A solvent recovery system

Abstract

The application relates to a solvent recovery system. The system comprises a pre-distillation unit, a water washing tower and a solvent recovery unit. The pre-distillation unit is used for distilling the solvent, and the pre-distillation unit will emit purge gas during the distillation process. The water washing tower is provided with a purge gas inlet, and the water washing tower is connected with the pre-distillation unit through the purge gas inlet. The solvent recovery unit comprises a recovery tower, a first reboiler, a first condenser, a first reflux tank and a solvent reflux pipe. The first reboiler heats the washing liquid to generate mixed gas containing methanol, the mixed gas is condensed through the first condenser and is subjected to gas-liquid separation through the first reflux tank, and the methanol gas is returned to the pre-distillation cycle through the solvent reflux pipe. Through the solvent recovery unit, the methanol in the purge gas can be recovered and re-injected into the methanol pre-distillation cycle.

Description

Technical Field

[0001] This application relates to the field of distillation technology, and in particular to a solvent recovery system. Background Technology

[0002] In the MTO-grade methanol synthesis process, crude methanol contains a significant amount of light components such as CO2 and H2. To remove these light components, the crude methanol must first undergo flash distillation in an expander to remove some of them, and then proceed to a pre-distillation column for further removal of these light components to obtain MTO-grade methanol. During the distillation process, the exhaust gas from the pre-distillation column still contains a considerable amount of methanol gas. Currently, this methanol-containing exhaust gas is sent to a flare system or incinerator for combustion. Whether it enters a flare system or an incinerator, the methanol is ultimately burned directly, which represents a significant waste of methanol resources.

[0003] In related technologies, a washing and absorption device is set up to wash the tail gas with demineralized water to obtain a liquid containing methanol, and this liquid is then returned to the pre-distillation tower, thereby reducing methanol waste.

[0004] However, the methanol recovered in the above method has a high water content, and its reflux into the distillation column will significantly affect the water content of the methanol in the pre-distillation column, thus affecting the quality of MTO-grade methanol. Utility Model Content

[0005] Therefore, it is necessary to provide a solvent recovery system to address the problem of high water content in the methanol recovered in related technologies.

[0006] A solvent recovery system includes a pre-distillation unit, a water washing tower, and a solvent recovery unit. The pre-distillation unit is used to distill the solvent, and during the distillation process, it emits purge gas. The water washing tower has a purge gas inlet, and the pre-distillation unit is connected to the water washing tower through this inlet. The solvent recovery unit includes a recovery tower, a first reboiler, a first condenser, a first reflux tank, and a solvent reflux pipe. The recovery tower has a first liquid inlet, and the water washing tower is connected to the recovery tower through this inlet. The first reboiler is located at the bottom of the recovery tower and is in communication with it. The first condenser is connected to the top of the recovery tower. The first reflux tank has a first gas inlet and a first gas outlet. The first condenser is connected to the first reflux tank through the first gas inlet, and the first reflux tank also has a first liquid outlet. The first recovery tower is connected to the first reflux tank through the first liquid outlet. One end of the solvent reflux pipe is connected to the first gas outlet, and the other end is connected to the pre-distillation unit.

[0007] In one embodiment, the pre-distillation unit includes a pre-distillation column, a second condenser, and a third condenser. The pre-distillation column is used to contain the solvent. The second condenser is connected to the pre-distillation column and is used to cool the gas discharged from the pre-distillation column. The third condenser is connected to the second condenser and is also connected to a water washing column via a purge gas inlet; the third condenser is used to cool the gas discharged from the second condenser.

[0008] In one embodiment, the cooling temperature of the second condenser is greater than or equal to 50°C and less than 70°C, and the cooling temperature of the third condenser is greater than or equal to 40°C and less than 50°C.

[0009] In one embodiment, the cooling temperature of the first condenser is greater than or equal to 70°C and less than 80°C.

[0010] In one embodiment, the solvent recovery unit further includes a first discharge pump, which is located at the bottom of the recovery tower and connected to the recovery tower, for pumping out the waste liquid in the recovery tower.

[0011] In one embodiment, the solvent recovery unit further includes a gas detection device disposed on the outer wall of the solvent return pipe for detecting the concentration of solvent gas.

[0012] In one embodiment, the solvent recovery unit further includes a flow retarder, which is disposed inside the solvent return pipe. The flow retarder is plate-shaped, and its outline shape is the same as the radial cross-sectional shape of the return pipe. The flow retarder is also provided with through holes evenly distributed on it.

[0013] In one embodiment, the through hole is a tapered hole, and the diameter of the tapered hole gradually increases along the direction of the solvent reflux pipe near the end of the first reflux tank and the direction of the solvent reflux pipe near the end of the pre-distillation unit.

[0014] In one embodiment, a heat insulation layer is provided on the outer peripheral surface of the solvent reflux pipe.

[0015] In one embodiment, a drain valve is also provided on the solvent reflux pipe.

[0016] In one embodiment, the solvent reflux pipe includes a first pipe section and a second pipe section, wherein the first pipe section has a first end and a second end, and the second pipe section has a third end and a fourth end. The first end is connected to a first gas outlet, the second end is connected to the third end, and the fourth end is connected to a pre-distillation unit. The horizontal height of the first end is less than the horizontal height of the second end, and the horizontal height of the third end is greater than the horizontal height of the fourth end.

[0017] The solvent recovery system described above can heat the washing liquid in the recovery tower through a first reboiler located at the bottom of the recovery tower, generating methanol-rich vapor. This vapor flows out of the recovery tower and into a first condenser, where it cools the vapor, causing most of the water to condense and reducing its water content. Further, the cooled vapor undergoes gas-liquid separation in a first reflux tank. The liquid flows back into the recovery tower through a first drain port, while the high-purity methanol vapor flows into a solvent reflux pipe through a first outlet and then back to the pre-distillation unit to continue participating in the methanol distillation cycle, thus achieving the recovery and utilization of methanol in the purge gas. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of a solvent recovery system provided in an embodiment of this application.

[0019] Figure 2 This is one of the schematic diagrams of the flow-retarding element provided in the embodiments of this application.

[0020] Figure 3 This is a second schematic diagram of the flow-retarding element provided in the embodiments of this application.

[0021] Figure 4 This is the third schematic diagram of the flow-retarding element provided in the embodiments of this application.

[0022] Figure 5 This is a schematic diagram of the solvent reflux tube provided in an embodiment of this application.

[0023] Figure label: Solvent recovery system-100;

[0024] Pre-distillation unit-1; Pre-distillation column-11; Pre-column reboiler-12; Condensation assembly-13; Second condenser-131; Third condenser-132; Pre-column reflux tank-14; Pre-column reflux pump-140; Pre-column reflux tank inlet-141; Pre-column reflux tank outlet-142;

[0025] Water scrubbing tower-2; vent gas inlet-20; scrubbing liquid outlet-21;

[0026] Solvent recovery unit-3; recovery tower-31; first liquid inlet-310; recovery tower feed pump-301; first reboiler-32; first condenser-33; first reflux tank-34; recovery tower reflux pump-340; first air inlet-341; first air outlet-342; first drain outlet-343; solvent reflux pipe-35; first pipe section-3501; first end-35011; second end-35012; second pipe section-3502; third end-35021; fourth end-35022; insulation layer-350; drain valve-351; first drain pump-4;

[0027] First connecting pipe - 1001; Second connecting pipe - 1002; Third connecting pipe - 1003; Fourth connecting pipe - 1004; Fifth connecting pipe - 1005; Gas detection device - 5; Flow retardant - 6; Through hole - 60; First hole section - 601; Second hole section - 602. Detailed Implementation

[0028] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, the specific embodiments of this application are described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of this application. However, this application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of this application. Therefore, this application is not limited to the specific embodiments disclosed below.

[0029] In the description of this application, it should be understood that if terms such as "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential" appear, these terms indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0030] Furthermore, where the terms "first" and "second" appear, these terms are for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined with "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, where the term "multiple" appears, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0031] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "joining," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise expressly limited. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0032] In this application, unless otherwise expressly specified and limited, the use of descriptions such as "above" or "below" the second feature indicates that the first and second features are in direct contact or indirect contact via an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. Similarly, "below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0033] It should be noted that if an element is referred to as being "fixed to" or "set on" another element, it can be directly on the other element or there may be an intervening element. If an element is considered to be "connected to" another element, it can be directly connected to the other element or there may be an intervening element. If so, the terms "vertical," "horizontal," "upper," "lower," "left," "right," and similar expressions used in this application are for illustrative purposes only and do not represent the only possible implementation.

[0034] See Figure 1 , Figure 1 A schematic diagram of a solvent recovery system 100 according to an embodiment of this application is shown. The following description uses methanol as the solvent.

[0035] The solvent recovery system 100 mainly includes a pre-distillation unit 1, which is used to distill crude methanol (solvent). During the distillation process, the pre-distillation unit 1 emits purge gas. In addition to light components such as CO2 and H2, the purge gas emitted during the distillation of crude methanol by the pre-distillation unit 1 also contains methanol gas. It should be noted that when the solvent is another substance, the impurity gases in the purge gas may not be CO2 or H2, and it is understandable that the purge gas contains gases corresponding to the solvent.

[0036] To recover methanol gas from the purge gas, the solvent recovery system 100 further includes a water washing tower 2 and a solvent recovery unit 3. The water washing tower 2 is provided with a purge gas inlet 20, and the pre-distillation unit 1 is connected to the water washing tower 2 through the purge gas inlet 20.

[0037] In this way, the purge gas discharged from the pre-distillation unit 1 can enter the water washing tower 2 through the purge gas inlet 20, where the demineralized water in the water washing tower 2 is used to wash the purge gas, dissolving the methanol gas in the purge gas in the demineralized water and achieving methanol recovery. The water washing tower 2 then sends the washing liquid to the solvent recovery unit for collection. It should be noted that when the solvent is methanol, demineralized water is used in the water washing tower 2 to wash the purge gas. When the solvent is another substance, a suitable detergent can be selected to wash the purge gas based on the physical and chemical properties of the solvent.

[0038] In some embodiments of this application, the pre-distillation unit 1 is connected to the purge gas inlet 20 of the water washing tower 2 via a gas supply pipe, so that the purge gas enters the interior of the water washing tower 2 and comes into contact with the demineralized water in the water washing tower 2. Furthermore, the purge gas inlet 20 can be located at the bottom of the water washing tower 2, and the demineralized water can be sprayed from the top of the water washing tower 2 through a spray device. This allows the purge gas and demineralized water to come into countercurrent contact, enabling more thorough contact between them and allowing the methanol in the purge gas to fully dissolve into the demineralized water.

[0039] As described above, after the purge gas is washed by the water washing tower 2, a washing liquid containing methanol is obtained. This methanol-containing washing liquid is then transported to the solvent recovery unit 3. It should be noted that when the solvent is another substance, the washing liquid is a solution formed by the substance corresponding to the solvent.

[0040] The solvent recovery unit 3 will be further explained below. (See attached document) Figure 1 The solvent recovery unit 3 includes a recovery tower 31, which is provided with a first liquid inlet 310. The recovery tower 31 is connected to the water washing tower 2 through the first liquid inlet 310, so as to collect the washing liquid containing methanol in the water washing tower 2.

[0041] In some embodiments, a washing liquid outlet 21 can be provided at the bottom of the washing tower 2, and then a delivery pipe can be used to connect the washing liquid outlet 21 and the first inlet 310. In this way, when the washing tower 2 is positioned higher than the recovery tower, the washing liquid can flow into the recovery tower 31 by its own weight through the delivery pipe. Furthermore, a recovery tower feed pump 301 can be installed in the middle of the delivery pipe between the washing tower 2 and the recovery tower 31. When there is no height difference between the washing tower 2 and the recovery tower 31, the washing liquid in the washing tower 2 can be forcibly transported into the recovery tower 31 by the recovery tower feed pump 301. This makes the placement of the washing tower 2 and the recovery tower 31 more flexible and adaptable to different construction sites.

[0042] Based on this, the solvent recovery unit 3 provided in this embodiment further includes a first reboiler 32, a first condenser 33, a first reflux tank 34, and a solvent reflux pipe 35. The washing liquid containing methanol in the recovery tower 31 is heated by the first reboiler 32 to generate methanol vapor, which is then separated into methanol gas by the first condenser 33 and the first reflux tank 34. The methanol gas is then returned to the pre-distillation unit 1 through the solvent reflux pipe 35 to continue participating in the methanol distillation cycle.

[0043] The methanol recovery process described above will be further explained below. The first reboiler 32 is located at the bottom of the recovery tower 31 and is connected to the recovery tower 31. Based on this, the first condenser 33 is connected to the top of the recovery tower 31. The first reflux tank 34 is provided with a first inlet 341 and a first outlet 342.

[0044] The first condenser 33 is connected to the first reflux tank 34 via the first air inlet 341. The first reflux tank 34 is also provided with a first drain port 343, which is connected to the recovery tower 31. Furthermore, one end of the solvent reflux pipe 35 is connected to the first air outlet 342, and the other end is connected to the pre-distillation unit 1.

[0045] In this way, the first reboiler 32, located at the bottom of the recovery tower 31, can heat the washing liquid in the recovery tower 31 to generate methanol-rich vapor. This vapor can flow out of the recovery tower 31 and enter the first condenser 33, which cools the vapor, causing most of the water to condense and thus reducing the water content of the vapor. Furthermore, the cooled vapor undergoes further gas-liquid separation in the first reflux tank 34. The liquid flows back into the recovery tower 31 through the first drain port 343, while the high-purity methanol vapor flows into the solvent reflux pipe 35 through the first outlet port 342 and then flows back to the pre-distillation unit 1 along the solvent reflux pipe 35 to continue participating in the methanol distillation cycle.

[0046] In some embodiments of this application, the first reboiler 32 can be connected to the recovery tower 31 via a connecting pipe. For example, a first connecting pipe 1001 and a second connecting pipe 1002 are provided between the recovery tower 31 and the first reboiler 32. One end of the first connecting pipe 1001 is connected to the bottom of the recovery tower 31, and the other end is connected to the first reboiler 32. The first connecting pipe 1001 is used to transport liquid so that the washing liquid collected in the recovery tower 31 can flow into the first reboiler 32, where it is heated to generate vapor containing methanol gas. One end of the second connecting pipe 1002 is connected to the first reboiler 32, and the other end is connected to the recovery tower 31. The second connecting pipe 1002 is used to transport gas so that the gas generated in the first reboiler 32 flows into the recovery tower 31 through the second connecting pipe 1002, and then flows from the recovery tower 31 to the first condenser 33.

[0047] In some embodiments of this application, the first condenser 33 is connected to the recovery tower 31 via a third connecting pipe 1003, and the first condenser 33 is also connected to the first reflux tank 34 via a fourth connecting pipe 1004. One end of the third connecting pipe 1003 is connected to the top of the recovery tower 31, and the other end is connected to the first condenser 33. Thus, the gas in the recovery tower 31 can enter the first condenser 33 through the third connecting pipe 1003, where it is cooled, causing most of the water content to condense into droplets. One end of the fourth connecting pipe 1004 is connected to the first condenser 33, and the other end is connected to the first air inlet 341. Thus, the cooled gas can enter the first reflux tank 34 through the fourth connecting pipe 1004, where further gas-liquid separation occurs to further reduce the water content in the methanol gas.

[0048] In some embodiments of this application, the first reflux tank 34 and the recovery tower 31 are connected by a fifth connecting pipe 1005. One end of the fifth connecting pipe 1005 is connected to the recovery tower 31, and the other end is connected to the first drain port 343. In this way, the liquid generated by gas-liquid separation can flow back into the recovery tower 31 through the fifth connecting pipe 1005. Furthermore, a recovery tower reflux pump 340 can be installed on the fifth connecting pipe 1005 to pump the liquid in the first reflux tank 34 into the recovery tower 31 through the fifth connecting pipe 1005.

[0049] As can be seen from the above, by further processing the washing liquid in the water washing tower 2 through the solvent recovery unit 3, methanol gas with low water content can be obtained, and this part of the methanol gas can be recycled back to the pre-distillation unit 1, so that this part of the methanol gas can continue to participate in the methanol distillation cycle and reduce the waste of methanol resources.

[0050] The pre-distillation unit 1 provided in this application will be further described below, see reference. Figure 1 The pre-distillation unit 1 includes a pre-distillation column 11, a pre-distillation reboiler 12, a condenser assembly 13, and a pre-distillation reflux tank 14. The pre-distillation column 11 is used to contain crude methanol, and the pre-distillation reboiler 12 is located at the bottom of the pre-distillation column 11 and communicates with it. The condenser assembly 13 is connected to the pre-distillation column 11 and is used to cool the gas discharged from the pre-distillation column 11. The pre-distillation reflux tank 14 is provided with a pre-distillation reflux tank inlet 141 and a pre-distillation reflux tank outlet 142. The pre-distillation reflux tank 14 is connected to the condenser assembly 13 through the pre-distillation reflux tank inlet 141, and is connected to the pre-distillation column 11 through the pre-distillation reflux tank outlet 142.

[0051] In this way, when crude methanol feedstock arrives, it can be contained in the pre-distillation column 11. The pre-column reboiler 12 then heats and vaporizes the crude methanol feedstock in the pre-distillation column 11, providing the rising steam required for gas-liquid mass transfer within the column, thus promoting the separation of light components from methanol. Further, the mixture of light component gas and methanol gas enters the condenser assembly 13, which cools the mixture, causing the methanol in the mixture to condense. Thus, a portion of the methanol in the mixture within the condenser assembly 13 is condensed and refluxed into the pre-column reflux tank 14, which is connected to the condenser assembly 13, while the remaining portion is discharged as purge gas along with the light component gas and enters the water washing column 2.

[0052] In some embodiments of this application, the condensation assembly 13 includes a second condenser 131 and a third condenser 132. The second condenser 131 is connected to the pre-distillation column 11 and is used to cool the gas discharged from the pre-distillation column 11. The third condenser 132 is connected to the second condenser 131 and is also connected to the water washing column 2 through a vent inlet 20. The third condenser 132 is used to cool the gas discharged from the second condenser 131.

[0053] Specifically, the second condenser 131 is also connected to the pre-return tank 14, and the gas cooled by the second condenser 131 enters the pre-return tank 14. The third condenser 132 is also connected to the pre-return tank 14, and the third condenser 132 is also connected to the water washing tower 2 through the vent gas inlet 20. Furthermore, the third condenser 132 is connected to the pre-return tank 14 through the pre-return tank inlet 141. The third condenser 132 is used to cool the gas discharged from the pre-return tank 14.

[0054] In this way, the two-stage cooling of the second condenser 131 and the third condenser 132 allows for the complete condensation of methanol vapor in the mixed gas, reducing the methanol content in the purge gas and minimizing waste. Specifically, the mixed gas in the pre-distillation column 11 first flows into the second condenser 131 through a connecting pipe, where it is cooled. The cooled mixed gas then flows through the connecting pipe between the second condenser 131 and the pre-distillation column reflux tank 14 into the pre-distillation column 14. The methanol condensed into liquid in the mixed gas flows out from the outlet 142 of the pre-distillation column reflux tank and flows back into the pre-distillation column 11 through the connecting pipe between the pre-distillation column reflux tank 14 and the pre-distillation column 11. The remaining mixed gas flows out from the pre-distillation column reflux tank 14 and enters the third condenser 132 through the connecting pipe between the pre-distillation column reflux tank 14 and the third condenser 132. The mixed gas is further cooled in the third condenser 132, and the condensed methanol is returned to the pre-recirculation tank 14 through the connecting pipe between the third condenser 132 and the pre-recirculation tank 14, and then returned to the pre-distillation column 11 from the pre-recirculation tank 14. The remaining mixed gas (purge gas) is introduced into the water washing column 2 through the connecting pipe between the third condenser 132 and the water washing column 2.

[0055] In this case, the connection between the solvent reflux pipe 35 and the pre-distillation unit 1 provided in this application can be a connection to the second condenser 131. Specifically, one end of the solvent reflux pipe 35 connected to the pre-distillation unit 1 can be connected to the connecting pipe between the second condenser 131 and the pre-distillation column 11, so that the recovered methanol gas can flow into the second condenser 131 through the connecting pipe to continue participating in the methanol distillation cycle.

[0056] In some embodiments of this application, the pre-recirculation tank 14 is connected to the pre-distillation column 11 via the pre-recirculation tank outlet 142, for example, via a connecting pipe. One end of the connecting pipe is connected to the pre-recirculation tank outlet 142, and the other end is connected to the pre-distillation column 11. Furthermore, a pre-recirculation pump 140 can be installed on the connecting pipe to pump the liquid in the pre-recirculation tank 14 into the pre-distillation column 11, thereby improving the liquid reflux efficiency.

[0057] In some embodiments of this application, the cooling temperature of the second condenser 131 is greater than or equal to 50°C and less than 70°C, and the cooling temperature of the third condenser 132 is greater than or equal to 40°C and less than 50°C.

[0058] In this way, the stepped cooling temperature settings of the second condenser 131 and the third condenser 132 enable finer component separation of the mixed gas, improving the methanol recovery rate and the purity of methanol.

[0059] In some embodiments of this application, the cooling temperature of the first condenser 33 is greater than or equal to 70°C and less than 80°C.

[0060] In this way, the first condenser 33 can quickly condense most of the high-boiling-point components, reducing the cooling load on the reflux to the pre-distillation unit 1, which in turn reduces the condensation load on the second condenser 131. Furthermore, it should be noted that the stepped cooling temperatures of the first condenser 33, the second condenser 131, and the third condenser 132 allow for finer separation and improved methanol gas purity. Additionally, the step-by-step cooling of the gas effectively reduces the load on the condensation equipment.

[0061] It should be noted that the cooling temperature range of the first condenser 33, the second condenser 131 and the third condenser 132 is determined based on the boiling point of methanol (64.7℃). When the solvent is other substances, the cooling temperature can be set in steps according to the characteristics of the selected solvent.

[0062] In some embodiments of this application, the solvent recovery unit 3 provided in this application further includes a first discharge pump 4, which is disposed at the bottom of the recovery tower 31 and communicates with the recovery tower 31, for discharging waste liquid in the recovery tower 31. The first discharge pump 4 and the recovery tower 31 can be connected by a connecting pipe so that the waste liquid in the recovery tower 31 can be discharged through the pipeline under the action of the first discharge pump 4.

[0063] In this way, the waste liquid in the recovery tower 31 can be discharged by the first discharge pump 4, avoiding the liquid level in the recovery tower 31 from being too high and ensuring the normal operation of the solvent recovery unit 3.

[0064] In some embodiments of this application, the solvent recovery unit 3 provided in this application further includes a gas detection device 5, disposed on the outer wall of the solvent return pipe 35, for detecting the concentration of solvent gas. The gas detection device 5 may include a detection sensor, a sampling module, a signal processing module, a communication module, and a power supply. The presence of solvent gas in the environment surrounding the solvent return pipe 35 is obtained through the detection sensor and the sampling module, the signal from the sensor is processed by the signal processing module, and the signal is recorded or remotely monitored through the communication module. The power supply provides power to each module.

[0065] This allows for timely detection of leaks in the solvent return pipe 35, reducing safety hazards. When the gas generated by the solvent is a harmful or dangerous gas, leaks can be detected promptly, thus reducing the probability of accidents. For example, a methanol gas leak can be detected immediately and appropriate emergency measures can be taken.

[0066] In some embodiments of this application, such as Figure 2As shown, the solvent recovery unit 3 provided in this application also includes a flow retarder 6, which is disposed inside the solvent return pipe 35. The flow retarder 6 is plate-shaped, and the outline shape of the flow retarder 6 is the same as the radial cross-sectional shape of the solvent return pipe 35. The flow retarder 6 is provided with through holes 60 evenly distributed on it.

[0067] In this way, by setting a flow buffer 6 inside the solvent return pipe 35, the flow rate of the gas inside the solvent return pipe 35 can be appropriately reduced, avoiding the generation of static electricity due to excessive flow rate, thereby preventing accidents caused by static electricity.

[0068] In some embodiments of this application, see Figure 3 The aforementioned through hole 60 is a tapered hole, and along the direction from the end of the solvent reflux pipe 35 near the first reflux tank 34 to the end of the solvent reflux pipe 35 near the pre-distillation unit 1, the diameter of the tapered hole gradually increases, that is, along the gas flow direction, the diameter of the through hole 60 gradually increases.

[0069] This reduces the pressure drop caused by the flow buffer 6, avoids excessive loss of gas kinetic energy, and ensures that the gas can flow smoothly into the pre-distillation unit 1 along the solvent return pipe 35 to participate in the cycle.

[0070] In the embodiments of this application, the aforementioned through hole 60 can also be a stepped hole, see reference. Figure 4 Along the direction of gas flow, the through-hole 60 may include a first orifice section 601 and a second orifice section 602, wherein the diameter of the first orifice section 601 is smaller than the diameter of the second orifice section 602, and the first orifice section 601 is located closer to the windward side. In this way, the diameter of the through-hole 60 increases sequentially. The small orifice of the first orifice section 601 initially constrains the airflow and reduces its kinetic energy, and then the second orifice section 602 stabilizes and diffuses the airflow, reducing back pressure.

[0071] In some embodiments of this application, a heat insulation layer 350 is provided on the outer peripheral surface of the solvent reflux pipe 35. For example, a closed-cell flexible rubber or plastic material can be provided on the outside of the solvent reflux pipe 35 to insulate the solvent reflux pipe 35 and prevent methanol from condensing inside the solvent reflux pipe 35.

[0072] In this way, by setting an insulation layer 350 on the outer periphery of the solvent return pipe 35, methanol condensation due to temperature drop can be avoided during the methanol transportation process.

[0073] In some embodiments of this application, a drain valve 351 is also provided on the solvent reflux pipe 35.

[0074] In this way, the drain valve 351 can be opened periodically to drain the liquid accumulated in the solvent return pipe 35, ensuring unobstructed flow in the pipeline and preventing corrosion.

[0075] In some embodiments of this application, see Figure 5 The solvent reflux pipe 35 includes a first pipe section 3501 and a second pipe section 3502. The first pipe section 3501 has a first end 35011 and a second end 35012, and the second pipe section 3502 has a third end 35021 and a fourth end 35022. The first end 35011 is connected to the first gas outlet 342 of the first reflux tank 34, the second end 35012 is connected to the third end 35021, and the fourth end 35022 is connected to the pre-distillation unit 1. The horizontal height of the first end 35011 is less than the horizontal height of the second end 35012, and the horizontal height of the third end 35021 is greater than the horizontal height of the fourth end 35022.

[0076] In this way, the first section 3501 of the solvent reflux pipe 35 is inclined and extends in a gradually rising direction in the gas flow direction, which reduces the resistance to gas flow. The second section 3502 is inclined and extends in a gradually decreasing direction in the gas flow direction. In the event of gas condensation and droplet formation, the droplets formed in the first section 3501 can flow back to the first reflux tank 34 under the action of gravity, and the droplets formed in the second section 3502 can flow into the pipeline of the pre-distillation unit 1 under the action of gravity, thereby preventing condensate from accumulating in the pipeline.

[0077] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0078] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A solvent recovery system, characterized in that, The solvent recovery system includes: A pre-distillation unit is used to distill the solvent, and the pre-distillation unit emits purge gas during the distillation process; The water washing tower is equipped with a vent gas inlet, and the pre-distillation unit is connected to the water washing tower through the vent gas inlet; Solvent recovery unit, comprising: The recovery tower is provided with a first liquid inlet, and the water washing tower is connected to the recovery tower through the first liquid inlet; The first reboiler is located at the bottom of the recovery tower and is connected to the recovery tower; The first condenser is connected to the top of the recovery tower; The first reflux tank is provided with a first air inlet and a first air outlet. The first condenser is connected to the first reflux tank through the first air inlet. The first reflux tank is also provided with a first drain outlet. The recovery tower is connected to the first reflux tank through the first drain outlet. The solvent reflux pipe is connected at one end to the first gas outlet and at the other end to the pre-distillation unit.

2. The solvent recovery system according to claim 1, characterized in that, The pre-distillation unit includes: A pre-distillation column for containing the solvent; The second condenser is connected to the pre-distillation column and is used to cool the gas discharged from the pre-distillation column; A third condenser is connected to the second condenser and is also connected to the water washing tower through the vent inlet. The third condenser is used to cool the gas discharged from the second condenser.

3. The solvent recovery system according to claim 2, characterized in that, The cooling temperature of the second condenser is greater than or equal to 50°C and less than or equal to 70°C; The cooling temperature of the third condenser is greater than or equal to 40°C and less than or equal to 50°C.

4. The solvent recovery system according to any one of claims 1-3, characterized in that, The cooling temperature of the first condenser is greater than or equal to 70°C and less than or equal to 80°C.

5. The solvent recovery system according to any one of claims 1-3, characterized in that, The solvent recovery unit further includes: The first discharge pump is located at the bottom of the recovery tower and is connected to the recovery tower, and is used to pump out the waste liquid in the recovery tower.

6. The solvent recovery system according to any one of claims 1-3, characterized in that, The solvent recovery unit further includes: A gas detection device is installed on the outer wall of the solvent reflux pipe to detect the concentration of solvent gas.

7. The solvent recovery system according to any one of claims 1-3, characterized in that, The solvent recovery unit further includes: A flow-retarding element is disposed inside the solvent reflux pipe. The flow-retarding element is plate-shaped, and its outline shape is the same as the radial cross-sectional shape of the solvent reflux pipe. The flow-retarding element is uniformly provided with through holes.

8. The solvent recovery system according to claim 7, characterized in that, The through hole is a tapered hole, and it points towards the end of the solvent reflux pipe near the first reflux tank, and towards the end of the solvent reflux pipe near the pre-distillation unit. The diameter of the tapered hole gradually increases.

9. The solvent recovery system according to any one of claims 1-3, characterized in that, The solvent reflux pipe is provided with a heat insulation layer on its outer circumference.

10. The solvent recovery system according to any one of claims 1-3, characterized in that, The solvent reflux pipe is also equipped with a drain valve; and / or, The solvent reflux pipe includes a first pipe section and a second pipe section, wherein the first pipe section has a first end and a second end, the second pipe section has a third end and a fourth end, the first end is connected to the first gas outlet, the second end is connected to the third end, and the fourth end is connected to the pre-distillation unit. The horizontal height of the first end is less than that of the second end, and the horizontal height of the third end is greater than that of the fourth end.

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