A methylene chloride recycling purification system

Abstract

This invention discloses a dichloromethane recovery and purification system, comprising a liquid recovery section and a gas recovery section. In the liquid recovery section, solid impurities are removed from the waste liquid via a filtration assembly, and the liquid is then fed into a separation tank equipped with a heating device. The difference in boiling points between dichloromethane and the impurities is used for evaporation and separation. The vaporized dichloromethane is then condensed and recovered via a first condensation system. The gas recovery section treats the non-condensable dichloromethane gas generated during liquid recovery. Its core component is an adsorption box containing adsorbent material, used to adsorb dichloromethane from the gas. After adsorption saturation, desorption and regeneration are performed by introducing steam. The desorbed mixed gas is condensed via a second condensation system and then enters a dichloromethane stratification tank for liquid-liquid separation, thereby recovering high-purity dichloromethane. This invention, through a closed-loop design of liquid-gas dual recovery, achieves efficient and thorough recovery and reuse of waste dichloromethane, significantly reducing production costs and environmental pollution.

Description

Technical Field

[0001] This utility model relates to the field of waste liquid treatment and recycling technology, and more specifically, to a dichloromethane recovery, utilization and purification system. Background Technology

[0002] In the wet process of lithium battery separator production, dichloromethane is widely used as an extractant due to its excellent solubility and non-flammability to extract pore-forming agents (such as white oil) from the separator, thereby forming a microporous structure. However, during the production process, especially in the event of equipment failure, waste dichloromethane contaminated with other substances can be generated.

[0003] The contaminated dichloromethane cannot be directly reused in production and typically requires treatment by specialized environmental companies. Currently, the most common treatment method in the industry is to dilute it extensively with water before sending it to a wastewater treatment plant, where it is degraded by microorganisms in a biological treatment tank. However, dichloromethane has a very stable chemical structure and a long biodegradation cycle, resulting in extremely low treatment efficiency. For example, a wastewater treatment plant with a capacity of thousands of tons can often only effectively treat a few hundred kilograms of waste dichloromethane per day. This treatment method is not only inefficient but also expensive in terms of dilution and biological treatment, and it also carries the potential risk of environmental pollution due to improper handling.

[0004] Therefore, how to provide a recycling system that can efficiently recover and purify waste dichloromethane, realize resource recycling, and reduce production costs and environmental pollution risks has become a technical problem that urgently needs to be solved in this field. Utility Model Content

[0005] The purpose of this invention is to provide a dichloromethane recovery and purification system to solve the problems of low efficiency, high cost and environmental risks in the treatment of waste dichloromethane mentioned in the background art.

[0006] This utility model provides a dichloromethane recovery, utilization, and purification system, comprising:

[0007] The liquid recovery section is used for the preliminary purification of waste dichloromethane liquid containing impurities; and

[0008] The gas recovery section is connected to the subsequent process of the liquid recovery section and is used to recover dichloromethane gas that failed to condense during the liquid purification process.

[0009] The liquid recovery section includes:

[0010] A filter assembly and a separation tank are connected in sequence. The filter assembly is used to remove solid impurities from waste dichloromethane liquid.

[0011] The separator is equipped with a heating device to heat the filtered waste dichloromethane mixture to a temperature above the vaporization temperature of dichloromethane but below the vaporization temperature of the impurities, so that the dichloromethane vaporizes and is discharged from the top of the tank, while the liquid impurities remain at the bottom of the tank.

[0012] The first condensation system, connected to the top outlet of the separator, is used to condense the vaporized dichloromethane into a liquid state.

[0013] The gas recovery section is connected to the gas outlet of the first condensation system and is used to receive and process the dichloromethane noncondensable gas that has not been condensed in the first condensation system.

[0014] The gas recovery section includes:

[0015] An adsorption box, filled with adsorption material, is used to adsorb dichloromethane gas. The inlet of the adsorption box is connected to the gas outlet of the first condensation system.

[0016] A steam regeneration device is used to introduce steam into the adsorption box to desorb the dichloromethane adsorbed on the adsorption material and discharge it with the steam.

[0017] The second condensation system is connected to the regeneration outlet of the adsorption box and is used to condense the desorbed dichloromethane and water vapor mixture.

[0018] as well as

[0019] The dichloromethane separation tank is connected to the outlet of the second condensation system. It is used to separate and purify dichloromethane by using the density difference and immiscibility between dichloromethane and water to separate the condensed liquid.

[0020] Optionally, the liquid recovery section also includes:

[0021] A waste liquid pump, located before the filter assembly, is used to extract waste dichloromethane liquid from the waste dichloromethane tank and pump it into the filter assembly.

[0022] The filtration assembly includes a bag filter and a precision filter connected in sequence.

[0023] Optionally, the separator is equipped with a temperature probe and a level gauge, and the heating device is a heating coil located inside the separator. The top of the separator is equipped with an exhaust port for discharging vaporized dichloromethane, and the bottom is equipped with a waste liquid vent for discharging residual waste liquid.

[0024] Optionally, the first condensation system includes a cooling water condenser and a chilled water condenser connected in sequence.

[0025] Optionally, the liquid recovery section also includes:

[0026] A first collection tank, connected to the liquid outlet of the first condensation system, is used to collect condensed liquid dichloromethane; and

[0027] The first pump, whose inlet is connected to the first collection tank, and whose outlet can be selectively connected to the inlet of a dichloromethane tank or a separation tank, is used to transport qualified dichloromethane to the dichloromethane tank or to send unqualified dichloromethane back to the separation tank for further purification.

[0028] Optionally, the adsorption box is equipped with a loss scale to monitor the weight change of the adsorption material after adsorbing dichloromethane, so as to determine whether it has reached adsorption saturation.

[0029] Optionally, the second condensing system includes a primary condenser and a secondary condenser connected in sequence.

[0030] Optionally, a second pump is connected to the bottom of the dichloromethane stratification tank to transport the dichloromethane in the lower layer of the stratification tank to the dichloromethane tank; an overflow port is provided at the top of the dichloromethane stratification tank to discharge the water in the upper layer into the sewage treatment system.

[0031] Optionally, the adsorbent material is carbon fiber.

[0032] Based on the technical content disclosed in this utility model, the following beneficial effects are achieved:

[0033] The dichloromethane recovery and purification system provided by this invention utilizes the significant boiling point difference between dichloromethane and common impurities (such as water and oil) in a separation tank through a liquid recovery section, enabling precise evaporation and separation. This step efficiently vaporizes over 90% of the dichloromethane in the waste liquid and performs a first-round condensation recovery, while concentrating and centrally treating high-boiling-point impurities, greatly reducing the load on subsequent wastewater treatment. Secondly, for the non-condensable dichloromethane gas generated during the first-round condensation process, which is difficult to handle by traditional processes, this system innovatively incorporates a gas recovery section. This section utilizes the highly efficient adsorption of dichloromethane by adsorbent materials to capture it, and then, through steam desorption-condensation-stratification, almost completely converts this gas into pure liquid dichloromethane for recovery. This two-stage recycling model, which combines liquid and gas, forms a closed-loop and highly efficient purification process. It not only enables the recycling of waste dichloromethane, significantly reducing the consumption of raw materials and the research and development and production costs of lithium batteries, but also eliminates the emission of dichloromethane at the source, reducing environmental pollution. It has extremely high economic benefits and environmental value.

[0034] Other features and advantages of the present invention will become clear from the following detailed description of exemplary embodiments of the present invention with reference to the accompanying drawings. Attached Figure Description

[0035] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments of the present invention and, together with their description, serve to explain the principles of the present invention.

[0036] Figure 1 This is a schematic diagram of the structure of one embodiment of the present invention.

[0037] Figure 2 for Figure 1 A schematic diagram of the intermediate separation tank.

[0038] Figure 3 for Figure 1 A schematic diagram of the adsorption chamber.

[0039] Explanation of reference numerals in the attached diagram: 1. Waste dichloromethane tank; 2. Waste liquid pump; 3. Bag filter; 4. Precision filter; 5. Separation tank; 501. Waste liquid inlet; 502. Dichloromethane vent; 503. Waste liquid drain hole; 504. Internal heating coil; 505. Level gauge; 506. Temperature probe; 6. Cooling water condenser; 7. Chilled water condenser; 8. First collection tank; 9. First pump; 10. Waste liquid tank; 11. Dichloromethane tank; 12. Adsorption tank; 1201. Carbon fiber filter element; 1202. Inlet valve; 1203. Exhaust valve; 1204. Steam valve; 1205. Regeneration valve; 1206. Temperature sensor; 13. Loss-in-weight scale; 14. First-stage condenser; 15. Second-stage condenser; 16. Dichloromethane stratification tank; 17. Second pump. Detailed Implementation

[0040] Various exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. It should be noted that, unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps set forth in these embodiments do not limit the scope of the present invention.

[0041] The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the invention or its application or use.

[0042] Techniques, methods, and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, they should be considered part of the specification.

[0043] In all the examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values.

[0044] It should be noted that similar labels and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be discussed further in subsequent figures.

[0045] See Figures 1 to 3This utility model provides a dichloromethane recovery and purification system, which is mainly divided into a liquid recovery section and a gas recovery section that are connected to each other.

[0046] I. Liquid Recovery Section

[0047] The core function of the liquid recovery section is to purify most of the dichloromethane in the contaminated waste dichloromethane liquid through evaporation and condensation.

[0048] During on-site operations, the waste dichloromethane drum 1 containing the waste liquid is first transported to the designated location. The waste liquid pump 2 is started to draw the waste liquid from the drum, which then flows sequentially through a bag filter 3 and a precision filter 4. These two filters constitute a filtration assembly used to effectively remove suspended solid particulate impurities from the waste liquid, preventing them from scaling or clogging pipes during subsequent heating.

[0049] The pretreated waste dichloromethane mixture enters separator 5. (Refer to...) Figure 2 Specifically, the pretreated waste dichloromethane mixture is introduced through the waste liquid inlet 501. During the introduction process, the operator observes the level gauge 505. When the level reaches the preset height (e.g., 80 cm), the introduction is stopped. Subsequently, the steam valve is activated to introduce steam into the internal heating coil 504 inside the tank to heat the mixture. The temperature inside the tank is monitored and controlled by the temperature probe 506 to maintain it at approximately 85°C. Since the boiling point of dichloromethane is approximately 39.8°C, while the boiling points of the main impurities in the waste liquid, such as water and white oil, are above 100°C, at this temperature, dichloromethane will rapidly vaporize, while other impurities remain liquid.

[0050] The vaporized dichloromethane is discharged through the dichloromethane vent 502 at the top of the separator 5 and enters the subsequent first condensation system. As evaporation continues, the liquid level in the separator 5 will continuously decrease. When the level gauge 505 shows that the liquid level has dropped to an extremely low position (e.g., below 8 cm) and has not changed for a long time, it can be determined that the dichloromethane in the tank has been basically completely vaporized. At this time, the residue at the bottom of the tank is mainly water, white oil, and various high-boiling-point impurities such as additives that cannot be vaporized. This residual waste liquid is discharged into the waste liquid tank 10 through the waste liquid vent 503 at the bottom, awaiting centralized treatment. Through this step, more than 90% of the dichloromethane in the waste liquid is separated, greatly reducing the total amount of waste liquid sent to the sewage treatment plant and the difficulty of treatment.

[0051] Combination Figure 1The high-temperature dichloromethane gas discharged from the separator 5 enters the first condensation system, which consists of a cooling water condenser 6 and a chilled water condenser 7 connected in series. First, the gas enters the cooling water condenser 6 and undergoes preliminary cooling and condensation using ambient temperature circulating water (e.g., 32-37°C). Subsequently, the mixture enters the chilled water condenser 7 and undergoes deep condensation using low-temperature chilled water (e.g., 7-12°C) to ensure that the vast majority of the dichloromethane gas is converted into a liquid state.

[0052] The condensed liquid dichloromethane flows by gravity into the first collection tank 8. A sample of the liquid in the collection tank is tested. If the purity is acceptable, the first pump 9 is activated to transfer it to the dichloromethane tank 11 for storage, ready for reuse in production. If the test fails, the valve is switched so that the first pump 9 pumps the unacceptable liquid back to the inlet of the separator 5 for further evaporation and purification until it meets the required purity.

[0053] When the first condensation system is working, some dichloromethane gas that cannot be completely condensed, i.e., "non-condensable gas," will inevitably be generated. This gas will be guided through pipelines to the gas recovery section for further treatment.

[0054] II. Gas Recovery Section

[0055] The gas recovery section mainly processes non-condensable gases from the first condensation system of the liquid recovery section to ensure maximum recovery rate of dichloromethane.

[0056] Non-condensable gases are introduced into an adsorption chamber 12 containing adsorbent material. In this preferred embodiment, the adsorbent material is a carbon fiber filter element 1201. (Refer to...) Figure 3 The gas enters the adsorption box 12 through the bottom inlet valve 1202. Utilizing the huge specific surface area of ​​the carbon fiber and its strong adsorption force on dichloromethane molecules, the dichloromethane in the airflow is captured, while other non-condensable gases such as air are discharged through the exhaust valve 1203.

[0057] To precisely control the adsorption process, a loss-in-weight scale 13 is installed at the bottom of the adsorption chamber 12. The loss-in-weight scale 13 includes a weighing sensor located at the bottom of the adsorption chamber 12. The carbon fiber used in this embodiment has an adsorption capacity of up to 30% of its own weight for dichloromethane. To ensure stable operation and regeneration efficiency, the adsorption amount is considered saturated when it reaches 20% of the weight of the carbon fiber filter element. The operator monitors the reading of the loss-in-weight scale 13 in real time. When the total weight increase of the adsorption chamber 12 reaches the preset value, the inlet valve 1202 and the exhaust valve 1203 are immediately closed, and the heating of the separation tank 5 is temporarily stopped to suspend the generation of new dichloromethane vapor.

[0058] Next, the saturated adsorption chamber 12 is regenerated. Steam valve 1204 and regeneration valve 1205 are opened, and high-temperature steam is introduced into the adsorption chamber 12. The hot steam causes the microporous structure of the carbon fibers to expand, disrupting the adsorption equilibrium of dichloromethane molecules. This causes the adsorbed dichloromethane to be released and form a mixed gas with the steam, which is then discharged through regeneration valve 1205. The temperature inside the chamber is monitored by temperature sensor 1206. When the temperature reaches approximately 100°C, it can be considered that the dichloromethane has been largely desorbed, and fiber regeneration is complete.

[0059] The desorbed high-temperature mixed gas enters the second condensation system, which consists of a first-stage condenser 14 and a second-stage condenser 15 connected in series. Its structure and working principle are similar to those of the first condensation system. It also uses cooling water and chilled water for two-stage cooling to completely condense the mixed gas into a liquid state.

[0060] The condensed liquid (mainly water and dichloromethane) enters the dichloromethane stratification tank 16. Based on dichloromethane (density approximately 1.3 g / cm³),... 3 ) and water (density approximately 1.0 g / cm³) 3 Due to their immiscible nature and different densities, the liquids naturally separate into layers within the tank, with the heavier dichloromethane settling at the bottom and the water floating on top. As regeneration continues, the liquid level in the dichloromethane stratification tank 16 rises continuously. When it reaches a high level, the water on top automatically overflows through the overflow port and enters the wastewater system for treatment. The pure dichloromethane at the bottom, after passing sampling and testing, is then pumped via the second pump 17 to the final dichloromethane tank 11, achieving the liquefaction and recovery of this gas. If the test fails, it can be pumped back to the upstream separation tank 5 for further treatment.

[0061] After one adsorption tank completes regeneration, close the steam valve 1204 and regeneration valve 1205, and reopen the inlet valve 1202 and exhaust valve 1203 to begin the next round of adsorption. The system can be equipped with two or more adsorption tanks that work alternately to achieve continuous and uninterrupted exhaust gas treatment.

[0062] In summary, this invention organically combines the liquid recovery section and the gas recovery section. First, it efficiently recovers most of the dichloromethane from the waste liquid through evaporation and condensation. Then, it replenishes and recovers the non-condensable gases generated during the process through adsorption and regeneration, thus forming a complete closed-loop recovery system. This system not only solves the waste liquid treatment problem and realizes resource recycling, but also has a clear structure, is feasible to operate, and has high industrial practical value.

[0063] Although specific embodiments of the present invention have been described in detail by way of examples, those skilled in the art should understand that the above examples are for illustrative purposes only and are not intended to limit the scope of the present invention. Those skilled in the art should understand that modifications can be made to the above embodiments without departing from the scope and spirit of the present invention. The scope of the present invention is defined by the appended claims.

Claims

1. A dichloromethane recovery and purification system, characterized in that, include: The liquid recovery section is used for the preliminary purification of waste dichloromethane liquid containing impurities; as well as The gas recovery section is connected to the subsequent process of the liquid recovery section and is used to recover dichloromethane gas that failed to condense during the liquid purification process. The liquid recovery section includes: A filter assembly and a separation tank are connected in sequence, wherein the filter assembly is used to remove solid impurities from waste dichloromethane liquid; The separation tank is equipped with a heating device to heat the filtered waste dichloromethane mixture to a temperature above the vaporization temperature of dichloromethane but below the vaporization temperature of the impurities, so that the dichloromethane is vaporized and discharged from the top of the tank, while the liquid impurities remain at the bottom of the tank. The first condensation system is connected to the top outlet of the separator and is used to condense the vaporized dichloromethane into a liquid state. The gas recovery section is connected to the gas outlet of the first condensation system and is used to receive and process the dichloromethane noncondensable gas that has not been condensed in the first condensation system. The gas recovery section includes: An adsorption box, filled with adsorption material, is used to adsorb dichloromethane gas. The inlet of the adsorption box is connected to the gas outlet of the first condensation system. A steam regeneration device is used to introduce steam into the adsorption box to desorb the dichloromethane adsorbed on the adsorption material and discharge it together with the steam. The second condensation system is connected to the regeneration outlet of the adsorption box and is used to condense the desorbed dichloromethane and water vapor mixture. as well as The dichloromethane separation tank is connected to the outlet of the second condensation system. It is used to separate and purify the condensed liquid by utilizing the density difference and immiscibility between dichloromethane and water.

2. The system according to claim 1, characterized in that, The liquid recovery section also includes: A waste liquid pump, located before the filter assembly, is used to extract waste dichloromethane liquid from the waste dichloromethane tank and pump it into the filter assembly; The filtration assembly includes a bag filter and a precision filter connected in sequence.

3. The system according to claim 1, characterized in that, The separation tank is equipped with a temperature probe and a level gauge, and the heating device is a heating coil located inside the tank. The top of the separation tank is provided with an exhaust port for discharging vaporized dichloromethane, and the bottom is provided with a waste liquid vent for discharging residual waste liquid.

4. The system according to claim 1, characterized in that, The first condensation system includes a cooling water condenser and a chilled water condenser connected in sequence.

5. The system according to claim 1 or 4, characterized in that, The liquid recovery section also includes: A first collection tank, connected to the liquid outlet of the first condensation system, is used to collect condensed liquid dichloromethane; and A first pump, whose inlet is connected to the first collection tank, and whose outlet can be selectively connected to the inlet of the dichloromethane tank or the separator, is used to transport qualified dichloromethane to the dichloromethane tank or to send unqualified dichloromethane back to the separator for further purification.

6. The system according to claim 1, characterized in that, The adsorption box is equipped with a weight loss scale to monitor the weight change of the adsorption material after adsorbing dichloromethane, so as to determine whether it has reached adsorption saturation.

7. The system according to claim 1, characterized in that, The second condensation system includes a primary condenser and a secondary condenser connected in sequence.

8. The system according to claim 1, characterized in that, The bottom of the dichloromethane stratification tank is connected to a second pump for transporting the dichloromethane in the lower layer of the dichloromethane stratification tank to the dichloromethane tank; the upper part of the dichloromethane stratification tank is provided with an overflow port for discharging the upper layer of water into the sewage treatment system.

9. The system according to claim 1, characterized in that, The adsorbent material is carbon fiber.

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