Multi-effect evaporation concentration cooling crystallization ammonium chloride preparation system and method

Abstract

The invention discloses a multi-effect evaporation concentration cooling crystallization ammonium chloride preparation system and method. The system comprises an ammonium chloride solution stock solution tank; a stock solution pump is arranged on the ammonium chloride stock solution tank; a neutralization reaction unit; the neutralization reaction unit comprises a neutralization absorption tower with a three-layer filler structure; the neutralization absorption tower is connected with the ammonium chloride solution stock solution tank through a pipeline; a tail gas treatment unit; the reaction unit is connected with the neutralization reaction unit; the tail gas treatment unit comprises an acid pickling tower, and a water washing tower is arranged on the acid pickling tower; a triple-effect evaporation and concentration unit; the I-effect evaporator is connected with the stock solution pump through a pipeline; a crystal packaging unit; the ammonium chloride preparation system has the beneficial effects that the gradient evaporation design of the triple-effect evaporation and concentration unit is combined with the vacuum condensation system to realize gradient utilization of steam heat energy, so that the ammonium chloride preparation system integrating high efficiency, energy conservation, environmental protection, standard reaching, high product purity and stable operation is formed, and the overall production efficiency can be effectively improved.

Description

Technical Field

[0001] The present invention relates to a preparation system and method for ammonium chloride by multi-effect evaporation concentration, cooling and crystallization. Background Art

[0002] At present, during the process of promoting product diversification, fertilizer production enterprises generally face the problem of by-product disposal. Taking compound fertilizer production enterprises as an example, the ammonia water by-produced by the synthetic ammonia plant and the hydrochloric acid by-produced by the potassium sulfate plant are in a long-term backlog state due to high storage costs, high transportation risks, and limited market sales. Traditional treatment methods mostly adopt low-price external sales or neutralization and discharge, which not only cause waste of resources, but also pose potential environmental compliance risks. How to achieve efficient resource utilization of such acid-base by-products has become a key bottleneck restricting the cost reduction, efficiency improvement and green transformation of enterprises.

[0003] Although the existing ammonium chloride preparation process can neutralize ammonia substances and hydrochloric acid to convert them into fertilizer-grade ammonium chloride, there are still significant defects in industrial applications: 1. The neutralization reaction mostly uses a single-stage spray tower, with low gas-liquid mass transfer efficiency, resulting in a high ammonia escape rate and excessive ammonia concentration in the tail gas, and subsequent complex purification devices need to be configured; 2. In the evaporation concentration link, single-effect evaporation is often used, with a high single steam consumption, and high-concentration ammonium chloride solution is prone to scale on the heating surface, and frequent shutdowns for cleaning are required. In view of this, the present invention proposes a preparation system and method for ammonium chloride by multi-effect evaporation concentration, cooling and crystallization to solve the above problems. Summary of the Invention

[0004] The purpose of the present invention is to provide a preparation system and method for ammonium chloride by multi-effect evaporation concentration, cooling and crystallization to solve the problems raised in the above background art.

[0005] To achieve the above purpose, the present invention provides the following technical solutions: A preparation system for ammonium chloride by multi-effect evaporation concentration, cooling and crystallization, comprising: An ammonium chloride solution stock solution tank; a stock solution pump is arranged on the ammonium chloride solution stock solution tank; A neutralization reaction unit; the neutralization reaction unit includes a neutralization absorption tower with a three-layer packing structure; the neutralization absorption tower is connected to the ammonium chloride solution stock solution tank through a pipeline; A tail gas treatment unit; connected to the neutralization reaction unit; the tail gas treatment unit includes an acid washing tower, and a water washing tower is arranged on the acid washing tower; A three-effect evaporation concentration unit; the three-effect evaporation concentration unit includes an I-effect evaporator, a II-effect evaporator, and a III-effect evaporator connected in sequence; the I-effect evaporator is connected to the stock solution pump through a pipeline; Crystallization packaging unit; the crystallization packaging unit includes a thickener and a centrifuge, and a crystallization conveying pipeline is arranged between the thickener and the centrifuge; the thickener is connected to the III-effect evaporator through a pipeline; the centrifuge is a horizontal two-stage piston pusher centrifuge; a packaging machine is arranged at the outlet of the centrifuge; Wherein, the gas-phase channels of the I-effect evaporator, the II-effect evaporator, and the III-effect evaporator are sequentially connected through pipelines, the II-effect evaporator and the III-effect evaporator are connected to a vacuum condensation system, the bottoms of the I-effect evaporator, the II-effect evaporator, and the III-effect evaporator are connected to an accident tank through pipelines, the ammonium chloride solution stock tank is connected to the accident tank through a pipeline, and an accident tank pump is arranged on the pipeline between the ammonium chloride solution stock tank and the accident tank.

[0006] As an improvement of the above technical solution, the neutralization absorption tower sequentially includes a first packing layer, a second packing layer, and a third packing layer from bottom to top; The first packing layer is used for the neutralization of gaseous ammonia and hydrochloric acid, the second packing layer is used for the neutralization of ammonia water and hydrochloric acid, and the third packing layer is used for mist coalescence; A demister is arranged at the top of the third packing layer, and the demister is made of a composite structure material of carbon steel and polypropylene; A top tail gas discharge port is arranged at the top of the neutralization absorption tower.

[0007] As an improvement of the above technical solution, a bottom liquid collecting tank is arranged at the bottom of the neutralization absorption tower, and the neutralization absorption tower sequentially has a gaseous ammonia inlet pipeline, an ammonia water inlet pipeline, and a hydrochloric acid inlet pipeline from bottom to top; The gaseous ammonia inlet pipeline is arranged below the first packing layer, the ammonia water inlet pipeline is arranged below the second packing layer, and the hydrochloric acid inlet pipeline is arranged below the third packing layer.

[0008] As an improvement of the above technical solution, the bottom of the pickling tower is connected to the top tail gas discharge port of the neutralization absorption tower through a pipeline, and a qualified tail gas discharge port is arranged at the top of the water washing tower; A pickling tail gas outlet is arranged at the bottom of the pickling tower, and a hydrochloric acid sprayer is arranged in the pickling tower; An absorption tower circulation pump is arranged between the neutralization absorption tower and the pickling tail gas outlet of the pickling tower.

[0009] As an improvement of the above technical solution, the I-effect evaporator is provided with an I-effect evaporation heater connected through a pipeline, and an I-effect evaporation circulating liquid pump is arranged between the I-effect evaporation heater and the I-effect evaporator; The II-effect evaporator is provided with a II-effect evaporation heater connected through a pipeline, and a II-effect evaporation circulating liquid pump is arranged between the II-effect evaporation heater and the II-effect evaporator; The III-effect evaporator is provided with a III-effect evaporation heater connected by a pipeline, and a III-effect evaporation circulating liquid pump is arranged between the III-effect evaporation heater and the III-effect evaporator.

[0010] As an improvement of the above technical solution, the I-effect evaporation heater uses I-effect steam as a heat source, and the temperature of the I-effect steam is 110°C ± 5°C; The II-effect evaporation heater uses II-effect steam as a heat source, and the temperature of the I-effect steam is 95°C ± 5°C; The III-effect evaporation heater uses III-effect steam as a heat source, and the temperature of the I-effect steam is 80°C ± 5°C.

[0011] As an improvement of the above technical solution, the vacuum condensation system includes a vacuum housing, a vacuum generator is arranged inside the vacuum housing, an acidic condensate tank is also connected by a pipeline on the vacuum housing, and an acidic liquid output pump is arranged on the acidic condensate tank; The gas-phase channels of the II-effect evaporation heater, the III-effect evaporation heater and the III-effect evaporator are all connected to the vacuum generator; A clear liquid circulation tank is connected by a pipeline to the centrifuge, a clear liquid circulation pump is connected by a pipeline to the clear liquid circulation tank, and the clear liquid circulation pump is connected to the pipeline between the III-effect evaporator and the III-effect evaporation circulating liquid pump.

[0012] A usage method of a multi-effect evaporation concentration cooling crystallization ammonium chloride preparation system includes the following steps: S1. Neutralization reaction: Gaseous ammonia is introduced from below the first packing layer of the neutralization absorption tower, ammonia water and hydrochloric acid are respectively sprayed from above the first packing layer and the second packing layer, the reaction temperature is controlled at 80 - 110°C, ammonium chloride solution is generated and stored in the ammonium chloride solution stock tank; S2. Tail gas treatment: In S1, the tail gas passes through the top tail gas discharge port of the neutralization absorption tower, and is sequentially treated by hydrochloric acid spraying in the pickling tower and water washing in the water washing tower. The treated ammonium-containing solution returns to the neutralization reaction unit, and at the same time, the water washing mixed liquid is sent out by a pump. S3. Three-effect evaporation concentration In S1, the generated ammonium chloride solution is introduced into the ammonium chloride solution stock tank and sent to the three-effect evaporation concentration unit by the stock solution pump, and is sequentially subjected to three-stage concentration of I-effect flash evaporation (110°C ± 5°C), II-effect flash evaporation (95°C ± 5°C), and III-effect flash evaporation (80°C ± 5°C). The evaporation pressure gradients of each effect are I-effect -0.02 MPa, II-effect -0.05 MPa, and III-effect -0.08 Mpa; S4. Cooling crystallization After S3 is completed, a concentrated solution is formed, and the concentrated solution is introduced into a thickener, and crystallized at 50°C ± 5°C in the thickener. After centrifugal separation, the finished product is obtained, and the mother liquor is heated and returned to the III-effect evaporator for further concentration.

[0013] As an improvement of the above technical solution, in the S3, the vacuum degree of the II-effect evaporator of the triple-effect evaporation concentration unit is maintained at -0.06 to -0.04 Mpa, and the vacuum degree of the III-effect evaporator is maintained at -0.09 to -0.07 Mpa.

[0014] As an improvement of the above technical solution, after the S4 is completed, when the triple-effect evaporation concentration unit needs to be cleaned, all the materials in the triple-effect evaporation concentration unit are discharged into the accident tank, and after the treatment is completed, they are sent into the ammonium chloride solution stock tank through the accident tank pump.

[0015] Compared with the prior art, the beneficial effects of the present invention are: Through the gradient evaporation design of the triple-effect evaporation concentration unit and the combination of the vacuum condensation system to realize the cascade utilization of steam thermal energy to reduce energy consumption; the neutralization absorption tower with a three-layer packing structure is used to complete the neutralization of gaseous ammonia-hydrochloric acid, the reaction of ammonia water-hydrochloric acid and the mist capture in stages, and cooperate with the tail gas synergistic treatment of the pickling tower and the water washing tower to realize the efficient conversion of gaseous ammonia and the tail gas discharge up to the standard; through the optimization of the crystallization separation of the thickener and the centrifuge, industrial grade ammonium chloride is produced; at the same time, the linkage design of the accident tank and the stock solution pump ensures a high recovery rate of materials when the system fails, and finally forms an ammonium chloride preparation system integrating high efficiency and energy saving, environmental protection compliance, high purity of products and stable operation, which can effectively improve the overall production efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a process schematic diagram of the present invention; Figure 2 It is a structural schematic diagram of the neutralization absorption tower of the present invention.

[0017] In the figure: 10, pickling tower; 11, water washing tower; 12, absorption tower circulation pump; 13, up-to-standard tail gas discharge port; 20, neutralization absorption tower; 21, bottom liquid collection tank of the tower; 22, first packing layer; 23, second packing layer; 24, third packing layer; 25, demister; 26, top tail gas discharge port; 27, hydrochloric acid inlet pipe; 28, ammonia water inlet pipe; 29, gaseous ammonia inlet pipe; 30, ammonium chloride solution stock solution tank; 31, stock solution pump; 40, I-effect evaporator; 41, I-effect evaporation heater; 42, II-effect evaporator; 43, II-effect evaporation heater; 44, III-effect evaporator; 45, III-effect evaporation heater; 46, I-effect evaporation circulation liquid pump; 47, II-effect evaporation circulation liquid pump; 48, III-effect evaporation circulation liquid pump; 50, thickener; 51, crystallization conveying pipeline; 60, centrifuge; 70, clear liquid circulation tank; 71, clear liquid circulation pump; 80, packaging machine; 90, vacuum condensation system; 91, vacuum housing; 92, acidic condensate tank; 93, acidic liquid output pump. Detailed implementation manners

[0018] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0019] Embodiment: As Figure 1-2 shown, this embodiment proposes an ammonium chloride preparation system for multi-effect evaporation concentration, cooling and crystallization, including: Ammonium chloride solution stock solution tank 30; a stock solution pump 31 is arranged on the ammonium chloride solution stock solution tank 30; Neutralization reaction unit; the neutralization reaction unit includes a neutralization absorption tower 20 with a three-layer packing structure; the neutralization absorption tower 20 is connected to the ammonium chloride solution stock solution tank 30 through a pipeline; Tail gas treatment unit; connected to the neutralization reaction unit; the tail gas treatment unit includes a pickling tower 10, and a water washing tower 11 is arranged on the pickling tower 10; Three-effect evaporation concentration unit; the three-effect evaporation concentration unit includes an I-effect evaporator 40, a II-effect evaporator 42, and a III-effect evaporator 44 connected in sequence; the I-effect evaporator 40 is connected to the stock solution pump 31 through a pipeline; Crystallization packaging unit; the crystallization packaging unit includes a thickener 50 and a centrifuge 60, and a crystallization conveying pipeline 51 is arranged between the thickener 50 and the centrifuge 60; the thickener 50 is connected to the III-effect evaporator 44 through a pipeline; the centrifuge 60 is a horizontal two-stage piston pusher centrifuge; a packaging machine 80 is arranged at the outlet of the centrifuge 60; Among them, the gas-phase channels of the I-effect evaporator 40, the II-effect evaporator 42, and the III-effect evaporator 44 are sequentially connected through pipelines. The II-effect evaporator 42 and the III-effect evaporator 44 are connected to a vacuum condensation system 90. The bottoms of the I-effect evaporator 40, the II-effect evaporator 42, and the III-effect evaporator 44 are connected to an accident tank through pipelines. The ammonium chloride solution stock tank 30 is connected to the accident tank through a pipeline, and an accident tank pump is arranged on the pipeline between the ammonium chloride solution stock tank 30 and the accident tank.

[0020] In this embodiment, when producing ammonium chloride solution, gaseous ammonia is introduced into the neutralization reaction unit, and the by-product ammonia water and hydrochloric acid of the enterprise are introduced into the neutralization reaction unit. After that, ammonium chloride solution is generated through neutralization reaction and stored in the ammonium chloride solution stock tank 30. Then, the ammonium chloride solution is evaporated and concentrated by the triple-effect evaporation concentration unit to form a concentrated solution, and the crystallization packaging unit performs crystallization packaging treatment; Through the gradient evaporation design of the triple-effect evaporation concentration unit and in combination with the vacuum condensation system 90, the cascade utilization of steam thermal energy is realized to reduce energy consumption; the neutralization absorption tower 20 with a three-layer packing structure is used to complete the neutralization of gaseous ammonia-hydrochloric acid, the reaction of ammonia water-hydrochloric acid, and the mist trapping in sections, and cooperate with the tail gas co-treatment of the pickling tower 10 and the water washing tower 11 to achieve efficient conversion of gaseous ammonia and meet the tail gas emission standards; through the optimization of the crystallization separation of the thickener 50 and the centrifuge 60, industrial-grade ammonium chloride is produced; at the same time, the linkage design of the accident tank and the stock solution pump 31 ensures a high recovery rate of materials in case of system failure. Finally, an ammonium chloride preparation system integrating high efficiency and energy saving, environmental protection compliance, high-purity products, and stable operation is formed, which can effectively improve the overall production efficiency.

[0021] Specifically, the neutralization absorption tower 20 sequentially includes a first packing layer 22, a second packing layer 23, and a third packing layer 24 from bottom to top; The first packing layer 22 is used for the neutralization of gaseous ammonia and hydrochloric acid, the second packing layer 23 is used for the neutralization of ammonia water and hydrochloric acid, and the third packing layer 24 is used for mist coalescence; A demister 25 is arranged at the top of the third packing layer 24, and the demister 25 is made of a composite structure material of carbon steel and polypropylene; A top tail gas discharge port 26 is arranged at the top of the neutralization absorption tower 20.

[0022] In this embodiment, through the segmented design of the gas ammonia-hydrochloric acid neutralization in the first packing layer 22 and the ammonia water-hydrochloric acid neutralization in the second packing layer 23, the staged neutralization reaction of the gas-phase and liquid-phase ammonia sources is realized, which can effectively improve the gas-liquid mass transfer efficiency, the conversion rate of gaseous ammonia, and the reaction rate of ammonia water neutralization, and effectively avoid the problem of local supersaturated crystallization caused by reaction backmixing; The third packing layer 24 adopts corrugated coalescing packing, which is used to improve the gas-liquid separation efficiency. Combined with the top CS+PP composite structure demister 25, it can resist corrosion in a strong acidic environment to improve the overall service life; Of course, the vertical integrated design of the first packing layer 22, the second packing layer 23, the third packing layer 24 and the demister 25 enables the neutralization absorption tower 20 to complete the functions of neutralization of gas-phase / liquid-phase ammonia sources, removal of reaction heat, and gas-liquid separation in a single tower, reducing the equipment height and broadening the operating flexibility range.

[0023] Specifically, a bottom liquid collecting tank 21 is arranged at the bottom of the neutralization absorption tower 20. The neutralization absorption tower 20 is successively provided with a gaseous ammonia inlet pipe 29, an ammonia water inlet pipe 28, and a hydrochloric acid inlet pipe 27 from bottom to top; The gaseous ammonia inlet pipe 29 is arranged below the first packing layer 22, the ammonia water inlet pipe 28 is arranged below the second packing layer 23, and the hydrochloric acid inlet pipe 27 is arranged below the third packing layer 24.

[0024] In this case, spray heads are connected to both the ammonia water inlet pipe 28 and the hydrochloric acid inlet pipe 27.

[0025] In this embodiment, by arranging the gaseous ammonia inlet pipe 29 at the bottom of the first packing layer 22, the ammonia water inlet pipe 28 below the second packing layer 23, and the hydrochloric acid inlet pipe 27 below the third packing layer 24, a three-stage countercurrent contact reaction zone is formed to realize the three-stage reaction intensification of the primary neutralization of gaseous ammonia-hydrochloric acid, the secondary neutralization of unreacted gaseous ammonia-ammonia water, and the deep neutralization of excessive hydrochloric acid, so that the total neutralization efficiency is improved compared with the traditional single-stage spray tower.

[0026] Specifically, the bottom of the pickling tower 10 is connected to the top tail gas discharge port 26 of the neutralization absorption tower 20 through a pipeline, and a qualified tail gas discharge port 13 is arranged at the top of the water washing tower 11; The bottom of the pickling tower 10 is provided with a pickling tail gas outlet, and a hydrochloric acid sprayer is arranged in the pickling tower 10; An absorption tower circulation pump 12 is arranged between the neutralization absorption tower 20 and the pickling tail gas outlet of the pickling tower 10.

[0027] In this embodiment, the tail gas at the top of the neutralization absorption tower 20 is successively introduced into the hydrochloric acid spraying section of the pickling tower 10 and the water washing section of the water washing tower 11, forming a three-stage purification path of "neutralizing residual gaseous ammonia → secondary pickling reaction → water washing particle trapping". Thus, through cascaded purification, closed-loop circulation and material optimization, near-zero emission of acidic tail gas and efficient reuse of raw materials during the production process of ammonium chloride are achieved, and at the same time, the operating cost is reduced.

[0028] Specifically, the first-effect evaporator 40 is provided with a first-effect evaporation heater 41 connected by a pipeline, and a first-effect evaporation circulating liquid pump 46 is arranged between the first-effect evaporation heater 41 and the first-effect evaporator 40; The second-effect evaporator 42 is provided with a second-effect evaporation heater 43 connected by a pipeline, and a second-effect evaporation circulating liquid pump 47 is arranged between the second-effect evaporation heater 43 and the second-effect evaporator 42; The third-effect evaporator 44 is provided with a third-effect evaporation heater 45 connected by a pipeline, and a third-effect evaporation circulating liquid pump 48 is arranged between the third-effect evaporation heater 45 and the third-effect evaporator 44.

[0029] Specifically, the first-effect evaporation heater 41 uses first-effect steam as a heat source, and the temperature of the first-effect steam is 110°C ± 5°C; The second-effect evaporation heater 43 uses second-effect steam as a heat source, and the temperature of the first-effect steam is 95°C ± 5°C; The third-effect evaporation heater 45 uses third-effect steam as a heat source, and the temperature of the first-effect steam is 80°C ± 5°C.

[0030] In this embodiment, this multi-effect evaporation system solves the technical bottlenecks of low energy efficiency, easy scaling and poor stability of traditional evaporators through temperature gradient matching, forced circulation heat transfer enhancement and vacuum collaborative control, and realizes the industrial effects of reducing the steam unit consumption and increasing the annual operating rate of equipment in the production of ammonium chloride.

[0031] Specifically, the vacuum condensation system 90 includes a vacuum housing 91, a vacuum generator is arranged inside the vacuum housing 91, an acidic condensate tank 92 is also connected to the vacuum housing 91 through a pipeline, and an acidic liquid output pump 93 is arranged on the acidic condensate tank 92; The gas-phase channels of the second-effect evaporation heater 43, the third-effect evaporation heater 45 and the third-effect evaporator 44 are all connected to the vacuum generator; A clear liquid circulation tank 70 is connected to the centrifuge 60 through a pipeline, a clear liquid circulation pump 71 is connected to the clear liquid circulation tank 70 through a pipeline, and the clear liquid circulation pump 71 is connected to the pipeline between the third-effect evaporator 44 and the third-effect evaporation circulating liquid pump 48.

[0032] In this embodiment, the gas-phase channels of the second-effect evaporation heater 43, the third-effect evaporation heater 45, and the third-effect evaporator 44 are connected in series and coupled through a vacuum generator to form a gradient vacuum system, so that the boiling points of each effect are accurately matched with the solution concentration, the total evaporation efficiency of the system is improved, and the steam consumption is reduced.

[0033] A method for using a preparation system for ammonium chloride by multi-effect evaporation concentration and cooling crystallization includes the following steps: S1. Neutralization reaction: Gaseous ammonia is introduced from below the first packing layer 22 of the neutralization absorption tower 20, and ammonia water and hydrochloric acid are respectively sprayed from above the first packing layer 22 and the second packing layer 23. The reaction temperature is controlled at 80 - 110°C to generate an ammonium chloride solution, which is stored in the ammonium chloride solution stock tank 30. S2. Tail gas treatment: In S1, the tail gas passes through the top tail gas discharge port 26 of the neutralization absorption tower 20, and is sequentially subjected to hydrochloric acid spraying in the pickling tower 10 and water washing treatment in the water washing tower 11. The treated ammonium-containing solution is returned to the neutralization reaction unit, and at the same time, the water washing mixed solution is sent out through a pump body. S3. Three-effect evaporation concentration In S1, the generated ammonium chloride solution is introduced into the ammonium chloride solution stock tank 30, and is sent to the three-effect evaporation concentration unit by the stock solution pump 31, and is sequentially subjected to three-stage concentration of the first-effect flash evaporation (110°C ± 5°C), the second-effect flash evaporation (95°C ± 5°C), and the third-effect flash evaporation (80°C ± 5°C). The evaporation pressure gradient of each effect is the first effect -0.02 MPa, the second effect -0.05 MPa, and the third effect -0.08 Mpa. S4. Cooling crystallization After S3 is completed, a concentrated solution is formed, and the concentrated solution is introduced into the thickener 50, and is cooled to 50°C ± 5°C in the thickener 50 for crystallization. After centrifugal separation, the finished product is obtained, and the mother liquor is returned to the third-effect evaporator 44 for re-concentration after heating.

[0034] In this embodiment, through the staged countercurrent reaction of the neutralization absorption tower 20, the gradient flash evaporation of the three-effect evaporation concentration unit, and the pressure coordinated control of the vacuum condensation system, the unit steam consumption of the product is reduced and the purity of ammonium chloride is improved; combined with the closed-loop treatment of the tail gas of the pickling tower 10 and the water washing tower 11, the low-temperature crystallization of the thickener 50 and the recycling of the mother liquor, the utilization rate of raw materials is improved and the reduction of waste liquid discharge is achieved; the system ensures continuous and stable operation through the demister 25 and each pump body, so that the comprehensive energy consumption is reduced, and it is suitable for large-scale industrial production.

[0035] Specifically, in the S3, the vacuum degree of the second-effect evaporator 42 in the three-effect evaporation concentration unit is maintained at -0.06 to -0.04 Mpa, and the vacuum degree of the third-effect evaporator 44 is maintained at -0.09 to -0.07 Mpa.

[0036] Specifically, after the completion of S4, when the triple-effect evaporation concentration unit needs to be cleaned, all the materials in the triple-effect evaporation concentration unit are discharged into the accident tank, and after the treatment, they are sent into the ammonium chloride solution stock tank 30 through the accident tank pump.

[0037] Although the embodiments of the present invention have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A preparation system for ammonium chloride by multi-effect evaporation concentration and cooling crystallization, characterized in that: Comprising: A stock solution tank (30) for ammonium chloride solution; a stock solution pump (31) is provided on the stock solution tank (30) for ammonium chloride solution; A neutralization reaction unit; the neutralization reaction unit includes a neutralization absorption tower (20) with a three-layer packing structure; the neutralization absorption tower (20) is connected to the stock solution tank (30) for ammonium chloride solution through a pipeline; An exhaust gas treatment unit; connected to the neutralization reaction unit; the exhaust gas treatment unit includes an acid washing tower (10), and a water washing tower (11) is provided on the acid washing tower (10); A triple-effect evaporation and concentration unit; the triple-effect evaporation and concentration unit includes a first-effect evaporator (40), a second-effect evaporator (42), and a third-effect evaporator (44) connected in sequence; the first-effect evaporator (40) is connected to the stock solution pump (31) through a pipeline; A crystallization and packaging unit; the crystallization and packaging unit includes a thickener (50) and a centrifuge (60), and a crystallization conveying pipeline (51) is provided between the thickener (50) and the centrifuge (60); the thickener (50) is connected to the third-effect evaporator (44) through a pipeline; the centrifuge (60) is a horizontal two-stage piston push-feed centrifuge; a packaging machine (80) is provided at the outlet of the centrifuge (60); Wherein, the gas-phase channels of the first-effect evaporator (40), the second-effect evaporator (42), and the third-effect evaporator (44) are connected in sequence through pipelines, the second-effect evaporator (42) and the third-effect evaporator (44) are connected to a vacuum condensation system (90), the bottoms of the first-effect evaporator (40), the second-effect evaporator (42), and the third-effect evaporator (44) are connected to an accident tank through pipelines, the stock solution tank (30) for ammonium chloride solution is connected to the accident tank through a pipeline, and an accident tank pump is provided on the pipeline between the stock solution tank (30) for ammonium chloride solution and the accident tank.

2. The ammonium chloride preparation system for multi-effect evaporation concentration and cooling crystallization according to claim 1, wherein: The neutralization absorption tower (20) sequentially includes a first packing layer (22), a second packing layer (23), and a third packing layer (24) from bottom to top; The first packing layer (22) is used for the neutralization of gaseous ammonia and hydrochloric acid, the second packing layer (23) is used for the neutralization of ammonia water and hydrochloric acid, and the third packing layer (24) is used for mist coalescence; A demister (25) is provided at the top of the third packing layer (24), and the demister (25) is made of a composite structure material of carbon steel and polypropylene; A top exhaust gas discharge port (26) is provided at the top of the neutralization absorption tower (20).

3. The ammonium chloride preparation system for multi-effect evaporation concentration, cooling and crystallization according to claim 2, characterized in that: A bottom liquid collection tank (21) is provided at the bottom of the neutralization absorption tower (20), and the neutralization absorption tower (20) sequentially has a gaseous ammonia inlet pipe (29), an ammonia water inlet pipe (28), and a hydrochloric acid inlet pipe (27) from bottom to top; The gaseous ammonia inlet pipe (29) is provided below the first packing layer (22), the ammonia water inlet pipe (28) is provided below the second packing layer (23), and the hydrochloric acid inlet pipe (27) is provided below the third packing layer (24).

4. A preparation system for ammonium chloride by multi-effect evaporation concentration and cooling crystallization according to claim 2, characterized in that: The bottom of the acid washing tower (10) is connected to the top exhaust gas discharge port (26) of the neutralization absorption tower (20) through a pipeline, and a qualified exhaust gas discharge port (13) is provided at the top of the water washing tower (11); The bottom of the pickling tower (10) is provided with a pickling tail gas outlet, and a hydrochloric acid sprayer is arranged in the pickling tower (10); An absorption tower circulation pump (12) is arranged between the neutralization absorption tower (20) and the pickling tail gas outlet of the pickling tower (10).

5. A preparation system for ammonium chloride by multi-effect evaporation concentration and cooling crystallization according to claim 1, characterized in that: The first-effect evaporator (40) is provided with a first-effect evaporation heater (41) connected by a pipeline, and a first-effect evaporation circulating liquid pump (46) is arranged between the first-effect evaporation heater (41) and the first-effect evaporator (40); The second-effect evaporator (42) is provided with a second-effect evaporation heater (43) connected by a pipeline, and a second-effect evaporation circulating liquid pump (47) is arranged between the second-effect evaporation heater (43) and the second-effect evaporator (42); The third-effect evaporator (44) is provided with a third-effect evaporation heater (45) connected by a pipeline, and a third-effect evaporation circulating liquid pump (48) is arranged between the third-effect evaporation heater (45) and the third-effect evaporator (44).

6. The ammonium chloride preparation system for multi-effect evaporation concentration, cooling and crystallization according to claim 5, wherein: The first-effect evaporation heater (41) uses first-effect steam as a heat source, and the temperature of the first-effect steam is 110°C ± 5°C; The second-effect evaporation heater (43) uses second-effect steam as a heat source, and the temperature of the first-effect steam is 95°C ± 5°C; The third-effect evaporation heater (45) uses third-effect steam as a heat source, and the temperature of the first-effect steam is 80°C ± 5°C.

7. A preparation system for ammonium chloride by multi-effect evaporation concentration, cooling and crystallization according to claim 5, characterized in that: The vacuum condensation system (90) includes a vacuum housing (91), a vacuum generator is arranged in the vacuum housing (91), an acidic condensate tank (92) is also connected to the vacuum housing (91) through a pipeline, and an acidic liquid output pump (93) is arranged on the acidic condensate tank (92); The gas-phase channels of the second-effect evaporation heater (43), the third-effect evaporation heater (45) and the third-effect evaporator (44) are all connected to the vacuum generator; A clear liquid circulation tank (70) is connected to the centrifuge (60) through a pipeline, a clear liquid circulation pump (71) is connected to the clear liquid circulation tank (70) through a pipeline, and the clear liquid circulation pump (71) is connected to the pipeline between the third-effect evaporator (44) and the third-effect evaporation circulating liquid pump (48).

8. A method for using an ammonium chloride preparation system for multi-effect evaporation concentration and cooling crystallization according to any one of claims 1-7, characterized in that: It includes the following steps: S1. Neutralization reaction: Gaseous ammonia is introduced from below the first packing layer (22) of the neutralization absorption tower (20), ammonia water and hydrochloric acid are respectively sprayed from above the first packing layer (22) and the second packing layer (23), the reaction temperature is controlled at 80 - 110°C, ammonium chloride solution is generated and stored in the ammonium chloride solution stock tank (30); S2. Tail gas treatment: In S1, the tail gas passes through the top tail gas discharge port (26) of the neutralization absorption tower (20), and is successively subjected to hydrochloric acid spraying in the pickling tower (10) and water washing treatment in the water washing tower (11). The treated ammonium-containing solution returns to the neutralization reaction unit, and at the same time, the water washing mixed liquid is sent out through a pump. S3. Triple-effect evaporation and concentration In S1, an ammonium chloride solution is generated and introduced into the ammonium chloride solution stock tank (30), and is sent by the stock solution pump (31) to the triple-effect evaporation and concentration unit, where primary concentration is carried out through three stages of flash evaporation, namely, flash evaporation in the first effect (110°C ± 5°C), flash evaporation in the second effect (95°C ± 5°C), and flash evaporation in the third effect (80°C ± 5°C). The evaporation pressure gradient for each effect is -0.02 MPa for the first effect, -0.05 MPa for the second effect, and -0.08 MPa for the third effect. S4. Cooling crystallization After S3 is completed, a concentrated solution is formed, and the concentrated solution is introduced into the thickener (50), and is cooled to 50°C ± 5°C in the thickener (50) for crystallization. After centrifugal separation, the finished product is obtained, and the mother liquor is heated and returned to the third-effect evaporator (44) for further concentration.

9. The usage method of an ammonium chloride preparation system for multi-effect evaporation concentration, cooling and crystallization according to claim 8, characterized in that: In the said S3, the vacuum degree of the second-effect evaporator (42) of the triple-effect evaporation and concentration unit is maintained at -0.06 to -0.04 MPa, and the vacuum degree of the third-effect evaporator (44) is maintained at -0.09 to -0.07 MPa.

10. The method of using a preparation system for ammonium chloride by multi-effect evaporation concentration, cooling and crystallization according to claim 9, characterized in that: After the said S4 is completed, when the triple-effect evaporation and concentration unit needs to be cleaned, all the materials in the triple-effect evaporation and concentration unit are discharged into the accident tank, and after the treatment is completed, they are sent into the ammonium chloride solution stock tank (30) through the accident tank pump.

Images