Method, product and system for co-producing iron phosphate through nitrophosphate fertilizer device

Abstract

The invention discloses a method, a product and a system for co-producing iron phosphate through a nitrophosphate fertilizer device. The method comprises the following steps: carrying out acidolysis on phosphorite by using nitric acid, and separating acid-insoluble substances to obtain an acidolysis solution; freezing and crystallizing the acidolysis solution, and carrying out solid-liquid separation to obtain a first solution; adding the first solution into a solution containing sulfate radicals for reaction to obtain a second solution; carrying out nitrate removal treatment on the second solution to obtain a third solution; adding ammonia into the third solution for neutralization, performing solid-liquid separation on the neutralized solution to obtain an ammonium phosphate salt solution, and adding an iron source into the ammonium phosphate salt solution for reaction to obtain iron phosphate. According to the method, the high-purity iron phosphate is prepared from the phosphorite raw material, the by-product in the production process can be directly used for fertilizer preparation or used as an independent product, and no waste is generated.

Description

Method, product and system for co-producing ferric phosphate through nitrophosphate fertilizer plant Technical Field

[0001] The present invention relates to the technical field of phosphate rock processing, and in particular to a method, product and system for co-producing iron phosphate through a nitrophosphate fertilizer device. Background Art

[0002] In general, the production of ferric phosphate involves the reaction of an iron source and a phosphorus source, using the prepared iron source and phosphoric acid to prepare the ferric phosphate. However, the present invention enables the preparation of ferric phosphate via two routes using nitrophosphate fertilizer equipment: one route is to prepare ferric phosphate from ammonium phosphate, and the other route is to prepare ferric phosphate from phosphoric acid. Both routes fully utilize the nitrophosphate fertilizer equipment to produce ferric phosphate.

[0003] Summary of the Invention

[0004] One embodiment of the present invention provides a method for co-producing ferric phosphate using a nitrophosphate fertilizer plant, comprising the following steps:

[0005] Phosphate rock or phosphate concentrate is acid-hydrolyzed with nitric acid, and acid-insoluble matter is separated to obtain an acid solution;

[0006] Freezing and crystallizing the acid hydrolyzed solution, and performing solid-liquid separation to obtain a first solution;

[0007] adding the first solution to a solution containing sulfate to perform decalcification to obtain a second solution A, and / or adding sulfuric acid to the first solution to perform a reaction, and performing solid-liquid separation to obtain a second solution B;

[0008] performing a denitration treatment on the second solution A and / or the second solution B to obtain a third solution A or a third solution B;

[0009] adding ammonia to the third solution A for neutralization, performing solid separation on the neutralized solution to obtain an ammonium phosphate solution, and adding an iron source to the ammonium phosphate solution for reaction to prepare iron phosphate;

[0010] And / or, the third solution B is pre-treated and extracted with an extraction solvent to obtain an extraction phase; the extraction phase is post-treated and stripped to obtain a phosphoric acid solution; and iron phosphate is obtained by reacting an iron source with the phosphoric acid solution.

[0011] The third solution B is extracted to remove metal ions to obtain a phosphoric acid solution.

[0012] In some embodiments, the acid hydrolysis solution is obtained by directly filtering and separating the liquid phase components in the acid hydrolysis slurry; or in other embodiments, the acid hydrolysis solution includes the liquid phase components in the acid hydrolysis slurry directly filtered and separated, and the washing solution obtained by washing the solid phase components decomposed by acid hydrolysis with process water once or multiple times.

[0013] In some embodiments, the acid hydrolysis solution of the phosphate concentrate primarily contains phosphate obtained by acid hydrolysis with nitric acid, and impurity metals such as calcium ions and nitrates. In a preferred embodiment, a relatively excessive amount of nitric acid may be added during the acid hydrolysis process to ensure complete reaction of the phosphate ore raw material.

[0014] In some embodiments, the acid-insoluble matter obtained by solid-liquid separation mainly contains silicon, calcium and magnesium salts; in a preferred embodiment, based on the effective utilization of the elements contained in the acid-insoluble matter, the acid-insoluble matter obtained by acid hydrolysis can be prepared into a soil conditioner product for use in improving the soil.

[0015] In some embodiments, the temperature of freezing and crystallizing the acid hydrolyzed solution is -10°C to -5°C, within which 60% to 85% of the calcium nitrate is precipitated in the form of Ca(NO3)2·4H2O crystals; the frozen solution is then filtered to promote the coagulation and precipitation of the crystals, thereby obtaining a first solution from which the impurity calcium is removed for the first time.

[0016] In a more preferred embodiment, the acid hydrolyzed liquid is frozen to a temperature of -8°C to -5°C and then directly fed into a double drum filter for filtration and separation. The liquid phase component obtained after filtration is the first solution.

[0017] Alternatively, in specific preferred implementation details, the solid phase component obtained after filtration separation, such as the filter cake obtained by filtration, is washed with frozen nitric acid and frozen water, and a portion of the washing liquid produced is recycled and combined into the acid hydrolysis liquid for re-freezing crystallization separation, and the other portion of the washing liquid is added to the acid hydrolysis tank for acid hydrolysis.

[0018] In some embodiments, a sulfate-containing solution, such as at least one of sulfuric acid and ammonium sulfate, is added to the first solution.

[0019] In a further embodiment, the sulfate-containing solution is not excessive to avoid the introduction of sulfate impurities; that is, the molar amount of sulfate added does not exceed the molar amount of calcium ions in the first solution to prevent the second solution A after decalcification from containing sulfate that affects the quality of phosphoric acid.

[0020] In another embodiment, the sulfate-containing solution is not excessive, and maintaining the sulfate concentration in the second solution below 0.5% after decalcification is beneficial for the subsequent removal of impurities; in a more preferred embodiment, the sulfate concentration in the second solution is maintained below 0.1% after decalcification; and even more preferably, the sulfate concentration in the second solution is maintained below 0.01% after decalcification.

[0021] In a preferred embodiment, the second solution A or the second solution B is subjected to denitration treatment by evaporating and concentrating the second solution to remove nitric acid.

[0022] In a preferred embodiment, the evaporation temperature for removing nitric acid by evaporating and concentrating the second solution A or B is adjustable between 70-90°C (vacuum degree 10-15 kPa); in a more preferred embodiment, the evaporation temperature for removing nitric acid is maintained at 70-90°C. When the nitrate concentration in the system is reduced to less than 0.1%, it is beneficial for the subsequent removal of metal impurities and the generation of phosphoric acid. Furthermore, in a more preferred embodiment, the evaporation concentration is reduced to less than 0.05%; more preferably, the evaporation concentration is reduced to less than 0.01%.

[0023] In a preferred embodiment, the concentration of nitrate ions in the third solution obtained by evaporating and concentrating the second solution to remove nitric acid is less than 0.05%. More preferably, the concentration of nitrate ions in the third solution is less than 0.01%.

[0024] In a preferred embodiment, the above extraction is a multi-stage cross-current extraction to make the extraction more efficient.

[0025] The term "multi-stage cross-current extraction" is a chemical engineering term that refers to a method of performing cross-current extraction in a multi-stage apparatus connected in series. Each stage comprises an extraction chamber and a re-extraction chamber. The donor phase contacts the extraction solvent in the extraction chamber, which is then re-extracted in the re-extraction chamber when it contacts the receiver phase. The extraction solvent flows in a cross-current manner with the donor and receiver phases within the same stage, while the donor and receiver phases flow in countercurrent through some or all of the stages.

[0026] In a preferred embodiment, it also includes:

[0027] The extracted phase obtained by the extraction is subjected to back extraction to separate phosphoric acid and an extraction solvent that can be recycled for extraction.

[0028] In a preferred embodiment, the extraction solvent includes at least one of n-butanol, isoamyl alcohol and tributyl phosphate.

[0029] In a preferred embodiment, an extraction solvent is used to extract and remove the third solution B, and the volume ratio of the extraction solvent to the third solution B is 0.5 to 5:1.

[0030] Furthermore, in some specific embodiments, the organic extraction solvent used in the above extraction step may include common metal ion extraction solvents such as n-butanol, isoamyl alcohol, sulfonated kerosene, No. 260 solvent oil, No. 406 environmentally friendly solvent oil, tributyl phosphate, and methyl isobutyl ketone. In a specific preferred embodiment, the extraction solvent used in step S50 is tributyl phosphate, and the ratio of tributyl phosphate to the mixed extraction solvent is 1:0.5-2, preferably 1:1. Furthermore, during the extraction, the volume ratio of the added extraction solvent to the third solution B is 0.5-5:1; preferably, the volume ratio of the added extraction solvent to the third solution B is 1-2:1.

[0031] In a preferred embodiment, before the stripping step of the extraction phase, the process further comprises:

[0032] washing the extraction phase to obtain a solution containing metal ions;

[0033] The solution containing metal ions is concentrated to obtain medium and trace element fertilizer products or as raw materials for fertilizer production.

[0034] In a preferred embodiment, it also includes:

[0035] The solution containing metal ions is used to prepare nitrophosphate fertilizer.

[0036] In a preferred embodiment, it also includes:

[0037] The acid used in the acid hydrolysis of the phosphate rock is at least partially derived from the nitric acid obtained by evaporating and removing nitrates from the second solution A or the second solution B.

[0038] In a preferred embodiment, the iron source includes at least one of ferric salt, ferrous salt or elemental iron, and the sulfate-containing solution is at least one of sulfuric acid solution and ammonium sulfate solution.

[0039] In a preferred embodiment, during the reaction of the iron source with the phosphoric acid solution, the pH value of the reaction system is controlled to be between 4 and 6.

[0040] In a preferred embodiment, the ammonia includes at least one of ammonia gas, liquid ammonia or ammonia water.

[0041] The present invention also provides an iron phosphate product prepared by the above method through the method of co-producing iron phosphate with a nitrophosphate fertilizer device.

[0042] The present invention also provides a system for co-producing ferric phosphate through a nitrophosphate fertilizer device, comprising:

[0043] Acid hydrolysis tank, used for acid hydrolysis of phosphate rock;

[0044] a first solid-liquid separation device for performing solid-liquid separation on the acid-hydrolyzed slurry after acid hydrolysis to obtain an acid-hydrolyzed liquid;

[0045] a freeze crystallization device, used for performing freeze crystallization on the acid hydrolyzed solution;

[0046] a second solid-liquid separation device for performing solid-liquid separation on the frozen crystallized acid hydrolyzed liquid to obtain a first solution;

[0047] a decalcification reaction device, configured to carry out a decalcification reaction between the first solution and a solution containing sulfate;

[0048] a third solid-liquid separation device, further used to perform solid-liquid separation on the product of the decalcification reaction to obtain a second solution;

[0049] a denitrification device for evaporating the second solution to remove nitrates, thereby obtaining a concentrated denitrified third solution and nitric acid;

[0050] an extraction device for extracting the third solution with an extraction solvent to obtain an extraction phase;

[0051] a stripping device for stripping the extract phase to obtain phosphoric acid;

[0052] And / or, the system is provided with a neutralization device and a fourth solid-liquid separation device, the neutralization device is used to perform a neutralization reaction between the third solution and ammonium to obtain a neutralization reaction solution, and the fourth solid-liquid separation device is used to perform solid-liquid separation on the neutralization reaction solution to obtain an ammonium phosphate salt solution.

[0053] In a preferred embodiment, the denitrification device is connected to an acidolysis tank, so that the nitric acid removed by the denitrification device enters the acidolysis tank.

[0054] In a preferred embodiment, the first solid-liquid separation device and / or the second solid-liquid separation device and / or the third solid-liquid separation device and / or the fourth solid-liquid separation device is a sedimentation tank, a filter press or a suction filter.

[0055] In a preferred embodiment, the first solid-liquid separation device, the second solid-liquid separation device, the third solid-liquid separation device and the fourth solid-liquid separation device are the same solid-liquid separation device that is cyclically used.

[0056] In a preferred embodiment, it also includes:

[0057] A stripping device is used to strip the extraction phase of the extraction device.

[0058] In a preferred embodiment, it also includes:

[0059] The washing device is located between the extraction device and the stripping device and is used to wash the extraction phase of the extraction device to obtain a washing liquid containing metal ions.

[0060] The first concentrating device concentrates the washing liquid containing metal ions to obtain a medium and trace element fertilizer product.

[0061] In a preferred embodiment, the extraction device comprises one of a rotary disc extraction tower, a multi-stage centrifugal extraction tower, a vibrating sieve plate tower or a sieve plate extraction tower.

[0062] In a preferred embodiment, it also includes:

[0063] The second concentrating device is used to concentrate the extracted phase of the stripping device.

[0064] The above preparation method utilizes nitrophosphate fertilizer equipment to prepare iron phosphate, and obtains high-purity iron phosphate from phosphate rock raw materials. The by-products in the production process can be directly used for fertilizer preparation or as independent products, and there is no waste. In addition, nitrophosphate fertilizer equipment is used to prepare iron phosphate through two pathways, namely, ammonium phosphate pathway and phosphoric acid pathway to produce iron phosphate. Both pathways are produced and prepared through nitrophosphate fertilizer equipment. The two pathways can be carried out separately or simultaneously. The by-product calcium sulfate is of high quality and can meet the application of industrial calcium sulfate such as building materials. The trace metal ions in the by-product extract and the neutralized precipitated phosphate metal salt can be used as raw materials for preparing fertilizers, and can also be directly used for fertilizer production. The by-product nitric acid can be recycled for phosphate rock decomposition, and can also be used for the preparation of iron sources, such as the preparation of ferric nitrate or ferrous nitrate. BRIEF DESCRIPTION OF THE DRAWINGS

[0065] FIG1 is a schematic diagram of a method for co-producing iron phosphate by a nitrophosphate fertilizer plant in one embodiment;

[0066] FIG2 is a schematic diagram of preparing an iron source in one embodiment;

[0067] FIG3 is a schematic diagram of multi-stage cross-current extraction, washing, and stripping to obtain phosphoric acid in one embodiment;

[0068] FIG4 is a schematic diagram of a system for co-producing iron phosphate through a nitrophosphate fertilizer plant in one embodiment;

[0069] FIG5 is a schematic diagram of a method for co-producing iron phosphate in a nitrophosphate fertilizer plant according to another embodiment;

[0070] FIG6 is a schematic diagram of a system for co-producing iron phosphate through a nitrophosphate fertilizer plant in yet another embodiment. DETAILED DESCRIPTION

[0071] The realization of the purpose, functional features and advantages of the present invention will be further described in conjunction with embodiments and with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only used to illustrate the present invention and are not intended to limit the present invention.

[0072] One embodiment of the present invention provides a method for co-producing iron phosphate through a nitrophosphate fertilizer device; the method uses phosphate rock and an iron source as raw materials to prepare and obtain iron phosphate.

[0073] In some embodiments, the phosphate rock or phosphate concentrate raw material used to prepare iron phosphate can be high-grade phosphate rock obtained by natural mining, and the phosphate concentrate is phosphate concentrate obtained by removing impurities or purifying medium- and low-grade phosphate rock.

[0074] FIG1 further shows a schematic diagram of a method for co-producing ferric phosphate in one embodiment, the method comprising:

[0075] S10, acid-hydrolyzing the phosphate rock or phosphate concentrate raw material with nitric acid or a mixed acid containing nitric acid, and separating and removing acid-insoluble matter to obtain an acid hydrolyzate;

[0076] S20, freezing the acid hydrolyzed solution to crystallize calcium nitrate, and filtering out the crystallized calcium nitrate to obtain a first solution;

[0077] S30, adding sulfuric acid solution to the first solution to further remove calcium to obtain a second solution;

[0078] S40, concentrating the second solution to volatilize excess nitric acid from the second solution, thereby obtaining a concentrated denitrified third solution;

[0079] S50, extracting the third solution obtained in step S40 to separate phosphoric acid and a portion of the metal ions from the third solution into an extraction phase; then washing the extraction phase to remove the metal ions; and back-extracting the washed extraction phase to return the phosphoric acid from the organic extraction solvent to the aqueous phase to obtain a phosphoric acid solution;

[0080] S60, preparing iron phosphate by reacting a phosphoric acid solution with an iron source.

[0081] In step S60, ferric phosphate is prepared by reacting an iron source with the phosphoric acid solution obtained in step S50. In some specific embodiments, the iron source includes at least one of an iron salt such as ferric sulfate, ferrous sulfate, ferric nitrate, ferrous nitrate, ferric chloride, or elemental iron such as iron powder.

[0082] For example, in a specific embodiment of FIG2 , the iron source is an iron salt solution obtained by dissolving and filtering an 85% by mass ferrous sulfate heptahydrate raw material, and then adding 25% ammonia water to further filter and remove impurities.

[0083] In a specific embodiment, an iron source is added to the phosphoric acid solution obtained in step S50, and the pH of the reaction system is preferably controlled within the range of 4 to 6 during the reaction. This is to avoid the precipitation of other metal impurities and insoluble ferrous phosphate when the pH of the reaction system is higher than 6, and to avoid the precipitation of ferric phosphate when the pH of the reaction system is lower than 4.

[0084] In a specific embodiment, the reaction product of the iron source and the phosphoric acid solution in step S60 is subjected to solid-liquid separation, and the solid phase component is ferric phosphate containing crystallization water, which is further dried to remove the crystallization water to obtain an anhydrous ferric phosphate product with higher purity. The liquid phase component of the solid-liquid separation of the product of the step S60 reaction also contains phosphate, nitrate, and other unprecipitated metal ions. In a further preferred embodiment, the method further includes:

[0085] The liquid phase component obtained by the solid-liquid separation in step S60 is used as a raw material for nitrophosphate fertilizer to prepare nitrophosphate fertilizer.

[0086] In some embodiments, the acid hydrolysis solution in step S10 is obtained by directly filtering and separating the liquid phase components in the acid hydrolysis slurry; or in other embodiments, the acid hydrolysis solution includes a combination of the liquid phase components directly filtered and separated from the acid hydrolysis slurry and the washing solution obtained by washing the solid phase components decomposed by acid hydrolysis with process water once or multiple times;

[0087] The acid hydrolysis solution of the phosphate concentrate mainly contains phosphate obtained by acid hydrolysis with nitric acid, and impurity metals such as calcium ions and nitrates. In a preferred embodiment, a relatively excessive amount of nitric acid may be added during the acid hydrolysis process to ensure complete reaction of the phosphate ore raw material.

[0088] In this embodiment, the acid-insoluble matter obtained by solid-liquid separation mainly contains acid-insoluble salts of silicon, calcium and magnesium; in a preferred embodiment, based on the effective utilization of the elements contained in the acid-insoluble matter, the acid-insoluble matter obtained by acid hydrolysis can be prepared into a soil conditioner product for use in improving the soil.

[0089] And in step S20, the acid hydrolyzed liquid is frozen to crystallize calcium nitrate, and the crystallized calcium nitrate is filtered out to obtain a first solution; specifically, in step S20, the acid hydrolyzed liquid is first frozen to crystallize, and during the freezing and crystallization process, a large amount of calcium ions and some metal ions such as magnesium are precipitated in the form of nitrate crystals; for example, the acid hydrolyzed liquid is frozen to a temperature of -10°C to -5°C, preferably -8°C to -5°C, and 60% to 85% of the calcium nitrate is precipitated in the form of Ca(NO3)2·4H2O crystals; and then the acid hydrolyzed liquid is directly sent to a vacuum filter for filtration and separation, and the liquid phase component obtained after filtration is the first solution.

[0090] Alternatively, in specific preferred implementation details, the solid phase components obtained after filtration separation, such as the filter cake obtained by filter pressing, are washed with frozen nitric acid and frozen water, and a portion of the washing liquid produced is used for system circulation and merged into the acid hydrolysis liquid for re-freezing crystallization separation, and the other portion of the washing liquid is added to the acid hydrolysis tank for acid hydrolysis.

[0091] And in step S30, sulfuric acid solution is added to the first solution to precipitate the remaining calcium ions in the first solution as slightly soluble or insoluble calcium sulfate, and solid-liquid separation is performed; the solid phase component obtained is calcium sulfate containing a certain amount of water, such as calcium sulfate hemihydrate, and a second solution that is further decalcified.

[0092] In an embodiment, the sulfate-containing solution is not excessive to avoid the introduction of sulfate impurities; that is, the molar amount of sulfate in the added sulfuric acid solution does not exceed the molar amount of calcium ions in the first solution to prevent the second solution after decalcification from containing sulfate that affects the quality of phosphoric acid.

[0093] In an embodiment, the sulfate-containing solution is not excessive, and maintaining the sulfate concentration in the second solution below 0.5% after decalcification is beneficial for the subsequent removal of impurities; in a more preferred embodiment, the sulfate concentration in the second solution is maintained below 0.1% after decalcification; more preferably, the sulfate concentration in the second solution is maintained below 0.01% after decalcification.

[0094] And in step S40, the second solution is concentrated to allow excess nitric acid to evaporate from the second solution, thereby obtaining a concentrated and denitrated third solution.

[0095] In a preferred embodiment, the evaporation temperature for removing nitric acid by evaporating and concentrating the second solution is adjustable between 120°C and 180°C. In a more preferred embodiment, the evaporation temperature for removing nitric acid is maintained at 160°C to 177°C. When the nitrate concentration in the system is reduced to less than 0.5%, it is beneficial for the subsequent removal of metal impurities and the generation of phosphoric acid. In a further more preferred embodiment, the evaporation concentration is reduced to less than 0.1%; more preferably, the evaporation concentration is reduced to less than 0.01%.

[0096] In an embodiment, the concentration of nitrate ions in the third solution obtained by evaporating and concentrating the second solution to remove nitric acid is less than 0.5%. More preferably, the concentration of nitrate ions in the third solution is less than 0.1%.

[0097] And in a preferred embodiment, the process method further reabsorbs or recovers the nitric acid removed in step S40 and uses it to acid-hydrolyze the phosphate rock raw material in step S10.

[0098] The third solution after concentration and removal of nitric acid mainly includes phosphoric acid and some impurities and metal ions.

[0099] And in step S50, the third solution obtained in step S40 is extracted to separate phosphoric acid and part of the metal ions from the third solution into an extraction phase; then the metal ions are removed from the extraction phase by washing; and the washed extraction phase is back-extracted to return phosphoric acid from the organic extraction solvent to the aqueous phase to obtain a phosphoric acid solution.

[0100] The terms "extraction" and "strip extraction" are both fundamental technical terms in the chemical industry. Extraction is the process of transferring a solute from one solvent to another, exploiting the differences in solubility or partition coefficients between two immiscible (or slightly soluble) solvents. Strip extraction is the reverse process, returning the solute from the extraction solvent.

[0101] Furthermore, in some specific embodiments, the organic extraction solvent used in the above extraction step can include commonly used metal ion extraction solvents such as n-butanol, isoamyl alcohol, sulfonated kerosene, No. 260 solvent oil, and No. 406 environmentally friendly solvent oil. In a specific preferred embodiment, the extraction solvent used in step S50 is a mixture of n-butanol and isoamyl alcohol, with the ratio of n-butanol to isoamyl alcohol in the mixed extraction solvent being 1:0.5-2, preferably, the ratio of n-butanol to isoamyl alcohol is 1:1. Furthermore, during the extraction, the amount of the extraction solvent added is in a volume ratio of 0.5-5:1 to the third solution.

[0102] In a further preferred embodiment, after the stripping step, the separated phosphoric acid solution is decolorized or concentrated. This not only further removes organic matter or fluorine from the solution, but also improves the appearance, color, and concentration of the product, thereby obtaining standardized high-purity industrial phosphoric acid. In one specific embodiment, the final high-purity phosphoric acid solution obtained through decolorization and concentration contains 61.58% by mass of P2O5.

[0103] On the other hand, in addition to obtaining phosphoric acid through stripping, the extraction solvent can also be reduced and purified so that the extraction solvent can be recycled.

[0104] In a preferred embodiment, the above extraction method is multi-stage cross-current extraction to make the extraction efficiency more sufficient.

[0105] The term "multi-stage cross-current extraction" is a chemical engineering term that refers to a method of performing cross-current extraction in a multi-stage apparatus connected in series. Each stage comprises an extraction chamber and a re-extraction chamber. The donor phase contacts the extraction solvent in the extraction chamber, which is then re-extracted in the re-extraction chamber when it contacts the receiver phase. The extraction solvent flows in a cross-current manner with the donor and receiver phases within the same stage, while the donor and receiver phases flow in countercurrent through some or all of the stages.

[0106] For example, FIG3 shows a schematic diagram of a multi-stage cross-current extraction in a specific embodiment; in this embodiment, multi-stage extraction, multi-stage washing and multiple back extractions are performed to improve the separation efficiency of the components in each step, thereby maximizing the purity of the final separated and prepared product.

[0107] In some specific embodiments, the solution containing metal ion impurities obtained by washing contains trace metal elements such as calcium, magnesium, manganese, etc., which are then added to phosphate fertilizers or fertilizer products to supplement the trace elements; or the solution containing metal ion impurities is concentrated and added to prepare an independent trace element fertilizer product.

[0108] Another embodiment of the present invention also provides a system for co-producing industrial phosphoric acid through a nitrophosphate fertilizer plant. In this preferred embodiment, the system for co-producing industrial phosphoric acid is shown in Figure 4 and includes:

[0109] Acid hydrolysis reaction device, which uses nitric acid or mixed acid to hydrolyze phosphate rock raw materials;

[0110] A first solid-liquid separation device is used to perform solid-liquid separation on the acid-hydrolyzed slurry after acid hydrolysis to obtain an acid-hydrolyzed liquid;

[0111] A freezing crystallization device is used to freeze and crystallize the acid hydrolyzed liquid;

[0112] a second solid-liquid separation device for performing solid-liquid separation on the acid hydrolyzed liquid of the freeze crystallization device to obtain the first solution and a solid phase of calcium nitrate crystalline hydrate;

[0113] a decalcification reaction device, used for reacting the first solution with the nitric acid solution;

[0114] The third solid-liquid separation device is also used to perform solid-liquid separation on the product of the decalcification reaction to obtain a second solution and solid calcium sulfate;

[0115] a denitrification device for concentrating and denitrifying the second solution to obtain a concentrated and denitrified third solution and nitric acid;

[0116] an extraction device for extracting the third solution with an organic extraction solvent to remove metal ions therein;

[0117] The washing device is located between the extraction device and the stripping device and is used to wash the extraction phase after the extraction device; after the washing liquid and the raffinate phase are combined, a phosphoric acid solution is obtained;

[0118] A stripping device for stripping the organic extraction solvent containing metal ions, i.e., the extraction phase, to obtain a phosphoric acid solution;

[0119] An iron phosphate reaction device for reacting phosphoric acid solution with an iron source to generate iron phosphate;

[0120] The fourth solid-liquid separation device performs solid-liquid separation on the reaction product of the ferric phosphate reaction device, and the solid phase component is the ferric phosphate product containing crystal water.

[0121] The denitrification device is connected to the acidolysis reaction device to allow nitric acid generated during evaporation and denitrification to enter the acidolysis tank for acidolysis.

[0122] Furthermore, the above system also includes:

[0123] The calcining device is used to calcine the solid phase components separated by the fourth solid-liquid separation device to obtain anhydrous ferric phosphate product.

[0124] And in some embodiments, the extraction device includes one of a rotating disk extraction column, a multi-stage centrifugal extraction column, a vibrating sieve plate column, or a sieve plate extraction column.

[0125] In some embodiments, the first solid-liquid separator, the second solid-liquid separator, and the third solid-liquid separator are independent separation devices or equipment; or in some other embodiments, the first solid-liquid separator, the second solid-liquid separator, and the third solid-liquid separator are a shared separation device or equipment, and the separation processes of the first solid-liquid separator, the second solid-liquid separator, and the third solid-liquid separator are performed in sequence in different steps. In some specific embodiments, the first solid-liquid separator, the second solid-liquid separator, and the third solid-liquid separator may include a sedimentation tank, a filter press, a suction filter, etc.

[0126] The above system of the present invention partially utilizes and improves the existing nitrophosphate fertilizer system to produce high-purity iron phosphate; the by-products in the production process can be directly used for fertilizer preparation or as an independent product, without waste.

[0127] In another embodiment of the present invention, a method for co-producing ferric phosphate is shown in FIG5 , and the method includes:

[0128] S10, acid-hydrolyzing the phosphate rock raw material with nitric acid or a mixed acid containing nitric acid, and separating and removing acid-insoluble matter to obtain an acid hydrolyzate;

[0129] S20, freezing the acid hydrolyzed solution to crystallize calcium nitrate, and filtering out the crystallized calcium nitrate to obtain a first solution;

[0130] S30, adding a sulfate-containing solution to the first solution to further remove calcium to obtain a second solution;

[0131] S40, concentrating the second solution to volatilize excess nitric acid from the second solution, thereby obtaining a concentrated denitrified third solution;

[0132] S50, adding ammonia, such as ammonia gas, liquid ammonia, or aqueous ammonia, to the third solution obtained in step S40 to perform a neutralization reaction, and filtering to obtain an ammonium phosphate solution;

[0133] S60, adding an iron source to the ammonium phosphate solution obtained in step S50 to react, and obtaining an iron phosphate product after solid-liquid separation.

[0134] And in step S60, at least one of an iron source such as ferric sulfate, ferrous sulfate, ferric nitrate, ferrous nitrate, ferric chloride, or elemental iron such as iron powder is reacted with the ammonium phosphate solution obtained in step S50 to obtain iron phosphate.

[0135] Likewise, during the reaction process of step S60, it is best to control the pH of the reaction system within the range of 4 to 6.

[0136] In a preferred embodiment, in step S50, the desired target product, ammonium phosphate, can be generated by neutralization by adding ammonia for neutralization reaction; on the other hand, during the neutralization reaction, the pH of the system gradually increases, and some metal ions such as calcium, magnesium, manganese, etc. will form solid phase precipitation, which helps to reduce and reduce impurities in the ammonium phosphate product, and then after filtering, impurities removal and concentration, a higher purity ammonium phosphate is obtained.

[0137] In a more preferred embodiment, the solid phase components separated by filtration in step S50 are mainly phosphates containing calcium, magnesium and manganese; these are then used as elements of nitrophosphate fertilizer to prepare nitrophosphate fertilizer.

[0138] In a more preferred embodiment, in step S50, ammonia gas is introduced into the third solution for neutralization reaction until the pH of the system reaches above 6. Preferably, when the pH of the system reaches above 6, impurity metal ions such as calcium, magnesium, and manganese in the system will precipitate in the form of phosphates, which is beneficial for reducing impurities and improving the purity of ammonium phosphate.

[0139] Further in some embodiments, ammonia is added to the third solution in step S50 to neutralize the pH of the reaction system, and the pH of the neutralization reaction system is adjustable between 4 and 7 according to the ratio or requirements of ammonium dihydrogen phosphate, ammonium monohydrogen phosphate and triammonium phosphate in the ammonium phosphate salt product to be prepared; by adjusting the pH range of the neutralization reaction system to different intervals, the proportion of ammonium dihydrogen phosphate, ammonium monohydrogen phosphate and triammonium phosphate in the prepared product can be adjusted.

[0140] Another embodiment of the present invention further provides a system for co-producing ferric phosphate, as shown in FIG5 , comprising:

[0141] Acid hydrolysis reaction device, which uses nitric acid or mixed acid to hydrolyze phosphate rock raw materials;

[0142] A first solid-liquid separation device is used to perform solid-liquid separation on the acid-hydrolyzed slurry after acid hydrolysis to obtain an acid-hydrolyzed liquid;

[0143] A freezing crystallization device is used to freeze and crystallize the acid hydrolyzed liquid;

[0144] a second solid-liquid separation device for performing solid-liquid separation on the acid hydrolyzed liquid of the freeze crystallization device to obtain the first solution and a solid phase of calcium nitrate crystalline hydrate;

[0145] a decalcification reaction device for reacting the first solution with a sulfate-containing solution such as sulfuric acid or ammonium sulfate;

[0146] The third solid-liquid separation device is also used to perform solid-liquid separation on the product of the decalcification reaction to obtain a second solution and solid calcium sulfate;

[0147] a denitrification device for concentrating and denitrifying the second solution to obtain a concentrated and denitrified third solution and nitric acid;

[0148] a neutralization device for performing a neutralization reaction between the third solution and ammonia;

[0149] The fourth solid-liquid separation device is used to filter and separate the system after the neutralization reaction, and the liquid phase is an ammonium phosphate salt solution;

[0150] The ferric phosphate reaction device is used to react the ammonium phosphate solution with the iron source to generate ferric phosphate;

[0151] The fifth solid-liquid separation device performs solid-liquid separation on the reaction product of the ferric phosphate reaction device to obtain a solid phase component, which is the ferric phosphate product containing crystal water.

[0152] The denitrification device is connected to the acidolysis reaction device to allow nitric acid generated during evaporation and denitrification to enter the acidolysis tank for acidolysis.

[0153] In some embodiments, the first solid-liquid separator, the second solid-liquid separator, the third solid-liquid separator, the fourth solid-liquid separator, and the fifth solid-liquid separator are independent separation devices or equipment; or in some other embodiments, the first solid-liquid separator, the second solid-liquid separator, the third solid-liquid separator, the fourth solid-liquid separator, and the fifth solid-liquid separator are shared separation devices or equipment, and the separation processes of the first solid-liquid separator, the second solid-liquid separator, the third solid-liquid separator, the fourth solid-liquid separator, and the fifth solid-liquid separator are performed in sequence in different steps. In some specific embodiments, the first solid-liquid separator, the second solid-liquid separator, the third solid-liquid separator, the fourth solid-liquid separator, and the fifth solid-liquid separator may include a sedimentation tank, a filter press, a suction filter, etc.

[0154] In a preferred embodiment, the denitration device comprises at least: a receiving chamber for receiving or accommodating the second solution; and a heater for heating and evaporating the second solution.

[0155] In a more preferred embodiment, the heater is a resistance heater and is configured to heat the second solution to 120-180° C. for evaporation during operation.

[0156] Furthermore, the above system also includes:

[0157] The calcining device is used to calcine the solid phase components separated by the fifth solid-liquid separation device to obtain anhydrous ferric phosphate product.

[0158] To demonstrate the efficiency of preparing the ferric phosphate product according to the present invention, the following Example 1 shows the material usage and output of the preparation process in a specific embodiment, including:

[0159] S10, 2 tons of phosphate concentrate containing 34% P2O5 (containing about 40.58% calcium as an impurity, about 0.77% magnesium as an impurity, and about 1-5% other impurities such as iron, aluminum, silicon, and fluorine) is acid-hydrolyzed with 2.4 tons of 100% nitric acid (0.53 tN), and the acid-hydrolyzed slurry is solid-liquid separated to obtain 0.09 tons of acid-insoluble matter (containing silicon, calcium, and magnesium raw materials) and an acid-hydrolyzed solution; the acid-insoluble matter is washed with water 2-3 times, and the washing solution is combined with the acid-hydrolyzed solution;

[0160] S20, freezing the acid solution to a temperature of -10°C to -5°C for crystallization, and then vacuum filtering the frozen solution at -2°C to 1°C to separate 3.54 tons of 60% crude calcium nitrate liquid crystal and 2.186 tons of the first solution (0.635 tons of P2O5);

[0161] S30, add 0.349t of sulfuric acid to the first solution, perform deep solid-liquid separation to obtain 0.51t of calcium sulfate hemihydrate and 2.055t of the second solution (0.635t of P2O5)

[0162] S40, evaporating and concentrating the second solution at 80-85° C. to remove nitrate, until the nitrate ion in the system is less than 0.01%, stopping the reaction, and recovering 0.473 tons of nitric acid and a third solution;

[0163] S50, performing multi-stage cross-current extraction on the third solution in an extraction tower using an organic extraction solvent (a 1:1 volume mixture of n-butanol and isoamyl alcohol) with a volume equal to one times that of the third solution, washing the extract with water, and finally back-extracting with pure water. After back-extraction and separation, a phosphoric acid solution is obtained;

[0164] S60, preparing an iron source: dissolving 2.3 t of purchased 85% ferrous sulfate heptahydrate in pure water, filtering and removing impurities, and then adding 0.93 t of 25% ammonia water to the solution for neutralization. After filtering and removing impurities again, an iron salt solution is obtained;

[0165] The iron salt solution was reacted with the phosphoric acid solution separated by stripping in step S50, and the pH of the reaction system was controlled to be 4-6. After the reaction was complete and sufficient precipitation was completed, solid-liquid separation was performed by filter pressing, and the filtrate was concentrated and crystallized to obtain 0.66 tons of ammonium sulfate product. The solid-liquid separation was performed twice, and 1.24 tons of iron phosphate containing crystallization water (including 0.48 tons of P2O5) was separated as a solid phase filter cake;

[0166] The ferric phosphate containing crystal water is further dried to remove the crystal water to obtain 1 t of anhydrous ferric phosphate; the P2O5 content in the anhydrous ferric phosphate is 48%, about 0.48 t of P2O5.

[0167] S70, concentrating the liquid phase component obtained from the solid-liquid separation in step S60 to prepare nitrophosphate fertilizer.

[0168] The following Example 2 shows the material usage and output of the preparation process in a specific embodiment, including:

[0169] S10, acid hydrolyzing 2 tons of phosphate concentrate containing 34% P2O5 with 2.4 tons (0.53 tN) of nitric acid, and separating the solid and liquid of the acid hydrolyzed slurry to obtain 0.09 tons of acid-insoluble matter (containing silicon, calcium, and magnesium raw materials) and an acid hydrolyzed solution; and washing the acid-insoluble matter with water 2 to 3 times, and combining the washing solution with the acid hydrolyzed solution;

[0170] S20, freezing the acid solution to a temperature of -10°C to -5°C for crystallization, and then vacuum filtering the cooled solution at -2°C to 1°C to separate 3.54 tons of 60% crude calcium nitrate liquid crystal and 2.186 tons of the first solution (0.635 tons of P2O5);

[0171] S30, add 0.349t of sulfuric acid to the first solution, perform deep solid-liquid separation to obtain 0.51t of calcium sulfate hemihydrate and 2.055t of the second solution (0.635t of P2O5)

[0172] S40, concentrating and denitrifying the second solution to recover 0.473 tons of nitric acid and a third solution;

[0173] S50, gradually adding 0.19t of ammonia to the third solution for neutralization reaction until the pH of the neutralization reaction system reaches 7.0, and then settling is complete, separation and purification are performed, and the liquid phase component is an ammonium phosphate solution;

[0174] S60, preparing an iron source: dissolving 2.3 t of purchased 85% ferrous sulfate heptahydrate in pure water, filtering and removing impurities, and then adding 0.93 t of 25% ammonia water to the solution for neutralization. After filtering and removing impurities again, an iron salt solution is obtained;

[0175] An iron salt solution was gradually added to the ammonium phosphate solution in step S50, and the pH of the reaction system was controlled to be between 4 and 6. After the reaction was complete and sufficient precipitation was achieved, solid-liquid separation was performed by filter pressing, and the filtrate was concentrated and crystallized to obtain 0.66 tons of ammonium sulfate product. The solid-liquid separation was performed twice, and 1.24 tons of iron phosphate containing crystal water (containing 0.48 tons of P2O5) was separated as a solid phase filter cake. After further calcination to remove the crystal water, 1 ton of anhydrous iron phosphate product (containing 48% P2O5) was obtained.

[0176] The above embodiments and specific scheme descriptions do not limit the scope of patent protection of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification, or directly or indirectly applied in other related technical fields, are also included in the scope of patent protection of the present invention.

Claims

1. A method for co-producing iron phosphate by a nitrophosphate fertilizer device, characterized in that: The steps include: Phosphate rock or phosphate concentrate is acid-hydrolyzed with nitric acid, and acid-insoluble matter is separated to obtain an acid solution; Freezing and crystallizing the acid hydrolyzed solution, and performing solid-liquid separation to obtain a first solution; adding the first solution to a solution containing sulfate to react, and performing solid-liquid separation to obtain a second solution A; and / or adding sulfuric acid to the first solution for reaction, and performing solid-liquid separation to obtain a second solution B; performing a denitration treatment on the second solution A and / or the second solution B to obtain a third solution A and / or a third solution B; adding ammonia to the third solution A for neutralization, performing solid separation on the neutralized solution to obtain an ammonium phosphate solution, and adding an iron source to the ammonium phosphate solution for reaction to prepare iron phosphate; and / or, pre-treating and extracting the third solution B with an extraction solvent to obtain an extract phase; and post-treating and back-extracting the extract phase to obtain a phosphoric acid solution; Iron phosphate is obtained by reacting an iron source with the phosphoric acid solution.

2. The method for co-producing iron phosphate by a nitrophosphate fertilizer device according to claim 1, characterized in that: The iron source includes at least one of ferric salt, ferrous salt or elemental iron, and the sulfate-containing solution is at least one of sulfuric acid solution and ammonium sulfate solution.

3. The method for co-producing ferric phosphate by a nitrophosphate fertilizer device according to claim 1 or 2, characterized in that: During the reaction of the iron source with the ammonium phosphate solution, the pH value of the reaction system is controlled to be between 4 and 6; during the reaction of the iron source with the phosphoric acid solution, the pH value of the reaction system is controlled to be between 4 and 6.

4. The method for co-producing ferric phosphate by a nitrophosphate fertilizer device according to claim 1 or 2, characterized in that: The concentration of nitrate in the third solution A and the third solution B is lower than 0.1%; more preferably, the concentration of nitrate in the third solution is lower than 0.05%; more preferably, the concentration of nitrate in the third solution is lower than 0.01%.

5. The method for co-producing ferric phosphate by a nitrophosphate fertilizer device according to claim 1 or 2, characterized in that: In extracting the third solution B with an extraction solvent, a volume ratio of the extraction solvent to the third solution B is 0.5 to 5:

1.

6. The method for co-producing ferric phosphate by a nitrophosphate fertilizer device according to claim 1, characterized in that: The ammonia includes at least one of ammonia gas, liquid ammonia or ammonia water.

7. A ferric phosphate product prepared by the method for co-producing ferric phosphate with a nitrophosphate fertilizer plant according to any one of claims 1 to 6.

8. A system for co-producing iron phosphate through a nitrophosphate fertilizer plant, characterized in that: include: Acid hydrolysis reaction device, used for acid hydrolysis of phosphate rock with nitric acid; a first solid-liquid separation device for performing solid-liquid separation on the acid-hydrolyzed slurry after acid hydrolysis to obtain an acid-hydrolyzed liquid; a freeze crystallization device, used for performing freeze crystallization on the acid hydrolyzed solution; a second solid-liquid separation device for performing solid-liquid separation on the frozen crystallized acid hydrolyzed liquid to obtain a first solution; a decalcification reaction device, used for reacting the first solution with a solution containing sulfate; a third solid-liquid separation device, further used to perform solid-liquid separation on the product of the decalcification reaction device to obtain a second solution; a denitration device, configured to evaporate the second solution to remove nitrate to obtain a third solution; an extraction device for pre-treating and extracting the third solution with an extraction solvent to obtain an extraction phase; a stripping device for post-processing and stripping the extract phase to obtain phosphoric acid; An iron phosphate reaction device is used to react an iron source with the phosphoric acid or ammonium phosphate solution to prepare iron phosphate. And / or, the system is provided with a neutralization device and a fourth solid-liquid separation device, the neutralization device is used to perform a neutralization reaction on the third solution and ammonia to obtain a neutralization reaction solution, and the fourth solid-liquid separation device is used to perform solid-liquid separation on the neutralization reaction solution to obtain an ammonium phosphate salt solution.

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