Apparatus and method for removing vocs by low temperature condensation

Abstract

The application discloses a device and method for removing VOC by low-temperature condensation, which comprises a filter bin filled with rigid filter medium, and industrial waste gas is directed to flow through the rigid filter medium; and a reduction bin intermittently communicated with the filter bin, and the rigid filter medium can flow from the filter bin into the reduction bin; wherein the reduction bin is filled with low-temperature ionic liquid capable of covering all the rigid filter medium, and the temperature of the low-temperature ionic liquid is lower than the common boiling point of each component of VOC in the industrial waste gas; and the reduction bin is also provided with a desorption discharge outlet. The application can recycle available VOC with low energy consumption, and solves the problem that the existing condensation recovery VOC needs to condense air and VOC, resulting in a large amount of energy consumption waste.

Description

Technical Field

[0001] This invention belongs to the field of waste gas treatment technology, specifically relating to a device and method for removing VOCs by low-temperature condensation. Background Technology

[0002] Volatile organic compounds (VOCs) are a type of gaseous pollutant. Common components include hydrocarbons, benzene compounds, alcohols, ketones, phenols, aldehydes, esters, amines, and cyanides.

[0003] Based on the treatment methods, there are two main categories of methods for treating organic waste gas: recovery methods and elimination methods. Recovery methods mainly include carbon adsorption, pressure swing adsorption, condensation, and membrane separation technology. Recovery methods separate VOCs using physical methods such as temperature, pressure, selective adsorbents, and selectively permeable membranes. Elimination methods include thermal oxidation, catalytic combustion, biological oxidation, and integrated technologies. Elimination methods mainly use chemical or biochemical reactions, employing heat, catalysts, and microorganisms to convert organic matter into CO2 and water. Traditionally, VOC waste gas treatment often employs adsorption or absorption elimination, combustion elimination, etc. However, these methods have drawbacks: adsorbents have short lifespans, require frequent replacement, and the replaced adsorbents become hazardous waste, requiring more resources for treatment; combustion elimination increases carbon emissions, which is inconsistent with environmental protection policies aimed at carbon reduction.

[0004] While low-temperature condensation recovery of VOCs can achieve VOC condensation and recovery, it requires the complete condensation of both air and VOCs, resulting in significant energy waste. Furthermore, due to the poor heat transfer properties of gases, the gas needs to remain in the condensation chamber for a prolonged period of heat exchange, which cannot meet the requirements for treating large-volume VOC emissions. Patent CN104606915 uses low-temperature nitrogen to condense VOC emissions, but this method suffers from high nitrogen costs. Additionally, the work done by the low-temperature nitrogen during condensation requires the combined action of the air and VOC gases, resulting in high energy consumption despite employing a cold energy recovery method. Moreover, most of the exhaust gas contains moisture, which freezes below 0°C, reducing system reliability. The exhaust gas leaving the condenser still contains a considerable concentration of VOCs, failing to meet environmental emission standards. Summary of the Invention

[0005] The purpose of this section is to outline some aspects of embodiments of the present invention and to briefly describe some preferred embodiments. Simplifications or omissions may be made in this section, as well as in the abstract and title of this application, to avoid obscuring the purpose of these documents; however, such simplifications or omissions should not be construed as limiting the scope of the invention.

[0006] In view of the problems existing in the above and / or prior art, the present invention is proposed.

[0007] One objective of this invention is to provide a device for removing VOCs by low-temperature condensation, which can recover all usable VOCs with low energy consumption, solving the problem that existing condensation recovery of VOCs requires condensing all air and VOCs, resulting in a large amount of energy waste.

[0008] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a device for removing VOCs by low-temperature condensation, comprising,

[0009] A filter chamber, wherein the filter chamber is filled with a rigid filter medium, and industrial waste gas flows directionally through the rigid filter medium; and,

[0010] The reduction chamber is intermittently connected to the filter chamber, and the rigid filter medium can flow from the filter chamber into the reduction chamber;

[0011] The reduction chamber is filled with a low-temperature ionic liquid that can cover all the rigid filter media. The temperature of the low-temperature ionic liquid is lower than the common boiling point of the VOC components in the industrial waste gas. The reduction chamber is also equipped with a desorption outlet.

[0012] The term "rigid filter media" as used in this article refers to materials with a certain degree of rigidity that can provide adsorption performance, enabling them to adsorb VOCs from industrial waste gases. Common "rigid filter media" can be spherical or near-spherical porous materials such as alumina, aluminum silicate, silicon dioxide, and carbides.

[0013] The term "directional flow" as used in this article refers to industrial waste gas moving in a fixed direction and maintaining that flow direction at all times. For example, it enters from one side of the filter chamber, passes through the rigid filter media, and exits from the other side of the filter chamber.

[0014] The term "intermittent connection" as used in this article refers to the fact that the reduction chamber and the filtration chamber are not always connected (isolated), but rather connected as needed. Throughout the entire process, the connection between the reduction chamber and the filtration chamber is intermittent, switching between connected and isolated states. For example, the reduction chamber and the filtration chamber are connected by a pipeline, and a valve is installed on this pipeline to control the connection or isolation between the two.

[0015] The term "low-temperature ionic liquid" as used in this article refers to a solution in which pure water is used as a solvent and ionic salts or compounds that can lower the melting point of the liquid are used as solutes. Depending on the melting point of the ionic liquid required in the work, ionic liquids can be prepared using compounds such as sodium chloride, calcium chloride, ethylene glycol, diethylene glycol, or mixtures thereof, with sodium chloride, calcium chloride, and their mixtures being preferred.

[0016] As a preferred embodiment of the device for low-temperature condensation removal of VOCs from industrial waste gas according to the present invention, the rigid filter medium is a rigid porous microsphere with a diameter between 1 and 20 mm, a porous surface structure with a pore size of 1 to 20 μm, a porosity of 50 to 90%, and a BET specific surface area > 400 m². 2 / g, micropores and mesopores are mainly distributed on the surface of the spheres, facilitating rapid adsorption and desorption. Since the spheres need to be transported and flowed, they must possess corresponding impact resistance, >15KJ / ㎡. Because the spheres need to undergo VOC liquid-phase recovery in a low-temperature reduction chamber, they must possess corresponding strengths, including impact resistance >20KJ / ㎡, flexural strength >60MPa, and tensile strength >50MPa; simultaneously, without considering the water absorption of the pore size, the material's water absorption rate is <1%.

[0017] As a preferred embodiment of the device for low-temperature condensation removal of VOCs from industrial waste gas according to the present invention, the rigid porous microspheres are spherical, microspheres, or quasi-spherical materials produced by calcination of metal salts or synthesized from polymer materials, possessing porous physical properties; different pore-opening agents can be selected to generate the required pore size. The rigid filter medium needs to have high strength and low water absorption. The material can be hydrophobically treated. Optional materials include polyphenylene ether, polyamide, polystyrene, polyethylene, polyimide, polypropylene, polycarbonate, polyester, or alumina, zinc oxide, manganese oxide, silicon dioxide, aluminum silicate, diatomaceous earth, graphite, activated coke, activated carbon, carbon fiber, carbon nanotubes, titanium dioxide, silicon carbide, silicon nitride, rare earth materials; or mixtures thereof. Alumina, aluminum silicate, silicon dioxide, manganese oxide, and polyimide are preferred.

[0018] As a preferred embodiment of the device for removing VOCs by low-temperature condensation according to the present invention, the desorption outlet includes a medium outlet and a liquid outlet;

[0019] The media outlet is connected to the top of the cleaning chamber and the filter chamber via the cleaning chamber.

[0020] As a preferred embodiment of the device for removing VOCs by low-temperature condensation according to the present invention, the reduction chamber is further provided with an ultrasonic generator.

[0021] In a preferred embodiment of the device for removing VOCs by low-temperature condensation according to the present invention, the liquid outlet is connected to a separator, and the separator has a VOC solvent recovery port and an ionic liquid recovery port.

[0022] The VOC solvent recovery port is connected to a solvent recovery chamber, and the ionic liquid recovery port is connected to the reduction chamber.

[0023] As a preferred embodiment of the device for removing VOCs by low-temperature condensation according to the present invention, the separator further has a gas recovery port, which is connected to a gas recovery chamber for recovering low-boiling-point VOC components.

[0024] As a preferred embodiment of the device for removing VOCs by low-temperature condensation according to the present invention, wherein: one side of the filter chamber is connected to the air inlet chamber, the other side of the filter chamber is connected to the exhaust chamber, and the filter chamber is isolated from the air inlet chamber and the exhaust chamber respectively by filter screens;

[0025] The direction from the air inlet to the exhaust outlet constitutes the directional flow direction of the industrial waste gas.

[0026] As a preferred embodiment of the device for removing VOCs by low-temperature condensation according to the present invention, wherein: the bottom of the air inlet chamber is provided with an exhaust gas inlet, the top of which is closed, and the side of the air inlet chamber is connected to the filter chamber;

[0027] The exhaust chamber has a clean air outlet at the top and is closed at the bottom. The side of the exhaust chamber is connected to the filter chamber.

[0028] In a preferred embodiment of the device for removing VOCs by low-temperature condensation according to the present invention, the bottom width of the air inlet chamber is smaller than its top width.

[0029] The bottom width of the exhaust chamber is greater than its top width.

[0030] As a preferred embodiment of the device for removing VOCs by low-temperature condensation according to the present invention, it includes: multiple waste gas treatment units composed of the air inlet chamber, the filter chamber and the exhaust chamber;

[0031] The industrial waste gas selectively connects to the waste gas inlet of the air intake chamber;

[0032] The reduction chamber is selectively connected to the filtration chamber.

[0033] The term "selective connection" as used in this article refers to the selective connection of chambers as needed. Industrial waste gas can selectively enter one or more inlet chambers, and the reduction chamber can selectively connect with one or more filter chambers. Among them, no industrial waste gas enters the waste gas treatment unit where the filter chamber connected to the reduction chamber is located, and this stage is the desorption and reduction stage.

[0034] Another object of the present invention is to provide a method for removing VOCs by low-temperature condensation, comprising,

[0035] Industrial waste gas containing VOCs enters the filtration chamber, flows through the rigid filter medium, and is then discharged.

[0036] After adsorption, the rigid filter medium enters the reduction chamber and is immersed in a low-temperature ionic liquid. The gas with a boiling point higher than that of the low-temperature ionic liquid becomes a liquid VOC solvent. The liquid VOC solvent is suspended or floated in the low-temperature ionic liquid, and the mixture of liquid VOC solvent and low-temperature ionic liquid is discharged from the reduction chamber.

[0037] As a preferred embodiment of the low-temperature condensation method for removing VOCs according to the present invention, the mixed liquid discharged from the reduction chamber enters the separator, and the suspended or floating VOC solvent and the low-temperature ionic solution are separated by the physical properties of immiscibility and different specific gravities.

[0038] The separated VOC solvents enter the solvent recovery chamber for recycling.

[0039] The separated low-temperature ionic liquid is returned to the reduction chamber for recycling.

[0040] As a preferred embodiment of the method for removing VOCs by low-temperature condensation according to the present invention, the method further includes: the low-boiling-point compounds contained in the waste gas volatilize in the separator and enter the gas recovery chamber for recycling.

[0041] As a preferred embodiment of the method for removing VOCs by low-temperature condensation of the present invention, the mixture is completely discharged from the reduction chamber, and the rigid filter medium desorbed and reduced in the reduction chamber is discharged.

[0042] Rigid filter media enter the cleaning chamber for cleaning and drying, and are then recycled.

[0043] Compared with the prior art, the present invention has the following beneficial effects:

[0044] This invention can recover all usable VOCs with low energy consumption, solving the problem of existing condensation recovery methods that require condensing all air and VOCs, resulting in significant energy waste. This invention only condenses the VOCs that need to be recovered and reused. Since the mass and volume ratio of VOCs in industrial waste gas is basically at the PPM level, energy consumption can be greatly reduced. Attached Figure Description

[0045] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein:

[0046] Figure 1 This is a schematic diagram of the structure of Embodiment 1 of the present invention;

[0047] Figure 2 This is a schematic diagram of the structure of Embodiment 2 of the present invention;

[0048] Figure 3 This is a schematic diagram of the structure of Embodiment 3 of the present invention;

[0049] Figure 4 This is a schematic diagram of the structure of Embodiment 4 of the present invention;

[0050] Figure 5 This is a schematic diagram of the connection between the filter chamber, the air intake chamber, and the exhaust chamber in Embodiment 4 of the present invention;

[0051] Figure 6 This is a schematic diagram of the structure of Embodiment 5 of the present invention;

[0052] Figure 7 This is a flowchart of Embodiment 5 of the present invention. Detailed Implementation

[0053] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the examples in the specification.

[0054] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0055] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0056] Example 1

[0057] like Figure 1 As shown, this is the first embodiment of the present invention. This embodiment provides a device for removing VOCs by low-temperature condensation, which mainly includes a filter chamber 100 and a reduction chamber 200. The filter chamber 100 adsorbs VOCs in industrial waste gas through an adsorption medium, while the reduction chamber 200 is used to desorb and reduce the adsorption medium that has been saturated with adsorption.

[0058] Specifically, the filter chamber 100 adopts a chamber structure commonly used in the field of waste gas treatment. Except for the parts that need to be connected to the outside, the rest is a closed structure. The filter chamber 100 is filled with a rigid filter medium S1. In this embodiment, the rigid filter medium S1 is a rigid porous microsphere with a porous structure. The rigid porous microsphere is made by calcining metal salts or synthesizing polymer materials, and has porous physical properties; at the same time, different pore-opening agents can be selected to generate the required pore size. During manufacturing, the material can be hydrophobically treated. The rigid porous microsphere needs to have high strength, low temperature resistance, good wear resistance, and no powdering. Optional materials include polyphenylene ether, polyamide, polystyrene, polyethylene, polyimide, polypropylene, polycarbonate, polyester, alumina, zinc oxide, manganese oxide, silicon dioxide, aluminum silicate, diatomaceous earth, graphite, activated coke, activated carbon, carbon fiber, carbon nanotubes, titanium dioxide, silicon carbide, silicon nitride, and rare earth materials. Alumina, aluminum silicate, silicon dioxide, manganese oxide, and polyimide are preferred. The diameter of the rigid porous microsphere is 1–20 mm; preferably 4–6 mm.

[0059] It should be noted that the filter chamber 100 also has a gas inlet 101 and a gas outlet 102. Industrial waste gas enters the filter chamber 100 through the gas inlet 101, flows through the rigid filter medium S1, and is discharged through the gas outlet 102. During this process, nitrogen oxides, sulfur dioxide, and VOCs in the industrial waste gas are adsorbed by the mesopores and micropores on the surface of the rigid porous spheres. The filling amount of the rigid filter medium S1 in the filter chamber 100 is sufficient to ensure adequate contact with the incoming industrial waste gas. Generally, it is sufficient to simply allow the rigid porous spheres to naturally accumulate and fill the filter chamber 100.

[0060] The reduction chamber 200 is a shell structure with an internal cavity, and except for the parts that need to be connected to the outside, the rest is a closed structure. The desorption chamber 200 and the media outlet 103 of the filter chamber 100 are connected by a pipe, and the rigid filter media S1 can enter the reduction chamber 200 from the media outlet 103 of the filter chamber 100 through the pipe.

[0061] The reduction chamber 200 consists of a cryogenic storage tank, an insulation jacket, and refrigeration equipment. The preferred refrigeration equipment is a chilled brine chiller. The reduction chamber 200 is filled with a cryogenic ionic liquid whose temperature is lower than the common boiling point of the VOC components in the industrial waste gas, for example, a cryogenic ionic liquid with a temperature of -55℃. The cryogenic state of the ionic liquid is maintained by the refrigeration equipment.

[0062] After the rigid filter medium S1 is immersed in the low-temperature ionic liquid, the VOC gas with a boiling point of ≥-55℃ in the micropores and mesopores of the rigid porous microspheres is converted into liquid VOC solvent through heat transfer and detaches from the rigid porous microspheres, suspending or floating in the low-temperature ionic liquid, thereby achieving the purpose of desorption and reduction of the rigid porous microspheres, and then recovering the desorbed and reduced rigid porous microspheres.

[0063] To improve the desorption efficiency of rigid porous microspheres, an ultrasonic generator 203 is installed in the reduction chamber 200. The ultrasonic waves directly and indirectly act on the liquid and rigid porous microspheres through cavitation, acceleration and direct flow in the liquid, thereby dispersing, emulsifying and peeling off the VOC solvent to achieve rapid desorption.

[0064] Ionic liquids use pure water as a solvent and can be soluted with ionic salts or organic compounds that lower the melting point of the liquid. The temperature of the low-temperature ionic liquid can be adjusted according to the type of VOCs in the waste gas. Solutes for preparing ionic liquids can include compounds such as sodium chloride, calcium chloride, ethylene glycol, and diethylene glycol. Sodium chloride, calcium chloride, and mixtures thereof are preferred.

[0065] Example 2

[0066] like Figure 2 As shown, the difference between this embodiment and the first embodiment is that the restoration chamber 200 is also connected to the cleaning chamber 300 and the separator 400.

[0067] A mixture of VOC solvent and low-temperature ionic liquid is fed into separator 400, where suspended or floating VOC solvent and ionic liquid are separated by their physical properties of immiscibility and different specific gravities. The principle of separator 400 can be referenced from existing oil-water separators. The separated VOC solvent enters solvent recovery chamber 500 through VOC solvent recovery port 401 for recycling. The separated low-temperature ionic liquid is recycled back to reduction chamber 200 through ionic liquid recovery port 402 for reuse.

[0068] After the above mixture is completely discharged from the reduction chamber 200, the desorbed and reduced rigid porous microspheres in the reduction chamber 200 are discharged from the medium outlet 201 and enter the cleaning chamber 300. The cleaning chamber 300 cleans the low-temperature ionic liquid and residual VOC solvent adhering to the surface of the rigid porous microspheres, and then dries them for recycling. The working principle of the cleaning chamber 300 can be referred to as that of an ultrasonic cleaning device. The cleaning chamber 300 contains water and an ultrasonic generator, and the rigid porous microspheres are cleaned by the water.

[0069] Depending on the type of VOC in the exhaust gas, if it contains low-boiling-point compounds, the separator 400 can also be equipped with a gas recovery port 403. This gas recovery port 403 is connected to the gas recovery chamber 600. A gas sensor is installed at the gas recovery port 403. When the gas sensor detects that VOC gas with a boiling point lower than that of ionic liquid is volatilizing in the separator 400, this portion of low-boiling-point VOC gas is discharged and sent to the gas recovery chamber 600. The gas recovery chamber 600 can recover the VOCs through a -180°C cryogenic device or through adsorption by activated carbon fibers filled in the gas recovery chamber 600.

[0070] Example 3

[0071] like Figure 3 As shown, the difference between this embodiment and the first embodiment is that the rigid porous microspheres that have been desorbed and reduced are recycled online.

[0072] The filter chamber 100 also has a media inlet 104. The cleaning chamber 300 is connected to the media inlet 104 through a pipeline, and the desorbed and reduced rigid porous balls are sent back into the filter chamber 100.

[0073] It should be noted that by placing the media inlet 104 at the top of the filter chamber 100, the desorbed and reduced rigid porous balls enter the empty filter chamber 100 through the media inlet 104 and can naturally accumulate under the action of gravity without the need for additional energy.

[0074] Meanwhile, with the help of the gravity of the rigid porous balls, a conveying device is set below the filter chamber 100, such as a screw conveyor M. The inlet of the screw conveyor M is located directly below the medium outlet 103 of the filter chamber 100. The rigid porous balls that have adsorbed VOCs can flow out of the filter chamber 100 and into the screw conveyor M by gravity. The screw conveyor M then sends the rigid porous balls into the reduction chamber 200.

[0075] To achieve continuous operation of the rigid porous balls recycling system, a ball storage tank 900 is installed on the pipeline between the cleaning chamber 300 and the media inlet 104. The ball storage tank 900 pre-stores a certain amount of rigid porous balls, sufficient to fill the filter chamber 100 once. The cleaning chamber 300 uses a common conveying device, such as a positive pressure pump, to transport the desorbed and reduced rigid porous balls to the ball storage tank 900. The ball storage tank 900 then uses a common conveying device, such as a positive pressure pump, to transport the rigid porous balls to the filter chamber 100. When the ball storage tank 900 is positioned above the filter chamber 100, the weight of the rigid porous balls can be used for transport, reducing the need for additional conveying equipment.

[0076] It should be noted that electrically controlled valves can be installed on the pipes between the ball storage tank 900 and the filter chamber 100 (upper pipe) and between the filter chamber 100 and the screw conveyor M (lower pipe) to control the ball transport and ensure the system's airtightness. When the gas sensor equipped with the system detects that the concentration of the discharged gas is close to or exceeds the required index, the electrically controlled valve in the lower pipe opens, and the rigid porous balls that have adsorbed VOCs flow out of the filter chamber 100 by gravity. When the grating sensor of the electrically controlled valve detects that no balls are flowing out, the lower pipe valve closes, and the electrically controlled valve in the upper pipe opens, allowing the desorbed and reduced rigid porous balls to flow into the filter chamber 100 from the top ball storage tank 900 by gravity. When the grating sensor of the electrically controlled valve detects that the filter chamber 100 is full of balls, the electrically controlled valve in the upper pipe closes, and the system continues to operate; this is one cycle, and the process is repeated.

[0077] Example 4

[0078] like Figures 4-5 As shown, the difference between this embodiment and the above embodiment is that an air inlet chamber 700 is provided on one side of the filter chamber 100, and an exhaust chamber 800 is provided on the other side of the filter chamber 100. The filter chamber 100 is connected to both the air inlet chamber 700 and the exhaust chamber 800, and is isolated from both the air inlet chamber 700 and the exhaust chamber 800 by filter screens S2. Industrial waste gas enters the air inlet chamber 700 from the waste gas inlet, flows through the filter chamber 100, and is discharged from the clean gas outlet of the exhaust chamber 800. That is, the direction from the air inlet chamber 700 to the exhaust chamber 800 constitutes the directional flow direction of the industrial waste gas.

[0079] It should be noted that, to reduce system resistance and save energy, the exhaust gas inlet is located at the bottom 701 of the intake chamber 700, the top 702 of the intake chamber 700 is closed, and the side 703 of the intake chamber 700 is connected to the filter chamber 100. The clean gas outlet is located at the top 802 of the exhaust chamber 800, the bottom 801 of the exhaust chamber 800 is closed, and the side 803 of the exhaust chamber 800 is connected to the filter chamber 100.

[0080] In the air intake chamber 700, the width of the bottom 701 is smaller than the width of the top 702. When gas enters the air intake chamber 700, the flow velocity is reduced by the change in diameter from small to large, which reduces the influence of turbulence and allows the airflow to pass through the adsorption chamber 700 in a laminar flow form as evenly as possible.

[0081] A gas sensor can also be installed at the clean gas outlet of the exhaust chamber 800 to detect the gas concentration in real time; when the concentration exceeds the standard, the desorption and reduction process in Example 3 is executed. The bottom 801 of the exhaust chamber 800 is wider than its top 802; in the exhaust chamber 800, since the system is under negative pressure, a certain gas flow resistance is formed in the exhaust chamber 800 by the change in diameter from large to small, ensuring that the airflow velocity in the exhaust chamber is stable, which facilitates stable data collection by the gas sensor.

[0082] Example 5

[0083] like Figure 6 As shown, the difference between this embodiment and the previous embodiment is that the air intake chamber 700, the filter chamber 100, and the exhaust chamber 800 are combined into a single exhaust gas treatment unit. This embodiment consists of multiple exhaust gas treatment units connected in parallel. Each air intake chamber 700 is connected to a common air intake pipe P1 via an electrically controlled valve, and each exhaust chamber 800 is connected to a common exhaust pipe P2 via an electrically controlled valve. Additionally, each filter chamber 100 is connected to a screw conveyor M via an electrically controlled valve.

[0084] In addition, a dust particulate filter can be installed at the front end of the intake pipe P1 to filter and remove dust and particulate matter.

[0085] It should be noted that, depending on the amount of incoming gas, the operation of certain filter chambers is controlled by an electronically controlled valve to adapt to the unevenness of incoming gas volume in the production environment and minimize energy consumption.

[0086] Among these measures, to further improve the utilization rate of warehouse space, such as... Figure 5 As shown, the intake chamber 700 and the exhaust chamber 800 can be arranged alternately. A filter chamber 100 is set between adjacent intake chambers 700 and exhaust chambers 800. The exhaust gas entering the intake chamber 700 can pass through the filter chamber 100 from the left and right sides and enter the exhaust chamber 800. The exhaust chamber 800 collects the clean gas and finally discharges it.

[0087] Specifically, such as Figure 7 As shown, the workflow of this embodiment is as follows:

[0088] When VOC-containing exhaust gas passes through the front-end dust and particulate matter filter to remove dust and particulate matter, or when the industrial exhaust gas generated by the front-end production equipment does not contain dust and particulate matter, the gas is transported by the inlet pipe P1 to the bottom of each inlet chamber 700, passes through the metal porous mesh from the left and right sides and enters the filter chamber 100. VOCs are adsorbed by the mesopores and micropores on the surface of the rigid porous balls. The gas after passing through the filter chamber 100 does not contain or meets the emission standards and enters the exhaust chamber 800.

[0089] The top of the exhaust chamber 800 is connected to the exhaust pipe P2, and the treated clean air or air that meets the emission standards is discharged into the atmosphere through the negative pressure exhaust fan Q1.

[0090] When the gas sensor at the clean gas outlet at the top of the exhaust chamber 800 detects that the concentration of the discharged gas is close to or exceeds the required level, the electrically controlled valve in the pipeline between the filter chamber 100 and the screw conveyor M opens, allowing the rigid porous spheres that have adsorbed VOCs to flow out of the filter chamber 100 by gravity. When the grating sensor of the electrically controlled valve detects that no spheres are flowing out, the valve in the pipeline between the filter chamber 100 and the screw conveyor M closes, and the electrically controlled valve in the pipeline between the sphere storage tank 900 and the filter chamber 100 opens, allowing the desorbed and reduced rigid porous spheres to flow into the filter chamber 100 from the top sphere storage tank 900 by gravity. When the grating sensor of the electrically controlled valve detects that the spheres have filled the filter chamber 100, the electrically controlled valve in the pipeline between the sphere storage tank 900 and the filter chamber 100 closes, and the system continues to operate; this is one cycle, and the process is repeated. Because the system has multiple chambers connected in parallel, the sphere replacement time is controlled to approximately 3-5 minutes.

[0091] The rigid filter medium S1, which has adsorbed VOCs, enters the screw conveyor M and is sent by the screw conveyor M into the reduction chamber 200 for reduction treatment. The reduction chamber 200 stores a low-temperature ionic liquid at a temperature of -55℃. When the rigid filter medium S1 is immersed in the low-temperature ionic liquid, the VOC gas with a boiling point ≥ -55℃ in the micropores and mesopores of the rigid filter medium S1 is transformed into a liquid VOC solvent through heat transfer. The ultrasonic generator 203 installed in the reduction chamber 200 is activated, and the VOC solvent on the rigid filter medium S1 is detached under the action of ultrasonic waves, grows in the low-temperature ionic liquid, and floats or suspends in the low-temperature ionic liquid.

[0092] A mixture of VOC solvent and low-temperature ionic liquid is fed into separator 400, where suspended or floating VOC solvent and low-temperature ionic liquid are separated by their physical properties of immiscibility and different specific gravities. The separated VOC solvent enters solvent recovery chamber 500 through VOC solvent recovery port 401 for recycling; the separated low-temperature ionic liquid is recycled back to reduction chamber 200 through ionic liquid recovery port 402 for reuse.

[0093] After the above mixture is completely discharged from the reduction chamber 200, the rigid porous microspheres desorbed and reduced in the reduction chamber 200 are discharged from the medium outlet 201 and enter the cleaning chamber 300. The cleaning chamber 300 cleans and dries the low-temperature ionic liquid and residual VOC solvent adhering to the surface of the rigid porous microspheres. The cleaning chamber 300 then sends the desorbed and reduced rigid porous microspheres to the microsphere storage tank 900 by a positive pressure pump for recycling.

[0094] Depending on the type of VOC in the exhaust gas, if it contains low-boiling-point compounds, the separator 400 can also be equipped with a gas recovery port 403. This gas recovery port 403 is connected to the gas recovery chamber 600. A gas sensor is installed at the gas recovery port 403. When the gas sensor detects that VOC gas with a boiling point lower than that of ionic liquid is volatilizing in the separator 400, this portion of low-boiling-point VOC gas is discharged and sent to the gas recovery chamber 600. The gas recovery chamber 600 can recover the VOCs through a -180°C cryogenic device or through adsorption by activated carbon fibers filled in the gas recovery chamber 600.

[0095] A gas recovery chamber 600 is connected to the upper part of the separator 400. The gas recovery chamber 600 is a cryogenic recovery device for low-boiling-point VOC gases, used for the recovery of VOC gases with boiling points lower than ionic liquids. If there are no low-boiling-point components in the exhaust gas, this recovery device can be omitted.

[0096] Example 6

[0097] like Figure 6 As shown, a waste gas treatment test was conducted on the low-temperature condensation VOC removal device provided in Example 5. To facilitate statistical data collection, the chambers of the device were numbered. Excluding the adsorption chamber, only the inlet and outlet chambers were numbered. The first outlet chamber closest to the incoming gas direction was numbered 1#, the first adjacent inlet chamber was numbered 2#, and so on, until the last chambers were numbered 2n-1# and 2n#.

[0098] The adsorption chamber is filled with rigid porous microspheres made of alumina and aluminum silicate. The diameter of the rigid porous microspheres is between 4 and 6 mm, and their surface has a porous structure. Micropores and mesopores are mainly distributed on the surface of the microspheres, with a pore size of 1–20 μm, a porosity of 55%, and a BET specific surface area > 400 m². 2 / g; The physical properties of rigid porous microspheres are: impact strength > 20KJ / m 2 The material has a melting point >500℃, a heat distortion temperature >350℃, a flexural strength >60MPa, and a tensile strength >50MPa. The rigid porous microspheres have a good appearance and no surface damage.

[0099] Industrial waste gas containing VOCs (mainly benzene and esters, with trace amounts of water-soluble VOCs) and no low-boiling-point hydrocarbons was treated with particulate matter and dust removal to achieve a VOC concentration of 200 mg / m³. 3 The gas temperature is 50℃, and the flow rate is 10,000 standard cubic meters per hour. It is fed into the equipment's inlet chamber, which is equipped with a water sprayer to dissolve and recover water-soluble VOCs. The average velocity of the exhaust gas passing through the filtration and adsorption section is controlled at 0.05 m / s.

[0100] According to the formula S = V / 0.05, where V is the air volume per unit time and S is the required filtration and adsorption area, the required working chambers are calculated. System calculations indicate that two intake chambers and three exhaust chambers are needed. Therefore, in this embodiment 6, only... Figure 6 The air intake and exhaust of compartments 1 through 5 in the middle section are closed, while the air intake and exhaust of other compartments are closed.

[0101] After 24 hours of treatment, the VOC concentrations in chambers #1, #3, and #5 are shown in Table 1.

[0102] Table 1

[0103] Warehouse #1 1 Warehouse #3 0.5 Warehouse #5 0.3 average concentration 0.6 Processing efficiency 99.7％

[0104] After 24 hours of operation, the average concentration in chambers #2 and #4 increased by 30%. The process of replacing the rigid filter media was started, and the small balls that had adsorbed the gas entered the reduction chamber. The cleaned small balls were then added to the filter chamber to continue working.

[0105] The ionic liquid in the reduction chamber is cooled by a refrigeration device. The temperature is controlled at -50℃. When the rigid filter medium enters the reduction chamber, the liquid temperature rises. After being cooled down to -50℃ by the refrigeration device, the VOCs adsorbed on the rigid filter medium undergo a phase change, transforming from gas to liquid.

[0106] After the ultrasonic generator is started for 5 to 10 minutes, the VOC liquid droplets adsorbed on the rigid filter medium detach from the micropores of the rigid filter medium and suspend or float in the ionic liquid. The mixture is pumped to the separator, and the separator is started. The separator separates a total of 47,000g of VOC solvent for recycling, which is close to the calculation. The separated ionic liquid is pumped to the ionic liquid tank for recycling.

[0107] After the mixed liquid is pumped out of the reduction chamber, the rigid filter medium is released from the reduction chamber and transported to the cleaning chamber for cleaning and drying; the treated rigid filter medium is then transported to the sphere storage tank for later use.

[0108] Clean, rigid, porous microspheres from the microsphere storage tank are periodically sampled and analyzed by solvent extraction and GC-MS (mass spectrometry). The extract obtained by extraction with dichloromethane solvent at 60°C for 3 hours is then analyzed by GC-MS, and no VOC residues are found on the surface.

[0109] Example 7

[0110] Referring to Example 6, a waste gas treatment test was conducted on the low-temperature condensation VOC removal device provided in Example 5. The equipment and rigid porous spheres were identical. Industrial waste gas containing low-boiling-point hydrocarbons with VOCs (mainly benzene, styrene, and ethylene) was treated by removing particulate matter and dust, resulting in a VOC concentration of 100 mg / m³. 3The gas temperature is 40℃, and the flow rate is 20,000 standard cubic meters per hour. The average velocity of the exhaust gas passing through the filtration and adsorption section is controlled at 0.05 m / s.

[0111] According to the formula S = V / 0.05, where V is the air volume per unit time and S is the required filtration and adsorption area, the required working chambers are calculated. System calculations indicate that 4 inlet chambers and 5 exhaust chambers need to operate. Therefore, in Example 7, only... Figure 6 The air intake and exhaust of compartments 1 through 9 in the middle section are closed, while the air intake and exhaust of other compartments are closed.

[0112] After 3 hours of treatment, the VOC concentrations in chambers 1#, 3#, 5#, 7#, and 9# are shown in Table 2.

[0113] Table 2

[0114] Warehouse #1 0.4 Warehouse #3 0.2 Warehouse #5 0.3 Warehouse #7 01 Warehouse #9 0.07 average concentration 0.21 Processing efficiency 99.79％

[0115] After 3 hours of operation, the average concentration in chambers #2, #4, #6, and #8 increased by 30%. The process of replacing the rigid filter media was then initiated, with the gas-adsorbed pellets entering the reduction chamber. Clean pellets were then added to the filter chamber to continue operation.

[0116] The ionic liquid in the reduction chamber is cooled by a refrigeration device. The temperature is controlled at -40℃. When the rigid filter media enters the reduction chamber, the liquid temperature rises. After being cooled down to -40℃ by the refrigeration device, the VOCs adsorbed on the rigid filter media undergo a phase change, transforming from gas to liquid.

[0117] After the ultrasonic generator is started for 5-10 minutes, the VOC liquid droplets adsorbed on the rigid filter medium detach from the micropores of the rigid filter medium and suspend or float in the ionic liquid. Simultaneously, the gas sensor in the reduction chamber detects the presence of an atmosphere and pumps the mixture and atmosphere under negative pressure to the separator. The separator is then started, separating a total of 5760g of VOC solvent, mainly benzene and styrene, which are recycled. The difference between this and the calculated value of 5987g ​​is mainly low-boiling-point ethylene gas. The separator's gas recovery port is opened, and the low-boiling-point atmosphere is sent into the gas recovery chamber for recovery of the low-boiling-point ethylene under cryogenic conditions. The separated ionic liquid is then pumped back to the reduction chamber for recycling.

[0118] After the mixed liquid is pumped out of the reduction chamber, the rigid filter medium is released from the reduction chamber and transported to the cleaning chamber for cleaning and drying; the treated rigid filter medium is then transported to the sphere storage tank for later use.

[0119] Clean, rigid, porous microspheres from the microsphere storage tank are periodically sampled and analyzed by solvent extraction and GC-MS (mass spectrometry). The extract obtained by extraction with dichloromethane solvent at 60°C for 3 hours is then analyzed by GC-MS, and no VOC residues are found on the surface.

[0120] This invention can recover all usable VOCs with low energy consumption, solving the problem that existing VOC condensation recovery methods require condensing all air and VOCs, resulting in significant energy waste. This invention only condenses the VOC gases that need to be recovered and reused, and since the mass and volume ratio of VOC gases in industrial waste gas is basically at the PPM level, energy consumption can be greatly reduced.

[0121] This invention solves the problem of existing VOC condensation recovery equipment where water vapor in VOC gas freezes during operation, clogging the condenser and pipes, causing a decrease in system efficiency or shutdown. This invention utilizes a rigid filter medium to adsorb VOC gas at room temperature. When the rigid filter medium reaches the point where reduction or saturation is needed, it is transported to a low-temperature ionic liquid. Since the solvent of the low-temperature ionic liquid is H2O, the water vapor and solvent in the VOC gas are the same substance, completely eliminating the interference of water vapor condensation during VOC condensation recovery.

[0122] This invention can treat large volumes of various industrial VOCs and achieve emission standards by adjusting the number of rigid filter media. Different rigid filter media with different physical properties can also be selected according to the type of gas to achieve efficient adsorption. One system can complete the adsorption and removal of multiple pollutants.

[0123] Rigid filter media utilizes spherical or near-spherical spheres that are easily transported by gravity. Production can be achieved through calcination and activation with metal salts, or by using elemental materials or carbon materials with excellent VOC adsorption properties, exhibiting porous physical characteristics. Different pore-opening agents can be selected based on the type of VOC to create the required pore size. Several gases can also be mixed and added. Rigid porous spheres also possess high strength, high pressure resistance, low-temperature resistance, and do not shed powder; compared to activated carbon, they can be reused multiple times, saving operating costs. Rigid porous spheres are easy to replace after failure, without interrupting production.

[0124] The present invention can control the amount of waste gas entering the system through valves; and the number of removal modules used can save energy.

[0125] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A device for removing VOCs by low-temperature condensation, characterized in that: include, A filter chamber (100) filled with a rigid filter medium (S1), through which industrial waste gas flows directionally in the direction of flowing through the rigid filter medium (S1); and, The reduction chamber (200) is intermittently connected to the filter chamber (100), and the rigid filter medium (S1) can flow from the filter chamber (100) into the reduction chamber (200). The reduction chamber (200) is filled with a low-temperature ionic liquid that can cover the entire rigid filter medium (S1). The temperature of the low-temperature ionic liquid is lower than the common boiling point of the VOC components in the industrial waste gas. The ionic liquid uses pure water as a solvent and can use ionic salts or organic compounds that can lower the melting point of the liquid as solutes. The reduction chamber (200) is also provided with a desorption outlet, which includes a medium outlet (201) and a liquid outlet (202). The media outlet (201) is connected to the top of the filter chamber (100) via the cleaning chamber (300); It also includes multiple waste gas treatment units consisting of an air intake chamber (700), a filter chamber (100), and an exhaust chamber (800), wherein the industrial waste gas is selectively connected to the waste gas inlet of the air intake chamber (700), and the reduction chamber (200) is selectively connected to the filter chamber (100); The bottom (701) of the air intake chamber (700) is provided with an exhaust gas inlet, and its top (702) is closed. The side (703) of the air intake chamber (700) is connected to the filter chamber (100). The top (802) of the exhaust chamber (800) is provided with a clean air outlet, and its bottom (801) is closed. The side (803) of the exhaust chamber (800) is connected to the filter chamber (100).

2. The apparatus for removing VOCs by low-temperature condensation as described in claim 1, characterized in that: The rigid filter medium (S1) is a rigid porous microsphere, which has a porous structure.

3. The apparatus for removing VOCs by low-temperature condensation as described in claim 2, characterized in that: The reduction chamber (200) is also equipped with an ultrasonic generator (203).

4. The apparatus for removing VOCs by low-temperature condensation as described in claim 3, characterized in that: The liquid outlet (202) is connected to a separator (400), which has a VOC solvent recovery port (401) and an ionic liquid recovery port (402). The VOC solvent recovery port (401) is connected to a solvent recovery chamber (500), and the ionic liquid recovery port (402) is connected to the reduction chamber (200).

5. The apparatus for removing VOCs by low-temperature condensation as described in claim 4, characterized in that: The separator (400) also has a gas recovery port (403) connected to a gas recovery chamber (600).

6. The apparatus for removing VOCs by low-temperature condensation as described in any one of claims 1 to 5, characterized in that: One side of the filter chamber (100) is connected to the air intake chamber (700), and the other side of the filter chamber (100) is connected to the exhaust chamber (800). The filter chamber (100) is isolated from the air intake chamber (700) and the exhaust chamber (800) by filter screens (S2). The direction from the air inlet (700) to the exhaust (800) constitutes the directional flow direction of the industrial waste gas.

7. The apparatus for removing VOCs by low-temperature condensation as described in claim 6, characterized in that: The bottom (701) width of the air intake chamber (700) is smaller than the top (702) width; The bottom (801) width of the exhaust chamber (800) is greater than the top (802) width.

8. A method for removing VOCs by low-temperature condensation, using the apparatus for removing VOCs by low-temperature condensation as described in claim 7, characterized in that: include, Industrial waste gas containing VOCs enters the filter chamber (100), flows through the rigid filter medium (S1), and is then discharged. After adsorption, the rigid filter medium (S1) enters the reduction chamber (200) and is immersed in the low-temperature ionic liquid. The gas with a boiling point higher than the temperature of the low-temperature ionic liquid becomes a liquid VOC solvent. The liquid VOC solvent is suspended or floated in the low-temperature ionic liquid. The mixture of liquid VOC solvent and low-temperature ionic liquid is discharged from the reduction chamber (200).

9. The method for removing VOCs by low-temperature condensation as described in claim 8, characterized in that: The mixture discharged from the reduction chamber (200) enters the separator (400), where suspended or floating VOC solvents and low-temperature ionic solutions are separated by their physical properties of immiscibility and different specific gravities. The separated VOC solvent enters the solvent recovery chamber (500) for recycling; The separated low-temperature ionic liquid is returned to the reduction chamber (200) for recycling.

10. The method for removing VOCs by low-temperature condensation as described in claim 8 or 9, characterized in that: It also includes the volatilization of low-boiling-point compounds contained in the exhaust gas within the separator (400), which then enter the gas recovery chamber (600) for recycling.

11. The method for removing VOCs by low-temperature condensation as described in claim 10, characterized in that: After the mixture is completely discharged from the reduction chamber (200), the rigid filter medium desorbed and reduced in the reduction chamber (200) is discharged (S1). The rigid filter media (S1) enters the cleaning chamber (300) for cleaning and drying, and the rigid filter media (S1) is recycled.

Images