Catalytic oxidation system for converting and removing VOCs (Volatile Organic Compounds)

Abstract

The utility model relates to the technical field of waste gas treatment, in particular to a catalytic oxidation system and method for converting and removing VOCs (Volatile Organic Compounds). The system comprises a reactor, a steam pocket and a water replenishing system, the reactor comprises a gas inlet, a gas outlet and a plurality of catalytic bed layers which are sequentially arranged at intervals in the gas flow direction; a heat exchange coil pipe is arranged between every two adjacent catalytic bed layers; a circulation loop is formed between the heat exchange coil and the steam pocket; the upstream of the air inlet is connected with a preheater; the water supplementing system comprises a first heat exchanger and a water supplementing tank used for supplementing water into the steam pocket, and water in the water supplementing tank can circularly flow between the water supplementing tank and the first heat exchanger. The waste heat of the waste gas discharged from the gas outlet can heat the water in the water replenishing tank, and the heat exchange coil in the scheme is not contacted with the catalytic bed layer, so that the temperature distribution in the catalytic bed layer is more uniform, and the catalytic oxidation reaction effect is better facilitated.

Description

Technical Field

[0001] The utility model relates to the technical field of waste gas treatment, and particularly relates to a catalytic oxidation system for VOCs conversion and removal. Background Art

[0002] Volatile organic compounds (VOCs) are important pollutants that affect the environment and human beings, and are also important precursors of ozone, PM2.5, secondary organic aerosols, etc. in the atmosphere. The coal chemical industry is one of the important sources of air pollution, and the environmental protection requirements are very strict.

[0003] At present, the mainstream method for treating VOCs is direct combustion. Due to the relatively high operating temperature of the direct combustion method, problems such as the easy generation of polluting gases such as NOx are likely to occur. Therefore, in some related technologies, catalytic oxidation is used to treat VOCs.

[0004] The catalytic oxidation technology (CO) operates at a relatively low temperature (200°C - 600°C), and has advantages such as less auxiliary fuel consumption, high safety, and low NOx emissions. It is the development direction of the VOCs treatment plan in the coal chemical industry. For the catalytic oxidation technology, mainly a catalyst is used to catalytically oxidize VOCs so that they decompose into carbon dioxide and water. For this catalytic oxidation technology, reference can be made to the catalytic oxidation system for efficient conversion and removal of VOCs in the coal chemical industry disclosed in the patent with the publication number CN117732242B.

[0005] However, for the above-mentioned catalytic oxidation system, there are still defects in actual application:

[0006] Firstly, the heat exchange tubes for cooling the catalyst are directly buried in the catalyst. In this way, the tube wall of the heat exchange tube is in direct contact with the catalyst, resulting in a lower temperature of the catalyst closer to the tube wall of the heat exchange tube. When the temperature difference between the catalyst and the medium in the heat exchange tube is large, a temperature gradient will occur inside the catalyst, making the temperature distribution of the catalyst uneven. For example, the temperature of the catalyst closer to the tube wall of the heat exchange tube is lower, resulting in a reduced catalytic efficiency of the catalyst at this position.

[0007] Secondly, in actual use of the steam drum, as the steam drum is continuously used, the water inside it will decrease, so it is necessary to replenish water. If water with a relatively low temperature, such as normal temperature water, is directly introduced into the steam drum for water replenishment, the steam generation efficiency will be affected. Summary of the Utility Model

[0008] In order to solve at least one technical problem mentioned in the background art, the purpose of the present utility model is to provide a catalytic oxidation system and method for VOCs conversion and removal.

[0009] To achieve the above purpose, the present utility model provides the following technical solutions:

[0010] On the one hand, the utility model provides a catalytic oxidation system for VOCs conversion and removal, which includes a reactor, a steam drum and a water replenishment system; the reactor includes an air inlet, an air outlet and a plurality of catalytic bed layers arranged at intervals in sequence along the gas flow direction; a heat exchange coil is arranged between adjacent catalytic bed layers, and there is a gap between the heat exchange coil and the adjacent catalytic bed layer; a circulation loop is formed between the heat exchange coil and the steam drum; a preheater is connected upstream of the air inlet; the water replenishment system includes a first heat exchanger and a water replenishment tank for replenishing water into the steam drum, and the water in the water replenishment tank can circulate between the water replenishment tank and the first heat exchanger; the air flow discharged from the air outlet is discharged after passing through the first heat exchanger; the steam drum is connected with a steam pipeline for transporting steam and having a first valve.

[0011] Compared with the prior art, the advantages of adopting this solution are as follows:

[0012] First of all, in this solution, multiple catalytic bed layers are provided, so that VOCs can be catalytically oxidized successively through each catalytic bed layer and decomposed into carbon dioxide and water; compared with the method of only setting one catalytic bed layer, the catalytic efficiency is undoubtedly higher.

[0013] Secondly, in this solution, adjacent catalytic bed layers are arranged at intervals, and a heat exchange coil is arranged between adjacent catalytic bed layers. In this way, a cooling zone is formed between adjacent catalytic bed layers. The heat released during the oxidation reaction of the VOCs waste gas passing through the upstream catalytic bed layer continues to move forward with the waste gas and is cooled by the heat exchange coil when passing through the heat exchange coil, so that the temperature of the waste gas is reduced to the required temperature (350°C - 450°C) before entering the next catalytic bed layer, so as to ensure that the waste gas can carry out an effective catalytic reaction with the next catalytic bed layer at an appropriate temperature.

[0014] It can be seen that in this solution, the cooling of the downstream catalytic bed layer is achieved by cooling the waste gas, and then indirectly cooling the catalytic bed layer by the cooled waste gas, rather than directly contacting the heat exchange coil with the catalytic bed layer for cooling. Compared with the method of directly contacting the heat exchange coil with the catalytic bed layer for cooling, in this solution, the heat exchange coil does not contact the catalytic bed layer. In this way, the temperature distribution in the catalytic bed layer can be relatively uniform, which is more conducive to the catalytic oxidation reaction effect.

[0015] Finally, in this solution, by setting up a water replenishment system and introducing the gas flow finally output from the gas outlet of the reactor (i.e., the purified waste gas, hereinafter referred to as the purified gas) into the first heat exchanger of the water replenishment system, since the water in the water replenishment tank circulates between the water replenishment tank and the first heat exchanger, and the purified gas output from the gas outlet still has residual heat, the purified gas will exchange heat with the water passing through the first heat exchanger through the first heat exchanger, transferring the heat to the water, thereby raising the temperature of the water in the water replenishment tank; when the water level in the steam drum drops and water replenishment is required, the water in the water replenishment tank can be introduced into the steam drum for water replenishment; since the water in the water replenishment tank has been heated, the impact on the steam generation efficiency of the steam drum when introduced into the steam drum is relatively small.

[0016] It can be seen that in this solution, the heat released by the waste gas reaction can be heat recovered twice. One time is to finally generate steam in the steam drum through the heat exchange coil, and the second time is to heat recover the purified gas output from the reactor to heat the water in the water replenishment tank for the water replenishment of the water replenishment tank to the steam drum.

[0017] As an optional implementation manner of the present utility model: the water replenishment system further includes a circulation pump, the water inlet end of the circulation pump is communicated with the water replenishment tank, the water outlet end of the circulation pump is connected with a water replenishment pipeline and a water outlet pipeline, the water replenishment pipeline is communicated with the steam drum; the water outlet pipeline is communicated with the water inlet end of the first heat exchanger; the water outlet end of the first heat exchanger is communicated with the water replenishment tank through a return water pipeline; the water replenishment pipeline is provided with a second valve.

[0018] As an optional implementation manner of the present utility model, the second valve is configured such that when the liquid level in the steam drum is lower than the set liquid level, the second valve opens; when the liquid level in the steam drum is higher than or equal to the set liquid level, the second valve closes.

[0019] As an optional implementation manner of the present utility model, the water replenishment system further includes a water injection pipeline connecting a water source for injecting water into the water replenishment tank; the water injection pipeline is provided with a third valve; the third valve is configured such that when the liquid level in the water replenishment tank is lower than the set liquid level, the third valve opens to inject water into the water replenishment tank through the water injection pipeline; when the liquid level in the water replenishment tank is higher than or equal to the set liquid level, the third valve closes.

[0020] As an optional implementation manner of the present utility model, the interval between the heat exchange coil and the adjacent catalyst bed layer is 100 mm - 600 mm.

[0021] As an optional implementation manner of the present utility model, the circulation loop includes a first pipeline and a second pipeline connected to the steam drum; the water inlet end of the heat exchange coil is connected with a water inlet branch pipeline, and the water outlet end of the heat exchange coil is connected with a water return branch pipeline; each water inlet branch pipeline is connected in parallel to the first pipeline; each water return branch pipeline is connected in parallel to the second pipeline; each water inlet branch pipeline is provided with a control valve for adjusting the flow rate.

[0022] As an alternative embodiment of the present utility model, the reactor further includes a second heat exchanger disposed upstream of the preheater, and the second heat exchanger is disposed between the gas outlet and the catalytic bed layer at the end; the VOCs waste gas to be treated sequentially passes through the second heat exchanger, the preheater, and the air inlet and then enters the reactor.

[0023] As an alternative embodiment of the present utility model, the catalytic bed layers are sequentially arranged vertically; the height of the bottom of the steam drum is higher than that of the uppermost heat exchange coil.

[0024] As an alternative embodiment of the present utility model, the catalytic bed layer is any one or a combination of several of granular, foam-type, and honeycomb-type catalysts.

[0025] On the other hand, the present utility model provides a catalytic oxidation method for VOCs conversion and removal, which is carried out by using the aforementioned catalytic oxidation system for VOCs conversion and removal, and includes the following steps:

[0026] - Inject water into the makeup water tank and inject water into the steam drum through the makeup water tank;

[0027] - Start the system, introduce the VOCs waste gas, and preheat the VOCs waste gas through the preheater, control the temperature of the waste gas between 350°C and 450°C, and the preheated VOCs waste gas enters the reactor through the air inlet and sequentially flows through each catalytic bed layer; the VOCs waste gas undergoes an oxidation reaction through the catalytic action of the catalytic bed layer;

[0028] - Control the flow rate of the heat exchange coil to adjust the inlet air temperature of the downstream catalytic bed layer between 350°C and 450°C;

[0029] - The purified waste gas flows through the first heat exchanger after flowing out of the gas outlet, so as to perform heat exchange with the water circulating between the makeup water tank and the first heat exchanger, and realize heating of the water in the makeup water tank;

[0030] - When the pressure in the steam drum exceeds the set value, the first valve opens, and the steam is output via the steam pipeline. When the pressure in the steam drum returns below the set value, the first valve closes;

[0031] - When the liquid level in the steam drum is lower than the set liquid level, the makeup water tank starts to replenish water into the steam drum until the liquid level in the steam drum reaches the set liquid level.

[0032] Other advantages and effects of the present utility model are specifically explained in the specific embodiments and the drawings section. Brief Description of the Drawings

[0033] Figure 1 It is a structural schematic diagram of the present utility model;

[0034] Figure 2 This is a schematic structural view of the reactor of the present utility model. Specific embodiments

[0035] The technical solutions of the embodiments of the present utility model will be explained and described below with reference to the accompanying drawings of the embodiments of the present utility model. However, the following embodiments are only the preferred embodiments of the present utility model and not all of them. Based on the embodiments in the embodiments, other embodiments obtained by those skilled in the art without creative work all fall within the protection scope of the present utility model.

[0036] In the following description, terms indicating orientation or positional relationship such as "inner", "outer", "upper", "lower", "left", "right", etc. are only for the convenience of describing the embodiments and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present utility model.

[0037] Embodiment 1

[0038] Please refer to Figure 1-2 As shown, this embodiment provides a catalytic oxidation system for VOCs conversion and removal, including a reactor 1, a steam drum 2, a water replenishment system, etc.

[0039] The reactor 1 mainly serves as a place for the catalytic oxidation reaction of VOCs waste gas (hereinafter referred to as waste gas); the reactor 1 includes an air inlet 12, an air outlet 13, and a number of catalytic beds 11 arranged at intervals in sequence along the gas flow direction; a heat exchange coil 15 is provided between adjacent catalytic beds 11. As Figure 2 shown, there is a gap d between the heat exchange coil 15 and the adjacent catalytic bed 11. Preferably, the gap d between the heat exchange coil 15 and the adjacent catalytic bed 11 is 100 mm - 600 mm.

[0040] As an alternative embodiment, in this embodiment, as Figure 2 shown, taking the upward flow of gas as an example, the reactor 1 includes a housing 10. The air inlet 12 is provided at the bottom of the housing 10 for introducing the waste gas to be purified; the air outlet 13 is provided at the top of the housing 10 for discharging the treated waste gas. For the convenience of description, in this embodiment, the waste gas discharged after treatment will be hereinafter referred to as purified gas.

[0041] Each catalytic bed 11 is arranged at intervals in sequence in the vertical direction. Among them, the catalytic bed 11 is preferably 2 - 8 layers, and the number of catalytic beds 11 is one more than that of the heat exchange coils 15. The heat exchange coil 15 is preferably made of 2205 duplex stainless steel finned tubes with an inner diameter of 5 mm - 40 mm.

[0042] Among them, the catalytic bed layer 11 includes a catalyst, and the catalyst can be any one or a combination of several of particulate, foam-type, and honeycomb-type catalysts. When the waste gas passes through the catalytic bed layer 11, it can be catalytically oxidized and decomposed into carbon dioxide and water under the catalysis of the catalyst in the catalytic bed layer 11, and heat is released, so as to realize the purification of the waste gas.

[0043] As Figure 1 shown, a circulation loop is formed between the heat exchange coil 15 and the steam drum 2, and the steam drum 2 is connected to a steam pipeline 20 for transporting steam and having a first valve 201; the steam drum 2 is mainly used for injecting water for generating steam. Among them, the water introduced into the make-up water tank 31 and the steam drum 2 is preferably demineralized and softened water.

[0044] During the use process, after the waste gas undergoes an oxidation reaction in the catalytic bed layer 11, heat will be released. If this heat is directly carried into the downstream catalytic bed layer 11 by the waste gas, it will cause the temperature of the downstream catalytic bed layer 11 to be too high, which is not conducive to the catalytic reaction of the downstream catalytic bed layer 11. Therefore, a heat exchange coil 15 is provided between two adjacent catalytic bed layers 11. At this time, a cooling zone is formed between the two catalytic bed layers 11.

[0045] During the working process, the water in the steam drum 2 can circulate between the heat exchange coil 15 and the steam drum 2; the heat released during the oxidation reaction of the waste gas passing through the upstream catalytic bed layer 11 flows upward with the waste gas. When it passes through the heat exchange coil 15, it exchanges heat with the water in the heat exchange coil 15. In this way, the water in the heat exchange coil 15 can cool the waste gas passing through the heat exchange coil 15 to reduce it to the required temperature (350°C - 450°C), so as to ensure that the waste gas can effectively catalyze the reaction with the next catalytic bed layer 11 at an appropriate temperature.

[0046] It can be seen that in this embodiment, the cooling of the downstream catalytic bed layer 11 is achieved by cooling the waste gas, and then indirectly cooling the downstream catalytic bed layer 11 by the cooled waste gas, rather than directly contacting the heat exchange coil 15 with the catalytic bed layer 11 for cooling. Compared with the method of directly contacting the heat exchange coil 15 with the catalytic bed layer 11 for cooling, in this solution, the heat exchange coil 15 does not contact the catalytic bed layer 11. In this way, the temperature distribution in the catalytic bed layer 11 can be made more uniform, which is more conducive to the catalytic oxidation reaction effect.

[0047] Conversely, the waste gas passing through the heat exchange coil 15 can heat the water in the heat exchange coil 15 and finally form steam; the first valve 201 is a pressure control valve for controlling the on-off of the steam pipeline 20. When the pressure in the steam drum 2 exceeds the set value (0.1 MPa - 1.0 MPa), the steam is transported to the steam network through the first valve 201. When the pressure returns below the set value, the first valve 201 automatically closes.

[0048] The pressure inside the steam drum 2 is controlled by controlling the outward delivery of steam through the first valve 201 to be between 0.1 MPa and 1.0 MPa, thereby adjusting the steam temperature inside the steam drum 2 to be between 120 °C and 180 °C.

[0049] The water replenishing system is mainly used to replenish water to the steam drum 2. As Figure 1 shown, it includes a first heat exchanger 32 and a water replenishing tank 31 for replenishing water into the steam drum 2. The water in the water replenishing tank 31 can circulate between the water replenishing tank 31 and the first heat exchanger 32; the air outlet 13 is connected to the intake end of the first heat exchanger 32 through a pipeline, and the outlet end of the first heat exchanger 32 is connected to the chimney 5 through a pipeline; the airflow discharged from the air outlet 13 is discharged after passing through the first heat exchanger 32 and is finally discharged through the chimney 5.

[0050] There is still residual heat in the purified gas finally output from the air outlet 13. Thus, the purified gas will exchange heat with the water passing through the first heat exchanger 32 to transfer the heat to the water, thereby raising the temperature of the water in the water replenishing tank 31; thus, when the water level in the steam drum 2 drops and water replenishment is required, the water in the water replenishing tank 31 can be introduced into the steam drum 2 for water replenishment; since the water in the water replenishing tank 31 has been heated, the introduction into the steam drum 2 has a relatively small impact on the steam generation efficiency of the steam drum 2.

[0051] It can be seen that in this embodiment, the heat released by the waste gas reaction is recycled twice. One time is to finally generate steam in the steam drum 2 through the heat exchange coil 15, and the second time is to recycle the heat of the purified gas output from the reactor 1 to heat the water in the water replenishing tank 31 for subsequent water replenishment of the steam drum 2 by the water replenishing tank 31.

[0052] In addition, this embodiment further includes an intake pipeline 8 for introducing the waste gas to be treated into the reactor 1. Along the airflow direction on the intake pipeline 8, a blower 7, a second heat exchanger 16, and a preheater 6 are successively provided; the outlet end of the preheater 6 is communicated with the intake port 12; thus, the waste gas to be treated is blown out by the blower 7 and successively flows through the second heat exchanger 16, the preheater 6, and the intake port 12 to enter the reactor 1 for subsequent reactions.

[0053] The function of the preheater 6 is to preheat the waste gas. It can adopt an electric heater, mainly to preheat the waste gas at the initial stage of system operation so that the waste gas is preheated to 350 °C - 450 °C and then enters the reactor 1 for catalytic reaction.

[0054] The second heat exchanger 16 is arranged within the housing 10 and is disposed between the air outlet 13 and the catalytic bed layer 11 at the end (i.e., the uppermost catalytic bed); the second heat exchanger 16 is preferably a plate heat exchanger; thus, when the waste gas output from the uppermost catalytic bed flows through the second heat exchanger 16, it will exchange heat with the waste gas flowing through the second heat exchanger 16, heating the waste gas by the waste heat of the waste gas, and the heated waste gas then flows into the air inlet 12 through the preheater 6.

[0055] In addition, in order to enable the waste gas to be evenly dispersed after entering the reactor 1 through the air inlet 12, in this embodiment, an air flow distribution layer 14 is provided at the inner bottom of the housing 10. The air flow distribution layer 14 is made of any one or a combination of alumina, zirconia, and silicon carbide particles, and the particle size is 3 mm to 50 mm.

[0056] As Figure 1 shown, the specific structure of the circulation loop formed between the heat exchange coil 15 and the steam drum 2 is as follows: the circulation loop includes a first pipeline 21 and a second pipeline 22 connected to the steam drum 2; the first pipeline 21 is used to introduce the water in the steam drum 2 into the heat exchange coil 15, and the second pipeline 22 is used to return the water and steam in the heat exchange coil 15 to the steam drum 2. Specifically:

[0057] One water inlet branch pipeline 23 is connected to the water inlet end of each heat exchange coil 15, and one water return branch pipeline 24 is connected to the water outlet end of each heat exchange coil 15.

[0058] Among them, the water inlet branch pipelines 23 are connected in parallel to the first pipeline 21, that is, one end of the first pipeline 21 is communicated with the bottom of the steam drum 2, the other end is communicated with one end of the water inlet branch pipeline 23, and the other end of the water inlet branch pipeline 23 is communicated with the water inlet end of the heat exchange coil 15.

[0059] The water return branch pipelines 24 are connected in parallel to the second pipeline 22, that is, one end of the second pipeline 22 is communicated with the upper part of the steam drum 2, the other end is communicated with one end of the water return branch pipeline 24, and the other end of the water return branch pipeline 24 is communicated with the water outlet end of the heat exchange coil 15.

[0060] A flow control valve 231 with adjustable flow rate (hereinafter referred to as the control valve 231) is provided on each water inlet branch pipeline 23. The control valve 231 is used to adjust the water flow rate in each water inlet branch pipeline 23, so as to adjust the intake air temperature of the downstream catalytic bed to be between 350 °C and 450 °C; for example, when the intake air temperature is too high, the control valve 231 is opened wider to increase the water flow rate, and vice versa, the control valve 231 is opened smaller to decrease the water flow rate.

[0061] In addition, in this embodiment, the height of the bottom of the steam drum 2 is higher than that of the uppermost heat exchange coil 15, and the vertical distance between the two is between 300 mm and 2000 mm. The purpose is to provide a gravity difference. Under the action of the gravity difference and the pressure in the steam drum 2, the liquid water in the steam drum 2 can flow downward into the heat exchange coil 15 by gravity. The liquid water in the steam drum 2 is heated in the heat exchange coil 15, and the water changes from the liquid phase to steam, the density decreases, the gravity difference increases, and the steam enters the steam drum 2 through the pipeline.

[0062] In this embodiment, the water replenishing system further includes a circulation pump 33. The water inlet end of the circulation pump 33 is communicated with the water replenishing tank 31. The water outlet end of the circulation pump 33 is connected with a water replenishing pipeline 35 and a water outlet pipeline 34. The water replenishing pipeline 35 is communicated with the steam drum 2. The water outlet pipeline 34 is communicated with the water inlet end of the first heat exchanger 32. The water outlet end of the first heat exchanger 32 is communicated with the top of the water replenishing tank 31 through a return water pipeline 36. A second valve 351 is provided on the water replenishing pipeline 35. Of course, a fourth valve 341 can also be provided on the water outlet pipeline 34.

[0063] The second valve 351 can be automatically opened and closed according to the liquid level in the steam drum 2. It is configured that when the liquid level in the steam drum 2 is lower than the set liquid level (the set liquid level here can be understood as the set minimum liquid level), the second valve 351 automatically opens, and at this time, the water in the water replenishing tank 31 is pumped into the steam drum 2 by the circulation pump 33 to replenish water to the steam drum 2. When the liquid level in the steam drum 2 is higher than or equal to the set liquid level (the set liquid level here can be understood as the set maximum liquid level), the second valve 351 automatically closes, and the water replenishment to the steam drum 2 stops, so as to maintain the liquid level in the steam drum 2 within a stable range.

[0064] During the whole process, the circulation pump 33 will also pump the water in the water replenishing tank 31 to circulate between the first heat exchanger 32 and the water replenishing tank 31 in sequence through the water outlet pipeline 34, the first heat exchanger 32, and the return water pipeline 36, so as to heat the water in the water replenishing tank 31 through the first heat exchanger 32.

[0065] In addition, in order to be able to automatically replenish water into the water replenishing tank 31, in this embodiment, the water replenishing system further includes a water injection pipeline 4 connecting the water source for injecting water into the water replenishing tank 31. The water source is mainly used to provide demineralized softened water. A third valve 41 is provided on the water injection pipeline 4. The third valve 41 can be automatically opened and closed according to the liquid level in the water replenishing tank 31. It is configured that when the liquid level in the water replenishing tank 31 is lower than the set liquid level, the third valve 41 opens to inject water into the water replenishing tank 31 through the water injection pipeline 4. When the liquid level in the water replenishing tank 31 is higher than or equal to the set liquid level, the third valve 41 automatically closes, and the water injection pipeline 4 stops replenishing water into the water replenishing tank 31.

[0066] It should be noted that in this embodiment, the detection of liquid level, pressure, and temperature can be respectively carried out by a liquid level sensor, a pressure sensor, and a temperature sensor.

[0067] Embodiment 2

[0068] Based on Embodiment 1, this embodiment provides a catalytic oxidation method for VOCs conversion and removal, which is mainly carried out by using the catalytic oxidation system for VOCs conversion and removal provided in Embodiment 1, and includes the following steps:

[0069] S0. When starting the system for the first time, inject water into the makeup water tank 31 and inject water into the steam drum 2 through the makeup water tank 31; specifically, open the third valve 41 to inject demineralized softened water into the makeup water tank 31, and open the circulating pump 33 to inject demineralized softened water into the steam drum 2.

[0070] S1. Start the system and open the blower 7 to introduce waste gas into the reactor 1.

[0071] S2. Open the preheater 6 to preheat the waste gas, and control the temperature of the waste gas to enter the reactor between 350°C and 450°C.

[0072] S3. The waste gas preheated by the preheater 6 enters the reactor 1 through the air inlet 12 and flows through each catalytic bed 11 in sequence. The waste gas undergoes an oxidation reaction under the catalytic action of the catalyst in the catalytic bed 11, and the waste gas is oxidized to generate carbon dioxide and gaseous water, while releasing reaction heat; the flow rate in the heat exchange coil 15 is controlled by adjusting the flow control valve 231 to adjust the inlet air temperature of the downstream catalytic bed between 350°C and 450°C.

[0073] S4. The purified waste gas flows out from the air outlet 13 and then flows through the first heat exchanger 32 to exchange heat with the water circulating between the makeup water tank 31 and the first heat exchanger 32, realizing the heating of the water in the makeup water tank 31, and the waste gas finally discharges through the chimney 5; when the purified waste gas flows through the second heat exchanger 16, the second heat exchanger 16 transfers the heat to the waste gas before purification.

[0074] S5. When the pressure in the steam drum 2 exceeds the set value (0.1 MPa - 1.0 MPa), the first valve 201 automatically opens, and the steam is output through the steam pipeline 20; when the pressure in the steam drum 2 returns below the set value (including the set value), the first valve 201 automatically closes.

[0075] S6. When the liquid level in the steam drum 2 is lower than the set liquid level, the second valve 351 automatically opens, and the makeup water tank 31 starts to supply water to the steam drum 2 until the liquid level in the steam drum 2 reaches the set liquid level, then the second valve 351 automatically closes and stops supplying water to the steam drum 2.

[0076] For those skilled in the art, it is obvious that the present utility model is not limited to the details of the above-described exemplary embodiments, and the present utility model can be implemented in other specific forms without departing from the spirit or basic characteristics of the present utility model. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-restrictive. The scope of the present utility model is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be embraced within the present utility model.

Claims

1. A catalytic oxidation system for VOCs conversion and removal, characterized in that, It includes a reactor, a steam drum and a make-up water system; the reactor includes an air inlet, an air outlet and a number of catalyst beds arranged at intervals in sequence along the gas flow direction; heat exchange coils are provided between adjacent catalyst beds, and there is a gap between the heat exchange coils and the adjacent catalyst beds; a circulation loop is formed between the heat exchange coils and the steam drum; a preheater is connected upstream of the air inlet; the make-up water system includes a first heat exchanger and a make-up water tank for supplying make-up water to the steam drum, and the water in the make-up water tank can circulate between the make-up water tank and the first heat exchanger; the gas flow discharged from the air outlet is discharged after passing through the first heat exchanger; the steam drum is connected with a steam pipeline for transporting steam and having a first valve.

2. The catalytic oxidation system for VOCs conversion and removal according to claim 1, characterized in that, The make-up water system further includes a circulation pump, the water inlet end of the circulation pump is communicated with the make-up water tank, the water outlet end of the circulation pump is connected with a make-up water pipeline and a water outlet pipeline, the make-up water pipeline is communicated with the steam drum; the water outlet pipeline is communicated with the water inlet end of the first heat exchanger; the water outlet end of the first heat exchanger is communicated with the make-up water tank through a return water pipeline; a second valve is provided on the make-up water pipeline.

3. The catalytic oxidation system for VOCs conversion and removal according to claim 2, wherein The second valve is configured to open when the liquid level in the steam drum is lower than the set liquid level; and close when the liquid level in the steam drum is higher than or equal to the set liquid level.

4. The catalytic oxidation system for VOCs conversion and removal according to claim 2, wherein, The make-up water system further includes a water injection pipeline connected to a water source for injecting water into the make-up water tank; a third valve is provided on the water injection pipeline; the third valve is configured to open to inject water into the make-up water tank through the water injection pipeline when the liquid level in the make-up water tank is lower than the set liquid level; and close when the liquid level in the make-up water tank is higher than or equal to the set liquid level.

5. A catalytic oxidation system for VOCs conversion and removal according to claim 1, characterized in that, The gap between the heat exchange coils and the adjacent catalyst beds is 100 mm - 600 mm.

6. The catalytic oxidation system for VOCs conversion and removal according to claim 1, wherein The circulation loop includes a first pipeline and a second pipeline connected to the steam drum; the water inlet end of the heat exchange coil is connected with a water inlet branch pipeline, and the water outlet end of the heat exchange coil is connected with a return water branch pipeline; each of the water inlet branch pipelines is connected in parallel to the first pipeline; each of the return water branch pipelines is connected in parallel to the second pipeline; control valves with adjustable flow rates are provided on each of the water inlet branch pipelines.

7. The catalytic oxidation system for VOCs conversion and removal according to claim 1, wherein The reactor further includes a second heat exchanger provided upstream of the preheater, and the second heat exchanger is provided between the air outlet and the last catalyst bed; the VOCs waste gas to be treated sequentially passes through the second heat exchanger, the preheater, the air inlet and then enters the reactor.

8. A catalytic oxidation system for VOCs conversion and removal according to claim 1, characterized in that, The catalyst beds are arranged vertically in sequence; the height of the bottom of the steam drum is higher than that of the uppermost heat exchange coil.

9. The catalytic oxidation system for VOCs conversion and removal according to claim 1, characterized in that, The catalyst bed is any one or a combination of several of granular, foam-type, and honeycomb-type catalysts.

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