VOCs waste gas purification treatment method and device

Abstract

The present invention discloses a VOCs waste gas purification treatment method and device, the VOCs waste gas purification treatment method comprises the following steps: passing the VOCs waste gas into a photo-oxidation reactor, performing photolysis and photo-oxidation under the irradiation of light one, and obtaining a mixed gas one containing ozone; passing the mixed gas one into a catalytic ozone oxidation reactor filled with an ozone oxidation catalyst, performing a catalytic ozone oxidation reaction, and obtaining a mixed gas two; and then passing the mixed gas two into a photocatalytic reactor filled with a photocatalyst, and performing a photocatalytic reaction under the irradiation of light two. Through the above method, the treatment efficiency of VOCs waste gas can be improved, the mineralization rate is high, and the energy consumption and cost are low.

Description

Technical Field

[0001] The present invention relates to the technical field of waste gas treatment, and in particular to a method and device for purifying VOCs waste gas. Background Art

[0002] Volatile organic compounds (VOCs) are one of the most important air pollutants to be controlled. Their harmful effects on the human body and environmental damage have attracted widespread attention, and VOC control efforts have been fully implemented. Commonly used VOC control methods include combustion, adsorption, absorption, condensation, plasma, biological, photocatalytic, and ozone catalytic oxidation. Combustion produces secondary pollution; adsorption and absorption require regular replacement of the adsorbent and absorption liquid, resulting in high maintenance costs; condensation cannot treat gaseous pollutants with complex compositions and has high operating costs; plasma consumes a lot of energy, is prone to secondary pollution, and has high operating costs; biological methods require the cultivation of specific microorganisms tailored to the pollutants, making operation cumbersome and difficult to control; and ozone catalytic oxidation requires an ozone generator to produce large amounts of ozone, resulting in high investment costs. However, companies in these industries are generally small and cannot afford to invest heavily in waste gas treatment. Instead, they typically use activated carbon adsorption technology, which, while low in investment, requires regular replacement of the activated carbon, is difficult to maintain, and has high operating costs. Therefore, developing a low-cost VOC treatment technology that is highly efficient for treating difficult-to-degrade waste gases is crucial. Summary of the Invention

[0003] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention provides a VOCs waste gas purification method and device, which can improve the treatment efficiency of VOCs waste gas and have a high mineralization rate.

[0004] The technical solution adopted by the present invention is:

[0005] A first aspect of the present invention provides a method for purifying VOCs waste gas, comprising the following steps:

[0006] S1. Passing VOCs waste gas into a photooxidation reactor, photolyzing and photooxidizing it under the irradiation of light 1 to obtain a mixed gas containing ozone 1;

[0007] S2, passing the ozone-containing mixed gas 1 obtained in step S1 into a catalytic ozone oxidation reactor filled with an ozone oxidation catalyst to perform a catalytic ozone oxidation reaction to obtain a mixed gas 2;

[0008] S3, introducing the mixed gas obtained in step S2 into a photocatalytic reactor filled with photocatalyst to carry out a photocatalytic reaction under the irradiation of light 2.

[0009] According to some embodiments of the present invention, the light 1 is vacuum ultraviolet light, and the light 2 is ultraviolet light; preferably, the light 1 is vacuum ultraviolet light with a wavelength less than or equal to 185 nm; the light 2 is ultraviolet light with a wavelength less than or equal to 254 nm.

[0010] According to some embodiments of the present invention, the light one and the light two are emitted by the same light source. Preferably, the light source is an ultraviolet lamp. In the above manner, the VOCs waste gas can first be subjected to photolysis and photooxidation reactions in a photooxidation reactor using the light one emitted by the light source and having a specific wavelength (generally vacuum ultraviolet light with a wavelength less than or equal to 185 nm), and the O2 in the waste gas is converted into O3 under the action of the light one; in addition, in the photocatalytic reactor, the mixed gas two can further utilize the light two (generally ultraviolet light with a wavelength less than or equal to 254 nm) that is not utilized in the photooxidation reactor to undergo a photocatalytic reaction, and according to the requirements of different reactions for light of different wavelengths, a purification process is set up to make full use of light energy, save energy consumption, reduce treatment costs, and improve the treatment efficiency of waste gas.

[0011] According to some embodiments of the present invention, the light source is a microwave electrodeless ultraviolet lamp, and its operation is controlled by microwave excitation emitted by a microwave emitting device to the microwave electrodeless ultraviolet lamp. The use of a microwave electrodeless ultraviolet lamp has a high removal rate for gaseous pollutants.

[0012] In addition, the photooxidation reactor in step S1 and the photocatalytic reactor in step S3 can be placed in the microwave resonant cavity of a microwave emitting device. The microwaves emitted by the microwave emitting device can then excite and control the emission and operation of the electrodeless ultraviolet lamp while assisting in promoting the reactions in the photooxidation reactor and the photocatalytic reactor. By adding microwaves (electromagnetic waves with a frequency in the range of 300 MHz to 300 GHz), gaseous pollutants can be removed at a lower temperature; the activity of the photocatalyst can be enhanced to a certain extent, thereby improving the removal efficiency of pollutants.

[0013] According to some embodiments of the present invention, in step S2, the ozone oxidation catalyst is selected from at least one of a transition metal oxide and a composite catalyst of a transition metal oxide and a molecular sieve. The transition metal oxide may specifically be at least one of oxides of transition metals such as Mn, Fe, Co, Ni, V, Cu, Ce, and Ag. Preferably, the ozone oxidation catalyst is selected from at least one of MnO2 and a MnO2 / molecular sieve composite catalyst. Further preferably, the ozone oxidation catalyst is a δ-MnO2 / molecular sieve composite catalyst. Specifically, the δ-MnO2 / molecular sieve composite catalyst may be a δ-MnO2 / USY molecular sieve composite catalyst. The composite catalyst may be prepared by the following method: mixing KMnO4 and USY molecular sieve, adding deionized water, and mixing thoroughly; adding an aqueous MnSO4 solution, stirring thoroughly, and then conducting a hydrothermal reaction at a temperature generally between 150°C and 170°C; cooling to room temperature after completion of the reaction, filtering, washing, drying, grinding, and passing through a 40-60 mesh sieve.

[0014] According to some embodiments of the present invention, in step S3, the photocatalyst is selected from at least one of BiVO4, TiO2, and a TiO2 / SiO2 composite catalyst. Preferably, the TiO2 / SiO2 composite catalyst can be prepared by the following method: mixing silica sol and a silane coupling agent, adding sodium hexametaphosphate, stirring, and adjusting the pH to 2-3; then adding titanium dioxide, stirring thoroughly, and then drying, grinding, and passing through a 40-60 mesh sieve.

[0015] According to some embodiments of the present invention, the VOCs waste gas purification method further includes: step S4, passing the gas treated in step S3 into a heated catalytic reactor filled with a thermal catalyst to perform a microwave heating catalytic reaction. Specifically, the thermal catalyst may be a MnO2 catalyst with good heat absorption properties. This step S4 further enhances the VOCs waste gas treatment effect and improves the mineralization rate.

[0016] The second aspect of the present invention provides a VOCs waste gas purification and treatment device, comprising a photooxidation reactor, a catalytic ozone oxidation reactor and a photocatalytic reactor connected in sequence; the photooxidation reactor has a reaction chamber one and an air inlet connected to the reaction chamber one, and an ultraviolet lamp is provided in the reaction chamber one; the catalytic ozone oxidation reactor has a reaction chamber two, and the reaction chamber two is filled with an ozone oxidation catalyst; the photocatalytic reactor has a reaction chamber three and an air outlet connected to the reaction chamber three, and the reaction chamber three is filled with a photocatalyst; the photooxidation reactor has a light-transmitting side wall for separating the reaction chamber one and the reaction chamber three.

[0017] According to some embodiments of the present invention, the ultraviolet lamp is a microwave electrodeless ultraviolet lamp, and the VOCs waste gas purification and treatment device further includes a microwave emitting device for exciting and controlling the operation of the microwave electrodeless ultraviolet lamp.

[0018] According to some embodiments of the present invention, the VOCs waste gas purification treatment device also includes a heating catalytic reactor connected to the gas outlet of the photocatalytic reactor, the heating catalytic reactor has a reaction chamber four and a gas outlet connected to the reaction chamber four, and the reaction chamber four is filled with a thermal catalyst; the microwave emitting device is also used to perform microwave heating on the heating catalytic reactor.

[0019] According to some embodiments of the present invention, a mounting bracket for mounting and supporting the ultraviolet lamp is provided in the reaction chamber.

[0020] According to some embodiments of the present invention, the photo-oxidation reactor is disposed in the photocatalytic reactor, and the sidewall of the photo-oxidation reactor is a light-transmitting sidewall.

[0021] The beneficial effects of the embodiments of the present invention are:

[0022] An embodiment of the present invention provides a method for purifying VOCs waste gas, which sequentially passes the VOCs waste gas into a photooxidation reactor, a catalytic ozone oxidation reactor, and a photocatalytic reactor. First, light one is used to perform photolysis and photooxidation in the photooxidation reactor. During this process, oxygen in the VOCs waste gas generates strong oxidizing free radicals and ozone under the action of light one, forming a mixed gas one containing ozone; then the mixed gas one containing ozone is passed into a catalytic ozone oxidation reactor, and under the action of an ozone oxidation catalyst, the ozone in the mixed gas one is used to perform a catalytic ozone oxidation reaction, thereby degrading small molecular pollutants into harmless molecules such as carbon dioxide and water, thereby forming a mixed gas two; then the mixed gas two is passed into a photocatalytic reactor, and under the action of light two and a photocatalyst, a photocatalytic reaction is performed to further oxidize and degrade pollutants such as toluene in the mixed gas two; through the above method, the synergistic effect of the multiple effects of high-energy light photolysis and photooxidation, catalytic ozone oxidation, and photocatalysis can be efficiently utilized to improve the treatment efficiency of VOCs waste gas, with a high mineralization rate and low energy consumption and cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly describes the drawings required for describing the embodiments.

[0024] Figure 1 This is a schematic structural diagram of an embodiment of a VOCs waste gas purification and treatment device of the present invention;

[0025] Figure 2 yes Figure 1A schematic diagram of the structure of a mounting bracket for mounting a UV lamp in a VOCs waste gas purification and treatment device is shown;

[0026] Figure 3 yes Figure 1 The long-term operation experimental effect diagram of the VOCs waste gas purification device shown;

[0027] Figure 4 yes Figure 1 The toluene desorption amount and CO desorption of the catalyst in situ regeneration after long-term operation of the VOCs waste gas purification device are shown in the figure. x Generation volume change curve;

[0028] Figure 5 yes Figure 1 The figure shows the performance effect of removing toluene after the catalyst is in situ regenerated after long-term operation of the VOCs waste gas purification treatment device. DETAILED DESCRIPTION

[0029] The following will clearly and completely describe the concept and technical effects of the present invention in conjunction with the embodiments to fully understand the purpose, features and effects of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, other embodiments obtained by those skilled in the art without creative work are all within the scope of protection of the present invention.

[0030] See also Figure 1 and Figure 2 , Figure 1 This is a schematic structural diagram of an embodiment of a VOCs waste gas purification and treatment device of the present invention. Figure 2 yes Figure 1 The schematic diagram of the structure of the mounting bracket for mounting the UV lamp in the VOCs waste gas purification device is shown in FIG. Figure 1 and Figure 2 As shown, the VOCs waste gas purification treatment device of this embodiment includes a photooxidation reactor 1, a catalytic ozone oxidation reactor 2, a photocatalytic reactor 3 and a microwave emission device 4 which are connected in sequence.

[0031] The photooxidation reactor 1 has a reaction chamber 1 and an air inlet connected to the reaction chamber 1. An ultraviolet lamp (not shown in the figure) is provided in the reaction chamber 1. In this embodiment, the ultraviolet lamp is specifically a microwave electrodeless ultraviolet lamp with a diameter of 20 mm and a length of 300 mm. Two microwave electrodeless ultraviolet lamp tubes are specifically provided in the reaction chamber 1. In order to facilitate the installation of the microwave electrodeless lamp tubes, a mounting bracket 11 for mounting and supporting the ultraviolet lamp is provided in the reaction chamber 1. In this embodiment, the mounting bracket 11 is specifically as follows: Figure 2As shown, it includes two opposing "8"-shaped mounting plates 111 and support columns 112 disposed between the two mounting plates 111 for connecting and supporting the two mounting plates 111. The two opposing "8"-shaped mounting plates 111 cooperate to form two sets of mounting holes for mounting UV lamps, with a diameter of 21 mm. The ends of the UV lamps are respectively secured to the through holes of the mounting plates 111. The mounting plates 111 and support columns 112 are specifically made of quartz. In other embodiments, the number and shape and size of the UV lamps can be adjusted according to the circumstances, and the mounting bracket 11 can also be designed with other structures.

[0032] Generally speaking, there is a gap between the UV lamp tubes, and between the UV lamp tubes and the photooxidation reactor 1, without contact. Based on this, in this embodiment, the photooxidation reactor 1 is specifically designed as a hollow cylindrical structure with an inner diameter of 50 mm and a length of 350 mm. Furthermore, to facilitate the installation and placement of the UV lamp, the photooxidation reactor 1 has stainless steel adapters at both ends, connecting the inlet and outlet pipes. The inlet and outlet pipes can specifically be made of polytetrafluoroethylene tubes with a diameter of 3 mm. Of course, the structure and size of the photooxidation reactor 1 can be adjusted according to actual conditions.

[0033] The catalytic ozone oxidation reactor 2 comprises a reaction chamber 2 filled with an ozone oxidation catalyst. Specifically, the catalytic ozone oxidation reactor 2 can be a hollow cylindrical structure with an inner diameter of 10 mm and a length of 400 mm. Stainless steel adapters are provided at both ends, and the stainless steel adapters are connected to the inlet and outlet pipes, respectively. Specifically, the inlet and outlet pipes can be made of 3 mm diameter polytetrafluoroethylene tubes.

[0034] The ozone oxidation catalyst is selected from at least one of a transition metal oxide and a composite catalyst of a transition metal oxide and a molecular sieve. The transition metal oxide can specifically be at least one of oxides of transition metals such as Mn, Fe, Co, Ni, V, Cu, Ce, and Ag. The ozone oxidation catalyst is preferably at least one of MnO2 and a MnO2 / molecular sieve composite catalyst. Further preferably, the ozone oxidation catalyst is a δ-MnO2 / molecular sieve composite catalyst. The ozone oxidation catalyst used in this embodiment is a δ-MnO2 / molecular sieve composite catalyst, specifically a δ-MnO2 / USY molecular sieve composite catalyst, which can be prepared by a preparation method comprising the following steps: weighing 0.3 g KMnO4 and 1.7 g USY molecular sieve and placing them into a 250 mL beaker ①, adding 40 mL deionized water, and magnetically stirring for 30 minutes, then weighing 0.055 g MnSO4·H2O and placing it into a 100 mL beaker, adding 40 mL deionized water, and slowly pouring it into the beaker ①, and magnetically stirring for another 30 minutes. The stirred solution is transferred to a 100 mL Teflon reactor, hydrothermally reacted at 160°C for 24 hours, naturally cooled to room temperature, filtered, washed, dried at 80°C for 12 hours, and ground and sieved to obtain solid particles of 40 to 60 mesh.

[0035] The photocatalytic reactor 3 has a reaction chamber 3 and an air outlet connected to the reaction chamber 3. The reaction chamber 3 is filled with a photocatalyst. The photocatalyst can be selected from at least one of BiVO4, TiO2, and a TiO2 / SiO2 composite catalyst, preferably a TiO2 / SiO2 composite catalyst. In this embodiment, the photocatalyst is specifically a TiO2 / SiO2 composite catalyst, which can be prepared by a preparation method comprising the following steps: weighing 25g of silica sol and placing it in a 250mL beaker, measuring 3mL of KH-570 and adding it to the beaker, stirring for 10 minutes, weighing 0.2g of sodium hexametaphosphate and adding it to the beaker, stirring for 5 minutes, adjusting the pH to 2, weighing 10g of P25 and adding it to the beaker, magnetically stirring for 1 hour, drying at 80°C for 12 hours, grinding and sieving to obtain solid particles of 40-60 mesh.

[0036] The photooxidation reactor 1 has a light-transmitting side wall for separating the reaction chamber 1 and the reaction chamber 3. In this embodiment, the photooxidation reactor 1 is arranged in the photocatalytic reactor 3, and the side wall of the photooxidation reactor 1 is a light-transmitting side wall, so that the VOCs waste gas in the photooxidation reactor 1 can first be photolyzed and photooxidized by the high-energy vacuum ultraviolet light 1 (such as vacuum ultraviolet light with a wavelength less than or equal to 185nm) emitted by the microwave electrodeless ultraviolet lamp. In this process, the oxygen in the gas can be converted into free radicals and ozone with strong oxidizing properties; and the unused ultraviolet light 2 (including ultraviolet light with a wavelength less than or equal to 254nm) can be irradiated into the reaction chamber 3 of the photocatalytic reactor 3 through the light-transmitting side wall of the photooxidation reactor 1, so as to promote the waste gas to undergo a photocatalytic reaction under the action of ultraviolet light 2 and the photocatalyst, and further oxidize and degrade pollutants such as toluene in the waste gas. Through the above structural setting, it is possible to improve the waste gas treatment capacity and efficiency while fully utilizing light energy, saving energy consumption, and reducing treatment costs.

[0037] Of course, the relative positions of the photooxidation reactor 1 and the photocatalytic reactor 3, as well as the structure of the side walls, can also be adjusted according to actual conditions. For example, the photooxidation reactor 1 and the photocatalytic reactor 3 can be configured as hollow square cylindrical structures, arranged side by side, and the reaction chamber 1 of the photooxidation reactor 1 and the reaction chamber 3 of the photocatalytic reactor 3 are separated by a transparent side wall, so that unused ultraviolet light in the photooxidation reactor 1 can be irradiated into the photocatalytic reactor 3 through the transparent side wall for further utilization.

[0038] In addition, the microwave emitting device 4 is mainly used to control the operation of the microwave electrodeless ultraviolet lamp by emitting microwave excitation. At the same time, the emitted microwaves can also enhance the activity of the photocatalyst filled in the reaction cavity 3 and improve the removal efficiency of pollutants.

[0039] In other embodiments, the VOCs waste gas purification device, based on the above structure, may further include a heating catalytic reactor connected to the gas outlet of the photocatalytic reactor. The heating catalytic reactor has a reaction chamber 4 and a gas outlet connected to the reaction chamber 4. The reaction chamber is filled with a thermal catalyst. The microwave emitting device 4 may also be used to perform microwave heating on the photocatalytic reactor. The configuration of the heating catalytic reactor can further ensure treatment capacity and treatment effect.

[0040] The VOCs waste gas purification treatment device of this embodiment utilizes the synergistic effects of high-energy ultraviolet light photolysis and photooxidation, catalytic ozone oxidation, and photocatalysis to purify VOCs waste gas. The treatment process specifically includes the following steps:

[0041] S1. Start the microwave emitting device 4 to emit microwaves to excite the microwave electrodeless ultraviolet lamp to move, and control the microwave power to excite the microwave electrodeless ultraviolet lamp to emit mixed light mainly composed of 185nm vacuum ultraviolet light and 254nm ultraviolet light.

[0042] S2. The VOCs waste gas containing toluene is introduced into the reaction chamber 1 of the photooxidation reactor 1 from the air inlet on the photooxidation reactor 1, and is photolyzed and photooxidized under the action of high-energy vacuum ultraviolet light with a wavelength less than or equal to 185nm, and is converted into small molecular organic substances such as aldehydes, ketones, acids or esters by chain breaking or ring opening, or is directly mineralized into inorganic substances such as CO2 and H2O; at the same time, O2 in the VOCs waste gas produces strong oxidizing free radicals and ozone (O3) under the action of high-energy ultraviolet light with a wavelength less than or equal to 185nm, forming a mixed gas containing ozone.

[0043] S3. Passing the mixed gas 1 obtained in step S2 into reaction chamber 2 of a catalytic ozone oxidation reactor 2 filled with a δ-MnO2 / USY molecular sieve ozone oxidation catalyst to perform a catalytic ozone oxidation reaction to obtain mixed gas 2. This step simultaneously removes ozone and utilizes ozone to further decompose pollutants in the VOCs waste gas through catalytic ozone oxidation, thereby achieving waste gas treatment while fully utilizing resources and meeting environmental protection requirements.

[0044] S4. The mixed gas 2 obtained in step S3 is introduced into the reaction chamber 3 of the photocatalytic reactor 3 filled with TiO2 / SiO2 photocatalyst. The ultraviolet light with a wavelength less than or equal to 254nm, which is emitted by the microwave electrodeless ultraviolet lamp and not utilized in the photooxidation reactor 1, is irradiated into the reaction chamber 3 of the photocatalytic reactor 3 through the light-transmitting side wall of the photooxidation reactor 1. The mixed gas 2 undergoes a photocatalytic reaction under the action of the photocatalyst and the ultraviolet light less than or equal to 254nm, thereby further purifying the residual pollutants. At the same time, the microwaves emitted by the microwave emitting device 4 can also enhance the activity of the photocatalyst and improve the removal efficiency of the pollutants. The treated gas is then discharged from the gas outlet of the photocatalytic reactor 3.

[0045] exist Figure 1 In the VOCs waste gas purification treatment device shown, a microwave electrodeless ultraviolet lamp and a microwave emitting device are used to provide ultraviolet light for the reaction treatment process. In other embodiments, the microwave emitting device can be eliminated, and the ultraviolet lamp in the photooxidation reactor can be a conventional ultraviolet lamp to provide ultraviolet light of the required wavelength, including vacuum ultraviolet light with a wavelength of ≤185nm and ultraviolet light with a wavelength of ≤254nm. The purification treatment effect of the structure is similar to that of the conventional ultraviolet lamp. Figure 1The method for purifying VOCs waste gas by the VOCs waste gas purification treatment device shown is similar, including: passing the VOCs waste gas into a photooxidation reactor, photolyzing and photooxidizing it under the irradiation of vacuum ultraviolet light with a wavelength less than or equal to 185nm, to obtain a mixed gas 1 containing ozone; passing the mixed gas 1 into a catalytic ozone oxidation reactor filled with an ozone oxidation catalyst, carrying out a catalytic ozone oxidation reaction, to obtain a mixed gas 2; and then passing the mixed gas 2 into a photocatalytic reactor filled with a photocatalyst, carrying out a photocatalytic reaction under the irradiation of ultraviolet light with a wavelength less than or equal to 254nm.

[0046] In the above embodiments, by efficiently utilizing the synergistic effects of high-energy ultraviolet photolysis and photooxidation, catalytic ozone oxidation and photocatalytic multiple effects, the removal capacity and treatment efficiency of VOCs waste gas can be improved, the mineralization rate is high and the cost is low.

[0047] If the VOCs waste gas purification treatment device that also includes a heating catalytic reactor is used to perform waste gas purification treatment, based on the above treatment process, the gas generated by the VOCs waste gas after being treated in the above steps S1 to S4 enters the heating catalytic reactor, and under the action of the microwaves emitted by the microwave emitting device 4, a microwave heating catalytic reaction is carried out, and the treated gas is then discharged from the gas outlet on the heating catalytic reactor. Through the above treatment, the treatment effect of the waste gas can be further guaranteed and complete mineralization can be achieved. In order to save energy consumption, the opening of the heating catalytic reactor can be controlled according to the required waste gas treatment intensity. If the high-energy ultraviolet light photolysis and photooxidation, catalytic ozone oxidation and photocatalytic process can achieve complete mineralization, there is no need to start the heating catalytic reactor. Specifically, the connection between the heating catalytic reactor and the gas outlet of the photocatalytic reactor can be disconnected so that the treated gas is discharged through the gas outlet of the photocatalytic reactor; and if the previous treatment is incomplete, the heating catalytic reactor is restarted.

[0048] In order to further verify the purification effect of the VOCs waste gas purification treatment device and the corresponding purification treatment method of the present invention, a series of application effect experiments were carried out, including: Figure 1 The VOCs waste gas purification treatment device shown in the figure purifies the waste gas according to the photooxidation-catalytic ozone oxidation-photocatalytic process as experimental group 1 and experimental group 2; Figure 1 The VOCs waste gas purification device shown in the figure cancels the photocatalytic reaction in the photocatalytic reactor, and performs waste gas purification according to the photooxidation-catalytic ozone oxidation process, which is used as the comparison group 1, including the comparison group 11 and the comparison group 12. The microwave power of the comparison group 11 and the comparison group 12 is different; Figure 1Based on the VOCs waste gas purification treatment device shown, the catalytic ozone oxidation reaction in the catalytic ozone oxidation reactor is cancelled, and the waste gas purification treatment is carried out according to the photooxidation-photocatalysis process, which is used as the comparison group 2, including the comparison group 21 and the comparison group 22. The microwave power of the comparison group 21 and the comparison group 22 is different.

[0049] By testing the toluene concentration in the exhaust gas before and after purification treatment in each group, the CO concentration and CO2 concentration in the purified gas, and calculating the degradation rate and mineralization rate of toluene according to the following formula, the removal effect of toluene by each process was evaluated.

[0050] (1) Degradation rate of toluene:

[0051]

[0052] Where, c(C7H8) in ——Concentration of toluene before purification, ppm;

[0053] c(C7H8) out ——Concentration of toluene after purification, ppm.

[0054] (2) Mineralization rate of toluene:

[0055]

[0056] Where c(CO) out ——CO concentration in the gas after purification, ppm;

[0057] c(CO2) out ——CO2 concentration in the gas after purification, ppm;

[0058] c(C7H8) in ——Concentration of toluene before purification, ppm.

[0059] The above method was used to test the exhaust gas purification effect, and the results are shown in Table 1 below:

[0060] Table 1 Test results of exhaust gas purification treatment effect

[0061]

[0062] It can be seen from Table 1 above that compared with the photooxidation-catalytic ozone oxidation process of comparison group 1 and the photooxidation-photocatalytic process of comparison group 2, the experimental group treatment process (photooxidation-catalytic ozone oxidation-photocatalytic process) is used to treat VOCs waste gas, which has high treatment efficiency and high mineralization rate.

[0063] In addition, the inventors also used photooxidation process, catalytic ozone oxidation process, photocatalytic process, photooxidation-catalytic ozone oxidation process, photooxidation-photocatalytic process, photooxidation-catalytic ozone oxidation-photocatalytic process to purify the waste gas. Figure 1 The VOCs waste gas purification device shown above was used to start the corresponding reactor according to the specific process. The toluene degradation and mineralization rates were then tested using the waste gas purification effectiveness testing method described above. After the reaction, the residual gas products were passed through a GC-MS (gas chromatography-mass spectrometry) to measure the reaction products. Initial waste gas parameters included: a toluene concentration of 20 ppm, a gas flow rate of 200 mL / min, an oxygen content of 21%, and a relative humidity of 70%. The degradation and mineralization test results are shown in Table 2 below, and the residual gas products are shown in Table 3 below.

[0064] Table 2 Effects of waste gas purification by different treatment processes

[0065]

[0066] Table 3 Relative proportion of gas residual products after waste gas purification by different treatment processes

[0067]

[0068]

[0069] Testing and Table 3 show that, under the same reaction conditions, a single microwave-triggered electrodeless UV lamp photooxidized toluene-containing VOCs waste gas, resulting in a toluene mineralization rate of only 31.4%, with residual ozone remaining at the outlet. Compared to single processes, the combined photooxidation-catalytic ozone oxidation and photooxidation-photocatalysis processes exhibited synergistic effects. The three-process combination of photooxidation-catalytic ozone oxidation-photocatalysis, by reusing byproduct ozone and the less effective UV light (generally with a wavelength of 254 nm or less), increased toluene mineralization to 92.8%, improving purification efficiency while ensuring no ozone leakage. The reason the three-process combination failed to achieve the expected mineralization rate compared to the sum of the three individual processes is primarily due to the complete ozone purification in the catalytic ozone oxidation stage, eliminating the synergistic contribution of ozone in the photocatalytic oxidation stage. However, combined with the results in Table 1, it is clear that appropriate microwave power adjustment can ensure complete toluene mineralization at the outlet.

[0070] Tables 3 and 4 show that the byproducts generated by the photooxidation process in Group A's waste gas are numerous benzene series, with benzaldehyde and benzoic acid comprising the largest proportions, 13.8% and 40.6%, respectively. There are also numerous chain organic compounds, with acetic acid and formic acid comprising the largest proportions, 19.9% ​​and 9.3%, respectively. In Group B, the organic byproducts generated by the catalytic ozone oxidation process are all benzene series, with benzene comprising the largest proportion. In Group C, the organic byproducts generated by the photocatalytic process are primarily benzene series, with formic acid being the only chain organic compound, with benzoic acid comprising 83.5%. In Group D, the organic byproducts generated by the photooxidation-catalytic ozone oxidation process include benzene series and long-chain organic compounds. Benzaldehyde, benzoic acid, and benzene comprise the largest proportions, 24.2%, 11.7%, and 22.7%, respectively. The organic byproducts generated by the photooxidation-photocatalytic process in Group E's waste gas were all benzene series, with benzoic acid and benzene accounting for the largest proportions, at 64.0% and 22.8%, respectively. The organic byproducts generated by the photooxidation-catalytic ozone oxidation-photocatalytic process in Group F's waste gas were primarily benzene series, with a small amount of formic acid, with benzoic acid accounting for the largest proportion, at 72.6%. This demonstrates that the mineralization rate must be maintained during the degradation process of VOCs waste gas; otherwise, it may cause even more serious pollution and harm.

[0071] In addition, in order to investigate the poisoning and regeneration of the device, we studied the poisoning and regeneration of the composite process under low mineralization rate. Figure 1 The device shown in the figure was subjected to a photooxidation-catalytic ozone oxidation-photocatalytic process. A long-term operation experiment was conducted under the reaction conditions of microwave power 147.75W, relative humidity 70%, oxygen content 21%, gas flow rate 200mL / min, initial toluene concentration 20ppm, and toluene mineralization rate 70.3% to test the toluene removal effect. The results are shown in the figure. Figure 3 shown.

[0072] Depend on Figure 3 It can be seen that with the extension of the operation time, the toluene degradation rate decreased slightly, but still remained above 96%, while the toluene mineralization rate gradually decreased from the initial 70.3% to 45.6% after 50 hours of operation. After 50 hours of operation, the toluene was stopped and 200 mL / min of dry air was introduced. The microwave electrodeless lamp was turned on to perform in-situ regeneration of the catalyst. The toluene desorption amount of the catalyst in-situ regeneration and the CO x (including CO and CO2) production, the results are as follows Figure 4 shown.

[0073] Depend on Figure 4 It can be seen that there is a small amount of toluene at the outlet in the first 60 minutes, and the toluene concentration at the outlet is almost zero after 60 minutes. x The output increased rapidly within 20 min and then decreased gradually.

[0074] In order to investigate the performance of the system in degrading toluene after regeneration, the experiment was further conducted under the conditions of relative humidity 70%, oxygen content 21%, microwave power 147.75W, gas flow rate 200mL / min, and initial toluene concentration 20ppm. The experimental results are shown in the figure below. Figure 5 shown.

[0075] Depend on Figure 5 It can be seen that after regeneration, the degradation rate of toluene by the system remained stable, and the toluene mineralization rate dropped from 70.3% to 67.4%, proving that the regeneration effect of the system was good.

Claims

1. A VOCs waste gas purification method, characterized in that: A VOCs waste gas purification treatment device is used to purify VOCs waste gas, and the VOCs waste gas purification treatment device includes a photo-oxidation reactor, a catalytic ozone oxidation reactor and a photocatalytic reactor connected in sequence; the photo-oxidation reactor has a reaction chamber one and a first air inlet and a first air outlet connected to the reaction chamber one, and an ultraviolet lamp is arranged in the reaction chamber one; the catalytic ozone oxidation reactor has a reaction chamber two and a second air inlet and a second air outlet connected to the reaction chamber two, the reaction chamber two is filled with an ozone oxidation catalyst, and the second air inlet is connected to the first air outlet; the photocatalytic reactor has a reaction chamber three and a third air outlet and a third air inlet connected to the reaction chamber three, the reaction chamber three is filled with a photocatalyst, and the third air inlet is connected to the second air outlet; the photo-oxidation reactor has a light-transmitting side wall for separating the reaction chamber one and the reaction chamber three; The ultraviolet lamp is a microwave electrodeless ultraviolet lamp, and the VOCs waste gas purification treatment device also includes a microwave emitting device for exciting and controlling the operation of the microwave electrodeless ultraviolet lamp; the microwave emitting device includes a microwave resonant cavity, and the photooxidation reactor and the photocatalytic reactor are both arranged in the microwave resonant cavity; The VOCs waste gas purification treatment method comprises the following steps: S0, start the microwave transmitting device, emit microwaves through the microwave transmitting device to excite the microwave electrodeless ultraviolet lamp to operate, and control the microwave power to excite the microwave electrodeless ultraviolet lamp to emit mixed light including light one and light two, wherein the light one is vacuum ultraviolet light with a wavelength less than or equal to 185nm, and the light two is ultraviolet light with a wavelength less than or equal to 254nm; S1. Passing VOCs waste gas into a photo-oxidation reactor, photolyzing and photo-oxidizing the waste gas under the assistance of light irradiation and microwaves emitted by a microwave emitting device, to obtain a mixed gas containing ozone; S2, passing the ozone-containing mixed gas 1 obtained in step S1 into a catalytic ozone oxidation reactor filled with an ozone oxidation catalyst to perform a catalytic ozone oxidation reaction to obtain a mixed gas 2; S3, introducing the mixed gas obtained in step S2 into a photocatalytic reactor filled with a photocatalyst, and performing a photocatalytic reaction under the assistance of light irradiation and microwaves emitted by a microwave emitting device.

2. The VOCs waste gas purification method according to claim 1, characterized in that: In step S2, the ozone oxidation catalyst is selected from at least one of a transition metal oxide and a composite catalyst of a transition metal oxide and a molecular sieve.

3. The VOCs waste gas purification method according to claim 2, characterized in that: In step S2, the ozone oxidation catalyst is selected from at least one of MnO2 and MnO2 / molecular sieve composite catalyst.

4. The VOCs waste gas purification method according to claim 1, characterized in that: In step S3, the photocatalyst is selected from at least one of BiVO4, TiO2, and TiO2 / SiO2 composite catalyst.

5. The VOCs waste gas purification method according to any one of claims 1 to 4, further comprising: Step S4, passing the gas treated in step S3 into a heating catalytic reactor filled with a thermal catalyst to perform a microwave heating catalytic reaction under the action of microwaves.

6. A VOCs waste gas purification device, characterized in that: It comprises a photo-oxidation reactor, a catalytic ozone oxidation reactor and a photocatalytic reactor which are connected in sequence; the photo-oxidation reactor comprises a reaction chamber 1 and a first air inlet and a first air outlet connected to the reaction chamber 1, and an ultraviolet lamp is arranged in the reaction chamber 1; the catalytic ozone oxidation reactor comprises a reaction chamber 2 and a second air inlet and a second air outlet connected to the reaction chamber 2, the reaction chamber 2 is filled with an ozone oxidation catalyst, and the second air inlet is connected to the first air outlet; the photocatalytic reactor comprises a reaction chamber 3 and a third air outlet and a third air inlet connected to the reaction chamber 3, the reaction chamber 3 is filled with a photocatalyst, and the third air inlet is connected to the second air outlet; the photo-oxidation reactor comprises a light-transmitting side wall for separating the reaction chamber 1 and the reaction chamber 3; The ultraviolet lamp is a microwave electrodeless ultraviolet lamp, which is configured to emit a mixed light including light one and light two, wherein light one is vacuum ultraviolet light with a wavelength less than or equal to 185nm, and light two is ultraviolet light with a wavelength less than or equal to 254nm; the VOCs waste gas purification treatment device also includes a microwave emitting device for exciting and controlling the operation of the microwave electrodeless ultraviolet lamp; the microwave emitting device includes a microwave resonant cavity, and the photooxidation reactor and the photocatalytic reactor are both arranged in the microwave resonant cavity.

7. The VOCs waste gas purification treatment device according to claim 6, characterized in that: The VOCs waste gas purification treatment device also includes a heating catalytic reactor connected to the third air outlet of the photocatalytic reactor, the heating catalytic reactor has a reaction chamber four and an air outlet connected to the reaction chamber four, and the reaction chamber four is filled with a thermal catalyst; the microwave emitting device is also used to perform microwave heating on the photocatalytic reactor.

8. The VOCs waste gas purification treatment device according to claim 7, characterized in that: A mounting bracket for mounting and supporting the ultraviolet lamp is arranged in the reaction chamber 1.

Images