Dehydration process and system for organic solvents

Abstract

The present application relates to the technical field of dehydration, in particular to a dehydration method and system of organic solvent. The method comprises the following steps: feeding the mixture in the raw material tank to a first membrane separation unit for the first dehydration by pressurized heating, wherein the mixture in the raw material tank comprises high water content organic solvent fed by external raw material pipeline and first separated material of a second membrane separation unit; feeding the second separated material of the first membrane separation unit to the second membrane separation unit for the second dehydration; and condensing and recycling the second separated material of the second membrane separation unit to obtain low water content organic solvent. The present application is provided with two-stage membrane separation units to achieve deep dehydration, and the first separated material of the second membrane separation unit is returned to the raw material tank. The first separated material of the second membrane separation unit is mixed with the high water content organic solvent and then enters the membrane separation unit for dehydration, which improves the membrane dehydration efficiency, improves the organic matter recovery rate of the system, reduces the sewage treatment load, and reduces the operation cost.

Description

Technical Field

[0001] This invention relates to the field of dehydration technology, and in particular to a method and system for dehydrating organic solvents. Background Technology

[0002] Current optimizations of membrane separation technology, particularly in membrane materials, modules, and processes, primarily focus on the feedstock side. Less attention is paid to organic solvent losses on the water permeate side, especially during deep dehydration. For high-value organic solvents, further improvements in their recovery rates are needed. Furthermore, the higher organic matter content on the water permeate side increases the wastewater treatment load, leading to higher operating costs. Summary of the Invention

[0003] To address the shortcomings of existing technologies, this invention proposes a method and system for dehydrating organic solvents, aiming to solve the problem of low organic solvent recovery rates.

[0004] The technical solution proposed in this invention is:

[0005] A method for dehydrating an organic solvent, the method comprising:

[0006] The mixture in the raw material storage tank is pressurized and heated and then transported to the primary membrane separation unit for the first dehydration. The mixture in the raw material storage tank includes a high-water-content organic solvent transported by an external raw material pipeline and the first separated product from the secondary membrane separation unit.

[0007] The second separated product from the primary membrane separation unit is then transported to the secondary membrane separation unit for a second dehydration.

[0008] The second separated product from the secondary membrane separation unit is condensed and recovered to obtain a low-water-content organic solvent.

[0009] Further, the step of pressurizing and heating the mixture in the raw material storage tank and conveying it to the primary membrane separation unit for the first dehydration includes:

[0010] The mixture from the raw material storage tank is pressurized by a pressurizing pump, preheated by a preheater, and heated to the operating temperature by a heater before entering the primary membrane separation unit for the first dehydration.

[0011] Further, the step of condensing and recovering the second separated product from the secondary membrane separation unit to obtain a low-aqueous organic solvent includes:

[0012] The second separated product from the secondary membrane separation unit is condensed sequentially through a back pressure valve, the hot fluid pipeline of the preheater, and the product condenser to obtain a low-water-content organic solvent. The mixture in the raw material storage tank passes through a cold fluid pipeline of the preheater.

[0013] Further, after the step of conveying the second separated product from the primary membrane separation unit to the secondary membrane separation unit for a second dehydration, the process includes:

[0014] The first separated product from the secondary membrane separation unit is returned to the raw material storage tank.

[0015] Further, the step of refluxing the first separated product from the secondary membrane separation unit back to the raw material storage tank includes:

[0016] The first separated product from the secondary membrane separation unit is condensed sequentially by a secondary vacuum condenser and then returned to the raw material storage tank by a permeate circulation pump.

[0017] Further, after the steps of condensing the first separated product from the secondary membrane separation unit sequentially through a secondary vacuum condenser and recirculating the permeate back to the raw material storage tank by a permeate circulation pump, the process includes:

[0018] The uncondensed material in the secondary vacuum condenser is transported to the exhaust gas treatment system pipeline via the secondary vacuum unit.

[0019] Further, after the step of conveying the second separated product from the primary membrane separation unit to the secondary membrane separation unit for a second dehydration, the process includes:

[0020] The first separated product from the primary membrane separation unit is condensed sequentially by a primary vacuum condenser and then discharged into the wastewater treatment system.

[0021] Further, after the step of condensing the first separated product from the primary membrane separation unit sequentially through a primary vacuum condenser and then discharging it into the wastewater treatment system, the process includes:

[0022] The uncondensed material in the primary vacuum condenser is transported to the exhaust gas treatment system pipeline via the primary vacuum unit.

[0023] Further, the step of refluxing the first separated product from the secondary membrane separation unit back to the raw material storage tank includes:

[0024] Control the second switching valve to open;

[0025] The first separated product from the secondary membrane separation unit is sequentially condensed for the first time by a secondary vacuum condenser, then condensed for the second time by a secondary vacuum unit and a tail cooler, and finally returned to the raw material storage tank by a permeate circulation pump.

[0026] Further, the step of refluxing the first separated product from the secondary membrane separation unit back to the raw material storage tank includes:

[0027] Control the opening of the first and second switching valves;

[0028] The first separated product from the secondary membrane separation unit is condensed sequentially by a secondary vacuum condenser and the permeate is returned to the raw material storage tank by a permeate circulation pump.

[0029] The uncondensed material in the secondary vacuum condenser is condensed sequentially by the secondary vacuum unit and the tail cooler, and the permeate is returned to the raw material storage tank by the permeate circulation pump.

[0030] The present invention also provides a dehydration system for organic solvents, comprising:

[0031] The first dehydration module is used to pressurize and heat the mixture in the raw material storage tank and transport it to the primary membrane separation unit for the first dehydration. The mixture in the raw material storage tank includes a high-water-content organic solvent transported by an external raw material pipeline and the first separated product of the secondary membrane separation unit.

[0032] The second dehydration module is used to transport the second separated product from the first-stage membrane separation unit to the second-stage membrane separation unit for a second dehydration.

[0033] The recovery module is used to condense and recover the second separated product from the secondary membrane separation unit to obtain a low-water-content organic solvent.

[0034] According to the above technical solution, the beneficial effects of the present invention are as follows: The present invention is provided with a two-stage membrane separation unit. The first-stage membrane separation unit can complete the first dewatering. The second-stage membrane separation unit further dewaters the second separated product from the first-stage membrane separation unit, that is, performs a second dewatering to achieve deep dewatering. The first separated product from the second-stage membrane separation unit is returned to the raw material storage tank. The first separated product from the second-stage membrane separation unit is mixed with a high water content organic solvent and then enters the membrane separation unit for dewatering, thereby improving the organic matter recovery rate of the system, reducing the wastewater treatment load, and reducing operating costs. Attached Figure Description

[0035] Figure 1 This is a flowchart of the dehydration method for organic solvents provided in the embodiments of the present invention;

[0036] Figure 2 This is a functional block diagram of the organic solvent dehydration system provided in the embodiments of the present invention;

[0037] Figure 3 This is a schematic block diagram of the structure of the organic solvent dehydration system provided in the embodiments of the present invention;

[0038] Figure 4 This is a schematic block diagram of the structure of an organic solvent dehydration system provided by another embodiment of the present invention. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0040] like Figure 1 , Figure 3 and Figure 4 As shown in the figure, an embodiment of the present invention proposes a method for dehydrating organic solvents, the method comprising the following steps:

[0041] Step S101: The mixture in the raw material storage tank is pressurized and heated and then transported to the primary membrane separation unit for the first dehydration. The mixture in the raw material storage tank includes a high-water-content organic solvent transported by an external raw material pipeline and the first separated product of the secondary membrane separation unit.

[0042] The raw material storage tank 21 is provided with a raw material inlet for connection to an external raw material pipeline, a permeate recovery port for connection to the outlet of the permeate circulation pump 63, and a raw material outlet for connection to the pressure pump 22.

[0043] The primary membrane separation unit 31 is composed of one or more membrane modules connected in series. The material inlet of the first membrane module is connected to the outlet of the heater 24, and the material outlet of the last membrane module is connected to the inlet of the secondary membrane separation unit. Each membrane module is provided with a vacuum pipeline on one side and is connected to the inlet of the primary vacuum condenser 41.

[0044] Step S102: The second separated product from the primary membrane separation unit is transported to the secondary membrane separation unit for a second dehydration.

[0045] The secondary membrane separation unit 32 is composed of one or more membrane modules connected in series. The material inlet of the first membrane module is connected to the outlet of the primary membrane separation unit 31, and the material outlet of the last membrane module is connected to the inlet of the back pressure valve 51. Each membrane module is provided with a vacuum pipeline on one side and is connected to the inlet of the secondary vacuum condenser 61.

[0046] Step S103: The second separated product from the secondary membrane separation unit is condensed and recovered to obtain a low-water-content organic solvent.

[0047] This invention features a two-stage membrane separation unit. The first-stage membrane separation unit 31 performs the first dehydration, while the second-stage membrane separation unit 32 further dehydrates the second product separated from the first-stage membrane separation unit 31, i.e., performs a second dehydration to achieve deep dehydration. The first product separated from the second-stage membrane separation unit 32 is returned to the raw material storage tank 21. The first product separated from the second-stage membrane separation unit 32 is mixed with a high-water-content organic solvent and then enters the membrane separation unit for dehydration, thereby improving the organic matter recovery rate of the system, reducing the wastewater treatment load, and lowering operating costs.

[0048] In this embodiment, the first separated product is the permeate, and the second separated product is the residue.

[0049] In this embodiment, the step of pressurizing and heating the mixture from the raw material storage tank and then conveying it to the primary membrane separation unit for the first dehydration includes:

[0050] The mixture from the raw material storage tank is pressurized by a pressurizing pump, preheated by a preheater, and heated to the operating temperature by a heater before entering the primary membrane separation unit for the first dehydration.

[0051] The pressurization pump 22 is used to provide energy to the raw materials and transport the materials. Its inlet and outlet are connected to the raw material storage tank 21 and the inlet of the preheater 23, respectively.

[0052] The preheater 23 is used to recover part of the heat and reduce costs. The cold material is the mixture in the raw material storage tank, and the hot material is the second separated product of the secondary membrane separation unit 32.

[0053] The heater 23 can be a liquid heater or a vaporizer, used to further heat the mixture in the raw material storage tank 21 to the operating temperature. The mixture in the raw material storage tank 21 can be in a vapor phase or a liquid phase in the primary and secondary membrane separation units. If it is in a liquid phase, the heater is a liquid heater; if it is in a vapor phase, the heater is a vaporizer.

[0054] In this embodiment, the step of condensing and recovering the second separated product from the secondary membrane separation unit to obtain a low-aqueous organic solvent includes:

[0055] The second separated product from the secondary membrane separation unit is condensed sequentially through a back pressure valve, the hot fluid pipeline of the preheater, and the product condenser to obtain a low-water-content organic solvent. The mixture in the raw material storage tank passes through a cold fluid pipeline of the preheater.

[0056] The back pressure valve 51 is used to assist in applying material pressure to the raw material side of the primary membrane separation unit and the secondary membrane separation unit. The back pressure valve 51 has an inlet for connecting to the material outlet of the secondary membrane separation unit 32, and an outlet for connecting to the material inlet of the preheater heat 23.

[0057] The product condenser 52 is used for product cooling. The hot material is a low-moisture product that has been cooled by waste heat recovery, and the cold material is circulating water.

[0058] In this embodiment, after the step of conveying the second separated product from the primary membrane separation unit to the secondary membrane separation unit for a second dehydration, the following steps are included:

[0059] The first separated product from the secondary membrane separation unit is returned to the raw material storage tank.

[0060] In this embodiment, the step of refluxing the first separated product from the secondary membrane separation unit back to the raw material storage tank includes:

[0061] The first separated product from the secondary membrane separation unit is condensed sequentially by a secondary vacuum condenser and then returned to the raw material storage tank by a permeate circulation pump.

[0062] The secondary vacuum condenser 61 is used to condense the first separated product of the secondary membrane separation unit 32. The secondary vacuum condenser 61 is provided with a hot material inlet for connection to the vacuum outlet collection pipe of the secondary membrane separation unit 32. The condensed material is connected to the organic matter content condensate pipeline on the secondary water permeate side and then discharged to the inlet of the permeate circulation pump 63. The uncondensed material is connected to the inlet of the secondary vacuum unit.

[0063] The permeate circulation pump 63 is used to recover the first separated product from the secondary membrane separation unit 32. The permeate circulation pump 63 has an inlet for connecting to the condensate outlet of the secondary vacuum condenser 61. The permeate circulation pump 63 has an outlet for connecting to the inlet of the raw material storage tank 21.

[0064] In this embodiment, after the steps of condensing the first separated product from the secondary membrane separation unit sequentially through a secondary vacuum condenser and recirculating the permeate back to the raw material storage tank by a permeate circulation pump, the process includes:

[0065] The uncondensed material in the secondary vacuum condenser is transported to the exhaust gas treatment system pipeline via the secondary vacuum unit.

[0066] The secondary vacuum unit 66 is used to impart vacuum to the water permeation side of the secondary membrane separation unit and to collect uncondensed material. The secondary vacuum unit 66 is provided with a material inlet for connecting to the outlet of the secondary vacuum condenser 61, and a material outlet for connecting to the exhaust gas treatment system pipeline.

[0067] In this embodiment, after the step of conveying the second separated product from the primary membrane separation unit to the secondary membrane separation unit for a second dehydration, the following steps are included:

[0068] The first separated product from the primary membrane separation unit is condensed sequentially by a primary vacuum condenser and then discharged into the wastewater treatment system.

[0069] The primary vacuum condenser 41 is used to condense the first separated product of the primary membrane separation unit 31. It is equipped with a hot material inlet for connecting to the vacuum outlet collection pipe of the primary membrane separation unit 31. The condensed material is connected to the high water content condensate pipeline on the primary water permeation side and then discharged to the sewage treatment system. The uncondensed material is connected to the inlet of the primary vacuum unit 42.

[0070] In this embodiment, after the step of condensing the first separated product from the primary membrane separation unit sequentially through a primary vacuum condenser and then discharging it into the wastewater treatment system, the following steps are included:

[0071] The uncondensed material in the primary vacuum condenser is transported to the exhaust gas treatment system pipeline via the primary vacuum unit.

[0072] The primary vacuum unit 42 is used to impart vacuum to the water permeation side of the primary membrane separation unit and to collect uncondensed material. The primary vacuum unit 42 is provided with a material inlet for connecting to the outlet of the primary vacuum condenser 41, and a material outlet for connecting to the exhaust gas treatment system pipeline.

[0073] like Figure 4 As shown, in some embodiments, the step of refluxing the first separated product from the secondary membrane separation unit back to the raw material storage tank includes:

[0074] Control the second switching valve to open;

[0075] The first separated product from the secondary membrane separation unit is sequentially condensed for the first time by a secondary vacuum condenser, then condensed for the second time by a secondary vacuum unit and a tail cooler, and finally returned to the raw material storage tank by a permeate circulation pump.

[0076] In this embodiment of the invention, it is mainly applied to low-boiling-point organic solvents, that is, organic solvents with a boiling point below 100°C. The second switching valve 65 is opened and the first switching valve 62 is closed. The first separated product of the secondary membrane separation unit 32 is sequentially condensed for the first time by the secondary vacuum condenser 61, the secondary vacuum unit 66, the tail cooler 64 for the second time, and the permeate circulation pump 63. Then, it is transported to the raw material storage tank 21 by the outlet of the permeate circulation pump 63.

[0077] In some embodiments, the step of refluxing the first separated product from the secondary membrane separation unit back to the feed storage tank includes:

[0078] Control the opening of the first and second switching valves;

[0079] The first separated product from the secondary membrane separation unit is condensed sequentially by a secondary vacuum condenser and the permeate is returned to the raw material storage tank by a permeate circulation pump.

[0080] The uncondensed material in the secondary vacuum condenser is condensed sequentially by the secondary vacuum unit and the tail cooler, and the permeate is returned to the raw material storage tank by the permeate circulation pump.

[0081] In this embodiment of the invention, it is mainly applied to high-boiling-point organic solvents, i.e., organic solvents with a boiling point higher than 100°C, to achieve two-stage recovery of high-water-content organic solvents. The second switch valve 65 is opened, and the first switch valve 62 is opened, so that the first separated material from the secondary membrane separation unit 32 is condensed sequentially through the secondary vacuum condenser 61 and enters the inlet of the permeate circulation pump 63; the uncondensed material in the secondary vacuum condenser 61 is condensed sequentially through the secondary vacuum unit 66 and the tail cooler 64 and enters the inlet of the permeate circulation pump 63; then it is transported to the raw material storage tank 21 from the outlet of the permeate circulation pump 63.

[0082] Example 1

[0083] An example is taken as an annual production of 40,000 tons of anhydrous ethanol (product water content less than 0.02 wt%) with 5.00 wt% water content.

[0084] After the ethanol feedstock with a water content of 5.00 wt% is mixed evenly with the high ethanol content condensate on the secondary water permeation side, it is pressurized by a pressurizing pump, preheated to 85°C by a preheater, and heated to the operating temperature of 120°C by a heater. Then, it enters the primary membrane separation unit in liquid state for the first dehydration to 0.50 wt%. Preferably, the water content of the material at the outlet of the primary membrane separation unit is 0.453 wt%. The water permeation side of the primary membrane separation unit is provided with a vacuum pressure of 3000 Pa·A by a primary vacuum unit.

[0085] The second separated product from the primary membrane separation unit is transported to the secondary membrane separation unit for a second dehydration to 0.02 wt%. The first separated product from the primary membrane separation unit is then condensed in a primary vacuum condenser and discharged into the wastewater treatment system.

[0086] The first separated material from the secondary membrane separation unit is condensed sequentially by a secondary vacuum condenser and the permeate is returned to the raw material storage tank by a permeate circulation pump. The uncondensed material in the secondary vacuum condenser is transported to the tail gas treatment system pipeline by a secondary vacuum unit. Preferably, the water permeate side of the secondary membrane separation unit is provided with a vacuum pressure of 300 Pa·A by the secondary vacuum unit.

[0087] The second separated product from the secondary membrane separation unit is sequentially condensed through a back pressure valve, the hot fluid pipeline of the preheater, and the product condenser to obtain a low-water-content organic solvent. Preferably, the back pressure valve is used to assist in applying material pressure to the raw material side of the primary and secondary membrane separation units, and the pressure is maintained at 0.5 MPa.G.

[0088] The overall organic matter (ethanol) loss only occurs during the production from the primary membrane dehydration permeate side, with a total production of 271.003 kg / h, of which ethanol content is 2.83 wt%. The loss is 7.68 kg / h per hour, resulting in an annual loss of approximately 61.36 tons of ethanol. Compared to the conventional process in Comparative Example 1 where secondary permeate was not recovered, this reduces ethanol loss by approximately 59.024 tons per year.

[0089] Example 2

[0090] An example is taken to illustrate the production of 10,000 tons / year of electronic-grade NMP (product water content less than 0.005wt%) using N-methylpyrrolidone NMP solution with 15.00wt% water content.

[0091] After uniformly mixing the NMP feedstock with a water content of 15.00 wt% with the high NMP content condensate from the secondary water permeation side, the mixture is sequentially pressurized by a booster pump, preheated to 80°C by a preheater, and heated to 120°C by a heater. After reaching the operating temperature, the mixture enters the primary membrane separation unit in liquid phase for the first dehydration, which is reduced to 0.50 wt%. Preferably, the water content of the material at the outlet of the primary membrane separation unit is 0.5 wt%. The water permeation side of the primary membrane separation unit is provided with a vacuum pressure of 2000 Pa·A by a primary vacuum unit.

[0092] The second separated product from the primary membrane separation unit is transported to the secondary membrane separation unit for a second dehydration to 0.02 wt%. The first separated product from the primary membrane separation unit is then condensed in a primary vacuum condenser and discharged into the wastewater treatment system.

[0093] The first and second switching valves are opened; the first separated material from the secondary membrane separation unit is condensed sequentially through a secondary vacuum condenser and the permeate is returned to the raw material storage tank by a permeate circulation pump; the uncondensed material in the secondary vacuum condenser is condensed sequentially through a secondary vacuum unit and a tail cooler and the permeate is returned to the raw material storage tank by a permeate circulation pump. Preferably, the water permeate side of the secondary membrane separation unit is provided with a vacuum pressure of 300 Pa·A by a secondary vacuum unit.

[0094] The second separated product from the secondary membrane separation unit is sequentially condensed through a back pressure valve, the hot fluid pipeline of the preheater, and the product condenser to obtain a low-water-content organic solvent. Preferably, the back pressure valve is used to assist in applying material pressure to the raw material side of the primary and secondary membrane separation units, and the pressure is maintained at 0.35 MPa.G.

[0095] The overall process organic matter (NMP) loss only occurs during the production from the primary membrane dehydration permeate side, with a total production of 223.152 kg / h, of which the NMP content is 2.669 wt%. The loss is 5.956 kg / h per hour, resulting in an annual loss of approximately 47.648 tons of NMP. Compared to the conventional process in Comparative Example 2, where no secondary permeate recovery was performed, this reduces NMP loss by approximately 68.688 tons annually.

[0096] Comparative Example 1

[0097] An example is taken as an annual production of 40,000 tons of anhydrous ethanol (product water content less than 0.02 wt%) with 5.00 wt% water content.

[0098] The ethanol feedstock with a water content of 5.00 wt% is pressurized by a pressurizing pump, preheated to 85°C by a preheater, and heated to 120°C by a heater before entering the first-stage membrane separation unit in liquid state for the first dehydration, which is reduced to 0.50 wt%. Preferably, the water content of the material at the outlet of the first-stage membrane separation unit is 0.15 to 0.75 wt%. The water permeate side of the first-stage membrane separation unit is provided with a vacuum pressure of 1000 to 5000 Pa·A by a first-stage vacuum unit.

[0099] The second separated product from the primary membrane separation unit is transported to the secondary membrane separation unit for a second dehydration to 0.02 wt%. The first separated product from the primary membrane separation unit is then condensed in a primary vacuum condenser and discharged into the wastewater treatment system.

[0100] The first separated material from the secondary membrane separation unit is condensed sequentially by a secondary vacuum condenser and then pumped into the wastewater treatment system via a permeate circulation pump. The uncondensed material in the secondary vacuum condenser is transported to the tail gas treatment system pipeline via a secondary vacuum unit. Preferably, the water permeate side of the secondary membrane separation unit is provided with a vacuum pressure of 100-500 Pa·A by the secondary vacuum unit.

[0101] The second separated product from the secondary membrane separation unit is sequentially condensed through a back pressure valve, the hot fluid pipeline of the preheater, and the product condenser to obtain a low-water-content organic solvent. Preferably, the back pressure valve is used to assist in applying material pressure to the raw material side of the primary and secondary membrane separation units, and the pressure is maintained at 0.2 to 0.6 MPa.G.

[0102] The overall process organic matter (ethanol) loss occurs in the production from the primary membrane dehydration permeate side and the secondary membrane permeate side. The primary permeate side produced a total of 271.003 kg / h of material, of which the ethanol content was 2.83 wt%. This represents a loss of 7.68 kg / h per hour, or approximately 61.36 tons of ethanol per year. The secondary permeate side produced a total of 22.584 kg / h of material, of which the ethanol content was 32.267 wt%. This represents a loss of 7.378 kg / h per hour, or approximately 59.024 tons of ethanol per year.

[0103] Comparative Example 2

[0104] An example is taken to illustrate the production of 10,000 tons / year of electronic-grade NMP (product water content less than 0.005wt%) using N-methylpyrrolidone NMP solution with 15.00wt% water content.

[0105] The NMP feedstock with a water content of 15.00 wt% is pressurized by a pressurizing pump, preheated to 80°C by a preheater, and heated to 120°C by a heater before entering the first-stage membrane separation unit in liquid state for the first dehydration, which is reduced to 0.50 wt%. Preferably, the water content of the material at the outlet of the first-stage membrane separation unit is 0.15 to 0.75 wt%. The water permeate side of the first-stage membrane separation unit is provided with a vacuum pressure of 1000 to 5000 Pa·A by a first-stage vacuum unit.

[0106] The second separated product from the primary membrane separation unit is transported to the secondary membrane separation unit for a second dehydration to 0.02 wt%. The first separated product from the primary membrane separation unit is then condensed in a primary vacuum condenser and discharged into the wastewater treatment system.

[0107] The first separated material from the secondary membrane separation unit is condensed sequentially by a secondary vacuum condenser and then pumped into the wastewater treatment system via a permeate circulation pump. The uncondensed material in the secondary vacuum condenser is transported to the tail gas treatment system pipeline via a secondary vacuum unit. Preferably, the water permeate side of the secondary membrane separation unit is provided with a vacuum pressure of 100-500 Pa·A by the secondary vacuum unit.

[0108] The second separated product from the secondary membrane separation unit is condensed sequentially through a back pressure valve, the hot fluid pipeline of the preheater, and the product condenser to obtain a low-water-content organic solvent. Preferably, the back pressure valve is used to assist in applying material pressure to the raw material side of the primary and secondary membrane separation units, and the pressure is maintained at 0.1 to 0.4 MPa.G.

[0109] The overall process organic matter (NMP) loss occurs in the production from the primary and secondary membrane dehydration permeate sides. The primary permeate side produced 223.152 kg / h of material, containing 2.669 wt% NMP. The hourly loss is 5.956 kg / h, resulting in an annual loss of approximately 47.648 tons of NMP. The secondary permeate side produced 13.617 kg / h of material, containing 63.047 wt% NMP. The hourly loss is 8.586 kg / h, resulting in an annual loss of approximately 68.688 tons of NMP. The total NMP loss for the entire process is approximately 116.336 tons per year.

[0110] Comparative Example 3

[0111] An example is taken to illustrate the production of 10,000 tons / year of electronic-grade NMP (product water content less than 0.005wt%) using N-methylpyrrolidone NMP solution with 15.00wt% water content.

[0112] After uniformly mixing the NMP feedstock with a water content of 15.00 wt% with the high NMP content condensate from the secondary water permeation side, the mixture is sequentially pressurized by a booster pump, preheated to 80°C by a preheater, and heated to 120°C by a heater. After reaching the operating temperature, the mixture enters the primary membrane separation unit in liquid phase for the first dehydration, which is reduced to 0.50 wt%. Preferably, the water content of the material at the outlet of the primary membrane separation unit is 0.5 wt%. The water permeation side of the primary membrane separation unit is provided with a vacuum pressure of 2000 Pa·A by a primary vacuum unit.

[0113] The second separated product from the primary membrane separation unit is transported to the secondary membrane separation unit for a second dehydration to 0.02 wt%. The first separated product from the primary membrane separation unit is then condensed in a primary vacuum condenser and discharged into the wastewater treatment system.

[0114] The first switch valve is opened and the second switch valve is closed; the first separated product of the secondary membrane separation unit is condensed sequentially through a secondary vacuum condenser, and the permeate is returned to the raw material storage tank by a permeate circulation pump; preferably, the water permeate side of the secondary membrane separation unit is provided with a vacuum pressure of 300 Pa·A by a secondary vacuum unit;

[0115] The second separated product from the secondary membrane separation unit is sequentially condensed through a back pressure valve, the hot fluid pipeline of the preheater, and the product condenser to obtain a low-water-content organic solvent. Preferably, the back pressure valve is used to assist in applying material pressure to the raw material side of the primary and secondary membrane separation units, and the pressure is maintained at 0.35 MPa.G.

[0116] The overall process organic matter (NMP) loss only occurs in the production and tail condensate production on the primary membrane dehydration permeate side. A total of 223.152 kg / h of material was produced on the primary permeate side, containing 2.669 wt% NMP. The secondary tail condensate production was 3.978 kg / h, containing 6.0% NMP. The production loss is 6.194 kg / h per hour, resulting in an annual loss of approximately 49.552 tons of NMP.

[0117] Comparative Example 4

[0118] An example is taken to illustrate the production of 10,000 tons / year of electronic-grade NMP (product water content less than 0.005wt%) using N-methylpyrrolidone NMP solution with 15.00wt% water content.

[0119] After uniformly mixing the NMP feedstock with a water content of 15.00 wt% with the high NMP content condensate from the secondary water permeation side, the mixture is sequentially pressurized by a booster pump, preheated to 80°C by a preheater, and heated to 120°C by a heater. After reaching the operating temperature, the mixture enters the primary membrane separation unit in liquid phase for the first dehydration, which is reduced to 0.50 wt%. Preferably, the water content of the material at the outlet of the primary membrane separation unit is 0.5 wt%. The water permeation side of the primary membrane separation unit is provided with a vacuum pressure of 2000 Pa·A by a primary vacuum unit.

[0120] The second separated product from the primary membrane separation unit is transported to the secondary membrane separation unit for a second dehydration to 0.02 wt%. The first separated product from the primary membrane separation unit is then condensed in a primary vacuum condenser and discharged into the wastewater treatment system.

[0121] The first switch valve is closed and the second switch valve is opened; the uncondensed material in the secondary vacuum condenser is condensed sequentially by the secondary vacuum unit and the tail cooler, and the permeate is returned to the raw material storage tank by the permeate circulation pump. Preferably, the water permeate side of the secondary membrane separation unit is provided with a vacuum pressure of 300 Pa·A by the secondary vacuum unit.

[0122] The second separated product from the secondary membrane separation unit is sequentially condensed through a back pressure valve, the hot fluid pipeline of the preheater, and the product condenser to obtain a low-water-content organic solvent. Preferably, the back pressure valve is used to assist in applying material pressure to the raw material side of the primary and secondary membrane separation units, and the pressure is maintained at 0.35 MPa.G.

[0123] The overall process organic matter (NMP) loss only occurs in the production from the primary membrane dehydration permeate side and the secondary permeate condensate production. A total of 223.152 kg / h of material was produced from the primary permeate side, containing 2.669 wt% NMP. The secondary permeate condensate production was 9.729 kg / h, containing 86.4% NMP. The production loss is 8.4058 kg / h per hour, resulting in an annual loss of approximately 114.89 tons of NMP.

[0124] like Figure 2 As shown, the present invention also provides an organic solvent dehydration system 1, comprising:

[0125] The first dehydration module 11 is used to pressurize and heat the mixture in the raw material storage tank and transport it to the primary membrane separation unit for the first dehydration. The mixture in the raw material storage tank includes a high-water-content organic solvent transported by an external raw material pipeline and the first separated product of the secondary membrane separation unit.

[0126] The second dehydration module 12 is used to transport the second separated product from the first-stage membrane separation unit to the second-stage membrane separation unit for a second dehydration.

[0127] The recovery module 13 is used to condense and recover the second separated product from the secondary membrane separation unit to obtain a low-water-content organic solvent.

[0128] This invention features a two-stage membrane separation unit. The first-stage membrane separation unit completes the initial dehydration, while the second-stage membrane separation unit further dehydrates the second product separated from the first-stage unit, achieving deep dehydration. The first product separated from the second-stage unit is then returned to the raw material storage tank. The first product separated from the first-stage membrane separation unit is mixed with a high-water-content organic solvent before entering the membrane separation unit for further dehydration, thereby improving the system's organic matter recovery rate, reducing the wastewater treatment load, and lowering operating costs.

[0129] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for dehydrating an organic solvent, characterized in that, The method includes: The mixture in the raw material storage tank is pressurized and heated and then transported to the primary membrane separation unit for the first dehydration. The mixture in the raw material storage tank includes a high-water-content organic solvent transported by an external raw material pipeline and the first separated product from the secondary membrane separation unit. The second separated product from the primary membrane separation unit is then transported to the secondary membrane separation unit for a second dehydration. The second separated product from the secondary membrane separation unit is condensed and recovered to obtain a low-water-content organic solvent.

2. The method for dehydrating organic solvents according to claim 1, characterized in that, The step of pressurizing and heating the mixture from the raw material storage tank and then conveying it to the primary membrane separation unit for the first dehydration includes: The mixture from the raw material storage tank is pressurized by a pressurizing pump, preheated by a preheater, and heated to the operating temperature by a heater before entering the primary membrane separation unit for the first dehydration.

3. The method for dehydrating organic solvents according to claim 2, characterized in that, The step of condensing and recovering the second separated product from the secondary membrane separation unit to obtain a low-aqueous organic solvent includes: The second separated product from the secondary membrane separation unit is condensed sequentially through a back pressure valve, the hot fluid pipeline of the preheater, and the product condenser to obtain a low-water-content organic solvent. The mixture in the raw material storage tank passes through a cold fluid pipeline of the preheater.

4. The method for dehydrating organic solvents according to claim 1, characterized in that, After the step of conveying the second separated product from the primary membrane separation unit to the secondary membrane separation unit for a second dehydration, the process includes: The first separated product from the secondary membrane separation unit is condensed sequentially by a secondary vacuum condenser and then returned to the raw material storage tank by a permeate circulation pump.

5. The method for dehydrating organic solvents according to claim 4, characterized in that, After the steps of condensing the first separated product from the secondary membrane separation unit sequentially through a secondary vacuum condenser and returning the permeate to the raw material storage tank via a permeate circulation pump, the process includes: The uncondensed material in the secondary vacuum condenser is transported to the exhaust gas treatment system pipeline via the secondary vacuum unit.

6. The method for dehydrating organic solvents according to claim 1, characterized in that, After the step of conveying the second separated product from the primary membrane separation unit to the secondary membrane separation unit for a second dehydration, the process includes: The first separated product from the primary membrane separation unit is condensed sequentially by a primary vacuum condenser and then discharged into the wastewater treatment system.

7. The method for dehydrating organic solvents according to claim 6, characterized in that, After the step of condensing the first separated product from the primary membrane separation unit sequentially through a primary vacuum condenser and then discharging it into the wastewater treatment system, the following steps are included: The uncondensed material in the primary vacuum condenser is transported to the exhaust gas treatment system pipeline via the primary vacuum unit.

8. The method for dehydrating organic solvents according to claim 1, characterized in that, After the step of conveying the second separated product from the primary membrane separation unit to the secondary membrane separation unit for a second dehydration, the process includes: Control the second switching valve to open; The first separated product from the secondary membrane separation unit is sequentially condensed for the first time by a secondary vacuum condenser, then condensed for the second time by a secondary vacuum unit and a tail cooler, and finally returned to the raw material storage tank by a permeate circulation pump.

9. The method for dehydrating organic solvents according to claim 1, characterized in that, After the step of conveying the second separated product from the primary membrane separation unit to the secondary membrane separation unit for a second dehydration, the process includes: Control the opening of the first and second switching valves; The first separated product from the secondary membrane separation unit is condensed sequentially by a secondary vacuum condenser and the permeate is returned to the raw material storage tank by a permeate circulation pump. The uncondensed material in the secondary vacuum condenser is condensed sequentially by the secondary vacuum unit and the tail cooler, and the permeate is returned to the raw material storage tank by the permeate circulation pump.

10. A dehydration system for an organic solvent, characterized in that, include: The first dehydration module is used to pressurize and heat the mixture in the raw material storage tank and transport it to the primary membrane separation unit for the first dehydration. The mixture in the raw material storage tank includes a high-water-content organic solvent transported by an external raw material pipeline and the first separated product of the secondary membrane separation unit. The second dehydration module is used to transport the second separated product from the first-stage membrane separation unit to the second-stage membrane separation unit for a second dehydration. The recovery module is used to condense and recover the second separated product from the secondary membrane separation unit to obtain a low-water-content organic solvent.

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