Apparatus and method for treating volatile organic gas

Abstract

The present application belongs to the technical field of waste gas treatment, and particularly relates to a kind of volatile organic compound gas grading treatment device, including adsorption container;The adsorption chamber of the adsorption container includes two adsorption zones, respectively, the adsorption zone A filled with large mesoporous adsorbent A and the adsorption zone B filled with small mesoporous adsorbent B;The mesoporous adsorbent A of the large mesoporous adsorbent A is 80-95% or more than the total pore volume of 3-10nm mesoporous;The pore size of the small mesoporous adsorbent B is less than 3nm;The wall of the adsorption zone A is provided with air hole A;The wall of the adsorption zone B is provided with air hole B.In addition, the present application also relates to a method for waste gas adsorption and desorption using the device.The method of adsorption by the device can effectively remove organic compounds from waste gas and improve waste gas treatment efficiency.The system and method have the advantages of simple structure, easy operation, low investment, long adsorbent service life and low energy consumption.

Description

Technical Field

[0001] This invention belongs to the field of chemical and environmental protection technology, and specifically relates to an apparatus and method for treating volatile organic compounds (VOCs). Background Technology

[0002] Chemical production processes are complex, often generating large quantities of waste gas containing organic matter with highly complex compositions. A combination of absorption and adsorption methods is frequently used for treatment. However, absorption is limited by gas-liquid phase equilibrium, restricting its effectiveness. Adsorption primarily utilizes porous adsorbents to bind organic molecules within the pores, allowing the gas to meet emission standards. However, in practice, due to the complexity of gas composition, even after absorption, the gas often retains multiple components with varying molecular weights. Subsequent adsorption treatment with fixed-pore-size adsorbents still limits their adaptability. Specifically, mesoporous adsorbents offer advantages such as easy regeneration and low energy consumption, while microporous adsorbents are frequently clogged by large molecules, making regeneration impossible. This phenomenon has become a common problem in the industry.

[0003] In addition, two methods are typically used during desorption operations. One method involves purging with a small amount of gas during heating. However, because the desorbed organic matter is polluting, this purging gas also becomes volatile organic compounds and must be recycled. Generally, this portion of gas can reach 1 / 10 to 1 / 5 of the original gas processing volume, which is very energy-inefficient. The other method is to create a vacuum during heating, but this method results in a very low heat transfer coefficient in the device, is time-consuming, and consumes a lot of energy. This problem has not been well resolved. Summary of the Invention

[0004] In order to overcome the shortcomings of the existing technology, the first objective of this invention is to provide a graded treatment device for volatile organic compounds (also referred to as the gas to be treated in this invention) (also referred to as the treatment device in this invention), which aims to achieve graded adsorption of volatile organic compounds of different molecular weights and reverse self-reinforcing desorption, thereby improving the adsorption and desorption effects.

[0005] A second objective of this invention is to provide a method for treating volatile organic compounds using the aforementioned apparatus, which aims to improve the adsorption effect of the gas to be treated and improve the stability of the adsorption-desorption cycle.

[0006] A staged treatment device for volatile organic compounds, comprising an adsorption container;

[0007] The adsorption chamber of the adsorption container includes two adsorption zones: adsorption zone A, which is filled with macroporous adsorbent A, and adsorption zone B, which is filled with microporous adsorbent B.

[0008] In the macroporous adsorbent A, mesopores of 3-10 nm account for more than 80-95% of the total pore volume; in the microporous adsorbent B, the pore size is less than 3 nm.

[0009] The adsorption zone A has pores A on its wall; the adsorption zone B has pores B on its wall.

[0010] In the apparatus described in this invention, the gas to be treated enters the adsorption chamber through pore A, is adsorbed sequentially through adsorption zone A and adsorption zone B, and is discharged as purified gas through pore B. In this invention, the adsorbents A and B, with their specific parameter characteristics, are partitioned, and further coordinated by the joint control of the pore structure characteristics of adsorbents A and B. This achieves synergy, facilitating the graded adsorption of gases of different molecular weights within volatile organic compounds (VOCs), improving the adsorption effect and efficiency of VOCs, and also aiding in the desorption of the adsorbed gas, reducing processing steps and energy consumption.

[0011] The adsorption container described in this invention can be a horizontally or vertically positioned container.

[0012] The cross-section of the adsorption container can be circular or square. The material of the container can be stainless steel, tempered glass, or other materials commonly used in the adsorption tower industry.

[0013] In this invention, the partitioning of the macroporous adsorbent A and the microporous adsorbent B with the aforementioned parameter characteristics, and the joint control of their pore structure characteristics, are key to synergistically improving the adsorption and desorption effects.

[0014] Preferably, in the macroporous adsorbent A, mesopores of 3-10 nm account for 90-95% of the total pore volume.

[0015] Preferably, the specific surface area of ​​the macroporous adsorbent A is 200-1500 m². 2 / g.

[0016] Preferably, in the small mesoporous adsorbent B, mesopores with a diameter greater than or equal to 1 nm and less than 3 nm account for 40-60% of the total pore volume, with the remainder being micropores with a diameter greater than or equal to 0.5 nm and less than 1 nm. Studies have found that the combination of adsorbent B with this pore characteristic, adsorbent A, and the aforementioned partitioning method helps to further improve long-term circulation performance.

[0017] Preferably, the materials of the macroporous adsorbents A and B are at least one of carbon, silicon dioxide, and aluminum oxide.

[0018] Preferably, there are no special requirements for the particle size of the mesoporous adsorbents A and B. For example, the D50 particle size of both can be 0.1-1 cm.

[0019] In this invention, the loading amount of macroporous adsorbent A in the loading chamber can be adjusted as needed. For example, the loading volume ratio of macroporous adsorbent A in the loading chamber is 20-80%; preferably 40-60%.

[0020] In this invention, adsorption zone A and adsorption zone B are separated by a porous plate with pores. The porous plate can retain the adsorbent while allowing gas to pass through.

[0021] Preferably, the device further includes a heat exchange device for controlling the temperature of adsorption zone A and adsorption zone B.

[0022] Preferably, the device further includes a three-way airflow valve, wherein the first port of the three-way valve is connected to the air port A, the second port is connected to the gas to be treated, and the third port is connected to the desorbed gas storage tank. Alternatively, the wall of the adsorption zone A of the device is also provided with air ports C for discharging the desorbed gas.

[0023] The device described in this invention can achieve adsorption-desorption cycles in two ways. One method involves using a three-way valve to switch between adsorption and desorption. During adsorption, the gas to be treated enters the adsorption chamber through the connecting gas path of the second port of the three-way valve (port A), undergoes staged adsorption in adsorption zones A and B within the chamber, and is then discharged through port B. During desorption, port B is closed, adsorption zones A and B are heated, and the desorbed gas in adsorption zone B flows countercurrently to purge adsorption zone A. The desorbed gas is then discharged through the connecting pipeline of port A and the third port of the three-way valve. Another embodiment of this invention involves providing a vent C on the wall of adsorption zone A. During adsorption, vent C is closed, and the gas to be treated enters the adsorption chamber through vent A for staged adsorption, and is discharged as purified gas through vent B. During desorption, vents A and B are closed, vent C is opened, and desorbed gas is discharged through vent C.

[0024] The preferred processing apparatus of this invention comprises a region filled with macroporous adsorbent (adsorption zone A), a region filled with microporous adsorbent (adsorption zone B), a porous plate separating the two regions, heat exchange tubes disposed in the two regions, a gas inlet (pore A), and two gas outlets (pore B and pore C, used for adsorption and desorption, respectively). The heat exchange tubes are connected to the cylindrical wall of the apparatus. In the macroporous adsorbent, mesopores of 3-10 nm account for 80-95% of the total pore volume, and the specific surface area is 200-1500 m². 2 / g, the materials are carbon, silicon dioxide, and aluminum oxide. In this small mesoporous adsorbent, mesopores (≥1 nm < 3 nm) account for 40-60% of the total pore volume, and micropores (≥0.5 nm < 1 nm) account for 40-60% of the total pore volume. Specific surface area is 1200-2500 m². 2 / g, the materials are carbon, silicon dioxide and aluminum oxide.

[0025] The present invention also provides a method for treating volatile organic compounds using the aforementioned staged treatment device, comprising a staged adsorption step:

[0026] The volatile organic compound gas to be treated enters the adsorption chamber of the device through pore A, and flows sequentially through adsorption zone A and adsorption zone B. In adsorption zone A, high molecular weight gases are selectively adsorbed, and in adsorption zone B, low molecular weight gases are selectively adsorbed. The purified gas is then discharged through pore B.

[0027] This invention has found that, by utilizing the aforementioned device and based on the combined control of the adsorbent partitioning and pore structure of the adsorbent in adsorption zones A and B, high molecular weight gases can be selectively adsorbed in adsorption zone A, and low molecular weight gases can be selectively adsorbed in adsorption zone B. This helps to achieve partitioned adsorption of gases with different molecular weights, thereby improving the adsorption effect and efficiency.

[0028] In this invention, the temperature of the staged adsorption phase is less than or equal to 30°C, preferably -5 to 20°C.

[0029] In this invention, the high molecular weight gas is C6-C. 12 Organic compounds; preferably at least one of hydrocarbons, alcohols, esters, amines, thiols, ketones, and thioethers having the number of carbon atoms mentioned above;

[0030] Preferably, the concentration of high molecular weight gases in the volatile organic compound gas to be treated is 500-2000 mg / m³. 3 ;

[0031] Preferably, the low molecular weight gas is a C3-C5 organic compound, preferably at least one of hydrocarbons, alcohols, esters, amines, and ethers with the specified number of carbon atoms;

[0032] Preferably, the concentration of low molecular weight gases in the volatile organic compound gas to be treated is 500-2000 mg / m³. 3 ;

[0033] Preferably, the pressure of the volatile organic compound gas to be treated is 0.1-2 MPa.

[0034] The processing method of the present invention further includes a countercurrent desorption step: closing pore B, heating and desorbing adsorption zones A and B, using the desorption gas from adsorption zone B to purge adsorption zone A to assist thermal desorption, and discharging and collecting the thermal desorption gas from the pores (such as pore A and / or pore C) of adsorption zone A.

[0035] This invention has discovered that, under the aforementioned staged adsorption, thermal desorption can preferentially desorb the gas in adsorption zone B, and further utilize this desorbed gas to countercurrently purge adsorption zone A, assisting in the thermal desorption of adsorption zone A. This invention also finds that utilizing countercurrent thermal desorption can improve the desorption effect and efficiency, increase the concentration of the desorbed gas, without increasing the total amount of pollutants, and contribute to improving desorption efficiency and reducing energy consumption.

[0036] Preferably, the adsorption zones A and B are heated to a temperature of 140-200℃.

[0037] The preferred processing method of the present invention includes the following steps:

[0038] (1) Using the device, a cooling medium is introduced into the heat exchange tube to keep the device temperature between -5 and 20°C.

[0039] (2) Volatile organic compounds are introduced into the device through the gas inlet (pore A, during adsorption). The gas first passes through the area filled with large mesoporous adsorbent (adsorption zone A) to retain larger molecular weight organic compounds while preventing the adsorption of smaller molecular weight organic compounds. Then, it passes through the area filled with small mesoporous adsorbent (adsorption zone B) to retain smaller molecular weight organic compounds. Finally, the gas exits the device through the gas outlet (during adsorption) and is discharged in compliance with emission standards.

[0040] (3) During the desorption operation, close the gas inlet (during adsorption) and gas outlet (during adsorption) 8 of the device, and open the gas outlet (during desorption). Empty the cooling medium from the heat exchange tubes; introduce a high-temperature medium into the heat exchange tubes to maintain the device temperature at 140-200℃. This causes the organic matter adsorbed on the small mesoporous adsorbent to evaporate, forming a purge gas, which, combined with the high temperature, blows off the organic matter adsorbed on the large mesoporous adsorbent. The desorbed gas exits the device from the gas outlet (desorption). After desorption is complete, resume the adsorption operation to continue processing volatile organic compounds.

[0041] (4) Use two identical devices, one in the adsorption operation and the other in the desorption operation, so that the process is continuous.

[0042] (5) The desorbed volatile organic compounds are concentrated and further processed.

[0043] The method described in this invention involves a device filled with two types of adsorbents with different pore sizes. One type adsorbs only large-molecule organic compounds and has no interception effect on small-molecule organic compounds. The other type of adsorbent specifically absorbs small-molecule organic compounds. Simultaneously, by adjusting the gas flow direction during desorption, the small-molecule organic compounds that are desorbed first act as purge gas, thereby improving the heat transfer coefficient of the device without increasing the total amount of pollutants, resulting in energy savings.

[0044] In the preferred method of this invention, the gas to be treated is one or more of nitrogen, hydrogen, CO2, CO, Ar, He, etc., wherein the high molecular weight organic compound is C6-C. 12 Organic compounds, including but not limited to hydrocarbons, alcohols, esters, amines, thiols, ketones, thioethers, etc., at a concentration of 500-2000 mg / m³. 3 Low molecular weight organic compounds are C3-C5 organic compounds, including but not limited to hydrocarbons, alcohols, esters, amines, ethers, etc., with a concentration of 500-2000 mg / m³. 3 The gas pressure is 0.1-2 MPa. The cooling medium is liquid ammonia, ice-salt water, or cooling water; the high-temperature medium is steam or flue gas.

[0045] Compared with existing technologies, the beneficial effects of the present invention are as follows:

[0046] (1) Using a special large mesoporous adsorbent that cuts off large molecular weight organic matter reduces the burden and deactivation probability of small mesoporous adsorbents, and extends the regeneration cycle of small mesoporous adsorbents by 50-80%.

[0047] (2) Using the desorbed small molecular weight organic matter as purge gas increases the heat transfer coefficient of the device by 5-20 times, shortens the desorption time by 20-30%, and reduces energy consumption by 20-40%. Attached Figure Description

[0048] Figure 1 Devices for treating volatile organic compounds

[0049] The components are: 1. the cylindrical body of the device; 2. the area filled with large mesoporous adsorbent; 3. the area filled with small mesoporous adsorbent; 4. the porous plate; 5. and 6. the heat exchange tubes; 7. the gas inlet (during adsorption); 8. the gas outlet (during adsorption); and 9. the gas outlet (during desorption).

[0050] Figure 2 Comparative apparatus for treating volatile organic compounds

[0051] Among them, 1. heat exchange tube; 2. region filled with large mesoporous adsorbent; 3. region filled with small mesoporous adsorbent; 4. gas inlet; 5. gas outlet 1; 6. gas inlet 2; 7. desorption gas outlet of region 3; 8. desorption gas outlet of region 4. Detailed Implementation

[0052] The present invention will now be described in detail with reference to the embodiments.

[0053] In the following cases, there are no special requirements for the median particle size of the adsorbent, for example, 0.3-0.5 cm.

[0054] Example 1

[0055] The large mesoporous adsorbent (material is carbon, with mesopores of 3-10 nm accounting for 90% of the total pore volume, and a specific surface area of ​​200 m²) is used. 2 / g) is filled into region 2 of the device and pressed down with a porous plate 4; then, a small mesoporous adsorbent (material is carbon, with mesopores greater than or equal to 1 nm and less than 3 nm accounting for 50% of the total pore volume, and micropores greater than or equal to 0.5 nm and less than 1 nm accounting for 50% of the total pore volume. Specific surface area is 2500 m²) 2 / g) is filled in region 3 of the device to form a fully functional device; wherein, the filling ratio of macroporous adsorbent is 20%.

[0056] Cooling medium (liquid ammonia) is introduced into heat exchange tubes 5 and 6 to maintain the device temperature at -5°C. Volatile organic compounds (primarily a mixture of nitrogen and hydrogen in any proportion, with high molecular weight organic compounds being C6-C6) are then introduced. 12 Hydrocarbons and alcohols, at concentrations of 250 mg / m³. 3 and 250 mg / m 3 Low molecular weight organic compounds are C3-C5 organic compounds, including hydrocarbons, amines, ethers, etc., with concentrations of 500, 500, and 1000 mg / m³, respectively. 3 The gas (at a pressure of 0.1 MPa) enters the device through gas inlet 7, first passing through region 2 filled with large mesoporous adsorbent to retain larger molecular weight organic compounds while not adsorbing smaller molecular weight organic compounds. Then it passes through region 3 filled with small mesoporous adsorbent to retain smaller molecular weight organic compounds. Finally, the gas exits the device through gas outlet 8, meeting emission standards.

[0057] During desorption, gas inlet 7 and gas outlet 8 are closed, while gas outlet 9 is opened. The cooling medium (liquid ammonia) in the heat exchange tubes is purged; a high-temperature medium (steam) is introduced into the heat exchange tubes to maintain the device temperature at 140°C. This causes the organic matter adsorbed on the small mesoporous adsorbent to evaporate, forming a purge gas. This purge gas, combined with the high temperature, removes the organic matter adsorbed on the large mesoporous adsorbent. The desorbed gas exits the device from gas outlet 9. After desorption is complete, adsorption operation is resumed to continue treating volatile organic compounds. Two identical devices are used, one in adsorption operation and the other in desorption operation, to ensure a continuous process.

[0058] Each adsorption cycle lasts 20–20.5 hours, and the desorption cycle lasts 2–2.5 hours. The desorbed volatile organic compounds are concentrated and undergo further treatment. After 500 hours of operation, the organic compound content in the treated gas is detected to be 8 mg / m³.

[0059] Example 2

[0060] The large mesoporous adsorbent (made of silica, with mesopores of 3-10 nm accounting for 90% of the total pore volume and a specific surface area of ​​1500 m²) is used. 2 / g) is filled into region 2 of the device and pressed down with a porous plate 4; then, a small mesoporous adsorbent (material is alumina, in which mesopores greater than or equal to 1 nm and less than 3 nm account for 50% of the total pore volume, and micropores greater than or equal to 0.5 nm and less than 1 nm account for 50% of the total pore volume. Specific surface area is 1200 m² / g) 2 / g) is filled in region 3 of the device to form a fully functional device, wherein the filling ratio of macroporous adsorbent is 70%.

[0061] Cooling medium (cooling water) is introduced into heat exchange tubes 5 and 6 to maintain the device temperature at 20°C. Volatile organic compounds (primarily a mixture of CO2 and CO in any proportion, with high molecular weight organic compounds being C6-C) are then introduced. 10 Esters, amines, thiols, and thioethers, at concentrations of 500, 500, 500, 500 mg / m³ 3 The low molecular weight organic compounds are C3-C5 esters, amines, ethers, etc., with concentrations of 100, 200, and 200 mg / m³. 3 The gas (at a pressure of 2 MPa) enters the device through gas inlet 7, first passing through region 2 filled with large mesoporous adsorbent to retain larger molecular weight organic compounds while not adsorbing smaller molecular weight organic compounds. Then it passes through region 3 filled with small mesoporous adsorbent to retain smaller molecular weight organic compounds. Finally, the gas exits the device through gas outlet 8, meeting emission standards.

[0062] During desorption, the gas inlet 7 and gas outlet 8 of the apparatus are closed, while the gas outlet 9 is opened. The cooling medium (cooling water) in the heat exchange tubes is purged; a high-temperature medium (flue gas) is introduced into the heat exchange tubes to maintain the apparatus temperature at 200°C. This causes the organic matter adsorbed on the small mesoporous adsorbent to evaporate, forming a purge gas. This purge gas, combined with the high temperature, strips the organic matter adsorbed on the large mesoporous adsorbent. The desorbed gas exits the apparatus from gas outlet 9. After desorption is complete, the adsorption operation is resumed to continue treating volatile organic compounds. Two identical apparatuses are used, one in adsorption operation and the other in desorption operation, to ensure a continuous process.

[0063] Each adsorption cycle lasts 20–20.5 hours, and the desorption cycle lasts 2–2.5 hours. The desorbed volatile organic compounds are concentrated and undergo further treatment. After 500 hours of operation, the organic compound content in the treated gas was measured at 12 mg / m³.

[0064] Example 3

[0065] The large mesoporous adsorbent (material is carbon, with mesopores of 3-10 nm accounting for 90% of the total pore volume, and a specific surface area of ​​1500 m²) is used. 2 / g) is filled into region 2 of the device and pressed down with a porous plate 4; then, a small mesoporous adsorbent (material is alumina, in which mesopores greater than or equal to 1 nm and less than 3 nm account for 50% of the total pore volume, and micropores greater than or equal to 0.5 nm and less than 1 nm account for 50% of the total pore volume. Specific surface area is 1500 m² / g) 2 / g) is filled in region 3 of the device to form a fully functional device, wherein the filling ratio of macroporous adsorbent is 60%.

[0066] Cooling medium (ice-salt water) is introduced into heat exchange tubes 5 and 6 to maintain the device temperature at 0°C. Volatile organic compounds (primarily Ar gases, including high molecular weight C6-C8 organic compounds such as hydrocarbons, alcohols, and ketones) are introduced at concentrations of 1500, 100, and 100 mg / m³, respectively. 3 Low molecular weight organic compounds are C3-C5 organic compounds, including hydrocarbons and ethers, with concentrations of 1000 and 200 mg / m³, respectively. 3 The gas (at a pressure of 1.5 MPa) enters the device through gas inlet 7, first passing through region 2 filled with large mesoporous adsorbent to retain larger molecular weight organic compounds while not adsorbing smaller molecular weight organic compounds. Then it passes through region 3 filled with small mesoporous adsorbent to retain smaller molecular weight organic compounds. Finally, the gas exits the device through gas outlet 8, meeting emission standards.

[0067] During desorption, close gas inlet 7 and gas outlet 8, and open gas outlet 9. Purge the cooling medium (ice-salt water) from the heat exchange tubes; introduce a high-temperature medium (steam) into the heat exchange tubes to maintain the device temperature at 180°C. This causes the organic matter adsorbed on the small mesoporous adsorbent to evaporate, forming a purge gas that, combined with the high temperature, strips the organic matter adsorbed on the large mesoporous adsorbent. The desorbed gas exits the device from gas outlet 9. After desorption is complete, resume adsorption operation to continue treating volatile organic compounds. Use two identical devices, one in adsorption operation and the other in desorption operation, to ensure a continuous process.

[0068] Each adsorption cycle lasts 20–20.5 hours, and the desorption cycle lasts 2–2.5 hours. The desorbed volatile organic compounds are concentrated and undergo further processing.

[0069] After 500 hours of operation, the organic matter content in the treated gas was detected at 12 mg / m³.

[0070] Example 4

[0071] The large mesoporous adsorbent (material is alumina, in which mesopores of 3-10 nm account for 90% of the total pore volume, and the specific surface area is 500 m²) is used. 2 / g) is filled into region 2 of the device and pressed down with a porous plate 4; then, a small mesoporous adsorbent (material is carbon, with mesopores greater than or equal to 1 nm and less than 3 nm accounting for 50% of the total pore volume, and micropores greater than or equal to 0.5 nm and less than 1 nm accounting for 50% of the total pore volume. Specific surface area is 2000 m²) 2 / g) is filled in region 3 of the device to form a fully functional device, wherein the filling ratio of macroporous adsorbent is 50%.

[0072] Cooling medium (ice-salt water) is introduced into heat exchange tubes 5 and 6 to maintain the device temperature at 5°C. Volatile organic compounds (primarily He gas, with high molecular weight organic compounds being C8-C) are introduced. 12 Organic compounds, including alcohols, esters, sulfides, etc., at concentrations of 1000, 200, and 200 mg / m³, respectively. 3 Low molecular weight organic compounds are C3-C5 organic compounds, including hydrocarbons, alcohols, and esters, with concentrations of 100, 500, and 300 mg / m³, respectively. 3 The gas (at a pressure of 0.6 MPa) enters the device through gas inlet 7, first passing through region 2 filled with large mesoporous adsorbent to retain larger molecular weight organic compounds while not adsorbing smaller molecular weight organic compounds. Then it passes through region 3 filled with small mesoporous adsorbent to retain smaller molecular weight organic compounds. Finally, the gas exits the device through gas outlet 8, meeting emission standards.

[0073] During desorption, close gas inlet 7 and gas outlet 8, and open gas outlet 9. Purge the cooling medium (ice-salt water) from the heat exchange tubes; introduce a high-temperature medium (flue gas) into the heat exchange tubes to maintain the device temperature at 170°C. This causes the organic matter adsorbed on the small mesoporous adsorbent to evaporate, forming a purge gas that, combined with the high temperature, strips the organic matter adsorbed on the large mesoporous adsorbent. The desorbed gas exits the device from gas outlet 9. After desorption is complete, resume adsorption operation to continue treating volatile organic compounds. Use two identical devices, one in adsorption operation and the other in desorption operation, to ensure a continuous process.

[0074] Each adsorption cycle lasts 20–20.5 hours, and the desorption cycle lasts 2–2.5 hours. The desorbed volatile organic compounds are concentrated and undergo further treatment. After 500 hours of operation, the organic compound content in the treated gas was measured at 11 mg / m³.

[0075] Example 5

[0076] The macroporous adsorbent (made of silica, in which mesopores of 3-10 nm account for 90% of the total pore volume, and the specific surface area is 1000 m²) is used. 2 / g) is filled into region 2 of the device and pressed down with porous plate 4; then, a small mesoporous adsorbent (material is carbon, in which mesopores greater than or equal to 1 nm and less than 3 nm account for 50% of the total pore volume, and micropores greater than or equal to 0.5 nm and less than 1 nm account for 50% of the total pore volume. Specific surface area is 2000 m² 2 / g) is filled in region 3 of the device to form a fully functional device, wherein the filling ratio of macroporous adsorbent is 50%.

[0077] Cooling medium (cooling water) is introduced into heat exchange tubes 5 and 6 to maintain the device temperature at 10°C. Volatile organic compounds (primarily nitrogen gas, containing high molecular weight C6-C9 organic compounds, including hydrocarbons, ketones, sulfides, etc.) are introduced at concentrations of 1500, 100, and 100 mg / m³, respectively. 3 Low molecular weight organic compounds are C3-C5 organic compounds, including hydrocarbons and esters, with concentrations of 500 and 500 mg / m³, respectively. 3 The gas (at a pressure of 0.8 MPa) enters the device through gas inlet 7, first passing through region 2 filled with large mesoporous adsorbent to retain larger molecular weight organic compounds while not adsorbing smaller molecular weight organic compounds. Then it passes through region 3 filled with small mesoporous adsorbent to retain smaller molecular weight organic compounds. Finally, the gas exits the device through gas outlet 8, meeting emission standards.

[0078] During desorption, close gas inlet 7 and gas outlet 8, and open gas outlet 9. Drain the cooling medium (cooling water) from the heat exchange tubes; introduce a high-temperature medium (steam) into the heat exchange tubes to maintain the device temperature at 185°C. This causes the organic matter adsorbed on the small mesoporous adsorbent to evaporate, forming a purge gas. This purge gas, combined with the high temperature, removes the organic matter adsorbed on the large mesoporous adsorbent. The desorbed gas exits the device from gas outlet 9. After desorption is complete, resume adsorption operation to continue treating volatile organic compounds. Use two identical devices, one in adsorption operation and the other in desorption operation, to ensure a continuous process.

[0079] Each adsorption cycle lasts 20–20.5 hours, and the desorption cycle lasts 2–2.5 hours. The desorbed volatile organic compounds are concentrated and undergo further treatment. After 500 hours of operation, the organic compound content in the treated gas is detected to be 10 mg / m³.

[0080] Comparative Example 1

[0081] Compared with Example 5, the only difference is that both Region 2 and Region 3 are filled with macroporous adsorbents (same as Example 5).

[0082] Adsorption and desorption were performed according to the method in Example 5. After 100 hours of operation, the organic matter content in the treated gas was 142 mg / m³; after 300 hours of operation, the organic matter content was 157 mg / m³; and after 500 hours of operation, the organic matter content was 168 mg / m³.

[0083] Comparative Example 2

[0084] Compared with Example 5, the only difference is that both Region 2 and Region 3 are filled with small mesoporous adsorbents (same as Example 5).

[0085] Adsorption and desorption were performed according to the method described in Example 5. Each adsorption cycle lasted 20-20.5 hours, and each desorption cycle lasted 2-2.5 hours. After 100 hours of operation, the organic matter content in the treated gas was 22 mg / m³; after 300 hours of operation, the organic matter content was 352 mg / m³; and after 500 hours of operation, the organic matter content was 638 mg / m³.

[0086] Comparative Example 3

[0087] Compared with Example 5, the only difference is that in both Region 2 and Region 3, a mixture of 40% macroporous adsorbent (same as Example 5) and 60% microporous adsorbent (same as Example 5) is filled.

[0088] Adsorption and desorption were performed according to the method in Example 5. After 100 hours of operation, the organic matter content in the treated gas was 52 mg / m³; after 300 hours of operation, the organic matter content was 352 mg / m³; and after 500 hours of operation, the organic matter content was 442 mg / m³.

[0089] Comparative Example 4

[0090] Compared with Example 5, the main difference is that the pore structure characteristics of the macroporous adsorbent are not controlled within the range described in this invention, specifically:

[0091] The macroporous adsorbent (material is silicon dioxide, in which mesopores >10nm account for 90% of the total pore volume, and the specific surface area is 800 m²) is used. 2 / g) is filled into region 2 of the device (filling amount is the same as in Example 5) and pressed with porous plate 4; then the small mesoporous adsorbent (same as in Example 5, filling amount is the same as in Example 5) is filled into region 3 of the device to form a fully functional device.

[0092] Cooling medium (cooling water) is introduced into heat exchange tubes 5 and 6 to maintain the device temperature at 10°C. Volatile organic compounds (primarily nitrogen gas, containing high molecular weight C6-C9 organic compounds, including hydrocarbons, ketones, sulfides, etc.) are introduced at concentrations of 1500, 100, and 100 mg / m³, respectively. 3Low molecular weight organic compounds are C3-C5 organic compounds, including hydrocarbons and esters, with concentrations of 500 and 500 mg / m³, respectively. 3 The gas (at a pressure of 0.8 MPa) enters the device through gas inlet 7, first passing through region 2 filled with large mesoporous adsorbent to retain larger molecular weight organic compounds while not adsorbing smaller molecular weight organic compounds. Then it passes through region 3 filled with small mesoporous adsorbent to retain smaller molecular weight organic compounds. Finally, the gas exits the device through gas outlet 8, meeting emission standards.

[0093] During desorption, close gas inlet 7 and gas outlet 8, and open gas outlet 9. Drain the cooling medium (cooling water) from the heat exchange tubes; introduce a high-temperature medium (steam) into the heat exchange tubes to maintain the device temperature at 185°C. This causes the organic matter adsorbed on the small mesoporous adsorbent to evaporate, forming a purge gas. This purge gas, combined with the high temperature, removes the organic matter adsorbed on the large mesoporous adsorbent. The desorbed gas exits the device from gas outlet 9. After desorption is complete, resume adsorption operation to continue treating volatile organic compounds. Use two identical devices, one in adsorption operation and the other in desorption operation, to ensure a continuous process.

[0094] The desorbed volatile organic compounds are concentrated and undergo further processing.

[0095] Adsorption and desorption were performed according to the method described in Example 5. After 100 hours of operation, the organic matter content in the treated gas was 32 mg / m³; after 300 hours of operation, the organic matter content was 132 mg / m³; and after 500 hours of operation, the organic matter content was 187 mg / m³.

[0096] Example 6

[0097] The macroporous adsorbent (material is silicon dioxide, in which mesopores of 3-10 nm account for 90% of the total pore volume, and the specific surface area is 800 m²) is used. 2 / g) is filled into region 2 of the device and pressed down with porous plate 4; then a small mesoporous adsorbent (material is carbon, in which 0.1-0.5 nm mesoporous pores account for 90% of the total pore volume, and the specific surface area is 4000 m²) is added. 2 / g) is filled in region 3 of the device to form a fully functional device.

[0098] Cooling medium (cooling water) is introduced into heat exchange tubes 5 and 6 to maintain the device temperature at 10°C. Volatile organic compounds (primarily nitrogen gas, containing high molecular weight C6-C9 organic compounds, including hydrocarbons, ketones, sulfides, etc.) are introduced at concentrations of 1500, 100, and 100 mg / m³, respectively. 3 Low molecular weight organic compounds are C3-C5 organic compounds, including hydrocarbons and esters, with concentrations of 500 and 500 mg / m³, respectively. 3The gas (at a pressure of 0.8 MPa) enters the device through gas inlet 7, first passing through region 2 filled with large mesoporous adsorbent to retain larger molecular weight organic compounds while not adsorbing smaller molecular weight organic compounds. Then it passes through region 3 filled with small mesoporous adsorbent to retain smaller molecular weight organic compounds. Finally, the gas exits the device through gas outlet 8, meeting emission standards.

[0099] During desorption, close gas inlet 7 and gas outlet 8, and open gas outlet 9. Drain the cooling medium (cooling water) from the heat exchange tubes; introduce a high-temperature medium (steam) into the heat exchange tubes to maintain the device temperature at 185°C. This causes the organic matter adsorbed on the small mesoporous adsorbent to evaporate, forming a purge gas. This purge gas, combined with the high temperature, removes the organic matter adsorbed on the large mesoporous adsorbent. The desorbed gas exits the device from gas outlet 9. After desorption is complete, resume adsorption operation to continue treating volatile organic compounds. Use two identical devices, one in adsorption operation and the other in desorption operation, to ensure a continuous process.

[0100] The desorbed volatile organic compounds are concentrated and undergo further processing.

[0101] Adsorption and desorption were performed according to the method in Example 5. After 100 hours of operation, the organic matter content in the treated gas was 12 mg / m³. After 300 hours of operation, the organic matter content in the treated gas was 18 mg / m³. After 500 hours of operation, the organic matter content in the treated gas was 42 mg / m³.

[0102] Example 7

[0103] The macroporous adsorbent (material is silicon dioxide, in which mesopores of 3-10 nm account for 90% of the total pore volume, and the specific surface area is 1000 m²) is used. 2 / g) is filled into region 2 of the device and pressed down with porous plate 4; then, a small mesoporous adsorbent (material is carbon, in which mesopores greater than or equal to 1 nm and less than 3 nm account for 50% of the total pore volume, and micropores greater than or equal to 0.5 nm and less than 1 nm account for 50% of the total pore volume. Specific surface area is 2000 m² 2 / g) is filled in region 3 of the device to form a fully functional device.

[0104] Cooling medium (cooling water) is introduced into heat exchange tubes 5 and 6 to maintain the device temperature at 10°C. Volatile organic compounds (primarily nitrogen gas, containing high molecular weight C6-C9 organic compounds, including hydrocarbons, ketones, sulfides, etc.) are introduced at concentrations of 1500, 100, and 100 mg / m³, respectively. 3 Low molecular weight organic compounds are C3-C5 organic compounds, including hydrocarbons and esters, with concentrations of 500 and 500 mg / m³, respectively. 3The gas (at a pressure of 0.8 MPa) enters the device through gas inlet 7, first passing through region 2 filled with large mesoporous adsorbent to retain larger molecular weight organic compounds while not adsorbing smaller molecular weight organic compounds. Then it passes through region 3 filled with small mesoporous adsorbent to retain smaller molecular weight organic compounds. Finally, the gas exits the device through gas outlet 8, meeting emission standards.

[0105] During desorption, close gas inlet 7 and gas outlet 8, and open gas outlet 9. Drain the cooling medium (cooling water) from the heat exchange tubes; introduce a high-temperature medium (steam) into the heat exchange tubes to maintain the device temperature at 185°C. This causes the organic matter adsorbed on the small mesoporous adsorbent to evaporate, forming a purge gas. This purge gas, combined with the high temperature, removes the organic matter adsorbed on the large mesoporous adsorbent. The desorbed gas exits the device from gas outlet 9. After desorption is complete, resume adsorption operation to continue treating volatile organic compounds. Use two identical devices, one in adsorption operation and the other in desorption operation, to ensure a continuous process.

[0106] The adsorption and desorption were performed according to the method in Example 5. The desorbed volatile organic compounds were concentrated and then further processed.

[0107] Example 7 underwent a long-term test. After 300 hours of continuous operation, the organic matter content in the treated gas was 12 mg / m³, with no change. After 1000 hours of continuous operation, the organic matter content was 14 mg / m³, also with no change. After 1500 hours of continuous operation, the exhaust gas met the requirements, and the organic matter content in the treated gas was 10 mg / m³. Under the same organic matter concentration, the amount of desorbed volatile organic compounds showed no significant change after 300 hours, 1000 hours, and 1500 hours of continuous operation, all remaining below 20 mg / m³.

[0108] Example 8

[0109] The macroporous adsorbent (made of silica, in which mesopores of 3-10 nm account for 90% of the total pore volume, and the specific surface area is 1000 m²) is used. 2 / g) is filled into region 2 of the device and pressed down with porous plate 4; then, a small mesoporous adsorbent (material is carbon, in which mesopores greater than or equal to 1 nm and less than 3 nm account for 50% of the total pore volume, and micropores greater than or equal to 0.5 nm and less than 1 nm account for 50% of the total pore volume. Specific surface area is 2000 m² 2 / g) is filled in region 3 of the device to form a fully functional device, wherein the filling ratio of macroporous adsorbent is 50%.

[0110] A cooling medium (cooling water) is introduced into heat exchange tubes 5 and 6 to maintain the temperature of the device at 10°C. Volatile organic compounds (the main carrier gas is nitrogen, wherein the large-molecular-weight organic compounds are C6-C9 organics, including hydrocarbons, ketones, thioethers, etc., with concentrations of 1500, 100, and 100 mg / m 3 respectively; the small-molecular-weight organic compounds are C3-C5 organics, including hydrocarbons and esters, with concentrations of 500 and 500 mg / m 3 respectively; and the gas pressure is 0.8 MPa) is introduced into the device through the gas inlet 7, first passes through the region 2 filled with large mesoporous adsorbent to trap large-molecular-weight organics while not adsorbing small-molecular-weight organics, then passes through the region 3 filled with small mesoporous adsorbent to trap small-molecular-weight organics. Afterwards, the gas exits the device through the gas outlet 8 and is discharged after reaching the standard.

[0111] During desorption operation, the gas inlet 7 and gas outlet 8 of the device are closed, and the gas outlet 9 is opened. The cooling medium (cooling water) in the heat exchange tubes is drained; a high-temperature medium (steam) is introduced into the heat exchange tubes to maintain the temperature of the device at 185°C. The organic compounds adsorbed on the small mesoporous adsorbent are evaporated out to form a purge gas, which配合 the high temperature to strip the organic compounds adsorbed on the large mesoporous adsorbent. The desorbed gas exits the device from the gas outlet 9. After desorption is completed, the adsorption operation is resumed to continue treating volatile organic compounds. Two identical devices are used, so that when one is in adsorption operation, the other is in desorption operation, making the process continuous.

[0112] The desorbed volatile organic compounds are concentrates, which are subjected to further treatment.

[0113] After 500 hours of operation, the detected organic content in the treated gas is 10 mg / m³. Through collection and analysis of the desorption recovery liquid, the organic recovery rate reaches 99.6%. Through metering of the steam consumption in the desorption process, the steam consumption within the 500h cycle is 5.8 t. Through statistics of the desorption time, the average duration is 1.8 h.

[0114] Example 8 was subjected to a long-period test: after continuous operation for 1000h, the detected organic content in the treated gas was 13 mg / m³, with no change in content; after continuous operation for 1500h, the exhaust gas remained qualified, and the detected organic content in the treated gas was 14 mg / m³. Under the same organic concentration condition, the amount of desorbed volatile organic compounds had no significant change after 500h, 1000h, and 1500h of continuous operation, all being below 20 mg / m³.

[0115] Comparative Example 5

[0116] Compared with Example 8, the main difference is that the adsorption and desorption regions are separately provided (according to Figure 2 ), the desorption gas cannot be utilized according to the process described in the present invention, specifically:

[0117] The large mesoporous adsorbent (same as in Example 8) is filled in a separate region 3; then the small mesoporous adsorbent (same as in Example 8) is filled in region 4 of the device, and the volumes of region 3 and region 4 are equal.

[0118] Cooling medium (cooling water) is introduced into heat exchanger tube 1 to maintain the device temperature at 10℃. Volatile organic compounds (primarily nitrogen gas, with high molecular weight C6-C9 organic compounds including hydrocarbons, ketones, sulfides, etc.) are introduced at concentrations of 1500, 100, and 100 mg / m³. 3 Low molecular weight organic compounds are C3-C5 organic compounds, including hydrocarbons and esters, with concentrations of 500 and 500 mg / m³, respectively. 3 The gas (at a pressure of 0.8 MPa) enters the device through gas inlet 4, first passing through region 2 filled with large mesoporous adsorbent to retain larger molecular weight organic compounds while not adsorbing smaller molecular weight organic compounds. After passing through pipe 5, it then passes through region 3 filled with small mesoporous adsorbent to retain smaller molecular weight organic compounds. Finally, the gas exits the device through gas outlet 6, meeting emission standards.

[0119] During desorption, gas inlet 4 and gas outlet 6 are closed, while gas outlets 7 and 8 are opened. The cooling medium (cooling water) in the heat exchange tubes is purged; a high-temperature medium (steam) is introduced into the heat exchange tubes to maintain the device temperature at 185°C. Organic matter adsorbed on the large mesoporous adsorbent in region 2 is evaporated at outlet 7, and organic matter adsorbed on the small mesoporous adsorbent in region 3 is evaporated at outlet 8. After desorption is complete, adsorption operation is resumed to continue treating volatile organic compounds. Two identical devices are used, one in adsorption operation and the other in desorption operation, to ensure a continuous process.

[0120] The desorbed volatile organic compounds are concentrated and undergo further processing.

[0121] After 500 hours of operation, the organic matter content in the treated gas was detected at 10 mg / m³. Analysis of the recovered liquid showed an organic matter recovery rate of 99.6%. Steam consumption during the desorption process was measured to be 7.2 tons over 500 hours, an increase of 24.1% compared to Example 8. The average desorption time was 2.3 hours, an increase of 27.7% compared to Example 8.

[0122] Comparative Example 5 underwent a long-cycle test, running for 800 hours, with the organic matter content in the treated gas detected at 15 mg / m³; after 1000 hours, the organic matter content was 20 mg / m³; and after 1500 hours, it was 31 mg / m³. While meeting the requirement that the organic matter content in the treated gas should not exceed 20 mg / m³, Comparative Example 5 shortened the analysis cycle by 50% compared to Example 8.

Claims

1. A method for treating volatile organic compound (VOC) gases using a staged treatment device, wherein the staged treatment device for VOC gases is characterized in that, Including adsorption containers; The adsorption chamber of the adsorption container includes two adsorption zones: adsorption zone A, which is filled with macroporous adsorbent A, and adsorption zone B, which is filled with microporous adsorbent B. In the macroporous adsorbent A, mesopores of 3-10 nm account for more than 80-95% of the total pore volume; in the microporous adsorbent B, the pore size is less than 3 nm. The adsorption zone A has pores A on its wall; the adsorption zone B has pores B on its wall. The adsorption zone A and adsorption zone B are separated by a porous plate with pores; Includes a fractional adsorption step: The volatile organic compound gas to be treated enters the adsorption chamber of the device through pore A, and flows sequentially through adsorption zone A and adsorption zone B. In adsorption zone A, high molecular weight gases are selectively adsorbed, and in adsorption zone B, low molecular weight gases are selectively adsorbed; and the purified gas is discharged through pore B. It also includes a countercurrent desorption step: closing pore B, heating and desorbing adsorption zones A and B, using the desorbed gas from adsorption zone B to purge adsorption zone A to assist thermal desorption, and collecting the thermal desorbed gas from pore A.

2. The method as described in claim 1, characterized in that, In the aforementioned mesoporous adsorbent A, mesopores of 3-10 nm account for 90-95% of the total pore volume.

3. The method as described in claim 1, characterized in that, The specific surface area of ​​macroporous adsorbent A is 200-1500 m². 2 / g.

4. The method as described in claim 1, characterized in that, In the small mesoporous adsorbent B, mesopores with a diameter greater than or equal to 1 nm and a diameter less than 3 nm account for 40-60% of the total pore volume, and the remainder consists of micropores with a diameter greater than or equal to 0.5 nm and a diameter less than 1 nm.

5. The method as described in claim 1, characterized in that, The materials of the macroporous adsorbents A and B are at least one of carbon, silicon dioxide, and aluminum oxide.

6. The method as described in claim 1, characterized in that, In the filling chamber, the volume ratio of macroporous adsorbent A is 20-80%.

7. The method as described in claim 1, characterized in that, It also includes a three-way airflow valve, wherein the first port of the three-way valve is connected to the air port A, the second port is connected to the gas to be treated, and the third port is connected to the desorbed gas storage tank; or, the wall of the adsorption zone A is also provided with an air port C for discharging the desorbed gas.

8. The method as described in claim 7, characterized in that, It also includes a heat exchange device for controlling the temperature of adsorption zone A and adsorption zone B.

9. The method as described in claim 1, characterized in that, The temperature of the fractional adsorption stage is less than or equal to 30℃.

10. The method as described in claim 9, characterized in that, The temperature for the fractional adsorption stage is -5 to 20℃.

11. The method as described in claim 1, characterized in that, The high molecular weight gas is C6-C. 12 The organic compounds; the low molecular weight gas is a C3-C5 organic compound.

12. The method as described in claim 11, characterized in that, The high molecular weight gas is at least one of hydrocarbons, alcohols, esters, amines, thiols, ketones, and thioethers with the specified number of carbon atoms; The low molecular weight gas is at least one of hydrocarbons, alcohols, esters, amines, and ethers with the specified number of carbon atoms.

13. The method as described in claim 12, characterized in that, The concentration of high molecular weight gases in the volatile organic compounds to be treated is 500-2000 mg / m³. 3 ; The concentration of low molecular weight gases is 500-2000 mg / m³. 3 ; The pressure of the volatile organic compound gas to be treated is 0.1-2 MPa.

14. The method as described in claim 1, characterized in that, During the countercurrent desorption process, the adsorption zones A and B are heated to a temperature of 140-200℃.

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