Ammonium nitrate refining system and method in nitrophosphate fertilizer production

Abstract

The invention discloses an ammonium nitrate refining system and method in nitrophosphate fertilizer production, the ammonium nitrate refining system comprises a refining filter, a pH control tank, a buffer tank and a heating concentration mechanism which are connected in sequence, the lower part of the refining filter is provided with an ammonium nitrate solution inlet, the upper part is provided with a filtering outlet, and the bottom is provided with a calcium carbonate outlet; a dilute ammonium nitrate inlet and a washing liquid / nitric acid inlet are formed in the top of the pH control tank; an outlet of the pH control tank is connected with an inlet of the buffer tank; the heating concentration mechanism comprises an evaporation chamber and a heater, the evaporation chamber is sequentially provided with a tail gas outlet, a dilute solution inlet, a circulating solution inlet, a concentrated solution outlet and the circulating solution outlet from top to bottom, the dilute solution inlet is connected with the outlet of the buffer tank, and the concentrated solution outlet is used for discharging an evaporated and concentrated concentrated ammonium nitrate solution; the circulating solution outlet and the circulating solution inlet are respectively connected with a refrigerant inlet and a refrigerant outlet of the heater, and a heating medium inlet and a heating medium outlet of the heater are respectively connected with a steam pipeline and a condensate pipeline.

Description

Technical Field

[0001] This invention relates to an ammonium nitrate refining system and method in the production of nitric acid phosphate fertilizer, belonging to the field of chemical production technology. Background Technology

[0002] Fertilizer can be produced by decomposing phosphate rock with nitric acid. Nitric acid decomposition of phosphate rock requires a reaction time of 20-60 minutes, significantly shorter than the 120-360 minutes required by sulfuric acid decomposition. During this process, nitric acid acts as an acidolytic agent, converting the P2O5 in the ore into a form absorbable by crops. Furthermore, nitric acid itself remains in the product as nitrogen fertilizer, achieving a "nitrogen-carrying-phosphorus" effect. Nitric acid decomposition of phosphate rock does not produce phosphogypsum. Compared to the sulfuric acid method, producing 1 ton of P2O5 results in approximately 5 tons less phosphogypsum emissions, eliminating the problem of phosphogypsum stockpiling, protecting the environment, and introducing approximately 0.66-1 ton of nitrate nitrogen. The mixed acid solution obtained from nitric acid decomposition of phosphate rock can be used to prepare nitrate phosphate fertilizer (containing both ammonium nitrate and ammonium phosphate). Nitrate phosphate fertilizer contains readily available nitrate nitrogen (NO3). - It contains water-soluble P2O5, as well as ammonium nitrogen (NH4) which has a longer-lasting fertilizer effect. + Nitrogen phosphate fertilizer is suitable for dryland crops, especially crops such as tobacco and citrus that require nitrate nitrogen supply, to improve the quality of cash crops. It also has significant fertilizer effects on grain crops such as wheat, corn and rice, and cash crops such as rapeseed, tea, cotton and soybeans, especially in medium and low fertility soils.

[0003] However, directly producing fertilizer from phosphate rock by simply using nitric acid to decompose it is unsuitable because such fertilizer is highly corrosive and hygroscopic. Therefore, it must be neutralized or ammonified. Because in phosphate rock, Ca... 2+ The molar ratio of P2O5 to Ca2O5 is generally above 3.33:1. During neutralization and ammoniation, the resulting precipitate of calcium phosphate (CaHPO4) contains Ca... 2+ The molar ratio of P2O5 is only 2:1, meaning there is at least 1.33 Ca remaining. 2+ It exists in the form of highly hygroscopic calcium nitrate, which can severely damage the physical properties of fertilizer products. Therefore, measures must be taken to remove excess calcium from the mixed acid solution. 2+ Remove. In the calcium nitrate crystallization separation system, Ca... 2+ It is removed in the form of Ca(NO3)2 solution, therefore, for every Ca molecule removed... 2+ It will contain 2 NO3. - Due to NO3 - It is nitrate nitrogen in nitrate phosphate fertilizer, which is a fast-acting and effective nutrient in chemical fertilizers and must be recycled.

[0004] To avoid producing the byproduct phosphogypsum, sulfate ions are not added to the calcium nitrate to ammonium nitrate separation system. NO3- It is recovered using ammonium nitrate solution, Ca 2+ Since calcium carbonate is used for removal, the ammonium nitrate solution from this system will contain calcium carbonate particles. This ammonium nitrate solution typically contains about 40% water and excess ammonia. Such a high water content means the ammonium nitrate solution cannot be directly used to produce concentrated nitric acid phosphate fertilizer solution; most of the water must be removed. Before removing the water, the excess ammonia must be neutralized to minimize losses. Furthermore, because the ammonium nitrate solution containing calcium carbonate particles will cause scaling and blockage of equipment and pipelines, it cannot be reused in the calcium nitrate conversion ammonium nitrate separation system or used for evaporation and concentration, to avoid blocking the production system and rendering it inoperable. Current technology lacks a system and method that can effectively remove calcium carbonate particles, neutralize excess ammonia, and remove water. Summary of the Invention

[0005] The purpose of this invention is to provide an ammonium nitrate refining system for the production of nitric acid phosphate fertilizer, used to remove calcium carbonate particles from ammonium nitrate, neutralize excess ammonia, and remove moisture. This invention also provides a method for refining ammonium nitrate in the production of nitric acid phosphate fertilizer.

[0006] The ammonium nitrate refining system in the production of nitric acid phosphate fertilizer of the present invention adopts the following technical solution: An ammonium nitrate refining system in the production of nitric acid phosphate fertilizer includes a refining filter, a pH control tank, a buffer tank, and a heating and concentration mechanism connected in sequence. The refining filter has an ammonium nitrate solution inlet at the bottom, a filter outlet at the top, and a calcium carbonate outlet at the bottom. The pH control tank is equipped with a stirrer. The top of the pH control tank has a dilute ammonium nitrate inlet and a washing liquid / nitric acid inlet. The dilute ammonium nitrate inlet is connected to the filter outlet. The washing liquid / nitric acid inlet is connected to the washing liquid and nitric acid pipelines from the boundary area. The outlet of the pH control tank is connected to the inlet of the buffer tank. The heating and concentration mechanism includes an evaporation chamber and a heater. The evaporation chamber has a tail gas outlet, a dilute solution inlet, a circulating solution inlet, a concentrated solution outlet, and a circulating solution outlet in sequence from top to bottom. The tail gas outlet is used to discharge steam. The dilute solution inlet is connected to the outlet of the buffer tank through a pipeline. The concentrated solution outlet is used to discharge the concentrated ammonium nitrate solution after evaporation and concentration. The circulating solution outlet and the circulating solution inlet are respectively connected to the refrigerant inlet and the refrigerant outlet of the heater. The heat medium inlet and the heat medium outlet of the heater are respectively connected to the steam pipeline and the condensate pipeline.

[0007] A branch pipe is connected to the pipe between the buffer tank and the dilute solution inlet of the evaporation chamber. The branch pipe is used to discharge part of the refined ammonium nitrate solution.

[0008] The heating and concentration mechanism consists of two or more sets. Each set includes an evaporation chamber and a heater connected together. Along the flow direction of ammonium nitrate, the dilute solution inlet of the first evaporation chamber is connected to the outlet of the buffer tank. The tail gas outlet of the first evaporation chamber discharges steam to the outside. The concentrated solution outlet of the last evaporation chamber discharges concentrated ammonium nitrate solution to the outside. In two adjacent sets of heating and concentration mechanisms, the concentrated solution outlet of the previous evaporation chamber is connected to the dilute solution inlet of the next evaporation chamber. The heat medium inlet of the previous heater is connected to the tail gas outlet of the next evaporation chamber. The heat medium outlet of each heater discharges condensate to the outside.

[0009] In two adjacent heating and concentration units, a feed pump is installed on the pipeline between the concentrated solution outlet of the first evaporation chamber and the dilute solution inlet of the next evaporation chamber.

[0010] The concentrated solution outlet of the last evaporation chamber is connected to a concentrated ammonium nitrate storage tank via a pipeline. The concentrated ammonium nitrate storage tank is equipped with a stirrer. The bottom of the concentrated ammonium nitrate storage tank is connected to a concentrated ammonium nitrate discharge pipeline, which is equipped with a concentrated ammonium nitrate pump.

[0011] The evaporation chamber and heater are both vertical structures; a circulation pump is installed on the pipeline between the circulating solution outlet and the refrigerant inlet; and a dilute ammonium nitrate pump is installed on the pipeline between the buffer tank and the dilute solution inlet of the heating and concentration mechanism.

[0012] The pH control tank is positioned higher than the buffer tank, with the outlet of the pH control tank angled downwards and the inlet of the buffer tank angled upwards, and the inlet of the buffer tank and the outlet of the pH control tank are on the same straight line.

[0013] The ammonium nitrate refining method in the production of nitric acid phosphate fertilizer of the present invention adopts the following technical solution: A method for refining ammonium nitrate in the production of nitric acid phosphate fertilizer, which is carried out using the above-mentioned ammonium nitrate refining system in the production of nitric acid phosphate fertilizer, includes the following steps: (1) Ammonium nitrate refining section: The raw material ammonium nitrate solution from the calcium nitrate conversion ammonium nitrate separation system enters the refining filter from the ammonium nitrate solution inlet, and the calcium carbonate particles are filtered out in the refining filter. The filtered calcium carbonate particles are discharged from the bottom calcium carbonate outlet, and the ammonium nitrate solution with the calcium carbonate particles removed exits from the side filter outlet and enters the pH control tank from the top inlet of the pH control tank; Nitric acid and washing liquid from the boundary area enter the pH control tank from the top washing liquid / nitric acid inlet, and are stirred in the pH control tank with a control tank stirrer, so that the nitric acid and ammonium nitrate solution are fully mixed. The pH value of the refined ammonium nitrate solution is controlled at 6-7. The refined ammonium nitrate solution is overflowed from the outlet on the side of the pH control tank and enters the buffer tank from the inlet on the side of the buffer tank. The refined ammonium nitrate solution in the buffer tank exits from the outlet on the side of the buffer tank. Part of it is pumped to the branch pipe by the dilute ammonium nitrate pump and enters the calcium nitrate to ammonium nitrate separation system for recycling. The other part of the refined ammonium nitrate solution enters the heating and concentration mechanism from the dilute ammonium nitrate inlet. (2) Heating evaporation and concentration section: The refined ammonium nitrate solution enters the evaporation chamber from the dilute ammonium nitrate inlet for evaporation and concentration. Part of the refined ammonium nitrate solution after evaporation and concentration is discharged from the concentrated ammonium nitrate outlet. The other part of the refined ammonium nitrate solution after evaporation and concentration enters the heater. After exchanging heat with steam in the heater, it enters the evaporation chamber again from the circulating solution inlet. The tail gas generated in the evaporation chamber is discharged from the exhaust gas outlet at the top.

[0014] The ammonium nitrate heating, evaporation, and concentration section includes a second-effect heating, evaporation, and concentration section and a first-effect heating, evaporation, and concentration section. Ammonium nitrate II-effect heating, evaporation, and concentration section: Secondary steam from the top steam outlet of the I-effect evaporator enters the shell side of the II-effect heater through the heat transfer medium inlet, exchanging heat with the circulating ammonium nitrate solution in the tube side. The secondary steam is cooled into condensate and discharged from the heat transfer medium outlet to the boundary area for reuse. Refined ammonium nitrate solution from the dilute ammonium nitrate pump enters the II-effect evaporator through the dilute ammonium nitrate solution inlet. A portion of the II-effect ammonium nitrate solution in the II-effect evaporator exits from the side concentrated ammonium nitrate outlet to the feed pump. Another portion of the II-effect ammonium nitrate solution exits from the bottom circulating solution outlet of the II-effect evaporator, passes through the II-effect circulating pump, and enters the II-effect heater through the refrigerant inlet. In the II-effect heater, the II-effect ammonium nitrate solution is heated and exits from the refrigerant outlet, then passes through the side circulating solution inlet to the II-effect evaporator for evaporation and concentration. The exhaust gas evaporated from the waste gas outlet at the top of the II-effect evaporator is discharged to the boundary area. Ammonium nitrate I-effect heating, evaporation, and concentration section: Live steam from the boundary area enters the shell side of the I-effect heater through the heat medium inlet, exchanging heat with the I-effect circulating ammonium nitrate solution in the tube side. The live steam is cooled into condensate and returned to the boundary area for reuse through the heat medium outlet. Ammonium nitrate solution from the II-effect heater enters the I-effect evaporation chamber through the side dilute solution inlet from the feed pump. A portion of the I-effect ammonium nitrate solution in the I-effect evaporation chamber exits the I-effect evaporation chamber through the side concentrated ammonium nitrate outlet and enters the concentrated ammonium nitrate storage tank. The I-effect ammonium nitrate solution in the concentrated ammonium nitrate storage tank, as the target product, is pumped from the side outlet of the concentrated ammonium nitrate storage tank to the nitric acid phosphate fertilizer concentrate production system via the concentrated ammonium nitrate pump. Another portion of the I-effect ammonium nitrate solution in the I-effect evaporation chamber exits the I-effect evaporation chamber through the bottom circulating solution outlet and enters the I-effect heater through the refrigerant inlet via the I-effect circulating pump. In the I-effect heater, the I-effect ammonium nitrate solution is heated and exits the I-effect heater through the refrigerant outlet and enters the I-effect evaporation chamber through the side circulating solution inlet for evaporation and concentration.

[0015] The raw material ammonium nitrate solution contains 60.12% NH4NO3 by mass; the nitric acid from the boundary area contains 58% NH4NO3 by mass, and the washing liquid contains 59.864% NH4NO3 by mass; the refined ammonium nitrate solution after purification contains 59.804% NH4NO3 by mass; in the pH control tank, the pH value of the refined ammonium nitrate solution is controlled at 6.5.

[0016] The beneficial effects of this invention are as follows: The ammonium nitrate solution, the raw material from the calcium nitrate to ammonium nitrate separation system, is purified by removing calcium carbonate particles in a refining filter. It is then fed into a pH control tank to maintain the pH value of the purified ammonium nitrate solution at approximately 6.5. Part of the purified ammonium nitrate solution is recycled back to the calcium nitrate to ammonium nitrate separation system, while the other part is evaporated and concentrated. The resulting concentrated ammonium nitrate solution is then used in a nitric acid phosphate fertilizer concentrate production system to produce nitric acid phosphate fertilizer concentrate. Through this invention, a portion of the ammonium nitrate solution is recycled, and the other portion is used to produce nitric acid phosphate fertilizer. Both portions of the purified ammonium nitrate solution are utilized efficiently. The entire nitric acid phosphate fertilizer production process does not produce phosphogypsum, eliminating the problem of phosphogypsum stockpiling and protecting the environment.

[0017] The present invention has the following advantages: (1) The present invention effectively removes calcium carbonate particles from the raw material ammonium nitrate solution from the calcium nitrate to ammonium nitrate separation system. In the 100 tons / hour nitrate phosphate fertilizer plant, the ammonium nitrate refining and evaporation system of the present invention processes about 132 tons of ammonium nitrate solution per hour and removes more than 144 kg of calcium carbonate particles with the refining filter, thus avoiding calcium carbonate scaling, clogging of equipment and pipelines. (2) The present invention neutralizes the excess ammonia in the ammonium nitrate solution from the refining filter. The pH value of the ammonium nitrate solution is adjusted to about 6.5 in the pH control tank with nitric acid to ensure that the excess free ammonia reacts with nitric acid to form ammonium nitrate. In a 100-ton / hour nitric acid phosphate fertilizer plant, the ammonium nitrate refining and evaporation system of the present invention reduces ammonia loss by about 344 kg per hour. (3) The present invention performs two-stage evaporation and concentration on the refined ammonium nitrate solution from the refined ammonium nitrate pump. In the 100 tons / hour nitrate phosphate fertilizer plant, the ammonium nitrate refining and evaporation system of the present invention processes about 81 tons of refined ammonium nitrate solution per hour. More than 28 tons of water are evaporated and removed. The water content of the concentrated ammonium nitrate solution is reduced from 40% to 8%. The nitrogen content in this solution accounts for more than 63% of the total nitrogen content of the nitrate phosphate fertilizer. (4) The present invention reuses the washing liquid from the exhaust gas scrubbing system. In the 100-ton / hour nitrate phosphate fertilizer plant, the ammonium nitrate refining and evaporation system of the present invention reuses 730 kg of washing liquid per hour. The washing liquid contains 437 kg of ammonium nitrate, thus recovering nitrogen fertilizer, reducing pollution, and protecting the environment. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of an ammonium nitrate refining system in the production of nitrate phosphate fertilizer according to an embodiment of the present invention.

[0019] In the diagram: 1-Refining filter, 2-pH control tank, 3-Control tank stirrer, 4-Buffer tank, 5-Dilute ammonium nitrate pump, 6-II-effect evaporation chamber, 7-II-effect circulating pump, 8-II-effect heater, 9-I-effect feed pump, 10-I-effect evaporation chamber, 11-I-effect circulating pump, 12-I-effect heater, 13-Concentrated ammonium nitrate storage tank, 14-Concentrated ammonium nitrate stirrer, 15-Concentrated ammonium nitrate pump, A1-Tail gas outlet, A2-Dilute solution inlet, A3-Circulating solution inlet, A4-Concentrated solution outlet, A5-Circulating solution outlet, B1-Refrigerant inlet, B2-Refrigerant outlet, B3-Heating medium inlet, B4-Heating medium outlet. Detailed Implementation

[0020] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0021] like Figure 1As shown, an embodiment of the ammonium nitrate refining system in the production of nitric acid phosphate fertilizer according to the present invention includes a refining filter 1, a pH control tank 2, a buffer tank 4, and a heating and concentration mechanism connected in sequence. The refining filter 1 has an ammonium nitrate solution inlet at the bottom, a filter outlet at the top, and a calcium carbonate outlet at the bottom. The pH control tank 2 is equipped with a control tank stirrer 3. The top of the pH control tank 3 has a dilute ammonium nitrate inlet and a washing liquid / nitric acid inlet. The dilute ammonium nitrate inlet is connected to the filter outlet, and the washing liquid / nitric acid inlet is connected to the washing liquid and nitric acid pipelines from the boundary area. The outlet of the pH control tank 3 is connected to the inlet of the buffer tank 4.

[0022] The heating and concentration mechanism includes an evaporation chamber and a heater. The evaporation chamber is provided with a tail gas outlet A1, a dilute solution inlet A2, a circulating solution inlet A3, a concentrated solution outlet A4, and a circulating solution outlet A5 from top to bottom. The tail gas outlet A1 is used to discharge steam. The dilute solution inlet A2 is connected to the outlet of the buffer tank 4 through a pipe. The concentrated solution outlet A4 is used to discharge the concentrated ammonium nitrate solution after evaporation and concentration. The circulating solution outlet A5 and the circulating solution inlet A3 are respectively connected to the refrigerant inlet B1 and the refrigerant outlet B2 of the heater. The heat medium inlet B3 and the heat medium outlet B4 of the heater are respectively connected to the steam pipe and the condensate pipe. The heating and concentration mechanism comprises two or more sets, each including an evaporation chamber and a heater connected together. Along the flow direction of ammonium nitrate, the dilute solution inlet of the first evaporation chamber is connected to the outlet of the buffer tank, and the exhaust gas outlet of the first evaporation chamber discharges steam to the outside. The concentrated solution outlet of the last evaporation chamber discharges concentrated ammonium nitrate solution to the outside. In adjacent sets of heating and concentration mechanisms, the concentrated solution outlet of the preceding evaporation chamber is connected to the dilute solution inlet of the following evaporation chamber, and the heat medium inlet of the preceding heater is connected to the exhaust gas outlet of the following evaporation chamber. The heat medium outlets of each heater discharge condensate to the outside. A feed pump 9 is installed on the pipeline between the concentrated solution outlet of the preceding evaporation chamber and the dilute solution inlet of the following evaporation chamber in adjacent sets of heating and concentration mechanisms. Both the evaporation chamber and the heater adopt a vertical structure. A circulation pump is installed on the pipeline between the circulating solution outlet and the refrigerant inlet.

[0023] In this embodiment, two sets of heating and concentration mechanisms are used. Along the flow direction of ammonium nitrate, the first evaporation chamber is a second-effect evaporation chamber 6, the first heater is a second-effect heater 8, and the circulation pump between the second-effect evaporation chamber 6 and the second-effect heater 8 is a second-effect circulation pump 7. The second evaporation chamber is a first-effect evaporation chamber 10, the second heater is a first-effect heater 12, and the circulation pump between the first-effect evaporation chamber 10 and the first-effect heater 12 is a first-effect circulation pump 11. The concentrated solution outlet of the last evaporation chamber (first-effect evaporation chamber 10 in this embodiment) is connected to a concentrated ammonium nitrate storage tank 13 via a pipeline. The concentrated ammonium nitrate storage tank 13 is equipped with a concentrated ammonium nitrate stirrer 14. The bottom of the concentrated ammonium nitrate storage tank 13 is connected to a concentrated ammonium nitrate discharge pipe, and a concentrated ammonium nitrate pump 15 is installed on the concentrated ammonium nitrate discharge pipe.

[0024] A branch pipe is connected to the pipeline between the buffer tank 4 and the dilute solution inlet of the evaporation chamber, and the branch pipe is used to discharge part of the refined ammonium nitrate solution. A dilute ammonium nitrate pump 5 is installed on the pipeline between the buffer tank 4 and the dilute solution inlet of the heating and concentration mechanism. The pH control tank 3 is positioned higher than the buffer tank 4, the outlet of the pH control tank 3 is angled downwards, the inlet of the buffer tank 4 is angled upwards, and the inlet of the buffer tank 4 and the outlet of the pH control tank 3 are on the same straight line.

[0025] The raw material—ammonium nitrate solution—from the calcium nitrate to ammonium nitrate separation system is connected to the side inlet of the refining filter 1 via a pipeline. After filtration in the refining filter 1, the raw ammonium nitrate solution enters the pH control tank 2 through the filter outlet located at the upper side. Nitric acid or washing liquid is introduced into the pH control tank 2 to adjust the pH of the filtered ammonium nitrate solution. After pH adjustment, the ammonium nitrate solution enters the buffer tank 4, and then enters the evaporation chamber of the heating and concentration mechanism via the dilute ammonium nitrate pump 5. The bottom outlet of the refining filter 1 is calcium carbonate, which is connected to the boundary area. The nitric acid pipeline from the boundary area is connected to the washing liquid / nitric acid inlet at the top of the pH control tank 2. This nitric acid pipeline is equipped with a washing liquid pipeline from the tail gas washing system. The branch pipe between the buffer tank 4 and the evaporation chamber is connected to the pipeline to the calcium nitrate to ammonium nitrate separation system.

[0026] The live steam pipe from the boundary area is connected to the heat medium inlet B3 of the first-effect heater 12, and the heat medium outlet B4 of the first-effect heater 12 is connected to the condensate pipe going to the boundary area; the top outlet A1 of the first-effect evaporator 10 is connected to the heat medium inlet B3 of the second-effect heater 8, and the heat medium outlet B4 of the second-effect heater 8 is connected to the condensate pipe going to the boundary area; the exhaust gas outlet A1 at the top of the second-effect evaporator 6 is connected to the exhaust gas pipe going to the boundary area; the circulating solution outlet A5 at the bottom of the first-effect evaporator 10 is connected to the refrigerant inlet B1 of the first-effect heater 12 through the first-effect circulating pump 11, and the refrigerant outlet B2 of the first-effect heater 12 is connected to the circulating solution inlet A3 on the side of the first-effect evaporator 10; the circulating solution outlet A5 at the bottom of the second-effect evaporator 6 is connected to the refrigerant inlet B1 of the second-effect heater 8 through the second-effect circulating pump 7, and the refrigerant outlet B2 of the second-effect heater 8 is connected to the circulating solution inlet A3 on the side of the second-effect evaporator 6; each heater adopts a shell-and-tube heat exchanger, with the heat medium flowing through the shell side and the refrigerant flowing through the tube side. In each evaporation chamber, the dilute solution inlet A2 on the side of the evaporation chamber is located above the circulating solution inlet A3 on the side, and the circulating solution inlet A3 on the side is located above the concentrated solution outlet A4 on the side.

[0027] The ammonium nitrate refining method in the production of nitric acid phosphate fertilizer utilizes the above-mentioned system to achieve ammonium nitrate refining and evaporation, including the following steps: (1) Ammonium nitrate refining section: The raw material from the calcium nitrate to ammonium nitrate separation system—ammonium nitrate solution (containing NH4NO3 mass concentration of 60.12%)—enters the refining filter 1 through the ammonium nitrate solution inlet. Calcium carbonate particles are filtered out in the refining filter 1, and the filtered calcium carbonate particles are discharged from the bottom calcium carbonate outlet to the boundary area. The ammonium nitrate solution with the calcium carbonate particles removed exits the refining filter 1 through the side filter outlet and enters the pH control tank 2 through the top inlet of the pH control tank 2. Nitric acid (containing NH4NO3 mass concentration of 58%) and washing liquid (containing NH4NO3 mass concentration of 59.864%) from the boundary area are discharged from the top washing liquid / nitric acid outlet. The acid inlet enters the pH control tank 2, where it is stirred by the control tank stirrer 3. The nitric acid and ammonium nitrate solution are thoroughly mixed, and the pH value of the refined ammonium nitrate solution is controlled at 6.5. The refined ammonium nitrate solution overflows from the outlet on the side of the pH control tank 2 and enters the buffer tank 4 through the inlet on the side of the buffer tank 4. The refined ammonium nitrate solution in the buffer tank 4 exits from the outlet on the side of the buffer tank 4. Part of it is pumped by the dilute ammonium nitrate pump 5 to the branch pipe and enters the calcium nitrate to ammonium nitrate separation system for recycling. The other part of the refined ammonium nitrate solution (containing NH4NO3 with a mass concentration of 59.804%) enters the II-effect evaporation chamber 6 from the dilute ammonium nitrate inlet A2.

[0028] (2) Heating, evaporation and concentration section: The refined ammonium nitrate solution enters the evaporation chamber from the dilute ammonium nitrate inlet for evaporation and concentration. A portion of the refined ammonium nitrate solution after evaporation and concentration is discharged from the concentrated ammonium nitrate outlet. The other portion of the refined ammonium nitrate solution after evaporation and concentration enters the heater. After exchanging heat with steam in the heater, it re-enters the evaporation chamber through the circulating solution inlet. The tail gas generated in the evaporation chamber is discharged from the waste gas outlet at the top.

[0029] The heating, evaporation, and concentration section specifically includes the ammonium nitrate II-effect heating, evaporation, and concentration section and the ammonium nitrate I-effect heating, evaporation, and concentration section.

[0030] Ammonium nitrate II-effect heating, evaporation, and concentration section: Secondary steam (temperature 120℃, pressure 0.2MPa) from the top steam outlet A1 of the I-effect evaporation chamber 10 enters the shell side of the II-effect heater 8 through the heat medium inlet B3, exchanging heat with the II-effect circulating ammonium nitrate solution in the tube side. The secondary steam is cooled into condensate and discharged from the heat medium outlet B4 to the boundary area for reuse. Refined ammonium nitrate solution (containing 40.2% H2O) from the dilute ammonium nitrate pump 5 enters the II-effect evaporation chamber 6 through the dilute ammonium nitrate solution inlet A2. A portion of the II-effect ammonium nitrate solution (containing 29% water, temperature 85℃) in the II-effect evaporation chamber 6 is discharged from the side... The concentrated ammonium nitrate solution (29% water concentration, 85°C) exits from outlet A4 of the second-effect evaporator 6 and goes to feed pump 9. Another portion of the second-effect ammonium nitrate solution (29% water concentration, 85°C) in the second-effect evaporator 6 exits from the bottom circulating solution outlet A5 of the second-effect evaporator 6 and enters the second-effect heater 8 via refrigerant inlet B1 through the second-effect circulating pump 7. In the second-effect heater 8, the second-effect ammonium nitrate solution is heated and exits from refrigerant outlet B2 of the second-effect heater 8, then enters the second-effect evaporator 6 via the side circulating solution inlet A3 for evaporation and concentration. The tail gas (71°C, 0.033MPa) evaporated from the exhaust gas outlet A1 at the top of the second-effect evaporator 6 goes to the boundary area.

[0031] Ammonium nitrate I-effect heating, evaporation, and concentration section: Live steam (temperature 187℃, pressure 1.2MPa) from the boundary area enters the shell side of the I-effect heater 12 through the heat medium inlet B3, exchanging heat with the I-effect circulating ammonium nitrate solution in the tube side. The live steam is cooled into condensate and returned to the boundary area for reuse through the heat medium outlet B4. Ammonium nitrate solution (water content 29%, temperature 85℃) from the II-effect heater 10 from the feed pump 9 enters the I-effect evaporation chamber 10 through the side dilute solution inlet A2. A portion of the I-effect ammonium nitrate solution (water content 8%) in the I-effect evaporation chamber 10 exits from the side concentrated ammonium nitrate outlet A4 and enters the concentrated ammonium nitrate storage tank 13. The ammonium nitrate solution in the first-effect ammonium nitrate storage tank 13, as the target product, is a concentrated ammonium nitrate solution (with a water mass concentration of 8%). It is sent from the side outlet of the concentrated ammonium nitrate storage tank 13 to the nitric acid phosphate fertilizer concentrate production system via the concentrated ammonium nitrate pump 15. Another part of the first-effect ammonium nitrate solution (with a water mass concentration of 8%) in the first-effect evaporation chamber 10 exits from the bottom circulating solution outlet A5 of the first-effect evaporation chamber 10 and enters the first-effect heater 12 through the refrigerant inlet B1 via the first-effect circulating pump 11. In the first-effect heater 12, the first-effect ammonium nitrate solution is heated and exits from the refrigerant outlet B2 of the first-effect heater 12 through the side circulating solution inlet A3 into the first-effect evaporation chamber 10 for evaporation and concentration.

[0032] The performance evaluation results of the ammonium nitrate refining and evaporation system for the 100-ton / hour nitrate phosphate fertilizer plant are shown in Table 1.

[0033] Table 1

Claims

1. An ammonium nitrate refining system for the production of nitric acid phosphate fertilizer, characterized in that: It includes a refining filter, a pH control tank, a buffer tank, and a heating and concentration mechanism connected in sequence. The refining filter has an ammonium nitrate solution inlet at the bottom, a filter outlet at the top, and a calcium carbonate outlet at the bottom. The pH control tank is equipped with a stirrer, and has a dilute ammonium nitrate inlet and a washing liquid / nitric acid inlet at the top. The dilute ammonium nitrate inlet is connected to the filter outlet, and the washing liquid / nitric acid inlet is connected to the washing liquid and nitric acid pipelines from the boundary area. The outlet of the pH control tank is connected to the inlet of the buffer tank. The heating and concentration mechanism includes an evaporation chamber and a heater. The evaporation chamber has a tail gas outlet, a dilute solution inlet, a circulating solution inlet, a concentrated solution outlet, and a circulating solution outlet in sequence from top to bottom. The tail gas outlet is used to discharge steam. The dilute solution inlet is connected to the outlet of the buffer tank through a pipeline. The concentrated solution outlet is used to discharge the concentrated ammonium nitrate solution after evaporation and concentration. The circulating solution outlet and circulating solution inlet are respectively connected to the refrigerant inlet and refrigerant outlet of the heater. The heat medium inlet and heat medium outlet of the heater are respectively connected to the steam pipeline and the condensate pipeline.

2. The ammonium nitrate refining system in the production of nitric acid phosphate fertilizer according to claim 1, characterized in that: A branch pipe is connected to the pipe between the buffer tank and the dilute solution inlet of the evaporation chamber. The branch pipe is used to discharge part of the refined ammonium nitrate solution.

3. The ammonium nitrate refining system in the production of nitric acid phosphate fertilizer according to claim 1, characterized in that: The heating and concentration mechanism consists of two or more sets. Each set includes an evaporation chamber and a heater connected together. Along the flow direction of ammonium nitrate, the dilute solution inlet of the first evaporation chamber is connected to the outlet of the buffer tank. The tail gas outlet of the first evaporation chamber discharges steam to the outside. The concentrated solution outlet of the last evaporation chamber discharges concentrated ammonium nitrate solution to the outside. In two adjacent sets of heating and concentration mechanisms, the concentrated solution outlet of the previous evaporation chamber is connected to the dilute solution inlet of the next evaporation chamber. The heat medium inlet of the previous heater is connected to the tail gas outlet of the next evaporation chamber. The heat medium outlet of each heater discharges condensate to the outside.

4. The ammonium nitrate refining system in the production of nitric acid phosphate fertilizer according to claim 3, characterized in that: In two adjacent heating and concentration units, a feed pump is installed on the pipeline between the concentrated solution outlet of the first evaporation chamber and the dilute solution inlet of the next evaporation chamber.

5. The ammonium nitrate refining system in the production of nitric acid phosphate fertilizer according to claim 3, characterized in that: The concentrated solution outlet of the last evaporation chamber is connected to a concentrated ammonium nitrate storage tank via a pipeline. The concentrated ammonium nitrate storage tank is equipped with a stirrer, and a concentrated ammonium nitrate discharge pipeline is connected to the bottom of the concentrated ammonium nitrate storage tank. A concentrated ammonium nitrate pump is installed on the concentrated ammonium nitrate discharge pipeline.

6. The ammonium nitrate refining system in the production of nitric acid phosphate fertilizer according to claim 1, characterized in that: Both the evaporation chamber and the heater are vertical structures. A circulation pump is installed on the pipeline between the circulating solution outlet and the refrigerant inlet. A dilute ammonium nitrate pump is installed on the pipeline between the buffer tank and the dilute solution inlet of the heating and concentration mechanism.

7. The ammonium nitrate refining system in the production of nitric acid phosphate fertilizer according to claim 1, characterized in that: The pH control tank is positioned higher than the buffer tank. The outlet of the pH control tank is angled downwards, while the inlet of the buffer tank is angled upwards. The inlet of the buffer tank and the outlet of the pH control tank are on the same straight line.

8. A method for refining ammonium nitrate in the production of nitric acid phosphate fertilizer, wherein the method utilizes the ammonium nitrate refining system for the production of nitric acid phosphate fertilizer according to any one of claims 1-8, characterized in that, It includes the following steps: (1) Ammonium nitrate refining section: The raw material ammonium nitrate solution from the calcium nitrate to ammonium nitrate separation system enters the refining filter from the ammonium nitrate solution inlet. The calcium carbonate particles are filtered out in the refining filter. The filtered calcium carbonate particles are discharged from the calcium carbonate outlet at the bottom. The ammonium nitrate solution with the calcium carbonate particles removed exits the refining filter from the side filter outlet and enters the pH control tank from the top inlet of the pH control tank. Nitric acid and washing liquid from the boundary area enter the pH control tank through the washing liquid / nitric acid inlet at the top. In the pH control tank, the mixture is stirred by the control tank stirrer to fully mix the nitric acid and ammonium nitrate solution, controlling the pH value of the refined ammonium nitrate solution at 6-7. The refined ammonium nitrate solution overflows from the outlet on the side of the pH control tank and enters the buffer tank through the inlet on the side of the buffer tank. The refined ammonium nitrate solution in the buffer tank exits from the outlet on the side of the buffer tank. Part of it is pumped by the dilute ammonium nitrate pump to the branch pipe and enters the calcium nitrate to ammonium nitrate separation system for recycling. The other part of the refined ammonium nitrate solution enters the heating and concentration mechanism from the dilute ammonium nitrate inlet. (2) Heating, evaporation and concentration section: The refined ammonium nitrate solution enters the evaporation chamber from the dilute ammonium nitrate inlet for evaporation and concentration. A portion of the refined ammonium nitrate solution after evaporation and concentration is discharged from the concentrated ammonium nitrate outlet. The other portion of the refined ammonium nitrate solution after evaporation and concentration enters the heater. After exchanging heat with steam in the heater, it re-enters the evaporation chamber through the circulating solution inlet. The tail gas generated in the evaporation chamber is discharged from the waste gas outlet at the top.

9. The method for refining ammonium nitrate in the production of nitric acid phosphate fertilizer according to claim 8, characterized in that: The ammonium nitrate heating, evaporation, and concentration section includes a second-effect heating, evaporation, and concentration section and a first-effect heating, evaporation, and concentration section. Ammonium nitrate II-effect heating, evaporation and concentration section: Secondary steam from the top steam outlet of the I-effect evaporation chamber enters the shell side of the II-effect heater through the heat medium inlet, and exchanges heat with the II-effect circulating ammonium nitrate solution in the tube side. The secondary steam is cooled into condensate and discharged from the heat medium outlet to the boundary area for reuse. Refined ammonium nitrate solution from the dilute ammonium nitrate pump enters the II-effect evaporation chamber through the dilute ammonium nitrate solution inlet. A portion of the ammonium nitrate solution in the second-effect evaporation chamber exits from the side concentrated ammonium nitrate outlet and goes to the feed pump. Another portion of the ammonium nitrate solution in the second-effect evaporation chamber exits from the bottom circulating solution outlet of the second-effect evaporation chamber and enters the second-effect heater through the refrigerant inlet via the second-effect circulating pump. In the second-effect heater, the ammonium nitrate solution is heated and exits from the refrigerant outlet of the second-effect heater, then enters the second-effect evaporation chamber through the side circulating solution inlet for evaporation and concentration. The exhaust gas evaporated from the waste gas outlet at the top of the second-effect evaporation chamber goes to the boundary area. Ammonium nitrate I-effect heating, evaporation and concentration section: Live steam from the boundary area enters the shell side of the I-effect heater through the heat medium inlet, and exchanges heat with the I-effect circulating ammonium nitrate solution in the tube side. The live steam is cooled into condensate and returned to the boundary area for reuse through the heat medium outlet; Ammonium nitrate solution from the II-effect feed pump enters the I-effect evaporation chamber through the side dilute solution inlet. A portion of the ammonium nitrate solution in the first-effect evaporation chamber exits from the concentrated ammonium nitrate outlet on the side and enters the concentrated ammonium nitrate storage tank. The ammonium nitrate solution in the first-effect evaporation chamber, as the target product, is pumped from the concentrated ammonium nitrate storage tank outlet on the side to the nitric acid phosphate fertilizer concentrate production system. Another portion of the first-effect ammonium nitrate solution in the first-effect evaporation chamber exits from the bottom circulating solution outlet and enters the first-effect heater via the refrigerant inlet through the first-effect circulating pump. In the first-effect heater, the first-effect ammonium nitrate solution is heated and exits from the refrigerant outlet through the first-effect heater and enters the first-effect evaporation chamber through the side circulating solution inlet for evaporation and concentration.

10. The method for refining ammonium nitrate in the production of nitric acid phosphate fertilizer according to claim 8, characterized in that: The raw material ammonium nitrate solution contains 60.12% NH4NO3 by mass; the nitric acid from the boundary area contains 58% NH4NO3 by mass, and the washing liquid contains 59.864% NH4NO3 by mass. The refined ammonium nitrate solution contained 59.804% NH4NO3 by mass; the pH value of the refined ammonium nitrate solution was controlled at 6.5 in the pH control tank.

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