control valve is arranged between the air outlet branch pipe and the air outlet main pipe.

[0011] The present specification also provides a coating line waste gas treatment method using the coating line waste gas treatment device described above, the method comprising:

[0012] The first and second activated carbon adsorption beds are connected in series to adsorb the waste gas in turn, while the third activated carbon adsorption bed is cooled and the fourth activated carbon adsorption bed is desorbed;

[0013] When the first activated carbon adsorption bed is saturated, the second and third activated carbon adsorption beds are connected in series to adsorb the waste gas in turn, while the fourth activated carbon adsorption bed is cooled and the first activated carbon adsorption bed is desorbed;

[0014] When the second activated carbon adsorption bed is saturated, the third and fourth activated carbon adsorption beds are connected in series to adsorb the waste gas in turn, while the first activated carbon adsorption bed is cooled and the second activated carbon adsorption bed is desorbed;

[0015] And so on.

[0016] Preferably, the method for determining whether the activated carbon adsorption bed is saturated comprises monitoring the volatile organic compound concentration at the air inlet end and the air outlet end of the activated carbon adsorption bed, and determining that the activated carbon adsorption bed is saturated when the difference between the volatile organic compound concentrations at the air inlet end and the air outlet end is less than a set threshold value.

[0017] Preferably, when two activated carbon adsorption beds are connected in series to adsorb the waste gas, the volatile organic compound concentration at the air outlet end of the activated carbon adsorption bed at the tail is monitored in real time, and an abnormality alarm is triggered when the volatile organic compound concentration at the air outlet end of the activated carbon adsorption bed at the tail is greater than zero.

[0018] The present application has the following advantages:

[0019] 1. The two activated carbon adsorption beds are connected in series to adsorb the coating waste gas, which can avoid the volatile organic compounds overflowing from the activated carbon adsorption bed at the head being directly discharged into the atmosphere, but being adsorbed by the activated carbon adsorption bed at the tail, thereby effectively achieving zero discharge of volatile organic compounds and avoiding air pollution.

[0020] 2. Since the activated carbon adsorption bed at the tail can effectively adsorb the volatile organic compounds overflowing from the activated carbon adsorption bed at the head, the activated carbon adsorption bed at the head can be desorbed after reaching a completely saturated state, thereby reducing the desorption frequency of the activated carbon adsorption bed and prolonging the service life.

[0021] 3. By sequentially cycling the working state of the four activated carbon adsorption beds, the efficient and orderly operation of the entire exhaust gas treatment device is ensured. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 A top view of a coating line exhaust gas treatment device according to an embodiment of the present specification;

[0023] Figure 2 A structure diagram of an activated carbon adsorber according to an embodiment of the present specification;

[0024] Figure 3 A flow chart of a coating line exhaust gas treatment method according to an embodiment of the present specification;

[0025] In the figure: 1 - spray absorption tower; 2 - dry filter; 3 - activated carbon adsorber; 31 - first activated carbon adsorption bed; 311 - first adsorption inlet branch pipe; 312 - first adsorption exhaust branch pipe; 32 - second activated carbon adsorption bed; 321 - second adsorption inlet branch pipe; 322 - second adsorption exhaust branch pipe; 33 - third activated carbon adsorption bed; 331 - third adsorption inlet branch pipe; 332 - third adsorption exhaust branch pipe; 34 - fourth activated carbon adsorption bed; 341 - fourth adsorption inlet branch pipe; 342 - fourth adsorption exhaust branch pipe; 35 - connecting pipeline; 36 - three-way valve; 37 - adsorption inlet main pipe; 38 - adsorption exhaust main pipe; 39 - volatile organic compound concentration monitor; 4 - catalytic combustion device; 5 - exhaust chimney; 6 - main fan; 71 - recent control valve; 72 - exhaust control valve. DETAILED DESCRIPTION

[0026] The present application will be further described in detail below in conjunction with the drawings and specific embodiments.

[0027] As mentioned in the background art, the existing coating exhaust gas treatment process, for the determination of the saturation of the activated carbon adsorption bed, usually uses a volatile organic compound concentration monitor installed in the exhaust gas outlet pipeline of the activated carbon adsorption bed to monitor. When the concentration exceeds the set threshold, it is determined that the adsorption bed has been saturated and needs to be desorbed. However, the determination of the saturation of the adsorption bed is not complete saturation. The higher the concentration of volatile organic compounds in the activated carbon adsorption bed exhaust gas outlet pipeline, the higher the degree of saturation of the activated carbon adsorption bed. When the concentration of volatile organic compounds in the outlet pipeline is comparable to that in the inlet pipeline, the activated carbon adsorption bed is considered to be completely saturated, and the concentration of volatile organic compounds at this time must be far exceeding the environmental protection standard. Therefore, only a relatively low threshold can be set to ensure that the emission concentration of volatile organic compounds meets the environmental protection requirements, that is, when the activated carbon adsorption bed has not reached complete saturation, the desorption process will be carried out, and accordingly, the desorption frequency of the activated carbon adsorption bed will be increased, and the desorption frequency will directly affect the service life of the activated carbon adsorption bed. Therefore, the lower the saturation of the activated carbon adsorption bed, the lower the emission concentration of volatile organic compounds, the better it meets the environmental protection requirements, but the service life is reduced. The higher the saturation of the activated carbon adsorption bed, the lower the desorption frequency, the longer the service life, but the higher the emission concentration of volatile organic compounds, the more difficult it is to meet the environmental protection requirements.

[0028] In summary, the prior art cannot effectively balance the service life of the activated carbon adsorption bed and environmental protection.

[0029] Therefore, as mentioned above, Figure 1As shown in the figure, this embodiment provides a coating line exhaust gas treatment device, including a spray absorption tower 1, a dry filter 2, an activated carbon adsorber 3, a catalytic combustion device 4, an exhaust chimney 5, and a main fan 6. The spray absorption tower 1, dry filter 2, activated carbon adsorber 3, and exhaust chimney 5 are connected in sequence. The main fan 6 is connected to the exhaust chimney 5, and the catalytic combustion device 4 is connected between the activated carbon adsorber 3 and the exhaust chimney 5. The entire device also includes a desorption fan, a cooling fan, and their piping, which are not shown in the figure. These are all conventional structures and will not be described in detail. In a relatively conventional manner: the coating exhaust gas first passes through the spray absorption tower 1 to remove pollutants such as paint mist, xylene, and benzene; then it passes through the dry filter 2 to remove fine particulate matter from the exhaust gas to prevent clogging of the activated carbon adsorption bed. Next, the activated carbon adsorption bed in activated carbon adsorber 3 is introduced. The activated carbon adsorbs the volatile organic compounds (VOCs) in the waste gas. The purified gas is directly discharged into the atmosphere through exhaust chimney 5. When the activated carbon adsorption bed reaches saturation, it enters desorption mode. Hot air generated by the desorption fan is used to back-blownly sweep the activated carbon adsorption bed, carrying the VOCs to the catalytic combustion device 4. In the catalytic combustion device 4, the VOCs are decomposed into carbon dioxide and water by high temperature and the action of a catalyst, releasing a large amount of heat. The activated carbon adsorption bed that has completed desorption is gradually cooled by a cooling fan. After cooling, it can be used for waste gas adsorption again. The connection pipelines between the desorption fan and the cooling fan and the activated carbon adsorption bed adopt existing technology. They are generally connected to the activated carbon adsorption bed by independent pipelines. Multiple activated carbon adsorption beds are connected to the desorption and cooling pipelines in parallel, and valves are used to control the connection of the activated carbon adsorption bed that needs to be desorbed or cooled.

[0030] Correspondingly, for the adsorption process, the existing technology also uses multiple activated carbon adsorption beds in parallel. The waste gas is controlled by valves to enter the corresponding activated carbon adsorption bed for adsorption. That is, after the waste gas passes through an activated carbon adsorption bed, it needs to be discharged into the atmosphere through an exhaust chimney, which causes the above-mentioned problems.

[0031] Unlike existing technologies, such as Figure 2 As shown, the activated carbon adsorber 3 in this embodiment includes a first activated carbon adsorption bed 31, a second activated carbon adsorption bed 32, a third activated carbon adsorption bed 33, and a fourth activated carbon adsorption bed 34, which are connected end-to-end by connecting pipes. Each connecting pipe 35 between adjacent activated carbon adsorption beds is equipped with an adsorption inlet branch pipe and an adsorption exhaust branch pipe. A three-way valve 36 is installed between each adsorption inlet branch pipe and the adsorption exhaust branch pipe and the connecting pipe 35. Specifically, the three-way valve 36 can be an electromagnetic three-way valve for automated control. The four adsorption inlet branch pipes are connected to the adsorption inlet main pipe 37, and the four adsorption exhaust branch pipes are connected to the adsorption exhaust main pipe 38. The adsorption inlet main pipe 37 is connected to the dry filter 2, and the adsorption exhaust main pipe 38 is connected to the exhaust chimney 5.

[0032] For a clearer illustration, the first adsorption inlet branch pipe 311 is at the gas inlet end of the first activated carbon adsorption bed 31, and the first adsorption exhaust branch pipe 312 is at the gas exhaust end; the second adsorption inlet branch pipe 321 is at the gas inlet end of the second activated carbon adsorption bed 32, and the second adsorption exhaust branch pipe 322 is at the gas exhaust end; the third adsorption inlet branch pipe 331 is at the gas inlet end of the third activated carbon adsorption bed 33, and the third adsorption exhaust branch pipe 332 is at the gas exhaust end; and the fourth adsorption inlet branch pipe 341 is at the gas inlet end of the fourth activated carbon adsorption bed 34, and the fourth adsorption exhaust branch pipe 342 is at the gas exhaust end.

[0033] The working principle of the activated carbon adsorber in this embodiment is as follows: through the control of the three-way valve 36, the first activated carbon adsorption bed 31 and the second activated carbon adsorption bed 32 are connected in series to the adsorption pipeline, that is, the exhaust gas is introduced into the first activated carbon adsorption bed 31 from the first adsorption inlet branch pipe 311, and after being discharged from the first activated carbon adsorption bed 31, it is introduced into the second activated carbon adsorption bed 32, and after being discharged from the second activated carbon adsorption bed 32, it is discharged into the exhaust chimney 5 through the second adsorption exhaust branch pipe 322; in this process, the third activated carbon adsorption bed 33 and the fourth activated carbon adsorption bed 34 are cut off from the communication relationship with the first and second activated carbon adsorption beds by the three-way valve 36, and at the same time, the third and fourth activated carbon adsorption beds can carry out the desorption or cooling process. When the first activated carbon adsorption bed 31 is from the process of being about to be saturated to being completely saturated, due to the decrease of its adsorption capacity, volatile organic compounds will overflow, but they will be completely adsorbed by the second activated carbon adsorption bed 32, and the amount of volatile organic compounds overflowing in this process is far lower than the adsorbable amount of the second activated carbon adsorption bed 32, so that no volatile organic compounds will be discharged from the second activated carbon adsorption bed 32. Then, through the switching of the three-way valve 36, the second activated carbon adsorption bed 32 and the third activated carbon adsorption bed 33 are connected in series to the adsorption pipeline, the second activated carbon adsorption bed 32 which has adsorbed a small amount of volatile organic compounds continues to adsorb the exhaust gas, the overflowing volatile organic compounds are adsorbed by the third activated carbon adsorption bed 33, and the saturated first activated carbon adsorption bed 31 enters the desorption process, and after the desorption is completed, it enters the cooling process, and after the cooling is completed, it enters the standby state, waiting to be connected to the adsorption pipeline again. Repeating the above process can realize zero emission of volatile organic compounds of the activated carbon adsorber 3, which is conducive to improving environmental protection; at the same time, since each activated carbon adsorption bed is desorbed only after being completely saturated, the overall desorption frequency is reduced, and the service life is prolonged.

[0034] Specifically, in order to automatically control the switching timing of the three-way valve, the inlet end and the outlet end of each activated carbon adsorption bed are provided with volatile organic compound concentration monitors 39 to determine whether the activated carbon adsorption bed reaches a fully saturated state according to the volatile organic compound concentration. Generally, when the volatile organic compound concentrations at the inlet end and the outlet end of the activated carbon adsorption bed are equivalent, that is, the difference between the volatile organic compound concentrations at the inlet end and the outlet end of the activated carbon adsorption bed is less than a set threshold, it is determined that the activated carbon adsorption bed reaches saturation. The set threshold can be a small value, for example, 50-100 mg / m 3 . Alternatively, we can also determine according to the volatile organic compound concentration at the outlet end of the activated carbon adsorption bed. When the volatile organic compound concentration at the outlet end of the activated carbon adsorption bed is greater than a set threshold, it is determined that the activated carbon adsorption bed reaches full saturation. In the prior art, the set threshold is generally 30-40 mg / m 3 . However, in the present embodiment, since there is an activated carbon adsorption bed connected in series behind, the set threshold can be a larger value, for example, 300-400 mg / m 3 , so as to ensure that the activated carbon adsorption bed at the head reaches or approaches full saturation as much as possible.

[0035] In order to reduce the residue of waste gas in the connecting pipeline, the three-way valve 36 is arranged as close to the activated carbon adsorption bed as possible.

[0036] In order to improve the reliability of the control of the waste gas flow direction, an inlet control valve 71 is arranged between the adsorption inlet branch pipe and the adsorption inlet main pipe, and an exhaust control valve 72 is arranged between the adsorption exhaust branch pipe and the adsorption exhaust main pipe.

[0037] As shown in Figure 3 , the present specification also provides a coating line waste gas treatment method, which adopts the coating line waste gas treatment device as described above. The method comprises the following steps:

[0038] Step s1, sequentially connecting the first activated carbon adsorption bed 31 and the second activated carbon adsorption bed 32 in series to adsorb waste gas, while allowing the third activated carbon adsorption bed 33 to cool and the fourth activated carbon adsorption bed 34 to desorb;

[0039] Step s2, when the first activated carbon adsorption bed 31 is saturated, sequentially connecting the second activated carbon adsorption bed 32 and the third activated carbon adsorption bed 33 in series to adsorb waste gas, while allowing the fourth activated carbon adsorption bed 34 to cool and the first activated carbon adsorption bed 31 to desorb;

[0040] Step s3, when the second activated carbon adsorption bed 32 is saturated, sequentially connecting the third activated carbon adsorption bed 33 and the fourth activated carbon adsorption bed 34 in series to adsorb waste gas, while allowing the first activated carbon adsorption bed 31 to cool and the second activated carbon adsorption bed 32 to desorb;

[0041] Step s4, and so on. The detailed process can refer to the above, which is not described here.

[0042] Since the adsorption time of the activated carbon adsorption bed is much longer than the desorption and cooling time, when one activated carbon adsorption bed reaches saturation, there must be other idle activated carbon adsorption beds that can seamlessly connect.

[0043] The method for determining that the activated carbon adsorption bed reaches saturation includes: monitoring the volatile organic compound concentrations at the gas inlet end and the gas outlet end of the activated carbon adsorption bed, and determining that the activated carbon adsorption bed reaches saturation when the difference between the volatile organic compound concentrations at the gas inlet end and the gas outlet end of the activated carbon adsorption bed is less than a set threshold value.

[0044] In order to avoid the concentration of volatile organic compounds in the discharged gas exceeding the standard due to equipment abnormalities, when two activated carbon adsorption beds are sequentially connected in series to adsorb the exhaust gas, the volatile organic compound concentration at the gas outlet end of the activated carbon adsorption bed at the tail is monitored in real time, and when the volatile organic compound concentration at the gas outlet end of the activated carbon adsorption bed at the tail is greater than zero, an abnormality alarm is performed.

[0045] The above is only a preferred specific embodiment of the present application, which is an implementation based on the overall concept of the present application, and the protection scope of the present application is not limited thereto. Any person skilled in the art can easily think of changes or replacements within the technical scope disclosed by the present application, which should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A coating line exhaust gas treatment device, comprising a spray absorption tower, a dry filter, an activated carbon adsorber, a catalytic combustion device, an exhaust chimney, and a main fan, wherein the spray absorption tower, dry filter, activated carbon adsorber, and exhaust chimney are connected in sequence, the main fan is connected to the exhaust chimney, and the catalytic combustion device is connected between the activated carbon adsorber and the exhaust chimney, characterized in that, The activated carbon adsorber includes a first activated carbon adsorption bed, a second activated carbon adsorption bed, a third activated carbon adsorption bed, and a fourth activated carbon adsorption bed that are connected end to end by connecting pipes. Each connecting pipe between two adjacent activated carbon adsorption beds is equipped with an adsorption inlet branch pipe and an adsorption exhaust branch pipe. A three-way valve is provided between the adsorption inlet branch pipe and the adsorption exhaust branch pipe and the connecting pipe.

2. The coating line exhaust gas treatment device according to claim 1, characterized in that, Each activated carbon adsorption bed is equipped with a volatile organic compound concentration monitor at both the inlet and outlet ends.

3. The coating line exhaust gas treatment device according to claim 1, characterized in that, The three-way valve is located near the activated carbon adsorption bed.

4. The coating line exhaust gas treatment device according to claim 1, characterized in that, The four adsorption inlet branch pipes are connected to the adsorption inlet main pipe, the four adsorption exhaust branch pipes are connected to the adsorption exhaust main pipe, the adsorption inlet main pipe is connected to the dry filter, and the adsorption exhaust main pipe is connected to the exhaust chimney.

5. The coating line exhaust gas treatment device according to claim 4, characterized in that, An intake control valve is provided between the adsorption intake branch pipe and the adsorption intake main pipe, and an exhaust control valve is provided between the adsorption exhaust branch pipe and the adsorption exhaust main pipe.

6. A method for treating exhaust gas from a painting line, characterized in that, The method of using the coating line exhaust gas treatment device as described in claim 1 includes: The first and second activated carbon adsorption beds are connected in series to adsorb the waste gas, while the third activated carbon adsorption bed is cooled and the fourth activated carbon adsorption bed is desorbed. When the first activated carbon adsorption bed is saturated, the second and third activated carbon adsorption beds are connected in series to adsorb the waste gas, while the fourth activated carbon adsorption bed is cooled and the first activated carbon adsorption bed is desorbed. When the second activated carbon adsorption bed is saturated, the third and fourth activated carbon adsorption beds are connected in series to adsorb the waste gas, while the first activated carbon adsorption bed is cooled and the second activated carbon adsorption bed is desorbed. And so on.

7. A method for treating exhaust gas from a painting line according to claim 6, characterized in that, Methods for determining whether an activated carbon adsorption bed has reached saturation include: monitoring the concentration of volatile organic compounds (VOCs) at the inlet and outlet of the activated carbon adsorption bed; when the difference in VOC concentration between the inlet and outlet of the activated carbon adsorption bed is less than a set threshold, the activated carbon adsorption bed is determined to have reached saturation.

8. A method for treating exhaust gas from a painting line according to claim 6, characterized in that, When two activated carbon adsorption beds are connected in series to adsorb waste gas, the concentration of volatile organic compounds at the exhaust end of the activated carbon adsorption bed at the tail end is monitored in real time. When the concentration of volatile organic compounds at the exhaust end of the activated carbon adsorption bed at the tail end is greater than zero, an abnormal alarm is triggered.

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