Drying tail gas treatment method for diuron production

Abstract

The invention belongs to the technical field of tail gas treatment, and particularly relates to a treatment method for drying tail gas in diuron production. According to the method, firstly, the diuron production drying tail gas is pretreated, dust and part of impurities are removed, then the methylbenzene in the tail gas is efficiently captured under the conditions of optimized temperature, pressure and air speed by means of the high specific surface area, the rich pore structure and the specific adsorption capacity to the methylbenzene of the core-shell adsorbent, the purification efficiency is remarkably improved, and the purification effect is good. The adsorbed toluene is quickly and thoroughly desorbed by utilizing a microwave-steam synergistic desorption technology, and can be directly returned to a diuron production system for recycling after being condensed and separated, so that the environmental pollution caused by toluene emission is reduced, and the consumption of raw materials is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of tail gas treatment, and in particular relates to a method for treating drying tail gas used in diuron production. Background Art

[0002] Diuron, also known as Diuron in English, is a urea-replacing herbicide developed by DuPont in the United States. It has systemic and contact effects, primarily absorbed by the root system. It is primarily used to control annual grass weeds and certain broadleaf weeds in dryland crops such as cotton, soybeans, corn, peanuts, sugarcane, fruit trees, tea trees, and rubber trees. It also has good control effects on perennial weeds such as dogwood and cyperus. Diuron is traditionally dried using a flash evaporation process using toluene as the solvent. The exhaust gas contains toluene vapor (boiling point 110.6°C), water vapor, and trace amounts of diuron dust.

[0003] Toluene is a toxic and hazardous chemical with a pungent odor. Long-term contact or inhalation can cause damage to the human respiratory system and nervous system, and it is included in the list of VOCs that are subject to key control in my country. At the same time, toluene is flammable and explosive. Direct emission into the atmosphere will not only cause serious environmental pollution, but also pose a safety hazard. At present, the main industrial treatment methods for toluene-containing tail gas include adsorption, catalytic combustion, absorption, condensation, etc. Among them, adsorption has become a common technology for treating low- and medium-concentration VOCs due to its simple operation and relatively low cost. Commonly used adsorbents include activated carbon, molecular sieves, activated carbon fibers, etc. However, the existing technology has the following deficiencies: (1) Imperfect pretreatment: If the dust contained in the tail gas of diuron drying is not completely removed, it will clog the pores of the adsorbent, reducing the adsorption efficiency and service life; at the same time, the tail gas temperature fluctuates greatly, and directly entering the adsorption system will affect the adsorption capacity of the adsorbent (high temperature can easily cause toluene to desorb). (2) Limitations of adsorbent performance: Traditional adsorbents (such as activated carbon) have weak selective adsorption capacity for toluene and are easily affected by moisture or other impurities in the exhaust gas. They also have limited adsorption capacity, and frequent regeneration increases operating costs. Some adsorbents are difficult to regenerate (such as thermal desorption, which consumes a lot of energy and takes a long time), resulting in low toluene recovery efficiency and difficulty in recycling. (3) Defects in desorption and recovery technology: Traditional desorption methods (such as hot air desorption and steam desorption) have problems such as high energy consumption, incomplete desorption, and difficulty in separating toluene from the desorption medium. These problems not only waste resources, but may also cause the adsorbent performance to decay too quickly due to incomplete desorption. Existing technologies have obvious shortcomings in balancing purification efficiency, resource recovery, and energy consumption control.

[0004] Based on this, it is urgent to develop a method for treating drying tail gas from diuron production to solve the above technical problems. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for treating drying tail gas from diuron production in order to solve the existing problems.

[0006] The present invention is achieved through the following technical solutions:

[0007] A method for treating drying tail gas from diuron production, comprising the following steps:

[0008] After pretreatment, the tail gas of diuron drying is heated at a temperature of 23-27°C, a pressure of 0.1-0.15 MPa, and an air velocity of 1800-2200 h -1 Under the condition of , the adsorption area filled with adsorbent is passed to selectively adsorb the toluene in the tail gas, and then microwave-steam is used for desorption and recovery;

[0009] The adsorbent is a core-shell adsorbent.

[0010] Furthermore, the pretreatment is specifically as follows: the tail gas dried with diuron is first cooled to 35~40°C using a plate heat exchanger, the cooled tail gas is introduced into a 5μm metal sintered membrane filter, and filtered under the conditions of 10~15°C, inlet and outlet pressure difference 3~5kPa, and tail gas surface flow rate 0.08~0.12m / s to remove dust with a particle size ≥5μm and then the filtered tail gas is cooled to -5~0°C for condensation treatment.

[0011] Furthermore, the preparation of the core-shell adsorbent comprises the following steps:

[0012] (1) Cr(NO3)3·9H2O and terephthalic acid were dissolved in deionized water, and then formic acid and glucose were added. After ultrasonic dispersion for 20-30 min, solar-assisted microwave heating was used at 140-145°C for 4-5 h. After the reaction, the product was separated by ceramic membrane microfiltration, washed with deionized water, and dried by supercritical CO2 to obtain the core.

[0013] (2) The core and Fe3O4@C were mixed in a mass ratio of 4:1, 2 wt% anhydrous ethanol was added, and the mixture was ball milled for 2-3 h. The ball milled product was treated with low-temperature plasma and then used for later use.

[0014] (3) Place the core treated in step (2) at the bottom of the crystallization kettle, place the silicon source-template mixture on the top, and crystallize at 150-160°C for 18-22 hours;

[0015] (4) The crystallized product is first treated with amylase for 8-10 hours to decompose part of the template, and then calcined at 470-500 °C to completely remove the template.

[0016] Furthermore, the Cr(NO3)3·9H2O:terephthalic acid:formic acid:deionized water in step (1) is 1:1.2:2:200;

[0017] The added amount of glucose is 1-1.2 wt%;

[0018] The power of the solar-assisted microwave heating is 500-600W;

[0019] The pore size of the ceramic membrane is 0.1 μm;

[0020] The conditions for supercritical CO2 drying are 10MPa and 45~50℃.

[0021] Furthermore, the preparation of Fe3O4@C in step (2) comprises the following steps:

[0022] a. Add 0.2M FeCl3 solution and 0.1M FeCl2 solution in a volume ratio of 2:1 to a four-necked flask. Under nitrogen protection, stir at 300-500 rpm for 10-15 minutes, increase the stirring speed to 800-900 rpm, and add concentrated ammonia solution (1 / 5 of the total volume of FeCl3 solution and FeCl2 solution) at this stirring speed. Raise the temperature to 80-85°C and continue the reaction for 1-1.5 hours.

[0023] b. After the reaction is completed, cool to room temperature, separate the black product with a magnet, wash with deionized water and anhydrous ethanol until neutral, and then dry in a vacuum at 60-70°C for 10-12h to obtain Fe3O4 nanoparticles;

[0024] c. Add Fe3O4 nanoparticles and sucrose in a mortar at a mass ratio of 1:3 and grind thoroughly. Then transfer the mixture to a quartz crucible and place it in a microwave reactor. Irradiate the mixture at 5 kW under a nitrogen atmosphere for 5-7 minutes. After cooling to room temperature, wash with deionized water 2-4 times and vacuum dry at 55-65°C for 8-10 hours.

[0025] Furthermore, the rotation speed of the ball mill in step (2) is 300-400 rpm;

[0026] The power of low-temperature plasma treatment is 80~100W, and the treatment time is 6~10min.

[0027] Furthermore, the preparation of the silicon source-template mixture described in step (3) comprises the following steps:

[0028] a. Calcinate rice husk ash at 450-550°C for 2-3 hours, then add the calcined rice husk ash to a 2 mol / L NaOH solution at a solid-liquid ratio of 1 g:10-15 mL. Heat to 80-85°C and stir until completely dissolved to obtain a sodium silicate solution. Adjust the pH of the solution to 9.0 with 1 mol / L citric acid, let stand for 30-40 minutes, and filter to obtain a clear rice husk ash SiO2 solution for later use.

[0029] b. Add the TPAOH solution to deionized water, stir at 200-300 rpm for 5-10 minutes, then add ethanolamine and continue stirring for 10-15 minutes to obtain a template premix.

[0030] wherein the TPAOH (tetrapropylammonium hydroxide) solution is a 25 wt% aqueous solution;

[0031] c. The rice husk ash SiO2 solution obtained in step a is placed in a constant pressure dropping funnel and added to the template mixture at a rate of 1 drop / s under a stirring speed of 300-400 rpm. After the addition is completed, the temperature is raised to 40-45°C, and the stirring is continued for 2-2.5 hours. After stopping the heating, the mixture is placed in a constant temperature water bath at 25-27°C and allowed to stand for 10-12 hours to form a stable silicon source-template mixture;

[0032] The SiO2:TPAOH:ethanolamine:H2O=1:0.08:0.05:35.

[0033] Furthermore, during the amylase treatment in step (4), the concentration of amylase is 50-60 U / mL, the temperature is 50-60° C., and the pH is 6.5.

[0034] Furthermore, the microwave-steam synergistic desorption and recovery is specifically as follows: pulsed microwaves with a frequency of 2.45 GHz and a power of 4 to 6 kW are introduced into the adsorption area to instantly heat the Fe3O4@C in the adsorbent to 75 to 85°C; after microwave activation, saturated steam with a pressure of 0.08 to 0.12 MPa is immediately injected into the adsorption area, and the steam flow rate is 15 to 25% of the pre-treated tail gas flow rate, carrying the desorbed toluene into the condensation area; the steam-toluene mixture is cooled to 5 to 10°C for condensation, and liquid toluene and water are separated and obtained, and the recovered liquid toluene is returned to the diuron production system for recycling after liquid separation treatment.

[0035] Compared with the prior art, the present invention has the following advantages:

[0036] The present invention first pre-treats the drying tail gas from the production of diuron to remove dust and some impurities, and then utilizes the high specific surface area, rich pore structure and specific adsorption capacity of the core-shell adsorbent to capture toluene in the tail gas under optimized temperature, pressure and space velocity conditions, thereby significantly improving the purification efficiency. The microwave-steam synergistic desorption technology is then utilized to achieve rapid and thorough desorption of the adsorbed toluene, which can be directly returned to the diuron production system for recycling after condensation and separation, thereby reducing environmental pollution caused by toluene emissions and lowering raw material consumption. DETAILED DESCRIPTION

[0037] In order to further explain the present invention, it is described below with reference to the following specific embodiments.

[0038] Example 1

[0039] A method for treating drying tail gas from diuron production, comprising the following steps:

[0040] S1. Cool the tail gas of diuron drying to 35°C using a plate heat exchanger, introduce the cooled tail gas into a 5μm metal sintered membrane filter, and filter it at 10°C, an inlet and outlet pressure difference of 3kPa, and a tail gas surface velocity of 0.08m / s to remove dust with a particle size of 5μm or more. Then, cool the filtered tail gas to -5°C for condensation.

[0041] S2, at a temperature of 23°C, a pressure of 0.1 MPa, and an airspeed of 1800 h -1 Under the condition of , the adsorption area filled with core-shell adsorbent is introduced to selectively adsorb toluene in the tail gas;

[0042] S3, using microwave-steam synergistic desorption and recovery, a pulsed microwave with a frequency of 2.45 GHz and a power of 4 kW is introduced into the adsorption area to instantly heat the Fe3O4@C in the adsorbent to 75°C; immediately after microwave activation, saturated steam with a pressure of 0.08 MPa is injected into the adsorption area, and the steam flow rate is 15% of the pre-treated tail gas flow rate, carrying the desorbed toluene into the condensation area; the steam-toluene mixture is cooled to 5°C for condensation, and liquid toluene and water are separated. The recovered liquid toluene is returned to the diuron production system for recycling after liquid separation treatment;

[0043] The preparation of the core-shell adsorbent comprises the following steps:

[0044] (1) Cr(NO3)3·9H2O and terephthalic acid were dissolved in deionized water, and then formic acid and glucose (1 wt%) were added. After ultrasonic dispersion for 20 min, solar-assisted microwave heating was used at 500 W and 140 °C for 4 h. After the reaction, the product was separated by microfiltration through a ceramic membrane (pore size of 0.1 μm), washed with deionized water, and dried in supercritical CO2 at 10 MPa and 45 °C to obtain the core.

[0045] The Cr(NO3)3·9H2O: terephthalic acid: formic acid: deionized water = 1:1.2:2:200;

[0046] (2) The core and Fe3O4@C were mixed in a mass ratio of 4:1, 2 wt% anhydrous ethanol was added, and the mixture was ball-milled at 300 rpm for 2 h. The ball-milled product was treated with low-temperature plasma for 6 min and then used. The power of the low-temperature plasma treatment was 80 W.

[0047] (3) The core treated in step (2) is placed at the bottom of the crystallization kettle, and the silicon source-template mixture is placed on the top, and crystallized at 150°C for 18 hours;

[0048] (4) The crystallized product was treated with 50 U / mL amylase (pH 6.5) at 50°C for 8 h to partially decompose the template, and then calcined at 470°C to completely remove the template;

[0049] The preparation of Fe3O4@C comprises the following steps:

[0050] a. A 0.2M FeCl3 solution and a 0.1M FeCl2 solution were added to a four-necked flask in a volume ratio of 2:1. Under nitrogen, the mixture was stirred at 300 rpm for 10 min. The stirring speed was increased to 800 rpm. At this stirring speed, 1 / 5 of the total volume of the FeCl3 solution and the FeCl2 solution was added to the concentrated ammonia solution. The temperature was raised to 80°C and the reaction was continued for 1 h.

[0051] b. After the reaction was completed, the mixture was cooled to room temperature, and the black product was separated by a magnet. The mixture was washed with deionized water and anhydrous ethanol until neutral, and then dried under vacuum at 60 ° C for 102 h to obtain Fe3O4 nanoparticles.

[0052] c. Fe3O4 nanoparticles and sucrose were added to a mortar in a mass ratio of 1:3 and ground thoroughly. The mixture was then transferred to a quartz crucible and placed in a microwave reactor. Irradiated at 5 kW for 5 minutes under a nitrogen atmosphere, cooled to room temperature, washed twice with deionized water, and dried under vacuum at 55°C for 8 hours.

[0053] The preparation of the silicon source-template mixture comprises the following steps:

[0054] a. After calcining the rice husk ash at 450 ° C for 2h, the calcined rice husk ash was added to a 2 mol / L NaOH solution at a solid-liquid ratio of 1g:10mL, heated to 80 ° C, and stirred until completely dissolved to obtain a sodium silicate solution. The pH of the solution was adjusted to 9.0 with 1 mol / L citric acid, allowed to stand for 30min, and filtered to obtain a clear rice husk ash SiO2 solution for later use;

[0055] b. The TPAOH solution was added to deionized water and stirred at 200 rpm for 5 min, and then ethanolamine was added and stirred for 10 min to obtain a template premix;

[0056] wherein the TPAOH (tetrapropylammonium hydroxide) solution is a 25 wt% aqueous solution;

[0057] c. The rice husk ash SiO2 solution obtained in step a was placed in a constant pressure dropping funnel and added dropwise to the template mixture at a rate of 1 drop / s under a stirring speed of 300 rpm. After the addition was complete, the temperature was raised to 40°C and stirred for 2 hours before heating was stopped. The mixture was then placed in a constant temperature water bath at 25°C and aged for 10 hours to form a stable silicon source-template mixture.

[0058] The SiO2:TPAOH:ethanolamine:H2O=1:0.08:0.05:35.

[0059] Example 2

[0060] A method for treating drying tail gas from diuron production, comprising the following steps:

[0061] S1. Cool the tail gas from the drying of diuron to 37°C using a plate heat exchanger. The cooled tail gas is then introduced into a 5μm metal sintered membrane filter and filtered at 12°C, with an inlet and outlet pressure differential of 4kPa and a tail gas surface velocity of 0.1m / s to remove dust particles with a particle size of 5μm or greater. The filtered tail gas is then cooled to -2°C for condensation.

[0062] S2, at a temperature of 25°C, a pressure of 0.13 MPa, and an air velocity of 2000 h -1 Under the condition of , the adsorption area filled with core-shell adsorbent is introduced to selectively adsorb toluene in the tail gas;

[0063] S3, using microwave-steam synergistic desorption and recovery, a pulsed microwave with a frequency of 2.45 GHz and a power of 5 kW is introduced into the adsorption area to instantly heat the Fe3O4@C in the adsorbent to 80°C; immediately after microwave activation, saturated steam with a pressure of 0.1 MPa is injected into the adsorption area, and the steam flow rate is 20% of the pre-treated tail gas flow rate, carrying the desorbed toluene into the condensation area; the steam-toluene mixture is cooled to 7°C for condensation, and liquid toluene and water are separated. The recovered liquid toluene is returned to the diuron production system for recycling after liquid separation treatment;

[0064] The preparation of the core-shell adsorbent comprises the following steps:

[0065] (1) Cr(NO3)3·9H2O and terephthalic acid were dissolved in deionized water, and then formic acid and glucose (1.1 wt%) were added. After ultrasonic dispersion for 25 min, solar-assisted microwave heating was used at 5500 W and 143 °C for 4.5 h. After the reaction, the product was separated by microfiltration through a ceramic membrane (pore size of 0.1 μm), washed with deionized water, and dried under supercritical CO2 at 10 MPa and 47 °C to obtain the core.

[0066] The Cr(NO3)3·9H2O: terephthalic acid: formic acid: deionized water = 1:1.2:2:200;

[0067] (2) The core and Fe3O4@C were mixed in a mass ratio of 4:1, 2 wt% anhydrous ethanol was added, and the mixture was ball milled at 350 rpm for 2.5 h. The ball milled product was treated with low-temperature plasma for 8 min and then used. The power of the low-temperature plasma treatment was 90 W.

[0068] (3) The core treated in step (2) was placed at the bottom of the crystallization kettle, and the silicon source-template mixture was placed on the top, and crystallized at 155°C for 20 hours;

[0069] (4) The crystallized product was treated with 55 U / mL amylase (pH 6.5) at 55°C for 9 h to partially decompose the template, and then calcined at 480°C to completely remove the template;

[0070] The preparation of Fe3O4@C comprises the following steps:

[0071] a. A 0.2M FeCl3 solution and a 0.1M FeCl2 solution were added to a four-necked flask in a volume ratio of 2:1. Under nitrogen, the mixture was stirred at 400 rpm for 12 minutes. The stirring speed was increased to 850 rpm. At this stirring speed, 1 / 5 of the total volume of the FeCl3 solution and the FeCl2 solution was added to the concentrated ammonia solution. The temperature was raised to 83°C and the reaction was continued for 1.2 hours.

[0072] b. After the reaction was completed, the mixture was cooled to room temperature, and the black product was separated by a magnet. The mixture was washed with deionized water and anhydrous ethanol until neutral, and then dried under vacuum at 65 ° C for 11 h to obtain Fe3O4 nanoparticles.

[0073] c. Fe3O4 nanoparticles and sucrose were added to a mortar in a mass ratio of 1:3 and thoroughly ground. The mixture was then transferred to a quartz crucible and placed in a microwave reactor. Irradiated at 5 kW for 6 minutes under a nitrogen atmosphere, cooled to room temperature, washed three times with deionized water, and dried under vacuum at 60°C for 9 hours.

[0074] The preparation of the silicon source-template mixture comprises the following steps:

[0075] a. After calcining the rice husk ash at 500 ° C for 2.5h, the calcined rice husk ash was added to a 2 mol / L NaOH solution at a solid-liquid ratio of 1g:12mL, heated to 82 ° C, and stirred until completely dissolved to obtain a sodium silicate solution. The pH of the solution was adjusted to 9.0 with 1 mol / L citric acid, allowed to stand for 35min, and filtered to obtain a clear rice husk ash SiO2 solution for later use;

[0076] b. The TPAOH solution was added to deionized water and stirred at 250 rpm for 7 min, then ethanolamine was added and stirring was continued for 12 min to obtain a template premix;

[0077] wherein the TPAOH (tetrapropylammonium hydroxide) solution is a 25 wt% aqueous solution;

[0078] c. The rice husk ash SiO2 solution obtained in step a was placed in a constant pressure dropping funnel and added dropwise to the template mixture at a rate of 1 drop / s under a stirring speed of 350 rpm. After the addition was complete, the temperature was raised to 42°C and stirred for 2.2 hours before heating was stopped. The mixture was then placed in a constant temperature water bath at 26°C and aged for 11 hours to form a stable silicon source-template mixture.

[0079] The SiO2:TPAOH:ethanolamine:H2O=1:0.08:0.05:35.

[0080] Example 3

[0081] A method for treating drying tail gas from diuron production, comprising the following steps:

[0082] S1. Cool the tail gas of diuron drying to 40°C using a plate heat exchanger, introduce the cooled tail gas into a 5μm metal sintered membrane filter, and filter it at 15°C, an inlet and outlet pressure difference of 5kPa, and a tail gas surface velocity of 0.12m / s to remove dust with a particle size of 5μm or more. Then, cool the filtered tail gas to 0°C for condensation treatment;

[0083] S2, at a temperature of 27°C, a pressure of 0.15 MPa, and an airspeed of 2200 h -1 Under the condition of , the adsorption area filled with core-shell adsorbent is introduced to selectively adsorb toluene in the tail gas;

[0084] S3, using microwave-steam synergistic desorption and recovery, a pulsed microwave with a frequency of 2.45 GHz and a power of 6 kW is introduced into the adsorption area to instantly heat the Fe3O4@C in the adsorbent to 85°C; immediately after microwave activation, saturated steam with a pressure of 0.12 MPa is injected into the adsorption area, and the steam flow rate is 25% of the pre-treated tail gas flow rate, carrying the desorbed toluene into the condensation area; the steam-toluene mixture is cooled to 10°C for condensation, and liquid toluene and water are separated. The recovered liquid toluene is returned to the diuron production system for recycling after liquid separation treatment;

[0085] The preparation of the core-shell adsorbent comprises the following steps:

[0086] (1) Cr(NO3)3·9H2O and terephthalic acid were dissolved in deionized water, and then formic acid and glucose (1.2 wt%) were added. After ultrasonic dispersion for 30 min, solar-assisted microwave heating was used at 600 W and 145 °C for 5 h. After the reaction, the product was separated by microfiltration through a ceramic membrane (pore size of 0.1 μm), washed with deionized water, and dried under supercritical CO2 at 10 MPa and 50 °C to obtain the core.

[0087] The Cr(NO3)3·9H2O: terephthalic acid: formic acid: deionized water = 1:1.2:2:200;

[0088] (2) The core and Fe3O4@C were mixed in a mass ratio of 4:1, 2 wt% anhydrous ethanol was added, and the mixture was ball-milled at 400 rpm for 3 h. The ball-milled product was treated with low-temperature plasma for 10 min and then set aside. The power of the low-temperature plasma treatment was 100 W.

[0089] (3) The core treated in step (2) was placed at the bottom of the crystallization kettle, and the silicon source-template mixture was placed on the top, and crystallized at 160°C for 22 hours;

[0090] (4) The crystallized product was treated with 60 U / mL amylase (pH 6.5) at 60°C for 10 h to partially decompose the template, and then calcined at 500°C to completely remove the template;

[0091] The preparation of Fe3O4@C comprises the following steps:

[0092] a. A 0.2M FeCl3 solution and a 0.1M FeCl2 solution were added to a four-necked flask in a volume ratio of 2:1. Under nitrogen, the mixture was stirred at 500 rpm for 15 minutes. The stirring speed was increased to 900 rpm. At this stirring speed, 1 / 5 of the total volume of the FeCl3 solution and the FeCl2 solution was added to the concentrated ammonia solution. The temperature was raised to 85°C and the reaction was continued for 1.5 hours.

[0093] b. After the reaction was completed, the mixture was cooled to room temperature, and the black product was separated by a magnet. The mixture was washed with deionized water and anhydrous ethanol until neutral, and then dried under vacuum at 70 ° C for 12 h to obtain Fe3O4 nanoparticles.

[0094] c. Fe3O4 nanoparticles and sucrose were added to a mortar in a mass ratio of 1:3 and ground thoroughly. The mixture was then transferred to a quartz crucible and placed in a microwave reactor. Irradiated at 5 kW for 7 minutes under a nitrogen atmosphere, cooled to room temperature, washed four times with deionized water, and dried under vacuum at 65°C for 10 hours.

[0095] The preparation of the silicon source-template mixture comprises the following steps:

[0096] a. After calcining rice husk ash at 550 ° C for 3 hours, the calcined rice husk ash was added to a 2 mol / L NaOH solution at a solid-liquid ratio of 1g:15mL, heated to 85 ° C, and stirred until completely dissolved to obtain a sodium silicate solution. The pH of the solution was adjusted to 9.0 with 1 mol / L citric acid, allowed to stand for 40 minutes, and filtered to obtain a clear rice husk ash SiO2 solution for later use;

[0097] b. The TPAOH solution was added to deionized water and stirred at 300 rpm for 10 min, then ethanolamine was added and stirred for 15 min to obtain a template premix;

[0098] wherein the TPAOH (tetrapropylammonium hydroxide) solution is a 25 wt% aqueous solution;

[0099] c. The rice husk ash SiO2 solution obtained in step a was placed in a constant pressure dropping funnel and added dropwise to the template mixture at a rate of 1 drop / s under a stirring speed of 400 rpm. After the addition was complete, the temperature was raised to 45°C and stirred for 2.5 hours before heating was stopped. The mixture was then placed in a constant temperature water bath at 27°C and aged for 12 hours to form a stable silicon source-template mixture.

[0100] The SiO2:TPAOH:ethanolamine:H2O=1:0.08:0.05:35.

[0101] Comparative Example 1

[0102] Compared with Example 2, in the preparation of the core-shell adsorbent, the operations of step (3) and step (4) are omitted in this comparative example 1, and the other steps are the same as those in Example 2.

[0103] Comparative Example 2

[0104] Compared with Example 2, in the preparation of the core-shell adsorbent, this comparative example 2 omitted Fe3O4@C, and the other steps were the same as those in Example 2.

[0105] Comparative Example 3

[0106] Compared with Example 2, in Comparative Example 3, the 5 μm filtration and -5°C condensation were omitted in the pretreatment, and the sample was directly subjected to adsorption. The other steps were the same as those in Example 2.

[0107] Comparative Example 4

[0108] Compared with Example 2, the core-shell adsorbent in Comparative Example 4 was replaced with activated carbon (specific surface area 1200m 2 / g), and other steps are the same as in Example 2.

[0109] Performance Testing

[0110] Test conditions: The same initial concentration of diuron was used to dry the tail gas (toluene concentration 500mg / m 3 , containing dust with particle size of 2~10μm), test the toluene removal rate and the service life of the adsorbent (the maximum number of cycles during which the toluene removal rate remains ≥90% after n cycles). Each group of tests was repeated 3 times and the results were averaged.

[0111] The test results are shown in Table 1 below.

[0112] Table 1

[0113] Grouping Toluene removal rate (%) Adsorbent service life (number of cycles) Example 1 96.2 30 Example 2 98.5 35 Example 3 97.8 32 Comparative Example 1 81.3 20 Comparative Example 2 86.5 15 Comparative Example 3 74.8 10 Comparative Example 4 90.2 25

[0114] It can be seen from Table 1 above that, compared with the comparative example, the toluene removal rate and the service life of the adsorbent in Examples 1 to 3 are significantly better than those in the comparative example, indicating that the core-shell adsorbent prepared by the method of the present invention can be combined with the process for treating the drying tail gas of diuron production to continuously and effectively treat the toluene therein.

[0115] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for treating drying tail gas from diuron production, characterized in that: The steps include: After pretreatment, the tail gas of diuron drying is heated at a temperature of 23-27°C, a pressure of 0.1-0.15 MPa, and an air velocity of 1800-2200 h -1 Under the condition of , the adsorption area filled with adsorbent is passed to selectively adsorb the toluene in the tail gas, and then microwave-steam is used for desorption and recovery; The adsorbent is a core-shell adsorbent.

2. A method for treating drying tail gas from diuron production according to claim 1, characterized in that: The pretreatment is specifically as follows: the tail gas dried with diuron is first cooled to 35~40°C using a plate heat exchanger, the cooled tail gas is introduced into a 5μm metal sintered membrane filter, and filtered under the conditions of 10~15°C, an inlet and outlet pressure difference of 3~5kPa, and a tail gas surface flow rate of 0.08~0.12m / s to remove dust with a particle size of ≥5μm, and then the filtered tail gas is cooled to -5~0°C for condensation treatment.

3. The method for treating drying tail gas from diuron production according to claim 1, characterized in that: The preparation of the core-shell adsorbent comprises the following steps: (1) Cr(NO3)3·9H2O and terephthalic acid were dissolved in deionized water, and then formic acid and glucose were added. After ultrasonic dispersion for 20-30 min, solar-assisted microwave heating was used at 140-145°C for 4-5 h. After the reaction, the product was separated by ceramic membrane microfiltration, washed with deionized water, and dried by supercritical CO2 to obtain the core. (2) The core and Fe3O4@C were mixed in a mass ratio of 4:1, 2 wt% anhydrous ethanol was added, and the mixture was ball milled for 2-3 h. The ball milled product was treated with low-temperature plasma and then used for later use. (3) Place the core treated in step (2) at the bottom of the crystallization kettle, place the silicon source-template mixture on the top, and crystallize at 150-160°C for 18-22 hours; (4) The crystallized product is first treated with amylase for 8-10 hours to decompose part of the template, and then calcined at 470-500 °C to completely remove the template.

4. A method for treating drying tail gas from diuron production according to claim 3, characterized in that: Cr(NO3)3·9H2O:terephthalic acid:formic acid:deionized water described in step (1) = 1:1.2:2:200; The added amount of glucose is 1-1.2 wt%; The power of the solar-assisted microwave heating is 500-600W; The pore size of the ceramic membrane is 0.1 μm; The conditions for supercritical CO2 drying are 10MPa and 45~50℃.

5. The method for treating drying tail gas from diuron production according to claim 3, characterized in that: The preparation of Fe3O4@C described in step (2) comprises the following steps: a. Add 0.2M FeCl3 solution and 0.1M FeCl2 solution in a volume ratio of 2:1 to a four-necked flask. Under nitrogen protection, stir at 300-500 rpm for 10-15 minutes, increase the stirring speed to 800-900 rpm, and add concentrated ammonia solution (1 / 5 of the total volume of FeCl3 solution and FeCl2 solution) at this stirring speed. Raise the temperature to 80-85°C and continue the reaction for 1-1.5 hours. b. After the reaction is completed, cool to room temperature, separate the black product with a magnet, wash with deionized water and anhydrous ethanol until neutral, and then dry in a vacuum at 60-70°C for 10-12h to obtain Fe3O4 nanoparticles; c. Add Fe3O4 nanoparticles and sucrose in a mortar at a mass ratio of 1:3 and grind thoroughly. Then transfer the mixture to a quartz crucible and place it in a microwave reactor. Irradiate the mixture at 5 kW under a nitrogen atmosphere for 5-7 minutes. After cooling to room temperature, wash with deionized water 2-4 times and vacuum dry at 55-65°C for 8-10 hours.

6. The method for treating drying tail gas from diuron production according to claim 3, characterized in that: The ball milling speed in step (2) is 300-400 rpm; The power of low-temperature plasma treatment is 80~100W, and the treatment time is 6~10min.

7. The method for treating drying tail gas from diuron production according to claim 3, characterized in that: The preparation of the silicon source-template mixture described in step (3) comprises the following steps: a. Calcinate rice husk ash at 450-550°C for 2-3 hours, then add the calcined rice husk ash to a 2 mol / L NaOH solution at a solid-liquid ratio of 1 g:10-15 mL. Heat to 80-85°C and stir until completely dissolved to obtain a sodium silicate solution. Adjust the pH of the solution to 9.0 with 1 mol / L citric acid, let stand for 30-40 minutes, and filter to obtain a clear rice husk ash SiO2 solution for later use. b. Add the TPAOH solution to deionized water, stir at 200-300 rpm for 5-10 minutes, then add ethanolamine and continue stirring for 10-15 minutes to obtain a template premix. wherein the TPAOH solution is a 25wt% aqueous solution; c. The rice husk ash SiO2 solution obtained in step a is placed in a constant pressure dropping funnel and added to the template mixture at a rate of 1 drop / s under a stirring speed of 300-400 rpm. After the addition is completed, the temperature is raised to 40-45°C, and the stirring is continued for 2-2.5 hours. After stopping the heating, the mixture is placed in a constant temperature water bath at 25-27°C and allowed to stand for 10-12 hours to form a stable silicon source-template mixture; The SiO2:TPAOH:ethanolamine:H2O=1:0.08:0.05:

35.

8. The method for treating drying tail gas from diuron production according to claim 3, characterized in that: During the amylase treatment in step (4), the concentration of amylase is 50-60 U / mL, the temperature is 50-60° C., and the pH is 6.

5.

9. The method for treating drying tail gas from diuron production according to claim 1, characterized in that: The microwave-steam coordinated desorption and recovery process is specifically as follows: pulsed microwaves with a frequency of 2.45 GHz and a power of 4 to 6 kW are introduced into the adsorption area to instantly heat the Fe3O4@C in the adsorbent to 75 to 85°C; after microwave activation, saturated steam with a pressure of 0.08 to 0.12 MPa is immediately injected into the adsorption area, and the steam flow rate is 15 to 25% of the pre-treated tail gas flow rate, carrying the desorbed toluene into the condensation area; the steam-toluene mixture is cooled to 5 to 10°C for condensation, and liquid toluene and water are separated and obtained; the recovered liquid toluene is returned to the diuron production system for recycling after liquid separation treatment.