Method for purifying gas containing organic pollutants

Abstract

The invention discloses a method for purifying gas containing organic pollutants. The purification method comprises two working states, namely, the first working state is an adsorption purification state, the second working state is an in-situ catalytic oxidation state, in the second working state, the oxygen concentration in the reactor is controlled, and the oxygen concentration in the reactor is controlled. Starting a bed layer temperature control system to heat the adsorption oxidant bed layer and the catalytic oxidation catalyst bed layer to a reaction starting temperature, then carrying out step-by-step heating and temperature control on the adsorption oxidant bed layer and the catalytic oxidation catalyst bed layer, continuously discharging the reacted purified gas out of the reactor, and then adjusting the temperature of the bed layers, so as to obtain the catalyst. And switching to the first working state. When the method is used for treating the gas containing the organic pollutants, under the condition that the intrinsic safety of the reactor can be guaranteed, the temperature of the reaction area is effectively controlled through efficient heat exchange to achieve in-situ adsorption and oxidation reaction, the problem that the adsorbed organic pollutants are not converted due to desorption and the like is effectively avoided, and the adsorption efficiency is improved. And a good purification effect is finally obtained.

Description

Technical Field

[0001] The present invention belongs to the field of VOCs gas treatment, and particularly relates to a purification method for gases containing organic pollutants. Background Art

[0002] VOCs (volatile organic compounds) emitted without organization within the chemical industrial park boundary often contain toxic and harmful gases (such as benzene series compounds, etc.), which pose a hazard to the physical health of employees. In addition to controlling the sources of unorganized emissions, purifying the VOCs gas in the air of enclosed places (such as operating rooms, rest rooms, etc.) where employees work or rest for a long time is of great significance for improving the environmental quality of the working and resting environment of employees. Different from the small amount of ultra-low concentration toxic and harmful gases (such as formaldehyde commonly found in decoration) in VOCs present in general indoor gases, the unorganized emissions of VOCs in the factory area are characterized by complex components and relatively high concentrations (compared with general indoor gases). One of the two mainstream air purification processes is to use an adsorbent to adsorb pollutants into its pores, and then the device can be used for a long time by replacing the adsorbent. This method is not applicable to the purification of VOCs gas in the enclosed area of the chemical industrial park. One of the main reasons is that the pollutant concentration in this environment is relatively high, and the method of replacing the adsorbent will lead to an increase in consumable costs and the generation of a large amount of solid waste. The other is to first adsorb pollutants into the pores of the adsorbent through the adsorbent, and then switch the gas path to desorb the pollutants into the catalytic oxidation device, and use off-site catalytic oxidation to treat them. This method has a long process flow, which easily leads to a large volume, much floor space, and an increase in manufacturing costs when designing the device. At the same time, the adsorbents generally used in both processes are targeted at conventional indoor toxic and harmful gases, and the adsorption effect on the complex VOCs gas present in the factory area is not ideal.

[0003] There is also a process means to directly in-situ catalytically oxidize the adsorbed VOCs while regenerating the storage material, thereby shortening the process flow and reducing the operating cost.

[0004] CN113648795A discloses a highly efficient plasma-assisted multi-technology flue gas purification device, which is characterized by using plasma discharge as the heat source for the catalytic reaction. The problem with it is the risk brought by high-voltage discharge during actual application, especially in places such as chemical industrial areas where higher safety requirements are imposed.

[0005] CN107789941A discloses a method for microwave-induced adsorption in-situ catalytic oxidation to degrade organic pollutants. This method uses microwave heating as the heat source for the catalytic reaction. The problem with it is that the microwave reactor has a large volume and is not easy to be made into a portable device, which is inconvenient to use in enclosed places with limited space.

[0006] CN216677734U discloses a device for providing indoor fresh air for petrochemical enterprises. The method of using ultraviolet light irradiation as the energy source for the catalytic oxidation reaction has problems such as low conversion efficiency, large volume of the reactor required, difficulty in making it into a portable device, and inconvenience in use in enclosed places with limited space.

[0007] CN113663472B discloses a multi-stage treatment method for organic waste gas. The method includes adsorbing and treating the organic waste gas by an adsorption assembly in which a plurality of adsorption columns filled with nitrogen-doped carbon adsorbents are connected in series, then performing heating and desorption treatment on the adsorption assembly, and the gas after desorption of the adsorption assembly enters a catalytic oxidation reactor for catalytic oxidation treatment under the catalysis of a nitrogen-doped cobalt / manganese oxide material coated with amorphous silica. This method only makes the adsorption unit into a multi-stage adsorption, and the adsorption unit and the catalytic oxidation unit exist independently of each other, and there are still problems such as low energy efficiency and large space required for the equipment.

[0008] CN101314101A discloses a method for purifying air by combining adsorption and in-situ thermal catalytic oxidation regeneration. The method is to use a porous material with both adsorption and catalytic functions, and a porous material with a protective adsorption function to adsorb low-concentration formaldehyde and benzene series in the air; when the adsorption of the porous material is close to saturation, electric heating is started to activate the catalytic activity of the porous material with both adsorption and catalytic functions, and catalytically oxidize the formaldehyde and benzene series adsorbed on the surface of the porous material into carbon dioxide and water; at the same time, the adsorption capacity of the porous material is regenerated; the regenerated porous material is reused for adsorption, and the air is purified in this cycle. In this method, although the porous material with both adsorption and catalytic functions can carry out oxidation reaction on organic substances, during the reaction process, there will still be some organic substances escaping, resulting in poor air purification effect. Summary of the Invention

[0009] In view of the characteristics of the gas containing organic pollutants, especially the VOCs gas in the enclosed area of the chemical plant area, the present invention provides a method for purifying the gas containing organic pollutants. The method of the present invention can effectively control the temperature of the reaction area through efficient heat exchange to achieve in-situ adsorption and oxidation reaction while ensuring the intrinsic safety of the reactor, effectively avoid the problem that the adsorbed organic pollutants are not converted due to desorption and other reasons, and finally obtain a good purification effect.

[0010] The present invention provides a method for purifying the gas containing organic pollutants, including two working states, wherein:

[0011] The first working state is the adsorption and purification state, including: the gas containing organic pollutants enters the reactor and contacts the adsorption oxidant and the catalytic oxidation catalyst in sequence, and the purified gas after adsorption is discharged from the reactor; in the first working state, the introduced gas containing organic pollutants and the discharged purified gas are detected in real time, and when the mass concentration of the organic pollutants in the purified gas does not meet the preset emission requirements, it is switched to the second working state;

[0012] The second working state is the in-situ catalytic oxidation state, including: starting the nitrogen protection gas path to introduce nitrogen into the reactor, controlling the oxygen concentration in the reactor, starting the bed temperature control system to heat the adsorption oxidant bed and the catalytic oxidation catalyst bed until the reaction start temperature, and then gradually heating and controlling the temperature of the adsorption oxidant bed and the catalytic oxidation catalyst bed, continuously discharging the purified gas after the reaction from the reactor, and then adjusting the bed temperature control system to cool the adsorption oxidant bed and the catalytic oxidation catalyst bed to the temperature in the adsorption and purification state, and then switching to the first working state.

[0013] The present invention also provides a purification system, wherein the purification system includes:

[0014] A reactor, in which an adsorption oxidant bed and a catalytic oxidation catalyst bed are sequentially arranged from bottom to top;

[0015] A purification and adsorption gas path for the gas containing organic pollutants to enter the reactor and the purified gas after adsorption and purification to be discharged from the reactor;

[0016] A catalytic oxidation exhaust gas path for the reaction products of the catalytic oxidation catalyst bed to be discharged from the reactor;

[0017] A nitrogen protection gas path for filling nitrogen into the reactor to control the oxygen concentration in the reactor; and

[0018] A bed temperature control system for adjusting the temperatures of the adsorption oxidant bed and the catalytic oxidation catalyst bed.

[0019] Further, the adsorption oxidant bed is filled with an adsorption oxidant for adsorbing organic pollutants and performing an in-situ oxidation reaction to remove organic pollutants.

[0020] Further, the catalytic oxidation catalyst bed is filled with a catalytic oxidation catalyst for catalytically oxidizing organic pollutants.

[0021] Further, the purification and adsorption gas path includes an inlet gas pipeline entering the reactor, which is arranged at the lower part or the bottom of the reactor, and an outlet gas pipeline discharging from the reactor, which is arranged at the upper part or the top of the reactor.

[0022] Further, the catalytic oxidation exhaust gas path includes an outlet gas pipeline discharging from the reactor, which is arranged at the upper part or the top of the reactor.

[0023] Further, the nitrogen protection gas path includes an inlet gas pipe entering the reactor, which is arranged at the lower part or the bottom of the reactor.

[0024] Further, the bed temperature control system is used to adjust the temperatures of the adsorption oxidant bed and the catalytic oxidation catalyst bed. By setting the bed temperature control system, when the adsorption oxidant bed is in the oxidation stage, it can prevent the bed temperature from rising too fast and causing the desorption of organic pollutants, and after the oxidation stage ends, it can quickly reduce the temperature of the adsorption oxidant bed and switch to the adsorption purification state as soon as possible.

[0025] Further, a sandwich heat exchanger is arranged in the adsorption oxidant bed and the catalytic oxidation catalyst bed, and the sandwich heat exchanger uses a phase change material with a melting temperature in the reaction temperature range to maintain the bed temperature.

[0026] The method of the present invention is applicable to the purification of gas containing organic pollutants, and is particularly applicable to the purification of VOCs gas in the closed area of a chemical industrial park. The organic pollutants can be formaldehyde and benzene series compounds, and the benzene series compounds include benzene, toluene, xylene, etc. The mass content of benzene series compounds in the gas containing organic pollutants is above 0.01 ppm, and can be 0.01 - 30 ppm. The mass content of formaldehyde in the gas containing organic pollutants is above 0.01 ppm, and can be 0.01 - 30 ppm.

[0027] Compared with the prior art, the present invention has the following advantages:

[0028] The inventors of the present invention have found through research that by controlling the timing of transferring from the first working state to the second working state and the operation of the second working state, the safety of the oxidation process in the catalytic oxidation reaction stage can be ensured. At the same time, by using the method of gradually heating and controlling the temperature to discharge the purified gas after the reaction from the reactor, on the one hand, the organic pollutants can be converted more fully, and on the other hand, the safety of the reaction stage system in the second working state is further ensured. Description of the Drawings

[0029] Figure 1 It is a schematic diagram of the purification system of the present invention;

[0030] Among them, the description of the reference numerals is as follows:

[0031] A01 - Compressor; A02 - Adsorption oxidant bed; A03 - Catalytic oxidation catalyst bed; A04 - Heat exchanger; A05 - Heat exchanger; C01 - Outlet of the purified gas after adsorption; C02 - Outlet of the purified gas after the reaction; C03 - Air inlet. Detailed Embodiments

[0032] The present invention will be described in detail below with reference to the drawings and embodiments.

[0033] like Figure 1 As shown, the purification system of the present invention comprises:

[0034] A reactor, wherein an adsorption oxidant bed A02 and a catalytic oxidation catalyst bed A03 are sequentially arranged from bottom to top in the reactor; the reactor is a fixed bed reactor;

[0035] The purification adsorption gas circuit is used to introduce the gas containing organic pollutants into the reactor through the air inlet C03 via the compressor A01, and the purified gas after adsorption and purification is discharged from the reactor through the purified gas outlet C01;

[0036] The catalytic oxidation exhaust gas circuit is provided with a purified gas outlet CO2 after the reaction, which is used for the oxidation reaction product to discharge from the reactor;

[0037] Nitrogen protection gas circuit (not shown) is used to fill nitrogen into the reactor to control the oxygen concentration in the reactor;

[0038] The bed temperature control system is used to adjust (such as heating or cooling) the temperature of the adsorption oxidant bed A02 and the catalytic oxidation catalyst bed A03, for example, by using a heater and a heat exchange device in the bed. The heat exchange device is such as Figure 1 Heat exchanger A04 and heat exchanger A05 are shown in FIG.

[0039] The workflow of the purification system of the present invention is as follows:

[0040] (1) The first working state is the adsorption purification state, including: the gas containing organic pollutants is introduced into the reactor from the air inlet C03 by the compressor A01, and after passing through the adsorption oxidant bed A02 and the catalytic oxidation catalyst bed A03, the purified gas after adsorption purification is discharged from the reactor through the purified gas outlet C01; in the first working state, the introduced gas containing organic pollutants and the discharged purified gas are detected in real time, and when the mass concentration of organic pollutants in the discharged purified gas does not meet the preset emission requirements (the preset emission requirements can be formulated according to the corresponding control standards, the emission requirements are 40%-100% of the upper limit of the standard, and more preferably 40%-60% of the upper limit of the standard, such as the pollutant requirements in GB / T 18883-2022 "Indoor Air Quality Standard", such as toluene requirement is less than 0.2mg / m 3 That is 48.7ppb, and formaldehyde is required to be less than 0.08mg / m 3 That is 59.7ppb, then the preset emission requirement for toluene is 19.5-48.7ppb, preferably 19.5-29.2ppb, and the preset emission requirement for formaldehyde is 23.8-59.7ppb, preferably 23.8-35.9ppb), and then switch to the second working state.

[0041] (2) The second working state is the in-situ catalytic oxidation state, including: starting the nitrogen protection gas path to introduce nitrogen into the reactor, controlling the oxygen concentration in the reactor (preferably, the volume concentration of oxygen is 5%-10%), starting the bed temperature control system to heat the adsorption oxidant bed A02 and the catalytic oxidation catalyst bed A03 until the reaction start temperature (preferably, the reaction start temperature is 100-300 °C; when the organic pollutant contains toluene, the reaction start temperature is 150-165 °C; when the organic pollutant contains formaldehyde, the reaction start temperature is 105-120 °C), then gradually heating and controlling the temperature of the adsorption oxidant bed and the catalytic oxidation catalyst bed, continuously discharging the purified gas after the reaction from the reactor, and then adjusting the bed temperature control system to cool the adsorption oxidant bed and the catalytic oxidation catalyst bed to the temperature of the adsorption purification state, and then switching to the first working state.

[0042] In the method of the present invention, when gradually heating and controlling the temperature and the organic pollutant contains toluene, it is preferably to adopt three-stage heating and temperature control. The first stage is heated to 150-165 °C and maintained for 3-7 minutes, the second stage is heated to 195-210 °C and maintained for 3-7 minutes, and the third stage is heated to 245-260 °C and maintained for 3-7 minutes. Preferably, the temperature rise rate to the first-stage reaction temperature is 15-25 °C / min, and the temperature rise rates to the second and third stages are 5-12 °C / min.

[0043] In the method of the present invention, when gradually heating and controlling the temperature and the organic pollutant contains formaldehyde, it is preferably to adopt two-stage heating and temperature control. The first stage is heated to 105-120 °C and maintained for 3-7 minutes, and the second stage is heated to 155-175 °C and maintained for 3-7 minutes. Preferably, the temperature rise rate to the first-stage reaction temperature is 15-25 °C / min, and the temperature rise rate to the second stage is 5-12 °C / min.

[0044] In the method of the present invention, a heat exchanger with a sandwich layer is arranged in the bed, and the heat exchanger in the sandwich layer contains a phase change material with a melting or vaporization temperature in the reaction temperature range, and its very large phase change latent heat is used to maintain the bed temperature.

[0045] In the method of the present invention, when gradually heating and controlling the temperature, it is preferably to adopt the phase change latent heat heat exchange method, that is, phase change materials with different melting points can be respectively installed in the heat exchange pipelines of the heat exchanger according to the temperature control requirements to meet the requirements of gradually controlling the temperature.

[0046] In the present invention, the adsorption oxidant bed is filled with an adsorption oxidant, which has the functions of chemically adsorbing organic pollutants and catalytically oxidizing organic pollutants. Generally, conventional adsorption oxidants can be used as the adsorption oxidant. For example, the adsorption oxidant includes a carrier and an active metal, wherein the carrier is at least one porous material selected from titanium dioxide, alumina, and molecular sieves (such as Beta zeolite and Y zeolite), and the active metal is at least one of Cu, Ag, Co, and Mn. The mass content of the active metal in the catalyst is 2% - 10%. The said adsorption oxidant can adsorb organic pollutants at normal temperature and catalytically oxidize organic pollutants into carbon dioxide and water at the reaction temperature.

[0047] In the present invention, the catalytic oxidation catalyst bed is filled with a catalytic oxidation catalyst, generally a supported catalyst, which includes a carrier and an active component. The said carrier can be a molecular sieve. The active component is a noble metal, selected from at least one of Pd, Pt, Ru, and Ag.

[0048] In the present invention, for the said catalytic oxidation catalyst, based on the mass of the catalyst, the mass content of the carrier is 99.0% - 99.5%, and the mass content of the active component calculated as an element is 0.5% - 1.0%.

[0049] In the present invention, in the said catalytic oxidation catalyst, the molecular sieve can be selected from at least one of Y zeolite, Beta zeolite, X-type zeolite, ZSM-5 zeolite, and ZSM-11 zeolite.

[0050] The catalytic oxidation catalyst of the present invention can be prepared by existing methods, such as the impregnation method. The impregnation method includes: preparing an impregnation solution containing the active component, impregnating the carrier with the impregnation solution, and then drying and calcining to obtain the catalytic oxidation catalyst. The impregnation method generally adopts conventional impregnation methods such as the equal-volume impregnation method. The drying temperature is 100 - 150 °C, and the time is 12 - 24 hours; the calcination temperature is 200 - 300 °C, and the time is 2 - 4 hours.

[0051] The catalytic oxidation catalyst of the present invention can be made into a shaped catalyst according to the size of the reactor, the gas flow rate to be treated, and the system pressure drop limit, etc. The shaped catalyst can be an extruded shaped catalyst or can also be prepared into a monolithic catalyst, such as coating the catalyst slurry onto a honeycomb ceramic body.

[0052] In the present invention, the volume ratio of the catalyst filled in the adsorption oxidant bed to the catalyst filled in the catalytic oxidation catalyst bed is 5 - 10:1.

[0053] In the present invention, in the first working state, i.e., the adsorption purification state, the adsorption conditions are as follows: the temperature is 25 - 60 °C.

[0054] Example 1

[0055] There are three kinds of adsorption oxidants used in this example: adsorption oxidant A, adsorption oxidant B, and adsorption oxidant C. Adsorption oxidant A uses Beta zeolite as a carrier and is loaded with 5% Ag by mass fraction. Adsorption oxidant B uses Beta zeolite as a carrier and is loaded with 2.5% Cu and 2.5% Ag by mass fraction. Adsorption oxidant C uses HZSM-5 zeolite as a carrier and is loaded with 2.5% Cu and 2.5% Ag by mass fraction. The catalytic oxidation catalyst uses Y zeolite as a carrier and is loaded with 0.5% Pd. The adsorption oxidant and the catalytic oxidation catalyst are respectively filled in the adsorption oxidant bed layer and the catalytic oxidation catalyst bed layer, and the filling volume ratio is 5:1. Among them, the volume ratio of adsorption oxidant A, adsorption oxidant B, and adsorption oxidant C is 1:1:1, and they are filled in a mixed way.

[0056] The raw material gas is the VOCs gas in the enclosed area of the chemical industrial park, and the average mass concentration of toluene in it is 5 ppm. Among them, the preset emission requirement of toluene formulated according to GB / T 18883-2022 "Indoor Air Quality Standard" is 25 ppb.

[0057] The first working state is the adsorption purification state: the volume of the adsorption bed layer is 5 m 3 , and the air volume is introduced at 2000 m 3 / h. The average toluene concentration of the gas is 5 ppm. After adsorbing for 20 hours, the toluene concentration at the outlet is less than 24 ppb. After 20 hours, the toluene concentration at the outlet reaches 25 ppb, and it is switched to the second working state;

[0058] The second working state is the in-situ catalytic oxidation state: the introduced air volume is reduced to 100 m 3 / h, and at the same time, 100 m 3 / h of nitrogen is introduced to reduce the volume concentration of oxygen to 10%. The bed layer temperature control system is started to heat the adsorption oxidant bed layer and the catalytic oxidation catalyst bed layer until 150 °C, and then gradually heated and temperature-controlled (when temperature-controlled, the three heat exchange media used in the heat exchanger are kerosene with a boiling range of 145-155 °C, N-methylpyrrolidone (NMP) with a boiling point of 202 °C, and cetyltrimethoxysilane with a boiling point of 250-260 °C, which are used to maintain the stability of the three-stage reaction temperature). The temperature rise rate to the first-stage reaction temperature is 20 °C / min, and the temperature rise rates to the second and third stages are 10 °C / min. The first-stage reaction temperature is 150 °C, and the reaction lasts for 5 minutes. The second-stage reaction temperature is 200 °C, and the reaction lasts for 5 minutes. The third-stage reaction temperature is 250 °C, and the reaction lasts for 5 minutes. During this process, the purified gas after the reaction is continuously discharged from the reactor, and the toluene concentration in it is less than 0.5 ppm. Then, the bed layer temperature control system is adjusted to cool the adsorption oxidant bed layer and the catalytic oxidation catalyst bed layer to room temperature, and then it is switched to the first working state.

[0059] Example 2

[0060] There are three kinds of adsorption oxidants used in this example: adsorption oxidant A, adsorption oxidant B, and adsorption oxidant C. Adsorption oxidant A uses Beta zeolite as the carrier and is loaded with 5% Ag by mass fraction. Adsorption oxidant B uses Beta zeolite as the carrier and is loaded with 2.5% Cu and 2.5% Ag by mass fraction. Adsorption oxidant C uses HZSM-5 zeolite as the carrier and is loaded with 2.5% Cu and 2.5% Ag by mass fraction. The catalytic oxidation catalyst uses Y zeolite as the carrier and is loaded with 0.5% Pd. The adsorption oxidant and the catalytic oxidation catalyst are respectively filled in the adsorption oxidant bed layer and the catalytic oxidation catalyst bed layer, and the filling volume ratio is 5:1. Among them, the volume ratio of adsorption oxidant A, adsorption oxidant B, and adsorption oxidant C is 1:1:1, and they are filled in a mixed way.

[0061] The raw material gas is the VOCs gas in the closed area of the chemical industrial park, and the average mass concentration of toluene in it is 5 ppm. Among them, the preset emission requirement of toluene formulated according to GB / T 18883-2022 "Indoor Air Quality Standard" is 25 ppb.

[0062] The first working state is the adsorption purification state: the volume of the adsorption bed layer is 5 m 3 ³, and the air is introduced at a flow rate of 2500 m 3 ³ / h. The average toluene concentration of the gas is 5 ppm. After adsorbing for 8 hours, the toluene concentration at the outlet is less than 24 ppb. After 8 hours, when the toluene concentration at the outlet reaches 25 ppb, it is switched to the second working state;

[0063] The second working state is the in-situ catalytic oxidation state: the introduced air volume is reduced to 100 m 3 ³ / h, and at the same time, 100 m 3 ³ / h of nitrogen is introduced to reduce the oxygen concentration to 10%. The bed layer temperature control system is started to heat the adsorption oxidant bed layer and the catalytic oxidation catalyst bed layer to 150 °C, and then gradually heated and temperature-controlled (when temperature-controlled, the three heat exchange media used in the heat exchanger are kerosene with a boiling point of 145-155 °C, N-methylpyrrolidone (NMP) with a boiling point of 202 °C, and hexadecyltrimethoxysilane with a boiling point of 250-260 °C, which are used to maintain the stability of the three-stage reaction temperature). The temperature rise rate to the first-stage reaction temperature is 20 °C / min, and the temperature rise rates to the second and third stages are 10 °C / min. The first-stage reaction temperature is 150 °C, and the reaction lasts for 5 minutes. The second-stage reaction temperature is 200 °C, and the reaction lasts for 5 minutes. The third-stage reaction temperature is 250 °C, and the reaction lasts for 5 minutes. During this process, the purified gas after the reaction is continuously discharged from the reactor, and the toluene concentration in it is less than 0.5 ppm. Then, the bed layer temperature control system is adjusted to cool the adsorption oxidant bed layer and the catalytic oxidation catalyst bed layer to room temperature, and then switched to the first working state.

[0064] Example 3

[0065] There are three kinds of adsorption oxidants used in this example: adsorption oxidant A, adsorption oxidant B, and adsorption oxidant C. Adsorption oxidant A uses Beta zeolite as the carrier and is loaded with 5% Ag by mass fraction. Adsorption oxidant B uses Beta zeolite as the carrier and is loaded with 2.5% Cu and 2.5% Ag by mass fraction. Adsorption oxidant C uses HZSM-5 zeolite as the carrier and is loaded with 2.5% Cu and 2.5% Ag by mass fraction. The catalytic oxidation catalyst uses Y zeolite as the carrier and is loaded with 0.5% Pd. The adsorption oxidant and the catalytic oxidation catalyst are respectively filled in the adsorption oxidant bed layer and the catalytic oxidation catalyst bed layer, and the filling volume ratio is 5:1, where the volume ratio of adsorption oxidant A, adsorption oxidant B, and adsorption oxidant C is 1:1:1, and they are filled in a mixed manner.

[0066] The raw material gas is the VOCs gas in the closed area of the chemical industrial park, and the average concentration of formaldehyde in it is 10 ppm. Among them, the preset emission requirement for formaldehyde formulated according to GB / T 18883-2022 "Indoor Air Quality Standard" is 30 ppb.

[0067] The first working state, namely the adsorption purification state: the volume of the adsorption bed layer is 5 m 3 ³, and the air volume is introduced at 2000 m 3 ³ / h. The average formaldehyde concentration of the gas is 10 ppm. After adsorbing for 20 hours, the outlet formaldehyde concentration is less than 29 ppb. After 20 hours, when the outlet formaldehyde concentration reaches 30 ppb, it is switched to the second working state;

[0068] The second working state is the in-situ catalytic oxidation state: the introduced air volume is reduced to 100 m 3 ³ / h, and at the same time, 100 m 3 ³ / h of nitrogen is introduced to reduce the oxygen concentration to 10%. The bed layer temperature control system is started to heat the adsorption oxidant bed layer and the catalytic oxidation catalyst bed layer until 120 °C, and then gradually heated and temperature-controlled (when temperature-controlled, the two heat exchange media used in the heat exchanger are zinc stearate with a melting point of 120 °C and turpentine with a boiling point of 154-170 °C, which are used to maintain the stability of the secondary reaction temperature). The temperature rise rate to the first-stage reaction temperature is 20 °C / min, and the temperature rise rate to the second stage is 10 °C / min. The first-stage reaction temperature is 120 °C, and the reaction lasts for 5 minutes. The second-stage reaction temperature is 160 °C, and the reaction lasts for 5 minutes. During this process, the purified gas after the reaction is continuously discharged from the reactor, and the formaldehyde concentration in it is less than 0.5 ppm. Then, the bed layer temperature control system is adjusted to cool the adsorption oxidant bed layer and the catalytic oxidation catalyst bed layer to room temperature, and then switched to the first working state.

[0069] Comparative Example 1

[0070] In this example, there are three kinds of adsorbed oxidants: adsorbed oxidant A, adsorbed oxidant B, and adsorbed oxidant C. Adsorbed oxidant A uses Beta zeolite as the carrier and is loaded with 5% Ag by mass fraction. Adsorbed oxidant B uses Beta zeolite as the carrier and is loaded with 2.5% Cu and 2.5% Ag by mass fraction. Adsorbed oxidant C uses HZSM-5 zeolite as the carrier and is loaded with 2.5% Cu and 2.5% Ag by mass fraction. The catalytic oxidation catalyst uses Y zeolite as the carrier and is loaded with 0.5% Pd. The adsorbed oxidant and the catalytic oxidation catalyst are respectively filled in the adsorbed oxidant bed layer and the catalytic oxidation catalyst bed layer, and the filling volume ratio is 5:1. Among them, the volume ratio of adsorbed oxidant A, adsorbed oxidant B, and adsorbed oxidant C is 1:1:1, and they are filled in a mixed manner.

[0071] The raw material gas is the VOCs gas in the closed area of the chemical industrial park, and the average concentration of toluene in it is 5 ppm. Among them, according to the "Indoor Air Quality Standard" GB / T 18883-2022, the preset emission requirement for toluene is 25 ppb.

[0072] The first working state is the adsorption purification state: the volume of the adsorption bed layer is 5 m 3 , and the air volume is introduced at 2000 m 3 / h. The average toluene concentration of the gas is 5 ppm. After adsorbing for 20 hours, the toluene concentration at the outlet is less than 24 ppb. After 20 hours, the toluene concentration at the outlet reaches 25 ppb, and it is switched to the second working state;

[0073] The second working state is the in-situ catalytic oxidation state: the introduced air volume is reduced to 100 m 3 / h, and at the same time, 100 m 3 / h of nitrogen is introduced to reduce the oxygen concentration to 10%. The bed layer temperature control system is started to heat the adsorbed oxidant bed layer and the catalytic oxidation catalyst bed layer until 250 °C, and the bed layer temperature is not allowed to exceed 400 °C by using conventional cold air heat exchange. The reaction lasts for 20 minutes. During this process, the purified gas after the reaction is continuously discharged from the reactor, and the toluene concentration will fluctuate above 10 ppm at the peak. Then, the bed layer temperature control system is adjusted to cool the adsorbed oxidant bed layer and the catalytic oxidation catalyst bed layer to room temperature, and then it is switched to the first working state.

[0074] Comparative Example 2

[0075] There are three kinds of adsorption oxidants used in this example: adsorption oxidant A, adsorption oxidant B, and adsorption oxidant C. Adsorption oxidant A uses Beta zeolite as the carrier and is loaded with 5% Ag by mass. Adsorption oxidant B uses Beta zeolite as the carrier and is loaded with 2.5% Cu and 2.5% Ag by mass. Adsorption oxidant C uses HZSM-5 zeolite as the carrier and is loaded with 2.5% Cu and 2.5% Ag by mass. The catalytic oxidation catalyst uses Y zeolite as the carrier and is loaded with 0.5% Pd. The adsorption oxidant and the catalytic oxidation catalyst are respectively filled in the adsorption oxidant bed layer and the catalytic oxidation catalyst bed layer, and the filling volume ratio is 5:1. Among them, the volume ratio of adsorption oxidant A, adsorption oxidant B, and adsorption oxidant C is 1:1:1, and they are filled in a mixed manner.

[0076] The raw material gas is the VOCs gas in the closed area of the chemical industrial park, and the average concentration of toluene in it is 5 ppm. Among them, the preset emission requirement for toluene formulated according to GB / T 18883-2022 "Indoor Air Quality Standard" is 25 ppb.

[0077] The first working state is the adsorption purification state: the volume of the adsorption bed layer is 5 m 3 , and the air volume is introduced at 2000 m 3 / h. The average toluene concentration of the gas is 5 ppm. After adsorbing for 16 hours, the toluene concentration at the outlet is less than 24 ppb. After 16 hours, the toluene concentration at the outlet reaches 25 ppb, and it is switched to the second working state;

[0078] The second working state is the in-situ catalytic oxidation state: the introduced air volume is reduced to 100 m 3 / h. At the same time, 100 m 3 / h of nitrogen is introduced to reduce the oxygen concentration to 10%. The bed layer temperature control system is started to heat the adsorption oxidant bed layer and the catalytic oxidation catalyst bed layer to 150 °C without heat exchange. The reaction lasts for 20 minutes, and the bed layer temperature continues to rise to above 450 °C. The purified gas after the reaction is continuously discharged, and the toluene concentration will fluctuate to above 10 ppm at the peak. Then, the bed layer temperature control system is adjusted to cool the adsorption oxidant bed layer and the catalytic oxidation catalyst bed layer to room temperature, and then it is switched to the first working state.

[0079] Comparative Example 3

[0080] Compared with Example 1, the difference is only that:

[0081] The introduced air volume is reduced to 100 m 3 / h. At the same time, 100 m 3 / h nitrogen gas is used to reduce the oxygen concentration to 10%. The bed temperature control system is started to heat the adsorption oxidant bed and the catalytic oxidation catalyst bed to 150°C, and conventional cold air heat exchange is used to maintain the bed temperature not exceeding 400°C, and the reaction lasts for 30 minutes. Then, the bed temperature is directly increased to 250°C, and the purified gas after the reaction is discharged, in which the toluene concentration is greater than 5 ppm. Then, the bed temperature control system is adjusted to cool the adsorption oxidant bed and the catalytic oxidation catalyst bed to room temperature, and then it is switched to the first working state.

Claims

1. A purification method for gas containing organic pollutants, including two working states, wherein: The first working state is the adsorption purification state, including: the gas containing organic pollutants enters the reactor and contacts the adsorption oxidant and the catalytic oxidation catalyst in sequence, and the purified gas after adsorption is discharged from the reactor; in the first working state, the introduced gas containing organic pollutants and the discharged purified gas are detected in real time, and when the mass concentration of organic pollutants in the purified gas does not meet the preset emission requirements, it is switched to the second working state; The second working state is the in-situ catalytic oxidation state, including: starting the nitrogen protection gas path to introduce nitrogen into the reactor, controlling the oxygen concentration in the reactor, starting the bed temperature control system to heat the adsorption oxidant bed and the catalytic oxidation catalyst bed until the reaction start temperature, and then gradually heating and controlling the temperature of the adsorption oxidant bed and the catalytic oxidation catalyst bed, continuously discharging the purified gas after the reaction from the reactor, and then adjusting the bed temperature control system to cool the adsorption oxidant bed and the catalytic oxidation catalyst bed to the temperature in the adsorption purification state, and then switching to the first working state.

2. The method according to claim 1, wherein The gas containing organic pollutants is the VOCs gas in the closed area of the chemical industrial park. Preferably, the organic pollutants are formaldehyde and / or benzene series compounds, and the benzene series compounds include at least one of benzene, toluene, and xylene; Further, the mass content of benzene series compounds in the gas containing organic pollutants is above 0.01 ppm, further 0.01 - 30 ppm, and / or the mass content of formaldehyde in the gas containing organic pollutants is above 0.01 ppm, further 0.01 - 30 ppm.

3. The method according to claim 1 or 2, characterized in that, When the mass concentration of organic pollutants in the purified gas does not meet the preset emission requirements, and when toluene is contained in the organic pollutants, the preset emission requirement for toluene is 19.5 - 48.7 ppb, preferably 19.5 - 29.2 ppb, and / or when formaldehyde is contained in the organic pollutants, the preset emission requirement for formaldehyde is 23.8 - 59.7 ppb, preferably 23.8 - 35.9 ppb.

4. The method according to claim 1 or 2, characterized in that Control the volume concentration of oxygen in the reactor to be 5% - 10%.

5. The method according to claim 3, wherein When toluene is contained in the organic pollutants, the reaction start temperature is 150 - 165 °C, or when formaldehyde is contained in the organic pollutants, the reaction start temperature is 105 - 120 °C.

6. The method according to claim 1 or 5, characterized in that, When gradually heating and controlling the temperature, when toluene is contained in the organic pollutants, preferably three-stage heating and temperature control are adopted. The first stage is heated to 150 - 165 °C and maintained for 3 - 7 minutes, the second stage is heated to 195 - 210 °C and maintained for 3 - 7 minutes, and the third stage is heated to 245 - 260 °C and maintained for 3 - 7 minutes; preferably, the temperature rise rate to the first-stage reaction temperature is 15 - 25 °C / min, and the temperature rise rates to the second and third stages are 5 - 12 °C / min.

7. The method according to claim 1 or 5, characterized in that When heating step by step and controlling the temperature, when formaldehyde is contained in the organic pollutants, it is preferably to adopt two-stage heating and temperature control. The first stage is heated to 105-120 °C and maintained for 3-7 minutes, and the second stage is heated to 155-175 °C and maintained for 3-7 minutes; preferably, the temperature rise rate to the first-stage reaction temperature is 15-25 °C / min, and the temperature rise rate to the second stage is 5-12 °C / min.

8. The method according to claim 1, 6 or 7, characterized in that A sandwich heat exchanger is arranged in the adsorption oxidant bed layer and the catalytic oxidation catalyst bed layer, and the sandwich heat exchanger uses a phase change material with a melting or vaporization temperature in the reaction temperature range to maintain the bed layer temperature.

9. The method according to claim 1, wherein The adsorption oxidant bed layer is filled with an adsorption oxidant, which has the functions of chemically adsorbing organic pollutants and catalytically oxidizing organic pollutants at the same time.

10. The method according to claim 9, wherein The adsorption oxidant includes a carrier and an active metal, wherein the carrier is at least one porous material selected from titanium dioxide, alumina and molecular sieves (such as Beta zeolite, Y zeolite), and the active metal is at least one of Cu, Ag, Co and Mn; the mass content of the active metal in the catalyst is 2%-10%.

11. The method according to claim 1, characterized in that, The catalytic oxidation catalyst bed layer is filled with a catalytic oxidation catalyst, including a carrier and an active component. The carrier is a molecular sieve (preferably at least one selected from Y zeolite, Beta zeolite, X-type zeolite, ZSM-5 zeolite or ZSM-11 zeolite), and the active component is a noble metal (preferably at least one selected from Pd, Pt, Ru, Ag); preferably, based on the mass of the catalyst, the mass content of the carrier is 99.0%-99.5%, and the mass content of the active component calculated as an element is 0.5%-1.0%.

12. The method according to claim 1, wherein The volume ratio of the catalyst filled in the adsorption oxidant bed layer to the catalyst filled in the catalytic oxidation catalyst bed layer is 5-10:1.

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