System for separating and purifying caprolactam from benzene-hexyl solution

Abstract

The utility model relates to a system for separating and purifying caprolactam from a benzene-hexane solution, which comprises a causticization reactor which is sequentially communicated with a benzene removal tower, a water washing tower and a hexane distillation tower through pipelines, the top of the already-distilled tower is sequentially communicated with the already-distilled tower condenser, the already-distilled tower reflux tank, the already-distilled tower reflux pump and the caprolactam product storage tank through pipelines, and the already-distilled tower reflux pump is communicated with the already-distilled tower through a pipeline. The device is simple in process, less in equipment and simple to operate and control, and the caprolactam product meeting GB / T 13254-2017 industrial caprolactam superior products can be purified from the benzene-hexyl solution through causticization reactions such as causticization reaction, debenzolization, water washing, distillation and the like and three tower processes.

Description

Technical Field

[0001] The utility model relates to the technical field of caprolactam refining, in particular to a system for separating and purifying caprolactam from a benzene-hexyl solution. Background Art

[0002] Caprolactam is an important organic chemical raw material and an important monomer for synthetic fibers and synthetic resins. It is mainly used as a raw material for the production of polyamide 6 engineering plastics and polyamide 6 fibers. It can also be used to produce antiplatelet drugs such as 6-aminocaproic acid and lauroquine oxadiazole, and has a wide range of uses. Known methods for producing caprolactam include the cyclohexanone oxime liquid phase Beckmann rearrangement method using fuming sulfuric acid as a catalyst, the cyclohexanone oxime gas phase Beckmann rearrangement method using solid zeolite as a catalyst, and the depolymerization of waste polymers to produce caprolactam. The solvent rearrangement product amide oil needs to be pre-extracted with benzene to extract the caprolactam in the amide oil. The extraction phase is a benzene-hexyl solution containing about 30ω% of caprolactam. The benzene-hexyl solution inevitably contains a variety of impurities, many of which are currently uncharacterized. The impurities are removed by refining the benzene-hexyl solution to obtain a caprolactam product that meets national standards. At present, the benzene-hexyl solution refining process generally uses a combination of benzene extraction, water extraction, ion exchange, hydrogenation, triple-effect evaporation, distillation and other processes to obtain a caprolactam product. This process has a series of problems such as long process, many equipment, much wastewater, high energy consumption, and unstable product quality. Therefore, in the field of caprolactam production technology, reducing energy consumption, reducing wastewater volume, and improving product quality are currently issues to be solved. Summary of the invention

[0003] In view of the problems existing in the prior art, the utility model provides a device for separating and purifying caprolactam from a benzene-hexyl solution.

[0004] The utility model is realized by the following technical solutions:

[0005] A system for separating and purifying caprolactam from a benzene-hexyl solution, the system comprising a causticizing reactor, the causticizing reactor being connected in sequence with a debenzene tower, a water washing tower and a caprolactam distillation tower through a pipeline, the top of the caprolactam distillation tower being connected in sequence with a caprolactam distillation tower condenser, a caprolactam distillation tower reflux tank, a caprolactam distillation tower reflux pump and a caprolactam product storage tank through a pipeline, and the caprolactam distillation tower reflux pump being connected to the caprolactam distillation tower through a pipeline.

[0006] Preferably, the top of the debenzene tower is connected to the debenzene tower top condenser, the debenzene tower reflux tank, the debenzene tower reflux pump and the benzene distillation section in sequence through a pipeline, and the debenzene tower reflux pump is connected to the debenzene tower through a pipeline.

[0007] Preferably, the top of the water washing tower is connected to the water washing tower condenser, the water washing tower reflux tank, the water washing tower reflux pump and the sewage treatment section in sequence through a pipeline, and the water washing tower reflux pump is connected to the water washing tower through a pipeline.

[0008] Preferably, the causticizing reactor, the debenzene tower reflux tank, the water washing tower reflux tank and the distillation tower reflux tank are respectively connected to the tail gas treatment device through pipelines.

[0009] Further preferably, a water washing tower vacuum pump is provided between the water washing tower reflux tank and the tail gas treatment device, and a distillation tower vacuum pump is provided between the distillation tower reflux tank and the tail gas treatment device.

[0010] Preferably, the debenzene tower is provided with a debenzene tower reboiler, the water washing tower is provided with a water washing tower reboiler, and the hexyl distillation tower is provided with a hexyl distillation tower reboiler.

[0011] Preferably, the bottom of the distillation tower is connected to a distillation tower discharge pump and a residual liquid treatment device in sequence through a pipeline.

[0012] Preferably, the causticizing reactor is provided with an agitator; the debenzene tower adopts a normal pressure packed tower, is provided with 4 to 7 layers of packing, is provided with liquid nozzles in the reflux layer and the feed layer, is provided with a liquid distributor above each layer of packing, and is provided with a demister at the top of the tower; the water washing tower and the distillation tower are negative pressure towers.

[0013] According to the characteristics of impurities in benzene-hexyl solution, a device for separating and purifying caprolactam from benzene-hexyl solution is provided. The benzene-hexyl solution containing 30ω% of caprolactam is successively subjected to causticizing reaction, debenzening, water washing, distillation and other processes to remove impurities in the benzene-hexyl solution, and produce a superior caprolactam product that exceeds the national standard. The utility model first passes the benzene-hexyl solution into a causticizing reactor, in which the acidic impurities react with caustic soda to generate easily removable substances; secondly, the benzene-hexyl solution after the causticizing reaction is passed into a debenzening tower to separate benzene and benzene-soluble impurities; then, the crude caprolactam after debenzening is passed into a water washing tower to separate water-soluble impurities; finally, the crude caprolactam is passed into a hexyl distillation tower to separate heavy component impurities, and the caprolactam product is separated and purified at the top of the tower.

[0014] The utility model has the following beneficial effects:

[0015] The utility model has a simple process, few equipments and simple operation and control. The benzene-hexyl solution can be purified into a caprolactam product that meets the requirements of GB / T 13254-2017 "Industrial Caprolactam" by successively passing through causticizing reaction, debenzenization, water washing, distillation and other causticizing reactions + 3 tower processes. Compared with the traditional benzene-hexyl solution refining technology, this patented technology has a small one-time investment, does not require expensive resins or catalysts, and reduces the energy consumption of the device by about 10%. Most of the impurities can be removed through causticizing reaction, debenzenization, water washing, distillation and other processes, and the purified caprolactam is superior to GB / T 13254-2017 "Industrial Caprolactam". Table 1 compares the caprolactam product indicators purified by this system with GB / T 13254-2017 "Industrial Caprolactam".

[0016] Table 1

[0017] BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a diagram showing the connection relationship of the equipment of the present utility model.

[0019] In the figure, causticizing reactor 1, causticizing reactor discharge pump 2, debenzene tower 3, debenzene tower top condenser 4, debenzene tower reflux tank 5, debenzene tower reflux pump 6, debenzene tower reboiler 7, debenzene tower kettle discharge pump 8, water washing tower 9, water washing tower condenser 10, water washing tower reflux tank 11, water washing tower reflux pump 12, water washing tower vacuum pump 13, water washing tower kettle discharge pump 14, water washing tower reboiler 15, hexane distillation tower 16, hexane distillation tower condenser 17, hexane distillation tower reflux pump 18, hexane distillation tower vacuum pump 19, hexane distillation tower reflux tank 20, hexane distillation tower discharge pump 21, hexane distillation tower reboiler 22, benzene distillation section 23, sewage treatment section 24, caprolactam product storage tank 25, residual liquid treatment device 26, tail gas treatment device 27. DETAILED DESCRIPTION

[0020] In order to enable those skilled in the art to better understand the present invention and implement it, the present invention is further described below in conjunction with the accompanying drawings and specific embodiments, but the embodiments are not intended to limit the present invention.

[0021] Example 1

[0022] A system for separating and purifying caprolactam from a benzene-hexyl solution, the system comprising a causticizing reactor 1, the causticizing reactor 1 being connected in sequence with a debenzene tower 3, a water washing tower 9 and a caprolactam distillation tower 16 through a pipeline, the top of the caprolactam distillation tower 16 being connected in sequence with a caprolactam distillation tower condenser 17, a caprolactam distillation tower reflux tank 20, a caprolactam distillation tower reflux pump 18 and a caprolactam product storage tank 25 through a pipeline, and the caprolactam distillation tower reflux pump 18 being connected with the caprolactam distillation tower 16 through a pipeline.

[0023] Preferably, the top of the debenzene tower 3 is connected to the debenzene tower top condenser 4, the debenzene tower reflux tank 5, the debenzene tower reflux pump 6 and the benzene distillation section 23 in sequence through a pipeline, and the debenzene tower reflux pump 6 is connected to the debenzene tower 3 through a pipeline.

[0024] Preferably, the top of the water washing tower 9 is connected to the water washing tower condenser 10, the water washing tower reflux tank 11, the water washing tower reflux pump 12 and the sewage treatment section 24 in sequence through a pipeline, and the water washing tower reflux pump 12 is connected to the water washing tower 9 through a pipeline.

[0025] Preferably, the causticizing reactor 1, the debenzene tower reflux tank 5, the water washing tower reflux tank 11 and the distillation tower reflux tank 20 are respectively connected to the tail gas treatment device 27 through pipelines.

[0026] Further preferably, a water washing tower vacuum pump 13 is provided between the water washing tower reflux tank 11 and the tail gas treatment device 27 , and a distillation tower vacuum pump 19 is provided between the distillation tower reflux tank 20 and the tail gas treatment device 27 .

[0027] Preferably, the debenzene tower 3 is provided with a debenzene tower reboiler 7 , the water washing tower 9 is provided with a water washing tower reboiler 15 , and the hexyl distillation tower 16 is provided with a hexyl distillation tower reboiler 22 .

[0028] Preferably, the bottom of the distillation tower 16 is connected to the distillation tower discharge pump 21 and the residual liquid treatment device 26 in sequence through a pipeline.

[0029] Preferably, the causticizing reactor 1 is provided with an agitator; the debenzene tower 3 adopts a normal pressure packed tower, is provided with 4 to 7 layers of packing, is provided with liquid nozzles in the reflux layer and the feed layer, is provided with a liquid distributor above each layer of packing, and is provided with a demister at the top of the tower; the water washing tower 9 and the distillation tower 16 are negative pressure towers.

[0030] According to the characteristics of impurities in benzene-hexyl solution, a device for separating and purifying caprolactam from benzene-hexyl solution is provided. The benzene-hexyl solution containing 30ω% of caprolactam is successively subjected to causticizing reaction, debenzening, water washing, distillation and other processes to remove impurities in the benzene-hexyl solution, and produce a superior caprolactam product that exceeds the national standard. The utility model first passes the benzene-hexyl solution into a causticizing reactor, in which the acidic impurities react with caustic soda to generate easily removable substances; secondly, the benzene-hexyl solution after the causticizing reaction is passed into a debenzening tower to separate benzene and benzene-soluble impurities; then, the crude caprolactam after debenzening is passed into a water washing tower to separate water-soluble impurities; finally, the crude caprolactam is passed into a hexyl distillation tower to separate heavy component impurities, and the caprolactam product is separated and purified at the top of the tower.

[0031] A benzene-hexyl solution containing about 30ω% of caprolactam and 32% of caustic soda are respectively introduced into a causticizing reactor 1 through pipelines in a certain proportion, and some acidic impurities in the benzene-hexyl solution react with the caustic soda to generate easily removable substances; the benzene-hexyl solution after the causticizing reaction is transported to the middle of a debenzene tower 3 through a discharge pump 2 of the causticizing reactor and a pipeline, and the light component benzene entrains some benzene-soluble impurities and flows from bottom to top, and is cooled at the top of the tower by a debenzene tower condenser 4 to become liquid phase impure benzene and flows into a debenzene tower reflux tank 5 by gravity, and a part of the impure benzene is pressurized by a debenzene tower reflux pump 6 and then transported to a benzene distillation section 23 for distillation and separation to obtain refined benzene. The debenzene tower 3 is recycled, a part of it is refluxed to the debenzene tower 3 to control the tower top temperature, and the factory by-product steam of 0.1MPa is transported to the debenzene tower reboiler 7 through a pipeline as the heat source of the debenzene tower 3; it is extracted from the tower top and sent to the benzene distillation section 23 for separation and purification of refined benzene for recycling; the crude caprolactam solution in the tower bottom of the debenzene tower 3 is transported to the middle of the water washing tower 9 through the debenzene tower bottom pump 8 and a pipeline, the crude caprolactam solution enters the water washing tower 9 from the middle and flows downward, and the desalted water is added from the tower bottom through a pipeline and flows from bottom to top, the crude caprolactam solution and the desalted water are in countercurrent contact in the water washing tower 9, and some water-soluble impurities are carried away by the desalted water. The wastewater containing impurities is cooled into liquid phase by the condenser 10 of the water washing tower and flows into the reflux tank 11 of the water washing tower by gravity. After the wastewater is pressurized by the reflux pump 12 of the water washing tower, part of it is sent to the sewage treatment section 24, and part of it is refluxed to the water washing tower 9 to control the temperature of the top of the tower. The 0.1MPa factory by-product steam is passed through the pipeline to the reboiler 15 of the water washing tower as the heat source of the water washing tower. The negative pressure of the water washing tower 9 is maintained by the vacuum pump 13 of the water washing tower; the crude caprolactam in the kettle of the water washing tower 9 is pressurized by the kettle pump 14 of the water washing tower and then passed into the middle part of the distillation tower 16. The distillation tower 16 is preferably a negative pressure tower through the distillation tower vacuum pump 1 9 is maintained, 1.0MPa factory steam is introduced into the reboiler 22 of the distillation tower through a pipeline as a heat source, the caprolactam solution is vaporized in the distillation tower 16 and rises from bottom to top, and is condensed into liquid phase by the distillation tower cooler 17 at the top of the tower and flows into the distillation tower reflux tank 20 by gravity, and the product caprolactam is pressurized by the distillation tower reflux pump 18, and a part of it is extracted as the caprolactam product to the caprolactam product storage tank 25, and a part of it is refluxed to the distillation tower 16 to control the top temperature of the tower, and the residual liquid in the bottom of the distillation tower 16 is transported to the residual liquid treatment section 26 by the distillation tower bottom pump 21 to further recover the caprolactam.

[0032] The liquid alkali added to the causticizing reactor is a cheap 32% caustic soda solution, and the mass ratio of caustic soda to benzene-hexyl solution is preferably 1:50. The causticizing reactor 1 is provided with an electric stirrer to mix the caustic soda and the benzene-hexyl solution evenly, so that the neutralization reaction can occur effectively. The causticizing reactor 1 is nitrogen-sealed and maintained at a slight positive pressure, and the reaction temperature is room temperature.

[0033] The debenzene tower 3 adopts a normal pressure packed tower, and the debenzene tower reboiler 7 adopts 0.1MPa steam of the factory by-product as a heat source to control the tower kettle temperature at 80-83°C, and the tower top temperature is controlled at 50°C. The tower plate filler is preferably a wire mesh filler with good mass transfer and heat transfer effects. 4-7 layers of fillers are set according to the flow rate of the benzene-hexyl solution. Liquid nozzles are set in the reflux layer and the feed layer to evenly spray the liquid onto the liquid distributor. A liquid distributor is set above each layer of filler so that the liquid can be evenly distributed on the filler. A demister is set on the top of the tower to intercept the heavy component caprolactam entrained in the rising gas phase. A debenzene tower cooler 4 and a debenzene tower reflux tank 5 are set on the top of the tower to cool the rising gas phase material to 40°C. A part of it is used as the top reflux to control the tower top temperature at 50°C, and a part of it is taken out as miscellaneous benzene and sent to the benzene distillation section 23.

[0034] The water washing tower 9 preferably adopts a negative pressure tower, and the tower pressure is controlled at an absolute pressure of 58KPa by the water washing tower vacuum pump 13. The tower kettle is provided with a water washing tower reboiler 15, which uses the factory by-product 0.1MPa steam as a heat source to control the tower kettle temperature at 90°C and the tower top temperature at 65°C. The water washing tower 9 is set as a "rotating disk tower" with a special structure. With the help of the motor installed on the top of the tower to drive the rotation of the rotating disk on the middle vertical axis, the crude caprolactam solution is dispersed on the tower plate to obtain the fine droplets required for washing. 5 to 10 layers of tower plates are set according to the load of the device. In order to achieve a better impurity washing effect, the crude caprolactam solution is introduced from the middle of the tower to flow downward, and the desalted water is introduced from the tower kettle to flow from bottom to top. The mass flow ratio of the crude caprolactam solution entering the water washing tower to the desalted water is 5:1. The crude caprolactam solution and the desalted water are in countercurrent and uniform contact on the tower plate, and the water-soluble impurities are carried by the desalted water and extracted from the top of the tower to the treatment section 24 of the sewage treatment device.

[0035] The distillation tower 16 preferably adopts a negative pressure tower, and the tower pressure is controlled at an absolute pressure of 90KPa by the distillation tower vacuum pump 19. The tower bottom is provided with a distillation tower reboiler 22, which uses 1.0MPa steam as a by-product of the factory as a heat source to control the tower bottom temperature at 140°C, and the tower top temperature is controlled at 90°C. The tower plate filler is preferably a wire mesh filler with good mass transfer and heat transfer effects, and 5 to 8 layers of filler are arranged. Liquid nozzles are provided in the reflux layer and the feed layer to evenly spray the liquid onto the liquid distributor.

[0036] The generated tail gas is transported to the tail gas treatment device 27 through a collecting pipe for recovery and treatment to meet environmental emission standards; the generated sewage is transported to the sewage treatment device 24 through a collecting pipe for centralized treatment.

[0037] The above embodiments are only preferred technical solutions of the present invention and should not be regarded as limitations of the present invention. The embodiments and features in the embodiments of the present application can be arbitrarily combined with each other without conflict. The protection scope of the present invention shall be the technical solutions recorded in the claims, including the equivalent replacement solutions of the technical features in the technical solutions recorded in the claims. That is, equivalent replacement improvements within this scope are also within the protection scope of the present invention.

Claims

1. A system for separating and purifying caprolactam from a benzene-hexyl solution, characterized in that: The system comprises a causticizing reactor (1), wherein the causticizing reactor (1) is connected to a debenzene tower (3), a water washing tower (9) and a caprolactam distillation tower (16) in sequence through a pipeline, and the top of the caprolactam distillation tower (16) is connected to a caprolactam distillation tower condenser (17), a caprolactam distillation tower reflux tank (20), a caprolactam distillation tower reflux pump (18) and a caprolactam product storage tank (25) in sequence through a pipeline, and the caprolactam distillation tower reflux pump (18) is connected to the caprolactam distillation tower (16) through a pipeline.

2. The system for separating and purifying caprolactam from benzene-hexyl solution according to claim 1, characterized in that: The top of the debenzene tower (3) is connected to the debenzene tower top condenser (4), the debenzene tower reflux tank (5), the debenzene tower reflux pump (6) and the benzene distillation section (23) in sequence through a pipeline, and the debenzene tower reflux pump (6) is connected to the debenzene tower (3) through a pipeline.

3. The system for separating and purifying caprolactam from benzene-hexyl solution according to claim 1, characterized in that: The top of the water washing tower (9) is connected to the water washing tower condenser (10), the water washing tower reflux tank (11), the water washing tower reflux pump (12) and the sewage treatment section (24) in sequence through a pipeline, and the water washing tower reflux pump (12) is connected to the water washing tower (9) through a pipeline.

4. The system for separating and purifying caprolactam from benzene-hexyl solution according to claim 3, characterized in that: The causticizing reactor (1), the debenzene tower reflux tank (5), the water washing tower reflux tank (11) and the distillation tower reflux tank (20) are respectively connected to the tail gas treatment device (27) through pipelines.

5. The system for separating and purifying caprolactam from benzene-hexyl solution according to claim 4, characterized in that: A water washing tower vacuum pump (13) is provided between the water washing tower reflux tank (11) and the tail gas treatment device (27), and a distillation tower vacuum pump (19) is provided between the distillation tower reflux tank (20) and the tail gas treatment device (27).

6. The system for separating and purifying caprolactam from benzene-hexyl solution according to claim 1, characterized in that: The debenzene tower (3) is provided with a debenzene tower reboiler (7), the water washing tower (9) is provided with a water washing tower reboiler (15), and the hexyl distillation tower (16) is provided with a hexyl distillation tower reboiler (22).

7. The system for separating and purifying caprolactam from benzene-hexyl solution according to claim 6, characterized in that: The bottom of the distillation tower (16) is connected to the distillation tower discharge pump (21) and the residual liquid treatment device (26) in sequence through a pipeline.

8. The system for separating and purifying caprolactam from benzene-hexyl solution according to claim 1, characterized in that: The causticizing reactor (1) is provided with a stirrer; the debenzene tower (3) is a normal pressure packed tower, provided with 4 to 7 layers of packing, liquid nozzles are provided in the reflux layer and the feed layer, a liquid distributor is provided above each layer of packing, and a demister is provided at the top of the tower; the water washing tower (9) and the distillation tower (16) are negative pressure towers.

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