Recycling device for isopropanol in POP (Polyoxymethylene) preparation process

Abstract

A recovery device of isopropanol in a POP preparation process is characterized by comprising a flash tank and a cyclone separator, an upper end opening of the flash tank is connected with an air inlet of the cyclone separator, and an air outlet of the cyclone separator is connected with a condenser, so that materials discharged from the air outlet of the cyclone separator are cooled. After flash evaporation, gas-phase isopropyl alcohol contained in a liquid phase is separated, the isopropyl alcohol carries a POP product to enter a cyclone separator, the isopropyl alcohol and the POP product are separated under the action of cyclone centrifugal force, and the gas-phase isopropyl alcohol is discharged out of the cyclone separator and is cooled into liquid, so that the isopropyl alcohol is well recovered.

Description

Technical Field

[0001] The utility model relates to a polymer polyol (POP) chemical production system, in particular to a recovery device of reagent isopropanol used in the preparation process of polyether polyol. Background Art

[0002] The polymer polyol (POP) process is a polymer made by using a chemical polymerization process, using isopropanol as a chain transfer agent, adding styrene, acrylonitrile and other vinyl monomers for graft copolymerization at a certain temperature and in the presence of an initiator. This polymer product has the advantages of high hardness, high resilience and high load-bearing capacity.

[0003] There will be some residual monomers, such as isopropanol, in the final polymer product. Residual isopropanol and other solvents will also affect the performance of the product. Therefore, in order to improve the performance of polymer polyols and recycle residual isopropanol and other reagents, the prior art discloses that the isopropanol and other monomers that do not participate in the reaction are recycled and reused by bubbling in a flash evaporator and then vacuum removal. However, the recycling efficiency is relatively low.

[0004] Chinese patent application publication No. CN217015373U discloses a device for recovering isopropyl alcohol in a POP production system, comprising a first flash evaporator (1), a second flash evaporator (2), a third flash evaporator (3), a fourth flash evaporator (4), a heat exchanger (5), a recovery tank (6), an isopropyl alcohol recovery tank (7) and a mist separator (8); wherein the first flash evaporator (1) and the second flash evaporator

[0005] The tail gas outlet of (2) is connected to the heat exchanger (5); the tail gas outlets of the third flash evaporator (3) and the fourth flash evaporator (4) are connected to the mist separator (8); and the recovery storage tank (6) is connected to the condensate outlet of the heat exchanger (5). The treatment process is relatively complicated by arranging multi-stage flash evaporation and heat exchange to recover isopropyl alcohol. Utility Model Content

[0006] On the one hand, the isopropyl alcohol recovery device in the POP preparation process provided by the utility model combines a flash tank with a cyclone gas-liquid separator to separate the POP product from the isopropyl alcohol well, thereby simplifying the isopropyl alcohol recovery process.

[0007] On the other hand, the isopropyl alcohol recovery device in the POP preparation process provided by the utility model improves the separation effect of the POP product and isopropyl alcohol by improving the structure of the internal components of the cyclone gas-liquid separator, that is, reduces the loss rate of the POP product and improves the recovery rate of isopropyl alcohol.

[0008] The utility model provides an isopropyl alcohol recovery device in a POP preparation process, comprising a flash tank and a cyclone separator, wherein the upper end opening of the flash tank is connected to an air inlet of the cyclone separator, and the air outlet of the cyclone separator is connected to a condenser, so that materials discharged from the air outlet of the cyclone separator are cooled.

[0009] The material entering the flash tank is a crude polymer polyol product containing isopropanol in a liquid state from the POP preparation process, which has a certain temperature, and isopropanol is mixed in the crude polymer product. After flash evaporation, the gaseous isopropanol contained in the liquid phase is separated, and the isopropanol carries the POP product into the cyclone separator. Under the action of the centrifugal force of the cyclone, the isopropanol and the POP product are separated, and the gaseous isopropanol is discharged from the cyclone separator and cooled into a liquid, that is, the isopropanol is well recovered. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 The utility model is a schematic diagram of the structure of an isopropyl alcohol recovery device in a POP preparation process.

[0011] Figure 2 It is a longitudinal cross-sectional schematic diagram of a cyclone separator of the utility model.

[0012] Figure 3 It is a cross-sectional schematic diagram of a cyclone separator of the utility model.

[0013] Markings in the figure: 1-flash tank; 2-cyclone separator; 3-condenser; 4-buffer tank; 5-buffer tank transfer pump; 20-lower partition; 20-lower partition; 21-air inlet; 22-air outlet; 23-liquid outlet; 24-first-stage cyclone tube; 25-second-stage cyclone tube; 26-horizontal partition; 27-isolation tube; 28-shell; 29-upper partition. DETAILED DESCRIPTION

[0014] The following is a further detailed description of the isopropyl alcohol recovery device in the POP preparation process of the present application. The protection scope of the present application is not limited, and its protection scope is defined by the claims. Certain disclosed specific details provide a comprehensive understanding of each disclosed embodiment. However, those skilled in the relevant art know that the embodiment can be implemented without using one or more of these specific details and using other materials, etc.

[0015] Unless the context requires otherwise, in the specification and claims, the terms "include" and "comprising" should be construed as having an open-ended, inclusive meaning, that is, "including, but not limited to".

[0016] The "embodiment", "one embodiment", "another embodiment" or "certain embodiments" mentioned in the specification means that the specific features, structures or characteristics described in connection with the embodiment are included in at least one embodiment. Therefore, "embodiment", "one embodiment", "another embodiment" or "certain embodiments" do not necessarily all refer to the same embodiment. Moreover, specific features, structures or characteristics may be combined in any manner in one or more embodiments. Each feature disclosed in the specification may be replaced by any alternative feature that can provide the same, equal or similar purpose. Therefore, unless otherwise specified, the disclosed features are only general examples of equal or similar features.

[0017] In the polymer polyol (POP) process, the amount of isopropyl alcohol added is 5-8w%. In order to make better use of isopropyl alcohol, the isopropyl alcohol recovery device of the utility model is added to the POP process, that is, a flash tank, a cyclone gas-liquid separator, and an isopropyl alcohol recovery condenser are arranged to recover isopropyl alcohol to the maximum extent under vacuum operation conditions.

[0018] The utility model discloses a recovery device for isopropyl alcohol in a POP preparation process, comprising a flash tank and a cyclone separator, wherein the upper end opening of the flash tank is connected to an air inlet of the cyclone separator, and the air outlet of the cyclone separator is connected to a condenser, so that materials discharged from the air outlet of the cyclone separator are cooled.

[0019] Compared with the traditional recovery process, the cyclone gas-liquid separator is a newly installed equipment. The trace droplets carried in the gas phase gather and settle under the action of the cyclone separation internals and return to the flash tank, reducing the loss rate of the product POP.

[0020] The separation internals of the cyclone separator can adopt the structure of the prior art, and preferably use the separation internal structure provided by the utility model.

[0021] In one embodiment of the utility model, a cyclone separator includes a shell and a separation internal component arranged in the shell, the separation internal component includes a primary cyclone tube, a secondary cyclone tube and an isolation tube, the isolation tube divides the space where the separation internal component is located into an internal space and an outer ring space in a first direction of the shell, the primary cyclone tube is located in the outer ring space, the secondary cyclone tube is located in the internal space, and a horizontal partition is arranged in a second direction in the shell, the horizontal partition is respectively connected to the inner wall of the shell and the outer wall of the isolation tube, and divides the outer ring space where the separation internal component is located into upper and lower partitions.

[0022] The shell of the cyclone separator is provided with an air inlet, and the gas-liquid mixture introduced through the air inlet enters the outer annular space of the separation internals at high speed for primary gas-liquid separation, and the gas discharged through the upper opening of the primary cyclone tube enters the inner space of the separation internals for secondary gas-liquid separation, and the gas discharged from the upper opening of the secondary cyclone tube is discharged to the outside of the separator through the air outlet. After two series separations, POP and isopropyl alcohol can be separated efficiently, the recovery rate of isopropyl alcohol is improved, and the loss rate of POP products is further reduced.

[0023] The first direction intersects with the second direction at a certain angle. Preferably, the angle at which the first direction intersects with the second direction is in the range of 60-90°, and more preferably, the angle at which the first direction intersects with the second direction is about 90°.

[0024] In some embodiments, the isolation tube is a tubular structure with a constant diameter, or a tubular structure with a variable diameter.

[0025] The cross section of the shell is circular, and the isolation tube and the shell are arranged concentrically. The outer annular space of the space where the separation internal part is located is the space surrounded by the outer wall of the isolation tube and the inside of the shell, and the internal space is the space inside the isolation tube.

[0026] The separation internals include an upper partition and a lower partition fixedly arranged in the shell. The upper partition and the lower partition are used to fix and install the primary cyclone tube and the secondary cyclone tube. The two ends of the isolation tube are respectively fixed to the lower partition and the upper partition.

[0027] A through hole is provided on the wall of the isolation tube to connect the outer annular space and the inner space where the separation internals are located. The gas after the primary gas-liquid separation can flow into the inner space through the through hole for secondary gas-liquid separation.

[0028] There can be multiple through holes, and the multiple through holes can be evenly arranged along the circumferential direction of the isolation tube. The aperture size of the through holes is not limited, and the size and density of the through holes can be calculated according to the processing volume.

[0029] An optional solution is to open a continuous opening in a certain height range of the isolation pipe in the circumferential direction. That is, the isolation pipe is divided into two sections, an upper isolation pipe and a lower isolation pipe, and there is a gap between the upper and lower isolation pipes. The size of the gap can be determined according to the processing volume.

[0030] Optionally, the diameters of the upper isolation tube and the lower isolation tube may be the same or different.

[0031] Alternatively, the lower end of the isolation tube is fixed to the lower partition plate, and a gap is provided between the upper end of the isolation tube and the upper partition plate, so as to connect the outer annular space and the inner space where the separation internals are located.

[0032] The horizontal partition of the utility model is located between the upper partition and the lower partition.

[0033] The upper surface of the horizontal partition is lower than the upper end of the first-stage cyclone tube. That is, the upper end of the first-stage cyclone tube passes through the horizontal partition and is located in the space between the horizontal partition and the upper partition.

[0034] The through hole or opening on the isolation tube is located in the space between the horizontal partition and the upper partition. The gas discharged from the upper end of the primary cyclone tube can enter the internal space of the isolation tube through the through hole or opening on the isolation tube for secondary gas-liquid separation.

[0035] The upper end of the secondary cyclone tube passes through the upper partition. After the secondary gas-liquid separation in the isolation tube, the gas is discharged through the upper end of the secondary cyclone tube, enters the upper space of the shell, and is discharged to the outside of the cyclone separator through the gas outlet.

[0036] In some embodiments, a plurality of primary cyclone tubes and a plurality of secondary cyclone tubes may be provided, wherein the number of the primary cyclone tubes is greater than the number of the secondary cyclone tubes.

[0037] The plurality of first-stage cyclone tubes are evenly arranged in the outer ring space between the upper and lower partitions along the circumferential direction; the plurality of second-stage cyclone tubes are evenly arranged in the inner space between the upper and lower partitions along the circumferential direction.

[0038] The number of the first-stage cyclone tubes and the second-stage cyclone tubes can be determined according to specific conditions (such as processing volume, vacuum degree, etc.). For example, 8 first-stage cyclone tubes are provided and 6 second-stage cyclone tubes are provided.

[0039] The primary and secondary cyclone tubes of the utility model adopt the cyclone separation tube structure of the prior art.

[0040] Through the recovery device of the utility model, after flash evaporation and two-stage cyclone separation, isopropanol can be recovered to the maximum extent, with a recovery rate of 80-85%, and 100% of the droplets of 8μm and above carried in the isopropanol are removed, and POP products are recovered to the maximum extent. The recovery device of the utility model occupies a small space, does not need to set up multiple tanks, and improves the gas-liquid separation effect by improving the internal parts of the cyclone separator.

[0041] The structure and effect of the isopropyl alcohol recovery device in the POP preparation process of the present invention are further described below in conjunction with the accompanying drawings of the specification.

[0042] Reference Figure 1As shown, the recovery device of isopropyl alcohol in the POP preparation process includes: a flash tank 1 and a cyclone separator 2. The side wall of the flash tank 1 is provided with an air inlet, the top of the flash tank 1 is provided with an air outlet and a liquid inlet, and the bottom of the flash tank 1 is provided with a discharge port. The air outlet of the flash tank 1 is connected to the cyclone separator 2, and the liquid outlet of the cyclone separator 2 is connected to the liquid inlet at the top of the flash tank 1. The gas discharged from the air outlet of the cyclone separator 2 is cooled by the condenser 3, and the condensed isopropyl alcohol is discharged to the isopropyl alcohol storage tank after passing through the buffer tank 4 under the action of the buffer tank delivery pump. A heating layer is provided outside the flash tank 1, for example, low-pressure steam is introduced to keep the temperature in the flash tank 1 within a certain range.

[0043] In the embodiment, a cyclone separator is structured as shown in the attached Figure 2 and 3 As shown. The shell 28 of the cyclone separator 2 is provided with separation internals, and the shell 28 is a cylindrical structure with a circular cross section. The separation internals include an upper partition 29 and a lower partition 20, which are respectively fixed in the shell 28 for fixing the cyclone tubes. The lower ends of the primary cyclone tube 24 and the secondary cyclone tube 25 are fixed on the lower partition 20, and the primary and secondary cyclone tubes are basically kept vertical to the upper and lower partition shells.

[0044] A horizontal partition 26 and an isolation tube 27 are arranged in the shell 28. The horizontal partition 26 is substantially in the shape of a ring. The horizontal partition 26 is substantially parallel to the upper and lower partitions and is located between the upper and lower partitions, separating the separation internals into two upper and lower spaces along the extension direction of the cyclone tube. The outer ring of the horizontal isolation plate 26 is in sealing contact or sealing connection with the inner wall of the shell 28.

[0045] An isolation tube 27 is provided in the shell 28. The isolation tube 27 is arranged along the extension direction of the cyclone tube, that is, the isolation tube 27 is arranged substantially parallel to the primary and secondary cyclone tubes. The lower end of the isolation tube 27 is fixed to the lower partition. The outer diameter of the isolation tube 27 at a certain height is equal to the diameter of the inner ring of the horizontal partition 26, and the isolation tube 27 can be sealed and connected to the inner circumferential wall of the horizontal partition 26 at a certain height. The setting of the isolation tube 27 can separate the separation internal parts into an inner ring part and an outer ring part in the plane direction of the upper and lower partitions. Figure 2 As shown, the space enclosed by the outer circumferential wall of the isolation tube 27, the inner circumferential wall of the shell 28, the lower surface of the horizontal isolation plate 26 and the surface of the lower partition plate 20 constitutes the outer annular space of the separation internal component, and the space enclosed by the inner circumferential wall of the isolation tube 27 is the internal space of the separation internal component.

[0046] The peripheral wall of the isolation tube 27 between the horizontal isolation plate 26 and the upper isolation plate 29 is provided with a plurality of through holes. Alternatively, the isolation tube 27 is a two-end tube, the upper end of the upper isolation tube is fixed on the upper isolation plate; the lower isolation tube is connected to the horizontal isolation plate 26 at a certain height, and the lower end of the lower isolation plate is fixed on the lower isolation plate; there is a certain gap between the lower end of the upper isolation tube and the upper end of the lower isolation tube. In this arrangement, the internal space of the separation inner part is connected to the outer annular space, and the fluid can flow in the two spaces through the through holes or gaps.

[0047] Reference Figure 3 The primary cyclone tube 24 is evenly arranged in the outer annular space of the separation inner part along the circumferential direction of the horizontal partition 26 of the shell, and the secondary cyclone tube 25 is evenly arranged in the inner space of the separation inner part along the circumferential direction of the horizontal partition 26 of the shell. The upper end of the primary cyclone tube 24 is located at or above the upper surface of the horizontal partition 26, and the upper end of the secondary cyclone tube 25 is located at or above the upper surface of the upper partition 29.

[0048] An air inlet 21 is provided on the peripheral wall of the housing 28, a liquid outlet 23 is provided at the bottom of the housing 28, and an air outlet 22 is provided at the top. The air inlet 21 faces the separation internal part.

[0049] The polymer polyol containing isopropyl alcohol is introduced into the flash tank 1, and the gas and liquid are initially separated at a certain temperature. The gas flows through the gas outlet to the gas inlet 21 of the cyclone separator 2, and the liquid flows out through the bottom of the flash tank. In the cyclone separator 2, the gas first enters the outer annular space of the separation internal component for a gas-liquid separation, and the gas enters the space between the upper partition and the horizontal partition through the upper end of the primary cyclone tube, and then flows into the internal space of the separation internal component through the through hole or gap of the isolation tube 27 for secondary gas-liquid separation. The gas (gaseous isopropyl alcohol) separated in the internal space of the separation internal component is discharged through the gas outlet on the shell 28. The liquid (POP product) flows into the flash tank 1 through the bottom liquid outlet 23 of the cyclone separator 2, and the gas-liquid separation is performed again.

[0050] Example 1-3 uses attached Figure 1 The isopropyl alcohol is recovered by a recovery device and a two-stage separation cyclone separator.

[0051] Example 1

[0052] The crude polymerization product containing isopropanol is sent to the flash tank at a temperature of 125°C. A jacketed pipe is set outside the flash tank. The operating temperature is maintained at 125°C using 0.5MPaG low-pressure steam. After flashing under vacuum conditions of 20kPaA, the liquid phase is mainly a POP polymerization product containing unreacted monomers. The liquid phase is transported to downstream equipment by controlling the liquid level of the flash tank; the gas phase is mainly composed of isopropanol and contains a small amount of POP product droplets. The gas phase component is sent to a cyclone gas-liquid separator. Under the action of the centrifugal force of the cyclone, the POP droplets gather and settle back to the flash tank. The gas phase at the top is sent to the shell side of the shell-and-tube condenser. The tube side uses 0°C chilled water as a cold source to cool the gas phase containing isopropanol from 125°C to 15°C. The isopropanol is condensed and recovered to the isopropanol buffer tank, and the non-condensable gas is sent to the exhaust gas treatment device. A vacuum pipe port is set on the shell side of the condenser, and the system operating pressure is maintained at 20kPaA by the vacuum device. The isopropanol recovery rate was found to be 82.7%, and no POP products were detected in the recovered isopropanol.

[0053] Example 2

[0054] The crude polymerization product containing isopropanol is sent to the flash tank at a temperature of 130°C. A jacketed pipe is set outside the flash tank. The operating temperature is maintained at 130°C using 0.5MPaG low-pressure steam. After flashing under vacuum conditions of 20kPaA, the liquid phase is mainly a POP polymerization product containing unreacted monomers. The liquid phase is transported to downstream equipment by controlling the liquid level of the flash tank; the gas phase is mainly composed of isopropanol and contains a small amount of POP product droplets. The gas phase component is sent to a cyclone gas-liquid separator. Under the action of the centrifugal force of the cyclone, the POP droplets gather and settle back to the flash tank. The gas phase at the top is sent to the shell side of the shell and tube condenser. The tube side uses 0°C chilled water as a cold source to cool the gas phase containing isopropanol from 130°C to 15°C. The isopropanol is condensed and recovered to the isopropanol buffer tank, and the non-condensable gas is sent to the exhaust gas treatment device. A vacuum pipe port is set on the shell side of the condenser, and the system operating pressure is maintained at 20kPaA by the vacuum device. The isopropanol recovery rate was found to be 83.1%, and no POP products were detected in the recovered isopropanol.

[0055] Example 3

[0056] The crude polymerization product containing isopropanol is sent to the flash tank at a temperature of 125°C. A jacketed pipe is set outside the flash tank. The operating temperature is maintained at 125°C using 0.5MPaG low-pressure steam. After flashing under vacuum conditions of 25kPaA, the liquid phase is mainly a POP polymerization product containing unreacted monomers. The liquid phase is transported to downstream equipment by controlling the liquid level of the flash tank. The main component of the gas phase is isopropanol and contains a small amount of POP product droplets. The gas phase component is sent to a cyclone gas-liquid separator. Under the action of the centrifugal force of the cyclone, the POP droplets gather and settle back to the flash tank. The gas phase at the top is sent to the shell side of the shell-and-tube condenser. The tube side uses 0°C chilled water as a cold source to cool the gas phase containing isopropanol from 125°C to 15°C. The isopropanol is condensed and recovered to the isopropanol buffer tank, and the non-condensable gas is sent to the exhaust gas treatment device. A vacuum pipe port is set on the shell side of the condenser, and the system operating pressure is maintained at 25kPaA by the vacuum device. The isopropanol recovery rate was found to be 81.2%, and no POP products were detected in the recovered isopropanol.

[0057] The above description is only a preferred embodiment of the present invention and is not intended to limit the scope of the substantial technical content of the present invention. The substantial technical content of the present invention is broadly defined in the scope of the claims of the application. Any technical entity or method completed by others, if it is exactly the same as that defined in the scope of the claims of the application or an equivalent variation, will be deemed to be included in the scope of the claims.

Claims

1. A device for recovering isopropanol in a POP preparation process, characterized in that: It includes a flash tank and a cyclone separator. The upper opening of the flash tank is connected to the air inlet of the cyclone separator. The air outlet of the cyclone separator is connected to a condenser, so that the material discharged from the air outlet of the cyclone separator is cooled.

2. The recovery device according to claim 1, characterized in that: The cyclone separator comprises a shell and a separation internal part arranged in the shell, the separation internal part comprises a primary cyclone tube, a secondary cyclone tube and an isolation tube, the isolation tube divides the space where the separation internal part is located into an inner space and an outer ring space in a first direction of the shell, the primary cyclone tube is located in the outer ring space, the secondary cyclone tube is located in the inner space, a horizontal partition is arranged in a second direction in the shell, the horizontal partition is respectively connected to the inner wall of the shell and the outer wall of the isolation tube, and divides the outer ring space where the separation internal part is located into an upper and a lower partition; The angle formed by the intersection of the first direction and the second direction is in the range of 60-90°.

3. The recovery device according to claim 2, characterized in that: The isolation tube is a tubular structure, the cross section of the shell is circular, and the isolation tube and the shell are concentrically arranged.

4. The recovery device according to claim 2, characterized in that: The separation internals include an upper baffle and a lower baffle fixed in the shell, the upper baffle and the lower baffle are used to fix the first-stage cyclone tube and the second-stage cyclone tube, and the two ends of the isolation tube are respectively fixed on the lower baffle and the upper baffle.

5. The recovery device according to any one of claims 2 to 4, characterized in that: A through hole is provided on the wall of the isolation tube to connect the outer annular space and the inner space where the separation internal component is located; Alternatively, continuous openings are provided in the circumferential direction within a certain height range of the isolation tube.

6. The recovery device according to any one of claims 2 to 4, characterized in that: The isolation tube is divided into an upper isolation tube and a lower isolation tube, and a gap is provided between the upper isolation tube and the lower isolation tube.

7. The recovery device according to any one of claims 2 to 4, characterized in that: The separation internals include an upper partition and a lower partition fixed in the shell, the upper partition and the lower partition are used to fix the first-stage cyclone tube and the second-stage cyclone tube, the lower end of the isolation tube is fixed to the lower partition, and the upper end of the isolation tube has a gap with the upper partition.

8. The recovery device according to any one of claims 2 to 4, characterized in that: The horizontal partition is located between the upper partition and the lower partition; the upper surface of the horizontal partition is lower than the upper end of the first-stage cyclone tube; The upper end of the secondary cyclone tube passes through the upper partition.

9. The recovery device according to claim 5, characterized in that: The through hole or opening on the isolation tube is located in the space between the horizontal partition and the upper partition.

10. The recovery device according to any one of claims 2 to 4, characterized in that: There are multiple primary cyclone tubes and multiple secondary cyclone tubes; the number of the primary cyclone tubes is greater than the number of the secondary cyclone tubes.

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