Ammonium sulfate neutralizing and crystallizing device and method thereof

Abstract

The invention discloses an ammonium sulfate neutralization and crystallization device and method, the ammonium sulfate neutralization and crystallization device comprises a tubular ammonia-water mixer, a tubular neutralization reactor, an ammonium sulfate crystallizer and a gas-liquid separator, the tubular neutralization reactor adopts a Venturi type and / or static mixing type tubular neutralization reactor, and the gas-liquid separator adopts a gas-liquid separator. The tubular neutralization reactor comprises a central spray pipe and a peripheral channel which forms a certain angle with the central spray pipe and intersects with the central spray pipe, a liquid outlet of the tubular ammonia-water mixer is communicated with a liquid inlet of the central spray pipe, and a liquid inlet of the peripheral channel is communicated with a liquid outlet of caprolactam redischarge liquid. According to the method, energy is recycled at the cost of increasing the investment of one-time equipment, saturated steam with a relatively high heat value can be produced as a byproduct, meanwhile, the loss of caprolactam and the load of a vacuum pump are reduced, and the neutralization reaction heat is fully utilized, so that the energy consumption of caprolactam production is further reduced; the purposes of increasing the yield, saving the raw material cost and reducing the energy consumption are achieved.

Description

Technical Field

[0001] The invention relates to a crystallization device, in particular to an ammonium sulfate neutralization crystallization device and a method thereof. Background Art

[0002] At present, the production of caprolactam at home and abroad basically needs to adopt the cyclohexanone oxime rearrangement process under the action of oleum, and its rearrangement reaction product is usually called caprolactam rearrangement liquid or simply rearrangement liquid (i.e., caprolactam containing 49-58wt% of oleum). Since the oleum content in the caprolactam rearrangement liquid is very high, and there is currently no effective means to separate it from caprolactam and recycle it, it is necessary to use ammonia to neutralize it, thereby producing ammonium sulfate as a by-product.

[0003] The solubility of ammonium sulfate in water varies with temperature as shown below:

[0004] (70.6g / 0℃, 75.4g / 20℃, 81.0g / 40℃, 88.0g / 60℃, 95.3g / 80℃, 103.8g / 100℃).

[0005] Since the solubility of ammonium sulfate in water changes little with temperature, it is generally necessary to adopt evaporation concentration to perform crystallization separation. At present, the neutralization of caprolactam rearrangement liquid and ammonia in industry generally adopts DTB (draft tube baffle) type neutralization evaporation crystallizer (New device for neutralization reaction crystallization of caprolactam ammonium sulfate, Enterprise Technology Development, 2005, vol.24, No.9; CN1757599A, 2006), that is, a draft tube plus baffle type neutralization evaporation crystallizer integrating concentration, evaporation, crystallization and decantation. Ammonia and caprolactam rearrangement liquid and ammonium sulfate aqueous solution (mainly composed of circulating ammonium sulfate crystal mother liquor) all directly enter this neutralization evaporation crystallizer, usually carry out neutralization reaction and crystallization at 15-20kPa (absolute pressure) and 55-65°C, and simultaneously utilize the heat of neutralization reaction and the mixed dissolution heat of sulfuric acid, ammonia and water to carry out evaporation concentration and crystallization to generate slurry containing ammonium sulfate particles (i.e. ammonium sulfate slurry), and utilize the baffle design in the device to separate amide oil (i.e. caprolactam crude oil containing 20-30wt% of water) from ammonium sulfate slurry (similar to decantation), and pump them to the caprolactam refining process for refining and purification; the ammonium sulfate slurry is extracted from the DTB neutralization evaporation crystallizer by a pump and enters the solid-liquid separation system (mainly thickening, centrifugation and drying, etc.) to separate the ammonium sulfate crystals, and the remaining ammonium sulfate mother liquor is recycled. For the water vapor evaporated from the DTB neutralization crystallizer, cooling water is generally used to cool and condense it through a condenser to generate negative pressure, so that the pressure in the device is maintained at 15 to 20 kPa (absolute pressure).

[0006] The advantages of the above-mentioned industrial neutralization crystallization device for caprolactam rearrangement liquid and ammonia are very obvious: the DTB neutralization evaporation crystallizer used integrates reaction, evaporation concentration and crystallization as well as amide oil separation, so the number of equipment is small, the process flow is relatively simple, and no additional energy is required for evaporation and concentration.

[0007] However, the disadvantages of this device are also very obvious:

[0008] (1) Due to the high heat release of the neutralization reaction and mixed dissolution of oleum and ammonia, a large amount of evaporation water is required to ensure a low crystallization temperature (such as 55-65°C). Moreover, the steam has almost no utilization value due to its low temperature, and a large amount of cooling water and a large condenser are required to condense it. For example, a 200,000-ton caprolactam unit needs to evaporate 27.5-30 tons of water vapor per hour, and correspondingly requires about 2700m3 of cooling water. 3 / h and equipped with about 1600m 2 The condenser is shown in Figure 2. It can be seen that the energy consumption is still relatively large.

[0009] (2) It is precisely because the current DTB neutralization evaporation crystallizer integrates the functions of neutralization reaction, evaporation concentration and crystallization, and amide oil separation, that the equipment is not only too large, complex in structure, and difficult to operate and control, but also the particle size of the ammonium sulfate crystal is small and difficult to control.

[0010] Therefore, the Chinese patent application with publication number CN 113368527 A proposes that by setting a condenser in the original DTB neutralization crystallizer body, the amount of evaporation steam discharged can be greatly reduced, thereby reducing the diameter of the top vapor phase pipe and the difficulty of layout; at the same time, the use of a jet vacuum condenser using the circulating mother liquid can reduce the amount of circulating cooling water by about 10%. However, due to the addition of a circulating mother liquid jet pump, some power consumption is increased compared to the original device. The Chinese patent application with publication number CN 115353122A proposes a method and device for generating high-temperature steam using the heat of neutralization reaction. First, ammonia water and caprolactam rearrangement liquid are added to the neutralization reactor together, and a neutralization reaction is carried out at a higher temperature to generate steam with a higher calorific value, and then the steam enters the flash crystallizer for cooling and crystallization, thereby using the neutralization heat to generate steam with a higher calorific value. However, since caprolactam hydrolyzes quickly under high temperature conditions, although the neutralization reaction takes a short time, the gas-liquid separation takes a long time. Therefore, the design and control of this method that integrates the neutralization reaction and gas-liquid separation may be very difficult, especially for materials with high viscosity such as caprolactam rearrangement liquid.

[0011] A Chinese patent application with publication number CN111498869A discloses an ammonium sulfate neutralization crystallization method and device thereof, the device comprising an OLSO type neutralization crystallizer, a tubular neutralization reactor and a sedimentation separator, the neutralization reactor being arranged outside the OLSO type neutralization crystallizer, and the tubular neutralization reactor being provided with a water input end, a rearrangement liquid input end, an ammonia gas or ammonia water input end and a crystallizer circulating liquid input end; an output end of the sedimentation separation region of the OLSO type neutralization crystallizer is connected to an inlet of a tubular neutralization reactor cylinder through an external circulation pump; an outlet at the upper part of the tubular neutralization reactor is connected to a first sedimentation separator, and an output end at the bottom of the first sedimentation separator is connected to an evaporation chamber of the OLSO type neutralization crystallizer; another output end at the upper part of the sedimentation separation region of the OLSO type neutralization crystallizer is connected to a second sedimentation separator, an output end at the bottom of the second sedimentation separator is connected to the lower part of the OLSO type crystallizer, and an output end at the bottom of the OLSO type crystallizer is connected to a centrifuge, a dryer and a sieving machine in sequence through a third sedimentation separator. In this scheme, a small amount of neutralization heat and ammonia dissolution heat can be used to control the morphology of ammonium sulfate crystals, but it cannot achieve the effect of reducing costs and saving energy. Caprolactam is a substance that is easily hydrolyzed at high temperatures. The reaction time in the tubular neutralization reactor in this scheme is long, and the loss of caprolactam is large. Summary of the invention

[0012] The technical problem to be solved by the present invention is to provide an ammonium sulfate neutralization crystallization device and a method thereof in view of the deficiencies in the prior art, so as to reduce the loss of caprolactam and make full use of the heat of the neutralization reaction to further reduce the energy consumption of caprolactam production, thereby achieving the purpose of increasing output, saving raw material costs and reducing energy consumption.

[0013] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0014] An ammonium sulfate neutralization crystallization device comprises a tubular ammonia-water mixer, a tubular neutralization reactor, an ammonium sulfate crystallizer, and a gas-liquid separator. The tubular neutralization reactor adopts a Venturi neutralization reactor, a static tubular neutralization reactor, or a Venturi and static mixed tubular neutralization reactor. The tubular neutralization reactor comprises a central nozzle and a peripheral channel which forms a certain angle with and intersects with the central nozzle. The liquid outlet of the tubular ammonia-water mixer is connected to the liquid inlet of the central nozzle, the liquid inlet of the peripheral channel is connected to the liquid outlet of caprolactam rearrangement liquid, the liquid outlet of the central nozzle is connected to the liquid inlet of the gas-liquid separator, the liquid outlet of the gas-liquid separator is connected to the liquid inlet of the ammonium sulfate crystallizer, and the gas outlet of the gas-liquid separator is connected to the gas inlet of a heat exchange device.

[0015] First, ammonia gas and an aqueous solution containing ammonium sulfate are mixed in a tubular ammonia-water mixer to generate an ammonia aqueous solution containing ammonium sulfate, and then neutralized and crystallized with a caprolactam rearrangement liquid containing fuming sulfuric acid in a tubular neutralization reactor. The steam separated by the gas-liquid separator is used as a heat source, and the amide oil (i.e., caprolactam crude oil containing a certain amount of water) separated by the ammonium sulfate crystallizer is sent for refining.

[0016] The gas-liquid separator in the present invention is used to quickly separate the reaction liquid after the neutralization reaction from the large amount of high-temperature steam generated to reduce the loss of caprolactam and utilize the large amount of heat energy generated by the reaction; the sedimentation separator in the Chinese patent application with publication number CN111498869A is used to further evaporate and separate the ammonium sulfate-containing liquid after the neutralization reaction.

[0017] In the present invention, a large amount of high-pressure and high-temperature steam is supplied externally and quickly separated from the neutralized rearrangement liquid, which reduces the loss of caprolactam due to high-temperature hydrolysis and eliminates the waste of only low-temperature negative-pressure steam in the existing process. However, the Chinese patent application with publication number CN111498869A only uses the neutralization heat and the ammonia dissolution heat to control the morphology of ammonium sulfate crystals, which cannot achieve the cost reduction and energy saving effect of the present invention.

[0018] The tubular neutralization reactor described in the present invention fully mixes ammonia and water to carry out neutralization reaction. However, the Chinese patent application with publication number CN111498869A distributes through a distribution pipe in the neutralization reactor, and it can be seen in the legend that the distribution pipe is a cylindrical structure. In addition, its "tubular neutralization reactor" is also a cylindrical structure, which is inconsistent with the structure described in the present invention. This structure cannot ensure that a large amount of high-temperature steam generated by the neutralization reaction is quickly removed, and a large amount of neutralization heat is easy to cause thermal hydrolysis of caprolactam in this process.

[0019] The central nozzle of the mixer is conducive to more complete premixing in high-speed flow and reduces micro-mixing effects.

[0020] In a preferred embodiment of the present invention, the water phase liquid outlet of the ammonium sulfate crystallizer is connected to the liquid inlet of the liquid injection pump, the liquid outlet of the liquid injection pump is connected to the liquid inlet of the liquid collecting tank, and the oil phase liquid outlet of the ammonium sulfate crystallizer is connected to the liquid inlet of the solid-liquid separation device.

[0021] In a preferred embodiment of the present invention, the gas-liquid separator includes a gas phase space with an upper cross-sectional area of ​​S1 and a liquid phase space with a lower cross-sectional area of ​​S2, S1 / S2=2~20, preferably S1 / S2=3~15, and further preferably S1 / S2=4~10.

[0022] The function of the gas-liquid separator in the present invention is to expand the gas volume to reduce the partial pressure and make vaporization easier. If the ratio is too low, vaporization will be difficult; if the ratio is too high, the separator volume will be too large, wasting space.

[0023] In a preferred embodiment of the present invention, the tubular ammonia-water mixer is a Venturi-type neutralization reactor, a static tubular neutralization reactor, or a Venturi-type and static mixed tubular neutralization reactor.

[0024] The present invention also discloses a neutralization crystallization method of the ammonium sulfate neutralization crystallization device, comprising the following steps:

[0025] S1, passing ammonia gas and an aqueous solution containing ammonium sulfate into a tubular ammonia-water mixer to mix and generate an ammonia aqueous solution containing ammonium sulfate;

[0026] S2, passing the aqueous ammonia solution containing ammonium sulfate obtained in S1 into the central nozzle of the tubular neutralization reactor, and passing the caprolactam rearrangement liquid containing fuming sulfuric acid into the peripheral channel of the tubular neutralization reactor to carry out a neutralization reaction;

[0027] The liquid after the neutralization reaction of S3 and S2 is passed into the gas-liquid separator;

[0028] The liquid separated from the liquid outlet of the gas-liquid separator in S4 and S3 is introduced into the ammonium sulfate crystallizer, and the amide oil and the water phase containing ammonium sulfate crystals are separated from the ammonium sulfate crystallizer. The steam from the gas outlet of the gas-liquid separator in S3 is introduced into the heat exchange device for use as a heat source.

[0029] The steam coming out from the upper part of the gas-liquid separator is sent to be used as a heat source, and the generated condensate should be recycled, preferably recycled back to the collecting tank for utilization.

[0030] In the crystallization step, the liquid phase discharged from the gas-liquid separator enters the ammonium sulfate crystallizer for rapid cooling and crystallization, and oil-water separation is performed in the crystallizer at the same time. The liquid phase in the ammonium sulfate crystallizer is divided into two phases, oil and water. The oil phase is called amide oil, that is, crude caprolactam oil containing a certain amount of water, which is sent for refining to obtain a caprolactam product; the water phase is a slurry containing ammonium sulfate crystals, which is sent for solid-liquid separation to obtain an ammonium sulfate solid product. The remaining mother liquor after solid-liquid separation is sent to a liquid collecting tank for recycling.

[0031] In a preferred embodiment of the present invention, the outlet pressure of the tubular neutralization reactor in S2 is 100 kPa to 300 kPa, preferably 110 kPa to 250 kPa; more preferably 120 kPa to 200 kPa.

[0032] In the present invention, the reactor outlet pressure is adjusted to further adjust the temperature of the high-temperature steam generated in the neutralization reaction. If the pressure is too low, the generated steam temperature will be low; if the pressure is too high, the vaporization difficulty will increase, making the neutralization heat insufficient to provide vaporization heat.

[0033] The tubular neutralization reactor adopts adiabatic operation, which means that there is no heat exchange or mass exchange between the surrounding environment. Insulation is used to reduce heat loss of equipment and improve production capacity.

[0034] In a preferred embodiment of the present invention, the tubular neutralization reactor adopts a Venturi-type tubular neutralization reactor, the average flow velocity of the central nozzle of the Venturi-type tubular neutralization reactor is V1, and the average flow velocity of the peripheral channel is V2; V2 / V1=0.2~10, preferably V2 / V1=0.6~6, and further preferably V2 / V1=1.0~3.0.

[0035] The purpose of adjusting the flow rate in the present invention is to strengthen the microscopic mixing effect. If the ratio is too low, the sulfuric acid molecules in the caprolactam rearrangement liquid will not diffuse in time and thus become a macroscopic fluid; if the ratio is too high, the amount of ammonia water will be insufficient, resulting in incomplete reaction of sulfuric acid in the caprolactam rearrangement liquid.

[0036] In a preferred embodiment of the present invention, the residence time of the liquid phase in the gas-liquid separator is ≤30 min, preferably ≤15 min, more preferably ≤10 min, and even more preferably ≤5 min.

[0037] If the residence time is too short, the reaction will be incomplete; if the residence time is too long, caprolactam will be hydrolyzed by heat.

[0038] In a preferred embodiment of the present invention, the gas phase pressure of the ammonium sulfate crystallizer is controlled at 5 kPa to 30 kPa; preferably 10 kPa to 25 kPa; more preferably 12 kPa to 20 kPa.

[0039] Its pressure is controlled by flow regulation of the liquid jet pump connected to it; the power fluid of the jet pump is the ammonium sulfate aqueous solution from the liquid collecting tank, which sucks the gas on the top of the ammonium sulfate crystallizer through the jet pump and then returns to the liquid collecting tank.

[0040] The purpose of adjusting the crystallizer pressure is to create a low pressure environment to lower the boiling point. If the pressure is too high, the temperature cannot be controlled at 65°C and crystallization cannot occur; if the pressure is too low, the energy consumption is too high.

[0041] In a preferred embodiment of the present invention, in S4, the temperature of the ammonium sulfate crystallizer is 55-65°C.

[0042] The tubular neutralization reactor is directly connected to the gas-liquid separator, or the tubular neutralization reactor is built in the gas phase space above the gas-liquid separator.

[0043] The present invention has a different focus from the Chinese patent application with publication number CN111498869A. The main purpose of the Chinese patent application with publication number CN111498869A is to adjust the morphology of the byproduct ammonium sulfate in the caprolactam neutralization crystallization process; while the main focus of the present invention is to further save energy consumption, reduce the loss of caprolactam products, and recycle the heat value generated by the neutralization reaction.

[0044] Compared with the prior art, the present invention has the following beneficial effects:

[0045] 1. The present invention proposes a method for neutralizing and crystallizing caprolactam rearrangement liquid, which reduces the caprolactam loss, increases the temperature and pressure of the neutralization reaction, thereby producing saturated steam with a high calorific value as a by-product, and reduces the load of the vacuum pump. In the process of neutralization and crystallization of the rearrangement liquid, only one neutralization reaction device is added, and the other ammonium sulfate crystallization parts remain unchanged, thereby achieving the purpose of energy recovery and utilization at the cost of increasing the one-time equipment investment, and being able to supply steam externally to increase the benefits.

[0046] 2. The present invention designs a neutralization and crystallization device for caprolactam rearrangement liquid, which solves the problem that the hydrolysis rate of caprolactam is fast under high temperature conditions, but the gas-liquid separation takes a long time, and the viscosity of the caprolactam rearrangement liquid is high, making it difficult to integrate the neutralization reaction and gas-liquid separation into one control. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 The present invention is a method process flow chart of an embodiment of the present invention.

[0048] Figure 2 Schematic diagram of the structure of a tubular neutralization reactor in one embodiment of the present invention.

[0049] Figure 3 Schematic diagram of the structure of a gas-liquid separator in one embodiment of the present invention. DETAILED DESCRIPTION

[0050] like Figure 1-Figure 3As shown, an ammonium sulfate neutralization crystallization device includes a tubular ammonia-water mixer 1, a tubular neutralization reactor 2, an ammonium sulfate crystallizer 3, and a gas-liquid separator 4. The tubular neutralization reactor 2 adopts a Venturi type and / or static mixing tubular neutralization reactor. The tubular neutralization reactor 2 includes a central nozzle 21 and a peripheral channel 22 that converges with the central nozzle 21 at a certain angle. The liquid outlet of the tubular ammonia-water mixer 1 is connected to the liquid inlet of the central nozzle 21, the liquid inlet of the peripheral channel 22 is connected to the liquid outlet of the caprolactam rearrangement liquid, the liquid outlet of the central nozzle 21 is connected to the liquid inlet of the gas-liquid separator 4, the liquid outlet of the gas-liquid separator 4 is connected to the liquid inlet of the ammonium sulfate crystallizer 3, and the gas outlet of the gas-liquid separator 4 is connected to the gas inlet of the heat exchange device 5.

[0051] The water phase liquid outlet of the ammonium sulfate crystallizer 3 is communicated with the liquid inlet of the liquid injection pump 6 , and the liquid outlet of the liquid injection pump 6 is communicated with the liquid inlet of the liquid collecting tank 7 .

[0052] The gas-liquid separator 4 comprises a gas phase space with an upper cross-sectional area of ​​S1 and a liquid phase space with a lower cross-sectional area of ​​S2, where S1 / S2=4-10.

[0053] The tubular ammonia-water mixer 1 is a Venturi-type and / or static mixing tubular ammonia-water mixer.

[0054] During operation, gaseous ammonia and the aqueous solution containing ammonium sulfate from the liquid collecting tank enter the tubular ammonia-water mixer for mixing to generate an ammonia aqueous solution containing ammonium sulfate, and then enter the tubular neutralization reactor for neutralization reaction with fuming sulfuric acid in the caprolactam rearrangement liquid to generate ammonium sulfate and produce high-temperature steam.

[0055] The steam generated during the neutralization process is separated from the liquid phase and used as a heat source. The condensate produced is circulated back to the sump for utilization, and the liquid phase enters the ammonium sulfate crystallizer.

[0056] The liquid phase entering the ammonium sulfate crystallizer from the gas-liquid separator is rapidly cooled and crystallized and is separated into oil-water phases in the crystallizer. The oil phase is called amide oil and is sent for refining to obtain the caprolactam product; the water phase is a slurry containing ammonium sulfate crystals and is sent for solid-liquid separation to obtain ammonium sulfate solid product. The remaining mother liquor after solid-liquid separation is sent to the liquid collecting tank for recycling.

[0057] The pressure of the ammonium sulfate crystallizer is regulated by flow rate regulation of a liquid jet pump connected thereto. The power fluid of the jet pump is an aqueous solution of ammonium sulfate from a liquid collecting tank, which is sucked into the gas at the top of the ammonium sulfate crystallizer by the jet pump and then returns to the liquid collecting tank.

[0058] Example 1

[0059] 1. 5100kg / h ammonia gas at about 45°C and 4.5bar is mixed with mother liquor in a mixer to form ammonia water at about 45°C and 4.5bar, which enters the neutralization reactor. The neutralization reactor adopts a Venturi tubular neutralization reactor. Ammonia water is neutralized with 27500kg / h cyclohexanone oxime rearrangement reaction liquid at about 115°C and 6.5bar in the neutralization reactor. The reaction temperature is about 144°C and the reaction pressure is 3bar. After the neutralization reaction, the stream immediately enters the gas-liquid separator. The outlet pressure of the tubular neutralization reactor is 100kPa, the gas-liquid separator S1 / S2=4, and the liquid phase residence time is 5 minutes. After separation, 54993.3kg / h of rearrangement liquid at about 3bar and 144°C is generated after the reaction, and 14429kg / h of saturated steam with a higher calorific value of the by-product at an absolute pressure of about 3bar and a temperature of 144°C is generated. The steam heat is used and then cooled and enters the collecting tank for reuse.

[0060] 2. The liquid phase discharged from the gas-liquid separator enters the ammonium sulfate crystallizer for rapid cooling and crystallization, and oil-water separation is performed in the crystallizer at the same time. The temperature in the ammonium sulfate crystallizer is controlled at 65°C and the gas phase pressure is 12kPa. 18121.7kg / h of amide oil is separated with a purity of about 70.88%, which enters the amide refining section and is sent for refining to obtain the caprolactam finished product; its aqueous phase is a slurry containing ammonium sulfate crystals, which is sent for solid-liquid separation to obtain an ammonium sulfate solid product, and the generated solid-liquid mixture is pumped into the solid-liquid separator to generate 19678.5kg / h of ammonium sulfate product with a specification of 100%. The remaining mother liquor after solid-liquid separation is sent to the liquid collecting tank for recycling.

[0061] For our factory, the process adopts continuous operation of 330 days per year, of which one month per year is used for fixed parking equipment maintenance and emergency handling. Through the improvement of the process flow, the original energy consumption was about 11010.95kw, and the current energy consumption is about 293.3kw, which can save 84883788 kw of electricity per year.

[0062] If calculated based on Zhejiang Province's industrial electricity charging standards, the electricity cost can be saved by approximately RMB 65,000,000 each year.

[0063] Example 2: The outlet pressure of the neutralization reactor was controlled, and the temperature and pressure of the steam generated after the reaction under different conditions were detected. The results are shown in the following table.

[0064] Outlet pressure(kpa) 80 100 120 200 250 300 Generated steam temperature (℃) 101.3 107.8 113.3 129.6 137.3 143.8 Generated steam pressure (kpa) 80 100 120 200 250 300

[0065] Example 3: The flow rate ratio in the central nozzle and the small holes around the nozzle of the neutralization reactor was controlled to detect the mass fraction of residual sulfuric acid in the rearrangement liquid after the neutralization reaction under different conditions. The results are shown in the following table.

[0066] V2 / V1 0.1 0.2 0.6 1 3 6 10 Mass fraction of sulfuric acid after reaction 0.186 0.114 0.051 0 0.002 0.085 0.149

[0067] Example 4: The cross-sectional area ratio of the upper and lower sections of the gas-liquid separator was changed to detect the proportion of the obtained steam in the liquid before vaporization under different conditions, that is, the vaporization rate. The results are shown in the following table.

[0068] S1 / S2 1 2 3 4 10 15 20 Vaporization rate 10.25％ 14.52％ 18.41％ 20.78％ 20.78％ 20.78％ 20.78％

[0069] Example 5: The residence time of the liquid phase in the gas-liquid separator was controlled, and the vaporization rate and the decomposition rate of caprolactam at different residence times were detected. The results are shown in the following table.

[0070] Liquid residence time 1min 5min 10min 15min 20min 30min 40min Vaporization rate 19.84％ 20.78％ 20.78％ 20.78％ 20.78％ 20.78％ 20.78％ Caprolactam decomposition rate 0 0 0.89％ 1.73％ 2.54％ 4.62％ 5.96％

Claims

1. An ammonium sulfate neutralization crystallization device, comprising a tubular ammonia-water mixer (1), a tubular neutralization reactor (2), and an ammonium sulfate crystallizer (3), characterized in that: The invention also comprises a gas-liquid separator (4); the tubular neutralization reactor (2) is a Venturi-type neutralization reactor, a static tubular neutralization reactor or a Venturi-type and static mixed tubular neutralization reactor; the tubular neutralization reactor (2) comprises a central nozzle (21) and a peripheral channel (22) which forms a certain angle with and intersects with the central nozzle (21); the liquid outlet of the tubular ammonia-water mixer (1) is connected to the liquid inlet of the central nozzle (21); the liquid inlet of the peripheral channel (22) is connected to the liquid outlet of the caprolactam rearrangement liquid pipeline; the liquid outlet of the central nozzle (21) is connected to the liquid inlet of the gas-liquid separator (4); the liquid outlet of the gas-liquid separator (4) is connected to the liquid inlet of the ammonium sulfate crystallizer (3); and the gas outlet of the gas-liquid separator (4) is connected to the gas inlet of the heat exchange device (5).

2. The ammonium sulfate neutralization crystallization device according to claim 1, characterized in that: The water phase liquid outlet of the ammonium sulfate crystallizer (3) is communicated with the liquid inlet of the liquid injection pump (6), the liquid outlet of the liquid injection pump (6) is communicated with the liquid inlet of the liquid collecting tank (7), and the oil phase liquid outlet of the ammonium sulfate crystallizer (3) is communicated with the liquid inlet of the solid-liquid separation device (8).

3. The ammonium sulfate neutralization crystallization device according to claim 1, characterized in that: The gas-liquid separator (4) comprises a gas phase space with an upper cross-sectional area of ​​S1 and a liquid phase space with a lower cross-sectional area of ​​S2, S1 / S2=2-20, preferably S1 / S2=3-15, and more preferably S1 / S2=4-10.

4. The ammonium sulfate neutralization crystallization device according to claim 1, characterized in that: The tubular ammonia-water mixer (1) adopts a Venturi-type neutralization reactor, a static tubular neutralization reactor, or a Venturi-type and static mixed tubular neutralization reactor.

5. A neutralization crystallization method for the ammonium sulfate neutralization crystallization device according to any one of claims 1 to 4, characterized in that The following steps are involved: S1, passing ammonia gas and an aqueous solution containing ammonium sulfate into a tubular ammonia-water mixer to mix and generate an ammonia aqueous solution containing ammonium sulfate; S2, passing the aqueous ammonia solution containing ammonium sulfate obtained in S1 into the central nozzle of the tubular neutralization reactor, and passing the caprolactam rearrangement liquid containing fuming sulfuric acid into the peripheral channel of the tubular neutralization reactor to carry out a neutralization reaction; The liquid after the neutralization reaction of S3 and S2 is passed into the gas-liquid separator; The liquid separated from the liquid outlet of the gas-liquid separator in S4 and S3 is introduced into the ammonium sulfate crystallizer, and the amide oil and the water phase containing ammonium sulfate crystals are separated from the ammonium sulfate crystallizer. The steam from the gas outlet of the gas-liquid separator in S3 is introduced into the heat exchange device for use as a heat source.

6. The neutralization crystallization method according to claim 5, characterized in that The outlet pressure of the tubular neutralization reactor in S2 is 100 kPa to 300 kPa, preferably 110 kPa to 250 kPa; more preferably 120 kPa to 200 kPa.

7. The neutralization crystallization method according to claim 5, characterized in that The tubular neutralization reactor adopts a Venturi-type tubular neutralization reactor, the average flow velocity of the central nozzle of the Venturi-type tubular neutralization reactor is V1, and the average flow velocity of the peripheral channel is V2; V2 / V1=0.2~10, preferably V2 / V1=0.6~6, and further preferably V2 / V1=1.0~3.

0.

8. The neutralization crystallization method according to claim 5, characterized in that The liquid phase residence time in the gas-liquid separator is ≤30 min, preferably ≤15 min, more preferably ≤10 min, and even more preferably ≤5 min.

9. The neutralization crystallization method according to claim 5, characterized in that: The gas phase pressure of the ammonium sulfate crystallizer is controlled at 5 kPa to 30 kPa; preferably 10 kPa to 25 kPa; more preferably 12 kPa to 20 kPa.

10. The neutralization crystallization method according to claim 5, characterized in that: In S4, the ammonium sulfate crystallizer temperature is 55-65°C.

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