A device and method for self-coupling hot water utilization of alcoholysis waste liquid for high-temperature wastewater recovery.

Abstract

This invention relates to a device and method for the self-coupling utilization of high-temperature wastewater and hot water from alcoholysis waste liquid. The device includes: a methanol purification tower, a catalytic decomposition tower, a flash tank, a first reboiler, a methyl acetate purification tower, a cooler, and a centrifugal pump. The bottom of the methanol purification tower is connected sequentially to the flash tank, the first reboiler, and the catalytic decomposition tower via pipelines. The catalytic decomposition tower is connected to the methanol purification tower via the methyl acetate purification tower. The flash tank is connected sequentially to the centrifugal pump, the cooler, and the methyl acetate purification tower via pipelines. The high-temperature wastewater from the bottom of the methanol purification tower enters the flash tank, forming flash vapor and flash tank drainage. The flash vapor exchanges heat with the material in the catalytic decomposition tower in the first reboiler, cooling it to form hot water. The hot water and flash tank drainage are combined, cooled by the cooler to obtain cooling water, which then enters the methyl acetate purification tower. This self-coupling achieves the upgrading of high-temperature wastewater, waste heat recovery, wastewater reuse, and energy saving.

Description

[0001] This application is a divisional application of the application entitled "A high-temperature hot water comprehensive utilization device for a polyvinyl alcohol waste liquid recovery system", which was filed on December 29, 2020, and the application number is 202011595789.1. Technical Field

[0002] This invention relates to the chemical industry, and in particular to a device and method for the self-coupling utilization of high-temperature wastewater and hot water from alcoholysis waste liquid. Background Technology

[0003] Distillation towers are common equipment in chemical plants. In the process of separating methanol and water, the methanol distillation tower is pressurized, and the methanol vapor is sent to other towers as a heat source. The high-temperature wastewater at the bottom is directly discharged into a ditch. This wastewater has high calorific value, low COD, and good water quality; direct discharge into the ditch results in energy waste, but it cannot be directly reused. An example is the methanol purification tower in the polyvinyl alcohol (PVA) recovery process.

[0004] In the existing recycling process, the polyvinyl alcohol alcoholysis waste liquid is sent to a methyl acetate coarse separation tower for coarse separation. The crude methyl acetate distillate from the methyl acetate coarse separation tower is sent to a methyl acetate purification tower for extraction and purification. The refined methyl acetate distillate from the methyl acetate purification tower is sent to a catalytic decomposition tower for catalytic hydrolysis to produce acetic acid and methanol. The methanol from the bottom of the methyl acetate coarse separation tower and the methanol-water solution from the bottom of the methyl acetate purification tower are sent to a methanol purification tower for methanol purification. The gaseous refined methanol distillate from the methanol purification tower is used to exchange heat with the reboiler of the methyl acetate coarse separation tower before being sent to the tank farm. The hot water from the bottom of the methanol purification tower is used to feed and exchange heat with the methyl acetate coarse separation tower before being sent to the wastewater treatment plant.

[0005] The above-mentioned equipment and processes have the following problems: 1. Currently, the high-temperature hot water (120-140℃) exiting the methanol purification tower has a high temperature and large flow rate. Due to the mixing of vapor and liquid, energy is not well utilized. Direct discharge into the sewer to the sewage treatment plant not only wastes energy but also increases the pressure on sewage treatment. The high temperature also kills some bacteria in the water treatment system, affecting the normal production of sewage treatment. 2. The alcoholysis mother liquor contains PVA powder, which easily causes clogging of the alcoholysis mother liquor pipeline and plate heat exchanger. The feed to the methyl acetate coarse fractionation tower is alcoholysis mother liquor, so the plates and outlet pipeline of the methyl acetate coarse fractionation tower are also prone to clogging. It is necessary to use a large amount of demineralized water for shutdown boiling and cleaning, which consumes a lot of energy, wastes energy, and increases the amount of sewage discharged. Summary of the Invention

[0006] The purpose of this invention is to provide a device and method for the self-coupling utilization of high-temperature wastewater and hot water from alcoholysis waste liquid.

[0007] To achieve the above-mentioned objectives, the present invention provides a self-coupling device for recovering high-temperature wastewater and hot water from alcoholysis waste liquid, comprising: a methanol purification tower, a catalytic decomposition tower, a flash tank, a first reboiler, a methyl acetate purification tower, a cooler, and a centrifugal pump.

[0008] The reboiler of the methanol purification tower is connected in sequence to the flash tank, the first reboiler, and the catalytic decomposition tower via pipelines; the catalytic decomposition tower is connected to the methanol purification tower via the methyl acetate purification tower.

[0009] The flash tank is connected in sequence to the centrifugal pump, the cooler, and the methyl acetate purification tower via pipelines;

[0010] The high-temperature wastewater from the bottom of the methanol purification tower enters the flash tank to form flash steam and flash tank drainage. The flash steam exchanges heat with the material in the catalytic decomposition tower in the first reboiler and is cooled to become hot water. The hot water and the flash tank drainage are combined, cooled by the cooler to obtain cooling water, and then enter the methyl acetate purification tower.

[0011] According to one aspect of the invention, it also includes a methyl acetate crude fractionation tower and a horizontal heat exchanger;

[0012] The methyl acetate crude fractionation tower is connected to the methanol purification tower, the methyl acetate purification tower, the cooler, and the horizontal heat exchanger, respectively.

[0013] The horizontal heat exchanger is connected to the flash tank, the methyl acetate crude separation tower, and the centrifugal pump, respectively. The horizontal heat exchanger is a shell-and-tube type horizontal heat exchanger.

[0014] The polyvinyl alcohol alcoholysis waste liquid enters the horizontal heat exchanger and exchanges heat with the hot water before entering the methyl acetate crude separation tower. The hot water is cooled down and then merged with the drainage from the flash tank.

[0015] According to one aspect of the present invention, the bottom of the methanol purification tower is connected to the inlet of the flash tank by a first pipeline;

[0016] The steam outlet of the flash tank is connected to the upper inlet of the first reboiler via a third pipeline;

[0017] The upper outlet of the first reboiler is connected to the lower part of the catalytic decomposition tower via a fourth pipeline;

[0018] The lower outlet of the first reboiler is connected to the first pipeline via a fifth pipeline; the fifth pipeline is equipped with a first drain pipe for discharging wastewater.

[0019] According to one aspect of the invention, a second reboiler is further provided in parallel with the first reboiler, the bottom of the catalytic decomposition tower is connected to the lower inlets of the first reboiler and the second reboiler respectively by a second pipeline; the upper inlet of the second reboiler is connected to a sixth pipeline for connecting to an external steam source; and the upper outlet of the second reboiler is connected to the lower part of the catalytic decomposition tower by a fourth pipeline.

[0020] According to one aspect of the present invention, the drain port of the flash tank is connected to a seventh pipeline and an eighth pipeline, and the flash tank is further provided with a liquid level control device for controlling the on / off state of the eighth pipeline.

[0021] According to one aspect of the present invention, the upper part of the methyl acetate purification tower is provided with a ninth pipeline for inputting external demineralized water, the top of which is provided with a tenth pipeline for connecting to a catalytic decomposition tower, and the bottom of the tower is provided with an eleventh pipeline connected to the methanol purification tower.

[0022] The top of the catalytic decomposition tower is equipped with a twelfth pipeline connected to the methyl acetate purification tower.

[0023] According to one aspect of the invention, the cooler is provided with a thirteenth pipe connected to the ninth pipe, and a fourteenth pipe connected to the outlet of the centrifugal pump.

[0024] The cooler is also equipped with a circulating water pipeline for connecting to external circulating water.

[0025] The centrifugal pump has a fifteenth pipeline at its inlet connected to the flash tank.

[0026] The first sewage pipe is connected to the fifteenth pipe through the sixteenth pipe.

[0027] According to one aspect of the present invention, the upper part of the methyl acetate crude fractionation tower is provided with a seventeenth pipeline for inputting external demineralized water, the top of which is provided with an eighteenth pipeline for connection to the methyl acetate purification tower, and the bottom of the tower is provided with a nineteenth pipeline connected to the eleventh pipeline.

[0028] According to one aspect of the present invention, the horizontal heat exchanger is provided with a twentieth pipeline for inputting alcoholysis waste liquid, a twenty-first pipeline for connecting to the middle part of the methyl acetate crude separation tower, and a twenty-second and twenty-third pipeline connected to the first drain pipe.

[0029] Control valves for controlling their on / off states are respectively installed on the 22nd and 23rd pipelines;

[0030] A 24th pipeline is connected between the 20th and 21st pipelines; a control valve for controlling its on / off state is installed on the 24th pipeline.

[0031] According to one aspect of the invention, the methyl acetate crude fractionation tower is further provided with a twenty-fifth pipeline for connecting the seventeenth pipeline and the thirteenth pipeline, and a twenty-sixth pipeline for connecting the nineteenth pipeline, the cooler and the centrifugal pump between the fourteenth pipeline;

[0032] The 26th pipeline is also provided with a 27th pipeline for connecting to the 20th pipeline; the 27th pipeline is provided with a control valve for controlling its on / off state.

[0033] According to one aspect of the invention, the outlet of the centrifugal pump includes: a fourteenth pipeline connected to the cooler, wherein the cooling water is connected via a thirteenth pipeline and a twenty-fifth pipeline to a ninth pipeline of demineralized water from the methyl acetate purification tower and a seventeenth pipeline of demineralized water from the methyl acetate crude separation tower, respectively; a twenty-sixth pipeline connected to the bottom of the methyl acetate crude separation tower; and a twenty-seventh pipeline connected to a twentyth pipeline for feeding the methyl acetate crude separation tower, for cleaning the twentyth pipeline.

[0034] According to one aspect of the present invention, a method for self-coupling utilization of high-temperature wastewater and hot water is also provided, applied to a high-temperature wastewater and hot water self-coupling utilization device as described in any of the above technical solutions, characterized in that it includes the following steps:

[0035] Step S1: The high-temperature wastewater from the methanol purification tower bottom is passed into the flash tank to form flash steam and flash tank drainage. The flash steam exchanges heat with the material of the catalytic decomposition tower in the first reboiler and is cooled to become hot water.

[0036] Step S2: The hot water obtained in step S1 is combined with the drainage from the flash tank, cooled by the cooler to obtain cooling water, which is then passed into the methyl acetate purification tower to replace the demineralized water for methyl acetate extraction and purification.

[0037] According to one aspect of the invention, it further includes:

[0038] Step S3: The hot water obtained in step S1 first enters a horizontal heat exchanger to exchange heat with the polyvinyl alcohol alcoholysis waste liquid from the feed of the methyl acetate crude fractionation tower. After cooling, the hot water obtained is then combined with the drainage from the flash tank.

[0039] According to one aspect of the invention, it further includes:

[0040] Step S4: The hot water obtained in step S3 is combined with the drainage from the flash tank and then enters a centrifugal pump, which divides it into three paths. The first path is sent to the cooler through the fourteenth pipeline for cooling and then to the methyl acetate purification tower and the methyl acetate coarse fractionation tower to replace the demineralized water. The second path is sent to the feed pipeline of the methyl acetate coarse fractionation tower through the twenty-seventh pipeline to replace the demineralized water used to clean the feed pipeline of the methyl acetate coarse fractionation tower. The third path is sent to the bottom of the methyl acetate coarse fractionation tower through the twenty-sixth pipeline to replace the demineralized water used to wash the tower plates.

[0041] According to one aspect of the present invention, the high-temperature wastewater steam and hot water are reused separately, reducing steam consumption and demineralized water consumption, reducing wastewater discharge, and reducing wastewater treatment pressure.

[0042] According to one aspect of the present invention, by setting up a flash tank, the high-temperature hot water (temperature 120-140℃) from the methanol purification tower bottom can enter the tank tangentially. Due to the effects of two-phase flow and eddy separation, after expansion within the tank, the pressure decreases, generating secondary flash steam (temperature 120-130℃). This secondary flash steam can then be introduced into a low-pressure steam pipe into the first reboiler to heat the material flowing through it. This allows the heat energy carried by the methanol purification tower bottom liquid to be reused (the temperature of the hot water after heat exchange is 90-100℃). This achieves the reuse of low-quality heat energy, effectively improving the energy utilization rate and reducing energy consumption of the present invention, thus saving production costs. With the above setup, approximately 1.32 tons of steam per ton of polyvinyl alcohol can be saved annually. If the annual production of polyvinyl alcohol is 10,000 tons, the direct economic benefit is approximately 790,000 yuan per year.

[0043] According to one aspect of the present invention, by setting a first drain pipe on the fifth pipeline, the water discharged from the methanol purification tower bottom and the first reboiler can be discharged. This is beneficial for the system to discharge water with more solid impurities after long-term operation, which is conducive to ensuring the long-term stable operation of the entire system.

[0044] According to one aspect of the present invention, by providing a second reboiler and a sixth pipeline for conveying external steam, it is possible to ensure that the second reboiler can supplement the heat energy when the first reboiler is unable to work or the heat supply is insufficient, thereby contributing to the stable operation of the present invention.

[0045] According to one aspect of the present invention, by providing multiple drain pipes on the flash tank, the flash tank can still be drained even if one drain pipe is blocked, which is beneficial for ensuring the long-term continuous operation of the flash tank. Furthermore, by using a liquid level control device to control one of the drain pipes, the draining of the flash tank of the present invention can be dynamically controlled, which is beneficial for improving the draining efficiency and the stable operation of the system.

[0046] According to one embodiment of the present invention, by adding a first reboiler, a flash tank, a centrifugal pump, and a cooler, the hot water (temperature 120-140℃) in the methanol purification tower bottom is cooled in two stages by the newly added first reboiler (heat exchanged, hot water temperature 90-100℃) and the cooler (heat exchanged, water temperature 30-40℃) before being sent to the methyl acetate purification tower for extraction water recycling. The hot water in the methanol purification tower bottom, after passing through the newly added first reboiler, can also use this portion of its heat energy as a heat source for the catalytic decomposition tower bottom. This not only reduces steam consumption in the catalytic decomposition tower but also saves demineralized water usage, improves water resource utilization, and reduces wastewater discharge. Through the above configuration, approximately 1.32 tons of steam per ton of polyvinyl alcohol (PVA) can be saved, approximately 3.64 tons of demineralized water per ton of PVA can be saved, and approximately 3.64 tons of wastewater discharge can be reduced. If the annual PVA production is 10,000 tons, the direct economic benefit exceeds RMB 1.045 million per year.

[0047] According to one embodiment of the present invention, by adding a flash tank, a reboiler (i.e., a first reboiler), a cooler, a horizontal heat exchanger, and a centrifugal pump, high-temperature hot water (temperature 120-140°C) first enters the flash tank. Flash steam (temperature 120-130°C) from the top of the flash tank enters the first reboiler for heat exchange. The hot water after heat exchange (temperature 90-100°C) is then fed into the horizontal heat exchanger from the bottom of the first reboiler, and then fed to the crude methyl acetate fraction via the horizontal heat exchanger. The feed to the tower is heated, and the cooled water (60-80℃) is combined with the hot water discharged from the bottom of the flash tank (90-100℃). This combined water is then pumped via a newly added centrifugal pump: one route is sent to the nineteenth pipeline of the methyl acetate coarse fractionation tower (connected by a pipeline), another route is sent to the twentieth feed pipeline of the methyl acetate coarse fractionation tower, and the third route is sent to the newly added cooler for further cooling. The cooled hot water is then returned to the methyl acetate coarse fractionation tower and the methyl acetate purification tower for reuse. This setup saves approximately 1.6 tons of steam per ton of polyvinyl alcohol (PVA), saves approximately 3.9 tons of demineralized water per ton of PVA, and reduces wastewater discharge by approximately 3.9 tons per ton of PVA. If the annual PVA production is 10,000 tons, the direct economic benefit is approximately 1.14 million yuan per year.

[0048] According to one aspect of the present invention, the above-mentioned distribution strategy for the three hot water sources can ensure that the system can operate safely, stably, and efficiently after the technical upgrade, while also achieving the comprehensive utilization of hot water and reducing production costs.

[0049] According to one aspect of the present invention, the high-temperature hot water can not only heat the feed material in the methyl acetate crude fractionation tower, but also be used for heat exchange of the bottom material in the catalytic decomposition tower via the first and second reboilers. If other devices do not have feed heat exchange devices, the hot water is directly sent to the newly added coolers for cooling, and then returned to the respective water points for reuse.

[0050] According to one aspect of the present invention, because the feed to the methyl acetate crude fractionation tower contains powder, it is easy to cause blockage of the tower plates, feed pipelines, and the bottom pipelines of the methyl acetate crude fractionation tower. On average, demineralized water needs to be added and boiled once a month. The hot water from the bottom of the methanol purification tower passes through a flash tank, then to the first reboiler, then to the horizontal heat exchanger for feeding the methyl acetate crude fractionation tower, and then to the newly added cooler (i.e., plate cooler). This hot water can also exchange heat with the feed to the methyl acetate crude fractionation tower, and at the same time replace the demineralized water for boiling and washing the tower plates, the twentieth feed pipeline, and the bottom pipelines of the methyl acetate crude fractionation tower, saving the amount of demineralized water, improving water resource utilization, and reducing sewage discharge. With the above setup, based on the calculation that the nineteenth pipeline of the methyl acetate crude fractionation tower bottom discharge and the twentieth pipeline of the feeding line are boiled and washed once a month on average, approximately 30,000 tons of steam will be saved per year, approximately 2,000 tons of demineralized water will be saved per year, approximately 2,000 tons of sewage discharge will be reduced per year, and the direct economic benefit will be approximately 32,000 yuan per year.

[0051] According to one aspect of the present invention, by employing a shell-and-tube horizontal heat exchanger, the frequency of equipment cleaning is reduced, the amount of demineralized water used is saved, and the amount of wastewater discharged is reduced. Alternatively, a filter can be added to the twentieth feed line of the methyl acetate coarse fractionation tower to filter polyvinyl alcohol powder in the feed, ensuring the normal operation of the entire unit. Furthermore, by using a shell-and-tube horizontal heat exchanger, the methyl acetate coarse fractionation tower can be continuously fed and heated, effectively reducing the steam consumption of the tower (before the shell-and-tube horizontal heat exchanger, the original plate heat exchanger was prone to clogging and operated intermittently; during periods of downtime, the feed temperature of the methyl acetate coarse fractionation tower was low, requiring increased steam consumption for heating the feed; now, with the horizontal heat exchanger, the methyl acetate coarse fractionation tower can be continuously fed and heated, saving steam). Through the above configuration, the number of cleaning operations for the shell-and-tube horizontal heat exchanger is effectively reduced, ensuring continuous operation of the equipment for more than three years, greatly improving the equipment's operating rate. Attached Figure Description

[0052] Figure 1 A schematic diagram illustrating a high-temperature hot water comprehensive utilization device according to an embodiment of the present invention;

[0053] Figure 2 A schematic diagram illustrating a high-temperature hot water comprehensive utilization device according to another embodiment of the present invention;

[0054] Figure 3 The diagram schematically illustrates a high-temperature hot water comprehensive utilization device according to another embodiment of the present invention.

[0055] 1. Methanol purification tower; 2. Catalytic decomposition tower; 3. Flash tank; 4. First reboiler; 5. Second reboiler; 6. Methyl acetate purification tower; 7. Cooler; 8. Centrifugal pump; 9. Methyl acetate coarse separation tower; 10. Horizontal heat exchanger; 11. First pipeline; 21. Second pipeline; 31. Third pipeline; 41. Fourth pipeline; 42. Fifth pipeline; 421. First drain pipe; 51. Sixth pipeline; 32. Seventh pipeline; 33. Eighth pipeline; 34. Liquid level control device; 61. Ninth pipeline; 62. Tenth pipeline Pipeline 63 (11th), Pipeline 22 (12th), Pipeline 71 (13th), Pipeline 72 (14th), Circulating Water Pipeline 73 (15th), Pipeline 81 (16th), Pipeline 91 (17th), Pipeline 92 (18th), Pipeline 93 (19th), Pipeline 101 (20th), Pipeline 102 (21st), Pipeline 103 (22nd), Pipeline 104 (23rd), Pipeline 105 (24th), Pipeline 94 (25th), Pipeline 95 (26th), Pipeline 951 (27th) Detailed Implementation

[0056] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly described below. Obviously, the drawings described below are merely some embodiments of the present invention, and those skilled in the art can obtain other drawings based on these drawings without creative effort.

[0057] When describing embodiments of the present invention, the terms "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer" express orientations or positional relationships based on the orientations or positional relationships shown in the relevant drawings. They are only for the convenience of describing the present invention 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. Therefore, the above terms should not be construed as limitations on the present invention.

[0058] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. The embodiments cannot be described in detail here, but the embodiments of the present invention are not limited to the following embodiments.

[0059] like Figure 1 As shown, according to one embodiment of the present invention, a high-temperature hot water comprehensive utilization device for a polyvinyl alcohol waste liquid recovery system includes: a methanol purification tower 1, a catalytic decomposition tower 2, a flash tank 3, and a first reboiler 4 and a second reboiler 5 for the catalytic decomposition tower 2. In this embodiment, the methanol purification tower 1 and the first reboiler 4 are respectively connected to the flash tank 3, and the catalytic decomposition tower 2 is connected to the first reboiler 4 and the second reboiler 5. In this embodiment, the first reboiler 4 and the second reboiler 5 are arranged in parallel.

[0060] like Figure 1 As shown, according to one embodiment of the present invention, the reboiler of the methanol purification tower 1 is connected to the inlet of the flash tank 3 via a first pipeline 11. In this embodiment, the reboiler of the catalytic decomposition tower 2 is connected to the lower inlets of the first reboiler 4 and the second reboiler 5 via a second pipeline 21. The steam outlet of the flash tank 3 is connected to the upper inlet of the first reboiler 4 via a third pipeline 31. In this embodiment, the upper outlets of the first reboiler 4 and the second reboiler 5 are connected to the lower part of the catalytic decomposition tower 2 via a fourth pipeline 41. In this embodiment, the lower outlet of the first reboiler 4 is connected to the first pipeline 11 via a fifth pipeline 42.

[0061] According to the present invention, by setting up a flash tank 3, the high-temperature hot water (temperature of 120-140℃) from the bottom of the methanol purification tower 1 can enter the tank tangentially along the flash tank 3. Due to the effect of fluid two-phase flow and eddy separation, after the tank expands, the pressure decreases, and secondary flash steam (temperature of 120-130℃) will be generated in the tank. This steam can then be introduced into the first reboiler 4 through the third low-pressure steam pipeline 31. This reboiler 4 heats the material introduced from the bottom of the catalytic decomposition tower 2 through the second pipeline 21 (the hot water temperature after heat exchange with the flowing material is 90-100℃). This allows the heat energy carried by the liquid in the bottom of the methanol purification tower 1 to be recovered and utilized. At the same time, it can maintain the temperature of the bottom of the catalytic decomposition tower 2 at 70-85℃ to ensure the normal operation of the catalytic decomposition tower 2. This achieves the recovery and utilization of low-quality heat energy while maintaining the normal operation of the catalytic decomposition tower 2, effectively improving the energy utilization rate of the present invention, reducing the energy consumption of the present invention, and saving production costs. With the above setup, it can save about 1.32 tons of steam per ton of polyvinyl alcohol per year. If the annual production of polyvinyl alcohol is 10,000 tons, it will generate direct economic benefits of about 790,000 yuan per year.

[0062] like Figure 1 As shown, according to one embodiment of the present invention, a first drain pipe 421 for discharging sewage is provided on the fifth pipe 42.

[0063] According to the present invention, by setting a first drain pipe 421 on the fifth pipeline 42, the water discharged from the bottom of the methanol purification tower 1 and the first reboiler 4 can be discharged. This is beneficial for the system to discharge water with more solid impurities after long-term operation, which is conducive to ensuring the long-term stable operation of the entire system.

[0064] like Figure 1 As shown, according to one embodiment of the present invention, the upper inlet of the second reboiler 5 is connected to a sixth pipe 51 for connecting to an external steam source.

[0065] According to the present invention, by providing a second reboiler 5 and a sixth pipeline 51 for conveying external steam, it is possible to ensure that the second reboiler 5 can supplement the heat energy when the first reboiler 4 fails to work or the heat supply is insufficient, which is beneficial to ensuring the stable operation of the present invention.

[0066] like Figure 1 As shown, according to one embodiment of the present invention, the drain port of the flash tank 3 is connected to a seventh pipe 32 and an eighth pipe 33. In this embodiment, the flash tank 3 is also provided with a liquid level control device 34 for controlling the on / off state of the eighth pipe 33.

[0067] According to the present invention, by providing multiple drain pipes on the flash tank 3, the flash tank 3 can still be drained even if one drain pipe is blocked, which is beneficial for ensuring the long-term continuous operation of the flash tank. Furthermore, by using a liquid level control device to control one of the drain pipes, the draining of the flash tank of the present invention can be dynamically controlled, which is beneficial for improving the draining efficiency and the stable operation of the system.

[0068] like Figure 2 As shown, according to one embodiment of the present invention, the high-temperature hot water comprehensive utilization device of the polyvinyl alcohol waste liquid recovery system of the present invention further includes: a methyl acetate purification tower 6, a cooler 7, and a centrifugal pump 8. In this embodiment, the methyl acetate purification tower 6 is connected to the cooler 7, and the cooler 7 is connected to the flash tank 3 via the centrifugal pump 8. In this embodiment, the cooler 7 is a plate cooler.

[0069] like Figure 2 As shown, according to one embodiment of the present invention, the methyl acetate purification tower 6 is provided with a ninth pipeline 61 at its upper part for inputting external demineralized water, a tenth pipeline 62 at its top for connecting to the catalytic decomposition tower 2, and an eleventh pipeline 63 at its bottom for connecting to the methanol purification tower 1. In this embodiment, the ninth pipeline 61 is connected to the upper part of the methyl acetate purification tower 6, the tenth pipeline 62 is connected to the middle part of the catalytic decomposition tower 2, and the eleventh pipeline 63 is connected to the upper part of the methanol purification tower 1. In this embodiment, the top of the catalytic decomposition tower 2 is provided with a twelfth pipeline 22 connected to the methyl acetate purification tower 6. The twelfth pipeline 22 is connected to the upper part of the methyl acetate purification tower 6.

[0070] like Figure 2 As shown, according to one embodiment of the present invention, the cooler 7 is provided with a thirteenth pipe 71 connected to the ninth pipe 61, and a fourteenth pipe 72 connected to the outlet of the centrifugal pump 8. In this embodiment, the cooler 7 is also provided with a circulating water pipe 73 for connecting to external circulating water. In this embodiment, the inlet of the centrifugal pump 8 is provided with a fifteenth pipe 81 connected to the flash tank 3.

[0071] like Figure 2 As shown, according to one embodiment of the present invention, the first drain pipe 421 on the fifth pipe 42 is connected to the fifteenth pipe 81 through the sixteenth pipe 82.

[0072] According to the present invention, wastewater reuse is achieved by connecting the sixteenth pipe 82 to the fifteenth pipe 81.

[0073] like Figure 1 As shown, according to one embodiment of the present invention, multiple centrifugal pumps 8 are arranged in parallel. In this embodiment, two centrifugal pumps 8 are arranged in parallel.

[0074] According to the present invention, by arranging multiple centrifugal pumps 8 in parallel, the flow between the fifteenth pipeline 81 and the fourteenth pipeline 72 is made smoother, avoiding the drawback of pipeline blockage caused by the blockage of a single centrifugal pump 8, and thus ensuring the stable operation of the entire pipeline. Furthermore, by arranging multiple centrifugal pumps 8 in parallel, the flow rate between the fifteenth pipeline 81 and the fourteenth pipeline 72 can be effectively controlled by changing the number of operating centrifugal pumps, thereby improving the flexibility of the present invention.

[0075] According to the present invention, by adding a first reboiler 4, a flash tank 3, a centrifugal pump 8, and a plate cooler 7, the hot water (temperature of 120-140℃) in the bottom of the methanol purification tower 1 is cooled by two stages of heat exchange in the newly added first reboiler 4 (hot water temperature of 90-100℃ after heat exchange with the material) and cooler 7 (water temperature of 30-40℃ after heat exchange) before being sent to the methyl acetate purification tower 6 as extraction water to replace part of the demineralized water for recycling. This not only reduces the steam consumption of the catalytic decomposition tower 2, but also saves the amount of demineralized water, improves water resource utilization, and reduces the amount of wastewater discharged. Through the above configuration, approximately 1.32 tons of steam per ton of polyvinyl alcohol can be saved, approximately 3.64 tons of demineralized water per ton of polyvinyl alcohol can be saved, and approximately 3.64 tons of wastewater discharged per ton of polyvinyl alcohol can be reduced. If the annual production of polyvinyl alcohol is 10,000 tons, the direct economic benefit is approximately RMB 1.045 million per year.

[0076] like Figure 3 As shown, according to one embodiment of the present invention, the high-temperature hot water comprehensive utilization device of the polyvinyl alcohol waste liquid recovery system of the present invention further includes: a methyl acetate coarse separation tower 9 and a horizontal heat exchanger 10. In this embodiment, the methyl acetate coarse separation tower 9 is connected to the methanol purification tower 1, the methyl acetate purification tower 6, the cooler 7, and the horizontal heat exchanger 10, respectively. In this embodiment, the horizontal heat exchanger 10 is connected to the flash tank 3, the methyl acetate coarse separation tower 9, and the fourteenth pipeline 72 between the cooler 7 and the centrifugal pump 8.

[0077] like Figure 3As shown, according to one embodiment of the present invention, the upper part of the methyl acetate crude fractionation tower 9 is provided with a seventeenth pipe 91 for inputting external demineralized water, the top of which is provided with an eighteenth pipe 92 for connection to the methyl acetate purification tower 6, and the bottom of the tower is provided with a nineteenth pipe 93 connected to an eleventh pipe 63. In this embodiment, the eighteenth pipe 92 is connected to the middle part of the methyl acetate purification tower 6.

[0078] like Figure 3 As shown, according to one embodiment of the present invention, the horizontal heat exchanger 10 is provided with a twentieth pipe 101 for inputting alcoholysis waste liquid, a twenty-first pipe 102 for connecting to the middle of the methyl acetate crude separation tower 9, and a twenty-second pipe 103 and a twenty-third pipe 104 connected to the first drain pipe 421 on the fifth pipe 42. In this embodiment, control valves for controlling their on / off states are respectively provided on the twenty-second pipe 103 and the twenty-third pipe 104.

[0079] like Figure 3 As shown, according to one embodiment of the present invention, a twenty-fourth pipeline 105 is connected between the twentyth pipeline 101 and the twenty-first pipeline 102. In this embodiment, a control valve for controlling its on / off state is provided on the twenty-fourth pipeline 105. This arrangement ensures the supply of methyl acetate crude fractionation tower 9 during maintenance of the horizontal heat exchanger 10.

[0080] like Figure 3 As shown, according to one embodiment of the present invention, the methyl acetate crude fractionation tower 9 is further provided with a twenty-fifth pipe 94 for connecting the seventeenth pipe 91 and the thirteenth pipe 71, and a twenty-sixth pipe 95 for connecting the nineteenth pipe 93 and the fourteenth pipe 72. In this embodiment, a twenty-seventh pipe 951 for connecting the twentieth pipe 101 is also provided on the twenty-seventh pipe 951. In this embodiment, a control valve for controlling its on / off state is provided on the twenty-seventh pipe 951.

[0081] According to the present invention, by adding a flash tank 3, a reboiler 4 (i.e., a first reboiler), a cooler 7, a horizontal heat exchanger 10, and a centrifugal pump 8, high-temperature hot water (temperature 120-140℃) first enters the flash tank 3. The flash vapor (temperature 120-130℃) at the top of the flash tank 3 enters the first reboiler 4 for heat exchange. The hot water after heat exchange (temperature 90-100℃) is fed from the bottom of the first reboiler 4 into the horizontal heat exchanger 10, and then from the horizontal heat exchanger 10 to the methyl acetate crude fractionation tower 9. The water, heated by feeding and then cooled (60-80℃), combines with the hot water discharged from the bottom of the flash tank (90-100℃). This mixture is then pumped via a newly added centrifugal pump: one route is sent to the nineteenth pipeline 93 of the methyl acetate coarse separation tower 9 (connected via pipeline 95); another route is sent to the twentieth pipeline 101 of the methyl acetate coarse separation tower 9; and the third route is sent to the newly added cooler 7 for cooling. The cooled hot water is then returned to the methyl acetate coarse separation tower 9 and the methyl acetate purification tower 6 for reuse. This setup saves approximately 1.6 tons of steam per ton of polyvinyl alcohol (PVA), saves approximately 3.9 tons of demineralized water per ton of PVA, and reduces wastewater discharge by approximately 3.9 tons per ton of PVA. If the annual PVA production is 10,000 tons, the direct economic benefit is approximately 1.14 million yuan per year.

[0082] To further illustrate this solution, the workflow of this solution will be further explained in conjunction with the accompanying drawings.

[0083] Figure 1 :

[0084] The process shown in the diagram applies to the recycling process. The process is as follows: The feed to methanol purification tower 1 comes from the methanol solution (temperature 70-90℃) in the methyl acetate crude fractionation tower 9 and the bottom liquid of methyl acetate purification tower 6. The refined methanol distilled from the top of methanol purification tower 1 is sent to the tank area. The high-temperature wastewater (temperature 120-140℃) in the bottom liquid of methanol purification tower 1 enters the flash tank 3 through the first pipeline 11 for gas-liquid separation. The gas phase (temperature 120-130℃) at the top of flash tank 3 is sent to the newly added first reboiler 4 of catalytic decomposition tower 2 through the third pipeline 31 as a heat source. The hot water (temperature 90-100℃) after heat exchange enters the first sewage pipe 421 through the fifth pipeline 42 and is discharged into the ditch. The feed to catalytic decomposition tower 2 is methyl acetate distilled from methyl acetate purification tower 6 (temperature 56-65℃). The top distillate of catalytic decomposition tower 2 (methyl acetate and methanol, temperature 50-68℃) is basically total reflux and sent to methyl acetate purification tower 6 for further processing. The second reboiler 5 is the original direct steam heat exchange reboiler of catalytic decomposition tower 2. The sixth pipeline 51 is a direct steam pipeline. The bottom liquid of catalytic decomposition tower 2 (acetic acid, methanol, and methyl acetate, temperature 70-85℃) enters the first reboiler 4 and the second reboiler 5 through the second pipeline 21 for heat exchange. The heated steam returns to the tower from the top of the first reboiler 4 and the second reboiler 5 through the fourth pipeline 41. The bottom liquid of catalytic decomposition tower 2 is the feed to the acetic acid crude fractionation tower (temperature 70-85℃). The bottom of the flash tank 3 is equipped with a seventh pipe 32 and an eighth pipe 33, each with a drain valve. The liquid level of the flash tank is remotely controlled by the regulating valve on the eighth pipe 33. The seventh pipe 32 serves as a backup for the eighth pipe 33. The liquid level control device 34 is a flash tank liquid level gauge.

[0085] Figure 2 :

[0086] Figure 2 exist Figure 1Based on the existing equipment, the following new equipment has been added: methyl acetate purification tower 6, cooler 7, and centrifugal pump 8. The feed for methyl acetate purification tower 6 is crude methyl acetate (temperature 55-60℃) distilled from methyl acetate crude fractionation tower 9. The feed for methanol purification tower 1 is methanol solution (temperature 70-90℃) from the bottom liquid of methyl acetate crude fractionation tower 9 and methyl acetate purification tower 6. The refined methanol distilled from the top of methanol purification tower 1 is sent to the tank area. The high-temperature wastewater (temperature 120-140℃) from the bottom liquid of methanol purification tower 1 enters flash tank 3 through the first pipeline 11 for gas-liquid separation. The gas phase (temperature 120-130℃) at the top of flash tank 3 is sent to the newly added first reboiler 4 of catalytic decomposition tower 2 through the third pipeline 31 as a heat source. The hot water (temperature 90-100℃) after heat exchange enters the first sewage pipe 421 through the fifth pipeline 42 and is discharged into the ditch. Methyl acetate (56-65℃) distilled from methyl acetate purification tower 6 is fed to catalytic decomposition tower 2 via the tenth pipeline 62. The top distillate of catalytic decomposition tower 2 (methyl acetate and methanol, 50-68℃) is basically total reflux and sent to methyl acetate purification tower 6 for further processing via pipeline 22. The second reboiler 5 is the original direct steam heat exchange reboiler of catalytic decomposition tower 2. The sixth pipeline 51 is a direct steam pipeline (220-250℃). The bottom liquid of catalytic decomposition tower 2 (acetic acid, methanol, and methyl acetate, 70-85℃) enters the first reboiler 4 and the second reboiler 5 respectively through the second pipeline 21 for heat exchange. The heated steam returns to the tower from the top of the first reboiler 4 and the second reboiler 5 through the fourth pipeline 41. The bottom liquid of catalytic decomposition tower 2 is the feed from the acetic acid crude fractionation tower (70-85℃). Drain valves are installed on the seventh pipe 32 and the eighth pipe 33 at the bottom of the flash tank 3. The liquid level of the flash tank 3 is remotely controlled by the regulating valve on the eighth pipe 33. The seventh pipe 32 serves as a backup for the eighth pipe 33. 34 is a level gauge for the flash tank. A sixteenth pipe 82 is added to the first drain pipe 421, and a fifteenth pipe 81 is added to the bottom of the flash tank 3. Both the sixteenth pipe 82 and the fifteenth pipe 81 serve as the feed for the centrifugal pump 8. The outlet of the centrifugal pump 8 is sent to the cooler 7 for cooling through the fourteenth pipe 72. The cooler 7 is cooled by circulating water through the circulating water pipe 73. The cooled water (temperature 30-40℃) is connected to the ninth demineralized water pipe 61 of the original methyl acetate purification tower 6 through the thirteenth pipe 71, reducing the amount of demineralized water used in the methyl acetate purification tower 6.

[0087] Figure 3 :

[0088] Figure 3 exist Figure 2Based on the existing equipment, two new components were added: a methyl acetate coarse separation tower 9 and a horizontal heat exchanger 10. The main function of the methyl acetate coarse separation tower 9 is to coarsely separate methyl acetate. The crude methyl acetate distillate from the top of the methyl acetate coarse separation tower 9 (temperature 55-60℃) is fed to the methyl acetate purification tower 6 through the eighteenth pipeline 92. The methanol solution (temperature 65-75℃) from the bottom of the methyl acetate coarse separation tower 9 is sent to the methanol purification tower 1 for further purification through the nineteenth pipeline 93. The horizontal heat exchanger 10 is a feed heat exchanger for the methyl acetate coarse separation tower 9. The feed is the alcoholysis waste liquid from the tank area, mainly composed of methyl acetate and methanol. It is sent to the horizontal heat exchanger 10 through the twentieth pipeline 101. After heat exchange, it is sent to the methyl acetate coarse separation tower 9 through the twenty-first pipeline 102 (temperature 50-65℃). The seventeenth pipeline 91 is the demineralized water supply line for the methyl acetate coarse separation tower 9.

[0089] The feed to methanol purification tower 1 comes from the methanol solution (temperature 70-90℃) in the crude methyl acetate column 9 and the bottom liquid of methyl acetate purification tower 6. The refined methanol distilled from the top of methanol purification tower 1 is sent to the tank area. The high-temperature wastewater (temperature 120-140℃) in the bottom liquid of methanol purification tower 1 enters the flash tank 3 through the first pipeline 11 for gas-liquid separation. The gas phase (temperature 120-130℃) at the top of flash tank 3 is sent to the newly added first reboiler 4 of catalytic decomposition tower 2 through the third pipeline 31 as a heat source. The hot water after heat exchange enters the first sewage pipe 421 through the fifth pipeline 42 and is discharged into the ditch. Methyl acetate (56-65℃) distilled from methyl acetate purification tower 6 is fed to catalytic decomposition tower 2 via the tenth pipeline 62. The top distillate from catalytic decomposition tower 2 (50-68℃) is essentially total reflux and is sent to methyl acetate purification tower 6 for further processing via the twelfth pipeline 22. The second reboiler 5 is the original direct steam heat exchange reboiler of catalytic decomposition tower 2. The sixth pipeline 51 is a direct steam line (220-250℃). The bottom liquid of catalytic decomposition tower 2 (acetic acid, methanol, methyl acetate, 70-85℃) enters the first reboiler 4 and the second reboiler 5 respectively via the second pipeline 21 for heat exchange. The heated steam returns to the tower from the top of the first reboiler 4 and the second reboiler 5 via the fourth pipeline 41. The bottom liquid of catalytic decomposition tower 2 (70-85℃) is the feed for the acetic acid crude fractionation tower. The flash tank 3 has pipes 32 and 33 at its bottom, and a drain valve. The liquid level in the flash tank is remotely controlled by a regulating valve on pipe 33. Pipe 32 serves as a backup for pipe 33, and pipe 34 is a level gauge for the flash tank. A sixteenth pipe 82 is located on the first drain pipe 421, and a fifteenth pipe 81 is located at the bottom of the flash tank 3. Both pipes 82 and 81 serve as feed for the centrifugal pump 8.

[0090] Centrifugal pump 8 has three outlets. One outlet is sent to cooler 7 via the fourteenth pipe 72 for cooling. Cooler 7 uses circulating water (temperature 20-35℃) via circulating water pipe 73 for cooling. The cooled water (temperature 30-40℃) is then connected to the ninth pipe 61 of the demineralized water (temperature 10-25℃) of the original methyl acetate purification tower 6 and the seventeenth pipe 91 of the demineralized water (temperature 10-25℃) of the methyl acetate coarse separation tower 9 via the thirteenth pipe 71 and the twenty-fifth pipe 94, respectively, thereby reducing the amount of demineralized water used in the methyl acetate coarse separation tower 9 and the methyl acetate purification tower 6. Secondly, the cleaning water from pipe 27 (951) used for daily feeding of the methyl acetate coarse fractionation tower 9 via pipe 20 (101) replaces the demineralized water. Since polyvinyl alcohol powder dissolves easily at high temperatures, hot water (90-100℃) is more effective than demineralized water (10-25℃) for cleaning the pipes, resulting in a cleaner and more thorough cleaning. The cleaning frequency is reduced from once a quarter to once every six months. Thirdly, the hot water is sent to the bottom of the methyl acetate coarse fractionation tower 9 via pipe 26 (95) to replace the demineralized water used for washing the tower plates. Hot water (90-100℃) itself carries heat, and its temperature is much higher than that of the demineralized water. Therefore, using hot water instead of demineralized water for washing the tower plates not only saves heat but also significantly reduces the amount of demineralized water used, reduces wastewater discharge, and saves on direct steam usage.

[0091] The horizontal heat exchanger 10 has hot water (90-100℃) as the heating medium on the right side, which flows through the shell side. The hot water inlet (90-100℃) pipe 103 and outlet (60-80℃) pipe 104 are connected to the fifth pipe 42 and the sixteenth pipe 82, respectively, and are equipped with a bypass first drain pipe 421. The horizontal heat exchanger 10 has alcoholysis waste liquid (30-40℃) as the cold medium on the left side, which flows through the tube side. The inlet (30-40℃) pipe 101 and outlet (50-65℃) pipe 102 are connected to the twentieth pipe 101 and the twenty-first pipe 102 20-65. A bypass twenty-fourth pipe 105 is provided before the twentieth and twenty-first pipes 101 and 102. If the horizontal heat exchanger 10 is not in use or under maintenance, the bypass first drain pipe 421 and twenty-fourth pipe 105 are activated. Because the alcoholysis waste liquid contains polyvinyl alcohol powder, and to facilitate cleaning after equipment blockage, the design specifies that hot water flows through the shell side and alcoholysis waste liquid flows through the tube side.

[0092] According to the present invention, by adding a flash tank 3, a reboiler 4 (i.e., a first reboiler), a cooler 7, a horizontal heat exchanger 10, and a centrifugal pump 8, high-temperature hot water (temperature 120-140℃) first enters the flash tank 3. Flash steam (temperature 120-130℃) from the top of the flash tank 3 enters the first reboiler 4 for heat exchange. The hot water after heat exchange (temperature 90-100℃) is fed from the bottom of the first reboiler 4 into the horizontal heat exchanger 10 to feed and heat up the methyl acetate crude fractionation tower 9. The cooled hot water... Water (temperature 60-80℃) and hot water (temperature 90-100℃) discharged from the bottom of the flash tank are combined and sent through the newly added centrifugal pump 8. One pump sends the hot water to the bottom pipeline 23 (93) of the methyl acetate crude fractionation tower 9, another pump sends it to the feed pipeline 20 (101) of the methyl acetate crude fractionation tower 9, and the third pump sends it to the newly added cooler 7 for cooling. The cooled hot water (temperature 30-40℃) is then returned to the methyl acetate crude fractionation tower 9 and the methyl acetate purification tower 6 for reuse. By distributing the hot water in three ways, approximately 15-30 m³ of hot water is reused in the methyl acetate purification tower 6 during normal operation of each tower. 3 / h (accounting for 75% of the total hot water), the hot water reuse rate of methyl acetate crude separation tower 9 is approximately 1-5m³. 3 / h (accounting for 15% of the total hot water volume), the flash tank emptying valve continuously drains approximately 2-4m. 3 / h (accounting for 10% of the total hot water). Because the feed to the methyl acetate crude fractionation tower 9 contains powder, it easily causes blockages in the tower trays, feed lines, and the reboiler lines of the methyl acetate crude fractionation tower 9. On average, it needs to be boiled and washed with demineralized water once a month. When the methyl acetate crude fractionation tower 9 needs to be shut down for washing, the hot water reuse rate of the methyl acetate purification tower 6 will decrease to approximately 5-10 m³ / h. 3 / h (accounting for 40% of the total hot water), the hot water reuse rate of methyl acetate crude fractionation tower 9 is increased to approximately 20-25m³. 3 / h (accounting for 60% of the total hot water), the recycled hot water can replace the demineralized water and be used to wash the trays of the methyl acetate coarse separation tower 9 through the 25th pipeline 94. It is also fed into the 20th feed pipeline 101 through the 27th pipeline 951 and into the bottom pipeline of the methyl acetate coarse separation tower 9 through the 26th pipeline 95 to the 19th pipeline 93. This saves demineralized water consumption, improves water resource utilization, and reduces sewage discharge. With the above settings, based on the calculation that the bottom discharge pipeline 93 of the methyl acetate coarse separation tower 9 and the 20th feed pipeline 101 are washed once a month on average, approximately 30,000 tons of steam will be saved per year, approximately 2,000 tons of demineralized water will be saved per year, and approximately 2,000 tons of sewage discharge will be reduced per year, generating direct economic benefits of approximately 32,000 yuan per year.

[0093] According to the present invention, the high-temperature hot water can not only heat the feed material in the methyl acetate crude fractionation tower 9, but also be used for heat exchange of the bottom material in the catalytic decomposition tower 2 through the first reboiler 4. If other devices do not have feed heat exchange devices, the hot water is directly sent to the newly added cooler 7 for cooling, and then returned to the respective water points for reuse.

[0094] According to the present invention, by employing a shell-and-tube horizontal heat exchanger 10, the frequency of equipment cleaning is reduced, the amount of demineralized water used is saved, and the amount of wastewater discharged is reduced. Alternatively, a filter can be added to the twentieth feed line 101 of the methyl acetate coarse fractionation tower 9 to filter polyvinyl alcohol powder in the feed of the methyl acetate coarse fractionation tower 9, ensuring the normal operation of the entire unit. Furthermore, by employing a shell-and-tube horizontal heat exchanger 10, the methyl acetate coarse fractionation tower 9 can be continuously fed and heat exchanged, effectively reducing the steam consumption of the methyl acetate coarse fractionation tower 9. Through the above-mentioned configuration, the cleaning frequency of the shell-and-tube horizontal heat exchanger is effectively reduced, ensuring continuous operation of the equipment for more than three years and greatly improving the equipment's operating rate.

[0095] The above description is merely an example of a specific solution of the present invention. For any devices and structures not described in detail herein, it should be understood that they are implemented using common devices and methods already available in the art.

[0096] The above description is merely one embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the invention by those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A device for the self-coupling utilization of high-temperature wastewater and hot water from alcoholysis waste liquid, characterized in that, include: Methanol purification tower (1), catalytic decomposition tower (2), flash tank (3), first reboiler (4), methyl acetate purification tower (6), cooler (7), centrifugal pump (8); The bottom of the methanol purification tower (1) is connected in sequence to the flash tank (3), the first reboiler (4), and the catalytic decomposition tower (2) via pipelines; the catalytic decomposition tower (2) is connected to the methanol purification tower (1) via the methyl acetate purification tower (6). The flash tank (3) is connected in sequence to the centrifugal pump (8), the cooler (7), and the methyl acetate purification tower (6) via pipelines; The high-temperature wastewater from the bottom of the methanol purification tower (1) enters the flash tank (3) to form flash steam and flash tank drainage. The flash steam exchanges heat with the material in the catalytic decomposition tower (2) in the first reboiler (4) and is cooled to become hot water. The hot water and the flash tank drainage are combined and cooled by the cooler (7) to obtain cooling water, which then enters the methyl acetate purification tower (6). The alcoholysis waste liquid recovery high-temperature wastewater hot water self-coupling utilization device also includes a methyl acetate crude separation tower (9) and a horizontal heat exchanger (10). The methyl acetate crude fractionation tower (9) is connected to the methanol purification tower (1), the methyl acetate purification tower (6), the cooler (7), and the horizontal heat exchanger (10), respectively. The horizontal heat exchanger (10) is connected to the flash tank (3), the methyl acetate crude fractionation tower (9), and the centrifugal pump (8) respectively. The horizontal heat exchanger (10) is a shell-and-tube horizontal heat exchanger. Polyvinyl alcohol hydrolysis waste liquid enters the horizontal heat exchanger (10) and exchanges heat with the hot water before entering the methyl acetate crude separation tower (9). The hot water is cooled down and then merged with the drainage from the flash tank.

2. The self-coupling device for recovering high-temperature wastewater and utilizing hot water from alcoholysis waste liquid according to claim 1, characterized in that, The bottom of the methanol purification tower (1) is connected to the inlet of the flash tank (3) via a first pipeline (11); The steam outlet of the flash tank (3) is connected to the upper inlet of the first reboiler (4) via a third pipeline (31); The upper outlet of the first reboiler (4) is connected to the lower part of the catalytic decomposition tower (2) via a fourth pipeline (41); The lower outlet of the first reboiler (4) is connected to the first pipeline (11) via a fifth pipeline (42); a first drain pipe (421) for draining sewage is provided on the fifth pipeline (42).

3. The self-coupling device for recovering high-temperature wastewater and utilizing hot water from alcoholysis waste liquid according to claim 1, characterized in that, It also includes a second reboiler (5) arranged in parallel with the first reboiler (4). The bottom of the catalytic decomposition tower (2) is connected to the lower inlet of the first reboiler (4) and the second reboiler (5) respectively by a second pipeline (21). The upper inlet of the second reboiler (5) is connected to a sixth pipeline (51) for connecting to an external steam source. The upper outlet of the second reboiler (5) is connected to the lower part of the catalytic decomposition tower (2) by a fourth pipeline (41).

4. The self-coupling device for recovering high-temperature wastewater and utilizing hot water from alcoholysis waste liquid according to claim 2, characterized in that, The drain outlet of the flash tank (3) is connected to the seventh pipeline (32) and the eighth pipeline (33). The flash tank (3) is also equipped with a liquid level control device (34) for controlling the opening and closing of the eighth pipeline (33).

5. The self-coupling device for recovering high-temperature wastewater and utilizing hot water from alcoholysis waste liquid according to claim 4, characterized in that, The methyl acetate purification tower (6) is provided with a ninth pipeline (61) for inputting external demineralized water at the top, a tenth pipeline (62) for connecting to the catalytic decomposition tower (2) at the top, and an eleventh pipeline (63) for connecting to the methanol purification tower (1) at the bottom. The top of the catalytic decomposition tower (2) is provided with a twelfth pipeline (22) connected to the methyl acetate purification tower (6).

6. The self-coupling device for recovering high-temperature wastewater and utilizing hot water from alcoholysis waste liquid according to claim 5, characterized in that, The cooler (7) is provided with a thirteenth pipe (71) connected to the ninth pipe (61) and a fourteenth pipe (72) connected to the outlet of the centrifugal pump (8). The cooler (7) is also provided with a circulating water pipe (73) for connecting to the external circulating water. The inlet of the centrifugal pump (8) is provided with a fifteenth pipeline (81) connected to the flash tank (3); The first sewage pipe (421) is connected to the fifteenth pipe (81) through the sixteenth pipe (82).

7. The self-coupling device for recovering high-temperature wastewater and utilizing hot water from alcoholysis waste liquid according to claim 6, characterized in that, The upper part of the methyl acetate crude fractionation tower (9) is provided with a seventeenth pipeline (91) for inputting external demineralized water, and the top of the tower is provided with an eighteenth pipeline (92) for connecting to the methyl acetate purification tower (6). The bottom of the tower is provided with a nineteenth pipeline (93) for connecting to the eleventh pipeline (63).

8. The self-coupling device for recovering high-temperature wastewater and utilizing hot water from alcoholysis waste liquid according to claim 7, characterized in that, The horizontal heat exchanger (10) is provided with a twentieth pipeline (101) for inputting alcoholysis waste liquid, a twenty-first pipeline (102) for connecting to the middle of the methyl acetate crude separation tower (9), and a twenty-second pipeline (103) and a twenty-third pipeline (104) connected to the first sewage pipe (421). The 22nd pipeline (103) and the 23rd pipeline (104) are respectively equipped with control valves for controlling their on / off states; A 24th pipeline (105) is connected between the 20th pipeline (101) and the 21st pipeline (102); a control valve for controlling its on / off state is provided on the 24th pipeline (105).

9. The self-coupling device for recovering high-temperature wastewater and utilizing hot water from alcoholysis waste liquid according to claim 8, characterized in that, The methyl acetate crude fractionation tower (9) is also provided with a twenty-fifth pipeline (94) for connecting the seventeenth pipeline (91) and the thirteenth pipeline (71), and a twenty-sixth pipeline (95) for connecting the nineteenth pipeline (93), the cooler (7) and the centrifugal pump (8) to the fourteenth pipeline (72). The 26th pipeline (95) is also provided with a 27th pipeline (951) for connecting the 20th pipeline (101); the 27th pipeline (951) is provided with a control valve for controlling its on / off state.

10. The self-coupling device for recovering high-temperature wastewater and utilizing hot water from alcoholysis waste liquid according to claim 8, characterized in that, The outlet of the centrifugal pump (8) includes: a fourteenth pipeline (72) connected to the cooler (7); the cooling water is connected to the ninth pipeline (61) of the demineralized water of the methyl acetate purification tower (6) and the seventeenth pipeline (91) of the demineralized water of the methyl acetate crude separation tower (9) via the thirteenth pipeline (71) and the twenty-fifth pipeline (94); a twenty-sixth pipeline (95) connected to the bottom of the methyl acetate crude separation tower (9); and a twenty-seventh pipeline (951) connected to the twentieth pipeline (101) for feeding the methyl acetate crude separation tower (9), for cleaning the twentieth pipeline (101).

11. A method for self-coupling the utilization of hot water from high-temperature wastewater, applied to the high-temperature wastewater hot water self-coupling utilization device as described in any one of claims 1-10, characterized in that, Includes the following steps: Step S1: The high-temperature wastewater from the bottom of the methanol purification tower (1) is passed into the flash tank (3) to form flash steam and flash tank drainage. The flash steam exchanges heat with the material of the catalytic decomposition tower (2) in the first reboiler (4) and cools down to become hot water. Step S2: The hot water obtained in step S1 is combined with the drainage from the flash tank and cooled by the cooler (7) to obtain cooling water. The cooling water is then passed into the methyl acetate purification tower (6) to replace the demineralized water for methyl acetate extraction and purification.

12. The method for self-coupling utilization of high-temperature wastewater and hot water according to claim 11, characterized in that, Also includes: Step S3: The hot water obtained in step S1 first enters the horizontal heat exchanger (10) to exchange heat with the feed polyvinyl alcohol alcoholysis waste liquid of the methyl acetate crude separation tower (9). After cooling, the hot water obtained is then combined with the drainage of the flash tank.

13. The method for self-coupling utilization of high-temperature wastewater and hot water according to claim 12, characterized in that, Also includes: Step S4: The hot water obtained in step S3 is combined with the drainage from the flash tank and enters the centrifugal pump (8) and is divided into three paths. The first path is sent to the cooler (7) through the fourteenth pipeline (72) for cooling and then sent to the methyl acetate purification tower (6) and the methyl acetate crude separation tower (9) to replace the demineralized water. The second path is sent to the feed pipe of the methyl acetate crude separation tower (9) through the twenty-seventh pipeline (951) to replace the demineralized water. The third path is sent to the bottom of the methyl acetate crude separation tower (9) through the twenty-sixth pipeline (95) to replace the demineralized water used to wash the tower plates.

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