阅读说明：本技术 一种硫酸铵结晶方法及其装置 (Ammonium sulfate crystallization method and device thereof ) 是由 杨春和 吴燕平 于 2020-04-14 设计创作，主要内容包括：本发明公开了一种硫酸铵结晶方法及其装置,属于化工领域。该装置使用两个串联的结晶器,采用两效真空结晶工艺,第一效为中和结晶,第二效为蒸发结晶。第一效为中和结晶产生的含细小的结晶颗粒比例大的浆液,送第二效为蒸发结晶系统,得到大颗粒硫酸铵比例较大的硫酸铵。该装置充分利用气氨溶解热和硫酸和氨中和反应的中和热,并利用中和结晶器的二次蒸汽作为热源,减少循环水消耗,提高大颗粒硫酸铵的比例,同时减少己内酰胺的包裹损失。(The invention discloses an ammonium sulfate crystallization method and an ammonium sulfate crystallization device, and belongs to the field of chemical industry. The device uses two crystallizers connected in series, and adopts a double-effect vacuum crystallization process, wherein the first effect is neutralization crystallization, and the second effect is evaporation crystallization. The first effect is to neutralize the slurry produced by crystallization and containing fine crystal particles in large proportion, and the second effect is to send the slurry to an evaporative crystallization system to obtain ammonium sulfate with large proportion of large particles of ammonium sulfate. The device makes full use of the heat of solution of gas ammonia and the heat of neutralization of the neutralization reaction of sulfuric acid and ammonia, and utilizes the secondary steam of the neutralization crystallizer as a heat source, thereby reducing the consumption of circulating water, improving the proportion of large-particle ammonium sulfate and reducing the wrapping loss of caprolactam.)

1. An ammonium sulfate crystallization device is characterized by comprising a primary-effect DTB type neutralization crystallizer (1) and a secondary-effect O L SO type crystallizer (5), wherein the two crystallizers are connected in series, the output end of the top of the primary-effect DTB type neutralization crystallizer (1) is connected with the shell pass inlet of a circulating heater (4) of the secondary-effect crystallizer, the shell pass outlet of the circulating heater (4) of the secondary-effect crystallizer is connected with a vapor-liquid separation tank (8), the lower part of the vapor-liquid separation tank (8) is connected with a condensate circulating pump (23), the condensate circulating pump (23) is connected with the bottom of the DTB type neutralization crystallizer (1), the output end of the middle lower part of the primary-effect DTB type neutralization crystallizer (1) is connected with the bottom end of the primary-effect DTB type neutralization crystallizer (1) through a primary-effect circulating pump (2);

one output end at the top of the sedimentation separation area of the double-effect O L SO type crystallizer (5) is connected with the lower part of the double-effect O L SO type crystallizer (5) through a double-effect sedimentation separator (6), the other output end at the bottom of the double-effect sedimentation separator (6) is connected with a circulating heater (4) of the double-effect crystallizer through a double-effect circulating pump (7), and the output end at the top end of the circulating heater (4) of the double-effect crystallizer is connected with the input end of the upper evaporation area of the double-effect O L SO type crystallizer (5);

and the discharge at the output end of the bottom of the primary-effect DTB type neutralization crystallizer (1) is conveyed to a secondary-effect O L SO type crystallizer (5).

2. The ammonium sulfate crystallization apparatus of claim 1, wherein: and the discharged material at the output end of the bottom of the primary-effect DTB type neutralization crystallizer (1) is conveyed to an inlet of a secondary-effect circulating pump (7).

3. The ammonium sulfate crystallization device as claimed in claim 1, characterized in that the output from the bottom of the primary DTB type neutralization crystallizer (1) is connected to the upper evaporation chamber of the secondary O L SO type crystallizer and/or to the bottom of the secondary O L SO type crystallizer.

4. The ammonium sulfate crystallization apparatus of claim 1, wherein: the lower part of the single-effect DTB type neutralization crystallizer (1) is also sequentially provided with an input end of water (17), an input end of rearrangement liquid (18) and an input end of ammonia gas (19), and the input ends of the water (17), the rearrangement liquid (18) and the ammonia gas (19) are all lifted into the guide barrel.

5. The ammonium sulfate crystallization apparatus of claim 1, wherein: a stirrer is arranged in an inner guide barrel of the single-effect DTB type neutralization crystallizer (1).

6. The ammonium sulfate crystallization apparatus of claim 1, wherein: one output end of the top of the sedimentation separation area of the first-effect DTB type neutralization crystallizer (1) is connected through a first-effect sedimentation separator (3), caprolactam on the upper part of the first-effect sedimentation separator (3) is recovered through a pipeline (16), one part of ammonium sulfate aqueous solution on the lower part of the first-effect sedimentation separator (3) is sent to the bottom of the neutralization crystallizer (1), and the other part of ammonium sulfate aqueous solution is sent to an inlet of a first-effect circulating pump (2).

7. The ammonium sulfate crystallization device as claimed in claim 1, characterized in that the output end of the bottom end of the double-effect O L SO type crystallizer (5) is respectively connected with a centrifuge (9), a dryer (10) and a sieving machine (11).

8. The ammonium sulfate crystallization device as claimed in claim 7, characterized in that the centrifuge (9) is connected with a mother liquor tank (12), the bottom of the mother liquor tank (12) is connected with a mother liquor circulating pump (13), and the outlet of the mother liquor circulating pump (13) is respectively connected with the bottom of the two-effect O L SO type crystallizer (5), the inlet of the two-effect circulating pump (7) and the outlet of the one-effect circulating pump (2).

9. A method for realizing ammonium sulfate crystallization by using the device is characterized in that: the method comprises the following steps that 1) rearrangement liquid from a rearrangement system of a caprolactam device enters a guide cylinder of a one-effect DTB neutralization crystallizer through a nozzle on a distributor of the one-effect DTB type neutralization crystallizer, ammonia gas outside a boundary area is sent into a flow cylinder at the lower part of the guide cylinder of the one-effect DTB neutralization crystallizer, neutralization reaction is carried out on the rearrangement liquid and sulfuric acid in the one-effect DTB neutralization crystallizer under the conditions that the pressure is 15 kPa-95 kPa and the temperature is 60-95 ℃, an ammonium sulfate solution in the guide cylinder absorbs heat released by the neutralization reaction and ammonia dissolution, part of materials are vaporized, the density is reduced, a difference between the internal density and the external density of the guide cylinder is formed, and the solution in the guide cylinder is pushed to rise under the combined action of a stirrer inside the guide cylinder;

2) after the liquid of the primary DTB neutralization crystallizer is discharged from the guide shell, settling separation is carried out, the caprolactam solution is positioned at the upper layer in a settling area, the middle layer is dilute ammonium sulfate, and the lower layer is concentrated ammonium sulfate; part of ammonium sulfate solution is taken out from the middle layer and the lower layer and is pumped to the bottom of the first-effect DTB neutralization crystallizer by a first-effect circulating pump, and the density of the ammonium sulfate solution is less than that of the solution at the bottom of the first-effect DTB neutralization crystallizer, so that the ammonium sulfate at the bottom of the first-effect DTB neutralization crystallizer is in a fluidized state; the fluidization process enhances the chance of collision of the crystals;

3) the ammonium sulfate-containing crystal material from the bottom of the primary DTB neutralization crystallizer automatically flows to an inlet of a secondary-effect circulating pump, is pumped by a pump to be heated and then is sent to an evaporation chamber of a secondary-effect O L SO type crystallizer or is sent to the bottom of the secondary-effect O L SO type crystallizer, the operating pressure of the secondary-effect O L SO type crystallizer is 10-50 KPa, the temperature is 50-65 ℃, secondary steam generated from the primary-effect DTB neutralization crystallizer and the top of the secondary-effect O L SO type circulating heater is used for heating the secondary-effect material, the secondary steam is condensed and then enters a gas-liquid separator, noncondensable gas is sent to a vacuum system, liquid condensate is sent to the primary-effect neutralization crystallizer by a condensate circulating pump to keep the water quantity balance and dissolve microcrystals, or is sent to an intermittent cleaning crystallizer demister by a condensate circulating pump, or is sent to flush a centrifugal machine by the condensate circulating pump, or is sent to flush an instrument pipeline by the condensate circulating pump to flush the instrument pipeline, or;

4) the inside of the double-effect O L SO type crystallizer is divided into an evaporation chamber and a crystallization settling zone, circulating liquid is sent to the evaporation chamber for gas-liquid separation, gas is sent to a vacuum system, liquid is concentrated ammonium sulfate solution and enters the bottom of the crystallization settling zone from a guide shell, the density of the circulating liquid is smaller than that of thick slurry at the bottom of the settling zone, the thick slurry zone at the bottom of the double-effect is in a fluidized state, the fluidized state can accelerate the collision and growth of crystals, the material in the thick slurry zone is sent to a centrifuge for separation, mother liquid is sent to a mother liquid tank and is sent to the bottom of the double-effect O L SO type crystallizer by a pump, an inlet of a double-effect circulating pump and an outlet of a single-effect circulating pump, wet solid ammonium;

5) the upper part of the crystallization settling zone of the double-effect O L SO type crystallizer contains water and small ammonium sulfate particles, and part of wrapped organic matters released by dissolving and recrystallizing fine crystals are pumped out by a double-effect circulating pump and then heated by a circulating heater of the double-effect crystallizer, and then sent to an evaporation zone for evaporation and concentration, or a double-effect settling separator is arranged outside the settling zone of the double-effect crystallizer, the liquid at the lower part is separated and sent to the inlet of the double-effect circulating pump or the bottom of the double-effect O L SO type crystallizer, the organic matters at the upper part are discharged after accumulating certain materials, and part of caprolactam is recovered.

10. The method of claim 9, wherein: and (3) the solution from the upper part of the primary DTB neutralization crystallization settling zone in the step 2) enters a primary settling separator, the upper layer of the primary settling separator is a caprolactam-containing crude product and is sent to caprolactam for refining, and the middle layer and the lower layer of the primary settling separator are water and ammonium sulfate which return to the bottom of the primary DTB neutralization crystallizer or are sent to a primary circulating pump and enter the primary DTB neutralization crystallizer for recrystallization.

The technical field is as follows:

the invention relates to the field of chemical devices, in particular to an ammonium sulfate crystallization method and an ammonium sulfate crystallization device applied to a caprolactam device.

Background

Caprolactam is an important organic chemical raw material and is mainly used for producing nylon 6 engineering plastics and nylon 6 fibers. The nylon 6 engineering plastic is mainly used as components and assemblies of automobiles, ships, electronic appliances, industrial machinery and daily consumer goods, the nylon 6 fiber can be made into textiles, industrial yarns, yarns for carpets and the like, besides, the caprolactam can also be used for producing antiplatelet drugs, producing laurocapram and the like, and the application is very wide. The main production methods of caprolactam include:

1. cyclohexanone-hydroxylamine process

The method is a main method for producing caprolactam by using cyclohexanone as a raw material. The production process routes of hydroxylamine are three, namely an HSO method, an HPO method and an NO method, which are respectively and briefly described as follows:

1) and HSO method (UBE method produced by Japan).

Part of the liquid ammonia is made into ammonia water, and part of the liquid ammonia is oxidized into nitrogen oxide. Absorbing sulfur dioxide (at normal temperature), nitrogen oxide and nitrogen dioxide (both at low temperature) with ammonia water in sequence to obtain hydroxylamine disulfonate, and heating and hydrolyzing to obtain hydroxylamine sulfate.

The obtained hydroxylamine sulfate reacts with cyclohexanone to generate cyclohexanone oxime. The cyclohexanone oxime is subjected to Beckmann molecular rearrangement in fuming sulfuric acid to obtain a caprolactam crude product, and then the caprolactam crude product is subjected to refining means such as extraction, ion exchange, thin film distillation and the like to obtain a finished product.

2) The HPO process (see DSM, the Netherlands for example).

Nitric oxide and nitrogen dioxide produced by ammoxidation are absorbed by the mixed solution of phosphoric acid, and the absorbed mixed solution reacts with hydrogen in the presence of a catalyst to produce hydroxylamine hydrochloride.

The hydroxylamine phosphate reacts with cyclohexanone to generate cyclohexanone oxime, the cyclohexanone oxime undergoes Beckmann molecular rearrangement in the fuming sulfuric acid, the rearranged liquid is neutralized and crystallized, and crude caprolactam is formed after the sulfuric acid is removed. Then purifying to obtain a product caprolactam

3) NO method (example of Germany BASF method)

Nitrogen and oxygen are oxidized into nitrogen monoxide under the dilution of steam, and the nitrogen and the oxygen are introduced into sulfuric acid solution containing Pt catalyst taking active carbon as a carrier together with hydrogen, so that NO is reduced into NH₂OH and withThe sulfuric acid is combined into hydroxylamine sulfate, caprolactam is obtained through oximation and transposition, and the finished product is obtained through extraction and distillation of the crude caprolactam.

2. Toluene method (example of SNIA in Italy)

Oxidizing toluene under 1MPa at 150-178 ℃ to obtain benzoic acid, purifying and hydrogenating to obtain hexahydrobenzoic acid.

Oxidizing ammonia into nitrogen oxide, and absorbing with fuming sulfuric acid to obtain nitroso sulfuric acid. In another tower, the hexahydrobenzoic acid is absorbed by nitroso sulfuric acid, and then the crude caprolactam is obtained under the action of oleum.

After the crude caprolactam product is subjected to second-stage extraction and oxidation treatment, the crude caprolactam product is sent to a film evaporator to be evaporated to obtain a finished product.

3. Light nitrosation method (taking PNC method of Dongli corporation of Japan as an example)

Cyclohexane and nitrosyl chloride react at 20-30 ℃ under the irradiation of light, oily substances formed at the bottom of the reactor are separated out and dissolved in water, sodium carbonate is used for neutralizing until the pH value is 6 to obtain cyclohexanone oxime, and the cyclohexanone oxime is transposed to obtain caprolactam.

4、H₂O₂Aminooximation process

The process comprises the steps of placing cyclohexanone, ammonia and 60% hydrogen peroxide in the same reactor, synthesizing cyclohexanone oxime in n-butyl alcohol (TBA) solvent through reaction under the action of a Ti-Si catalyst taking Si as a carrier, rectifying and recovering a mixture produced through the reaction through TBA, extracting cyclohexanone oxime toluene, rectifying and other processes to obtain cyclohexanone oxime, carrying out Beckmann rearrangement reaction on the cyclohexanone oxime under the action of oleum to generate crude caprolactam, extracting and distilling the crude caprolactam to obtain a finished product of caprolactam

The most of the above process technologies adopt the liquid phase rearrangement method of cyclohexanone oxime to prepare caprolactam, that is, cyclohexanone oxime undergoes molecular rearrangement in oleum to obtain crude caprolactam, and then the crude caprolactam is neutralized to remove sulfuric acid. Ammonia is generally adopted in a caprolactam device to neutralize cyclohexanone oxime to carry out molecular rearrangement in oleum to obtain sulfuric acid in crude caprolactam to generate ammonium sulfate.

At present, the rearrangement reaction of the main production process of caprolactam in China adopts a two-stage or three-stage process, and the process has no great difference. The neutralization of the rearrangement reaction liquid includes a process of neutralizing with ammonia to produce ammonium sulfate and then evaporating and crystallizing to obtain solid ammonium sulfate, and a process of neutralizing with gaseous ammonia in a vacuum crystallizer to evaporate water by using reaction heat to obtain solid ammonium sulfate. The second ammonium sulfate neutralization crystallization device utilizes the solution heat of the ammonia gas and the neutralization heat of the reaction of the ammonia and the sulfuric acid, saves the steam consumption, reduces the circulating water consumption consumed by the solution heat of the cooling gas ammonia and the neutralization heat of the reaction of the ammonia and the sulfuric acid, has certain economical efficiency, and is widely adopted in a newly-built caprolactam device.

At present, the ammonium sulfate neutralization crystallization method widely adopted in a domestic caprolactam device is to introduce rearrangement reaction liquid into a DTB type crystallizer to complete the neutralization and evaporation crystallization processes, but the inventor finds that the ammonium sulfate neutralization crystallization process has the following problems by adopting a single DTB type ammonium sulfate neutralization crystallizer in the prior art:

a) the single DTB type ammonium sulfate neutralization crystallizer widely adopted at present has the advantages that the solid particles of the ammonium sulfate are mostly 0.6-1.2 mm, the proportion of the ammonium sulfate crystals with the solid particle size of more than 2mm is less than 10%, generally about 5%, the proportion of the ammonium sulfate crystals with the solid particle size of more than 2mm is less, the solid particle size is small, but the price of the large-particle ammonium sulfate crystals is about 30-45 dollars/t higher than that of the small-particle ammonium sulfate crystals, namely about 200-300 RMB/t of ammonium sulfate, the ammonium sulfate yield of a caprolactam device is large, about 1.5t of ammonium sulfate/t of caprolactam, and the economical efficiency of the ammonium sulfate crystallization device is poor due to the process technology of small ammonium sulfate large particle proportion.

b) At present, the caprolactam content in the ammonium sulfate solid is usually about 0.1 percent by weight, which causes caprolactam loss, and a space for reducing the caprolactam loss exists in the technology;

c) the single DTB type ammonium sulfate neutralizes the secondary steam generated at the top of the crystallization tower, and generally adopts circulating cooling water for cooling, so that the energy is not reasonably utilized, and the consumption of the cooling water is relatively large.

Disclosure of Invention

The invention aims to provide an ammonium sulfate crystallization method and a device thereof aiming at the technical problems, the device fully utilizes the solution heat of gas ammonia and the neutralization heat of the neutralization reaction of sulfuric acid and ammonia, and utilizes secondary steam of a neutralization crystallizer as a heat source, thereby reducing the consumption of circulating water, improving the proportion of large-particle ammonium sulfate and reducing the loss of caprolactam.

The purpose of the invention can be realized by the following technical scheme:

an ammonium sulfate crystallization device comprises a primary-effect DTB type neutralization crystallizer and a secondary-effect O L SO type crystallizer, wherein the two crystallizers are connected in series, the output end of the top of the primary-effect DTB type neutralization crystallizer is connected with the shell pass inlet of a circulating heater of the secondary-effect crystallizer, the shell pass outlet of the circulating heater of the secondary-effect crystallizer is connected with a vapor-liquid separation tank, the lower part of the vapor-liquid separation tank is connected with a condensate circulating pump, and the condensate circulating pump is connected with the bottom of the primary-effect DTB type neutralization crystallizer;

one output end at the top of the sedimentation separation area of the double-effect O L SO type crystallizer is connected with a double-effect sedimentation separator, one output end at the bottom of the double-effect sedimentation separator is connected with the lower part of the double-effect O L SO type crystallizer, and the other output end at the bottom of the double-effect sedimentation separator is connected with a circulating heater of the double-effect crystallizer through a double-effect circulating pump;

and the discharge at the output end of the bottom of the primary-effect DTB type neutralization crystallizer is conveyed to a secondary-effect O L SO type crystallizer.

The technical scheme of the invention is as follows: and the discharged material at the output end of the bottom of the primary-effect DTB type neutralization crystallizer is conveyed to an inlet of a secondary-effect circulating pump.

In the technical scheme of the invention, the discharged materials at the output end of the bottom of the primary-effect DTB type neutralization crystallizer are conveyed to the upper evaporation chamber of the secondary-effect O L SO type crystallizer to be connected, and/or the bottom of the secondary-effect O L SO type crystallizer is connected.

In other embodiments: the discharge of the output end of the bottom of the first-effect DTB type neutralization crystallizer is conveyed to a centrifugal mother liquor tank, the two-effect crystallizer is pumped by the mother liquor tank, and the centrifugal mother liquor tank material is mainly conveyed to the first-effect DTB type neutralization crystallizer due to the need of balancing the water volume evaporated by the first effect.

The technical scheme of the invention is as follows: the lower part of the one-effect DTB type neutralization crystallizer is also sequentially provided with a water input end, a rearrangement liquid input end and an ammonia gas input end, and the water input end, the rearrangement liquid input end and the ammonia gas input end all rise into the guide barrel.

The technical scheme of the invention is as follows: the upper part of the vapor-liquid separation tank is connected with a vacuum system.

The technical scheme of the invention is as follows: one output end of the top of the settling separation area of the primary-effect DTB type neutralization crystallizer is connected through a primary-effect settling separator, caprolactam on the upper portion of the primary-effect settling separator is recovered through a pipeline, one part of ammonium sulfate aqueous solution on the lower portion of the primary-effect settling separator is sent to the bottom of the neutralization crystallizer, and the other part of ammonium sulfate aqueous solution is sent to an inlet of a primary-effect circulating pump.

In the technical scheme of the invention, the output end of the bottom end of the double-effect O L SO type crystallizer is respectively connected with a centrifugal machine, a dryer and a sieving machine.

According to the technical scheme, the centrifuge is connected with a mother liquor tank, the bottom of the mother liquor tank is connected with a mother liquor circulating pump, and an outlet of the mother liquor circulating pump is respectively connected with the bottom of a double-effect O L SO type crystallizer, an inlet of the double-effect circulating pump and an outlet of a single-effect circulating pump.

The technical scheme of the invention is as follows: the method comprises the following steps:

1) the rearrangement liquid from a rearrangement system of a caprolactam device enters a guide cylinder of a first-effect DTB neutralization crystallizer through a nozzle on a distributor of the first-effect DTB type neutralization crystallizer, ammonia gas outside a boundary area is sent to the lower part of the guide cylinder of the first-effect DTB neutralization crystallizer, neutralization reaction is carried out on the rearrangement liquid and sulfuric acid in the first-effect DTB neutralization crystallizer under the conditions that the pressure is about 15 kPa-95 kPa and the temperature is 60-95 ℃, the ammonium sulfate solution in the guide cylinder absorbs heat released by the neutralization reaction and ammonia dissolution, partial materials are vaporized, the density is reduced, a density difference between the inside and the outside of the guide cylinder is formed, and the solution in the guide cylinder is pushed to rise under the combined action of a stirrer inside the guide cylinder;

2) after the liquid of the primary DTB neutralization crystallizer is discharged from the guide shell, settling separation is carried out, the caprolactam solution is positioned at the upper layer in a settling area, the middle layer is dilute ammonium sulfate, and the lower layer is concentrated ammonium sulfate; part of ammonium sulfate solution is taken out from the middle layer and the lower layer and is pumped to the bottom of the first-effect DTB neutralization crystallizer by a first-effect circulating pump, and the density of the ammonium sulfate solution is less than that of the solution at the bottom of the first-effect DTB neutralization crystallizer, so that the ammonium sulfate at the bottom of the first-effect DTB neutralization crystallizer is in a fluidized state; the fluidization process enhances the chance of collision of the crystals;

3) the ammonium sulfate-containing crystal material from the bottom of the primary DTB neutralization crystallizer automatically flows to an inlet of a secondary-effect circulating pump, is pumped by a pump to be heated and then is sent to an evaporation chamber of a secondary-effect O L SO type crystallizer or is sent to the bottom of the secondary-effect O L SO type crystallizer, the operating pressure of the secondary-effect O L SO type crystallizer is 10-50 KPa, the temperature is 50-65 ℃, secondary steam generated from the primary-effect DTB neutralization crystallizer and the top of the secondary-effect O L SO type circulating heater is used for heating the secondary-effect material, the secondary steam is condensed and then enters a gas-liquid separator, noncondensable gas is sent to a vacuum system, liquid condensate is sent to the primary-effect neutralization crystallizer by a condensate circulating pump to keep the water quantity balance and dissolve microcrystals, or is sent to an intermittent cleaning crystallizer demister by a condensate circulating pump, or is sent to flush a centrifugal machine by the condensate circulating pump, or is sent to flush an instrument pipeline by the condensate circulating pump to flush the instrument pipeline, or;

4) the inside of the double-effect O L SO type crystallizer is divided into an evaporation chamber and a crystallization settling zone, circulating liquid is sent to the evaporation chamber for gas-liquid separation, gas is sent to a vacuum system, liquid is concentrated ammonium sulfate solution and enters the bottom of the crystallization settling zone from a guide shell, the density of the circulating liquid is smaller than that of thick slurry at the bottom of the settling zone, the thick slurry zone at the bottom of the double-effect is in a fluidized state, the fluidized state can accelerate the collision and growth of crystals, the material in the thick slurry zone is sent to a centrifuge for separation, mother liquid is sent to a mother liquid tank and is sent to the bottom of the double-effect O L SO type crystallizer by a pump, an inlet of a double-effect circulating pump and an outlet of a single-effect circulating pump, wet solid ammonium;

5) the upper part of the crystallization settling zone of the double-effect O L SO type crystallizer contains water and small ammonium sulfate particles, and part of wrapped organic matters released by dissolving and recrystallizing fine crystals are pumped out by a double-effect circulating pump and then heated by a circulating heater of the double-effect crystallizer, and then sent to an evaporation zone for evaporation and concentration, or a double-effect settling separator is arranged outside the settling zone of the double-effect crystallizer, the liquid at the lower part is separated and sent to the inlet of the double-effect circulating pump or the bottom of the double-effect O L SO type crystallizer, the organic matters at the upper part are discharged after accumulating certain materials, and part of caprolactam is recovered.

The technical scheme of the invention is as follows: and (3) the solution from the upper part of the primary DTB neutralization crystallization settling zone in the step 2) enters a primary settling separator, the upper layer of the primary settling separator is a caprolactam-containing crude product and is sent to caprolactam for refining, and the middle layer and the lower layer of the primary settling separator are water and ammonium sulfate which return to the bottom of the primary DTB neutralization crystallizer or are sent to a primary circulating pump and enter the primary DTB neutralization crystallizer for recrystallization.

The device uses two crystallizers connected in series, and adopts a double-effect vacuum crystallization process, wherein the first effect is neutralization crystallization, and the second effect is evaporation crystallization. The first effect is to neutralize the slurry which is generated by crystallization and contains fine crystal particles with large proportion, and the slurry is sent to a second effect evaporation crystallization system to obtain ammonium sulfate with large proportion of large particles of ammonium sulfate. Meanwhile, the encapsulation loss of caprolactam is reduced.

In the invention, the first effect neutralization crystal is a DTB type crystallizer, an inner guide flow barrel is arranged in the crystallizer, and a stirrer is arranged in the inner guide flow barrel. The stirrer functions as follows: on the one hand, the heat transfer and the mass transfer in the guide cylinder are accelerated, the local overheating and the uniform mixing of reaction materials are avoided, on the other hand, the ammonium sulfate crystals in the inner guide cylinder are pushed to move upwards, and the crystals are reduced or disappear under the combined action of stirring and the heat generated by the ammonia solution heat and neutralization in the inner guide cylinder, so that the large ammonium sulfate particles are prevented from being formed in the caprolactam-containing area of the crystallizer, and the loss of caprolactam is reduced.

In the technical scheme of the invention, the first-effect neutralization crystallizer integrates two process processes of neutralization and evaporative crystallization into one crystallizer to complete, water in the ammonium sulfate solution is evaporated by utilizing the ammonia gas solution heat and the neutralization reaction heat, a heating heat source is provided for the second-effect crystallizer, cooling water required for cooling secondary steam at the top of the first-effect neutralization crystallizer is reduced, and the energy-saving effect is achieved.

Part of dilute ammonium sulfate solution is taken out from the middle layer of the sedimentation separation area of the lower part of the first-effect neutralization crystallizer, and is delivered to the bottom of the first-effect DTB neutralization crystallizer by using a first-effect circulating pump, the density of the dilute ammonium sulfate is less than that of the solution at the bottom of the first-effect DTB neutralization crystallizer, so that the ammonium sulfate at the bottom of the first-effect DTB neutralization crystallizer is in a fluidized state, the collision chance among crystals is enhanced, the ammonium sulfate crystals grow, and the small circulation amount is set by the first-effect circulating pump, so that the ammonium.

In the technical scheme of the invention, the crystallization, sedimentation and separation area of the double-effect O L SO type crystallizer is divided into two layers, wherein the upper layer is mainly an ammonium sulfate aqueous solution containing small ammonium sulfate crystals and a slurry area containing a small amount of caprolactam and other organic matters and being ammonium sulfate, the lower layer is mainly an ammonium sulfate aqueous solution containing ammonium sulfate crystals and being a concentrated slurry area of ammonium sulfate, and the materials in the concentrated slurry area and the slurry area of ammonium sulfate are in a fluidized state.

The upper layer is mainly ammonium sulfate aqueous solution containing ammonium sulfate small crystals, the ammonium sulfate aqueous solution is pumped out of a circulating heater of a double-effect crystallizer by a double-effect circulating pump to be heated, part of fine ammonium sulfate crystals are dissolved and sent to an evaporation zone for evaporation and concentration, a double-effect sedimentation separator can be arranged outside a sedimentation zone of the double-effect crystallizer, part of liquid at the top of the upper layer of a crystallization and sedimentation separation zone of the double-effect O L SO type crystallizer is introduced into the double-effect sedimentation separator to separate organic matters such as caprolactam, the liquid at the lower part of the double-effect sedimentation separator is sent to an inlet of the double-effect circulating pump or the bottom of the double-effect O L SO type crystallizer, and the organic matters at the upper.

In the invention, the second-effect crystallizer is internally provided with the inner guide barrel, the stirrer is not arranged in the inner guide barrel, the ammonium sulfate crystals in the guide barrel move from top to bottom, the crystals become larger and reach the bottom of the sedimentation separation area of the crystallizer, and because a large amount of materials with small density are introduced into the bottom of the sedimentation separation area, the materials in the sedimentation separation area are in a fluidized state, so that the collision of the crystals is enhanced, and large ammonium sulfate particles are formed.

The invention has the beneficial effects that:

a) the large-particle ammonium sulfate generated by the OS L O type evaporative crystallizer has the characteristic of large particle ammonium sulfate, the proportion of the large-particle ammonium sulfate is improved, the proportion of the ammonium sulfate crystals with particle size of more than 2mm is more than 30 percent, usually 40 percent, the proportion of the large-particle ammonium sulfate crystals is far more than 5 percent by adopting the crystallization process, and the economical efficiency is obviously improved;

b) the external circulation heater of the OS L O type evaporative crystallizer eliminates fine crystals and the recrystallization process, and reduces the wrapping loss of caprolactam in the crystallization process.

c) Secondary steam generated at the top of the primary-effect DTB neutralization crystallizer is used as a circulating heater of the secondary-effect crystallizer to heat secondary-effect materials, extra steam is not needed, consumption of a heat source is saved, and circulating water consumption is reduced.

d) The large-flow double-effect circulating pump is used to make the ammonium sulfate at the bottom of the double-effect crystallizer in a fluidized state, so that the fluidization is enhanced, the collision of ammonium sulfate crystals and the timely elimination of fine ammonium sulfate crystals are enhanced, the specific gravity of large ammonium sulfate crystals is effectively improved, and the average particle size of the crystals is improved.

Drawings

FIG. 1 is a schematic structural diagram of an ammonium sulfate crystallization device according to the present invention.

The system comprises a primary-effect DTB type neutralization crystallizer, a primary-effect circulating pump, a primary-effect sedimentation separator, a secondary-effect crystallizer circulating heater, a secondary-effect O L SO type crystallizer, a secondary-effect sedimentation separator, a secondary-effect circulating pump, a gas-liquid separation tank, a centrifugal machine, a dryer, a screening machine, a mother liquid tank, a mother liquid circulating pump, a small-particle ammonium sulfate, a large-particle ammonium sulfate, a CP L crude product, water, a heavy liquid discharge, ammonia gas, a condensate, a vacuum removal system, a CP L crude product and a condensate circulating pump, wherein 1 is a primary-effect DTB type neutralization crystallizer, 2 is a primary-effect circulating pump, 3 is a primary-effect sedimentation separator, 4 is a secondary-effect sedimentation separator, 7 is a secondary-effect circulating pump, 8 is a gas.

Note that CP L is an abbreviation for caprolactam.

The specific implementation mode is as follows:

the invention is further illustrated by the following examples, without limiting the scope of the invention:

referring to fig. 1, an ammonium sulfate crystallization device comprises a first-effect DTB type neutralization crystallizer 1 and a second-effect O L SO type crystallizer 5 which are connected in series, wherein the output end of the top of the first-effect DTB type neutralization crystallizer 1 is connected with the shell pass inlet of a second-effect crystallizer circulating heater 4, the shell pass outlet of the second-effect crystallizer circulating heater 4 is connected with a vapor-liquid separation tank 8, the lower part of the vapor-liquid separation tank 8 is connected with a condensate circulating pump 23, the condensate circulating pump 23 is connected with the bottom of the DTB type neutralization crystallizer 1, the output end of the middle lower part of the first-effect DTB type neutralization crystallizer 1 is connected with the bottom end of the first-effect DTB type neutralization crystallizer 1 through a first-effect circulating pump 2;

one output end at the top of the sedimentation separation area of the double-effect O L SO type crystallizer 5 is connected with a double-effect sedimentation separator 6, one output end at the bottom of the double-effect sedimentation separator 6 is connected with the lower part of the double-effect O L SO type crystallizer 5, and the other output end at the bottom of the double-effect sedimentation separator 6 is connected with a circulating heater 4 of the double-effect crystallizer through a double-effect circulating pump 7;

and the discharge at the output end of the bottom of the primary-effect DTB type neutralization crystallizer 1 is conveyed to a secondary-effect O L SO type crystallizer 5.

And the discharged material at the output end of the bottom of the primary-effect DTB type neutralization crystallizer 1 is conveyed to the inlet of a secondary-effect circulating pump 7.

Or the discharge of the output end of the bottom of the primary-effect DTB type neutralization crystallizer 1 is conveyed to the upper evaporation chamber of the secondary-effect O L SO type crystallizer to be connected, and/or the bottom of the secondary-effect O L SO type crystallizer is connected.

The lower part of the single-effect DTB type neutralization crystallizer 1 is also sequentially provided with an input end of water 17, an input end of rearrangement liquid 18 and an input end of ammonia gas 19, and the input ends of the water 17, the rearrangement liquid 18 and the ammonia gas 19 are all lifted into the guide barrel.

A stirrer is arranged in an inner guide barrel of the primary-effect DTB type neutralization crystallizer 1.

One output end of the top of the sedimentation separation area of the first-effect DTB type neutralization crystallizer 1 is connected through a first-effect sedimentation separator 3, caprolactam on the upper part of the first-effect sedimentation separator 3 is recovered through a pipeline 16, one part of ammonium sulfate aqueous solution on the lower part of the first-effect sedimentation separator 3 is sent to the bottom of the neutralization crystallizer 1, and the other part of the ammonium sulfate aqueous solution is sent to the inlet of a first-effect circulating pump 2.

The output end of the bottom end of the double-effect O L SO type crystallizer 5 is respectively connected with a centrifuge 9, a dryer 10 and a sieving machine 11.

The centrifuge 9 is connected with a mother liquor tank 12, the bottom of the mother liquor tank 12 is connected with a mother liquor circulating pump 13, and the outlet of the mother liquor circulating pump 13 is respectively connected with the bottom of the double-effect O L SO type crystallizer 5, the inlet of the double-effect circulating pump 7 and the outlet of the first-effect circulating pump 2.