A method for recovering waste gas solvent

Abstract

The present invention provides a method for recovering waste gas solvents. The present invention relates to a method for recovering waste gas solvents, which aims to improve the recovery efficiency of organic solvents in waste gas and reduce environmental pollution. The method comprises the following steps: pre-treating waste gas to remove impurities and adjust temperature and humidity; adsorbing solvents in a primary adsorption tank through electric field enhanced adsorption technology; waste gas enters a secondary adsorption tank, and low-polarity solvents are separated by a separation membrane, and waste gas is discharged; desorption is performed through steam heating, pressure reduction and electric field reversal to recover solvents; condensing the mixed gas and improving the purity of the solvent through supergravity separation. The present invention realizes the efficient recovery of organic solvents in waste gas by comprehensively utilizing technologies such as electric field enhanced adsorption, hot steam desorption, condensation and supergravity separation, which not only improves the solvent recovery rate and reduces resource waste, but also reduces waste gas emissions, and has significant economic benefits and environmental protection value.

Description

Technical Field

[0001] The present invention relates to the field of environmental protection, and in particular to a method for recovering a waste gas solvent. Background Art

[0002] In industrial production processes, especially in the fields of chemical industry, coatings, printing, solvent recovery, etc., waste gas often contains a large amount of organic solvent components. These organic solvents not only cause serious pollution to the environment, but may also pose a threat to human health. Therefore, how to effectively recover and treat organic solvents in waste gas has become an important issue in environmental protection and resource recycling. Traditional methods for recovering waste gas solvents mainly include adsorption, condensation, washing, etc. The adsorption method usually uses adsorption materials such as activated carbon and molecular sieves to remove solvent components in waste gas through physical adsorption, but because the solvent recovery efficiency is low and it is easy to cause adsorbent saturation, it needs to be replaced or regenerated regularly. The condensation method condenses the solvent vapor into liquid by lowering the temperature and separates the solvent from the gas phase. It is suitable for situations where the solvent is highly volatile, but the condensation efficiency is closely related to conditions such as temperature and pressure changes, and the processing capacity is limited.

[0003] While existing technologies have proposed several improvements to address these issues, they still have limitations. For example, patent publication number CN220257590U discloses an organic waste gas solvent recovery device. However, this device still suffers from the following drawbacks: For some mixed solvents with complex compositions, existing recovery devices may not be able to achieve efficient separation and recovery. Different solvents have varying physical properties, such as boiling points and volatility, making it difficult to precisely control parameters like temperature and pressure during the recovery process. This can result in some solvents being unable to be fully recovered or having low purity after recovery. Summary of the Invention

[0004] (1) Technical problems solved

[0005] In view of the shortcomings of the prior art, the present invention aims to provide a method for recovering waste gas solvents, which solves the problems existing in the prior art. First, by utilizing electric field enhanced adsorption technology, the adsorption effect of solvent molecules and activated carbon is enhanced according to the polarity differences of different solvents, thereby ensuring efficient separation. Secondly, by precisely controlling the temperature, pressure and electric field direction during the desorption process, the recovery difficulties caused by differences in the physical properties of the solvents are effectively overcome, ensuring that more solvents can be desorbed. For low-polarity and small-molecule solvents, secondary adsorption and separation membrane technology are used to further optimize the separation process to ensure that the recovered solvent is purer. Finally, ultra-gravity separation technology further improves the purity of the solvent and ensures efficient recovery. Through these innovations, the present invention can solve the problems of separation difficulties and low purity in the complex solvent recovery process, and achieve efficient and accurate solvent recovery.

[0006] (2) Technical solution

[0007] To achieve the above object, the present invention provides the following technical solution: a method for recovering waste gas solvent, comprising the following steps:

[0008] S1 pretreatment: the waste gas containing solvent is passed into the pretreatment mechanism for filtration and temperature and humidity adjustment;

[0009] S2 primary adsorption: The pretreated exhaust gas is passed into the primary adsorption tank and adsorbed by activated carbon plates and electric field enhancement;

[0010] S3 secondary adsorption: the waste gas enters the secondary adsorption tank, and the low-grade and small-molecule solvents are separated by the separation membrane, and the waste gas is discharged through the chimney;

[0011] S4: Desorption: Steam is introduced into the first-stage adsorption tank for 15-30 minutes to perform decompression desorption while adjusting the direction and intensity of the electric field;

[0012] S5 condensation: condensing the desorbed mixed gas in a condensation mechanism;

[0013] S6 separation: the condensed mixed liquid is separated in a super gravity separation mechanism;

[0014] S7 Solvent Recovery: The separated high-purity solvent is transported to the solvent recovery tank for storage and subsequent use.

[0015] Preferably, in the S1 pretreatment step, the temperature of the exhaust gas is controlled at 25-30° C., and the humidity is controlled at 60%-80%.

[0016] Preferably, in the S2 primary adsorption step, the activated carbon plate is spiral-shaped, a central electrode is fixed to the central axis of the activated carbon plate, interlayer electrodes are embedded in the interior of the activated carbon plate, and both ends of the central electrode are connected to a reversible power supply.

[0017] Preferably, in the S2 primary adsorption step, the exhaust gas flow rate is controlled at 2000 m³ / h, the specific surface area of the activated carbon plate is controlled at 1500 m² / g, the porosity is greater than 80%, and the intensity of the electric field is controlled at 5-10 kV / m.

[0018] Preferably, in the S4 desorption step, the steam temperature is controlled to be 120-150°C.

[0019] Preferably, in the desorption step S4, the pressure of the adsorption tank during the reduced pressure desorption is controlled at 50-80 mbar.

[0020] Preferably, in the S4 desorption step, the intensity of the electric field is controlled to be 3-5 kV / m, and the direction of the electric field is opposite to that of the electric field in the S2 primary adsorption step.

[0021] Preferably, in step S5 condensation, the condensation temperature is controlled to be 5-10°C.

[0022] Preferably, in the separation step S6, the centrifugal force of the ultra-gravity separation device is 500-1000G.

[0023] (3) Beneficial effects

[0024] The present invention aims to provide a method for recovering organic solvents from waste gas. This method utilizes an advanced multi-step technology to significantly improve the recovery efficiency of organic solvents from waste gas and effectively reduce environmental pollution. The key innovation of this invention lies in the integration of electric field-enhanced adsorption, vapor desorption, condensation, and high-gravity separation technologies to form a highly efficient waste gas solvent recovery system.

[0025] First, through electric field-enhanced adsorption technology, the interaction between solvent molecules and adsorbent is enhanced by combining activated carbon plates with an electric field, significantly improving the adsorption efficiency of organic solvents in exhaust gas. The electric field not only enhances the directional adsorption of the solvent but also strengthens the binding force between the solvent and the adsorbent, making it easier for solvent molecules to be adsorbed on the activated carbon plates. Second, the desorption process combines high-temperature steam and vacuum decompression technology. By adjusting the direction and intensity of the electric field, the desorption efficiency of the solvent is further improved, ensuring that the adsorption capacity of the activated carbon saturated with adsorption can be quickly restored and the organic solvent can be efficiently recovered.

[0026] During the condensation stage, the present invention uses a low-temperature cooling medium to condense the desorbed mixed gas, effectively separating the solvent from other components in the exhaust gas and further improving the purity of the recovered solvent. Subsequently, high-gravity separation technology is used to finely separate the condensate through centrifugal force, removing impurities and water from the solvent. This ensures the recovered solvent is of high purity and suitable for reuse in the production process, reducing resource consumption.

[0027] Through the combination of this series of technologies, the present invention realizes the efficient recovery and separation of organic solvents in waste gas, which not only improves the solvent recovery rate and reduces the emission of harmful waste gas, but also effectively saves resources and reduces industrial production costs. It has significant economic benefits and environmental value and is suitable for multiple industrial fields, especially in waste gas treatment in the coatings, printing, chemical and other industries, and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiment below. The accompanying drawings are for illustration purposes only and are not to be considered as limiting the present invention. The same reference symbols are used throughout the drawings to represent the same components. In the drawings:

[0029] Figure 1 This is a schematic diagram of an overall waste gas solvent recovery method of the present invention;

[0030] Figure 2 This is a schematic diagram of a primary adsorption tank in a waste gas solvent recovery method of the present invention;

[0031] Figure 3 A schematic diagram of an activated carbon plate in a waste gas solvent recovery method of the present invention;

[0032] Figure 4 for Figure 3 An enlarged view of point A in the schematic diagram of an activated carbon plate in a waste gas solvent recovery method of the present invention;

[0033] Figure 5 A schematic diagram of overall adsorption and emission in a waste gas solvent recovery method of the present invention;

[0034] Figure 6 Schematic diagram of overall desorption and solvent recovery in a waste gas solvent recovery method of the present invention;

[0035] In the figure: 1-fixed frame, 2-pretreatment mechanism, 3-first-stage adsorption tank, 4-second-stage adsorption tank, 5-condensation mechanism, 6-supergravity separation mechanism, 7-solvent recovery tank, 8-steam furnace, 9-vacuum adsorption pump, 10-chimney, 31-tank body, 32-activated carbon plate, 33-internal reinforcement column, 34-center electrode, 35-interlayer electrode, 36-connection pipe, 37-reversible power supply. DETAILED DESCRIPTION

[0036] The following is a combination of the examples of the present invention Figures 1 to 6 A clear and complete description of the technical solutions in the embodiments of the present invention is provided. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0037] The device for the waste gas solvent recovery method includes: a fixed frame 1, a pretreatment mechanism 2 is provided on the right side of the fixed frame 1, a first-level adsorption tank 3 is fixed to the lower end of the fixed frame 1, a second-level adsorption tank 4 is provided on the left side of the first-level adsorption tank 3, a condensation mechanism 5 is provided at the front of the fixed frame 1, a supergravity separation mechanism 6 is connected to the rear end of the condensation mechanism 5, a solvent recovery tank 7 is connected to the left side of the supergravity separation mechanism 6, a steam furnace 8 is provided at the rear end of the fixed frame 1, and a vacuum adsorption pump 9 is provided at the upper end of the fixed frame 1. A chimney 10 is provided at the rear end of the fixed frame 1.

[0038] Pretreatment mechanism 2 performs preliminary treatment on waste gas containing organic solvents. Primary adsorption tank 3 adsorbs the pretreated waste gas to remove the majority of the organic solvent. Secondary adsorption tank 4 supplements the primary adsorption tank, providing additional adsorption for solvents that the primary adsorption tank struggles to absorb. Condensation mechanism 5 cools the desorbed organic solvent vapor into a liquid state. Supergravity separation mechanism 6 further separates the condensed liquid mixture. Solvent recovery tank 7 collects the high-purity organic solvent obtained after supergravity separation. Steam boiler 8 provides steam for desorption of activated carbon from the adsorption tank. After the activated carbon is saturated with adsorption, steam generated by the steam boiler enters the adsorption tank. The high temperature and energy of the steam promote desorption of organic solvent molecules from the activated carbon surface. The steam also cleans the activated carbon pores, restoring its adsorption properties and extending its service life, ensuring long-term, stable operation of the adsorption tank. A vacuum adsorption pump 9 reduces pressure within the adsorption tank during the desorption process, promoting desorption of the organic solvent from the activated carbon surface. It also prevents pressure abnormalities within the system and ensures safe operation. The chimney 10 serves to provide a safe exhaust gas discharge channel for the entire organic solvent recovery system.

[0039] The primary adsorption tank 3 comprises a tank body 31, within which an activated carbon plate 32 is fixed. An internal reinforcement column 33 is located in the middle of the activated carbon plate 32, and a central electrode 34 is located in the middle of the internal reinforcement column 33. Interlayer electrodes 35 are also located within the activated carbon plate 32. The activated carbon plate 32 has a large specific surface area and a rich pore structure, enabling it to adsorb organic solvent molecules in the exhaust gas through physical adsorption on its surface and within its pores. The internal reinforcement column 33 primarily serves to strengthen the structural strength of the activated carbon plate. The central electrode 34 is located within the internal reinforcement column in the middle of the activated carbon plate. When powered on, the central electrode generates an electric field around the activated carbon plate. This electric field aligns polar organic solvent molecules in the exhaust gas, making them more easily adsorbed on the activated carbon plate surface. It also induces polarization in non-polar molecules, enhancing their adsorption to the activated carbon plate. Furthermore, the electric field alters the charge distribution on the activated carbon plate surface, increasing adsorption sites and further improving the plate's adsorption efficiency for organic solvents.

[0040] The activated carbon plate 32 is spiral-shaped, with the central electrode 34 positioned along the central axis of the spiral. The spiral design of the activated carbon plate 32 eliminates the need for a straight line for exhaust gas flowing through the plate within the tank, allowing it to snake along a spiral path. This significantly prolongs the contact time between the exhaust gas and the activated carbon plate, allowing the organic solvent molecules in the exhaust gas more opportunities to fully contact the surface and pores of the activated carbon plate, thereby increasing the probability of organic solvent adsorption and enhancing the adsorption effect.

[0041] The central electrode 34 is arranged on the central axis of the spiral activated carbon plate 32, and the electric field generated after power is applied can radiate to the surroundings in a relatively uniform manner. Since the activated carbon plate is spirally wrapped around the electrode, this layout allows the electric field to penetrate the entire activated carbon plate more evenly, ensuring that each part can be affected by the electric field, so that the organic solvent molecules at different positions of the activated carbon plate can be subjected to a relatively consistent adsorption force enhancement effect, thereby improving the uniformity and overall efficiency of adsorption. The position of the central axis enables the electric field force to act effectively along the radial direction of the spiral activated carbon plate. For polar organic solvent molecules in the exhaust gas, they will move radially toward the surface of the activated carbon plate under the action of the electric field force, making them more easily adsorbed; for non-polar molecules, they can also be better affected by the polarization induced by the electric field and be adsorbed, giving full play to the strengthening effect of the electric field on the adsorption process.

[0042] The interlayer electrode 35 is a metal sheet, which is spirally embedded in the interior of the activated carbon plate 32. The interlayer electrode 35 is made of metal sheet, which can effectively conduct current and ensure that the expected electric field effect can be generated after power is applied or induced charging. At the same time, the relatively thin nature of the metal sheet makes it easier to bend it into a shape that matches the spiral activated carbon plate, making it convenient for embedded installation inside the activated carbon plate. The interlayer electrode 35, which is spirally embedded in the interior of the activated carbon plate, further optimizes the electric field distribution inside the activated carbon plate by cooperating with the central electrode 34 on the central axis. When the central electrode is energized to generate an electric field, the interlayer electrode will be charged due to electrostatic induction, forming a more complex and detailed electric field network inside the activated carbon plate. This electric field network can penetrate into each tiny pore area of the activated carbon plate, so that the adsorption process of organic solvent molecules inside the activated carbon plate is subject to more comprehensive and precise electric field regulation, further improving the adsorption efficiency.

[0043] The electric field formed by the interlayer electrodes 35 works synergistically with the electric field of the central electrode 34, providing a stronger driving force for the adsorption of organic solvent molecules in the exhaust gas, both polar and non-polar. For example, polar molecules are more firmly adsorbed to the activated carbon plate due to the combined effects of electric field forces from different directions. This synergistic electric field also enhances the likelihood of adsorption of non-polar molecules, thereby improving the entire activated carbon plate's adsorption capacity for organic solvents.

[0044] Example 1: Waste gas containing alkane solvents

[0045] Process flow:

[0046] Source of waste gas: The waste gas primarily comes from the solvent processing section of a chemical plant. The waste gas primarily contains alkane solvents (such as n-hexane and n-heptane), with a solvent concentration of approximately 1500-2000 mg / m³.

[0047] S1: Pretreatment: The exhaust gas passes through a high-efficiency filter to remove particulate matter, ensuring that the particulate matter content is less than 5 mg / m³. The exhaust gas temperature is then adjusted to 28°C and the humidity is adjusted to 65% through a temperature and humidity control device.

[0048] S2 Primary Adsorption: Exhaust gas enters the primary adsorption tank and comes into contact with the spiral activated carbon plates, undergoing physical adsorption. Alkane solvent molecules are effectively adsorbed through physical adsorption. Other exhaust gases after adsorption are discharged directly through the chimney.

[0049] Electric field-assisted adsorption: An electric field (with an intensity of 7 kV / m) was applied inside the activated carbon plate to enhance the adsorption of alkane solvents.

[0050] S3 desorption:

[0051] Steam desorption: When the activated carbon plate is saturated with adsorption, the hot steam (120°C) generated by the steam furnace enters the primary adsorption tank, exchanges heat with the solvent molecules, and promotes the desorption of the solvent from the activated carbon surface.

[0052] Vacuum desorption: The pressure in the adsorption tank is reduced to 80 mbar by a vacuum adsorption pump to accelerate the desorption of the solvent.

[0053] Electric field adjustment: The direction of the electric field was reversed and the intensity was reduced to 3 kV / m, further reducing the adsorption force between the solvent and activated carbon and promoting desorption.

[0054] S4 Condensation: The temperature inside the condenser is controlled at 8°C. Cold water acts as a cooling medium to remove the heat from the solvent vapor, turning the toluene, acetone and ethanol vapors into liquid.

[0055] S5 Super Gravity Separation: The liquid mixture enters the super gravity separation equipment, and under the action of 800G centrifugal force, a small amount of impurities and water in the solvent are effectively separated.

[0056] S6 Solvent Recovery: After ultra-gravity separation, the purity of toluene, acetone and ethanol solvents reaches 98.5% and is transported to the solvent recovery tank for storage and can be reused in production.

[0057] Example 2: Waste gas containing aromatic hydrocarbon solvents

[0058] Process flow:

[0059] Source of waste gas: The waste gas comes from a printing factory, which uses aromatic hydrocarbon solvents (such as benzene, toluene, and xylene) in its production process. The solvent concentration in the waste gas is approximately 3,000-5,000 mg / m³.

[0060] S1 pretreatment: Filtration and temperature and humidity adjustment: The exhaust gas passes through a high-efficiency filter to remove particulate matter, and the particulate matter content is less than 5mg / m³. The temperature and humidity adjustment device controls the exhaust gas temperature at 30℃ and the humidity at 60%.

[0061] S2 primary adsorption: The exhaust gas enters the primary adsorption tank and comes into contact with the spiral activated carbon plate. The aromatic hydrocarbon solvent molecules are adsorbed on the surface of the activated carbon through physical adsorption.

[0062] Electric field-assisted adsorption: An electric field (with a strength of 9 kV / m) is applied within the activated carbon plate to enhance the adsorption of aromatic hydrocarbon solvents, especially those with strong polarity (such as benzene and toluene).

[0063] S3 secondary adsorption:

[0064] Solvent characteristics: Since the waste gas contains some smaller molecular weight, low polarity alkane solvents (such as alkanes, cycloalkanes, etc.) in addition to aromatic hydrocarbon solvents, secondary adsorption is required for further treatment.

[0065] Exhaust gas enters the secondary adsorption tank: Exhaust gas enters the secondary adsorption tank through the outlet of the primary adsorption tank, where it comes into contact with the separation membrane. The pore size and properties of the separation membrane are tailored to the size and polarity of solvent molecules, trapping aromatic hydrocarbons (such as benzene and toluene) while allowing other small molecule solvents (such as alkanes) to pass through the membrane. The separated exhaust gas is discharged through the chimney.

[0066] S4 desorption stage:

[0067] Steam desorption: When the adsorption capacity of the activated carbon plate reaches saturation, the steam furnace (120°C) releases hot steam into the first-stage adsorption tank to desorb the solvent.

[0068] Vacuum desorption: The pressure in the adsorption tank is reduced to 50-80 mbar by a vacuum adsorption pump to promote the desorption of the solvent.

[0069] Electric field adjustment: Adjust the direction and intensity of the electric field to further promote the desorption of the solvent from the activated carbon surface and separation membrane.

[0070] S5 Condensation:

[0071] The temperature inside the condenser is controlled at 7°C, and the refrigerant takes away the heat of the solvent vapor, turning the solvent vapor into liquid.

[0072] S6 Super Gravity Separation:

[0073] The liquid mixture enters the ultra-gravity separation equipment, where the impurities and water in the solvent are separated under the action of 700G centrifugal force, with the separation purity reaching 93%.

[0074] S7 Solvent Recovery:

[0075] After ultra-gravity separation, the toluene, n-hexane, acetone, cyclohexane, and ethyl acetate solvents reach a purity of 99% and are transported to a solvent recovery tank for storage and reuse in production. Meanwhile, the waste gas, treated in a secondary adsorption tank, meets emission standards and is discharged through a chimney.

[0076] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A method for recovering waste gas solvents, comprising the following steps: S1 pretreatment: the waste gas containing solvent is passed into the pretreatment mechanism for filtration and temperature and humidity adjustment; S2 primary adsorption: The pretreated exhaust gas is passed into the primary adsorption tank and adsorbed by activated carbon plates and electric field enhancement; S3 secondary adsorption: the waste gas enters the secondary adsorption tank, and the low-grade and small-molecule solvents are separated by the separation membrane, and the waste gas is discharged through the chimney; S4 desorption: Steam is introduced into the first-stage adsorption tank for 15-30 minutes to perform decompression desorption while adjusting the direction and intensity of the electric field; S5 condensation: condensing the desorbed mixed gas in a condensation mechanism; S6 separation: the condensed mixed liquid is separated in a super gravity separation mechanism; S7 Solvent Recovery: The separated high-purity solvent is transported to the solvent recovery tank for storage and subsequent use; In the S2 primary adsorption step, the primary adsorption tank includes a tank body, an activated carbon plate is fixed inside the tank body, the activated carbon plate is spiral-shaped, a central electrode is fixed to the central axis of the activated carbon plate, an internal reinforcement column is provided in the middle, a central electrode is provided in the middle of the internal reinforcement column, an interlayer electrode is embedded in the interior of the activated carbon plate, and both ends of the central electrode are connected to a reversible power supply; In the S4 desorption step, the steam temperature is controlled to be 120-150° C., the electric field strength is controlled to be 3-5 kV / m, and the direction of the electric field is opposite to that in the S2 primary adsorption step.

2. The method for recovering waste gas solvent according to claim 1, characterized in that: In the S1 pretreatment step, the temperature of the exhaust gas is controlled at 25-30° C., and the humidity is controlled at 60%-80%.

3. The method for recovering waste gas solvent according to claim 1, characterized in that: In the S2 primary adsorption step, the exhaust gas flow rate is controlled at 2000 m³ / h, the specific surface area of the activated carbon plate is controlled at 1500 m² / g, the porosity is greater than 80%, and the intensity of the electric field is controlled at 5-10 kV / m.

4. The method for recovering waste gas solvent according to claim 1, characterized in that: In the desorption step S4, the pressure of the adsorption tank is controlled at 50-80 mbar during the reduced pressure desorption.

5. The method for recovering waste gas solvent according to claim 1, characterized in that: In the S5 condensation step, the condensation temperature is controlled to be 5-10°C.

6. The method for recovering waste gas solvent according to claim 1, characterized in that: In the S6 separation step, the centrifugal force of the ultra-gravity separation device is 500-1000G.

Images