Hydroxypropyl methylcellulose mixed solvent recycling method, device and application

Abstract

The invention discloses a method for recycling a hydroxypropyl methylcellulose mixed solvent. The method comprises the following steps: S1, preparing a high-ionic-strength solution; s2, injecting the high-ionic-strength solution into a solvent separator; s3, the hydroxypropyl methylcellulose mixed solvent is introduced into the bottom of the high-ionic-strength solution through a feeding pipe, and substance transfer exchange occurs on a water-oil two-phase interface; and S4, after an organic solvent layer is formed in the solvent separator, collecting the organic solvent overflowing from the solvent separator. A plurality of water outlet holes are formed in a water outlet structure at the tail end of the feeding pipe. According to the method for recycling the hydroxypropyl methylcellulose mixed solvent, the high-ionic-strength solution is used for separating the hydroxypropyl methylcellulose mixed solvent, so that the layering time of the hydroxypropyl methylcellulose mixed solvent can be remarkably shortened, and the working efficiency of solvent recycling is improved. The invention further discloses a hydroxypropyl methylcellulose mixed solvent recycling device and application.

Description

Technical Field

[0001] The invention belongs to the technical field of slurry production of hypromellose and environmentally friendly solvent treatment, and in particular, relates to a method and device for recycling a hypromellose mixed solvent. Background Art

[0002] The production process of Hydroxypropyl Methylcellulose (HPMC) mainly includes the slurry method and the gas phase method. The existing technology mainly adopts the slurry method, and its process includes impregnating refined cotton or wood pulp with liquid caustic soda, squeezing out excess alkali liquid to obtain alkali cellulose, then adding solvent and etherifying agent, and carrying out etherification reaction at a certain temperature and pressure, and finally obtaining the finished product through neutralization washing, drying, crushing and other steps. Among them, the solvent is mostly a mixed solvent such as toluene and isopropanol, the solvent dosage is large, the purity requirement is high, and the impurity and moisture content requirements are low, so it needs to be recycled.

[0003] The basic process of existing solvent recovery is as follows: after the etherification reaction of HPMC, the materials in the reactor are transferred to the desolventizing reactor, the pH is adjusted, and then steam is introduced into the desolventizing reactor for solvent recovery. The recovered mixed solvent (toluene and isopropanol) is separated by a gas-liquid separator, collected by a condenser, and then enters a stratification tank for static stratification for more than 24 hours. The upper layer liquid enters a storage tank for inspection and standby use.

[0004] Chinese patent application number 202410833949.3 discloses a solvent recovery system, including a reaction chamber, a filter, a condenser and a water ring vacuum pump. The reaction chamber is hollow inside, and a compartment that can be filled with a medium is arranged at the bottom, and a heating pipe is arranged in the compartment. The reaction chamber, the filter, the condenser and the water ring vacuum pump are connected in sequence through pipelines, and a first pneumatic valve and a second start-up valve are respectively arranged on the pipeline connecting the filter and the condenser and the pipeline connecting the condenser and the water ring vacuum pump. The first pneumatic valve and the second start-up valve are controlled to open by a solenoid valve at the same time, and the solution in the reaction chamber is heated by the compartment. The heating temperature can be stabilized through the conduction of the medium. The solenoid valve is used to simultaneously control the synchronous start and stop of the pneumatic valves at the inlet and outlet of the water ring vacuum pump and the condenser. The oil and water in the compressed air are separated by an oil-water separator to improve the quality of the compressed air. By arranging a vacuum unloading valve, when the pneumatic valve closes the pipeline, overpressure protection is provided to maintain the stability of the system.

[0005] In summary, in the prior art, the method for recovering solvent has the following disadvantages: 1. The solvent has a high water content and a high impurity content that is easy to accumulate. After repeated use, the quality of the solvent decreases and cannot meet the production requirements of hydroxypropyl methylcellulose. A new solvent needs to be replaced.

[0006] 2. The solvent recovery process requires a long period of static stratification (usually more than 24 hours), which is slow, time-consuming, and inefficient, affecting production capacity. It also requires a large number of transfer equipment, increasing safety risks.

[0007] 3. The lower layer liquid contains a large amount of isopropanol, which causes great waste and high processing cost.

[0008] 4. The solvent and lower liquid need to be recovered in a distillation tower for the second time, which consumes a lot of energy, is costly, and causes a large loss of solvent.

[0009] Provided are a method and device for recycling a mixed solvent of hypromellose, in particular, how to improve the efficiency of solvent recovery work. Summary of the invention

[0010] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention provides a method for recycling a mixed solvent of hypromellose, the purpose of which is to improve the efficiency of solvent recovery.

[0011] In order to achieve the above object, the technical solution adopted by the present invention is: a method for recycling a mixed solvent of hypromellose, comprising the steps of: S1. Prepare a high ionic strength solution; S2, injecting the high ionic strength solution into a solvent separator; S3, passing the hydroxypropyl methylcellulose mixed solvent to be treated into the bottom of the high ionic strength solution through a feed pipe, so that material transfer and exchange occurs at the water-oil two-phase interface; S4, after an organic solvent layer is formed in the solvent separator, collecting the organic solvent overflowing from the solvent separator; Wherein, the water outlet structure at the end of the feed pipe is provided with a plurality of water outlet holes, and the hydroxypropyl methylcellulose mixed solvent discharged from the water outlet holes enters into the high ionic strength solution.

[0012] In step S1, the high ionic strength solution is one or a mixture of two or more of sodium chloride, sodium sulfate, and potassium chloride, and the mass concentration of the high ionic strength solution is not less than 15%.

[0013] The high ionic strength solution is a mixed solution of sodium chloride and sodium sulfate, wherein the concentration of sodium chloride is 10% to 25%, and the concentration of sodium sulfate is 15% to 20%.

[0014] In the step S2, the high ionic strength solution is injected into the solvent separator, and the liquid level is more than 1 / 3 of the total height of the solvent separator.

[0015] In the step S3, the flow rate of the hydroxypropyl methylcellulose mixed solvent when passing into the bottom of the high ionic strength solution is 20-50 mL / min, the temperature is 25-50° C., and the pressure is normal pressure.

[0016] The shape of the terminal water outlet structure of the feed pipe is a straight tube, a bell-mouth shape, a disc shape or a ring shape, and the water outlet hole is arranged on the bottom surface and / or the side surface of the terminal water outlet structure.

[0017] The step S4 further comprises: introducing the overflowed organic solvent into a next solvent separator for secondary separation, wherein the solvent separator is injected with the high ionic strength solution.

[0018] The method for recycling the mixed solvent of hypromellose further comprises the steps of: S5. adjusting the solubility of the high ionic strength solution in the solvent separator.

[0019] Another object of the present invention is to provide a device for recycling a mixed solvent of hypromellose, comprising a solvent separator and a feed pipe, wherein the solvent separator is configured to accommodate a high ionic strength solution and a mixed solvent of hypromellose, and the feed pipe is configured to pass the mixed solvent of hypromellose into the bottom of the high ionic strength solution; a water outlet structure at the end of the feed pipe is provided with a plurality of water outlet holes.

[0020] The shape of the terminal water outlet structure of the feed pipe is a straight tube, a bell-mouth shape, a disc shape or a ring shape, and the water outlet hole is arranged on the bottom surface and / or the side surface of the terminal water outlet structure.

[0021] The aperture of the water outlet is 0.5-2 mm.

[0022] The distance between two adjacent water outlet holes is 5-10 mm.

[0023] The height-to-diameter ratio of the solvent separator is 3:1-5:1.

[0024] The solvent separator comprises an upper body and a lower body connected to each other, wherein the upper body is cylindrical and the lower body is conical, and a first sampling port and a second sampling port are arranged on the upper body, and the height of the first sampling port is greater than that of the second sampling port.

[0025] An overflow port is arranged on the upper body, and the organic solvent formed in the upper layer of the solvent separator overflows through the overflow port.

[0026] The lower body is provided with a salt water inlet and a salt water outlet, and the high ionic strength solution enters the lower body through the salt water inlet.

[0027] The brine inlet and the brine outlet are connected to a brine recovery tank through pipelines.

[0028] Another object of the present invention is to provide a method for recycling a mixed solvent of hypromellose or an application of a mixed solvent recycling device of hypromellose in the slurry production of hypromellose.

[0029] The method for recycling a mixed solvent of hypromellose can significantly shorten the stratification time of the mixed solvent of hypromellose by using a high ionic strength solution to separate the mixed solvent of hypromellose, improve the efficiency of solvent recovery, reduce the water and impurity content in the mixed solvent of hypromellose, improve the recovery rate and purity of the solvent, reduce energy consumption and processing costs, reduce safety risks, and has strong operability for industrial implementation. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] This specification includes the following drawings, which show the following contents: Figure 1 It is a schematic flow diagram of the method for recycling the mixed solvent of hypromellose of the present invention; Figure 2 It is a structural schematic diagram of a device for recycling a mixed solvent of hypromellose according to the present invention; Figure 3a It is a structural diagram of a feed pipe with a straight pipe-shaped water outlet structure at the end; Figure 3b It is a schematic diagram of the arrangement of the water outlet holes of a feed pipe whose terminal water outlet structure is a straight tube; Figure 4a It is a structural diagram of a feed pipe with a bell-shaped water outlet structure at the end; Figure 4b It is a schematic diagram of the arrangement of the water outlet holes of a feed pipe whose end water outlet structure is a bell-shaped one; Figure 5a It is a structural diagram of a feed pipe with a spiral water outlet structure at the end; Figure 5b It is a schematic diagram of the arrangement of the water outlet holes of a feed pipe with a spiral water outlet structure at the end; Figure 6a It is a structural diagram of a feed pipe with a ring-shaped end water outlet structure; Figure 6b It is a schematic diagram of the arrangement of the water outlet holes of a feed pipe with a ring-shaped water outlet structure at the end; The markings in the figure are: 1. upper body; 2. lower body; 3. main body; 4. end water outlet structure; 5. first sampling port; 6. second sampling port; 7. second-stage solvent separator; 8. overflow pipe; 9. salt water layer; 10. organic solvent layer; 11. water outlet; 12. connecting pipe. DETAILED DESCRIPTION

[0031] The specific implementation methods of the present invention are further explained in detail below by describing the embodiments with reference to the accompanying drawings, with the aim of helping those skilled in the art to have a more complete, accurate and in-depth understanding of the concept and technical solution of the present invention and facilitating its implementation.

[0032] It should be noted that, in the following embodiments, the “first” and “second” mentioned do not represent an absolute distinction in structure and / or function, nor do they represent a sequential order of execution, but are merely for the convenience of description.

[0033] First, as Figure 2 As shown, the present invention provides a device for recycling a mixed solvent of hypromellose, comprising a solvent separator and a feed pipe, wherein the solvent separator is configured to contain a high ionic strength solution and a mixed solvent of hypromellose, and the feed pipe is configured to pass the mixed solvent of hypromellose into the bottom of the high ionic strength solution; a water outlet structure at the end of the feed pipe is provided with a plurality of water outlet holes.

[0034] Specifically, the hydroxypropyl methylcellulose mixed solvent is a mixed solvent used in the production of hydroxypropyl methylcellulose, which is a mixed solvent of toluene and isopropanol. The high ionic strength solution is a mixture of one or more of sodium chloride, sodium sulfate, and potassium chloride. The high ionic strength solution can be a high-concentration aqueous solution or saturated solution prepared using one or more salts including but not limited to sodium chloride, sodium sulfate, potassium chloride, etc., and the salt mass concentration of the high ionic strength solution is not less than 15%.

[0035] During operation, a high ionic strength solution is first injected into the solvent separator, and then the HPMC mixed solvent to be treated is passed into the bottom of the high ionic strength solution through the feed pipe, and material transfer and exchange occurs at the water-oil two-phase interface. After the HPMC mixed solvent is passed into the bottom of the high ionic strength solution through the feed pipe, due to the density difference between the HPMC mixed solvent and the high ionic strength solution, the HPMC mixed solvent will move upward rapidly because its density is lower than that of the high ionic strength solution. During the upward movement of the HPMC mixed solvent, the HPMC mixed solvent and the high ionic strength solution are in contact, and material transfer and exchange occurs at the interface. The highly polar substances (such as water, methanol, etc.) in the HPMC mixed solvent enter the high ionic strength solution. The solubility of these substances in the high ionic strength solution is relatively high, so they can be effectively "removed" from the solvent, thereby achieving the effect of impurity removal. At the same time, due to the high concentration of the high ionic strength solution, the high concentration environment of the high ionic strength solution produces a salting-out effect on the isopropanol in the solvent, so the solubility of isopropanol in the high ionic strength solution is reduced, making it easier to separate from the solvent. This effect not only helps to quickly separate, but also reduces the loss of isopropanol in the high ionic strength solution, and improves the separation efficiency. With the continuous rise of the solvent and the progress of material exchange, a sufficient amount of organic solvent gradually accumulates in the upper layer, and an organic solvent layer and a brine layer are formed in the solvent separator, and the brine layer is located below the organic solvent layer. When the organic solvent in the upper layer reaches a certain amount, it flows out from the overflow port of the solvent separator. These outflowing organic solvents can be treated in two ways: one is to directly enter the production cycle for continued use, so that resources can be recycled; the other is to be introduced into the next separator for a deeper secondary separation to further purify or remove other impurities. This process takes advantage of the difference in physical and chemical properties between the solvent and the brine to achieve efficient material separation and purification. It can not only improve production efficiency, but also reduce production costs.

[0036] Moreover, the water outlet structure at the end of the feed pipe is densely covered with multiple water outlet holes, and the HPMC mixed solvent discharged from each water outlet hole enters the high ionic strength solution. The design of the fine water outlet holes can make the HPMC mixed solvent form finer droplets or streams when flowing out, thereby increasing the contact area between the HPMC mixed solvent and the high ionic strength solution. A larger contact area usually means more opportunities for interaction. In two-phase separation, increasing the contact area can directly improve the separation efficiency.

[0037] like Figure 2As shown, the solvent separator includes an upper body and a lower body connected to each other, and an overflow port, a first sampling port and a second sampling port are arranged on the upper body, the height of the first sampling port is greater than the height of the second sampling port, and the height of the overflow port is greater than the height of the first sampling port. The first sampling port is located in the organic solvent layer, and the second sampling port is located in the salt water layer. Valves are arranged at the first sampling port and the second sampling port. By sampling at the first sampling port, the organic solvent component of the organic solvent layer can be monitored; by sampling at the second sampling port, the salt water concentration of the salt water layer can be monitored.

[0038] like Figure 2 As shown, an overflow port is arranged on the upper body, and the organic solvent formed in the upper layer of the solvent separator overflows through the overflow port. The overflow port is connected to an overflow pipe, and the overflow pipe is used to connect to the inlet end of the feed pipe of the second-stage hydroxypropyl methylcellulose mixed solvent recovery and utilization device.

[0039] like Figure 2 As shown, the lower body is provided with a brine inlet and a brine outlet, and the high ionic strength solution enters the lower body through the brine inlet. The brine inlet and the brine outlet are located at the lower end of the lower body, and a bottom valve is provided at the brine outlet. The brine inlet and the brine outlet are connected to the brine recovery tank through a pipeline for the concentration and recycling of low-concentration brine.

[0040] like Figure 2 As shown, the upper body is cylindrical, the lower body is conical, the upper body and the lower body are coaxially arranged, the upper end of the lower body is a large diameter end, the lower end of the lower body is a large diameter end, the diameter of the large diameter end is larger than the diameter of the small diameter end, the upper end of the lower body is connected to the lower end of the upper body and the diameters of the two are the same. The feed pipe is vertically inserted into the solvent separator, and the lower end of the feed pipe is a terminal water outlet structure, which can extend into the lower body.

[0041] As a preferred method, the height-to-diameter ratio (ratio between height and diameter) of the solvent separator is 3:1~5:1. A deeper salt water layer can increase the contact between the solvent and the salt water, increase the mass transfer time, and enhance the separation effect. However, if the height is too large, the effect is no longer obvious, and the processing cost increases. Practice has proved that a height-to-diameter ratio of 3:1~5:1 is more reasonable.

[0042] As a preference, the terminal water outlet structure of the feed pipe has a variety of shapes, such as a straight tube, a trumpet, a disc or an annular shape, and the water outlet hole can be arranged on the bottom surface and / or the side surface of the terminal water outlet structure, and the bottom surface of the terminal water outlet structure refers to the lowest position on the terminal water outlet structure. The aperture of the water outlet hole arranged in the terminal water outlet structure of the feed pipe is 0.5~2mm, and the aperture of the water outlet hole can be 0.7mm, 0.9mm, 1.2mm, 1.4mm, 1.6mm or 1.8mm. The spacing between two adjacent water outlet holes is 5~10mm, and the spacing between two adjacent water outlet holes can be 6mm, 7mm, 8mm or 9mm. The purpose of setting different shapes and openings at the end is to increase the contact between the treatment solvent and the brine, facilitate the interphase transfer of impurities, and enhance the treatment effect. The shape of the feed pipe end, the position of the opening, the aperture size, and the hole density can be selected according to the size of the equipment, the processing requirements, the processing capacity, etc.

[0043] Second, as Figure 1 As shown, the present invention provides a method for recycling a mixed solvent of hypromellose, which adopts the mixed solvent recycling device of hypromellose of the above structure and comprises the following steps: S1. Prepare a high ionic strength solution; S2, injecting the high ionic strength solution into the solvent separator; S3, passing the hydroxypropyl methylcellulose mixed solvent to be treated into the bottom of the high ionic strength solution through a feed pipe, so that material transfer and exchange occurs at the water-oil two-phase interface; S4, after an organic solvent layer is formed in the solvent separator, collecting the organic solvent overflowing from the solvent separator; The water outlet structure at the end of the feed pipe is provided with a plurality of water outlet holes, and the hydroxypropyl methylcellulose mixed solvent discharged from the water outlet holes enters into the high ionic strength solution.

[0044] In the above step S1, the high ionic strength solution is a mixture of one or more of sodium chloride, sodium sulfate, and potassium chloride. When preparing the high ionic strength solution, first weigh the solid salt (such as sodium chloride, sodium sulfate, potassium chloride, etc.), add it to water, and then stir and dissolve it until the solid salt is completely dissolved, and finally filter out the insoluble matter to form a high ionic strength solution for standby use. The salt mass concentration of the prepared high ionic strength solution is not less than 15%.

[0045] In the above step S2, the high ionic strength solution is injected into the solvent separator, and the liquid level is more than 1 / 3 of the total height of the solvent separator.

[0046] In the above step S3, the HPMC mixed solvent to be treated is introduced into the bottom of the high ionic strength solution through the feed pipe, and the solvent flows out / sprays out from the water outlet at the bottom of the feed pipe. The HPMC mixed solvent contacts the high ionic strength solution, and material transfer and exchange occurs at the water-oil two-phase interface.

[0047] In the above step S3, the temperature of the hydroxypropyl methylcellulose mixed solvent when it is passed into the bottom of the high ionic strength solution is 25-50°C, and the pressure is normal pressure. Exemplarily, the flow rate of the hydroxypropyl methylcellulose mixed solvent when it is passed into the bottom of the high ionic strength solution can be 25mL / min, 30mL / min, 35mL / min, 40mL / min or 45mL / min, and the temperature can be 30°C, 35°C, 40°C or 45°C. The temperature of the processing solvent should not be too high. When the temperature is high, the vapor pressure is large, waste gas may be generated, and a gas recovery or treatment device needs to be added.

[0048] In the above step S4, after the HPMC mixed solvent is continuously introduced, an organic solvent layer and a brine layer are gradually formed in the solvent separator, and the brine layer is located below the organic solvent layer. Then, the valve at the overflow port is opened in time to collect the organic solvent overflowing from the overflow port.

[0049] The above step S4 also includes: introducing the overflowed organic solvent into the next solvent separator for secondary separation, and the solvent separator is also injected with a high ionic strength solution to further purify or remove other impurities.

[0050] like Figure 1 As shown, the method for recycling the mixed solvent of hydroxypropyl methylcellulose of the present invention further comprises the following steps: S5. Adjust the solubility of the high ionic strength solution in the solvent separator.

[0051] In the above step S5, the brine concentration of the brine layer is monitored by sampling at the second sampling port. When it is monitored that the brine concentration of the brine layer does not meet the stratification requirements, the brine concentration of the brine layer needs to be adjusted by opening the bottom valve at the brine outlet to discharge part of the low-concentration brine in the solvent separator, and then opening the valve at the brine inlet to add new high ionic strength solution to the solvent separator to maintain the separation efficiency.

[0052] In a third aspect, the present invention also provides a method for recycling a mixed solvent of hypromellose or an application of a mixed solvent recycling device for hypromellose in a slurry process for producing hypromellose, which is used for the rapid recovery and purification of a mixed solvent of toluene and isopropanol. Embodiment 1

[0053] In this embodiment, the high ionic strength solution is a sodium chloride solution with a concentration of 25%. The mixed solvent for producing hydroxypropyl methylcellulose is recovered by layering the 25% sodium chloride solution.

[0054] Take 500ml of 25% sodium chloride solution and add Figure 2 In the solvent separator shown, the total volume of the solvent separator is about 1000ml. 25% sodium chloride solution is injected into the solvent separator, and the liquid level is about 20cm. Hydroxypropyl methylcellulose mixed solvent is passed into the bottom of the sodium chloride solution through a feed pipe. The flow rate of the hydropropyl methylcellulose mixed solvent is controlled so that a total amount of 1000ml of the hydropropyl methylcellulose mixed solvent is injected into the solvent separator, and the injection time lasts about 30min. The hydropropyl methylcellulose mixed solvent is quickly layered in the solvent separator, and both phases are clear and transparent, with a clear interface. The upper layer is the organic solvent layer, and the lower layer is the brine layer. Part of the organic solvent flows out from the overflow port of the solvent separator, and the flowing organic solvent is collected. After the experiment is completed, the liquid level of the brine layer rises by about 2cm, and then the organic solvent layer is sampled, and finally the content is determined by gas chromatography, and the results are shown in Table 1. Embodiment 2

[0055] In this embodiment, the high ionic strength solution is a sodium sulfate solution, and the concentration of the sodium sulfate solution is 20%. The mixed solvent for the production of hydroxypropyl methylcellulose is recovered by layering the 20% sodium sulfate solution.

[0056] Take 500ml of 20% sodium sulfate solution and add Figure 2 In the solvent separator shown, the total volume of the solvent separator is about 1000ml. 20% sodium sulfate solution is injected into the solvent separator, and the liquid level is about 20cm. Hydroxypropyl methylcellulose mixed solvent is passed into the bottom of the sodium sulfate solution through a feed pipe. The flow rate of the hydropropyl methylcellulose mixed solvent is controlled so that a total amount of 1000ml of the hydropropyl methylcellulose mixed solvent is injected into the solvent separator, and the injection time lasts about 30min. The hydropropyl methylcellulose mixed solvent is quickly layered in the solvent separator, and both phases are clear and transparent, with a clear interface. The upper layer is the organic solvent layer, and the lower layer is the brine layer. Part of the organic solvent flows out from the overflow port of the solvent separator, and the flowing organic solvent is collected. After the experiment is completed, the liquid level of the brine layer rises slightly, and then the organic solvent layer is sampled, and finally the content is determined by gas chromatography, and the results are shown in Table 1. Embodiment 3

[0057] In this embodiment, the high ionic strength solution is a mixture of a sodium chloride solution and a sodium sulfate solution, wherein the concentration of the sodium chloride solution is 10% and the concentration of the sodium sulfate solution is 15%. The mixed solvent for the production of hydroxypropyl methylcellulose is recovered by layering the 10% sodium chloride + 15% sodium sulfate mixed salt solution.

[0058] Take 5.0L of a high ionic strength solution made of 10% sodium chloride + 15% sodium sulfate solution and add Figure 2 In the solvent separator shown, the total volume of the solvent separator is about 10.0L. The high ionic strength solution is injected into the solvent separator, and the liquid level is about 35cm. The hydroxypropyl methylcellulose mixed solvent is passed into the bottom of the sodium sulfate solution through a feed pipe. The flow rate of the hydroxypropyl methylcellulose mixed solvent is controlled so that a total amount of 10L of hydroxypropyl methylcellulose mixed solvent is injected into the solvent separator, and the injection time lasts about 60min. The hydroxypropyl methylcellulose mixed solvent is quickly layered in the solvent separator, and both phases are clear and transparent, with a clear interface. The upper layer is the organic solvent layer, and the lower layer is the brine layer. Part of the organic solvent flows out from the overflow port of the solvent separator, and the outflowing organic solvent is collected. After the experiment is completed, the liquid level of the brine layer rises by about 1.5cm, and the organic solvent layer is sampled. Finally, the content is determined by gas chromatography, and the results are shown in Table 1. Comparative Example

[0059] The traditional treatment process of the mixed solvent of hydroxypropyl methylcellulose is as follows: after the etherification reaction of hydroxypropyl methylcellulose, the materials in the reactor are transferred to the desolventizing reactor, the pH is adjusted, and then steam is introduced into the desolventizing reactor for solvent recovery. The recovered mixed solvent (toluene and isopropanol) is separated by a gas-liquid separator, collected by a condenser, and then enters a stratification tank. After standing and stratifying for more than 24 hours, it can become clear, and the upper liquid enters a storage tank for inspection and standby. The upper liquid is sampled and the content is measured. The results are shown in Table 1.

[0060] Table 1 Solvent determination results

[0061] Compared with the traditional treatment process, the mixed solvent treated by the method for recycling the hydroxypropyl methylcellulose mixed solvent of the present invention has clear and transparent solvent, low water content, less loss of toluene and isopropanol, high treatment efficiency, low energy consumption and is green and environmentally friendly. Embodiment 4

[0062] In this embodiment, Figure 3a and Figure 3b The shape of the end water outlet structure of the feed pipe shown in the figure is a straight tube, and water outlet holes are arranged on the bottom and side surfaces of the end water outlet structure. The side surface of the end water outlet structure is a cylindrical surface, and the side surface of the end water outlet structure is coaxial with the solvent separator. The bottom surface of the end water outlet structure is located below the side surface, and the water outlets on the bottom surface and side surfaces of the end water outlet structure are evenly distributed. Embodiment 5

[0063] In this embodiment, Figure 4a and Figure 4bThe shape of the end water outlet structure of the feed pipe shown in the figure is a trumpet shape. The feed pipe includes a main body, and the end water outlet structure is arranged at the lower end of the main body. The main body is a cylindrical tube body with a hollow interior. The main body and the end water outlet structure are coaxially arranged. The upper end of the end water outlet structure is a small diameter end, and the lower end of the end water outlet structure is a large diameter end. The diameter of the large diameter end is larger than the diameter of the small diameter end. The diameter of the end water outlet structure gradually increases from the small diameter end to the large diameter end. The small diameter end of the end water outlet structure is fixedly connected to the lower end of the main body and the two have the same diameter. The water outlets on the bottom surface of the end water outlet structure are evenly distributed, and the bottom surface of the end water outlet structure is the end surface of the large diameter end. Embodiment 6

[0064] In this embodiment, Figure 5a and Figure 5b The shape of the end water outlet structure of the feed pipe shown in the figure is spiral, the feed pipe includes a main body, and the end water outlet structure is arranged at the lower end of the main body. The main body is a cylindrical tube body with a hollow interior, and the end water outlet structure is a spiral tube body with a hollow interior. The spiral tube body presents a spiral structure, and the lower end of the main body is connected to the end water outlet structure at the center of the end water outlet structure. The water outlet arranged on the end water outlet structure is distributed along the spiral line of the spiral tube body, which means that the hydroxypropyl methylcellulose mixed solvent can flow out from multiple positions and at different angles, thereby achieving a wider and more uniform dispersion. Embodiment 7

[0065] In this embodiment, Figure 6a and Figure 6b The shape of the terminal water outlet structure of the feed pipe shown in the figure is annular, the feed pipe includes a main body and a connecting pipe, a plurality of connecting pipes are arranged at the lower end of the main body, the lower ends of all the connecting pipes are connected to the terminal water outlet structure, the main body is a cylindrical tube body with a hollow interior, all the connecting pipes are evenly distributed circumferentially with the axis of the main body as the center line, the terminal water outlet structure is a circular ring tube body with a hollow interior, the terminal water outlet structure and the main body are coaxially arranged, the diameter of the terminal water outlet structure is larger than the diameter of the main body, the hydroxypropyl methylcellulose mixed solvent entering the main body enters the terminal water outlet structure below through a plurality of connecting pipes, the bottom surface of the terminal water outlet structure is a circular ring plane, and a plurality of water outlets are sealed on the bottom surface of the terminal water outlet structure.

[0066] In the above-mentioned fourth to seventh embodiments, the different water outlet structures of the feed pipe respectively belong to different forms of fluid mixing methods, which can accelerate the solvent processing speed and have a significant effect on the rapid processing of mixed solvents.

[0067] The present invention is described above by way of example in conjunction with the accompanying drawings. Obviously, the specific implementation of the present invention is not limited to the above-mentioned methods. As long as various non-substantial improvements are made using the method concept and technical solution of the present invention; or the above concept and technical solution of the present invention are directly applied to other occasions without improvement, they are all within the protection scope of the present invention.

Claims

1. A method for recycling a mixed solvent of hypromellose, characterized in that: Includes steps: S1. Prepare a high ionic strength solution; S2, injecting the high ionic strength solution into a solvent separator; S3, passing the hydroxypropyl methylcellulose mixed solvent to be treated into the bottom of the high ionic strength solution through a feed pipe, so that material transfer and exchange occurs at the water-oil two-phase interface; S4, after an organic solvent layer is formed in the solvent separator, collecting the organic solvent overflowing from the solvent separator; Wherein, the water outlet structure at the end of the feed pipe is provided with a plurality of water outlet holes, and the hydroxypropyl methylcellulose mixed solvent discharged from the water outlet holes enters into the high ionic strength solution.

2. The method for recycling the mixed solvent of hypromellose according to claim 1, characterized in that: In step S1, the high ionic strength solution is one or a mixture of two or more of sodium chloride, sodium sulfate, and potassium chloride, and the mass concentration of the high ionic strength solution is not less than 15%.

3. The method for recycling the mixed solvent of hypromellose according to claim 1, characterized in that: The high ionic strength solution is a mixed solution of sodium chloride and sodium sulfate, wherein the concentration of sodium chloride is 10% to 25%, and the concentration of sodium sulfate is 15% to 20%.

4. The method for recycling a mixed solvent of hypromellose according to any one of claims 1 to 3, characterized in that: In the step S2, the high ionic strength solution is injected into the solvent separator, and the liquid level is more than 1 / 3 of the total height of the solvent separator.

5. The method for recycling a mixed solvent of hypromellose according to any one of claims 1 to 3, characterized in that: In the step S3, the flow rate of the hydroxypropyl methylcellulose mixed solvent when passing into the bottom of the high ionic strength solution is 20-50 mL / min, the temperature is 25-50° C., and the pressure is normal pressure.

6. The method for recycling a mixed solvent of hypromellose according to any one of claims 1 to 3, characterized in that: The shape of the terminal water outlet structure of the feed pipe is a straight tube, a bell-mouth shape, a disc shape or a ring shape, and the water outlet hole is arranged on the bottom surface and / or the side surface of the terminal water outlet structure.

7. The method for recycling a mixed solvent of hypromellose according to any one of claims 1 to 3, characterized in that: The step S4 further comprises: introducing the overflowed organic solvent into a next solvent separator for secondary separation, wherein the solvent separator is injected with the high ionic strength solution.

8. The method for recycling a mixed solvent of hypromellose according to any one of claims 1 to 3, characterized in that: Also includes the steps: S5. adjusting the solubility of the high ionic strength solution in the solvent separator.

9. A device for recycling a mixed solvent of hypromellose, characterized in that: It comprises a solvent separator and a feed pipe. The solvent separator is configured to contain a high ionic strength solution and a hydroxypropyl methylcellulose mixed solvent. The feed pipe is configured to pass the hydroxypropyl methylcellulose mixed solvent into the bottom of the high ionic strength solution. A water outlet structure at the end of the feed pipe is provided with a plurality of water outlet holes.

10. The device for recycling the mixed solvent of hypromellose according to claim 9, characterized in that: The shape of the terminal water outlet structure of the feed pipe is a straight tube, a bell-mouth shape, a disc shape or a ring shape, and the water outlet hole is arranged on the bottom surface and / or the side surface of the terminal water outlet structure.

11. The device for recycling the mixed solvent of hypromellose according to claim 9, characterized in that: The aperture of the water outlet is 0.5-2 mm.

12. The device for recycling the mixed solvent of hypromellose according to claim 11, characterized in that: The distance between two adjacent water outlet holes is 5-10 mm.

13. The device for recycling the mixed solvent of hypromellose according to any one of claims 9 to 12, characterized in that: The height-to-diameter ratio of the solvent separator is 3:1-5:

1.

14. The device for recycling the mixed solvent of hypromellose according to any one of claims 9 to 12, characterized in that: The solvent separator comprises an upper body and a lower body connected to each other, wherein the upper body is cylindrical and the lower body is conical, and a first sampling port and a second sampling port are arranged on the upper body, and the height of the first sampling port is greater than that of the second sampling port.

15. The device for recycling the mixed solvent of hypromellose according to claim 14, characterized in that: An overflow port is arranged on the upper body, and the organic solvent formed in the upper layer of the solvent separator overflows through the overflow port.

16. The device for recycling the mixed solvent of hypromellose according to claim 14, characterized in that: The lower body is provided with a salt water inlet and a salt water outlet, and the high ionic strength solution enters the lower body through the salt water inlet.

17. The device for recycling the mixed solvent of hypromellose according to claim 16, characterized in that: The brine inlet and the brine outlet are connected to a brine recovery tank through pipelines.

18. Application of the method for recycling the mixed solvent of hypromellose according to claim 1 in the slurry process production of hypromellose.

19. Use of the device for recycling the mixed solvent of hypromellose according to claim 9 in the slurry process production of hypromellose.

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