MVR deamination crystallization system for phosphogypsum resource production of gypsum

Abstract

The utility model discloses a kind of MVR deamination crystallization system for phosphogypsum resource production gypsum, including heating unit, crystallizer, filter, absorption tower and steam supply unit, heating unit includes steam heater, ammonia heater and forced circulation pump, crystallizer is used to separate gas-liquid after heating and produce ammonia and liquid phase to dissolved solution, the circulating material discharge port of crystallizer and ammonia outlet are connected with ammonia heater, filter is connected with the crystallization discharge port of crystallizer by crystallization discharge pump, absorption tower is connected with the cooling liquid discharge port and incondensable gas discharge port of ammonia heater, steam supply unit includes absorption heat exchanger and flash tank;By combining with MVR technology, secondary steam produced by system evaporation system is re-compressed and utilized, and the heat generated by ammonia absorption and heat release is utilized to reduce, greatly reduce the operating energy consumption of equipment in the process of phosphogypsum resource treatment, save operating cost, improve the feasibility of phosphogypsum resource technology.

Description

Technical Field

[0001] This utility model relates to the field of gypsum production technology, specifically to an MVR deammoniation crystallization system for the resource-based production of gypsum from phosphogypsum. Background Technology

[0002] Phosphate gypsum, a byproduct of phosphate rock production, is a solid waste that is inevitably generated during the wet processing of phosphate rock (i.e., using acids such as sulfuric acid and nitric acid to decompose phosphate rock to produce core phosphate chemical products such as phosphoric acid and ammonium phosphate compound fertilizers). It is also one of the largest byproducts in the global phosphate chemical industry in terms of output and the highest level of attention to resource utilization.

[0003] Its formation is deeply tied to phosphate rock processing, and its properties are significantly affected by the quality of phosphate rock and production processes. It also possesses the dual characteristics of "environmental risk" and "resource attributes".

[0004] After being processed through a series of processes such as crushing, dissolving, and pressure filtration, phosphogypsum produces a mixed solution mainly containing calcium sulfate and ammonium sulfate. Due to the increased ammonium content in the solution, the solubility of calcium sulfate increases. The ammonium in the solution is removed by evaporation, thereby reducing the solubility of calcium sulfate and causing calcium sulfate to crystallize out. The ammonia gas (secondary steam) generated by evaporation is heated and pressurized by a compressor and then enters a forced circulation evaporator as a heat source to provide the heat required for ammonia removal from the raw materials. Because the ammonia concentration in the secondary steam is relatively high (about 30%), the secondary steam cannot be completely condensed, with a condensation rate of only about 35% and a low ammonia content in the condensate of only about 4%. This results in a large amount of non-condensable ammonia gas being discharged from the evaporation and crystallization system, causing a heat imbalance in the system. External heat supplementation is required, resulting in high system energy consumption and increased operating costs.

[0005] Based on the above problems, this utility model proposes an MVR deammoniation crystallization system for the resource-based production of gypsum from phosphogypsum that can solve the above problems. Utility Model Content

[0006] The purpose of this invention is to provide an MVR deammoniation crystallization system for the resource-based production of gypsum from phosphogypsum, in order to solve the problems mentioned in the background art.

[0007] To achieve the above objectives, this utility model provides the following technical solution: an MVR deammoniation crystallization system for the resource-based production of gypsum from phosphogypsum, comprising:

[0008] The heating unit includes a steam heater, an ammonia heater, and a forced circulation pump, wherein the forced circulation pump is used to deliver the solution to be heated by the steam heater;

[0009] A crystallizer is used to separate the gas and liquid phases of a heated solution to produce ammonia and liquid phase. The circulating material outlet and ammonia outlet of the crystallizer are connected to the ammonia heater, and the ammonia generated is used to exchange heat with the circulating material in the ammonia heater.

[0010] The filter is connected to the crystallization outlet of the crystallizer via a crystallization discharge pump;

[0011] The absorption tower is connected to the coolant outlet and non-condensable gas outlet of the ammonia heater, and the absorption tower is also connected to the mother liquor outlet of the filter.

[0012] The steam supply unit includes an absorption heat exchanger and a flash tank. The absorption heat exchanger connects the flash tank and the absorption tower. Pure water exchanges heat with the mother liquor that absorbs ammonia in the absorption heat exchanger and then enters the flash tank. The steam outlet of the flash tank is connected to the steam inlet of the steam heater through a steam compressor unit.

[0013] As a preferred technical solution, the outlet of the forced circulation pump is connected to the solution inlet of the steam heater, the inlet of the forced circulation pump is connected to a feed pipe, and the inlet of the forced circulation pump is connected to the circulating material outlet of the ammonia heater.

[0014] As a preferred technical solution, an ammonia compressor is provided between the crystallizer and the ammonia heater, and the ammonia compressor is used to increase the temperature and pressure of the ammonia entering the ammonia heater.

[0015] As a preferred technical solution, the coolant outlet of the ammonia heater is connected to a dilute ammonia tank, and the dilute ammonia tank is connected to the absorption tower via a dilute ammonia pump.

[0016] As a preferred technical solution, the condensate drain of the steam heater is connected to a condensate tank, and the condensate tank is connected to the flash tank via a condensate pump.

[0017] Compared with the prior art, the beneficial effects of this utility model are:

[0018] By combining with MVR technology, the secondary steam generated by the system's evaporation system is recompressed and utilized, and the heat generated by ammonia absorption and exothermic processes is utilized, which greatly reduces the operating energy consumption of the equipment during the phosphogypsum resource utilization process, saves operating costs, and improves the feasibility of the phosphogypsum resource utilization process. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the overall structure;

[0020] In the diagram: 1. Steam heater; 2. Ammonia heater; 3. Crystallizer; 4. Ammonia compressor; 5. Crystallization discharge pump; 6. Forced circulation pump; 7. Dilute ammonia tank; 8. Dilute ammonia pump; 9. Condensate tank; 10. Condensate pump; 11. First vacuum pump; 12. Filter; 13. Absorption tower; 14. Absorption circulation pump; 15. Absorption heat exchanger; 16. Pure water circulation pump; 17. Flash tank; 18. Steam compressor unit; 19. Second vacuum pump. Detailed Implementation

[0021] The following is a detailed description, with reference to the accompanying drawings, of an MVR deammoniation crystallization system for the resource-based production of gypsum from phosphogypsum according to embodiments of the present disclosure. To make the objectives, technical solutions, and advantages of this disclosure clearer, the technical solutions in the embodiments of this disclosure will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this disclosure.

[0022] Therefore, the following detailed description of embodiments of the present disclosure provided in conjunction with the accompanying drawings is not intended to limit the scope of the claimed disclosure, but merely to illustrate selected embodiments of the disclosure. All other embodiments obtained by those skilled in the art based on the embodiments of the present disclosure without inventive effort are within the scope of protection of the present disclosure.

[0023] Please see Figure 1

[0024] Example 1

[0025] The heating unit includes a steam heater 1, an ammonia heater 2, and a forced circulation pump 6. The steam heater 1 is connected to a first vacuum pump 11. The forced circulation pump 6 is used to transport the solution heated by the steam heater 1. The outlet of the forced circulation pump 6 is connected to the solution inlet of the steam heater 1. The inlet of the forced circulation pump 6 is connected to a feed pipe. The inlet of the forced circulation pump 6 is connected to the circulating material outlet of the ammonia heater 2.

[0026] The crystallizer 3 is connected to the solution outlet of the steam heater 1. The phosphogypsum solution is transported to the steam heater 1 through the forced circulation pump 6. The phosphogypsum solution is heated after exchanging heat with steam in the steam heater 1. After the heated solution enters the crystallizer 3, gas-liquid separation occurs, and ammonia and liquid phase are generated.

[0027] In this process, the liquid phase crystallizes and grows crystals in the crystallizer 3, and the circulating material (clear liquid) is separated out. The circulating material re-enters the ammonia heater 2, while the generated ammonia gas is heated and pressurized by the ammonia compressor 4 and enters the ammonia heater 2. This allows the generated ammonia gas to exchange heat with the circulating material in the ammonia heater 2. The ammonia gas after heat exchange produces dilute ammonia water and uncondensed ammonia gas. The circulating material after heat exchange is then re-entered into the steam heater 1 by the forced circulation pump 6 for heating.

[0028] The filter 12 is connected to the crystallization outlet of the crystallizer 3 via the crystallization discharge pump 5. The filter 12 is a belt filter. The crystal slurry generated by crystallization and crystal growth in the crystallizer 3 is transported to the filter 12 via the crystallization discharge pump 5 for solid-liquid separation. The separated solid is calcium sulfate dihydrate (gypsum), and the separated liquid is the mother liquor.

[0029] The absorption tower 13 is connected to a second vacuum pump 19. The absorption tower 13 is connected to the coolant outlet and non-condensable gas outlet of the ammonia heater 2. Specifically, the coolant outlet of the ammonia heater 2 is connected to a dilute ammonia tank 7. The dilute ammonia tank 7 is connected to the absorption tower 13 through a dilute ammonia pump 8.

[0030] The absorption tower 13 is connected to the mother liquor outlet of the filter 12, and the mother liquor absorbs dilute ammonia water and uncondensed ammonia gas in the absorption tower 13.

[0031] The steam supply unit includes an absorption heat exchanger 15 and a flash tank 17. The absorption heat exchanger 15 is connected to the flash tank 17 and the absorption tower 13. Pure water exchanges heat with the mother liquor that absorbs ammonia in the absorption heat exchanger 15 and then enters the flash tank 17. The steam outlet of the flash tank 17 is connected to the steam inlet of the steam heater 1 through the steam compressor unit 18. The absorption heat exchanger 15 is connected to the absorption tower 13 through the absorption circulation pump 14. The absorption heat exchanger 15 is connected to the flash tank 17 through the pure water circulation pump 16.

[0032] As the temperature of the mother liquor increases during the ammonia absorption process, the mother liquor exchanges heat with pure water in the absorption heat exchanger 15 during the ammonia absorption process, which can reduce the temperature of the mother liquor and increase the mother liquor's ability to continue absorbing ammonia. After the mother liquor absorbs ammonia and reaches the designed ammonium concentration, it is discharged to the front-end gypsum washing and dissolving section for recycling.

[0033] The pure water after heat exchange is then subjected to adiabatic flash evaporation in flash tank 17. The secondary steam generated by flash evaporation enters steam compressor unit 18. After being heated and pressurized by steam compressor unit 18, the secondary steam enters steam heater 1 to heat the circulating material.

[0034] Example 2

[0035] The heating unit includes a steam heater 1, an ammonia heater 2, and a forced circulation pump 6. The steam heater 1 is connected to a first vacuum pump 11. The forced circulation pump 6 is used to transport the solution heated by the steam heater 1. The outlet of the forced circulation pump 6 is connected to the solution inlet of the steam heater 1. The inlet of the forced circulation pump 6 is connected to a feed pipe. The inlet of the forced circulation pump 6 is connected to the circulating material outlet of the ammonia heater 2.

[0036] The crystallizer 3 is connected to the solution outlet of the steam heater 1. The phosphogypsum solution is transported to the steam heater 1 through the forced circulation pump 6. The phosphogypsum solution is heated after exchanging heat with steam in the steam heater 1. After the heated solution enters the crystallizer 3, gas-liquid separation occurs, and ammonia and liquid phase are generated.

[0037] In this process, the liquid phase crystallizes and grows crystals in the crystallizer 3, and the circulating material (clear liquid) is separated out. The circulating material re-enters the ammonia heater 2, while the generated ammonia gas is heated and pressurized by the ammonia compressor 4 and enters the ammonia heater 2. This allows the generated ammonia gas to exchange heat with the circulating material in the ammonia heater 2. The ammonia gas after heat exchange produces dilute ammonia water and uncondensed ammonia gas. The circulating material after heat exchange is then re-entered into the steam heater 1 by the forced circulation pump 6 for heating.

[0038] The filter 12 is connected to the crystallization outlet of the crystallizer 3 via the crystallization discharge pump 5. The filter 12 is a belt filter. The crystal slurry generated by crystallization and crystal growth in the crystallizer 3 is transported to the filter 12 via the crystallization discharge pump 5 for solid-liquid separation. The separated solid is calcium sulfate dihydrate (gypsum), and the separated liquid is the mother liquor.

[0039] The absorption tower 13 is connected to a second vacuum pump 19. The absorption tower 13 is connected to the coolant outlet and non-condensable gas outlet of the ammonia heater 2. Specifically, the coolant outlet of the ammonia heater 2 is connected to a dilute ammonia tank 7. The dilute ammonia tank 7 is connected to the absorption tower 13 through a dilute ammonia pump 8.

[0040] The absorption tower 13 is connected to the mother liquor outlet of the filter 12, and the mother liquor absorbs dilute ammonia water and uncondensed ammonia gas in the absorption tower 13.

[0041] The steam supply unit includes an absorption heat exchanger 15 and a flash tank 17. The absorption heat exchanger 15 is connected to the flash tank 17 and the absorption tower 13. Pure water exchanges heat with the mother liquor that absorbs ammonia in the absorption heat exchanger 15 and then enters the flash tank 17. The steam outlet of the flash tank 17 is connected to the steam inlet of the steam heater 1 through the steam compressor unit 18. The absorption heat exchanger 15 is connected to the absorption tower 13 through the absorption circulation pump 14. The absorption heat exchanger 15 is connected to the flash tank 17 through the pure water circulation pump 16.

[0042] As the temperature of the mother liquor increases during the ammonia absorption process, the mother liquor exchanges heat with pure water in the absorption heat exchanger 15 during the ammonia absorption process, which can reduce the temperature of the mother liquor and increase the mother liquor's ability to continue absorbing ammonia. After the mother liquor absorbs ammonia and reaches the designed ammonium concentration, it is discharged to the front-end gypsum washing and dissolving section for recycling.

[0043] The pure water after heat exchange is then subjected to adiabatic flash evaporation in flash tank 17. The secondary steam generated by flash evaporation enters steam compressor unit 18. After being heated and pressurized by steam compressor unit 18, the secondary steam enters steam heater 1 to heat the circulating material.

[0044] The condensate drain of the steam heater 1 is connected to a condensate tank 9. The condensate tank 9 is connected to the flash tank 17 via a condensate pump 10. After the secondary steam exchanges heat with the steam heater 1, it produces condensate which enters the flash tank 17 and can be reheated, thereby achieving system water balance and heat balance.

[0045] Working principle:

[0046] Evaporation and crystallization: The phosphogypsum solution is pumped into a forced circulation pipeline, and then circulated into the steam heater 1 by the forced circulation pump 6. After being heated by steam, it enters the crystallizer 3 for gas-liquid separation. Ammonia flash evaporates and enters the ammonia compressor 4. The liquid phase enters the crystallizer 3 for crystallization and crystal growth, and the circulating material (clear liquid) is separated. The circulating material is circulated into the steam heater 1 and the ammonia heater 2 by the forced circulation pump 6, and then enters the crystallizer 3 for gas-liquid separation. This cycle of evaporation is repeated to achieve the designed evaporation rate.

[0047] Ammonia compression: In the crystallizer 3, the total ammonium content of the solution decreases due to the evaporation of ammonia, which in turn reduces the solubility of calcium sulfate and causes calcium sulfate crystals to form. The evaporated ammonia enters the ammonia compressor 4. After being heated and pressurized by the compressor, it enters the ammonia heater 2 to exchange heat with the circulating material. The condensed dilute ammonia water is collected in the dilute ammonia water tank 7 and sent to the absorption tower 13 by the dilute ammonia water pump 8. After absorbing ammonia, it is discharged from the system. The uncondensed ammonia in the ammonia heater 2 also enters the absorption tower 13.

[0048] Solid-liquid separation: After crystal growth, the crystal slurry is sent to the filter through the crystal discharge pump 5 for solid-liquid separation. The solid is calcium sulfate dihydrate (gypsum), and the liquid phase is the mother liquor. After the mother liquor is evaporated to remove ammonia and reduce the ammonia concentration, it enters the absorption tower 13 to continue absorbing ammonia.

[0049] Ammonia absorption: The mother liquor and ammonia are absorbed in a countercurrent cycle in absorption tower 13. After the mother liquor absorbs ammonia and reaches the designed ammonium concentration, it is discharged to the front-end gypsum washing and dissolving section for recycling.

[0050] Pure water flash evaporation and steam compression: During ammonia absorption, the mother liquor temperature rises and exchanges heat with pure water through absorption heat exchanger 15. This heats the pure water while lowering the mother liquor temperature, facilitating continued ammonia absorption. The heated pure water then circulates into flash tank 17 for adiabatic flash evaporation. The secondary steam generated from the flash evaporation enters steam compressor unit 18. The un-flashed pure water is sent to the absorption heat exchanger via pure water circulation pump 16 to circulate and exchange heat with the mother liquor. After being heated and pressurized by steam compressor unit 18, the secondary steam enters steam heater 1 to heat the circulating material, causing it to evaporate ammonia. The steam condensate is collected in condensate tank 9 and returned to flash tank 17 via condensate pump 10, thus achieving system water and heat balance.

[0051] By combining with MVR (Mechanical Vapor Recompression) technology, the secondary steam generated by the system's evaporation system is recompressed and utilized, and the heat generated by ammonia absorption and exothermic processes is utilized, significantly reducing the operating energy consumption of the equipment during the phosphogypsum resource utilization process, saving operating costs, and improving the feasibility of the phosphogypsum resource utilization process. A comparison of energy consumption is made using a real-world case study of a project with a processing capacity of 48 t / h; detailed parameters are shown in the table below.

[0052]

[0053] surface

[0054] As can be seen from Table 1, this technology reduces the overall operating cost by 816 yuan / h compared to the traditional single-effect deammoniation crystallization process, which means that the overall operating cost is reduced by 62.4%.

[0055] Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. An MVR deammoniation crystallization system for the resource-based production of gypsum from phosphogypsum, characterized in that, include: The heating unit includes a steam heater, an ammonia heater, and a forced circulation pump, wherein the forced circulation pump is used to deliver the solution to be heated by the steam heater; A crystallizer is used to separate the gas and liquid phases of a heated solution to produce ammonia and liquid phase. The circulating material outlet and ammonia outlet of the crystallizer are connected to the ammonia heater, and the ammonia generated is used to exchange heat with the circulating material in the ammonia heater. The filter is connected to the crystallization outlet of the crystallizer via a crystallization discharge pump; The absorption tower is connected to the coolant outlet and non-condensable gas outlet of the ammonia heater, and the absorption tower is also connected to the mother liquor outlet of the filter. The steam supply unit includes an absorption heat exchanger and a flash tank. The absorption heat exchanger connects the flash tank and the absorption tower. Pure water exchanges heat with the mother liquor that absorbs ammonia in the absorption heat exchanger and then enters the flash tank. The steam outlet of the flash tank is connected to the steam inlet of the steam heater through a steam compressor unit.

2. The MVR deammoniation crystallization system for the resource-based production of gypsum from phosphogypsum according to claim 1, characterized in that, The outlet of the forced circulation pump is connected to the solution inlet of the steam heater, the inlet of the forced circulation pump is connected to a feed pipe, and the inlet of the forced circulation pump is connected to the circulating material outlet of the ammonia heater.

3. The MVR deammoniation crystallization system for the resource-based production of gypsum from phosphogypsum according to claim 1, characterized in that, An ammonia compressor is provided between the crystallizer and the ammonia heater, and the ammonia compressor is used to increase the temperature and pressure of the ammonia entering the ammonia heater.

4. The MVR deammoniation crystallization system for the resource-based production of gypsum from phosphogypsum according to claim 1, characterized in that, The coolant outlet of the ammonia heater is connected to a dilute ammonia tank, which is connected to the absorption tower via a dilute ammonia pump.

5. The MVR deammoniation crystallization system for the resource-based production of gypsum from phosphogypsum according to claim 1, characterized in that, The condensate drain of the steam heater is connected to a condensate tank, and the condensate tank is connected to the flash tank via a condensate pump.

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