Vacuum rectification system with powder catcher

Abstract

The invention relates to a vacuum rectification system with a powder catcher. The vacuum rectification system comprises a rectification tower, a tower top gas phase condenser, a tail gas cooler, a vacuum buffer tank and a vacuum pump which are sequentially communicated in a gas phase mode, the vacuum buffer tank comprises a powder catcher, the filtering aperture of the powder catcher is 0.2-60 micrometers, and the porosity of the powder catcher is 15-40%. The vacuum rectification system has the advantages that solid powder is prevented from entering the vacuum pump in high-freezing-point substance system rectification, and the vacuum pump is prevented from being blocked.

Description

Technical Field

[0001] The present invention relates to the technical field of vacuum distillation, and more particularly to a vacuum distillation system with a powder collector. Background Art

[0002] The vacuum system of a vacuum distillation unit consists of a distillation column, condenser, reflux tank, off-gas cooler, vacuum buffer tank, and vacuum pump. The vacuum buffer tank is a crucial component of the vacuum system, playing a crucial role in ensuring its stability and protecting the vacuum pump. During the distillation process, overhead vapor is condensed into liquid in the condenser, while non-condensable gases are further cooled in the off-gas cooler before being pumped out of the distillation unit by a vacuum pump. Due to the high condenser temperature, the non-condensable gases in the vacuum distillation of high-freezing-point substances inevitably contain some high-freezing-point components. As the non-condensable gases flow along the gas phase pipeline toward the vacuum pump, they sublime and precipitate upon encountering low temperatures. This precipitated solid powder adheres to the inner walls of the off-gas cooler, pipelines, and vacuum buffer tank, with some floating in the non-condensable gases. This accumulation can lead to blockages in equipment and pipelines. In severe cases, these solids can enter the vacuum system, damaging the vacuum pump and compromising the stable operation of the distillation unit. Therefore, for vacuum distillation of high-freezing-point substances, it is crucial that the vacuum system efficiently capture these high-freezing-point components in the non-condensable gases.

[0003] CN214436608U discloses a blockage-resistant vacuum buffer tank. During the vacuum distillation process, this device effectively prevents blockage of the vacuum system caused by high-melting-point material vapor passing through the overhead cooler and entering the vacuum pipeline, where it cools and crystallizes, thereby ensuring smooth vacuum distillation operation. This utility model patent employs the addition of a solvent to the vacuum buffer tank to dissolve and absorb the high-melting-point components in the condensed gas, preventing them from entering the vacuum pump system. However, the addition of a solvent involves the subsequent recovery and disposal of the solvent containing the high-melting-point material, increasing the complexity of the process. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a vacuum distillation system which can effectively prevent powder in tail gas from entering a vacuum pump.

[0005] Specifically, the present invention relates to the following aspects.

[0006] 1. A vacuum distillation system comprising a distillation tower, a tower top gas phase condenser, a tail gas cooler, a vacuum buffer tank and a vacuum pump connected in sequence, wherein the vacuum buffer tank comprises a powder collector (preferably a hollow porous tube), and the filter pore size of the powder collector is 0.2-60 μm (preferably 10-30 μm) and the porosity is 15-40% (preferably 20-30%).

[0007] 2. The vacuum distillation system according to any of the preceding or following aspects, wherein the distillation tower is configured to distill a high-freezing-point substance or a mixture containing a high-freezing-point substance (e.g., at least one selected from long-chain diamines, preferably at least one selected from decanediamine, dodecanediamine, tridecanediamine, and tetradecanediamine).

[0008] 3. The vacuum distillation system according to any one of the preceding or following aspects, wherein the vacuum buffer tank is configured to receive non-condensable gas from the tail gas cooler and separate solid powder from the non-condensable gas through the powder collector.

[0009] 4. The vacuum distillation system according to any one of the preceding or following aspects, wherein the temperature of the non-condensable gas is 0-50°C (preferably 20-30°C), and the solid content of the non-condensable gas is 0.01-0.1 g / m 3 (Preferably 0.01-0.03g / m 3 ).

[0010] 5. The vacuum distillation system according to any one of the preceding or following aspects, wherein the operating conditions of the vacuum buffer tank include: pressure drop of 0.1-2 kPa and temperature of 0-50°C.

[0011] 6. The vacuum distillation system described in any of the preceding or following aspects, wherein the vacuum buffer tank includes an inner cavity, a support plate that divides the inner cavity into an upper gas collecting chamber and a lower gas inlet chamber, and the powder collector arranged on the support plate, one end of the powder collector is located in the gas collecting chamber, and the other end is located in the gas inlet chamber.

[0012] 7. The vacuum distillation system according to any one of the preceding or following aspects, wherein the volume ratio of the gas collecting chamber to the gas inlet chamber is 1:5-1:30 (preferably 1:10-1:20).

[0013] 8. The vacuum distillation system according to any of the preceding or following aspects, wherein the hollow porous tube is one or more (e.g., 1-100) and the arrangement density of the plurality of hollow porous tubes on the support plate is 1-9 tubes / m 2 Support plate (preferably 3-6 / m 2 support plate).

[0014] 9. The vacuum distillation system according to any of the preceding or following aspects, wherein the number of the hollow porous tubes is one or more (e.g., 1-100), the multiple hollow porous tubes are arranged in a square or triangle on the support plate, and the distance between two adjacent hollow porous tubes is 100-500 mm (preferably 200-300 mm).

[0015] 10. The vacuum distillation system according to any one of the preceding or following aspects, wherein the hollow porous tube has a length of 500-2000 mm (preferably 1000-1500 mm) and an outer diameter of 40-100 mm.

[0016] Technical Effects

[0017] According to the present invention, solid powder in the non-condensable gas is completely captured to prevent the solid powder from entering the vacuum pump, thereby extending the service life of the vacuum pump and ensuring the stable operation of the vacuum distillation device.

[0018] According to the present invention, the solid powder filtered by the buffer tank can also be conveniently recovered.

[0019] According to the present invention, the operation cycle of the collector can be extended and the number of backflushing operations can be reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Schematic diagram of a vacuum distillation system with a powder collector.

[0021] In the figure, 1 is a distillation tower, 2 is the first gas phase condenser, 3 is the first gas phase condenser, 7 is a reflux tank, 4 is a tail gas cooler, 5 is a vacuum buffer tank, and 6 is a vacuum pump.

[0022] Figure 2 Schematic diagram of a vacuum buffer tank with a powder collector.

[0023] In the figure, 51 is the head, 52 is the support plate, 53 is the cylinder wall, and 54 is the collector.

[0024] Figure 3 A top view of the powder collector. DETAILED DESCRIPTION

[0025] The specific embodiments of the present invention are described in detail below. However, it should be noted that the protection scope of the present invention is not limited by these specific embodiments, but is determined by the claims in the appendix.

[0026] All publications, patent applications, patents, and other references mentioned in this specification are incorporated herein by reference. Unless otherwise defined, all technical and scientific terms used in this specification have the meanings commonly understood by those skilled in the art. In the event of conflict, the definitions in this specification will prevail.

[0027] When this specification uses the prefix "well known to those skilled in the art", "prior art" or similar terms to introduce materials, substances, methods, steps, devices or components, the objects introduced by the prefix include those commonly used in the art when this application is filed, but also include those that are not commonly used at present but will become generally recognized in the art to be suitable for similar purposes.

[0028] In the context of this specification, by substantially it is meant that the deviation does not exceed 5%, preferably does not exceed 2% or 1%.

[0029] In the context of this specification, the so-called high freezing point refers to a freezing point temperature of 50° C. or above under normal pressure.

[0030] Unless otherwise specified, all percentages, parts, ratios, etc. mentioned in this specification are based on weight and pressure is absolute pressure.

[0031] In the context of this specification, if there are no specific operating conditions and additives, those known in the art are directly applicable without particular limitation.

[0032] In the context of this specification, any two or more embodiments of the present invention may be arbitrarily combined, and the technical solutions thus formed belong to part of the original disclosure of this specification and also fall within the scope of protection of the present invention.

[0033] According to one embodiment of the present invention, a vacuum distillation system is provided, comprising a distillation tower, a tower top gas phase condenser, a tail gas cooler, a vacuum buffer tank and a vacuum pump, which are sequentially gas-phase connected.

[0034] According to the present invention, the vacuum buffer tank includes a powder collector. Preferably, the powder collector has a filter pore size of 0.2-60 μm (preferably 10-30 μm) and a porosity of 15-40% (preferably 20-30%). A smaller pore size or porosity requires greater pumping power, which is more likely to cause pore blockage and increase recoil frequency. A larger pore size or porosity results in poor retention, making it easier for powder to enter the vacuum pump, shortening its service life.

[0035] According to one embodiment of the present invention, a distillation column is configured to distill a high-freezing-point substance or a mixture containing a high-freezing-point substance to obtain a gas phase at the top of the column and a liquid phase at the bottom of the column. The high-freezing-point substance may be, for example, at least one selected from long-chain diamines, preferably at least one selected from decanediamine, dodecanediamine, tridecanediamine, and tetradecanediamine.

[0036] According to one embodiment of the present invention, the operating conditions of the distillation tower include: tower top pressure 0.1-20 kPa, tower top temperature 100-220° C., and reflux ratio 1:50-50:1.

[0037] According to one embodiment of the present invention, the tower top gas phase condenser includes a tower top first gas phase condenser and a tower top second gas phase condenser. The tower top first gas phase condenser condenses the tower top gas phase from the rectifying tower to obtain a condenser liquid phase and a gas phase, and the tower top second gas phase condenser condenses the gas phase from the tower top first gas phase condenser to obtain a condenser liquid phase and tail gas.

[0038] According to one embodiment of the present invention, the first gas phase condenser at the top of the tower is a horizontal fixed tube sheet heat exchanger.

[0039] According to one embodiment of the present invention, the operating conditions of the first gas-phase condenser at the top of the tower include: a pressure drop of 0.01-5 kPa and a temperature of 100-220°C.

[0040] According to one embodiment of the present invention, the second gas-phase condenser at the top of the tower is a horizontal fixed tube sheet heat exchanger.

[0041] According to one embodiment of the present invention, the operating conditions of the second vapor phase condenser at the top of the tower include: a pressure drop of 0.01-2 kPa and a temperature of 100-220°C.

[0042] According to one embodiment of the present invention, the reflux tank is configured to reflux part of the liquid from the first gas-phase condenser and the second gas-phase condenser at the top of the tower into the distillation tower, and extract part of the liquid as the product.

[0043] According to one embodiment of the present invention, the operating conditions of the reflux drum include: a temperature of 100-220°C.

[0044] According to one embodiment of the present invention, the tail gas cooler cools the tail gas from the second gas phase condenser at the top of the tower to obtain a cooler solid phase and non-condensable gas.

[0045] According to one embodiment of the present invention, the temperature of the non-condensable gas is 0-50°C (preferably 20-30°C).

[0046] According to one embodiment of the present invention, the solid content of the non-condensable gas is 0.01-0.1 g / m 3 (Preferably 0.01-0.03g / m 3 The inventors of the present invention have discovered that when the solid content of the non-condensable gas is too high, the operating cycle of the collector is significantly shortened.

[0047] According to one embodiment of the present invention, the operating conditions of the exhaust gas cooler include: pressure drop of 0.01-1 kPa, and temperature of 0-50°C.

[0048] According to one embodiment of the present invention, the inner diameter of the heat exchange tube of the exhaust gas cooler is 40-100 mm.

[0049] According to one embodiment of the present invention, the vacuum buffer tank receives the non-condensable gas from the exhaust gas cooler, and its operating conditions include: pressure drop 0.01-2 kPa, temperature 0-50°C.

[0050] According to one embodiment of the present invention, the vacuum buffer tank includes an inner cavity, a support plate that divides the inner cavity into an air collecting chamber located at the upper part and an air inlet chamber located at the lower part, and the powder collector arranged on the support plate, one end of the powder collector is located in the air collecting chamber, and the other end is located in the air inlet chamber.

[0051] According to one embodiment of the present invention, the volume ratio of the gas collecting chamber to the gas inlet chamber is 1:5-1:30 (preferably 1:10-1:20). If the volume ratio is too small, the gas inlet chamber may be easily blocked. If the volume ratio is too large, the gas flow rate may be too low, the gas collection effect may be reduced, and the service life of the vacuum pump may be shortened.

[0052] According to one embodiment of the present invention, a non-condensable gas inlet is provided on the side of the air inlet chamber, a material outlet is provided at the bottom of the air inlet chamber, and the air inlet chamber and the air collecting chamber are connected in gas communication via a powder collector.

[0053] According to one embodiment of the present invention, the non-condensable gas enters the air inlet chamber tangentially from the non-condensable gas inlet, wherein the angle between the central axis of the non-condensable gas inlet and the horizontal direction is 0-60 degrees.

[0054] According to one embodiment of the present invention, the angle between the central axis of the non-condensable gas inlet and the horizontal direction is 10-30°.

[0055] According to one embodiment of the present invention, the powder collector is provided with a backflush line.

[0056] According to one embodiment of the present invention, the powder collector is closed at an end on the air inlet chamber side and is open at an end on the air collecting chamber side.

[0057] According to one embodiment of the present invention, the powder collector is a hollow porous tube, in particular a ceramic hollow porous tube, such as a silicon carbide hollow porous tube. In addition, the hollow porous tube can be one or more, such as 1-100.

[0058] According to one embodiment of the present invention, the plurality of hollow porous tubes are arranged on the support plate in an arbitrary pattern (preferably a square or a triangle), and the distance between two adjacent hollow porous tubes is 100-500 mm (preferably 200-300 mm).

[0059] According to one embodiment of the present invention, the arrangement density of the plurality of hollow porous tubes on the support plate is 1-9 tubes / m 2 Support plate (preferably 3-6 / m 2When the density is too low, the collector's operating cycle is significantly reduced.

[0060] According to one embodiment of the present invention, the length of the hollow porous tube is 500-2000 mm (preferably 1000-1500 mm) and the outer diameter is 40-100 mm.

[0061] The present invention will be further described in detail below with reference to the accompanying drawings, but the present invention is not limited to these drawings.

[0062] like Figure 1 、 Figure 2 As shown, a vacuum distillation system with a powder collector comprises a distillation tower 1, a first gas phase condenser 2 at the top of the tower, a reflux tank 7, a second gas phase condenser 3 at the top of the tower, an exhaust gas cooler 4, a vacuum buffer tank 5, and a vacuum pump 6, which are sequentially gas-connected. The vacuum buffer tank 5 includes a powder collector.

[0063] The high freezing point material is vacuum distilled in the distillation tower 1, and the top steam is connected to the first gas phase condenser 2 at the top of the tower through a pipeline.

[0064] The first gas phase condenser 2 at the top of the tower is a horizontal fixed tube plate heat exchanger. The steam from the top of the distillation tower enters the shell side of the first gas phase condenser, and the heat transfer oil serves as the refrigerant and enters the tube side.

[0065] The second gas phase condenser 3 at the top of the tower is a horizontal fixed tube plate heat exchanger. The gas phase at the outlet of the first gas phase condenser 2 enters the shell side of the second gas phase condenser 3, and the heat transfer oil serves as the refrigerant and enters the tube side.

[0066] The shell-side liquid phase from the first and second vapor condensers 2 and 3 at the top of the tower enters the reflux tank 7, where part of it flows back to the distillation tower and part of it is extracted as product. The tail gas from the shell-side gas outlet of the second vapor condenser 3 is connected to the tail gas inlet of the tail gas cooler via a pipeline.

[0067] In exhaust cooler 4, exhaust gas is continuously cooled through jacketed heat exchanger 45 and shell-and-tube heat exchanger 46, with circulating cooling water or low-pressure steam as the heat exchange medium. High-freezing-point components are cooled to a solid phase and deposited on the inner surfaces of jacketed heat exchanger 45 and shell-and-tube heat exchanger 46. Non-condensable gas is connected to vacuum buffer tank 5 through the outlet of the exhaust cooler. Non-condensable gas containing high-freezing-point solid components enters vacuum buffer tank 5 tangentially through a feed pipe, inlet 55, where it is filtered by powder trap 54, trapping the powder. Pure non-condensable gas is connected to the vacuum pump through vacuum buffer tank outlet 57 and finally discharged from the vacuum system through the vacuum pump. 58 is the backflush nitrogen port.

[0068] Example

[0069] The present invention is further described in detail below with reference to examples, but the present invention is not limited to these examples.

[0070] Example 1

[0071] Distillation of Dodecanediamine High Freezing Point System

[0072] In this embodiment, the high freezing point component is dodecanediamine, which has a freezing point of 67-69°C. The specific components are 1% laurylamine, 0.5% decanediamine, 96% dodecanediamine, 1% N-ethyldodecanediamine, and 1.5% other heavy components. Rectification is performed using the aforementioned vacuum distillation system with a powder filter, using a rotary vane vacuum pump.

[0073] The specific operating conditions are as follows:

[0074] The tower top pressure is 2 kPa, the tower top temperature is 190 ° C, and the reflux ratio is 1:5.

[0075] The first gas phase condenser at the top of the tower is a horizontal fixed tube sheet heat exchanger with an operating condition of a pressure drop of 0.5 kPa and a temperature of 180°C.

[0076] The second gas phase condenser at the top of the tower is a horizontal fixed tube sheet heat exchanger with an operating condition of pressure drop of 0.02 kPa and temperature of 150 °C.

[0077] The reflux tank temperature is 170°C.

[0078] The inner diameter of the exhaust gas cooler heat exchange tube is 40mm, and the operating conditions are: pressure drop 0.1kPa, temperature 50℃.

[0079] The operating conditions of the vacuum buffer tank are: pressure drop 0.1 kPa, temperature 50°C.

[0080] The non-condensable gas enters the air inlet chamber along a tangential direction from the non-condensable gas inlet, and the angle between the central axis direction of the non-condensable gas inlet and the horizontal direction is 30°.

[0081] The powder collector includes three silicon carbide hollow porous tubes.

[0082] The filtration pore size of the hollow porous tube is 10 μm.

[0083] The hollow porous tubes are arranged in a triangle on the support plate, and the distance between two adjacent porous tubes is 100 mm.

[0084] The hollow porous tube has a length of 1000 mm, an outer diameter of 40 mm, and a porosity of 40%.

[0085] The arrangement density of the hollow porous tubes on the support plate is 3 tubes / m 2 Support plate.

[0086] The volume ratio of the air collecting chamber to the air inlet chamber is 1:10.

[0087] The non-condensable gas has a temperature of 25°C and a solid content of 0.01 g / m 3 .

[0088] After 26 days of operation, the top vacuum of the distillation tower dropped, and the distillation system was stopped. The collector needed to be backflushed to release the vacuum pump oil. The vacuum pump oil was clear and transparent.

[0089] Example 2

[0090] Distillation of Decanediamine High Freezing Point System

[0091] In this embodiment, the high freezing point component is decanediamine, which has a freezing point of 62°C. The specific components are 2% decylamine, 0.5% octanediamine, 95% decanediamine, 1% N-ethyldecanediamine, and 1.5% other heavy components. Rectification is performed using the aforementioned vacuum distillation system with a powder filter, using a rotary vane vacuum pump.

[0092] Decanediamine is vacuum distilled in a distillation tower. The specific operating conditions are as follows:

[0093] The tower top pressure is 3 kPa, the tower top temperature is 170 ° C, and the reflux ratio is 1:10.

[0094] The first gas phase condenser at the top of the tower is a horizontal fixed tube sheet heat exchanger, and the operating conditions are a pressure drop of 0.2 kPa and a temperature of 160 °C.

[0095] The second gas phase condenser at the top of the tower is a horizontal fixed tube sheet heat exchanger with an operating condition of pressure drop of 0.02 kPa and temperature of 120 °C.

[0096] The reflux tank temperature is 140°C.

[0097] The inner diameter of the exhaust gas cooler heat exchange tube is 50mm, and the operating conditions are: pressure drop 0.2kPa, temperature 60℃.

[0098] The operating conditions of the vacuum buffer tank are: pressure drop 0.5 kPa, temperature 60 °C.

[0099] The non-condensable gas enters the air inlet chamber along a tangential direction from the non-condensable gas inlet, and the angle between the central axis direction of the non-condensable gas inlet and the horizontal direction is 30°.

[0100] The powder collector includes four silicon carbide hollow porous tubes.

[0101] The filtration pore size of the hollow porous tube is 30 μm.

[0102] The hollow porous tubes are arranged in a square on the support plate, and the distance between two adjacent porous tubes is 500 mm.

[0103] The hollow porous tube has a length of 1500 mm, an outer diameter of 100 mm, and a porosity of 40%.

[0104] The arrangement density of the hollow porous tubes on the support plate is 4 tubes / m 2 Support plate.

[0105] The volume ratio of the air collecting chamber to the air inlet chamber is 1:20.

[0106] The non-condensable gas has a temperature of 35°C and a solid content of 0.02 g / m 3 .

[0107] After 15 days of operation, the top vacuum of the distillation tower dropped, and the distillation system was stopped. The collector needed to be backflushed to release the vacuum pump oil. The vacuum pump oil was clear and transparent.

[0108] Example 3

[0109] Distillation of tridecanediamine high freezing point system

[0110] In this embodiment, the high freezing point component is tridecanediamine, which has a freezing point of 51°C. The specific composition is 1% tridecanediamine, 0.5% dodecanediamine, 96% tridecanediamine, 1% N-ethyltridecanediamine, and 1.5% other heavy components. Rectification is performed using the aforementioned vacuum distillation system with a powder filter, using a rotary vane vacuum pump.

[0111] Tridecane diamine is vacuum distilled in a distillation tower. The specific operating conditions are as follows:

[0112] The tower top pressure is 3 kPa, the tower top temperature is 200°C, and the reflux ratio is 1:10.

[0113] The first gas phase condenser at the top of the tower is a horizontal fixed tube sheet heat exchanger with an operating condition of a pressure drop of 1 kPa and a temperature of 170°C.

[0114] The second gas phase condenser at the top of the tower is a horizontal fixed tube sheet heat exchanger with an operating condition of pressure drop of 0.05 kPa and temperature of 100 °C.

[0115] The reflux tank temperature is 130°C.

[0116] The inner diameter of the exhaust gas cooler heat exchange tube is 40mm, and the operating conditions are: pressure drop 0.1kPa, temperature 50℃.

[0117] The operating conditions of the vacuum buffer tank are: pressure drop 1kPa, temperature 50℃.

[0118] The non-condensable gas enters the air inlet chamber along a tangential direction from the non-condensable gas inlet, and the angle between the central axis direction of the non-condensable gas inlet and the horizontal direction is 30°.

[0119] The powder collector includes four silicon carbide hollow porous tubes.

[0120] The filtration pore size of the hollow porous tube is 20 μm.

[0121] The hollow porous tubes are arranged in a square on the support plate, and the distance between two adjacent porous tubes is 300 mm.

[0122] The hollow porous tube has a length of 1000 mm, an outer diameter of 40 mm, and a porosity of 15%.

[0123] The arrangement density of the hollow porous tubes on the support plate is 6 tubes / m 2 Support plate.

[0124] The volume ratio of the air collecting chamber to the air inlet chamber is 1:20.

[0125] The non-condensable gas has a temperature of 50°C and a solid content of 0.01 g / m 3 .

[0126] After 15 days of operation, the top vacuum of the distillation tower dropped, and the distillation system was stopped. The collector needed to be backflushed to release the vacuum pump oil. The vacuum pump oil was clear and transparent.

[0127] Example 4

[0128] The distillation of the dodecanediamine high freezing point system is the same as that in Example 1, except that the temperature of the non-condensable gas is 5°C.

[0129] After 20 days of operation, the top vacuum of the distillation tower dropped, and the distillation system was stopped. The collector needed to be backflushed to release the vacuum pump oil. The vacuum pump oil was clear and transparent.

[0130] Example 5

[0131] The distillation of the high freezing point system of dodecanediamine is the same as that in Example 1, except that the temperature of the non-condensable gas is 50°C.

[0132] After 21 days of operation, the top vacuum of the distillation tower dropped, and the distillation system was stopped. The collector needed to be backflushed to release the vacuum pump oil. The vacuum pump oil was clear and transparent.

[0133] Example 6

[0134] The distillation of the high freezing point system of dodecanediamine was the same as in Example 1, except that the solid content of the non-condensable gas was 0.1 g / m 3 .

[0135] After 17 days of operation, the top vacuum of the distillation tower dropped, and the distillation system was stopped. The collector needed to be backflushed to release the vacuum pump oil. The vacuum pump oil was clear and transparent.

[0136] Example 7

[0137] The distillation of the dodecanediamine high freezing point system is the same as that in Example 1, except that the volume ratio of the gas collecting chamber to the gas inlet chamber is 1:30.

[0138] After 17 days of operation, the top vacuum of the distillation tower dropped, and the distillation system was stopped. The collector needed to be backflushed to release the vacuum pump oil. The vacuum pump oil was clear and transparent.

[0139] Example 8

[0140] The distillation of the dodecanediamine high freezing point system is the same as that in Example 1, except that the volume ratio of the gas collecting chamber to the gas inlet chamber is 1:5.

[0141] After 18 days of operation, the top vacuum of the distillation tower dropped, and the distillation system was stopped. The collector needed to be backflushed to release the vacuum pump oil. The vacuum pump oil was clear and transparent.

[0142] Example 9

[0143] The distillation of the high freezing point system of dodecanediamine is the same as that of Example 1, except that the arrangement density of the hollow porous tubes on the support plate is 1 tube / m 2 Support plate.

[0144] After 15 days of operation, the top vacuum of the distillation tower dropped, and the distillation system was stopped. The collector needed to be backflushed to release the vacuum pump oil. The vacuum pump oil was clear and transparent.

[0145] Example 10

[0146] The distillation of the high freezing point system of dodecanediamine is the same as that of Example 1, except that the arrangement density of the hollow porous tubes on the support plate is 9 tubes / m 2 Support plate.

[0147] After 22 days of operation, the top vacuum of the distillation tower dropped, and the distillation system was stopped. The collector needed to be backflushed to release the vacuum pump oil. The vacuum pump oil was clear and transparent.

[0148] Comparative Example 1

[0149] The same as Example 1, the only difference is that no powder collector is provided.

[0150] After the distillation tower had been running for 7 days, the vacuum at the top of the tower dropped, so the distillation system was stopped and the vacuum pump oil was drained. The vacuum pump oil became turbid.

[0151] Comparative Example 2

[0152] The same as Example 1, the only difference is that the filtration pore size of the hollow porous tube is 0.1 μm.

[0153] After the distillation tower has been running for 3 days, the vacuum at the top of the tower drops, the distillation system is stopped, and the collector needs to be backflushed.

[0154] Comparative Example 3

[0155] The same as Example 1, the only difference is that the filtration pore size of the hollow porous tube is 70 μm.

[0156] After the distillation tower had been running for 4 days, the vacuum at the top of the tower dropped, so the distillation system was stopped and the vacuum pump oil was drained. The vacuum pump oil became turbid.

[0157] Comparative Example 4

[0158] The same as Example 1, except that the porosity of the hollow porous tube is 10%.

[0159] After the distillation tower has been running for 2 days, the vacuum at the top of the tower drops, the distillation system is stopped, and the collector needs to be backflushed.

[0160] Comparative Example 5

[0161] The same as Example 1, except that the porosity of the hollow porous tube is 45%.

[0162] After the distillation tower had been running for 4 days, the vacuum at the top of the tower dropped, so the distillation system was stopped and the vacuum pump oil was drained. The vacuum pump oil became turbid.

[0163] Comparative Example 6

[0164] The same as embodiment 1, the only difference is that no exhaust gas cooler is provided.

[0165] After the distillation tower had been running for 5 days, the vacuum at the top of the tower dropped, so the distillation system was stopped and the vacuum pump oil was drained. The vacuum pump oil became turbid.

Claims

1. A vacuum distillation system comprising a distillation tower, a tower top gas phase condenser, a tail gas cooler, a vacuum buffer tank and a vacuum pump connected in sequence, wherein the vacuum buffer tank comprises a powder collector (preferably a hollow porous tube), and the filter pore size of the powder collector is 0.2-60 μm (preferably 10-30 μm) and the porosity is 15-40% (preferably 20-30%).

2. The vacuum distillation system according to claim 1, wherein the distillation tower is configured to distill a high-freezing-point substance or a mixture containing a high-freezing-point substance (such as at least one selected from long-chain diamines, preferably at least one of decanediamine, dodecanediamine, tridecanediamine, and tetradecanediamine). 3 . The vacuum distillation system according to claim 1 , wherein the vacuum buffer tank is configured to receive non-condensable gas from the tail gas cooler and separate solid powder from the non-condensable gas through the powder collector.

4. The vacuum distillation system according to claim 3, wherein the temperature of the non-condensable gas is 0-50°C (preferably 20-30°C), and / or the solid content of the non-condensable gas is 0.01-0.1 g / m 3 (Preferably 0.01-0.03g / m 3 ).

5. The vacuum distillation system according to claim 1, wherein the operating conditions of the vacuum buffer tank include: Pressure drop 0.1-2kPa, temperature 0-50℃.

6. The vacuum distillation system of claim 1, wherein the vacuum buffer tank comprises an inner cavity, a support plate that divides the inner cavity into an upper gas collecting chamber and a lower gas inlet chamber, and the powder collector arranged on the support plate, one end of the powder collector being located in the gas collecting chamber and the other end being located in the gas inlet chamber.

7. The vacuum distillation system according to claim 6, wherein the volume ratio of the gas collecting chamber to the gas inlet chamber is 1:5-1:30 (preferably 1:10-1:20).

8. The vacuum distillation system according to claim 6, wherein the number of the hollow porous tubes is one or more (e.g., 1-100 tubes), and the arrangement density of the plurality of hollow porous tubes on the support plate is 1-9 tubes / m 2 Support plate (preferably 3-6 / m 2 support plate).

9. The vacuum distillation system according to claim 6, wherein the number of the hollow porous tubes is one or more (e.g., 1-100), the multiple hollow porous tubes are arranged in a square or triangle on the support plate, and the distance between two adjacent hollow porous tubes is 100-500 mm (preferably 200-300 mm).

10. The vacuum distillation system according to claim 1, wherein the hollow porous tube has a length of 500-2000 mm (preferably 1000-1500 mm) and an outer diameter of 40-100 mm.

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