Methods, products and systems for co-producing ferric phosphate with nitrate phosphate fertilizer plants

Abstract

To provide a method of co-producing ferric phosphate using a nitric acid / phosphoric acid fertilizer device, a product, and a system.SOLUTION: The method includes: dissolving phosphate ore using an acid, i.e., nitric acid and separating a matter insoluble to an acid to obtain an acid solution; refrigerating / crystalizing the acid solution and carrying out solid / liquid separation to obtain a first solution; adding / reacting the first solution to / with a solution containing a sulfate to obtain a second solution; removing nitrates from the second solution to obtain a third solution; adding ammonia to the third solution to neutralize the same; carrying out solid / liquid separation of the neutralized solution to obtain an ammonium phosphate solution; and adding / reacting an iron source to / with the ammonium phosphate solution to prepare ferric phosphate. According to the present invention, ferric phosphate of high purity is obtained from phosphate ore, and byproducts produced in the production process can be used for producing a fertilizer or can be used as an independent product as they are, and hence waste is eliminated.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to the technical field of phosphate rock processing, and in particular to methods, products and systems for co-producing ferric phosphate with a nitrate phosphate fertilizer plant. [Background technology]

[0002] Ferric phosphate is usually produced by reacting an iron source with a phosphorus source to prepare ferric phosphate using an already prepared iron source and phosphoric acid. However, the present invention makes it possible to use the nitrate phosphate fertilizer apparatus to prepare ferric phosphate in two ways: a method of preparing ferric phosphate using ammonium phosphate salt, and a method of preparing ferric phosphate using phosphoric acid, and ferric phosphate can be produced by utilizing the nitrate phosphate fertilizer apparatus. Summary of the Invention [Problem to be solved by the invention]

[0003] One embodiment of the present invention is a method for co-producing ferric phosphate with a nitrate phosphate fertilizer system, comprising: acid digestion of phosphate rock or phosphate concentrate with nitric acid and separation of acid insoluble matter to obtain an acid solution; freezing and crystallizing the acid solution and performing solid-liquid separation to obtain a first solution; Adding the first solution to a solution containing sulfate, reacting the solution, and performing solid-liquid separation to obtain a second solution A, and / or adding the first solution to sulfuric acid, reacting the solution, and performing solid-liquid separation to obtain a second solution B; treating the second solution A and / or the second solution B to remove nitrates to obtain a third solution A and / or a third solution B; adding ammonia to the third solution A to neutralize it, subjecting the neutralized solution to solid-liquid separation to obtain an ammonium phosphate salt solution, and adding an iron source to the ammonium phosphate salt solution to react with it to prepare ferric phosphate; and / or pre-treating and extracting the third solution B with an extraction solvent to obtain an extract phase, post-treating and back-extracting the extract phase to obtain a phosphoric acid solution, and reacting an iron source with the phosphoric acid solution to obtain ferric phosphate.

[0004] The third solution B is extracted to remove metal ions to obtain a phosphoric acid solution.

[0005] In some embodiments, the acid solution is obtained by directly filtering and separating the liquid phase components in the acid decomposition slurry, or in some embodiments, the acid solution is obtained by a combination of directly filtering and separating the liquid phase components in the acid decomposition slurry and washing the solid phase components of the acid decomposition with process water one or more times to obtain a wash solution.

[0006] In some embodiments, the acid solution of the phosphate concentrate mainly comprises phosphate obtained by nitric acid decomposition, impurity metals including calcium ions, nitrates, etc. In a preferred embodiment, the nitric acid added during the acid decomposition process may be in relative excess to completely react the phosphate rock feedstock.

[0007] In some embodiments, the acid-insoluble matter obtained by solid-liquid separation mainly comprises silica-calcium-magnesium salts, and in a preferred embodiment, the acid-insoluble matter obtained by acid decomposition is prepared into a soil conditioner product to improve soil based on the effective utilization of the elements contained in the acid-insoluble matter.

[0008] In some embodiments, the temperature of the acid solution freezing and crystallization is -10°C to -5°C, in which 60-85% of calcium nitrate precipitates as Ca(NO3)2·4H2O crystals, and then the frozen solution is filtered to promote the solidification and precipitation of the crystal particles to obtain the first solution of the first calcium impurity removal.

[0009] In a more preferred embodiment, the acid solution is frozen to a temperature of −8° C. to −5° C., and then directly fed to a double drum filter for filtration and separation, and the liquid phase component obtained after filtration is used as the first solution.

[0010] Or in a specific preferred embodiment, the solid phase component obtained after filtration is filtered to obtain a filter cake, the filter cake is washed with frozen nitric acid and frozen water, a part of the generated washing liquid is circulated and combined with the acid solution to be frozen and crystallized and separated again, and the other part of the washing liquid is added to an acid decomposition tank to carry out acid decomposition.

[0011] In some embodiments, the first solution comprises a sulfate-containing solution, such as at least one of sulfuric acid, ammonium sulfate.

[0012] In another embodiment, the solution containing sulfate is not in excess to avoid the introduction of sulfate impurities, i.e. the molar amount of sulfate added is equal to or less than the molar amount of calcium ions in the first solution, to prevent sulfate from affecting the phosphoric acid quality of the second solution A after decalcification.

[0013] In another embodiment, the solution containing sulfate is not in excess, and maintaining the concentration of sulfate in the second solution after decalcification at less than 0.5% is advantageous for subsequent impurity removal, and in a more preferred embodiment, the concentration of sulfate in the second solution after decalcification is maintained at less than 0.1%, and more preferably, the concentration of sulfate in the second solution after decalcification is maintained at less than 0.01%.

[0014] In a preferred embodiment, the treatment of the second solution A or the second solution B to remove nitrates is carried out by concentrating the second solution by evaporation to remove nitric acid.

[0015] In a preferred embodiment, the evaporation temperature at which the second solution A or B is concentrated by evaporation to remove nitric acid can be adjusted between 70 and 90° C. (vacuum degree 10 to 15 kpa), and in a more preferred embodiment, the temperature at which the evaporation is performed to remove nitric acid is maintained at 70 to 90° C. Evaporation to reduce the concentration of nitrates in the system to less than 0.1% is advantageous for the subsequent removal of metal impurities and the production of phosphoric acid, and further, in a more preferred embodiment, the concentration of nitrates in the system is concentrated by evaporation to less than 0.05%, and more preferably, the concentration of nitrates in the system is concentrated by evaporation to less than 0.01%.

[0016] In a preferred embodiment, after the second solution is concentrated by evaporation to remove nitric acid, the third solution contains a nitrate ion concentration of less than 0.05%, more preferably, the third solution contains a nitrate ion concentration of less than 0.01%.

[0017] In a preferred embodiment, the above extraction is a multi-stage cross-flow extraction to ensure efficient and thorough extraction.

[0018] The term "multi-stage cross-flow extraction" is a chemical industry term and refers to a method of performing multi-stage cross-flow extraction using a multi-stage serial apparatus. Each stage includes an extraction chamber and a re-extraction chamber. The donor phase and the extraction solvent are contacted in the extraction chamber, and the extraction solvent is re-extracted by contacting with the receiver phase in the re-extraction chamber. The extraction solvent crosses the donor phase and the receiver phase appropriately in the same stage, and the donor phase and the receiver phase counterflow in some or all stages.

[0019] In a preferred embodiment, The method further comprises the step of back-extracting the extracted phase obtained by the extraction to obtain phosphoric acid and a reusable extraction solvent by separation.

[0020] In a preferred embodiment, the extraction solvent comprises at least one of n-butanol, isoamyl alcohol, and tributyl phosphate.

[0021] In a preferred embodiment, in extracting and removing the third solution B with an extraction solvent, the volume ratio of the extraction solvent to the third solution B is 0.5 to 5:1.

[0022] In some specific embodiments, the organic extraction solvent employed in the above extraction steps may include commonly used metal ion extraction solvents such as n-butanol, isoamyl alcohol, sulfonated paraffin, 260 solvent oil, 406# environmental protection solvent oil, tributyl phosphate, methyl isobutyl ketone, etc. In a specific preferred embodiment, the extraction solvent employed in step S50 is tributyl phosphate, and the ratio of tributyl phosphate in the mixed extraction solvent is 1:0.5-2, preferably 1:1. In the extraction, the volume ratio of the amount of the extraction solvent added to the third solution B is 0.5-5:1, preferably the volume ratio of the amount of the extraction solvent added to the third solution B is 1-2:1.

[0023] In a preferred embodiment, prior to the step of back-extracting the extraction phase, washing the extraction phase to obtain a solution containing metal ions; The method further includes concentrating the solution containing metal ions to obtain a medium trace element fertilizer product or a fertilizer production feedstock.

[0024] In a preferred embodiment, The method further comprises using the metal ion-containing solution in the preparation of a nitrate phosphate fertilizer.

[0025] In a preferred embodiment, The acid in the acid decomposition of the phosphate rock further includes at least a part of nitric acid obtained by removing nitrates from the second solution A or the second solution B by evaporation.

[0026] In a preferred embodiment, the iron source comprises at least one of an iron salt, a ferrous salt, or an iron monomer, and the sulfate-containing solution is at least one of a sulfuric acid solution, an ammonium sulfate solution.

[0027] In a preferred embodiment, the pH value of the reaction system is controlled to 4 to 6 in the reaction between the iron source and the phosphoric acid solution.

[0028] In a preferred embodiment, the ammonia comprises at least one of ammonia gas, liquid ammonia, or aqueous ammonia.

[0029] The present invention further provides a ferric phosphate product prepared according to the above method for co-producing ferric phosphate with a nitrate phosphate fertilizer system.

[0030] The present invention further provides a system for co-producing ferric phosphate with a nitrate phosphate fertilizer plant, the system comprising: an acid decomposition reaction device for decomposing and reacting phosphate rock with nitric acid; a first solid-liquid separation device for performing solid-liquid separation of the acid decomposition slurry after the acid decomposition to obtain an acid solution; a freezing and crystallization device for freezing and crystallizing the acid solution; a second solid-liquid separation device for performing solid-liquid separation of the frozen and crystallized acid solution to obtain a first solution; a descaling reactor for reacting the first solution with a sulfate-containing solution; a third solid-liquid separator for performing solid-liquid separation of the product of the descaling reaction apparatus to obtain a second solution; a denitration device for evaporating the second solution to remove nitrates and obtain a third solution; an extraction apparatus for pre-treating and extracting the third solution with an extraction solvent to obtain an extraction phase; a stripping device for working up the extract phase and stripping it to obtain phosphoric acid; a ferric phosphate reactor for reacting an iron source with the phosphoric acid or ammonium phosphate salt solution to prepare ferric phosphate; and / or a neutralization device for neutralizing the third solution with ammonia to obtain a neutralized reaction solution, and a fourth solid-liquid separation device for performing solid-liquid separation of the neutralized reaction solution to obtain an ammonium phosphate salt solution.

[0031] In a preferred embodiment, the denitration device is connected to an acid decomposition tank, and nitric acid removed by the denitration device enters the acid decomposition tank.

[0032] 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 one of a settler, a filter press or a filter extractor.

[0033] 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 reusable solid-liquid separation device.

[0034] In a preferred embodiment, The apparatus further includes a back-extraction apparatus for back-extracting the extract phase of the extractor.

[0035] In a preferred embodiment, a washing device disposed between the extraction device and the back extraction device for washing the extraction phase of the extraction device to obtain a washing solution containing metal ions; and a first concentrator for concentrating the metal ion-containing washing solution to obtain a medium trace element fertilizer product.

[0036] In a preferred embodiment, the extraction apparatus comprises one of a rotary extraction column, a multi-stage centrifugal extraction column, a vibrating sieve plate column, or a sieve plate extraction column.

[0037] In a preferred embodiment, The apparatus further includes a second concentrator for concentrating the effluent phase of the stripper.

[0038] According to the above preparation method, ferric phosphate is prepared by the nitric acid phosphate fertilizer equipment, and high purity ferric phosphate is obtained by producing it from phosphate rock as raw material. The by-product during the production process can be used directly in fertilizer preparation or as an independent product, and no waste is generated. The nitric acid phosphate fertilizer equipment makes it possible to prepare ferric phosphate using ammonium phosphate salt and to prepare ferric phosphate using phosphoric acid. Both of these methods are produced by the nitric acid phosphate fertilizer equipment, and the two methods can be carried out separately or simultaneously. The by-product calcium sulfate has high quality and can be used for building materials and industrial calcium sulfate. The medium and trace metal ions in the by-product extract and the neutralized precipitate, which is the phosphate metal salt, can both be used as raw materials for fertilizer preparation and can be directly produced as fertilizer. The by-product nitric acid can be recycled for phosphate rock decomposition and can also be used for preparing iron sources, such as preparing ferric nitrate or ferrous nitrate. [Brief description of the drawings]

[0039] [Figure 1] FIG. 1 is a schematic diagram illustrating a process for co-producing ferric phosphate with a nitrate phosphate fertilizer system in one embodiment. [Diagram 2] FIG. 1 is a schematic diagram showing the preparation of an iron source in one embodiment. [Diagram 3] FIG. 1 is a schematic diagram showing the production of phosphoric acid by multi-stage cross-flow extraction, washing and stripping in one embodiment. [Figure 4] FIG. 1 is a schematic diagram illustrating a system for co-producing ferric phosphate with a nitrate phosphate fertilizer plant in one embodiment. [Diagram 5] FIG. 2 is a schematic diagram showing a method for co-producing ferric phosphate with a nitrate phosphate fertilizer system in another embodiment. [Figure 6] FIG. 1 is a schematic diagram showing a system for co-producing ferric phosphate with a nitrate phosphate fertilizer plant in another embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0040] The objects, features and advantages of the present invention will be further described in conjunction with the embodiments with reference to the drawings. Note that the specific embodiments described herein are used only for the purpose of interpreting the present invention, and are not intended to limit the present invention.

[0041] One embodiment of the present invention provides a method for co-producing ferric phosphate by a nitrate phosphate fertilizer plant, which obtains ferric phosphate by preparing it from phosphate rock and an iron source.

[0042] In some embodiments, the phosphate rock or phosphate concentrate raw material for preparing ferric phosphate is naturally extracted high-quality phosphate rock, and the phosphate concentrate is a phosphate concentrate obtained by removing impurities and refining low- or medium-quality phosphate rock.

[0043] FIG. 1 is a schematic diagram showing a method for co-producing ferric phosphate in one embodiment, the method comprising: S10, acid-decomposing the phosphate rock or phosphate concentrate raw material with nitric acid or a mixed acid containing nitric acid, and separating and removing the acid insolubles and acid solution; S20, freezing the acid solution to crystallize calcium nitrate, and removing the crystallized calcium nitrate by filtration to obtain a first solution; S30, adding a sulfuric acid solution to the first solution to further remove calcium to obtain a second solution; S40, concentrating the second solution and volatilizing excess nitric acid from the second solution to obtain a concentrated denitrified third solution; S50, extracting the third solution obtained in step S40, separating phosphoric acid and some of the metal ions from the third solution into an extraction phase, then removing the metal ions from the extraction phase by washing, and back-extracting the washed extraction phase to return phosphoric acid from the organic extraction solvent to the aqueous phase to obtain a phosphoric acid solution; S60, reacting the phosphoric acid solution with the iron source to prepare ferric phosphate.

[0044] In step S60, an iron source is reacted with the phosphoric acid solution obtained in step S50 to prepare ferric phosphate, where in some specific embodiments the iron source comprises at least one of an iron salt, such as ferric sulfate, ferrous sulfate, ferric nitrate, ferrous nitrate, ferric chloride, or monomeric iron, such as iron powder.

[0045] For example, in one specific embodiment of FIG. 2, the iron source is an iron salt solution obtained by dissolving and filtering 85% by weight ferrous sulfate heptahydrate raw material, followed by addition of 25% aqueous ammonia and further filtering to remove impurities.

[0046] In a specific embodiment, an iron source is added to the phosphoric acid solution obtained in step S50, and during the reaction, the pH of the reaction system is preferably controlled in the range of 4 to 6. When the pH of the reaction system is higher than 6, other metal impurities and poorly soluble ferrous phosphate are precipitated in large quantities, whereas when the pH of the reaction system is lower than 4, precipitation of ferric phosphate is difficult to occur.

[0047] 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, the solid phase component is ferric phosphate containing water of crystallization, and after further drying to remove the water of crystallization, a higher purity anhydrous ferric phosphate product is obtained. The liquid phase component obtained by solid-liquid separation of the reaction product in step S60 also contains phosphate, nitrate, and other unprecipitated metal ions. In an even more preferred embodiment, the method includes the following steps: The method further includes a step of preparing a nitrate phosphate fertilizer using a liquid phase component obtained by solid-liquid separation of the product of step S60 as a nitrate phosphate fertilizer raw material. In some embodiments, the acid solution in step S10 is obtained by directly filtering and separating the liquid phase components of the acid decomposition slurry, or in some embodiments, the acid solution is obtained by combining the liquid phase components of the acid decomposition slurry obtained by directly filtering and separating them, and the washing liquid obtained by washing the solid phase components of the acid decomposition with process water one or more times; The acid solution of the phosphate concentrate mainly includes phosphate obtained by nitric acid decomposition, impurity metals such as calcium ions, nitrates, etc. In a preferred embodiment, the nitric acid added during the acid decomposition process may be in relatively excess in order to completely react the phosphate rock raw material.

[0048] In this embodiment, the acid-insoluble matter obtained by solid-liquid separation mainly contains acid-insoluble salts of silica-calcium-magnesium, and 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 decomposition is prepared into a soil conditioner product to improve soil.

[0049] In step S20, the acid solution is frozen to crystallize calcium nitrate, and the crystalline calcium nitrate is filtered to obtain a first solution; specifically, in step S20, the acid solution is first frozen and crystallized; during the freezing and crystallization process, a large amount of calcium ions and some metal ions, such as magnesium, will precipitate as nitrate crystals; for example, the temperature of the acid solution is frozen to -10°C to -5°C, preferably -8°C to -5°C, and 60-85% of calcium nitrate will precipitate as Ca(NO3)2·4H2O crystals; then the solution is fed to a vacuum filter for filtering and separating; the liquid phase component after filtration is the first solution.

[0050] Alternatively, in a specific preferred embodiment, the solid phase component obtained after filtration is press-filtered to obtain a press filter cake, the filter cake is washed with frozen nitric acid and frozen water, a part of the washing liquid is used for system circulation to be combined with the acid solution and frozen and crystallized again for separation, and the other part of the washing liquid is added to an acid decomposition tank for acid decomposition.

[0051] In step S30, a sulfuric acid solution is added to the first solution, and the remaining calcium ions in the first solution are precipitated as slightly or poorly soluble calcium sulfate, and solid-liquid separation is performed. The resulting solid phase components are calcium sulfate containing a certain amount of water, such as calcium sulfate hemihydrate, and a second solution from which calcium has been further removed.

[0052] In an embodiment, the sulfate-containing solution is not in excess to avoid contamination with sulfate impurities, i.e., the molar amount of sulfate in the added sulfuric acid solution is equal to or less than the molar amount of calcium ions in the first solution, so as not to contain sulfate that would affect the phosphoric acid quality in the second solution after decalcification.

[0053] In an embodiment, the solution containing sulfate is not in excess, and maintaining the concentration of sulfate in the second solution after decalcification at less than 0.5% is advantageous for subsequent removal of impurities, and in a more preferred embodiment, the concentration of sulfate in the second solution after decalcification is maintained at less than 0.1%, and more preferably, the concentration of sulfate in the second solution after decalcification is maintained at less than 0.01%.

[0054] In step S40, the second solution is concentrated to volatilize excess nitric acid from the second solution, thereby obtaining a concentrated, denitrified third solution.

[0055] In a preferred embodiment, the evaporation temperature for removing nitric acid by evaporating and concentrating the second solution can be adjusted between 120 and 180° C., and in a more preferred embodiment, the temperature for removing nitric acid by evaporating and concentrating is maintained at 160 to 177° C. Evaporating the nitrate salts in the system to a concentration of less than 0.5% is advantageous for the subsequent removal of metal impurities and the production of phosphoric acid, and in an even more preferred embodiment, the nitrate salts in the system are evaporated and concentrated to a concentration of less than 0.1%, and more preferably, the nitrate salts in the system are evaporated and concentrated to a concentration of less than 0.01%.

[0056] In an embodiment, the third solution obtained by evaporating and concentrating the second solution to remove nitric acid has a nitrate ion concentration of less than 0.5%. More preferably, the third solution has a nitrate ion concentration of 0.1%.

[0057] In a preferred embodiment, the process involves re-absorbing or recovering the nitric acid removed in step S40 and then using it to acid-digest the phosphate rock feedstock in step S10.

[0058] The third solution after concentrating and removing the nitric acid mainly contains phosphoric acid, some impurities and metal ions.

[0059] In step S50, the third solution obtained in step S40 is extracted to separate phosphoric acid and some of the metal ions from the third solution into an extraction phase, and then the metal ions are washed and removed from the extraction phase by washing, and the extracted phase after washing is back-extracted to return phosphoric acid from the organic extraction solvent to the aqueous phase to obtain a phosphoric acid solution.

[0060] The terms "extraction" and "stripping" are both basic technical terms in the chemical industry. Here, "extraction" refers to the process of transferring a solute substance from one solvent to another by utilizing the difference in solubility or distribution coefficient between two solvents that are insoluble (or slightly soluble) in each other. "Stripping" is the reverse process of "extraction" and is the process of returning a solute substance from the extraction solvent.

[0061] In some specific embodiments, the organic extraction solvent employed in the above extraction steps may include commonly used metal ion extraction solvents such as n-butanol, isoamyl alcohol, sulfonated paraffin, 260 solvent oil, 406# environmental protection solvent oil, etc. In a specific preferred embodiment, the extraction solvent employed in step S50 is a mixture of n-butanol and isoamyl alcohol, and the ratio of n-butanol to isoamyl alcohol in the mixed extraction solvent is 1:0.5-2, preferably, the ratio of n-butanol to isoamyl alcohol is 1:1. During extraction, the volume ratio of the extraction solvent added to the third solution is 0.5-5:1.

[0062] In an even more preferred embodiment, after the back-extraction step, the phosphoric acid solution separated by back-extraction is decolorized or concentrated, etc., to further remove organic matter or elemental fluorine in the solution, while improving the appearance, color, and concentration, etc., of the product, to obtain a standardized product of high-purity industrial phosphoric acid. In a specific embodiment, the decolorized and concentrated final high-purity phosphoric acid solution contains 61.58% P2O5 by mass.

[0063] On the other hand, in addition to obtaining phosphoric acid by stripping, the extraction solvent can be recycled by reducing and purifying it.

[0064] In a preferred embodiment, the above extraction method is a multi-stage cross-flow extraction, which can make the extraction more efficient.

[0065] "Multistage cross-flow extraction" is a chemical industry term that refers to a method of performing multistage cross-flow extraction in multiple stages connected in series. Each stage includes an extraction chamber and a re-extraction chamber. In the extraction chamber, the donor phase is in contact with the extraction solvent, and the latter is re-extracted in the re-extraction chamber by contacting the receiver, the extraction solvent is cross-flowed to both the donor and receiver phases in a suitable manner in the same stage, and the donor and receiver phases are counter-flowed in some or all stages.

[0066] For example, Figure 3 is a schematic diagram showing multi-stage cross-flow extraction in a specific embodiment, in which the separation efficiency of components in each step can be improved by multi-stage extraction, multi-stage washing and multiple back extraction, and the final separation and preparation product purity can be improved.

[0067] In some exemplary embodiments, the solution containing metal ion impurities after washing contains trace or medium-level metal elements, such as calcium, magnesium, manganese, etc., and is added to a phosphate fertilizer or fertilizer product to replenish the trace or medium-level elements, or the solution containing metal ion impurities is concentrated and added to prepare a separate trace or medium-level fertilizer product.

[0068] Another embodiment of the present invention further provides a system for co-producing industrial phosphate with a nitrate phosphate fertilizer unit. In this preferred embodiment, the system for co-producing industrial phosphate, as shown in FIG. 4, includes: an acid decomposition reactor for decomposing the phosphate rock raw material with nitric acid or a mixed acid; a first solid-liquid separation device for performing solid-liquid separation of the acid decomposition slurry after the acid decomposition to obtain an acid solution; a refrigeration and crystallization device for freezing and crystallizing the acid solution; a second solid-liquid separator for subjecting the acid solution of the refrigeration and crystallization apparatus to solid-liquid separation to obtain a first solution and a solid phase calcium nitrate crystal hydrate; a descaling reactor for reacting the first solution with a nitric acid solution; a third solid-liquid separator for subjecting the product of the decalcification reaction to solid-liquid separation to obtain a second solution and calcium sulfate in a solid phase; a denitration device for concentrating and denitrating the second solution to obtain a concentrated and denitrated third solution and nitric acid; an extraction apparatus for extracting the third solution with an organic extraction solvent to remove metal ions therein; a washing device provided between the extractor and the stripping device for washing the extracted phase extracted by the extractor and combining the washing liquid with the extracted residual phase to obtain a phosphoric acid solution; a stripping apparatus for stripping the metal ion-containing organic extractant or extraction phase to obtain a phosphoric acid solution; a ferric phosphate reactor for reacting the phosphoric acid solution with an iron source to produce ferric phosphate; and a fourth solid-liquid separation device for subjecting the reaction product of the iron(III) phosphate reaction device to solid-liquid separation to obtain the solid phase component as an iron(III) phosphate product containing water of crystallization.

[0069] The denitration device is connected to an acid decomposition reaction device, and the nitric acid generated by the evaporative denitration is supplied to the acid decomposition tank for acid decomposition. In addition, the system The system further includes a calcination device for calcining the solid phase component separated in the fourth solid-liquid separation device to obtain an anhydrous iron(III) phosphate product.

[0070] In some embodiments, the extractor comprises one of a rotary extraction column, a multi-stage centrifugal extraction column, a vibrating sieve plate column, or a sieve plate extraction column.

[0071] In some embodiments, the first solid-liquid separation device, the second solid-liquid separation device, and the third solid-liquid separation device are independent separation devices or devices, or in some embodiments, the first solid-liquid separation device, the second solid-liquid separation device, and the third solid-liquid separation device may share a separation device or device, and the separation process of the first solid-liquid separation device, the second solid-liquid separation device, and the third solid-liquid separation device may be performed separately in different steps. In some specific embodiments, the first solid-liquid separation device, the second solid-liquid separation device, and the third solid-liquid separation device include a settler, a filter press, a filter extractor, etc.

[0072] The above system of the present invention partially utilizes and improves the existing nitrate phosphate fertilizer system to produce high purity ferric phosphate, and the by-products during the production process can be directly used in fertilizer preparation or used as independent products, with no waste.

[0073] According to another embodiment of the present invention, a method for co-producing ferric phosphate includes the steps of: S10, acid decomposing the phosphate rock raw material with nitric acid or a mixed acid containing nitric acid, and separating and removing the acid insoluble matter and acid solution; S20, freezing the acid solution to crystallize calcium nitrate, and filtering out the crystalline calcium nitrate to obtain a first solution; S30, adding a solution containing sulfate to the first solution to further remove calcium to obtain a second solution; S40, concentrating the second solution and volatilizing excess nitric acid from the second solution to obtain a concentrated denitrified third solution; S50, adding ammonia, such as gaseous ammonia, liquid ammonia or aqueous ammonia, to the third solution obtained in step S40 to carry out a neutralization reaction, and filtering to obtain a solution of ammonium phosphate salt; S60, adding an iron source to the ammonium phosphate salt solution obtained in step S50 to react with it, and then performing solid-liquid separation to obtain a ferric phosphate product.

[0074] In step S60, an iron source, for example at least one of ferric sulfate, ferrous sulfate, ferric nitrate, ferrous nitrate, ferric chloride, or monomeric iron such as iron powder, is reacted with the ammonium phosphate salt solution obtained in step S50 to obtain ferric phosphate.

[0075] Similarly, during the reaction in step S60, the pH of the reaction system is preferably controlled in the range of 4-6.

[0076] In a preferred embodiment, in step S50, ammonia is added to carry out a neutralization reaction to obtain the desired target product ammonium phosphate salt; during the neutralization reaction, the pH of the system gradually increases, and some metal ions, such as calcium, magnesium, manganese, etc., form solid phase precipitates, which is favorable for reducing and eliminating impurities in the ammonium phosphate salt product; and the impurities are filtered out and concentrated to obtain high-purity ammonium phosphate salt.

[0077] Furthermore, in a more preferred embodiment, the solid phase components filtered and separated in step S50 are mainly phosphates containing calcium, magnesium, and manganese, which are further prepared into nitrate phosphate fertilizer as elements of nitrate phosphate fertilizer.

[0078] Furthermore, in a more preferred embodiment, in step S50, ammonia gas is passed through the third solution to carry out a neutralization reaction until the pH of the system becomes 6 or more. Preferably, when the pH of the system becomes 6 or more, impurity metal ions in the system, such as calcium, magnesium, manganese, etc., are precipitated as phosphates, which is advantageous for reducing impurities and improving the purity of ammonium phosphate salts.

[0079] Furthermore, in some embodiments, in step S50, ammonia is added to the third solution to neutralize the pH of the reaction system, and the proportions or amounts of ammonium dihydrogen phosphate, ammonium monohydrogen phosphate, and ammonium trihydrogen phosphate are different in the prepared ammonium phosphate salt product as needed, and the pH of the neutralization reaction system can be adjusted between 4 and 7, and the proportions of ammonium dihydrogen phosphate, ammonium monohydrogen phosphate, and ammonium trihydrogen phosphate in the prepared product can be adjusted by adjusting the pH of the neutralization reaction system to the above range.

[0080] Another embodiment of the present invention further provides a system for co-producing ferric phosphate, as shown in FIG. an acid decomposition reactor for decomposing the phosphate rock raw material with nitric acid or a mixed acid; a first solid-liquid separation device for performing solid-liquid separation of the acid decomposition slurry after the acid decomposition to obtain an acid solution; a refrigeration and crystallization device for freezing and crystallizing the acid solution; a second solid-liquid separator for performing solid-liquid separation of the acid solution from the refrigeration and crystallization apparatus to obtain a first solution and a solid phase calcium nitrate crystal hydrate; a descaling reactor for reacting the first solution with a sulfate-containing solution, such as sulfuric acid or ammonium sulfate; a third solid-liquid separator for subjecting the product of the decalcification reaction to solid-liquid separation to obtain a second solution and calcium sulfate in a solid phase; a denitration device for concentrating and denitrating the second solution to obtain a concentrated and denitrated third solution and nitric acid; a neutralization device for neutralizing the third solution with ammonia; a fourth solid-liquid separator for filtering and separating the system after the neutralization reaction, and converting the liquid phase into an ammonium phosphate salt solution; a ferric phosphate reactor for reacting the ammonium phosphate salt solution with an iron source to produce ferric phosphate; and a fifth solid-liquid separation device for performing solid-liquid separation of the reaction product from the iron(III) phosphate reaction device to obtain a solid phase component, i.e., an iron(III) phosphate product containing water of crystallization. The denitrification equipment is connected to an acid decomposition reactor, and the nitric acid produced by the evaporative denitrification is supplied to the acid decomposition tank for acid decomposition.

[0081] In some embodiments, the first solid-liquid separation device, the second solid-liquid separation device, the third solid-liquid separation device, the fourth solid-liquid separation device, and the fifth solid-liquid separation device are independent separation devices or devices, or in some embodiments, the first solid-liquid separation device, the second solid-liquid separation device, the third solid-liquid separation device, the fourth solid-liquid separation device, and the fifth solid-liquid separation device may share a separation device or device, and in different steps, the first solid-liquid separation device, the second solid-liquid separation device, the third solid-liquid separation device, the fourth solid-liquid separation device, and the fifth solid-liquid separation device are performed separately. In some specific embodiments, the first solid-liquid separation device, the second solid-liquid separation device, the third solid-liquid separation device, the fourth solid-liquid separation device, and the fifth solid-liquid separation device may include a settling tank, a filter press, a filter extractor, etc.

[0082] In a preferred embodiment, the denitration apparatus includes a receiving chamber for receiving or holding the second solution, and a heater for heating and evaporating the second solution.

[0083] In a more preferred embodiment, the heater is a resistive heater and is configured, when operated, to heat the second solution to between 120 and 180° C. to vaporize it.

[0084] Furthermore, the above system The system further includes a calcination device for calcining the solid phase component separated by the fifth solid-liquid separation device to obtain an anhydrous iron(III) phosphate product.

[0085] To illustrate the preparation efficiency of the ferric phosphate product of the present invention, the following Example 1 illustrates the material usage and yield of the preparation process of a specific embodiment, S10: A phosphate concentrate containing 2 t of 34% P2O5 (calcium impurity: about 40.58%, magnesium impurity: about 0.77%, other impurities such as iron, aluminum, silicon, and fluorine: about 1-5% in total) is decomposed with 2.4 t (0.53 tN) of converted nitric acid, the acid decomposition slurry is separated into solid and liquid, 0.09 t of acid insoluble matter (silica-calcium-magnesium raw material) and an acid solution are obtained, the acid insoluble matter is washed with water 2-3 times, and the washing liquid is mixed with the acid solution; S20, freezing the acid solution to a temperature of -10°C to -5°C to crystallize, and vacuum filtering and separating the frozen solution at -2 to 1°C to obtain 3.54t of 60% crude calcium nitrate crystals and 2.186t of the first solution (0.635tP2O5); S30, adding 0.349t of sulfuric acid to the first solution and thoroughly separating the solid and liquid to obtain 0.51t of calcium sulfate hemihydrate and 2.055t of a second solution (0.635t of P2O5); S40, evaporating and concentrating the second solution at 80-85 ° C. and denitrifying it, stopping the reaction until the nitrate ion in the system is less than 0.01%, and recovering it to obtain 0.473t of converted nitric acid and a third solution; S50, the third solution is subjected to multi-stage cross-flow extraction in an extraction tower with one volume of an organic extraction solvent (a 1:1 volume mixture of n-butanol and isoamyl alcohol), the extraction phase is washed with water, and finally back-extracted with pure water, and after back-extraction, separated to obtain a phosphoric acid solution; S60, iron source preparation: dissolving 2.3t of purchased 85% ferrous sulfate heptahydrate in pure water, filtering and removing impurities, and then adding 0.93t of 25% ammonia water to the solution to neutralize it, and filtering and removing impurities again to obtain an iron salt solution; The iron salt solution is reacted with the phosphoric acid solution separated by stripping in step S50, and the pH of the reaction system is controlled to 4-6. After the reaction is complete and sufficient precipitation is achieved, the solid-liquid separation is performed by press filtration, and the ammonium sulfate product is obtained by filtration, concentration, and crystallization to obtain 0.66t. The solid-phase filter cake obtained by solid-liquid separation contains 1.24t of ferric phosphate (containing 0.48t of P2O5) as water of crystallization. Further, the water of crystallization of the ferric phosphate is dried to remove the water of crystallization to obtain 1 t of anhydrous ferric phosphate, and the P2O5 content in the anhydrous ferric phosphate is 48% (about 0.48 tP2O5). S70, concentrating the liquid phase component obtained by the solid-liquid separation in step S60 to prepare a nitrate phosphate fertilizer.

[0086] The following Example 2 describes the material usage and yield of the preparation process in a specific embodiment, specifically: S10: Acid decomposing 2t of phosphate concentrate containing 34% P2O5 with 2.4t (0.53tN) of converted nitric acid, separating the acid decomposition slurry into solid and liquid to obtain 0.09t of acid insoluble matter (containing silica-calcium-magnesium raw material) and acid solution, washing the acid insoluble matter with water 2-3 times, and combining the washing liquid with the acid solution; S20, freezing the acid solution to a temperature of -10°C to -5°C to crystallize, and vacuum filtering and separating the cooled solution at -2 to 1°C to obtain 3.54t of 60% crude calcium nitrate crystals, and 2.186t of a first solution (0.635tP2O5); S30, adding 0.349t of sulfuric acid to the first solution and thoroughly separating the solid and liquid to obtain 0.51t of calcium sulfate hemihydrate and 2.055t of a second solution (0.635t of P2O5); S40, concentrating and denitrifying the second solution to recover 0.473t of converted nitric acid and a third solution; S50, gradually add 0.19t of ammonia to the third solution to carry out neutralization reaction, and when the pH of the neutralization reaction system reaches 7.0, wait for complete precipitation, separate and purify, and the liquid phase component is an ammonium phosphate salt solution; S60, iron source preparation: 2.3t of purchased 85% ferrous sulfate heptahydrate was dissolved in pure water, impurities were removed by filtration, and then 0.93t of 25% ammonia water was added to the solution to neutralize it, and impurities were removed by filtration again to obtain an iron salt solution. Step S50 includes gradually adding the iron salt solution to the ammonium phosphate salt solution, controlling the pH of the reaction system to 4-6, and performing solid-liquid separation by press filtration after complete reaction and sufficient precipitation. The filtrate is concentrated and crystallized to obtain 0.66t of ammonium sulfate product. The solid-phase filter cake obtained by solid-liquid separation has 1.24t of ferric phosphate water of crystallization (containing 0.48t of P2O5), and after removing the water of crystallization by calcination, anhydrous ferric phosphate ferric phosphate product of 1t (containing 48% P2O5) is obtained.

[0087] Although the above examples and specific embodiments have been described in detail, the scope of protection of the present invention is not limited thereto, and any equivalent structure or equivalent flow modifications made based on the disclosure of the specification of the present invention, or any direct or indirect application in other related technical fields, should all be included in the scope of protection of the present invention.

Claims

1. acid digestion of phosphate rock or phosphate concentrate with nitric acid and separation of acid insoluble matter to obtain an acid solution; freezing and crystallizing the acid solution and performing solid-liquid separation to obtain a first solution; adding the first solution to a solution containing sulfate to react with the sulfate, and performing solid-liquid separation to obtain a second solution A; treating the second solution A to remove nitrates to obtain a third solution A; adding ammonia to the third solution A to neutralize it, subjecting the neutralized solution to solid separation to obtain an ammonium phosphate salt solution, and adding an iron source to the ammonium phosphate salt solution to react with it to prepare ferric phosphate; 1. A method for co-producing ferric phosphate with a nitrate phosphate fertilizer system, comprising:

2. 2. The method for co-producing ferric phosphate by a nitrate phosphate fertilizer system as recited in claim 1, wherein the iron source comprises at least one of an iron salt, a ferrous salt, or an iron monomer, and the sulfate-containing solution is at least one of a sulfuric acid solution, an ammonium sulfate solution.

3. The method for co-producing ferric phosphate by nitrate phosphate fertilizer equipment according to claim 1, characterized in that in the reaction of the iron source with the ammonium phosphate salt solution, the pH value of the reaction system is controlled to be 4-6.

4. 2. The method for co-producing ferric phosphate by a nitrate phosphate fertilizer apparatus according to claim 1, wherein the concentration of nitrate in the third solution A is less than 0.1%, more preferably, the concentration of nitrate in the third solution A is less than 0.05%, more preferably, the concentration of nitrate in the third solution A is less than 0.01%.

5. 2. The method for co-producing ferric phosphate with a nitrate phosphate fertilizer system as recited in claim 1, wherein the ammonia comprises at least one of ammonia gas, liquid ammonia, or aqueous ammonia.

6. acid digestion of phosphate rock or phosphate concentrate with nitric acid and separation of acid insoluble matter to obtain an acid solution; freezing and crystallizing the acid solution and performing solid-liquid separation to obtain a first solution; adding the first solution to sulfuric acid to react with the sulfuric acid, and performing solid-liquid separation to obtain a second solution B; treating the second solution B to remove nitrates to obtain a third solution B; pre-treating and extracting the third solution B with an extraction solvent to obtain an extract phase, post-treating and stripping the extract phase to obtain a phosphoric acid solution, and reacting an iron source with the phosphoric acid solution to obtain ferric phosphate.

7. 7. The method for co-producing ferric phosphate with a nitrate phosphate fertilizer system as recited in claim 6, wherein the iron source comprises at least one of an iron salt, a ferrous salt, or an iron monomer.

8. The method for co-producing ferric phosphate by nitrate phosphate fertilizer equipment according to claim 6, characterized in that in the reaction of the iron source with the phosphoric acid solution, the pH value of the reaction system is controlled to be 4-6.

9. 7. The method for co-producing ferric phosphate by a nitrate phosphate fertilizer device as claimed in claim 6, characterized in that the concentration of nitrate in the third solution B is less than 0.1%, more preferably, the concentration of nitrate in the third solution B is less than 0.05%, more preferably, the concentration of nitrate in the third solution B is less than 0.01%.

10. 7. The method for co-producing ferric phosphate by nitrate phosphate fertilizer apparatus according to claim 6, characterized in that in the extraction of the third solution B by the extraction solvent, the volume ratio of the extraction solvent to the third solution B is 0.5-5:

1.

11. 13. A ferric phosphate product prepared by the process for co-producing ferric phosphate with a nitrate phosphate fertilizer system as claimed in claim 1 or 6.

12. an acid decomposition reaction device for decomposing and reacting phosphate rock with nitric acid; a first solid-liquid separation device for performing solid-liquid separation of the acid decomposition slurry after the acid decomposition to obtain an acid solution; a freezing and crystallization device for freezing and crystallizing the acid solution; a second solid-liquid separation device for performing solid-liquid separation of the frozen and crystallized acid solution to obtain a first solution; a descaling reactor for reacting the first solution with a sulfate-containing solution; a third solid-liquid separator for performing solid-liquid separation of the product of the descaling reaction apparatus to obtain a second solution; a denitration device for evaporating the second solution to remove nitrates and 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 working up the extract phase and stripping it to obtain phosphoric acid; a ferric phosphate reactor for reacting an iron source with the phosphoric acid or ammonium phosphate salt solution to prepare ferric phosphate; and / or a neutralization device for neutralizing the third solution with ammonia to obtain a neutralized reaction solution, and a fourth solid-liquid separation device for performing solid-liquid separation of the neutralized reaction solution to obtain an ammonium phosphate salt solution.

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