A system for co-production of potassium nitrate and calcium magnesium nitrate in a nitric phosphate fertilizer plant
Patent Information
- Application Number
- CN202521779724.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-08-20
- Publication Date
- 2026-10-23
- Estimated Expiration
- 2035-08-20
AI Technical Summary
但在实际生产过程中，存在着磷矿的利用率较低，且产品的附加值低的缺陷
[0014]按照上述方案制成的一种硝酸磷肥装置联产硝酸钾和硝酸钙镁肥的系统，通过设置磷矿粉镁钙预脱除单元、一次酸解脱钙单元和二次脱钙及硝酸钾分离单元能够实现对磷矿粉镁的多次脱钙，以提高物料的流动性，从而便于后续过程中对硝酸磷肥的生产，进一步地，通过设置磷矿粉镁钙预脱除单元和一次酸解脱钙单元能够实现对硝酸钙镁的分离，以实现副产硝酸钙镁肥的目的，同时通过设置二次脱钙及硝酸钾分离单元，为制备硝酸钾奠定了基础；具有提高磷矿利用率和产品附加值的特点。
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Figure CN224877965U_ABST
Abstract
Description
Technical Field
[0001] This utility model belongs to the field of nitrate phosphate fertilizer production technology, specifically a system for co-producing potassium nitrate and calcium magnesium nitrate fertilizers in a nitrate phosphate fertilizer plant. Background Technology
[0002] Nitrophosphate fertilizer is a compound fertilizer produced primarily from phosphate rock. It contains both nitrogen and phosphorus, and its production process revolves around the decomposition and nutrient conversion of phosphate rock. The production principle involves using nitric acid to decompose the phosphate rock, converting the phosphorus into soluble phosphorus that can be absorbed by plants. Simultaneously, nitrogen (from nitric acid or subsequently added ammonia) is introduced, ultimately producing a compound fertilizer containing ammonium nitrate, monoammonium phosphate, and other components. Fertilizers produced in this way are characterized by comprehensive nutrient supply and wide applicability, providing both nitrogen (N) and phosphorus (P2O5) to meet the diverse needs of crop growth. They are particularly suitable for crops with high nitrogen and phosphorus requirements (such as corn and cotton) and neutral to slightly alkaline soils. However, in actual production, there are drawbacks, including low utilization of phosphate rock and low added value of the product. Utility Model Content
[0003] To overcome the above deficiencies, this utility model provides a system for the co-production of potassium nitrate and calcium magnesium nitrate fertilizers in a nitrate phosphate fertilizer plant, thereby solving the technical problems existing in the prior art.
[0004] The technical solution adopted by this utility model to solve its technical problem is:
[0005] A system for co-producing potassium nitrate and calcium magnesium nitrate fertilizers in a nitric acid phosphate fertilizer plant. The system includes a phosphate rock powder magnesium calcium pre-removal unit, which is connected to a primary acid decalcification unit. The primary acid decalcification unit is connected to a nitric acid phosphate fertilizer production unit via a secondary decalcification and potassium nitrate separation unit, which is also connected to a potassium nitrate production unit. The liquid phase channel in the phosphate rock powder magnesium calcium pre-removal unit and the solid phase channel in the primary acid decalcification unit are connected to the calcium magnesium nitrate fertilizer production unit. The phosphate rock powder magnesium calcium pre-removal unit includes at least a magnesium removal tank. The top of the magnesium removal tank is connected to a phosphate rock powder channel and a first nitric acid pipeline. The outlet of the magnesium removal tank is connected to a filter press. The liquid phase outlet of the filter press is connected to the primary acid decalcification unit, and the solid phase pipeline of the filter press is connected to the calcium magnesium nitrate fertilizer production unit.
[0006] Preferably, the primary acid decalcification unit includes an acid decalcification tank connected to the liquid phase outlet of a filter press, the acid decalcification tank is also connected to a second nitric acid pipeline, the bottom of the acid decalcification tank is connected to the inlet of a horizontal screw press, the liquid phase outlet of the horizontal screw press is connected to a freeze crystallizer, the outlet of the freeze crystallizer is connected to a first centrifuge, the solid phase outlet of the first centrifuge is connected to a secondary decalcification and potassium nitrate separation unit, and the liquid phase pipeline of the first centrifuge is connected to a calcium magnesium nitrate fertilizer production unit.
[0007] Preferably, the calcium magnesium nitrate fertilizer production unit includes a dissolving tank, on which a magnesium oxide pipe and a third nitric acid pipe are provided. The calcium magnesium nitrate outlet of the dissolving tank is connected to a neutralization tank. The neutralization tank is provided with a first ammonia gas pipe. The calcium magnesium nitrate outlet of the neutralization tank is connected to a triple-effect steam generator. The outlet of the triple-effect steam generator is connected to a calcium magnesium nitrate fertilizer storage tank through a fluidized bed granulator and a first screening and cooling machine.
[0008] Preferably, the small particle channel in the first screening and cooling machine is connected to the seed inlet of the fluidized bed granulator.
[0009] Preferably, the secondary decalcification and potassium nitrate separation unit includes a potassium nitrate reaction tank connected to the liquid phase outlet of the first centrifuge, a potassium sulfate pipeline on the potassium nitrate reaction tank, a filter connected to the potassium nitrate reaction tank, a liquid phase outlet of the filter connected to a first cooling crystallizer, an outlet of the first cooling crystallizer connected to a second centrifuge, a solid phase outlet of the second centrifuge connected to a redissolution tank, a potassium carbonate pipeline on the redissolution tank, a filter connected to the second cooling crystallizer, an outlet of the second cooling crystallizer connected to a third centrifuge, and a solid phase outlet of the third centrifuge connected to a potassium nitrate storage tank via a dryer.
[0010] Preferably, the liquid phase outlet of the third centrifuge is connected to the filtrate reuse inlet of the redissolution tank.
[0011] Preferably, the liquid phase outlet of the second centrifuge is connected to the first inlet of the tubular reactor, the second inlet of the tubular reactor is connected to the fourth nitric acid pipeline, the third inlet of the tubular reactor is connected to the second ammonia gas pipeline, the outlet of the tubular reactor is connected to the flash tank, the liquid phase outlet of the flash tank is connected to the first heat exchange channel of the two-stage evaporator, the outlet of the first heat exchange channel of the two-stage evaporator is connected to the mixing tank, the outlet of the mixing tank is connected to the granulation tower, and the outlet of the granulation tower is connected to the nitric acid phosphate fertilizer warehouse through the second screening cooler; the mixing tank is equipped with a potassium salt pipeline and an impurity pipeline connected to the impurity outlet of the filter.
[0012] Preferably, the process steam pipeline of the flash evaporator is connected to the second heat exchange channel of the two-stage evaporator, and the steam pipeline is connected to the condensate inlet of the redissolution tank through the third heat exchange channel of the two-stage evaporator.
[0013] Preferably, the solid phase outlet of the filter is connected to the scrubber, and the outlet of the scrubber is connected to the industrial gypsum warehouse through the dryer; the top of the scrubber is provided with a clean water pipe, and the washing water pipe at the bottom of the scrubber is connected to the liquid phase inlet of the first cooling crystallizer; the insoluble matter outlet of the horizontal screw press is connected to the soil conditioner storage tank.
[0014] A system for co-producing potassium nitrate and calcium magnesium nitrate fertilizers, manufactured according to the above scheme, achieves multiple decalcifications of magnesium phosphate rock powder by setting up a magnesium-calcium pre-removal unit, a primary acid decalcification unit, and a secondary decalcification and potassium nitrate separation unit. This improves the flowability of the material, facilitating the subsequent production of phosphate nitrate fertilizer. Furthermore, the magnesium-calcium pre-removal unit and the primary acid decalcification unit enable the separation of calcium magnesium nitrate, achieving the goal of producing calcium magnesium nitrate fertilizer as a byproduct. Simultaneously, the secondary decalcification and potassium nitrate separation unit lays the foundation for potassium nitrate preparation. This system features improved phosphate rock utilization and increased product added value. Attached Figure Description
[0015] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0016] Figure 1 This is a schematic diagram of the structure of this utility model.
[0017] In the diagram: 1. Demagnesium removal tank; 2. Phosphate rock powder channel; 3. First nitric acid pipeline; 4. Filter press; 5. Acid hydrolysis tank; 6. Second nitric acid pipeline; 7. Horizontal screw press; 8. Freezing crystallizer; 9. First centrifuge; 10. Dissolving tank; 11. Magnesium oxide pipeline; 12. Third nitric acid pipeline; 13. Neutralization tank; 14. First ammonia gas pipeline; 15. Triple-effect steam purifier; 16. Fluidized bed granulator; 17. First screening cooler; 18. Calcium magnesium nitrate fertilizer storage tank; 19. Potassium nitrate reaction tank; 20. Potassium sulfate pipeline; 21. Filter; 22. First cooling crystallizer; 23. Second centrifuge; 24. Redissolving tank; 25. Carbonic acid 26. Potassium pipeline; 27. Filter; 28. Second cooling crystallizer; 29. Third centrifuge; 30. Dryer; 31. Potassium nitrate storage tank; 32. Tubular reactor; 33. Fourth nitric acid pipeline; 34. Second ammonia gas pipeline; 35. Flash evaporator; 36. Two-stage evaporator; 37. Mixing tank; 38. Granulation tower; 39. Second screening cooler; 40. Nitric acid phosphate fertilizer warehouse; 41. Potassium salt pipeline; 42. Impurity pipeline; 43. Steam pipeline network; 44. Scrubber; 45. Dryer; 46. Industrial gypsum warehouse; 47. Clean water pipeline; 48. Washing water pipeline; 49. Soil conditioner storage tank; 40. Small particle channel. Detailed Implementation
[0018] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present utility model.
[0019] The following is in conjunction with the appendix Figure 1 This application provides a further detailed description of a system for the co-production of potassium nitrate and calcium magnesium nitrate fertilizers in a nitric acid phosphate fertilizer plant. The system includes a phosphate rock powder magnesium calcium pre-removal unit, which is connected to a primary acid decalcification unit. The primary acid decalcification unit is connected to a nitric acid phosphate fertilizer production unit via a secondary decalcification and potassium nitrate separation unit, which is also connected to a potassium nitrate production unit. The liquid phase channel in the phosphate rock powder magnesium calcium pre-removal unit and the solid phase channel in the primary acid decalcification unit are connected to the calcium magnesium nitrate fertilizer production unit. The phosphate rock powder magnesium calcium pre-removal unit includes at least a magnesium removal tank 1. The top of the magnesium removal tank 1 is connected to a phosphate rock powder channel 2 and a first nitric acid pipe 3. The outlet of the magnesium removal tank 1 is connected to a filter press 4. The liquid phase outlet of the filter press 4 is connected to the primary acid decalcification unit, and the solid phase pipe of the filter press 4 is connected to the calcium magnesium nitrate fertilizer production unit. This invention effectively improves the purity of nitrophosphate fertilizer through multiple decalcification processes, and also enhances the flowability of the nitrophosphate fertilizer production material. This facilitates production and prevents clogging of the granulation nozzle, laying the foundation for subsequent granulation tower production of nitrophosphate fertilizer. The invention utilizes a secondary decalcification and potassium nitrate separation unit to separate potassium nitrate from the material, enabling the production of potassium nitrate through a potassium nitrate production unit. Simultaneously, a magnesium-calcium pre-removal unit for phosphate rock powder and a primary acid decalcification unit separate the corresponding liquid and solid phases, laying the foundation for the production of calcium-magnesium nitrate fertilizer through a calcium-magnesium nitrate fertilizer production unit. This invention enables the effective utilization of phosphate rock and increases the added value of the product, thereby enhancing the company's competitiveness. The invention includes a magnesium-calcium pre-removal unit for phosphate rock powder. High magnesium / calcium content in phosphate rock can affect the flowability of subsequent materials and increase filtration difficulty. This pre-removal of magnesium / calcium ensures continuous operation of subsequent processes.
[0020] Furthermore, the primary acid decalcification unit includes an acid decomposition tank 5 connected to the liquid phase outlet of the filter press 4. The acid decomposition tank 5 is also connected to the second nitric acid pipeline 6. The bottom of the acid decomposition tank 5 is connected to the inlet of the horizontal screw press 7. The liquid phase outlet of the horizontal screw press 7 is connected to the freeze crystallizer 8. The outlet of the freeze crystallizer 8 is connected to the first centrifuge 9. The solid phase outlet of the first centrifuge 9 is connected to the secondary decalcification and potassium nitrate separation unit. The liquid phase pipeline of the first centrifuge 9 is connected to the calcium magnesium nitrate fertilizer production unit. This invention utilizes a horizontal screw press 7, which continuously separates suspended solids from liquids through mechanical separation. The drum and screw rotate at a certain differential speed in the same direction at high speed. Material is continuously introduced into the inner cylinder of the conveying screw through the feed pipe, accelerating before entering the drum. Under the influence of the centripetal force field, heavier solids accumulate on the inner wall of the drum, forming a residue layer. The conveying screw continuously pushes the accumulated solids to the conical end of the drum, where they are discharged through the slag outlet. The lighter liquid phase forms an inner liquid ring, continuously overflowing from the large end of the drum and being discharged through the liquid outlet. The liquid phase separated by the horizontal screw press 7 contains calcium nitrate tetrahydrate. The solubility of calcium nitrate tetrahydrate is greatly affected by temperature; therefore, this invention employs a cryogenic crystallizer 8 to remove it, thereby regulating the yield of subsequent calcium magnesium nitrate fertilizer and potassium nitrate.
[0021] Furthermore, the calcium magnesium nitrate fertilizer production unit includes a dissolving tank 10, which is equipped with a magnesium oxide pipe 11 and a third nitric acid pipe 12. The calcium magnesium nitrate outlet of the dissolving tank 10 is connected to a neutralization tank 13, which is equipped with a first ammonia gas pipe 14. The calcium magnesium nitrate outlet of the neutralization tank 13 is connected to a triple-effect steam purifier 15, and the outlet of the triple-effect steam purifier 15 is connected to a calcium magnesium nitrate fertilizer storage tank 18 via a fluidized bed granulator 16 and a first screening and cooling machine 17. Based on the mixture of the aforementioned tetrahydrate calcium nitrate and the dilute calcium magnesium nitrate solution from the liquid phase outlet of the filter press 4, dilute nitric acid is added, and ammonia gas is introduced into the neutralization tank 13 for reaction. During this process, a calcium magnesium nitrate fertilizer solution is generated. This solution is evaporated and concentrated by the triple-effect steam purifier 15 and then granulated by the fluidized bed granulator 16 to obtain calcium magnesium nitrate fertilizer.
[0022] Furthermore, the small particle channel 49 in the first screening and cooling machine 17 is connected to the seed inlet of the fluidized bed granulator 16. This configuration enables the reuse of waste materials, thereby reducing the production cost of calcium magnesium nitrate fertilizer.
[0023] Furthermore, the secondary decalcification and potassium nitrate separation unit includes a potassium nitrate reaction tank 19 connected to the liquid phase outlet of the first centrifuge 9. The potassium nitrate reaction tank 19 is equipped with a potassium sulfate pipe 20. The potassium nitrate reaction tank 19 is connected to a filter 21. The liquid phase outlet of the filter 21 is connected to a first cooling crystallizer 22. The outlet of the first cooling crystallizer 22 is connected to a second centrifuge 23. The solid phase outlet of the second centrifuge 23 is connected to a redissolution tank 24. The redissolution tank 24 is equipped with a potassium carbonate pipe 25. The redissolution tank 24 is connected to a second cooling crystallizer 27 through a filter 26. The outlet of the second cooling crystallizer 27 is connected to a third centrifuge 28. The solid phase outlet of the third centrifuge 28 is connected to a potassium nitrate storage tank 30 through a dryer 29.
[0024] Furthermore, the liquid phase outlet of the third centrifuge 28 is connected to the filtrate reuse inlet of the redissolution tank 24.
[0025] Furthermore, the liquid phase outlet of the second centrifuge 23 is connected to the first inlet of the tubular reactor 31, the second inlet of the tubular reactor 31 is connected to the fourth nitric acid pipeline 32, the third inlet of the tubular reactor 31 is connected to the second ammonia gas pipeline 33, the outlet of the tubular reactor 31 is connected to the flash tank 34, the liquid phase outlet of the flash tank 34 is connected to the first heat exchange channel of the two-stage evaporator 35, the outlet of the first heat exchange channel of the two-stage evaporator 35 is connected to the mixing tank 36, the outlet of the mixing tank 36 is connected to the granulation tower 37, and the outlet of the granulation tower 37 is connected to the nitric acid phosphate fertilizer warehouse 39 through the second screening cooler 38; the mixing tank 36 is equipped with a potassium salt pipeline 40 and an impurity pipeline 41 connected to the impurity outlet of the filter 26. By setting up a fourth nitric acid pipe 32, dilute nitric acid can be added into the tubular reactor 31 to adjust the N / P ratio in the nitric acid phosphate fertilizer while ensuring the fluidity of the solution. This invention ensures the fluidity of the solution through multiple decalcification processes, which not only makes it easy to operate but also enables continuous production. In addition, the solution in this invention has good fluidity and less solid insoluble matter, so granulation tower 37 can be used for granulation. This not only avoids clogging of the granulator but also effectively ensures the appearance and strength of the fertilizer, thereby improving product quality.
[0026] Furthermore, the process steam pipe of the flash evaporator 34 is connected to the second heat exchange channel of the two-stage evaporator 35, and the steam network 42 is connected to the condensate inlet of the redissolution tank 24 through the third heat exchange channel of the two-stage evaporator 35. This arrangement enables effective recovery and utilization of heat energy, thereby saving steam in the steam network 42; the condensate from the second heat exchange channel of the two-stage evaporator 35 can be used as a raw material for acid preparation in subsequent processes.
[0027] Furthermore, the solid phase outlet of the filter 21 is connected to the scrubber 43, and the outlet of the scrubber 43 is connected to the industrial gypsum warehouse 45 via the dryer 44; a clean water pipe 46 is provided at the top of the scrubber 43, and a washing water pipe 47 at the bottom of the scrubber 43 is connected to the liquid phase inlet of the first cooling crystallizer 22; the insoluble matter outlet of the horizontal screw press 7 is connected to the soil conditioner storage tank 48. In the process of producing nitric acid phosphate fertilizer using phosphate rock powder in this utility model, not only potassium nitrate and calcium magnesium nitrate fertilizers can be produced as byproducts, but also industrial gypsum and soil conditioner can be produced as byproducts, thereby improving the utilization rate of phosphate rock powder and enhancing the competitiveness of enterprises.
[0028] A production method for a nitrate phosphate fertilizer plant that co-produces potassium nitrate and calcium magnesium nitrate fertilizers, the production method comprising the following steps:
[0029] Step 1: Phosphate rock powder in phosphate rock powder channel 2 enters magnesium stripping tank 1, and dilute nitric acid in first nitric acid pipe 3 enters magnesium stripping tank 1; the two are mixed and reacted in magnesium stripping tank 1, and the reaction products include liquid magnesium nitrate and calcium nitrate; and solid slurry-like phosphate rock powder; the phosphate rock powder contains 26-28% phosphorus pentoxide, and the concentration of dilute nitric acid in first nitric acid pipe 3 is 10-20%;
[0030] Step 2: The reaction products are filtered through a filter press 4 to separate the liquid and solid phases. The separated solid phase enters the acidolysis tank 5, and the dilute nitric acid in the second nitric acid pipeline 6 enters the acidolysis tank 5 for acidolysis reaction. The acidolysis reaction products include liquid calcium nitrate, dilute phosphoric acid, nitric acid, and solid acid-insoluble matter. The above acidolysis reaction products are separated by a horizontal screw press 7. The separated solid phase, which is solid acid-insoluble matter, enters the soil conditioner storage tank 48 for use as a soil conditioner. The concentration of dilute nitric acid in the second nitric acid pipeline 6 is 55%.
[0031] Step 3: The liquid phase separated by the decanter 7 enters the first cryogenic crystallizer 8. At an operating temperature of -5℃, calcium nitrate tetrahydrate crystallizes into a solid. The material in the first cryogenic crystallizer 8 enters the first centrifuge 9 for solid-liquid separation. The solid phase after solid-liquid separation and the liquid phase separated by the filter press 4 in step 2 enter the dissolving tank 10 together. Magnesium oxide from magnesium oxide pipe 11 enters the dissolving tank 10, and 55% dilute nitric acid from the third nitric acid pipe 12 enters the dissolving tank 10. Calcium nitrate tetrahydrate in the dissolving tank 10... Calcium magnesium nitrate solution, magnesium oxide, and 55% dilute nitric acid from filter press 4 are mixed and reacted in dissolving tank 10. The reacted material enters neutralization tank 13 and reacts with gaseous ammonia from first ammonia pipeline 14 to generate calcium magnesium nitrate fertilizer solution with N content of 13.5-15.5%. The calcium magnesium nitrate fertilizer solution is concentrated in three stages by triple-effect steam generator 15, and then granulated by fluidized bed granulator 16. The calcium magnesium nitrate fertilizer granules are screened and cooled by first screening and cooling machine 17 and then sent to calcium magnesium nitrate fertilizer storage tank 18.
[0032] Step 4: The liquid phase after solid-liquid separation in the first centrifuge 9 in Step 3 enters the potassium nitrate reaction tank 19, and the potassium sulfate in the potassium sulfate pipeline 20 enters the potassium nitrate reaction tank 19. The two materials react in the potassium nitrate reaction tank 19, and the reaction products include a solid phase and a liquid phase. The solid phase is calcium sulfate dihydrate, and the liquid phase is a mixed solution of potassium nitrate, phosphoric acid, and nitric acid. The reaction time is 1-2 hours. The reaction products enter the filter 21 for solid-liquid separation.
[0033] Step 5: The liquid phase after solid-liquid separation in filter 21 in step 4 enters the first cooling crystallizer 22 to crystallize potassium nitrate at an operating temperature of 0℃; the material in the first cooling crystallizer 22 enters the second centrifuge 23 for solid-liquid separation.
[0034] Step 6: The solid phase after solid-liquid separation in step 5 via the second centrifuge 23 enters the redissolution tank 24, and the potassium carbonate in the potassium carbonate pipeline 25 enters the redissolution tank 24. The condensate from the third heat exchange channel of the two-stage evaporator 35, the liquid phase from the third centrifuge 28, and the crude potassium nitrate and potassium carbonate react in the redissolution tank 24 in a reverse reaction to generate calcium carbonate and magnesium carbonate precipitates. After impurities are removed by the filter 26, and calcium and magnesium ions are removed by cooling and crystallization by the second cooling crystallizer 27, the precipitate enters the third centrifuge 28 for solid-liquid separation. The liquid phase after solid-liquid separation is returned to the redissolution tank 24 for reuse. The solid phase after solid-liquid separation enters the dryer 29 to obtain dry potassium nitrate, and finally it is stored in the potassium nitrate storage tank 30.
[0035] Step 7: The liquid phase after solid-liquid separation by the second centrifuge 23 in Step 5 enters the tubular reactor 31. At the same time, gaseous ammonia in the second gaseous ammonia pipeline 33 enters the tubular reactor 31 through the third inlet of the tubular reactor 31, and 55% dilute nitric acid in the fourth nitric acid pipeline 32 enters the tubular reactor 31. The above liquid phase, gaseous ammonia, and 55% dilute nitric acid are fully mixed and neutralized in the tubular reactor 31. The neutralized material enters the flash tank 34 for flash evaporation. The flash evaporation process separates the process steam and the nitric acid phosphate fertilizer solution. The nitric acid phosphate fertilizer solution enters the first heat exchange channel of the two-stage evaporator 35. First, the above process steam enters the second heat exchange channel of the two-stage evaporator 35 for heat exchange. After heat exchange, it is concentrated by heat exchange with the steam from the steam network 42 that enters the second heat exchange channel of the two-stage evaporator 35.
[0036] Step 8: The concentration of the nitric acid phosphate fertilizer solution after passing through the two-stage evaporator 35 is 99.5%. The 99.5% concentration nitric acid phosphate fertilizer solution enters the mixing tank 36. The nitric acid phosphate fertilizer solution in the mixing tank 36 is granulated by the granulation tower 37. After granulation, it is screened and cooled by the second screening and cooling machine 38 and then sent to the nitric acid phosphate fertilizer warehouse 39. The above-mentioned nitric acid phosphate fertilizer is a binary nitric acid phosphate fertilizer.
[0037] Step 9: The solid phase after solid-liquid separation in filter 21 in step 4 is calcium sulfate dihydrate. After being washed by scrubber 43 and dried by dryer 44, the calcium sulfate dihydrate becomes industrial gypsum. The industrial gypsum is stored in industrial gypsum warehouse 45. The clean water in clean water pipe 46 enters scrubber 43 as washing water. The washing water after washing enters the first cooling crystallizer 22 through washing water pipe 47 for recycling.
[0038] Step 10: The potassium salt in the potassium salt pipeline 40 enters the mixing tank 36 and is mixed with a 99.5% nitrate phosphate fertilizer solution. After mixing, the mixture enters the granulation tower 37 for granulation. After granulation, the mixture is screened and cooled by the second screening and cooling machine 38 and then sent to the nitrate phosphate fertilizer warehouse 39. The above-mentioned nitrate phosphate fertilizer is a ternary nitrate phosphate fertilizer.
[0039] Step 11: Impurities in filter 26 enter mixing tank 36 through impurity pipe 41, so that impurities in filter 26 can be used as filler for binary nitrate phosphate fertilizer or ternary nitrate phosphate fertilizer.
[0040] This invention can process various components in phosphate rock into phosphate / potassium nitrate fertilizer, calcium magnesium nitrate fertilizer, potassium nitrate, industrial gypsum, and soil conditioner, which not only makes full use of resources but also increases the added value of products. Its reaction process mainly utilizes the following principles:
[0041] (1) Demagnesification of phosphate rock powder:
[0042] 2HNO3+MgCO3→Mg(NO3)2+H2O+CO2
[0043] 2HNO3+CaCO3→Ca(NO3)2+H2O+CO2
[0044] (2) Neutralization process of acid hydrolysate
[0045] The main component of phosphate rock, calcium fluorophosphate, reacts with nitric acid:
[0046] Ca5F(PO4)3+10HNO3=5Ca(NO3)2+3H3PO4+HF↑
[0047] (3) Secondary decalcification and potassium nitrate formation reaction:
[0048] Ca(NO3)2+K2SO4+2H2O=2KNO3+CaSO4·2H2O↓
[0049] Ca(NO3)2+K2CO3=2KNO3+CaCO3↓
[0050] (4) Nitrophosphate fertilizer formation reaction:
[0051] H3PO4+HNO3+2NH3=NH4NO3+NH4H2PO4
[0052] Compared to traditional technologies that require high-grade phosphate rock powder (phosphate rock powder containing 30% or more of phosphorus pentoxide), this invention utilizes medium-grade phosphate rock powder. Through a magnesium-calcium pre-removal unit, 10-20% dilute nitric acid and phosphate rock powder containing 26-28% phosphorus pentoxide are mixed in a magnesium removal tank 1. This allows the magnesium and a very small amount of calcium in the phosphate rock powder to preferentially react with the nitric acid, producing liquid magnesium nitrate and calcium nitrate, and solid slurry-like phosphate rock powder. The solid and liquid phases are separated by a filter press 4. The liquid is a dilute solution of calcium magnesium nitrate, and the solid filter residue is phosphate concentrate containing more than 32% phosphorus pentoxide. This process not only refines the medium-grade phosphate rock powder, ensuring subsequent production, but also lays the foundation for the production of calcium magnesium nitrate fertilizer.
[0053] The foregoing has shown and described the basic principles, main features, and advantages of this utility model. Those skilled in the art should understand that this utility model is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of this utility model. Various changes and modifications can be made to this utility model without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed utility model.
Claims
1. A system for co-producing potassium nitrate and calcium magnesium nitrate fertilizers using a nitrate phosphate fertilizer plant, characterized in that: The system includes a magnesium-calcium pre-removal unit for phosphate rock powder, which is connected to a primary acid decalcification unit. The primary acid decalcification unit is connected to a nitrate phosphate fertilizer production unit via a secondary decalcification and potassium nitrate separation unit. The secondary decalcification and potassium nitrate separation unit is also connected to a potassium nitrate production unit. The liquid phase channel in the magnesium-calcium pre-removal unit and the solid phase channel in the primary acid decalcification unit are connected to the calcium-magnesium nitrate fertilizer production unit. The magnesium-calcium pre-removal unit for phosphate rock powder includes at least a magnesium removal tank (1). The top of the magnesium removal tank (1) is connected to the phosphate rock powder channel (2) and the first nitric acid pipeline (3). The outlet of the magnesium removal tank (1) is connected to the filter press (4). The liquid phase outlet of the filter press (4) is connected to the primary acid decalcification unit. The solid phase pipeline of the filter press (4) is connected to the calcium magnesium nitrate fertilizer production unit.
2. The system for co-producing potassium nitrate and calcium magnesium nitrate fertilizers in a nitrate phosphate fertilizer plant according to claim 1, characterized in that: The primary acid decalcification unit includes an acid decomposition tank (5) connected to the liquid phase outlet of the filter press (4). The acid decomposition tank (5) is also connected to the second nitric acid pipeline (6). The bottom of the acid decomposition tank (5) is connected to the inlet of the horizontal screw press (7). The liquid phase outlet of the horizontal screw press (7) is connected to the freeze crystallizer (8). The outlet of the freeze crystallizer (8) is connected to the first centrifuge (9). The solid phase outlet of the first centrifuge (9) is connected to the secondary decalcification and potassium nitrate separation unit. The liquid phase pipeline of the first centrifuge (9) is connected to the calcium magnesium nitrate fertilizer production unit.
3. A system for co-producing potassium nitrate and calcium magnesium nitrate fertilizers in a nitrate phosphate fertilizer plant according to claim 1 or 2, characterized in that: The calcium magnesium nitrate fertilizer production unit includes a dissolving tank (10), on which a magnesium oxide pipe (11) and a third nitric acid pipe (12) are provided. The calcium magnesium nitrate outlet of the dissolving tank (10) is connected to a neutralization tank (13). The neutralization tank (13) is provided with a first ammonia gas pipe (14). The calcium magnesium nitrate outlet of the neutralization tank (13) is connected to a triple-effect steam generator (15). The outlet of the triple-effect steam generator (15) is connected to a calcium magnesium nitrate fertilizer storage tank (18) through a fluidized bed granulator (16) and a first screening cooler (17).
4. The system for co-producing potassium nitrate and calcium magnesium nitrate fertilizers in a nitrate phosphate fertilizer plant according to claim 3, characterized in that: The small particle channel (49) in the first screening cooler (17) is connected to the seed inlet of the fluidized bed granulator (16).
5. The system for co-producing potassium nitrate and calcium magnesium nitrate fertilizers in a nitrate phosphate fertilizer plant according to claim 2, characterized in that: The secondary decalcification and potassium nitrate separation unit includes a potassium nitrate reaction tank (19) connected to the liquid phase outlet of the first centrifuge (9). A potassium sulfate pipe (20) is provided on the potassium nitrate reaction tank (19). The potassium nitrate reaction tank (19) is connected to a filter (21). The liquid phase outlet of the filter (21) is connected to a first cooling crystallizer (22). The outlet of the first cooling crystallizer (22) is connected to a second centrifuge (23). The solid phase outlet of the second centrifuge (23) is connected to a redissolution tank (24). A potassium carbonate pipe (25) is provided on the redissolution tank (24). The redissolution tank (24) is connected to a second cooling crystallizer (27) via a filter (26). The outlet of the second cooling crystallizer (27) is connected to a third centrifuge. (28) Connected, the solid phase outlet of the third centrifuge (28) is connected to the potassium nitrate storage tank via the dryer (29). (30) Connected.
6. The system for co-producing potassium nitrate and calcium magnesium nitrate fertilizers in a nitrate phosphate fertilizer plant according to claim 5, characterized in that: The liquid phase outlet of the third centrifuge (28) is connected to the filtrate reuse inlet of the redissolution tank (24).
7. The system for co-producing potassium nitrate and calcium magnesium nitrate fertilizers in a nitrate phosphate fertilizer plant according to claim 5, characterized in that: The liquid phase outlet of the second centrifuge (23) is connected to the first inlet of the tubular reactor (31), the second inlet of the tubular reactor (31) is connected to the fourth nitric acid pipeline (32), the third inlet of the tubular reactor (31) is connected to the second ammonia gas pipeline (33), the outlet of the tubular reactor (31) is connected to the flash tank (34), the liquid phase outlet of the flash tank (34) is connected to the first heat exchange channel of the two-stage evaporator (35), the outlet of the first heat exchange channel of the two-stage evaporator (35) is connected to the mixing tank (36), the outlet of the mixing tank (36) is connected to the granulation tower (37), and the outlet of the granulation tower (37) is connected to the nitric acid phosphate fertilizer warehouse (39) through the second screening cooler (38). The mixing tank (36) is provided with a potassium salt pipe (40) and an impurity pipe (41) connected to the impurity outlet of the filter (26).
8. The system for co-producing potassium nitrate and calcium magnesium nitrate fertilizers in a nitrate phosphate fertilizer plant according to claim 7, characterized in that: The process steam pipe of the flash tank (34) is connected to the second heat exchange channel of the two-stage evaporator (35), and the steam network (42) is connected to the condensate inlet of the redissolution tank (24) through the third heat exchange channel of the two-stage evaporator (35).
9. A system for co-producing potassium nitrate and calcium magnesium nitrate fertilizers in a nitrate phosphate fertilizer plant according to claim 5, characterized in that: The solid phase outlet of the filter (21) is connected to the scrubber (43), and the outlet of the scrubber (43) is connected to the industrial gypsum warehouse (45) through the dryer (44); the top of the scrubber (43) is provided with a clean water pipe (46), and the washing water pipe (47) at the bottom of the scrubber (43) is connected to the liquid phase inlet of the first cooling crystallizer (22). The insoluble material outlet of the horizontal screw press (7) is connected to the soil conditioner storage tank (48).