System and method for recovering n-hexane solution from reaction solution

Abstract

The invention relates to the technical field of organic solvent recovery, in particular to a system and a method for recovering an n-hexane solution from a reaction solution. The normal hexane recovery system comprises a reaction unit, a first heat exchange unit, a second heat exchange unit, a condensation recovery device and a liquid storage unit which are sequentially communicated in the fluid flowing direction, the condensation recovery device comprises a tail gas outlet, the second heat exchange unit further comprises a second gas inlet and a second gas outlet, and the tail gas outlet is communicated with the second gas inlet through a pipeline; the reaction unit comprises a reaction gas inlet, and the second gas outlet is communicated with the reaction gas inlet through the return pipe. Gas generated from the reaction unit is subjected to heat exchange through the first heat exchange unit and the second heat exchange unit and then enters the condensation recovery device to be subjected to low-temperature condensation so as to provide n-hexane liquid phase stream and tail gas, the n-hexane liquid phase stream is filtered and then enters the liquid storage unit, and the tail gas flows back to the reaction unit.

Description

Technical Field

[0001] The invention relates to the technical field of organic solvent recovery, and in particular to a system and method for recovering a normal hexane solution from a reaction solution. Background Art

[0002] Magnetic beads are a kind of medium biological product used for biological genetic separation, purification and detection, especially in the separation, purification and detection of infectious diseases and genetic diseases. In the process of producing magnetic beads, n-hexane solution is used. Because n-hexane solution is volatile, the gas it produces is not only pungent, but also toxic, irritating, teratogenic and carcinogenic. Therefore, the generated gas must be properly handled. The environmental protection department requires that n-hexane gas must be condensed and recovered before being discharged into the atmosphere. Otherwise, direct incineration of n-hexane gas will not only cause harm to the environment, but also may explode due to contact between gas and air. The lower explosion limit is 1.1% and the upper explosion limit is 7.5%. Although n-hexane gas can be adsorbed by activated carbon, this method consumes a lot of activated carbon and increases costs. The current production process is to directly use activated carbon to adsorb n-hexane gas, which not only leads to the failure to recycle the n-hexane raw materials, wastes resources, but also fails to meet the new environmental protection requirements. Therefore, it is necessary to improve the existing process, recycle n-hexane, improve resource utilization, reduce the use of activated carbon, and thus reduce costs and environmental burdens. Summary of the invention

[0003] In view of the above-mentioned shortcomings of the prior art, the purpose of the present invention is to provide a system and method for recovering n-hexane solution from a reaction solution, so as to solve the problems in the prior art that n-hexane raw materials are not recycled, resulting in waste of resources; activated carbon adsorbs n-hexane, increasing production costs, and cannot meet environmental protection requirements, posing environmental hazards, etc.

[0004] To achieve the above-mentioned purpose and other related purposes, the first aspect of the present invention provides a n-hexane solution recovery system, comprising a reaction unit, a first heat exchange unit, a second heat exchange unit, a condensation recovery device and a liquid storage unit which are connected in sequence in the direction of fluid flow; the condensation recovery device comprises a tail gas outlet, the second heat exchange unit further comprises a second air inlet and a second air outlet, the tail gas outlet is connected to the second air inlet through a pipeline; and also comprises a reflux pipe, the reaction unit comprises a reaction air inlet, and the second air outlet is connected to the reaction air inlet through the reflux pipe.

[0005] In some embodiments of the present invention, the reaction unit includes one or more reactors with gas circulation; a first micro-pressure mechanical gauge is provided on the top of the reactor connected to the reflux pipe; a second micro-pressure mechanical gauge is provided on the top of the reactor close to the first heat exchange unit.

[0006] In some embodiments of the present invention, the reaction unit also includes a reaction outlet, the second heat exchange unit also includes a first air inlet, and a circulating fan is provided on the connecting pipeline between the reaction outlet and the first air inlet; a first valve body is also provided on the connecting pipeline between the circulating fan and the first air inlet.

[0007] In some embodiments of the present invention, a water collecting unit is further included. The water collecting unit includes a first liquid level sensor and a water seal safety valve connected in sequence along the liquid flow direction. The water collecting unit is connected to the liquid outlet of each guide tube through a pipeline.

[0008] In some embodiments of the present invention, a second valve body is respectively provided at a pipe connection between each of the heat exchange pipes and the air inlet and / or the air outlet of the guide cylinder.

[0009] In some embodiments of the present invention, the first heat exchange unit is a plate heat exchanger.

[0010] In some embodiments of the present invention, a first temperature gauge and a pipeline cold insulation layer are provided on the connecting pipeline between the second heat exchange unit and the condensation recovery device along the gas flow direction.

[0011] In some embodiments of the present invention, a liquid filter is further provided on the connecting pipe between the liquid storage unit and the condensation recovery device.

[0012] In some embodiments of the present invention, a second temperature gauge, a third valve body and an anemometer are provided on the connecting pipe between the exhaust gas outlet and the second air inlet along the fluid flow direction.

[0013] In some embodiments of the present invention, a third temperature gauge is further provided on the connecting pipeline between the exhaust gas outlet and the second air inlet.

[0014] In some embodiments of the present invention, the reflux pipe is provided with an oxygen measuring unit, a nitrogen pipeline and an air pressure monitoring device in sequence along the fluid flow direction.

[0015] In some embodiments of the present invention, a fourth valve body and a fifth valve body are sequentially provided on the connecting pipe between the oxygen measuring unit and the nitrogen pipeline along the fluid flow direction.

[0016] In some embodiments of the present invention, the nitrogen pipeline includes a nitrogen bottle, a pressure reducing valve, a gas throttle valve and a sixth valve body which are sequentially connected along the gas flow direction.

[0017] In some embodiments of the present invention, the air pressure monitoring device includes a U-shaped tube, the high-pressure side pipe of the U-shaped tube is connected to the return pipe through a pipe; the low-pressure side pipe of the U-shaped tube is provided with a second liquid level sensor, a third liquid level sensor and a fourth liquid level sensor in sequence along the liquid outflow direction.

[0018] In some embodiments of the present invention, a gas filter, a sixth valve body and a fourth temperature gauge are sequentially provided on the connecting pipe between the gas pressure monitoring device and the reaction gas inlet along the gas flow direction.

[0019] The second aspect of the present invention provides a method for recovering n-hexane solution from a reaction liquid, comprising the following steps: the gas generated from the reaction unit is subjected to heat exchange through a first heat exchange unit and a second heat exchange unit respectively, and then enters a condensation recovery device for low-temperature condensation to provide a n-hexane liquid phase stream and tail gas, the n-hexane liquid phase stream enters a liquid storage unit after filtration, and the tail gas is refluxed to the reaction unit.

[0020] As described above, the system and method for recovering n-hexane solution from a reaction solution of the present invention have the following beneficial effects:

[0021] The invention has a simple structure and is easy to operate. It can efficiently recycle waste organic solvent n-hexane solution. The recovery rate increases with the extension of system operation time, and it is converted into reusable finished raw materials, saving costs and generating economic value. Compared with traditional processes, it meets the latest environmental protection requirements, effectively reduces the risk of environmental pollution, and can achieve both economic and environmental benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Shown is an overall schematic diagram of a n-hexane recovery system disclosed in an embodiment of the present invention.

[0023] Description of Figure Numbers

[0024] 1 Reaction unit

[0025] 101 Reaction air inlet

[0026] 102 reaction outlet

[0027] 103 The first micro-pressure mechanical meter

[0028] 104 Second Micro-pressure Mechanical Watch

[0029] 2. The first heat exchange unit

[0030] 21 First air inlet

[0031] 22 First air outlet

[0032] 23 Second air inlet

[0033] 24 Second air outlet

[0034] 3. Second heat exchange unit

[0035] 31. Guide tube

[0036] 311 liquid outlet

[0037] 32 Heat exchange pipe

[0038] 4 Condensate recovery device

[0039] 41 Exhaust gas outlet

[0040] 5 Return pipe

[0041] 51 Oxygen measurement unit

[0042] 52 Nitrogen pipeline

[0043] 521 Nitrogen Bottle

[0044] 522 Pressure reducing valve

[0045] 523 Gas Throttle Valve

[0046] 524 Sixth valve body

[0047] 53 Fifth valve body

[0048] 54 Air pressure monitoring device

[0049] 540 U-tube

[0050] 541 Second liquid level sensor

[0051] 542 Third liquid level sensor

[0052] 543 Fourth liquid level sensor

[0053] 55 Gas filter

[0054] 56 Seventh valve body

[0055] 57 Fourth Thermometer

[0056] 6 Circulation fan

[0057] 7 Water collection unit

[0058] 71 First liquid level sensor

[0059] 72 Water seal safety valve

[0060] 8 First valve body

[0061] 9 Second valve body

[0062] 10 First Thermometer

[0063] 11 Pipeline insulation layer

[0064] 12 Second temperature gauge

[0065] 13 Third valve body

[0066] 14 Anemometer

[0067] 15 Third Thermometer

[0068] 16 Fourth valve body

[0069] 17 Liquid storage unit

[0070] 171 Liquid Filter DETAILED DESCRIPTION

[0071] See also Figure 1 . It should be noted that the structures, proportions, sizes, etc. illustrated in the drawings in this specification are only used to match the contents disclosed in the specification for people familiar with this technology to understand and read, and are not used to limit the limiting conditions for the implementation of the present invention, so they have no substantial technical significance. Any modification of the structure, change in the proportional relationship, or adjustment of the size should still fall within the scope of the technical content disclosed by the present invention without affecting the effects and purposes that can be achieved by the present invention. At the same time, the terms such as "upper", "lower", "left", "right", "middle" and "one" quoted in this specification are only for the convenience of description, and are not used to limit the scope of the implementation of the present invention. Changes or adjustments in their relative relationships should also be regarded as the scope of the implementation of the present invention without substantially changing the technical content.

[0072] like Figure 1 In a first aspect, the present invention provides a n-hexane recovery system, comprising a reaction unit 1, a first heat exchange unit 2, a second heat exchange unit 3, a condensation recovery device 4 and a liquid storage unit 17, which are connected in sequence according to the fluid flow direction; the condensation recovery device 4 comprises a tail gas outlet 41, the second heat exchange unit 3 further comprises a second air inlet 23 and a second air outlet 24, the tail gas outlet 41 is connected to the second air inlet 23 through a pipeline; it also comprises a reflux pipe 5, the reaction unit 1 comprises a reaction air inlet 101, and the second air outlet 24 is connected to the reaction air inlet 101 through the reflux pipe 5.

[0073] In the n-hexane recovery system provided by the present invention, the reaction unit 1 includes one or more reactors through which gas flows, a first micro-pressure mechanical gauge 103 is provided on the top of the reactor connected to the reflux pipe 5, and a second micro-pressure mechanical gauge 104 is provided on the top of the reactor close to the first heat exchange unit 2. In a specific embodiment, there may be 6 reactors, each of which is provided with an air inlet and an air outlet, the air inlet of the reactor connected to the reflux pipe 5 is a reaction air inlet 101, the reaction unit 1 also includes a reaction air outlet 102, and the air outlet of the reactor close to the first heat exchange unit 2 is a reaction air outlet 102.

[0074] In the n-hexane recovery system provided by the present invention, the first heat exchange unit 2 is a plate heat exchanger purchased from ALFALAVAL. The n-hexane gas exchanges heat with the low-temperature gas on the other side through the plate heat exchanger, and the temperature of the n-hexane gas is initially lowered, and the gas is mainly above zero degrees.

[0075] In the n-hexane recovery system provided by the present invention, the second heat exchange unit 3 also includes a first air inlet 21, and a circulating fan 6 is provided on the connecting pipeline between the reaction air outlet 102 and the first air inlet 21; a first valve body 8 is also provided on the connecting pipeline between the circulating fan 6 and the first air inlet 21.

[0076] In the n-hexane recovery system provided by the present invention, the second heat exchange unit 3 includes one or more guide tubes 31, and also includes one or more heat exchange pipes 32, each of which is used to connect the air inlet and the air outlet of the second heat exchange unit 3; each heat exchange pipe 32 is provided with a second valve body 9 at the pipe connection between the air inlet and / or the air outlet of the guide tube 31. In a specific embodiment, there can be two guide tubes 31, and there can be four heat exchange pipes 32. The two guide tubes 31 are connected in series to increase the heat exchange area and reduce the cost. The heat exchange pipes are symmetrically distributed on both sides of the guide tube 31. By switching the second valve body 9 to change the airflow direction, the air path that is about to be blocked by ice and ice is given time to defrost, so as to prevent the air path from being blocked by ice and ice. In a specific embodiment, the minimum frequency of the circulating fan 6 is set to 30Hz, and the maximum frequency is set to 55Hz; when the frequency exceeds 55Hz, the system automatically switches the airflow direction of the second valve body 9.

[0077] The n-hexane recovery system provided by the present invention also includes a water collection unit 7, which includes a first liquid level sensor 71 and a water seal safety valve 72 connected in sequence along the liquid flow direction, and the water collection unit 7 is connected to the liquid outlet 311 of each guide tube 31 through a pipeline. The water seal safety valve 72 is respectively provided with a left liquid inlet, a right liquid inlet and a tank bottom port, and the water seal safety valve 72 is used to collect liquefied water. In addition, when the system pressure is too large, the water seal safety valve 72 can also be used to exhaust. The liquid outlet 311 is connected to the tank bottom port of the water seal safety valve 72 through a pipeline, and the outer wall of the pipeline is close to the first liquid level sensor 71. The liquid level sensor 131 is used to detect whether there is water at the lowest point of the water seal safety valve 132. If not, water can be added manually.

[0078] In the n-hexane recovery system provided by the present invention, the connecting pipe between the second heat exchange unit 3 and the condensation recovery device 4, the connecting pipe between the tail gas outlet 41 and the second air inlet 23, and the reflux pipe 5 are sanitary stainless steel pipes.

[0079] In the n-hexane recovery system provided by the present invention, a first thermometer 10 and a pipeline cold insulation layer 11 are provided on the connecting pipeline between the second heat exchange unit 2 and the condensation recovery device 4 along the gas flow direction. The pipeline cold insulation layer 11 is used to separate the outer wall of all sanitary stainless steel pipelines from the air, wrap the pipeline, and prevent the gas in the pipeline from exchanging heat with the gas in the environment.

[0080] In the n-hexane recovery system provided by the present invention, a liquid filter 171 is further provided on the connecting pipe between the liquid storage unit 17 and the condensation recovery device 4, and the temperature in the condensation recovery device 4 is -45°C--35°C, which can be optionally -45-40°C or -40--35°C.

[0081] In the n-hexane recovery system provided by the present invention, a second thermometer 12, a third valve body 13 and an anemometer 14 are provided on the connecting pipe of the tail gas outlet 41 and the second air inlet 23 along the fluid flow direction. The anemometer 14 is used to feedback information when a system failure occurs. For example, when the anemometer 14 does not detect the wind speed, the temperature of the second thermometer 12 changes from -40 degrees to room temperature, indicating that the low-temperature condensation recovery device 4 is to be shut down and start to shut down and defrost. In a specific embodiment, the anemometer 14 is interlocked with the circulating fan 6. The circulating fan 6 automatically changes frequency according to the size of the air volume on the anemometer 14. The circulating fan 6 is started at a low frequency. When the air volume range set on the anemometer 14 is reached, the circulating fan 6 works at a constant frequency.

[0082] In the n-hexane recovery system provided by the present invention, a third thermometer 15 is further provided on the connecting pipeline between the tail gas outlet 41 and the second air inlet 23 .

[0083] In the n-hexane recovery system provided by the present invention, the reflux pipe 5 is provided with an oxygen measuring unit 51, a nitrogen pipeline 52 and a gas pressure monitoring device 54 in sequence along the fluid flow direction.

[0084] In the n-hexane recovery system provided by the present invention, a fourth valve body 16 and a fifth valve body 53 are sequentially provided on the connecting pipe between the oxygen measuring unit 51 and the nitrogen pipeline 52 along the fluid flow direction, wherein the connecting pipe is a part of the reflux pipe 5.

[0085] In the n-hexane recovery system provided by the present invention, the nitrogen pipeline 52 includes a nitrogen bottle 521, a pressure reducing valve 522, a gas throttle valve 523 and a sixth valve body 524 which are sequentially connected along the gas flow direction.

[0086] In the n-hexane recovery system provided by the present invention, the gas pressure monitoring device 54 includes a U-shaped tube 540, and the high-pressure side pipeline of the U-shaped tube 540 is connected to the reflux pipe 5 through a pipeline; the low-pressure side pipeline of the U-shaped tube 540 is provided with a second liquid level sensor 541, a third liquid level sensor 542 and a fourth liquid level sensor 543 in sequence along the liquid outflow direction. When the liquid level of the high-pressure side pipeline in the U-shaped tube 540 is lower than the second liquid level sensor 541, liquid is added manually to replenish liquid to the pipeline; when the liquid level in the U-shaped tube 540 is higher than the fourth liquid level sensor 543, the sixth valve body 524 is closed to stop nitrogen filling; when the liquid level does not exceed the detection range of the third liquid level sensor 542, the sixth valve body 524 is opened to fill nitrogen.

[0087] In the n-hexane recovery system provided by the present invention, a gas filter 55, a sixth valve body 56 and a fourth thermometer 57 are sequentially arranged on the connecting pipe between the gas pressure monitoring device 54 and the reaction gas inlet 101 along the gas flow direction, wherein the connecting pipe is a part of the reflux pipe 5. The gas filter is used to filter the tail gas to prevent impurities from entering the rear end.

[0088] In a specific embodiment of the n-hexane recovery system provided by the present invention, the first valve body 8, the third valve body 13, and 56 are manual ball valves; the second valve body 9 can be a T1 type pneumatic three-way clamp ball valve and / or a T2 type pneumatic three-way clamp ball valve; the fourth valve body 16, the fifth valve body 53, and the seventh valve body 524 are electrically controlled valves.

[0089] In the n-hexane recovery system provided by the present invention, the first micro-pressure mechanical gauge 103, the second micro-pressure mechanical gauge 104, the first thermometer 10, the third thermometer 15, and the fourth thermometer 57 are all used to display the pressure and temperature of each point in the pipeline.

[0090] In the n-hexane recovery system provided by the present invention, the system design gas volume is 9-11m 3 / h, optional 9-10m 3 / h or 10-11m 3 / h, preferably 10m 3 / h.

[0091] Working process of the present invention:

[0092] 1. Before filling with nitrogen, there is no solution in the reactor, only air. Then check the valve switch status. First, the first valve body 8, the third valve body 13, and the seventh valve body 56 are required to be fully open, and the gas throttle valve 523 is closed; secondly, the second valve body 9 is required to be in the straight-through position, and the internal channel is fully opened; the fourth valve body 16, the sixth valve body 524, and the fifth valve body 53 are closed; all other inlets and outlets of the reactor are closed.

[0093] 2. Open the nitrogen bottle 521, adjust the pressure of the pressure reducing valve 522 to 0.04-0.08MPa, which can be 0.04-0.06MPa or 0.06-0.08MPa, first open the nitrogen to fill the sixth valve body 524, then slowly open the gas throttle valve 523 to fill the nitrogen, adjust the opening degree of the gas throttle valve 523 according to the situation of the air pressure monitoring device 54, observe the oxygen content, when the oxygen measuring unit 51 shows that the oxygen content reaches 0.09%, start the circulation fan 6; when the oxygen measuring unit 51 shows that the oxygen content reaches 0.05%, open the fifth valve body 53 and close the fourth valve body 16; observe the circulation wind speed, The wind speed on the anemometer 14 is adjusted to 1.4m / s-1.6m / s by adjusting the opening degree of the first valve body 8 and the third valve body 13, which can be optionally 1.4-1.5m / s or 1.5-1.6m / s; then, when the liquid level is lower than the second liquid level sensor 541, liquid is added manually to replenish liquid to the pipeline; when the liquid level is higher than the fourth liquid level sensor 543, the sixth valve body 524 is closed and nitrogen filling is stopped; when the third liquid level sensor 542 does not detect the liquid level, the sixth valve body 524 is opened to fill nitrogen; then after the system for recovering n-hexane solution operates normally for a period of time, the condensation recovery device 4 is turned on.

[0094] 3. Add the reaction solution into the reactor. The reaction solution is a liquid containing n-hexane used to produce magnetic beads, and then stir all the solutions in the reactor.

[0095] 4. The circulating fan 6 sucks the n-hexane gas in the reactor into the first heat exchange unit 2 for heat exchange. The temperature of the n-hexane gas is initially lowered, and the gas is mainly above zero degrees. Then, the n-hexane gas is heat exchanged with the low-temperature gas on the other side through the second heat exchange unit 3. The n-hexane gas is lowered to below zero degrees. The liquefied water enters the water collection unit 7. When the system pressure is too high, it can be exhausted through the water seal safety valve 72. The first liquid level sensor 71 can detect whether there is water at the lowest point of the water seal safety valve 72. If not, water can be added manually. The temperature in the condensation recovery device 4 is about -40 degrees. The n-hexane gas enters the condensation recovery device 4 for liquefaction. After the liquefied n-hexane is filtered by the liquid filter 171, it enters the liquid storage unit 17 for recovery, and the tail gas is discharged back to the reactor through the reflux pipe 5.

[0096] The second aspect of the present invention provides a method for recovering n-hexane solution from a reaction liquid, comprising the following steps: the gas generated from the reaction unit is subjected to heat exchange through a first heat exchange unit and a second heat exchange unit respectively, and then enters a condensation recovery device for low-temperature condensation to provide a n-hexane liquid phase stream and tail gas, the n-hexane liquid phase stream enters a liquid storage unit after filtration, and the tail gas is refluxed to the reaction unit.

[0097] In the method for recovering n-hexane solution from a reaction liquid provided by the present invention, the reaction liquid is a liquid containing n-hexane and is used to produce magnetic beads.

[0098] In the method for recovering n-hexane solution from reaction liquid provided by the present invention, the gas comprises 1% n-hexane, 98% nitrogen, and other 1% such as water vapor.

[0099] In the method for recovering n-hexane solution from reaction liquid provided by the present invention, the temperature of the low-temperature condensation is -45°C--35°C, which can be -45°C--40°C or -40°C--35°C.

[0100] In order to make the technical means, creative features, objectives and effects achieved by the present invention easier to understand, the present invention is described in detail below in conjunction with embodiments and drawings.

[0101] In the following examples, unless otherwise specified, all reaction raw materials are commercially available products.

[0102] Unless otherwise specified, the purity of each product in each embodiment of the present invention exceeds 98%.

[0103] Example 1

[0104] Before filling with nitrogen, make sure that there is no solution in the reactor, only air. Check and set the valve status: open the first valve body 8, the third valve body 13 and the seventh valve body 56, close the gas throttle valve 523, ensure that the second valve body 9 is in the straight-through position, and all other inlets and outlets of the reactor are closed. Open the nitrogen bottle 521, adjust the pressure of the pressure reducing valve 522 to 0.04-0.08MPa, first fill the sixth valve body 524 with nitrogen, then slowly open the gas throttle valve 523, and adjust the opening degree of the gas throttle valve 523 according to the air pressure monitoring device 54. When the oxygen measuring unit 51 shows that the oxygen content reaches 0.09%, turn on the circulating fan 6; when the oxygen content drops to 0.05%, open the fifth valve body 53 and close the fourth valve body 16. Adjust the first valve body 8 and the third valve body 13, and adjust the wind speed on the anemometer 14 to 1.4-1.6m / s. Adjust the nitrogen filling according to the air pressure monitoring device 54.

[0105] After the system is running normally, the condensation recovery device 4 is started, and the reaction solution is added to the reaction unit 1 and stirred. The gas generated from the reaction unit includes 1% of n-hexane, 98% of nitrogen, and 1% of water vapor. The generated gas enters the condensation recovery device 4 for low-temperature condensation after heat exchange through the first heat exchange unit 2 and the second heat exchange unit 3. The temperature in the condensation recovery device 4 is -40°C to provide n-hexane liquid phase stream and tail gas. The n-hexane liquid phase stream enters the liquid storage unit 17 after filtration. The recovery rate of n-hexane increases with the extension of the system operation time. The tail gas is refluxed to the reaction unit 1, and the temperature of the tail gas is -40°C.

[0106] The above embodiments are preferred cases of the present invention and are not intended to limit the protection scope of the present invention. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, and these simple modifications all belong to the protection scope of the present invention.

[0107] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

Claims

1. A normal hexane recovery system, characterized in that: It comprises a reaction unit (1), a first heat exchange unit (2), a second heat exchange unit (3), a condensation recovery device (4) and a liquid storage unit (17) which are sequentially connected in the direction of fluid flow; The condensation recovery device (4) includes a tail gas outlet (41), and the second heat exchange unit (3) also includes a second air inlet (23) and a second air outlet (24), and the tail gas outlet (41) is connected to the second air inlet (23) through a pipeline; it also includes a reflux pipe (5), and the reaction unit (1) includes a reaction air inlet (101), and the second air outlet (24) is connected to the reaction air inlet (101) through the reflux pipe (5).

2. The n-hexane recovery system according to claim 1, characterized in that: Also includes any one or more of the following features: A1) The reaction unit (1) comprises one or more reaction vessels through which gas flows; A2) The reaction unit (1) further comprises a reaction gas outlet (102), the second heat exchange unit (3) further comprises a first gas inlet (21), and a circulating fan (6) is provided on the connecting pipeline between the reaction gas outlet (102) and the first gas inlet (21).

3. The n-hexane recovery system according to claim 2, characterized in that: Also includes any one or more of the following features: A11) a first micro-pressure mechanical gauge (103) is provided on the top of the reaction kettle connected to the reflux pipe (5); A12) a second micro-pressure mechanical gauge (104) is provided on the top of the reaction kettle close to the first heat exchange unit (2); A21) A first valve body (8) is also provided on the connecting pipe between the circulation fan (6) and the first air inlet (21).

4. The n-hexane recovery system according to claim 1, characterized in that: The second heat exchange unit (3) comprises one or more flow guide tubes (31), and also comprises one or more heat exchange pipes (32), each of the heat exchange pipes (32) being respectively used for connecting an air inlet and an air outlet of the second heat exchange unit (3).

5. The n-hexane recovery system according to claim 4, characterized in that: Also includes any one or more of the following features: B1) further comprises a water collection unit (7), the water collection unit (7) comprising a first liquid level sensor (71) and a water seal safety valve (72) connected in sequence along the liquid flow direction, the water collection unit (7) being connected to the liquid outlet (311) of each guide tube (31) through a pipeline; B2) A second valve body (9) is provided at each of the heat exchange pipes (32) and at the pipe connection point between the air inlet and / or the air outlet of the guide cylinder (31).

6. The n-hexane recovery system according to claim 1, characterized in that: Also includes any one or more of the following features: C1) the first heat exchange unit (2) is a plate heat exchanger; C2) A first temperature gauge (10) and a pipeline cold insulation layer (11) are provided on the connecting pipeline between the second heat exchange unit (2) and the condensation recovery device (4) along the gas flow direction; C3) A liquid filter (171) is also provided on the connecting pipe between the liquid storage unit (17) and the condensation recovery device (4); C4) A second temperature gauge (12), a third valve body (13) and an anemometer (14) are provided on the connecting pipe between the exhaust gas outlet (41) and the second air inlet (23) along the fluid flow direction; C5) A third temperature gauge (15) is also provided on the connecting pipeline between the exhaust gas outlet (41) and the second air inlet (23).

7. The n-hexane recovery system according to claim 1, characterized in that: The reflux pipe (5) is provided with an oxygen measuring unit (51), a nitrogen pipeline (52) and a gas pressure monitoring device (54) in sequence along the fluid flow direction.

8. The n-hexane recovery system according to claim 7, characterized in that: Also includes any one or more of the following features: D1) A fourth valve body (16) and a fifth valve body (53) are provided in sequence on the connecting pipe between the oxygen measuring unit (51) and the nitrogen pipeline (52) along the fluid flow direction; D2) the nitrogen pipeline (52) comprises a nitrogen bottle (521), a pressure reducing valve (522), a gas throttle valve (523) and a sixth valve body (524) which are sequentially connected along the gas flow direction; D3) the air pressure monitoring device (54) comprises a U-shaped tube (540), the high-pressure side pipeline of the U-shaped tube (540) being connected to the return pipe (5) through a pipeline; the low-pressure side pipeline of the U-shaped tube (540) is provided with a second liquid level sensor (541), a third liquid level sensor (542) and a fourth liquid level sensor (543) in sequence along the liquid outflow direction; D4) A gas filter (55), a sixth valve body (56) and a fourth thermometer (57) are sequentially arranged on the connecting pipe between the gas pressure monitoring device (54) and the reaction gas inlet (101) along the gas flow direction.

9. A method for recovering n-hexane solution from a reaction solution, using the n-hexane recovery system according to any one of claims 1 to 8, characterized in that: The steps include: The gas generated from the reaction unit is heat exchanged through the first heat exchange unit and the second heat exchange unit respectively, and then enters the condensation recovery device for low-temperature condensation to provide a n-hexane liquid phase stream and tail gas. The n-hexane liquid phase stream enters the liquid storage unit after filtration, and the tail gas is refluxed to the reaction unit.

10. The method for recovering n-hexane solution from a reaction solution according to claim 9, wherein the temperature of the low-temperature condensation is -45°C to 35°C.

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