Treatment process and system for nitrogen oxide tail gas in photovoltaic cell production process

Abstract

The invention discloses a treatment process and system for nitrogen oxide tail gas in the production process of photovoltaic cells, and the system comprises a reactor which is provided with a gas inlet and distribution port and a gas outlet, and the gas inlet and distribution port is provided with a gas inlet fan; the two catalytic plates are arranged in the reactor in a spaced mode, the interior of each catalytic plate is hollow, the outer wall of each catalytic plate is transparent, each catalytic plate is of a porous structure, the interior of each catalytic plate is filled with a Fe modified TiO2 catalyst, and an illumination catalytic chamber is defined by the two catalytic plates and the inner wall of the reactor; and the light source is an ultraviolet lamp or a visible light lamp and is arranged in the illumination catalysis chamber. According to the process, the single-chamber photocatalytic reactor serves as a core, the Fe modified TiO2 catalyst is combined, nitrogen oxide in waste gas can be efficiently removed, and the whole process is simple, easy to operate, low in operation cost, energy-saving, environmentally friendly and wide in market application prospect.

Description

Technical Field

[0001] The present invention relates to the field of waste gas treatment, and in particular to a treatment process and system for nitrogen oxide tail gas in the production process of photovoltaic cells. Background Art

[0002] Photovoltaic power generation, as a new energy power generation technology, is widely recognized by the society for its green and clean characteristics. In order to reduce the cost of electricity, achieve grid parity, and meet the needs of global energy transformation, solar cell technology and market have been developing rapidly. At the same time, a large amount of exhaust gas is generated during the production of solar cells, and nitrogen oxides (NO x ) waste gas, nitrogen oxide waste gas is an important source of air pollution, not only has a strong toxic effect on the lungs, heart and other organs of human and animal, but also can form acid mist, acid rain and photochemical smog, destroy the ozone layer, nitrogen oxide is one of the main sources of air pollution, commonly known as nitrogen oxides (NO x ) include N2O, NO, NO2, N2O3, N2O4, N2O5, etc. Among them, NO and NO2 are the main pollutants of the atmosphere. In addition, N2O is also an air pollutant, which is particularly polluting to the upper atmosphere. x Although only naturally occurring NO x However, due to the high concentration of emissions and concentrated locations, the harm is very serious. x The hazards caused by the emission of NO to the natural environment and human production and life mainly include: x Toxic to humans; harmful to plants; NO x It is the main cause of acid rain and acid fog; NO x It forms chemical smog with hydrocarbons, causing secondary pollution; N2O participates in the destruction of the ozone layer, causing great harm to the ecological environment and human production and life, so NO x Waste gas treatment has become an important part of environmental protection and a primary condition for industrial production and operation. At present, a certain concentration of nitrogen oxides (NO x ), mainly from cleaning (nitric acid), hole expansion (nitric acid, hydrofluoric acid), pickling (nitric acid, hydrofluoric acid) and other processes, the main purpose of which is to treat the surface of the silicon wafer to meet the requirements of subsequent treatment. Since nitric acid and hydrofluoric acid are required in the cleaning, hole expansion and pickling of silicon wafers, NO, NO2, N2O, N2O3, N2O4 and other waste gases will be generated in the above-mentioned treatment processes. Due to the complex composition of the waste gas, it is collectively referred to as nitrogen oxides NO x .

[0003] Traditional denitrification technologies such as adsorption, selective catalytic reduction (SCR) and non-selective catalytic reduction (SNCR) generally have secondary pollution problems such as ammonia escape, which has caused considerable trouble for ecological environment governance. At the same time, these technologies require high energy consumption, so the cleaner, more environmentally friendly and energy-saving photocatalytic oxidation denitrification technology has a better development trend in the future.

[0004] Yes x Another effective treatment method is photocatalytic oxidation technology, which is cleaner, more environmentally friendly, and energy-saving, and has better oxidation capacity than traditional denitrification technology. The reaction is driven by sunlight irradiating the catalyst, and the reaction conditions are relatively mild. The choice of catalyst in this technology is crucial. Titanium dioxide is a low-cost, easy-to-prepare, and chemically stable catalyst suitable for removing a series of VOCs, especially in the photocatalytic oxidation of VOCs. Titanium dioxide can degrade volatile organic compounds into CO, H2O, etc. under ultraviolet light. The photocatalytic oxidation of titanium dioxide occurs under low temperature conditions and is economical.

[0005] However, TiO2 also has some problems due to its own properties. Due to its wide bandgap (3.2eV), it has a better absorption effect on ultraviolet light below 380nm, and low utilization rate of visible light above 400nm. In addition, there is the problem of too fast recombination rate of photogenerated electron-hole pairs. These problems also restrict the practical application of TiO2.

[0006] Therefore, it is necessary to improve the existing technology to provide a more reliable solution. Summary of the invention

[0007] The technical problem to be solved by the present invention is to provide a process and system for treating nitrogen oxide tail gas in the production process of photovoltaic cells in view of the deficiencies in the above-mentioned prior art.

[0008] In order to solve the above technical problems, the technical solution adopted by the present invention is as follows: In a first aspect of the present invention, a system for treating nitrogen oxide tail gas in the production process of photovoltaic cells is provided, comprising:

[0009] A reactor having an air inlet and an air outlet, wherein the air inlet is provided with an air intake fan;

[0010] Two catalytic plates are arranged in the reactor at intervals, the catalytic plates are hollow inside, transparent outside and have a porous structure, the catalytic plates are filled with Fe-modified TiO2 catalyst, and a light catalytic chamber is formed between the two catalytic plates and the inner wall of the reactor;

[0011] A light source, which is an ultraviolet lamp or a visible light lamp, is arranged in the photocatalytic chamber;

[0012] Under the action of the air intake fan, the exhaust gas to be treated enters the reactor from the air intake port, the exhaust gas contacts the Fe-modified TiO2 catalyst in the catalytic plate, is reduced under the illumination of the light source, and the treated exhaust gas is discharged through the outlet.

[0013] Preferably, the Fe-modified TiO2 catalyst is prepared by the following method:

[0014] 1) Add Fe3O4 and polyvinyl pyrrolidone into anhydrous ethanol, disperse by ultrasonication, drop butyl titanate into the mixture under stirring, mix well, and obtain solution A;

[0015] 2) Mix deionized water, glacial acetic acid and anhydrous ethanol to obtain solution B;

[0016] 3) Adding the B solution to the A solution under stirring, pouring the resulting mixture into a reaction vessel, and reacting under heating alone or heating and microwave assistance;

[0017] 4) After the reaction is complete, cool to room temperature, pour off the supernatant, add ethanol to the remaining solid, wash with alcohol and stir;

[0018] 5) Centrifuging the alcohol-washed solution, drying and grinding the solid product obtained after centrifugation to obtain the Fe-modified TiO2 catalyst.

[0019] Preferably, the Fe-modified TiO2 catalyst is prepared by the following method:

[0020] 1) Weigh 1.3-5.5 g of Fe3O4 and 0.025-0.1 g of polyvinyl pyrrolidone, add them into 20-80 mL of anhydrous ethanol, and ultrasonically disperse them for 10-40 min. Then, drop 8.5-34 ml of butyl titanate under stirring, and mix well to obtain solution A;

[0021] 2) Mix 2.5-10 mL of deionized water, 2.5-10 mL of glacial acetic acid and 20-80 mL of anhydrous ethanol to obtain solution B;

[0022] 3) Adding the B solution to the A solution under stirring, pouring the resulting mixture into a reaction kettle, and reacting under the following conditions: reacting at 160-200° C. for 4-16 hours, or reacting under the microwave at 160-200° C. and 250-1000W for 1-4 hours;

[0023] 4) After the reaction is complete, cool to room temperature, pour off the supernatant, add ethanol to the remaining solid, wash with alcohol and stir at 50-70°C for 1-4h;

[0024] 5) The alcohol-washed solution is centrifuged at a speed of 1750-7000 r / min for 5-20 min, and the solid product obtained after centrifugation is dried at 70-90° C. for 4-16 h and ground to obtain the Fe-modified TiO2 catalyst.

[0025] Preferably, the Fe-modified TiO2 catalyst is prepared by the following method:

[0026] 1) Weigh 2.7 g of Fe3O4 and 0.05 g of polyvinyl pyrrolidone, add them into 40 mL of anhydrous ethanol, disperse them by ultrasonic for 20 min, add 17 ml of butyl titanate dropwise under stirring, mix well, and obtain solution A;

[0027] 2) Mix 5 mL of deionized water, 5 mL of glacial acetic acid and 40 mL of anhydrous ethanol to obtain solution B;

[0028] 3) Add solution B to solution A under stirring, pour the resulting mixture into a reactor, and react at 180°C for 8 hours;

[0029] 4) After the reaction is complete, cool to room temperature, discard the supernatant, add ethanol to the remaining solid, wash with alcohol and stir at 60°C for 2h;

[0030] 5) The alcohol-washed solution was centrifuged at a speed of 3500 r / min for 10 min, and the solid product obtained after centrifugation was dried at 80° C. for 8 h and ground to obtain the Fe-modified TiO2 catalyst.

[0031] Preferably, the Fe-modified TiO2 catalyst is prepared by the following method:

[0032] 1) Weigh 2.7 g of Fe3O4 and 0.05 g of polyvinyl pyrrolidone, add them into 40 mL of anhydrous ethanol, disperse them by ultrasonic for 20 min, add 17 ml of butyl titanate dropwise under stirring, mix well, and obtain solution A;

[0033] 2) Mix 5 mL of deionized water, 5 mL of glacial acetic acid and 40 mL of anhydrous ethanol to obtain solution B;

[0034] 3) Add solution B to solution A under stirring, pour the resulting mixture into a reaction kettle, and react under microwave at 180°C and 500W for 2h;

[0035] 4) After the reaction is complete, cool to room temperature, pour off the supernatant, add ethanol to the remaining solid, wash with alcohol and stir at 60°C for 2h;

[0036] 5) The alcohol-washed solution was centrifuged at a speed of 3500 r / min for 10 min, and the solid product obtained after centrifugation was dried at 80° C. for 8 h and ground to obtain the Fe-modified TiO2 catalyst.

[0037] Preferably, the system further comprises:

[0038] A gas storage tank for caching waste gas to be treated, which is connected to the air inlet of the reactor through an air inlet pipeline, and a tail gas absorption bottle, which is connected to the air outlet of the reactor through an exhaust pipeline.

[0039] Preferably, the gas storage tank is provided with a first valve, and the air intake pipe is provided with a second valve and a flow meter.

[0040] Preferably, a third valve and a flue gas analyzer are provided on the exhaust duct.

[0041] Preferably, the ultraviolet lamp is an 18W mercury lamp with a main wavelength of 254nm, and the visible lamp is a 35W incandescent lamp.

[0042] In a second aspect of the present invention, a process for treating nitrogen oxide tail gas during the production of photovoltaic cells is provided, wherein the system as described above is used to purify the tail gas containing nitrogen oxides generated during the production of photovoltaic cells, and the method comprises the following steps:

[0043] S1. collecting the tail gas containing nitrogen oxides generated in the production process of photovoltaic cells through the gas storage tank;

[0044] S2, close the third valve, open the first valve, the second valve, the air intake fan and the light source, pass the tail gas in the gas storage tank into the reactor, and keep it for 2-30 minutes after filling the reactor;

[0045] S3. Open the third valve to allow the tail gas discharged from the reactor to enter the tail gas absorption bottle, and then be discharged after being absorbed by the absorbent in the bottle. By adjusting the first valve, the flow rate detected by the flow meter reaches the designed value, thereby continuously treating the tail gas in the gas storage tank.

[0046] The beneficial effects of the present invention are:

[0047] The present invention provides a treatment process and system for nitrogen oxide tail gas in the production process of photovoltaic cells. The present invention uses a single-chamber photocatalytic reactor as the core and combines a Fe-modified TiO2 catalyst to achieve efficient removal of nitrogen oxides in exhaust gas. The overall process is simple, easy to operate, low in operating cost, energy-saving and environmentally friendly, and has broad market application prospects.

[0048] The present invention adopts Fe doping to modify TiO2 to improve the photocatalytic denitrification effect. 3+ It can play the following roles: (1) Forming a capture center with a valence higher than Ti 4+ The metal ions capture electrons and have a lower valence than Ti 4+ The metal ions capture holes and suppress the hole h +and electronic - (2) forming doping energy levels so that photons with lower energy can also excite electrons and holes, thus improving the photon utilization rate; (3) extending the lifetime of electrons and holes. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 It is a structural schematic diagram of a system for treating nitrogen oxide tail gas in a photovoltaic cell production process of the present invention;

[0050] Figure 2 The NO2 removal test results in Test Example 1;

[0051] Figure 3 The NO2 removal test results in Test Example 2;

[0052] Figure 4 This is the NO2 removal test result in Test Example 3.

[0053] Description of reference numerals:

[0054] 1—reactor; 11—air inlet and air distribution port; 12—air outlet; 13—air inlet fan;

[0055] 2—catalytic plate; 21—Fe-modified TiO2 catalyst; 22—photocatalytic chamber;

[0056] 3—Light source;

[0057] 4—gas storage tank; 41—first valve;

[0058] 5—intake pipe; 51—second valve; 52—flow meter;

[0059] 6—exhaust pipe; 61—third valve; 62—flue gas analyzer;

[0060] 7—Tail gas absorption bottle. DETAILED DESCRIPTION

[0061] The present invention is further described in detail below in conjunction with embodiments so that those skilled in the art can implement the invention with reference to the description.

[0062] It should be understood that the terms such as “having”, “including” and “comprising” used herein do not exclude the existence or addition of one or more other elements or combinations thereof.

[0063] The test methods used in the following examples are conventional methods unless otherwise specified. The materials and reagents used in the following examples are all commercially available unless otherwise specified. In the following examples, if no specific conditions are specified, the experiments were carried out under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used, if the manufacturer is not specified, are all conventional products that can be purchased commercially.

[0064] The present invention provides a system for treating nitrogen oxide tail gas in the production process of photovoltaic cells, referring to Figure 1 ,include:

[0065] The reactor 1 has an air inlet 11 and an air outlet 12, and the air inlet 11 is provided with an air inlet fan 13;

[0066] Two catalytic plates 2 are arranged in the reactor 1 at intervals. The catalytic plates 2 are hollow inside and transparent outside with a porous structure. The inside of the catalytic plates 2 is filled with Fe-modified TiO2 catalyst 21. A light catalytic chamber 22 is formed between the two catalytic plates 2 and the inner wall of the reactor 1.

[0067] The light source 3 is an ultraviolet lamp or a visible light lamp, and is disposed in the photocatalytic chamber 22;

[0068] Under the action of the air intake fan 13, the exhaust gas to be treated enters the reactor 1 from the air intake port 11, the exhaust gas contacts the Fe-modified TiO2 catalyst in the catalytic plate 2, and is reduced (for example, reduced to N2) under the illumination of the light source 3, and the treated exhaust gas is discharged through the outlet 12.

[0069] In a preferred embodiment, the reactor 1 is made of stainless steel and is rectangular in shape. The catalytic plate 2 is rectangular (with an area equal to the longitudinal section of the reactor 1 ), and its outer periphery is connected to the inner wall of the reactor 1 .

[0070] In a preferred embodiment, the Fe-modified TiO2 catalyst is prepared by the following method:

[0071] 1) Weigh 1.3-5.5 g of Fe3O4 and 0.025-0.1 g of polyvinyl pyrrolidone, add them into 20-80 mL of anhydrous ethanol, and ultrasonically disperse them for 10-40 min. Then, drop 8.5-34 ml of butyl titanate under stirring, and mix well to obtain solution A;

[0072] 2) Mix 2.5-10 mL of deionized water, 2.5-10 mL of glacial acetic acid and 20-80 mL of anhydrous ethanol to obtain solution B;

[0073] 3) Adding the B solution to the A solution under stirring, pouring the resulting mixture into a reaction kettle, and reacting under the following conditions: reacting at 160-200° C. for 4-16 hours, or reacting under the microwave at 160-200° C. and 250-1000W for 1-4 hours;

[0074] 4) After the reaction is complete, cool to room temperature, pour off the supernatant, add ethanol to the remaining solid, wash with alcohol and stir at 50-70°C for 1-4h;

[0075] 5) The alcohol-washed solution is centrifuged at a speed of 1750-7000 r / min for 5-20 min. The solid product obtained after centrifugation is dried at 70-90° C. for 4-16 h and ground to obtain an Fe-modified TiO2 catalyst.

[0076] In a preferred embodiment, the system further comprises:

[0077] An air storage tank 4 for caching waste gas to be treated is connected to the air inlet 11 of the reactor 1 through the air inlet pipe 5 , and an exhaust gas absorption bottle 7 is connected to the air outlet 12 of the reactor 1 through the exhaust pipe 6 .

[0078] In a preferred embodiment, a first valve 41 is provided on the gas storage tank 4 , and a second valve 51 and a flow meter 52 are provided on the air intake pipe 5 .

[0079] In a preferred embodiment, a third valve 61 and a flue gas analyzer 62 are provided on the exhaust pipe 6 .

[0080] In a preferred embodiment, the ultraviolet lamp is an 18W mercury lamp with a main wavelength of 254nm, and the visible lamp is a 35W incandescent lamp.

[0081] The present invention also provides a process for treating nitrogen oxide tail gas during the production process of photovoltaic cells, which uses the above system to purify the tail gas containing nitrogen oxides generated during the production process of photovoltaic cells. The method includes the following steps:

[0082] S1, collecting the tail gas containing nitrogen oxides generated in the production process of photovoltaic cells through the gas storage tank 4;

[0083] S2, close the third valve 61, open the first valve 41, the second valve 51, the air intake fan 13 and the light source 3, pass the tail gas in the gas storage tank 4 into the reactor 1, and keep it for 2-30 minutes after filling the reactor 1;

[0084] S3. Open the third valve 61 to allow the tail gas discharged from the reactor 1 to enter the tail gas absorption bottle 7, and be discharged after being absorbed by the absorbent in the bottle. By adjusting the first valve 41, the flow rate detected by the flow meter 52 reaches the designed value, thereby continuously treating the tail gas in the gas storage tank 4.

[0085] Photocatalytic technology is a new type of pollutant treatment technology. It can convert solar energy into energy required for chemical reactions. Under the action of semiconductor photocatalytic materials, pollutants are degraded. The degradation process is mainly that semiconductors are excited by visible light, which will generate electrons. Electrons undergo transitions to form electron-hole pairs. Electrons and holes react with O2 and H2O to generate highly oxidizing O 2-and ·OH, oxidizing and degrading the pollutants. The whole process does not require any other energy except the light source 3, and does not produce secondary pollutants, which has a good removal effect on pollutants. Semiconductor photocatalytic materials are the key to photocatalytic degradation of pollutants. TiO2 is currently the most widely used photocatalytic material because of its high photocatalytic activity, good chemical stability, non-toxicity and low price. However, TiO2 is affected by its own properties and there are also some problems. Because of its wide bandgap (3.2eV), it has a good absorption effect on ultraviolet light below 380nm, and has a low utilization rate for visible light above 400nm. In addition, there is also the problem of too fast recombination rate of photogenerated electron-hole pairs. These problems also restrict the practical application of TiO2.

[0086] Modification of TiO2 can improve the photochemical performance of the catalyst, and semiconductor composite is considered to be an effective method to improve the photocatalytic activity of TiO2. The heterojunction formed by the composite of TiO2 and other narrow-bandgap semiconductors can effectively reduce the bandgap of TiO2 and improve its photocatalytic activity. Fe3O4 is a photosensitive material with good economic efficiency. In the present invention, it is composited with TiO2 to prepare an efficient and environmentally friendly composite semiconductor photocatalytic material, which can improve the degradation performance of the photocatalytic system. In terms of the processing capacity of the entire device, it can process NO in many industries. x Waste gas is converted into harmless N2. The Fe-doped TiO2 catalyst reduces the sample particle size and increases the specific surface area, which is conducive to the photocatalytic oxidation reaction. At the same time, the incorporation of Fe can also make TiO2 respond to visible light, and the absorption spectrum is significantly red-shifted to the visible light region. The Fe-doped photocatalyst has a 15% and 10% higher denitration rate under ultraviolet and visible light than the undoped photocatalyst. The Fe element enters the TiO2 lattice in the form of substitution doping and forms a capture trap for photogenerated electrons and holes, effectively prolonging the separation of photogenerated carriers, thereby increasing the number of photogenerated carriers participating in the photocatalytic reaction, thereby improving the ultraviolet light catalytic denitration activity and expanding the response of visible light. Therefore, the Fe-modified TiO2 catalyst prepared in the present invention has a higher photocatalytic denitration effect and has a certain industrial application value.

[0087] In the present invention, the tail gas from the production process of photovoltaic cells enters the reactor 1, and after the synergistic effect of ultraviolet light irradiation and Fe-modified TiO2 catalyst, nitrogen oxides such as NO2 are reduced to N2, while Fe-doped 3+ , can play the following roles: (1) forming a capture center with a valence higher than Ti 4+ The metal ions capture electrons and have a lower valence than Ti 4+ The metal ions capture holes and suppress the hole h + and electronic -(2) forming doping energy levels so that photons with lower energy can also excite electrons and holes, thus improving the photon utilization rate; (3) extending the lifetime of electrons and holes.

[0088] The above is the overall concept of the present invention, and detailed embodiments and comparative examples are provided below on the basis of the overall concept of the present invention to further illustrate the present invention.

[0089] Example 1

[0090] A treatment system for nitrogen oxide tail gas in the production process of photovoltaic cells, referring to Figure 1 ,include:

[0091] The reactor 1 has an air inlet 11 and an air outlet 12, and the air inlet 11 is provided with an air inlet fan 13;

[0092] Two catalytic plates 2 are arranged in the reactor 1 at intervals. The catalytic plates 2 are hollow inside and transparent outside with a porous structure. The inside of the catalytic plates 2 is filled with Fe-modified TiO2 catalyst 21. A light catalytic chamber 22 is formed between the two catalytic plates 2 and the inner wall of the reactor 1.

[0093] The light source 3 is an ultraviolet lamp or a visible light lamp, and is disposed in the photocatalytic chamber 22;

[0094] Under the action of the air intake fan 13, the exhaust gas to be treated enters the reactor 1 from the air intake port 11, the exhaust gas contacts the Fe-modified TiO2 catalyst in the catalytic plate 2, and is reduced (for example, reduced to N2) under the illumination of the light source 3, and the treated exhaust gas is discharged through the outlet 12.

[0095] In this embodiment, the reactor 1 is made of stainless steel and is rectangular in shape. The catalytic plate 2 is rectangular (with an area equal to the longitudinal section of the reactor 1 ), and its outer periphery is connected to the inner wall of the reactor 1 .

[0096] In this embodiment, the system further includes:

[0097] A gas storage tank 4 for caching the waste gas to be treated is connected to the gas inlet 11 of the reactor 1 through the gas inlet pipe 5, and a tail gas absorption bottle 7 is connected to the gas outlet 12 of the reactor 1 through the exhaust pipe 6. A first valve 41 is provided on the gas storage tank 4, and a second valve 51 and a flow meter 52 (rotor flow meter 52) are provided on the gas inlet pipe 5. A third valve 61 and a flue gas analyzer 62 are provided on the exhaust pipe 6.

[0098] In this embodiment, the light source 3 is an ultraviolet lamp, specifically an 18W mercury lamp with a main wavelength of 254nm.

[0099] In this embodiment, the absorbent in the tail gas absorption bottle 7 is a sodium hydroxide solution with a mass concentration of 20%.

[0100] In this embodiment, the Fe-modified TiO2 catalyst is prepared by the following method:

[0101] 1) Weigh 2.7 g of Fe3O4 and 0.05 g of polyvinyl pyrrolidone into a clean beaker without water, then add 40 mL of anhydrous ethanol, ultrasonically disperse for 20 min, drop 17 ml of butyl titanate under rapid stirring, mix well, and obtain solution A;

[0102] 2) Add 5 mL of deionized water, 5 mL of glacial acetic acid and 40 mL of anhydrous ethanol into a constant pressure separatory funnel and mix well to obtain solution B;

[0103] 3) Add solution B to solution A under slow stirring (the dropping speed should not be too fast to prevent liquid splashing), pour the resulting mixture into a reactor, and react under microwave at 180°C and 500W for 2h;

[0104] 4) After the reaction is complete, cool to room temperature, pour off the supernatant, add ethanol to the remaining white columnar solid, put it in a constant temperature water bath with a magnetic stirrer, and stir for 2 hours at 60°C with alcohol washing;

[0105] 5) Pour the alcohol-washed solution into a centrifuge tube and centrifuge at 3500 r / min for 10 min. Place the solid product obtained after centrifugation in a forced air drying oven, dry at 80° C. for 8 h, and grind to obtain a Fe-modified TiO2 catalyst.

[0106] In this embodiment, the method for purifying the tail gas containing nitrogen oxides generated in the production process of photovoltaic cells by the system includes the following steps:

[0107] S1, collecting the tail gas containing nitrogen oxides generated in the production process of photovoltaic cells through the gas storage tank 4;

[0108] S2, close the third valve 61, open the first valve 41, the second valve 51, the air intake fan 13 and the light source 3, pass the tail gas in the gas storage tank 4 into the reactor 1, and keep it for 5 minutes after filling the reactor 1;

[0109] S3. Open the third valve 61 to allow the tail gas discharged from the reactor 1 to enter the tail gas absorption bottle 7, and be discharged after being absorbed by the absorbent in the bottle. By adjusting the first valve 41, the flow rate detected by the flow meter 52 reaches the designed value, thereby continuously treating the tail gas in the gas storage tank 4.

[0110] Test Case

[0111] The system and method of Example 1 were used to test the NO2 removal rate, wherein the removal rate calculation formula is as follows:

[0112]

[0113] In the above formula, η is the removal rate of NO2 (%); C i is the concentration of NO2 in the intake air (ppm); C o is the concentration of NO2 in the outlet gas (ppm). At the end of the reaction system, a gas washing bottle filled with sodium hydroxide solution is used to absorb the residual NO2 in the reaction gas to avoid environmental pollution. The entire reaction system connection pipeline is connected with a silicone tube.

[0114] Test Example 1

[0115] A mixture of NO2 gas and air was used as the exhaust gas, and the system and method in Example 1 were used for testing:

[0116] The NO2 flow rate into the reactor 1 is set to 0.5L / min, the NO2 concentration is 10ppm, the flow rate is monitored by the rotor flowmeter 52, the NO2 gas concentration in the outlet gas is measured by the flue gas analyzer 62, and the NO2 inlet gas is regularly replaced and supplemented; after continuous operation, the outlet gas can be stabilized at a NO2 concentration of less than 2ppm, and the removal rate reaches 86% after stabilization. The test results are as follows Figure 2 shown.

[0117] Test Example 2

[0118] A mixture of NO2 gas and air was used as the exhaust gas, and the system and method in Example 1 were used for testing:

[0119] The NO2 flow rate into the reactor 1 is set to 0.8L / min, and the NO2 concentration is set to 10ppm. The flow rate is monitored by the rotor flowmeter 52, and the NO2 gas concentration in the outlet gas is measured by the flue gas analyzer 62. The NO2 inlet gas is regularly replaced and supplemented; after continuous operation, the outlet gas can be stabilized at a NO2 concentration of less than 3ppm, and the removal rate reaches more than 75%. The test results are as follows Figure 3 shown.

[0120] Test Example 3

[0121] A mixture of NO2 gas and air was used as the exhaust gas, and the system and method in Example 1 were used for testing:

[0122] The NO2 flow rate into the reactor 1 is set to 1.0L / min, and the NO2 concentration is set to 10ppm. The flow rate is monitored by the rotor flowmeter 52, and the NO2 gas concentration in the outlet gas is measured by the flue gas analyzer 62. The NO2 inlet gas is regularly replaced and supplemented; after continuous operation, the outlet gas can be stabilized at a NO2 concentration below 3.5ppm, and the removal rate reaches 65%. The test results are as follows Figure 4 shown.

[0123] Although the embodiments of the present invention have been disclosed as above, they are not limited to the applications listed in the specification and the implementation modes. They can be fully applied to various fields suitable for the present invention. For those familiar with the art, additional modifications can be easily implemented. Therefore, without departing from the general concept defined by the claims and the scope of equivalents, the present invention is not limited to specific details.

Claims

1. A system for treating nitrogen oxide tail gas in the production process of photovoltaic cells, characterized in that: include: A reactor having an air inlet and an air outlet, wherein the air inlet is provided with an air intake fan; Two catalytic plates are arranged in the reactor at intervals, the catalytic plates are hollow inside, transparent outside and have a porous structure, the catalytic plates are filled with Fe-modified TiO2 catalyst, and a light catalytic chamber is formed between the two catalytic plates and the inner wall of the reactor; A light source, which is an ultraviolet lamp or a visible light lamp, is arranged in the photocatalytic chamber; Under the action of the air intake fan, the exhaust gas to be treated enters the reactor from the air intake port, the exhaust gas contacts the Fe-modified TiO2 catalyst in the catalytic plate, is reduced under the illumination of the light source, and the treated exhaust gas is discharged through the outlet.

2. The system for treating nitrogen oxide tail gas in the photovoltaic cell production process according to claim 1, characterized in that: The Fe-modified TiO2 catalyst is prepared by the following method: 1) Add Fe3O4 and polyvinyl pyrrolidone into anhydrous ethanol, disperse by ultrasonication, drop butyl titanate into the mixture under stirring, mix well, and obtain solution A; 2) Mix deionized water, glacial acetic acid and anhydrous ethanol to obtain solution B; 3) Adding the B solution to the A solution under stirring, pouring the resulting mixture into a reaction vessel, and reacting under heating alone or heating and microwave assistance; 4) After the reaction is complete, cool to room temperature, pour off the supernatant, add ethanol to the remaining solid, wash with alcohol and stir; 5) Centrifuging the alcohol-washed solution, drying and grinding the solid product obtained after centrifugation to obtain the Fe-modified TiO2 catalyst.

3. The system for treating nitrogen oxide tail gas in the photovoltaic cell production process according to claim 2, characterized in that: The Fe-modified TiO2 catalyst is prepared by the following method: 1) Weigh 1.3-5.5 g of Fe3O4 and 0.025-0.1 g of polyvinyl pyrrolidone, add them into 20-80 mL of anhydrous ethanol, and ultrasonically disperse them for 10-40 min. Then, drop 8.5-34 ml of butyl titanate under stirring, and mix well to obtain solution A; 2) Mix 2.5-10 mL of deionized water, 2.5-10 mL of glacial acetic acid and 20-80 mL of anhydrous ethanol to obtain solution B; 3) Adding the B solution to the A solution under stirring, pouring the resulting mixture into a reaction kettle, and reacting under the following conditions: reacting at 160-200° C. for 4-16 hours, or reacting under the microwave at 160-200° C. and 250-1000W for 1-4 hours; 4) After the reaction is complete, cool to room temperature, pour off the supernatant, add ethanol to the remaining solid, wash with alcohol and stir at 50-70°C for 1-4h; 5) The alcohol-washed solution is centrifuged at a speed of 1750-7000 r / min for 5-20 min, and the solid product obtained after centrifugation is dried at 70-90° C. for 4-16 h and ground to obtain the Fe-modified TiO2 catalyst.

4. The system for treating nitrogen oxide tail gas in the photovoltaic cell production process according to claim 3, characterized in that: The Fe-modified TiO2 catalyst is prepared by the following method: 1) Weigh 2.7 g of Fe3O4 and 0.05 g of polyvinyl pyrrolidone, add them into 40 mL of anhydrous ethanol, disperse them by ultrasonic for 20 min, add 17 ml of butyl titanate dropwise under stirring, mix well, and obtain solution A; 2) Mix 5 mL of deionized water, 5 mL of glacial acetic acid and 40 mL of anhydrous ethanol to obtain solution B; 3) Add solution B to solution A under stirring, pour the resulting mixture into a reactor, and react at 180°C for 8 hours; 4) After the reaction is complete, cool to room temperature, discard the supernatant, add ethanol to the remaining solid, wash with alcohol and stir at 60°C for 2h; 5) The alcohol-washed solution was centrifuged at a speed of 3500 r / min for 10 min, and the solid product obtained after centrifugation was dried at 80° C. for 8 h and ground to obtain the Fe-modified TiO2 catalyst.

5. The system for treating nitrogen oxide tail gas in the photovoltaic cell production process according to claim 3, characterized in that: The Fe-modified TiO2 catalyst is prepared by the following method: 1) Weigh 2.7 g of Fe3O4 and 0.05 g of polyvinyl pyrrolidone, add them into 40 mL of anhydrous ethanol, disperse them by ultrasonic for 20 min, add 17 ml of butyl titanate dropwise under stirring, mix well, and obtain solution A; 2) Mix 5 mL of deionized water, 5 mL of glacial acetic acid and 40 mL of anhydrous ethanol to obtain solution B; 3) Add solution B to solution A under stirring, pour the resulting mixture into a reaction kettle, and react under microwave at 180°C and 500W for 2h; 4) After the reaction is complete, cool to room temperature, discard the supernatant, add ethanol to the remaining solid, wash with alcohol and stir at 60°C for 2h; 5) The alcohol-washed solution was centrifuged at a speed of 3500 r / min for 10 min, and the solid product obtained after centrifugation was dried at 80° C. for 8 h and ground to obtain the Fe-modified TiO2 catalyst.

6. The system for treating nitrogen oxide tail gas in the photovoltaic cell production process according to claim 1 or 5, characterized in that: The system also includes: A gas storage tank for caching waste gas to be treated, which is connected to the air inlet of the reactor through an air inlet pipeline, and a tail gas absorption bottle, which is connected to the air outlet of the reactor through an exhaust pipeline.

7. The system for treating nitrogen oxide tail gas in the photovoltaic cell production process according to claim 6, characterized in that: The gas storage tank is provided with a first valve, and the air intake pipeline is provided with a second valve and a flow meter.

8. The system for treating nitrogen oxide tail gas in the photovoltaic cell production process according to claim 7, characterized in that: The exhaust pipe is provided with a third valve and a flue gas analyzer.

9. The system for treating nitrogen oxide tail gas in the photovoltaic cell production process according to claim 8, characterized in that: The ultraviolet lamp is an 18W mercury lamp with a main wavelength of 254nm, and the visible lamp is a 35W incandescent lamp.

10. A process for treating nitrogen oxide tail gas in the production process of photovoltaic cells, characterized in that: The method uses the system as described in any one of claims 8 to 9 to purify the tail gas containing nitrogen oxides generated in the production process of photovoltaic cells, and the method comprises the following steps: S1. collecting the tail gas containing nitrogen oxides generated in the production process of photovoltaic cells through the gas storage tank; S2, close the third valve, open the first valve, the second valve, the air intake fan and the light source, pass the tail gas in the gas storage tank into the reactor, and keep it for 2-30 minutes after filling the reactor; S3. Open the third valve to allow the tail gas discharged from the reactor to enter the tail gas absorption bottle, and then be discharged after being absorbed by the absorbent in the bottle. By adjusting the first valve, the flow rate detected by the flow meter reaches the designed value, thereby continuously treating the tail gas in the gas storage tank.

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