Purification method and purification system for gas containing organic pollutants

Abstract

The invention discloses a purification method and a purification system for gas containing organic pollutants. The purification system comprises a reactor, wherein an adsorption oxidant bed layer and a catalytic oxidation catalyst bed layer are sequentially arranged in the reactor from bottom to top; the purification and adsorption gas path is used for enabling gas containing organic pollutants to enter the reactor and discharging purified gas after adsorption and purification out of the reactor; the catalytic oxidation exhaust gas path is used for discharging reaction products of the catalytic oxidation catalyst bed layer out of the reactor; the nitrogen protection gas path is used for filling nitrogen into the reactor and controlling the oxygen concentration in the reactor; the circulating gas path is used for external circulation of gas in the reactor; and the bed temperature control system is used for adjusting the temperatures of the adsorption oxidant bed and the catalytic oxidation catalyst bed. When the purification system is used for treating the gas containing the organic pollutants, in-situ adsorption and oxidation reaction can be realized under the condition that the intrinsic safety of the reactor can be ensured, the problem that the adsorbed organic pollutants are not converted due to desorption and the like is effectively avoided, 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 and a purification system 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), 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 operation 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 existing in general indoor gases, the unorganized emissions of VOCs in the industrial park have the characteristics of complex composition and relatively high concentration (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 aimed at conventional indoor toxic and harmful gases, and the adsorption effect on the complex VOCs gas existing in the industrial park is not ideal.

[0003] Another process means is 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 high-efficiency plasma-assisted multi-technology flue gas purification device, which is characterized in that plasma discharge is used as the heat source for the catalytic reaction. The problem is the risk brought by high-voltage discharge during actual application, especially in places with higher safety requirements such as chemical industrial areas.

[0005] CN107789941A discloses a method for microwave-induced adsorption in-situ catalytic oxidation degradation of organic pollutants, which uses microwave heating as the heat source for the catalytic reaction. The problem is that the microwave reactor is large in 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. Using ultraviolet light irradiation as the energy source for catalytic oxidation reaction, the problems are low conversion efficiency, large reactor volume 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 multiple 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 desorbed from 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, still having the problems of low energy efficiency and large space required for equipment.

[0008] CN101314101A discloses a method for purifying air by combining adsorption and in-situ thermal catalytic oxidation regeneration. The method uses a porous material with both adsorption and catalytic functions, and a porous material with 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 so on to realize the purification of air. 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 gas containing organic pollutants, especially VOCs gas in the enclosed area of chemical industrial parks, the present invention provides a purification method and a purification system for gas containing organic pollutants. The method of the present invention can realize 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] In the first aspect of the present invention, a purification system is provided, wherein the purification system includes:

[0011] A reactor, in which an adsorption oxidant bed layer and a catalytic oxidation catalyst bed layer are sequentially arranged from bottom to top;

[0012] A purification 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;

[0013] A catalytic oxidation exhaust gas path for discharging the reaction products of a catalytic oxidation catalyst bed from the reactor;

[0014] A nitrogen protection gas path for filling nitrogen into the reactor to control the oxygen concentration in the reactor;

[0015] A recycle gas path for the external recycle of the gas in the reactor; and

[0016] A bed temperature control system for adjusting the temperatures of the adsorption oxidant bed and the catalytic oxidation catalyst bed.

[0017] Furthermore, an adsorption oxidant is filled in the adsorption oxidant bed, which is used for adsorbing organic pollutants and performing an in-situ oxidation reaction to remove the organic pollutants.

[0018] Furthermore, a catalytic oxidation catalyst is filled in the catalytic oxidation catalyst bed, which is used for catalytically oxidizing organic pollutants.

[0019] Furthermore, the purified 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.

[0020] Furthermore, 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.

[0021] Furthermore, the nitrogen protection gas path includes an inlet gas pipeline entering the reactor, which is arranged at the lower part or the bottom of the reactor.

[0022] Furthermore, the bed temperature control system is used for adjusting 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 quickly switch to the adsorption purification state.

[0023] Furthermore, the outlet of the recycle gas path from the reactor is located above the catalytic oxidation catalyst bed, preferably arranged at the top of the reactor, and the inlet of the recycle gas path into the reactor is located below the adsorption oxidant bed, preferably arranged at the bottom of the reactor. Further, a recycle buffer tank and a recycle pump can also be arranged between the inlet and outlet of the recycle gas path. Among them, the buffer tank is used to prevent the pressure from rising too much when the gas expands due to heat, and the recycle pump is used to provide the power for the gas flow.

[0024] The present invention provides a method for purifying a gas containing organic pollutants, including two working states, wherein:

[0025] 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. When the mass concentration of organic pollutants in the purified gas does not meet the preset emission requirements, or when the total amount of adsorbed organic pollutants reaches 0.02% - 0.30% (preferably 0.08 - 0.16%) of the total mass of the adsorption oxidant bed and the catalytic oxidation catalyst bed, it is switched to the second working state;

[0026] 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, closing the inlets and outlets of the purified adsorption gas path, the catalytic oxidation exhaust gas path, and the nitrogen protection gas path, opening the inlets and outlets of the circulation gas path, starting the external circulation operation of the gas in the reactor, and at the same time controlling the pressure of the reactor, starting the bed temperature control system to heat the adsorption oxidant bed and the catalytic oxidation catalyst bed until the expected reaction temperature. The adsorption oxidant conducts an in-situ catalytic oxidation reaction on the adsorbed organic pollutants. During the above process, the desorbed organic pollutants contact the catalytic oxidation catalyst for catalytic oxidation reaction. After the reaction ends, close the inlets and outlets of the circulation gas path, stop the circulation operation, discharge the purified gas after the reaction from the reactor, and adjust the bed temperature control system to cool the adsorption oxidant bed and the catalytic oxidation catalyst bed to the temperature of the adsorption and purification state, and then switch to the first working state.

[0027] The method of the present invention is applicable to the purification of the gas containing organic pollutants, and is particularly applicable to the purification of VOCs gas in the enclosed area of the chemical industrial park. The organic pollutants can be formaldehyde and benzene series, and the benzene series includes benzene, toluene, xylene, etc. The mass content of benzene series 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.

[0028] Compared with the prior art, the present invention has the following advantages:

[0029] The inventor of the present invention has found through research that by setting up a circulation gas path, controlling the timing of switching 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, the pressure in the reactor is controlled by the buffer tank arranged on the circulation gas path, further ensuring the safety of the reaction stage system in the second working state. Description of the Drawings

[0030] Figure 1 It is a schematic diagram of the purification system of the present invention;

[0031] Among them, the description of the attached drawing reference numerals is as follows:

[0032] A01 - Compressor; A02 - Adsorption oxidant bed; A03 - Catalytic oxidation catalyst bed; A04 - Heat exchanger; A05 - Heat exchanger; A06 - Circulation buffer tank; A07 - Circulation pump; C01 - Outlet of purified gas after adsorption; C02 - Outlet of purified gas after reaction; C03 - Air inlet. Specific embodiments

[0033] The present invention will be described in detail below with reference to the accompanying drawings and embodiments.

[0034] As Figure 1 shown, the purification system of the present invention includes:

[0035] A reactor, in which an adsorption oxidant bed A02 and a catalytic oxidation catalyst bed A03 are sequentially arranged from bottom to top; the reactor is a fixed bed reactor;

[0036] A purification adsorption gas path, for a gas containing organic pollutants to be introduced into the reactor through a compressor A01 from an air inlet C03, and the purified gas after adsorption and purification is discharged from the reactor through an outlet C01 of the purified gas;

[0037] A catalytic oxidation exhaust gas path, provided with an outlet C02 of the purified gas after reaction, for discharging the oxidation reaction products from the reactor;

[0038] A nitrogen protection gas path (not marked), for filling nitrogen into the reactor to control the oxygen concentration in the reactor;

[0039] A circulation gas path, for the gas in the reactor to be discharged from the upper part of the reactor and then enter the reactor from the lower part for external circulation of the gas, and a circulation buffer tank A06 and a circulation pump A07 are arranged on the circulation gas path;

[0040] A bed temperature control system, for adjusting (such as heating or cooling) the temperatures of the adsorption oxidant bed A02 and the catalytic oxidation catalyst bed A03, for example, it can be realized through heaters in the bed and heat exchange equipment, and the heat exchange equipment is such as Figure 1 the heat exchangers A04 and A05 shown in the figure. In addition, it is also necessary to prevent the bed temperature from rising too fast and control the bed temperature below 450°C.

[0041] The working process of the purification system of the present invention is specifically as follows:

[0042] (1) The first working state, i.e., the adsorption and purification state, includes: The gas containing organic pollutants is introduced into the reactor through the air inlet C03 by the compressor A01. After passing through the adsorption oxidant bed A02 and the catalytic oxidation catalyst bed A03, the purified gas after adsorption and 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. 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, and the emission requirements are 40%-100% of the standard upper limit, further preferably 40%-60% of the standard upper limit. For example, for pollutants in GB / T 18883-2022 "Indoor Air Quality Standard", the requirement for toluene is less than 0.2 mg / m 3 That is, 48.7 ppb, and the requirement for formaldehyde is less than 0.08 mg / m 3 That is, 59.7 ppb. Then the preset emission requirement for toluene is 19.5 - 48.7 ppb, preferably 19.5 - 29.2 ppb, and the preset emission requirement for formaldehyde is 23.8 - 59.7 ppb, preferably 23.8 - 35.9 ppb), or when the total amount of adsorbed organic pollutants reaches 0.02% - 0.30% (preferably 0.08 - 0.16%) of the total mass of the adsorption oxidant bed and the catalytic oxidation catalyst bed, it switches to the second working state; Preferably, when the mass concentration of organic pollutants in the purified gas does not meet the preset emission requirements or the total amount of adsorbed organic pollutants reaches 0.02% - 0.30% (preferably 0.08 - 0.16%) of the total mass of the adsorption oxidant bed and the catalytic oxidation catalyst bed, it switches to the second working state;

[0043] (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%), closing the inlets and outlets of the purified adsorption gas path, the catalytic oxidation exhaust gas path, and the nitrogen protection gas path, opening the inlets and outlets of the circulation gas path, starting the external circulation operation of the gas in the reactor, and at the same time controlling the pressure in the reactor (controlling the pressure of the reactor to be 0.1 - 0.2 MPa), starting the bed temperature control system to heat the adsorption oxidant bed A02 and the catalytic oxidation catalyst bed A03 until the expected reaction temperature. The adsorption oxidant conducts an in-situ catalytic oxidation reaction on the adsorbed organic pollutants. The desorbed organic pollutants in the above process contact the catalytic oxidation catalyst for catalytic oxidation reaction (the organic pollutants are oxidized to CO2 and H2O). After the reaction ends, close the inlets and outlets of the circulation gas path, stop the circulation operation, open the purified gas outlet after the reaction to discharge the purified gas from the reactor, and adjust the bed temperature control system to cool the adsorption oxidant bed and the catalytic oxidation catalyst bed to the temperature of the adsorption and purification state, and then switch to the first working state.

[0044] In the present invention, when the external circulation operation of the gas in the reactor is started, the oxygen content of the gas pre-stored in the circulation gas path is 5% - 10%, and the circulation gas volume is 200 - 2000 h of the bed space velocity. -1 .

[0045] In the present invention, the expected reaction start temperature is set according to the type of organic pollutant. For example, when the organic pollutant is formaldehyde, the expected reaction start temperature is 105 - 125 °C, and when the organic pollutant is toluene, the expected reaction start temperature is 180 - 210 °C. Preferably, the heating rate for heating up to the expected reaction start temperature is controlled at 10 - 25 °C / min.

[0046] In the present invention, during the reaction process, the heating rate of the bed layer is controlled below 10 °C / min, and the bed layer temperature is controlled not to exceed 350 °C.

[0047] In the present invention, when the bed layer cools down naturally, the reaction ends; preferably, when the natural cooling rate of the bed layer is greater than 3 °C / min, preferably greater than 5 °C / min, the reaction ends.

[0048] In the present invention, preferably, from the start of the reaction until the natural heating rate of the bed layer is 0.3 - 1.0 °C / min, the average heating rate of the bed layer is controlled at 1.5 - 7 °C / min, the reaction time is 5 - 30 minutes, and starting from when the natural heating rate of the bed layer is 0.3 - 1.0 °C / min, the reaction continues for another 3 - 12 minutes, and then the reaction ends.

[0049] [ In the present invention, when the heating rate of the bed layer is less than 1 °C / min, the means for reducing the bed layer temperature by cooling is stopped. When the bed layer temperature control system is stopped and no forced temperature adjustment is applied to the bed layer, the temperature rise of the bed layer caused by the reaction is the natural temperature rise of the bed layer, and the natural cooling of the bed layer temperature caused by the end of the reaction is the natural cooling of the bed layer.

[0050] In the present invention, taking toluene as an example of organic pollutants, 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%), closing the inlets and outlets of the purification adsorption gas path, the catalytic oxidation exhaust gas path, and the nitrogen protection gas path, opening the inlets and outlets of the circulation gas path, starting the external circulation operation of the gas in the reactor, and at the same time controlling the pressure in the reactor (controlling the pressure of the reactor to be 0.1-0.2 MPa), starting the bed temperature control system to heat the adsorption oxidant bed A02 and the catalytic oxidation catalyst bed A03, controlling the heating rate to be 15-25 °C / min until the expected reaction start temperature of 180-210 °C, and the adsorption oxidant conducts an in-situ catalytic oxidation reaction on the adsorbed organic pollutants. The desorbed organic pollutants during the above process contact the catalytic oxidation catalyst for a catalytic oxidation reaction (the organic pollutants are oxidized to CO2 and H2O); during the reaction, control the heating rate of beds A02 and A03 to be below 10 °C / min, and control the temperatures of beds A02 and A03 not to exceed 350 °C, preferably not to exceed 300 °C; from the start of the reaction until the natural heating rate of beds A02 and A03 is 0.3-1.0 °C / min, control the average bed heating rate to be 1.5-7 °C / min, and the reaction time is 5-30 minutes; from the time when the natural heating rate of beds A02 and A03 is 0.3-1.0 °C / min (preferably, the reaction temperature at this time is 240-300 °C), after reacting for another 3-7 minutes, the natural cooling rate of beds A02 and A03 is greater than 3 °C / min, preferably greater than 5 °C / min, and the reaction ends. After the reaction ends, close the inlets and outlets of the circulation gas path, stop the circulation operation, open the purified gas outlet after the reaction to discharge the purified gas from the reactor, and adjust 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 switch to the first working state.

[0051] In the present invention, taking formaldehyde, an organic pollutant, as an example, the second working state is the in-situ catalytic oxidation state, which includes: 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%), closing the inlets and outlets of the purification adsorption gas path, the catalytic oxidation exhaust gas path, and the nitrogen protection gas path, opening the inlets and outlets of the circulation gas path, starting the external circulation operation of the gas in the reactor, and at the same time controlling the pressure in the reactor (controlling the pressure of the reactor to be 0.1-0.2 MPa), starting the bed temperature control system to heat the adsorption oxidant bed A02 and the catalytic oxidation catalyst bed A03, controlling the heating rate to be 15-25 °C / min until the expected reaction start temperature of 105-125 °C, and the adsorption oxidant performs an in-situ catalytic oxidation reaction on the adsorbed organic pollutants. The desorbed organic pollutants during the above process contact the catalytic oxidation catalyst for a catalytic oxidation reaction (the organic pollutants are oxidized to CO2 and H2O); during the reaction, the heating rates of beds A02 and A03 are controlled below 10 °C / min, and the temperatures of beds A02 and A03 are controlled not to exceed 250 °C, preferably not to exceed 200 °C; from the start of the reaction until the natural heating rate of beds A02 and A03 is 0.3-1.0 °C / min, the average bed heating rate is controlled at 1.5-5 °C / min, and the reaction time is 5-30 minutes; from when the natural heating rate of beds A02 and A03 is 0.3-1.0 °C / min (preferably, the reaction temperature at this time is 140-180 °C), after reacting for another 3-7 minutes, the natural cooling rate of beds A02 and A03 is greater than 3 °C / min, preferably greater than 5 °C / min, and the reaction ends. After the reaction ends, close the inlets and outlets of the circulation gas path, stop the circulation operation, open the purified gas outlet after the reaction to discharge the purified gas from the reactor, and adjust 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 switch to the first working state.

[0052] 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, where the carrier is at least one porous material among titanium dioxide, alumina, and molecular sieves (such as Beta molecular sieve, Y molecular sieve), 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 room temperature and can catalytically oxidize organic pollutants to carbon dioxide and water at the reaction temperature.

[0053] In the present invention, a catalytic oxidation catalyst bed is filled with a catalytic oxidation catalyst, generally a supported catalyst, which includes a carrier and an active component. The carrier can be a molecular sieve. The active component is a noble metal selected from at least one of Pd, Pt, Ru, and Ag.

[0054] In the present invention, for the 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 in terms of the element is 0.5% - 1.0%.

[0055] In the present invention, in the catalytic oxidation catalyst, the molecular sieve can be selected from at least one of Y molecular sieve, Beta molecular sieve, X-type molecular sieve, ZSM-5 molecular sieve, and ZSM-11 molecular sieve.

[0056] 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.

[0057] The catalytic oxidation catalyst of the present invention can be made into a shaped catalyst according to the reactor size, gas treatment volume, and system pressure drop limit, etc. The shaped catalyst can be an extruded catalyst or can be prepared into a monolithic catalyst, such as coating the catalyst slurry onto a honeycomb ceramic body.

[0058] 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 0.5 - 10:1.

[0059] 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.

[0060] Example 1

[0061] In this example, the adsorption oxidant used is supported on a Beta molecular sieve with 5% Cu and 2.5% Ag by mass fraction, and the catalytic oxidation catalyst is supported on a ZSM-11 molecular sieve with 0.5% Pd. The adsorption oxidant and the catalytic oxidation catalyst are respectively filled in the adsorption oxidant bed and the catalytic oxidation catalyst bed, and the filling volume ratio is 1:1.

[0062] 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 for toluene according to GB / T 18883-2022 "Indoor Air Quality Standard" is 25 ppb.

[0063] The first working state is the adsorption and purification state: the volume of the adsorption bed layer is 5 m 3 , introducing air at a flow rate of 2000 m 3 / h, the average toluene concentration of the gas is 5 ppm, 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;

[0064] The second working state is the in-situ catalytic oxidation state: closing the outlet, introducing 5 m 3 of nitrogen, reducing the oxygen concentration to 10%, closing the inlet, opening the recycle gas path, adjusting the space velocity passing through the bed layer to 500 h -1 , at this time the pressure is 1.1 bar, heating the bed layer temperature to 200 °C at a heating rate of 20 °C / min to start the reaction. During the reaction process, the heating rate of the bed layer temperature is controlled to be less than 10 °C / min by using conventional cold gas heat exchange. From the start of the reaction until the natural heating rate of the bed layer is 1.0 °C / min, the reaction lasts for 20 minutes. At this time, the bed layer temperature is 260 °C. After continuing the reaction for another 10 minutes, the natural cooling rate of the bed layer reaches more than 3 °C / min, and the reaction ends. Closing the recycle gas path, opening the outlet, discharging the purified gas after the reaction, in which the toluene concentration is less than 0.5 ppm, and adjusting the bed layer temperature control system to cool the adsorption oxidant bed layer and the catalytic oxidation catalyst bed layer to room temperature, and then switching to the first working state.

[0065] Example 2

[0066] The adsorption oxidant used in this example is supported on Beta zeolite, loaded with 5% Cu and 2.5% Ag by mass fraction, and the catalytic oxidation catalyst is supported on ZSM-11 zeolite, 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 1:1.

[0067] The raw material gas is the VOCs gas in the closed area of the chemical industrial park, and the average mass concentration of toluene 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.

[0068] The first working state is the adsorption and purification state: the volume of the adsorption bed layer is 5 m 3 , introducing air at a flow rate of 2500 m 3 / h, the average toluene concentration of the gas is 5 ppm, 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;

[0069] The second working state is the in-situ catalytic oxidation state: closing the outlet, introducing 10 m3 Nitrogen is used to reduce the oxygen concentration to 7%. The inlet is closed, and the recycle gas path is opened. The space velocity through the bed is adjusted to 800 h -1 , and the pressure at this time is 1.13 bar. The bed temperature is increased to 200 °C at a heating rate of 20 °C / min to start the reaction. During the reaction process, conventional cold gas heat exchange is used to control the heating rate of the bed temperature to be less than 10 °C / min. From the start of the reaction until the natural heating rate of the bed is 1.0 °C / min, the reaction lasts for 20 minutes. At this time, the bed temperature is 260 °C. After continuing to react for another 5 minutes, the natural cooling rate of the bed reaches more than 3 °C / min, and the reaction ends. The recycle gas path is closed, the outlet is opened, and the purified gas after the reaction is discharged. The toluene concentration is less than 0.5 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 switched to the first working state.

[0070] Example 3

[0071] In this example, the adsorption oxidant uses Y zeolite as the carrier, loaded with 2.5% Co and 2.5% Mn by mass fraction, and the catalytic oxidation catalyst uses ZSM-11 zeolite as the carrier, loaded with 0.5% Pd. The adsorption oxidant and the catalytic oxidation catalyst are respectively filled in the adsorption oxidant bed and the catalytic oxidation catalyst bed, and the filling volume ratio is 1:1.

[0072] The raw material gas is the VOCs gas in the closed area of the chemical industrial park, and the mass concentration of formaldehyde 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.

[0073] The first working state is the adsorption purification state: the volume of the adsorption bed is 5 m 3 , and the air volume is introduced at 2500 m 3 / h. The average formaldehyde concentration of the gas is 10 ppm. After adsorbing for 20 hours, the formaldehyde concentration at the outlet is less than 29 ppb. After 20 hours, the formaldehyde concentration at the outlet reaches 30 ppb, and it is switched to the second working state;

[0074] The second working state is the in-situ catalytic oxidation state: the outlet is closed, and 10 m 3 Nitrogen is used to reduce the oxygen concentration to 7%. The inlet is closed, and the recycle gas path is opened. The space velocity through the bed is adjusted to 800 h -1, at this time the pressure is 1.13 bar. With a heating rate of 10 °C / min, the bed temperature is raised to 120 °C to start the reaction. During the reaction, conventional cold gas heat exchange is used to control the heating rate of the bed temperature to be less than 6 °C / min. From the start of the reaction until the natural heating rate of the bed is 1.0 °C / min, the reaction continues for 20 minutes. At this time, the bed temperature is 150 °C. After continuing the reaction for another 5 minutes, the natural cooling rate of the bed reaches more than 3 °C / min, and the reaction ends. The circulation gas path is closed, the outlet is opened, and the purified gas after the reaction is discharged, in which the formaldehyde concentration is less than 0.5 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 switched to the first working state.

[0075] Comparative Example 1

[0076] In this example, the adsorption oxidant used is based on Beta zeolite as the carrier, loaded with 5% by mass of Cu and 2.5% of Ag, and the catalytic oxidation catalyst is based on ZSM-11 zeolite as the carrier, loaded with 0.5% Pd. The adsorption oxidant and the catalytic oxidation catalyst are respectively filled in the adsorption oxidant bed and the catalytic oxidation catalyst bed, and the filling volume ratio is 1:1.

[0077] The raw material gas is the same as in Example 1.

[0078] The first working state is the adsorption purification state: the volume of the adsorption bed is 5 m 3 , with an air volume of 2000 m 3 / h for air intake. 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;

[0079] The second working state is the in-situ catalytic oxidation state: instead of using the circulation gas path, a mixture of air and pure nitrogen (1:1) is introduced. At the same time, the total air volume is reduced to 200 m 3 / h. With a heating rate of 10 °C / min, the bed temperature is raised to 200 °C to start the reaction. During the reaction, conventional cold gas heat exchange is used to control the heating rate of the bed temperature to be less than 10 °C / min. From the start of the reaction until the natural cooling rate of the bed reaches 3.0 °C / min, the reaction continues for 30 minutes, and the reaction ends. Among them, the average heating rate from the start of the reaction to the 20th minute is 3.0 °C / min. During the reaction, the purified gas after the reaction is continuously discharged. When the toluene concentration peaks, it will fluctuate above 15 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 switched to the first working state.

[0080] Comparative Example 2

[0081] The adsorption oxidant used in this example is supported on Beta zeolite, loaded with 5% by mass of Cu and 2.5% of Ag. The catalytic oxidation catalyst is supported on ZSM-11 zeolite, loaded with 0.5% of 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 1:1.

[0082] The raw material gas is the same as that in Example 1.

[0083] 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;

[0084] The second working state is the in-situ catalytic oxidation state: close the outlet, introduce 5 m 3 of nitrogen gas to reduce the oxygen concentration to 1%. Open the recycle gas path, and the recycle gas path is filled with nitrogen gas to adjust the space velocity passing through the bed layer to 500 h -1 . At this time, the pressure is 1.1 bar. At a heating rate of 10 °C / min, the bed layer temperature is raised to 200 °C to start the reaction. During the reaction process, the heating rate of the bed layer temperature is controlled to be less than 10 °C / min by using conventional cold gas heat exchange. The reaction lasts for 20 minutes. At this time, the bed layer temperature is 205 °C, and the natural cooling rate of the bed layer reaches more than 3 °C / min. The reaction ends. Then close the recycle gas path, open the outlet, and discharge the purified gas after the reaction. The toluene concentration is much greater than 10 ppm (due to insufficient oxygen, incomplete combustion, and the toluene concentration is significantly high). And adjust the bed layer temperature control system to cool the adsorption oxidant bed layer and the catalytic oxidation catalyst bed layer to room temperature, and then switch to the first working state

[0085] Comparative Example 3

[0086] Compared with Example 1, the difference is only that:

[0087] The second working state is the in-situ catalytic oxidation state: close the outlet, introduce 10 m 3 of nitrogen gas to reduce the oxygen concentration to 7%. Close the inlet, open the recycle gas path, and adjust the space velocity passing through the bed layer to 800 h -1, at this time the pressure is 1.13 bar. With a heating rate of 20 °C / min, the bed temperature is raised to 200 °C to start the reaction. During the reaction process, conventional cold gas heat exchange is used to control the heating rate of the bed temperature to be less than 10 °C / min. From the start of the reaction until the natural heating rate of the bed is 1.0 °C / min, the reaction lasts for 20 minutes. At this time, the bed temperature is 260 °C. Then the recycle gas path is closed, the outlet is opened, and the purified gas after the reaction is discharged, in which the toluene concentration is greater than 5 ppm. And the bed temperature control system is adjusted to cool the adsorption oxidant bed and the catalytic oxidation catalyst bed to room temperature, and then switch to the first working state.

Claims

1. A purification system, characterized in that, The purification system includes: a reactor, in which an adsorption oxidant bed layer and a catalytic oxidation catalyst bed layer are sequentially arranged from bottom to top; a purification adsorption gas path for a gas containing organic pollutants to enter the reactor and the purified gas after adsorption purification to be discharged from the reactor; a catalytic oxidation exhaust gas path for the reaction products of the catalytic oxidation catalyst bed layer to be discharged from the reactor; a nitrogen protection gas path for filling nitrogen into the reactor to control the oxygen concentration in the reactor; a circulation gas path for the external circulation of the gas in the reactor; and a bed temperature control system for adjusting the temperatures of the adsorption oxidant bed layer and the catalytic oxidation catalyst bed layer.

2. The purification system according to claim 1, wherein, The adsorption oxidant bed layer is filled with an adsorption oxidant for adsorbing organic pollutants and performing an in-situ oxidation reaction to remove the organic pollutants.

3. The purification system according to claim 1, characterized in that, The catalytic oxidation catalyst bed layer is filled with a catalytic oxidation catalyst for catalytically oxidizing organic pollutants.

4. The purification system according to claim 1, characterized in that, The purification 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; and / or, 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.

5. The purification system according to claim 1, wherein The outlet of the circulation gas path from the reactor is located above the catalytic oxidation catalyst bed layer, preferably arranged at the top of the reactor, and the inlet of the circulation gas path into the reactor is located below the adsorption oxidant bed layer, preferably arranged at the bottom of the reactor; further, a circulation buffer tank and a circulation pump are arranged between the inlet and outlet of the circulation gas path.

6. A method for purifying a gas containing organic pollutants, which includes two working states, wherein: The first working state is the adsorption purification state, including: the gas containing organic pollutants enters the reactor and contacts with 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. When the mass concentration of the organic pollutants in the purified gas does not meet the preset emission requirements, or when the total amount of adsorbed organic pollutants reaches 0.02% - 0.30% (preferably 0.08 - 0.16%) of the total mass of the adsorption oxidant bed layer and the catalytic oxidation catalyst bed layer, 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, closing the inlets and outlets of the purification adsorption gas path, the catalytic oxidation exhaust gas path, and the nitrogen protection gas path, opening the inlets and outlets of the circulation gas path, starting the external circulation operation of the gas in the reactor, controlling the pressure of the reactor at the same time, starting the bed temperature control system to heat the adsorption oxidant bed and the catalytic oxidation catalyst bed until the expected reaction temperature, and the adsorption oxidant conducts in-situ catalytic oxidation reaction on the adsorbed organic pollutants. During the above process, the desorbed organic pollutants contact the catalytic oxidation catalyst for catalytic oxidation reaction. After the reaction ends, close the inlets and outlets of the circulation gas path, stop the circulation operation, discharge the purified gas after the reaction from the reactor, and adjust 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 switch to the first working state.

7. The method according to claim 6, characterized in that The gas containing organic pollutants is the VOCs gas in the enclosed 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 the 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.

8. The method according to claim 6 or 7, characterized in that, When the mass concentration of the organic pollutants in the purified gas does not meet the preset emission requirements or the total amount of adsorbed organic pollutants reaches any one of 0.02% - 0.30% (preferably 0.08 - 0.16%) of the total mass of the adsorption oxidant bed and the catalytic oxidation catalyst bed, switch to the second working state. Preferably, when toluene is contained in the organic pollutants, the preset emission requirement for toluene is 19.5 - 48.7 ppb, preferably 9. The method according to claim 6 or 7, characterized in that, ​ 10. The method according to any one of claims 6-9, characterized in that, ​ 11. The method according to claim 10, characterized in that, ​ 12. The method according to claim 11, wherein ​ 13. The method according to claim 11 or 12, characterized in that, From the start of the reaction until the natural heating rate of the bed layer is 0.3 - 1.0 °C / min, the average heating rate of the bed layer is controlled at 1.5 - 7 °C / min, the reaction time is 5 - 30 minutes. Starting from the natural heating rate of the bed layer being 0.3 - 1.0 °C / min, the reaction proceeds for another 3 - 7 minutes and then the reaction ends.

14. The method according to claim 6 or 7, characterized in that, 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 simultaneously.

15. The method according to claim 6 or 7, characterized in that The adsorption oxidant includes a carrier and an active metal. 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%.

16. The method according to claim 6 or 7, characterized in that, The catalytic oxidation catalyst bed layer is filled with a catalytic oxidation catalyst, which includes 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 in terms of the element is 0.5% - 1.0%.

17. The method according to claim 6 or 7, characterized in that, The volume ratio of the catalysts filled in the adsorption oxidant bed layer to the catalytic oxidation catalyst bed layer is 0.5 - 10:1.

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