A wet-process phosphoric acid production process for comprehensive utilization of phosphate rock full-element resources

Abstract

The application discloses a wet-process phosphoric acid production process for comprehensive utilization of full-element resources of phosphate rock, and belongs to the field of phosphorus chemical production. The process comprises the following steps: decomposing phosphate rock, a decomposing solution and a bottom solution to obtain a primary decomposing solution and primary decomposing residue; crystallizing the primary decomposing solution to obtain ammonium biphosphate crystals and a crystallization mother liquor of the ammonium biphosphate crystals; directly selling the ammonium biphosphate as a product or transforming the ammonium biphosphate to produce high-quality phosphoric acid, and returning the obtained crystallization mother liquor to preparation of the decomposing solution or the decomposing bottom solution; transforming the primary decomposing residue through ammonium carbonate to obtain an ammonium sulfate solution and a calcium carbonate filter cake; returning the ammonium sulfate solution to preparation of the decomposing solution or comprehensive utilization; transforming the calcium carbonate filter cake through ammonium chloride to obtain a mixed gas containing CO2 and NH3, a calcium chloride solution and an insoluble residue; and further producing calcium-containing compounds from the calcium chloride solution. The process provided by the application can absorb phosphate gypsum from the source, has low sulfuric acid consumption, high fluorine leaching rate, high comprehensive utilization rate of calcium resources, and good quality of the phosphoric acid obtained through transformation.

Description

TECHNICAL FIELD

[0001] The present application relates to a phosphorite full-element resource comprehensive utilization wet-process phosphoric acid production process, belonging to the field of phosphorus chemical production. BACKGROUND

[0002] Wet-process phosphoric acid, in a broad sense, refers to phosphoric acid produced by decomposing phosphorite with inorganic acids such as nitric acid, hydrochloric acid, sulfuric acid, and fluosilicic acid. The process of decomposing phosphorite with sulfuric acid is different from the process of decomposing phosphorite with other inorganic acids, and its significant feature is that the product after decomposition is not only phosphoric acid solution, but also calcium sulfate precipitate, which can be separated by simple filtration. The industrial application of wet-process phosphoric acid prepared by the sulfuric acid method has a history of more than 100 years, and has become a complete and modern production system. At present, the vast majority of wet-process phosphoric acid is prepared by the sulfuric acid method. Therefore, in a narrow sense, the wet-process phosphoric acid commonly referred to is the phosphoric acid prepared by decomposing phosphorite with sulfuric acid.

[0003] The wet-process phosphoric acid process of decomposing phosphorite with sulfuric acid is divided into different processes according to the hydration form of calcium sulfate crystals, including a dihydrate process, an anhydrous process, a hemihydrate process, a dihydrate-hemihydrate recrystallization process, and a hemihydrate-dihydrate recrystallization process.

[0004] The dihydrate process controls the precipitation of calcium in the form of dihydrate (gypsum) CaSO4•2H2O during the decomposition of phosphorite. The dihydrate process has the advantages of good stability of calcium sulfate dihydrate, uniform and coarse crystal particles, easy filtration and washing, and the disadvantage of low concentration of the produced phosphoric acid, with a P2O5 concentration of 31%, and a low phosphorus conversion rate, usually only 97.5%.

[0005] The anhydrous process controls the precipitation of calcium in the form of anhydrous substance (CaSO4) during the decomposition of phosphorite. The anhydrous process has the advantage of high concentration of the obtained finished phosphoric acid, with a P2O5 concentration of 50-55%, and the disadvantage of serious passivation of the phosphorite surface, low phosphorus recovery rate, usually only 93%, fine crystal particles of anhydrous substance, difficult filtration and washing, and difficulty in industrialization.

[0006] The hemihydrate process controls the precipitation of calcium in the form of hemihydrate (CaSO4•1 / 2H2O) during the decomposition of phosphorite. The hemihydrate process has the advantages of a concentration of the obtained phosphoric acid of 40-45% P2O5, formation of coarse precipitation particles, and good filtration performance in concentrated phosphoric acid medium, and the disadvantage of easy passivation of the phosphorite surface during the decomposition process, low phosphorus conversion rate, usually 92-95%.

[0007] The di-hemihydrate recrystallization process is to ensure the precipitation of calcium in the form of dihydrate (CaSO4•2H2O) by controlling the temperature of the decomposition of phosphate rock by sulfuric acid and reducing the concentration of phosphoric acid in the solution, and then heating and concentrating the reaction slurry to convert the precipitate into hemihydrate, thereby improving the recovery rate of phosphorus and the purity of the byproduct phosphogypsum. The advantages of this process are that the recovery rate of phosphorus is improved, and the disadvantages are: (1) the concentration of the obtained product phosphoric acid is still too low for the production of phosphorus chemical products; (2) the heat distribution of the process is unreasonable, a large amount of reaction heat needs to be removed in order to maintain the formation of dihydrate at a relatively low temperature, and the recrystallization process needs to be heated to increase the temperature of the slurry, suffering from the "cold and hot disease" of the process; (3) the hemihydrate crystallization of calcium sulfate is a metastable solid phase, and the treatment of hemihydrate filter residue is difficult, and practical operation process often encounters difficulties; (4) the generation of anhydrous material in the recrystallization process is difficult to prevent, and once "overdrying" occurs, the filterability of the filter residue will be poor.

[0008] The hemihydrate-dihydrate recrystallization process is further divided into dilute acid process and concentrated acid process. The dilute acid process refers to the formation of calcium sulfate hemihydrate crystals in dilute phosphoric acid, which is then directly converted into dihydrate without filtration, and then filtered and washed. The process only arranges one filtration, so it is called one-step process. The advantages of one-step process are that only one filtration is arranged, the process is simple, and there is no requirement for the size of hemihydrate crystal particles, and the phosphorus recovery rate of the process can reach 98%, and the disadvantages are that the process requires the concentration of phosphoric acid in the slurry to be at most 30-32% P2O5, the concentration of the obtained finished product phosphoric acid is still low, and strong heat exchange must be carried out for recrystallization to maintain the temperature of the slurry at 50-60℃. The concentrated acid process refers to the formation of calcium sulfate hemihydrate crystals in concentrated phosphoric acid, which is then filtered and washed, and then absorbs water to convert into dihydrate slurry, and finally filtered and washed. Since the process arranges two filtrations, it is called two-step process. The advantages of two-step process are: (1) the concentration of the obtained finished product phosphoric acid is high, generally 40-45% P2O5, which can be directly used as raw material for most phosphate fertilizer production; (2) the conversion rate of P2O5 is high, generally more than 98%, which is the process widely used by wet-process sulfuric acid at present, but the disadvantages are that two filtrations are required, the process flow is relatively long, the operation is complicated, and the total process time is also relatively long, generally 4-5 hours, and the production efficiency is low.

[0009] A common feature of the above-mentioned wet-process phosphoric acid production processes is that only a small part of the decomposed slurry of the phosphate rock is used for filtering to produce phosphoric acid, and the remaining large part is used as back slurry to control the crystallization state of gypsum. The waste residue obtained by filtering contains, in addition to calcium sulfate (more than 90%), a small amount of undecomposed phosphate rock, fluorosilicate precipitate, undetached phosphoric acid and fluorosilicic acid, possible phosphate precipitate and insoluble impurities brought in with the phosphate rock, etc., which are collectively referred to as phosphogypsum. Nearly half of the fluorine in the phosphate rock in the wet-process phosphoric acid production process remains in the phosphogypsum, and the waste of fluorine resources is astonishing. The production of phosphogypsum in the phosphate chemical industry is huge, and 4-4.5 tons of phosphogypsum are produced for every ton of P2O5 produced by using the dihydrate process. The leachate of phosphogypsum is acidic due to the presence of soluble phosphorus and fluorine, which is harmful to the ecological environment. The root cause of the generation of phosphogypsum is that the calcium element is not comprehensively utilized in the decomposition process of the phosphate rock. SUMMARY

[0010] In view of the problems existing in the prior art, the purpose of the present application is to provide a wet-process phosphoric acid production process for comprehensive utilization of full-element resources of phosphate rock. The process provided by the present application can absorb phosphogypsum from the source, has high production efficiency, low sulfuric acid consumption, high fluorine leaching rate, high comprehensive utilization rate of calcium resources, low production cost, good product quality, simple operation, and produces phosphoric acid with high concentration and good quality.

[0011] In order to achieve the above-mentioned purpose, the first aspect of the present application is to provide a wet-process phosphoric acid production process for comprehensive utilization of full-element resources of phosphate rock, which comprises:

[0012] (1) decomposing phosphate rock, a decomposing solution and a bottom solution at a temperature of 60-120°C for 0.25-2.5h, adjusting the mass concentration of P2O5 in the slurry to 30-50%, adjusting the pH value to 2.6-4.6 by using an alkaline substance, filtering and washing while hot, to obtain a primary decomposing solution and a primary decomposing residue; the decomposing solution is a solution containing ammonium bisulfate, and the bottom solution is water or a solution containing phosphoric acid;

[0013] (2) crystallizing the primary decomposing solution to obtain ammonium dihydrogen phosphate crystals and a crystallization mother liquor; the crystallization mother liquor is returned to be used for preparing the decomposing solution or the decomposing bottom solution;

[0014] using the ammonium dihydrogen phosphate crystals as a raw material for the production of phosphoric acid and phosphate or directly selling them as products;

[0015] (3) mixing the primary decomposing residue after slurry adjustment with an ammonium carbonate salt, adjusting the pH value of the slurry to alkaline by using ammonia or aqueous ammonia, and placing it in a mixed atmosphere of CO2 and NH3 for carbon-ammonia transformation, and then filtering and separating to obtain an ammonium sulfate solution and a calcium carbonate filter cake;

[0016] The ammonium sulfate solution is returned to be used for preparing the decomposing solution or for comprehensive utilization.

[0017] The calcium carbonate filter cake is placed in a solution containing calcium chloride to perform ammonium chloride transformation, filtration, to obtain a mixed gas containing CO2 and NH3, and a calcium chloride solution and insoluble residue;

[0018] Alternatively, the calcium carbonate filter cake is mixed with ammonium chloride and calcined to perform ammonium chloride transformation, to obtain a mixed gas containing CO2 and NH3 and CaCl2 calcine, the calcine is dissolved in water and filtered to obtain a calcium chloride solution and insoluble residue;

[0019] The mixed gas containing CO2 and NH3 is returned to be used in the ammonium carbonate transformation and / or production of calcium-containing compounds;

[0020] The calcium chloride solution is used as a bottom solution for production of calcium-containing compounds and / or ammonium chloride transformation;

[0021] (4) The insoluble residue is subjected to secondary decomposition with the decomposing solution to extract residual phosphorus.

[0022] The application innovatively uses a solution containing ammonium bisulfate as a decomposing solution to decompose phosphate rock. Although the decomposition of phosphate rock by ammonium bisulfate solution is also an exothermic reaction, compared with the decomposition of phosphate rock by sulfuric acid, the heat released is much smaller, and the cooling burden of the decomposition process is much lighter. The heat generated by the reaction is consumed by equipment heat dissipation, water evaporation heat absorption and physical heat carried away by the material. Further, the decomposition of phosphate rock in ammonium bisulfate is very fast, and there is no need to worry about the conversion rate of P2O5 in the decomposition process of phosphate rock and the generation of phosphate rock passivation phenomenon, and the generated precipitate is easy to filter, and does not block during the filtration and washing process. Further, the generated precipitate of the application has no special requirement for the crystalline state, and does not need to be specifically selected. The precipitate can be any one or several of dihydrate gypsum, hemihydrate gypsum and anhydrous gypsum.

[0023] Further, the decomposition of phosphate rock can be carried out at a temperature of 60-120℃, and the decomposition time only needs to be 0.25-2.5h, which greatly improves the operation efficiency of phosphate rock decomposition. Because the time required for phosphate rock decomposition is short, and the back slurry amount in the decomposition process is small, the power consumption required for stirring and slurry transportation in the phosphate rock decomposition process is small, and at the same time, the filtration burden of the decomposition slurry is also reduced. In addition, the phosphorus and fluorine in the primary decomposition residue of phosphate rock are mainly enriched in the insoluble residue after ammonium carbonate and ammonium chloride transformation, and the insoluble residue is collected and returned to be subjected to secondary decomposition with the solution containing ammonium bisulfate to recover phosphorus and fluorine.

[0024] Further, the primary decomposition solution can be cooled to selectively crystallize ammonium dihydrogen phosphate in the solution, so as to effectively separate phosphorus and impurities, and the obtained ammonium dihydrogen phosphate crystals can be further recrystallized to further improve the purity of the ammonium dihydrogen phosphate. The ammonium dihydrogen phosphate obtained by crystallization can be converted to produce phosphoric acid, and high-quality phosphoric acid products can be obtained. Compared with the traditional wet-process phosphoric acid production process, the production process is simple, the product quality is good, and the production cost is low.

[0025] The basic principle of the wet-process phosphoric acid production process for full-element resourceization and comprehensive utilization of phosphate rock is as follows:

[0026] (NH4)2SO4 + H2SO4 = 2NH4HSO4 (1)

[0027] Ca5F(PO4)3 + 6NH4HSO4 + 5xH2O =Δ= 3NH4H2PO4 + 5CaSO4•xH2O↓ +

[0028] NH4F + (NH4)2SO4,x = 0~2 (2)

[0029] 4NH4HSO4 + SiO2 + 6NH4F = (NH4)2SiF6 + 4(NH4)2SO4 + 2H2O (3)

[0030] NH4H2PO4 + HCl = H3PO4 + NH4Cl↓ (4)

[0031] 2NH4H2PO4 + NO + NO2 = H3PO4 + N2↑ + 2H2O (5)

[0032] CaSO4•xH2O + 2NH3 + CO2 = (NH4)2SO4 + CaCO3↓ + (x-1)H2O (6)

[0033] CaCO3 + 2NH4Cl =Δ= CaCl2 + H2O + CO2↑ + 2NH3↑ (7)

[0034] CaCl2 + CO2 + 2NH3 + H2O = CaCO3↓ + 2NH4Cl (8)

[0035] CaCl2 + (NH4)2SO4 + nH2O = CaSO4•nH2O↓ + 2NH4Cl, n = 0~2 (9)

[0036] (NH4)2SiF6 + Na2SO4 = (NH4)2SO4 + Na2SiF6↓ (10)

[0037] The ammonium sulfate solution obtained by ammonium carbonate transformation of the primary decomposition residue is used to replace sulfuric acid to decompose the phosphate ore, which not only can effectively inhibit the dissolution of impurities in the decomposition process, but also can make the sulfate radical be used twice in the decomposition process of the phosphate ore, and the amount of sulfuric acid is significantly reduced. The ammonium bisulfate is added in an amount of 1-1.5 times of the stoichiometric amount to decompose the phosphate ore, and the P2O5 primary leaching rate can reach 85-93% after heating and stirring for 0.5 h. The calcium carbonate filter cake obtained by ammonium carbonate transformation of the primary decomposition residue is subjected to ammonium chloride transformation again, and the obtained insoluble filter residue is leached with a solution containing ammonium bisulfate, so that the decomposition rate of phosphorus is maximized, the leaching rate of phosphorus in the decomposition process of the phosphate ore is ≥99%, the leaching rate of fluorine is ≥97%, the comprehensive utilization rate of calcium resources in the whole process is ≥95%, and compared with the traditional process, the theoretical amount of sulfuric acid is saved by 40%. The amount of sulfuric acid required for the decomposition of the phosphate ore is reduced, and the cooling load of the reaction slurry in the decomposition process of the phosphate ore is significantly reduced.

[0038] It should be noted that the type of phosphate ore and the composition and content of the substances in the phosphate ore have no special requirements, and known methods in the art can be used.

[0039] As a preferred scheme, step (2) further comprises purifying and removing impurities, and the primary decomposition solution is purified and impurities are removed before crystallization, or the mother liquor obtained after crystallization is purified and impurities are removed.

[0040] As a preferred scheme, the method for purifying and removing impurities is that the mother liquor obtained after crystallization or the primary decomposition solution is mixed with an alkali metal sulfate and stirred for 45 min-80 min, the molar ratio of the alkali metal element in the alkali metal sulfate to the fluorine element in the mother liquor obtained after crystallization or the primary decomposition solution is 1:2.5-4, so that the fluorine is crystallized and separated in the form of fluorosilicate.

[0041] As a more preferred scheme, the step of purifying and removing impurities is that the mother liquor or the primary decomposition solution is first mixed with an alkali metal sulfate and stirred for 45 min-80 min, so that the fluorine in the mother liquor or the primary decomposition solution is crystallized and separated in the form of fluorosilicate, then the pH value of the liquid obtained after crystallization is adjusted to 6-9, residual impurities are precipitated again, the mother liquor is obtained by filtration, and the purified mother liquor is returned to be used for preparing the decomposition solution or the decomposition bottom solution.

[0042] As a preferred solution, in step (3), the specific steps of the ammonium carbonate transformation include: mixing the primary decomposition residue with ammonium carbonate salt after slurry preparation, adjusting the pH of the slurry to 8-9 with ammonia or aqueous ammonia, and reacting for 0.5-2.5 h under a mixed atmosphere of CO2 and NH3 to perform ammonium carbonate transformation, and then filtering and separating to obtain an ammonium sulfate solution and a calcium carbonate filter cake; the molar ratio of Ca element in the primary decomposition residue to C element in the ammonium carbonate salt is 1:1-1.5.

[0043] As a preferred solution, the ammonium carbonate salt is ammonium bicarbonate.

[0044] As a preferred solution, the mass concentration of ammonium bisulfate in the decomposition solution is ≥20%.

[0045] As a preferred solution, the decomposition solution is prepared from the ammonium sulfate solution in step (3), the crystallization mother liquor in step (2), and sulfuric acid, or the decomposition solution is prepared from the ammonium sulfate solution in step (3) and sulfuric acid.

[0046] As a preferred solution, the molar ratio of ammonium sulfate to sulfuric acid in the ammonium sulfate solution is 1:0.8-1.2 on a dry basis.

[0047] As a preferred solution, in step (1), the molar ratio of Ca element in the phosphate rock to S element in the decomposition solution is 1:1-1.5.

[0048] As a preferred solution, the solid-liquid ratio of the phosphate rock to the bottom liquid is 1-5:1 g / mL.

[0049] As a preferred solution, the mass concentration of P2O5 in the phosphoric acid-containing solution is ≥10%, and the solid content is 0-20 wt%.

[0050] As a preferred solution, in step (2), the ammonium dihydrogen phosphate crystals are recrystallized and then used as raw materials for the production of phosphoric acid and phosphates or directly sold as products.

[0051] As a preferred solution, the phosphoric acid-containing solution is prepared from the washing water of the primary decomposition residue, the crystallization mother liquor, the primary decomposition slurry, or the primary decomposition solution.

[0052] As a preferred solution, the alkaline substance includes at least one of phosphate rock, calcium carbonate, diammonium phosphate, triammonium phosphate, ammonia, and aqueous ammonia.

[0053] As a preferred solution, the operation of crystallizing the primary decomposition solution includes: cooling the primary decomposition solution to 0-30℃ to selectively crystallize ammonium dihydrogen phosphate.

[0054] As a preferred solution, the method for producing phosphoric acid from ammonium dihydrogen phosphate crystals comprises: converting the ammonium dihydrogen phosphate into phosphoric acid by using at least one of hydrochloric acid, HCl gas, a mixed gas of NO / NO2 in an equimolar ratio, and nitrous acid as a transformation agent.

[0055] As a more preferred solution, when hydrochloric acid or HCl gas is used as the transformation agent, the method comprises: first dissolving the ammonium dihydrogen phosphate in hydrochloric acid or introducing HCl gas into the ammonium dihydrogen phosphate solution to convert the ammonium dihydrogen phosphate into phosphoric acid and ammonium chloride; then crystallizing the ammonium chloride by cooling; filtering the ammonium chloride crystals and a phosphoric acid-containing solution; and finally evaporating and concentrating the phosphoric acid-containing solution to volatilize excess HCl and obtain a phosphoric acid product. The present application ingeniously uses ammonium dihydrogen phosphate and its recrystallized product as the raw material for the production of wet-process phosphoric acid, greatly simplifying the production process of high-quality wet-process phosphoric acid. By using hydrochloric acid or HCl gas as the transformation agent, the principle of replacing a weak acid with a strong acid is used to first convert the ammonium dihydrogen phosphate into a phosphoric acid solution and ammonium chloride crystals, then evaporate and concentrate the obtained phosphoric acid solution to obtain a high-quality phosphoric acid product, and collect the obtained HCl gas to return it to the transformation process for recycling, thereby achieving the recycling of HCl in the phosphoric acid production process. The present application has the advantages of simple process, good product quality, low production cost, environmental friendliness, etc.

[0056] As a preferred solution, the molar ratio of the ammonium dihydrogen phosphate to HCl (on a dry basis) is 1:1 to 3.

[0057] As a preferred solution, the step of cooling to crystallize the ammonium chloride specifically comprises: first cooling the solution obtained after transformation to 10 to 30°C, and then cooling to -35 to 9°C to crystallize the ammonium chloride. - The ammonium chloride is crystallized under the action of the common ion effect of the ions, and the filtrate is subjected to deep crystallization to precipitate ammonium chloride at a temperature of -35 to 9°C.

[0058] As a more preferred solution, when a mixed gas of NO / NO2 in an equimolar ratio and / or nitrous acid is used as the transformation agent, the method comprises: introducing the mixed gas of NO / NO2 and / or nitrous acid into the ammonium dihydrogen phosphate solution to convert the ammonium dihydrogen phosphate into ammonium nitrite and phosphoric acid; heating the ammonium nitrite to gradually decompose and release nitrogen; and finally evaporating and concentrating the decomposed liquid to obtain a phosphoric acid product.

[0059] As a more preferred solution, the alkali metal sulfate is sodium sulfate and / or potassium sulfate.

[0060] As a preferred scheme, the ammonium chloride transformation operation specifically comprises: the calcium carbonate filter cake is placed in a solution containing calcium chloride, the calcium carbonate is rapidly decomposed at 105-175 DEG C for 1-3 hours, ammonium chloride transformation is carried out, CO2 and NH3 mixed gas, and calcium chloride solution and insoluble residue are obtained; the molar ratio of Ca element in the calcium carbonate filter cake to Cl element in the ammonium chloride is 1:2-3; the concentration of calcium chloride in the solution containing calcium chloride is greater than or equal to 20 wt.%. The solution containing calcium chloride is selected as the reaction bottom liquid, mainly based on the fact that the reaction of ammonium chloride in the aqueous solution decomposing calcium carbonate belongs to an endothermic reaction type, and the purpose of selecting the solution containing calcium chloride as the reaction bottom liquid is to utilize the characteristic that the boiling point of the CaCl2 solution increases with the increase of the concentration of the CaCl2 solution, when the concentration of the calcium chloride solution reaches 20%, the boiling point temperature of the CaCl2 solution can be increased to greater than or equal to 105 DEG C, which can meet the process temperature required for the rapid decomposition of ammonium chloride in the solution, and the product obtained by the reaction is also CaCl2, which is convenient for recycling and utilization.

[0061] The concentration of calcium chloride in the solution containing calcium chloride according to the application is further preferably 30 wt.% to 55 wt.%.

[0062] As a preferred scheme, the ammonium chloride transformation operation specifically comprises: the calcium carbonate filter cake is placed in a solution containing calcium chloride, the calcium carbonate is rapidly decomposed at 105-175 DEG C for 1-3 hours, ammonium chloride transformation is carried out, CO2 and NH3 mixed gas, and calcium chloride solution and insoluble residue are obtained; the molar ratio of Ca element in the calcium carbonate filter cake to Cl element in the ammonium chloride is 1:2-3; the concentration of calcium chloride in the solution containing calcium chloride is greater than or equal to 20 wt.%. The solution containing calcium chloride is selected as the reaction bottom liquid, mainly based on the fact that the reaction of ammonium chloride in the aqueous solution decomposing calcium carbonate belongs to an endothermic reaction type, and the purpose of selecting the solution containing calcium chloride as the reaction bottom liquid is to utilize the characteristic that the boiling point of the CaCl2 solution increases with the increase of the concentration of the CaCl2 solution, when the concentration of the calcium chloride solution reaches 20%, the boiling point temperature of the CaCl2 solution can be increased to greater than or equal to 105 DEG C, which can meet the process temperature required for the rapid decomposition of ammonium chloride in the solution, and the product obtained by the reaction is also CaCl2, which is convenient for recycling and utilization.

[0063] As a preferred scheme, the method for using the obtained calcium chloride solution for the production of calcium-containing compounds comprises: the CO2 and NH3 mixed gas is introduced into the calcium chloride solution to generate calcium carbonate.

[0064] As a preferred scheme, the method for using the obtained calcium chloride solution for the production of calcium-containing compounds comprises: the CO2 and NH3 mixed gas is introduced into the calcium chloride solution, the pH value is adjusted to 8-9, calcium carbonate is precipitated and separated out, and the precipitated calcium carbonate product is obtained by filtering, washing and drying.

[0065] As a preferred scheme, the washing water mentioned above and the filtrate obtained by filtering are combined, evaporated, concentrated, crystallized and recycled to recover ammonium chloride, and the ammonium chloride is recycled and utilized in the ammonium chloride transformation process.

[0066] As a preferred scheme, the method for using the obtained calcium chloride solution to produce a calcium-containing compound comprises: mixing the calcium chloride solution with a solution containing ammonium sulfate or ammonium sulfate crystals to produce calcium sulfate; and the molar ratio of Ca in the calcium chloride solution to S in the ammonium sulfate on a dry basis is 1:0.8-1.2.

[0067] As a preferred scheme, the method for using the obtained calcium chloride solution to produce a calcium-containing compound comprises: mixing the calcium chloride solution with sodium sulfate solid to produce calcium sulfate whiskers, and filtering to obtain calcium sulfate whiskers and a post-reaction liquid.

[0068] As a preferred scheme, the post-reaction liquid is mixed with a calcium chloride solution, the precipitated sodium chloride crystals are filtered, and the obtained filtrate is recycled to the calcium sulfate whisker production process.

[0069] As a preferred scheme, the comprehensive utilization comprises producing ammonium sulfate fertilizer and / or producing calcium sulfate using the ammonium sulfate solution.

[0070] Compared with the prior art, the present application has at least the following advantages:

[0071] (1) The ammonium sulfate solution obtained by converting the once-decomposed residue is used to prepare an ammonium bisulfate solution by mixing with sulfuric acid, and the ammonium bisulfate solution is used as a decomposition liquid for phosphorite decomposition, thereby significantly reducing the amount of sulfuric acid required for phosphorite decomposition; and ammonium dihydrogen phosphate in the once-decomposition liquid can be selectively crystallized and precipitated after cooling, and the crystallized ammonium dihydrogen phosphate is used to produce phosphoric acid, thereby obtaining high-quality phosphoric acid products, and compared with the traditional wet-process phosphoric acid production process, the present application has the advantages of simple production process, good product quality, low production cost, and strong market competitiveness.

[0072] (2) The once-decomposed residue after phosphorite decomposition is converted into ammonium carbonate and ammonium chloride, and the obtained calcium chloride solution is used to produce industrial precipitated calcium carbonate, precipitated calcium sulfate, and calcium sulfate whiskers, so that the calcium and sulfate in the solution are fully utilized, which not only allows the calcium in the phosphorite to be comprehensively utilized, but also greatly improves the comprehensive economic benefits of the wet-process phosphoric acid production process.

[0073] (3) The process provided by the present application can absorb phosphogypsum from the source, and can effectively utilize phosphorus, fluorine, and calcium with high utilization rate. DETAILED DESCRIPTION

[0074] The endpoints of the ranges and any values disclosed herein are not limited to the precise values recited as the exact dimensions are not critical to the properties. Any numerical range recited herein is intended to include all sub-ranges of the same numbers (i.e., every subset of numbers within the indicated range). For ranges containing one or more endpoints, the endpoints are included in the range. For ranges containing no endpoints, the range is intended to include all values and / or sub-ranges of the same numbers (i.e., every number falling within the range).

[0075] The application will be further described with reference to the following non-limiting examples. It is apparent that only some of the particular embodiments of the application are described and that numerous other embodiments falling within the scope of the application exist. It will be readily apparent to those skilled in the art that varying substitutions and modifications can be made to the application disclosed herein without departing from the scope and spirit of the application.

[0076] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The materials, methods, and examples provided herein are illustrative only and not intended to be limiting.

[0077] Example 1

[0078] 1000 g of phosphate rock powder with P2O5 content of 32.15 wt% and CaO content of 50.16 wt% was weighed, first added water according to solid-liquid ratio of 3:1 g / mL, and heated to increase the temperature to 65℃, then slowly added ammonium bisulfate solution with mass concentration of 40% according to Ca / S molar ratio of 1:1.2, after the addition of ammonium bisulfate solution, the temperature of the solution was increased to 85℃, and after constant temperature stirring for 0.5 h (at this time the mass concentration of P2O5 in the slurry was 41.9 wt%), the pH value of the slurry was adjusted to 4.2 by adding diammonium phosphate, and then filtered and washed while hot to obtain a primary decomposition liquid and a primary decomposition residue;

[0079] The primary decomposition liquid was cooled to room temperature, ammonium dihydrogen phosphate was crystallized and precipitated, and ammonium dihydrogen phosphate crystals and their crystallization mother liquor were obtained by filtration, and then the obtained ammonium dihydrogen phosphate crystals were recrystallized with saturated ammonium dihydrogen phosphate solution to obtain ammonium dihydrogen phosphate products meeting the quality requirements of I class of HG / T 4133-2021 industrial ammonium dihydrogen phosphate, and the crystallization mother liquor thereof was first added with potassium sulfate according to K / F molar ratio of 1:3 to crystallize potassium fluosilicate to remove fluorine, then ammonia water was added to adjust the pH value to 7, and other impurities were removed by filtration, and the obtained impurity-removed purified liquid was returned to be used for preparing decomposition liquid and decomposition bottom liquid;

[0080] The obtained primary decomposition residue is first slurried by adding water at a solid-liquid ratio of 1:1 g / mL, then CO2 and NH3 mixed gas is introduced into the slurry at a Ca / C molar ratio of 1:1.2, and the solution pH is adjusted to 8.5 with ammonia, and stirred at room temperature for 1 h, so that the calcium sulfate in it is converted into calcium carbonate, and the ammonium sulfate solution and calcium carbonate filter cake are obtained by filtration, and the obtained ammonium sulfate solution is divided into two parts, one part is returned to prepare the ammonium bisulfate solution, and the other part is used for comprehensive utilization, and the obtained calcium carbonate-containing filter cake is mixed with ammonium chloride at a Ca / Cl molar ratio of 1:2.1, and the mine is dried and then calcined at a temperature of 465°C for 1 h, to obtain a calcined sand containing CaCl2 and a flue gas containing CO2 and NH3, the flue gas is collected and used for ammonium carbonate transformation of the primary decomposition residue, and the calcined sand is dissolved by adding water, and calcium chloride solution and insoluble residue are obtained by filtration, and the insoluble residue is further decomposed with the ammonium bisulfate solution until the P content in it is reduced to <0.05%, and finally the obtained calcium chloride solution is divided into two parts, one part is mixed with the ammonium sulfate solution obtained by ammonium carbonate transformation at a Ca / S molar ratio of 1:1, and the precipitated calcium sulfate product is obtained by filtration, and the other part is used as the reaction bottom liquid for ammonium carbonate transformation of the calcium carbonate filter cake, the process has a phosphorus leaching rate of 99.4%, a fluorine leaching rate of 97.8%, and a calcium resource comprehensive utilization rate of 96.7%.

[0081] Example 2

[0082] 500g of phosphate rock powder with a P2O5 content of 30.62wt% and a CaO content of 49.05wt% is weighed, and is added into the ammonium dihydrogen phosphate crystallization mother liquor obtained in Example 1 to form a slurry at a solid-liquid ratio of 1:1 g / mL, and is stirred and heated, and 500g of ammonium sulfate solution obtained in Example 1 is slowly added at a Ca / S molar ratio of 1:1.2, and the ammonium bisulfate solution with a mass concentration of 47% preheated to 85°C is slowly added, and after the addition of the ammonium bisulfate solution is completed, the slurry is continuously stirred at 110°C for 0.25h (at this time, the P2O5 mass concentration in the slurry is 37.6wt%), then 110g of phosphate rock powder is added to coarsely adjust the pH of the slurry, and concentrated ammonia is added to adjust the pH of the slurry to 4.5, and the hot slurry is filtered and washed to obtain a primary decomposition liquid and a primary decomposition residue;

[0083] The obtained primary decomposition residue is first slurried with water at a solid-liquid ratio of 1:1 g / mL, then ammonium bicarbonate is added to the slurry at a Ca / C molar ratio of 1:1.2 to perform ammonium carbonate transformation, and the solution pH is adjusted to 8.2 with ammonia, and stirred at room temperature for 1 h to convert the calcium sulfate therein into calcium carbonate, and the ammonium sulfate solution and calcium carbonate filter cake are filtered, and the obtained ammonium sulfate solution is divided into two parts, one part is returned to prepare the decomposition solution, and the other part is evaporated and concentrated to crystallize agricultural ammonium sulfate fertilizer, the obtained calcium carbonate-containing filter cake is first mixed with ammonium chloride at a Ca / Cl molar ratio of 1:2.4, then slowly stirred and added to the solution containing calcium chloride obtained in Example 1 heated to 120°C (the concentration of calcium chloride is 43.7 wt.%), and reacted for 1.5 h to rapidly decompose and convert into a slurry containing calcium chloride and a mixed gas containing CO2 and NH3, the mixed gas is collected and returned to the ammonium carbonate transformation of the primary decomposition residue, and the slurry is filtered to obtain a calcium chloride solution and an insoluble residue, the insoluble residue is further decomposed with ammonium bisulfate solution until the P content therein is reduced to 0.03%, and the leaching rate of phosphorus reaches 99.6%, and the obtained calcium chloride solution is divided into two parts, one part is used as the reaction bottom liquid for ammonium chloride transformation of the calcium carbonate filter cake, and the other part is passed into the mixed gas of CO2 and NH3 to precipitate calcium at a pH of 8.6, and the precipitate is filtered, washed and dried to obtain industrial precipitated calcium carbonate, and the combined filtrate and wash water is evaporated and concentrated to crystallize and recover ammonium chloride, and the ammonium chloride crystals are returned to the ammonium chloride transformation process for recycling, and the overall process has a calcium resource utilization rate of 97.6%.

[0084] The primary decomposition solution is naturally cooled to crystallize ammonium dihydrogen phosphate, filtered to obtain ammonium dihydrogen phosphate crystals and their crystallization mother liquor, the crystallization mother liquor is then purified and impurities are removed, and the crystallization mother liquor is first added with potassium sulfate at a K / F molar ratio of 1:3 to crystallize potassium fluoro-silicate to remove fluorine, then ammonia water is added to adjust the pH to 7, and other impurities are removed by filtration, and the obtained purified solution is returned to prepare the decomposition solution and decomposition bottom liquid; and the obtained ammonium dihydrogen phosphate crystals are recrystallized with saturated ammonium dihydrogen phosphate solution, and the obtained ammonium dihydrogen phosphate solution is transformed to produce phosphoric acid. Hydrochloric acid is used as the transformation agent, and the recrystallized product is first added to 37% hydrochloric acid at a solid-liquid ratio of 1:1 g / mL (the molar ratio of ammonium dihydrogen phosphate to HCl on a dry basis is 1:1.4), stirred and heated to dissolve, naturally cooled, and then placed in an environment at -25°C to freeze crystallize for 16 h to force the ammonium chloride therein to deeply crystallize and precipitate, filtered, the filtrate is heated and evaporated, the volatilized HCl is collected and reused, and when the specific gravity of the solution rises to 1.54 g / mL, heating is stopped, and the solution is cooled to room temperature, and the sample is tested, and the quality meets the quality standards of food additives-phosphoric acid in the national food safety standard GB 1886.15-2015, and the process consumes 65.8% of the sulfuric acid of the traditional process, and the leaching rate of fluorine is 98.1%.

[0085] Example 3

[0086] Take 500g of phosphate rock powder with P2O5 content of 29.64wt% and CaO content of 48.73wt%, and add the purified and impurity-removed ammonium dihydrogen phosphate crystallization mother liquor obtained in Example 2 to form a slurry at a solid-liquid ratio of 1:1 g / mL, and stir and heat to raise the temperature to 98℃, and slowly add the ammonium bisulfate solution with a mass concentration of 36% prepared by mixing the ammonium sulfate solution obtained in Example 2 with sulfuric acid, preheated to 95℃, at a Ca / S molar ratio of 1:1.1, and after the ammonium bisulfate solution is added, continue to stir at a constant temperature of 115℃ for 0.5h (at this time, the mass concentration of P2O5 in the slurry is 41.8wt%), and adjust the pH of the slurry to 3.5 with calcium carbonate powder, and filter and wash while hot to obtain a primary decomposition liquid and a primary decomposition residue;

[0087] The obtained primary decomposition residue is first slurried with water at a solid-liquid ratio of 1:1 g / mL, then ammonium bicarbonate is added to the slurry at a Ca / C molar ratio of 1:1.2 to transform it, and the pH of the solution is adjusted to 8.5 with ammonia, and stirred at room temperature for 1h to convert the calcium sulfate in it into calcium carbonate, and filtered to obtain an ammonium sulfate solution and a calcium carbonate filter cake, and the obtained ammonium sulfate solution is added to the sodium bicarbonate transformation according to the stoichiometric amount, and concentrated by evaporation, and crystallized to obtain sodium sulfate solids, and the mixed gas of CO2 and NH3 generated during the evaporation and concentration process is collected and returned for use in the ammonium bicarbonate transformation of the primary decomposition residue. The obtained calcium carbonate-containing filter cake is first mixed with ammonium chloride at a Ca / Cl molar ratio of 1:2.3, and then slowly stirred and added to the calcium chloride-containing solution obtained in Example 2 heated to 130℃ (the concentration of calcium chloride is 51.6wt.%), and reacted for 1h to make it decompose rapidly and convert into a calcium chloride-containing slurry and a mixed gas containing CO2 and NH3, and the mixed gas is collected for use in the production of ammonium carbonate, and the slurry is filtered to obtain a calcium chloride solution and an insoluble residue, and the insoluble residue is further decomposed with ammonium bisulfate solution until the P content in it is reduced to 0.04%, the calcium dissolution rate is 98.1%, and the phosphorus leaching rate reaches 99.3%, and then sodium sulfate solids are slowly stirred and added to the obtained calcium chloride solution, and reacted at 45℃ for 8h, and filtered and washed to obtain a two-water gypsum whisker with a length-diameter ratio of 10~100 and a post-reaction liquid, and the obtained gypsum whisker is washed, dried at 400℃ for 2h to obtain anhydrous gypsum whisker products with a whiteness of >96%, and then a 45% concentration calcium chloride solution is added to the post-reaction liquid to force sodium chloride to crystallize and precipitate, and filtered to obtain sodium chloride crystals which are dissolved in water to form a saturated solution, and CO2 and NH3 mixed gas is bubbled into the saturated solution to make sodium bicarbonate crystallize and precipitate first, and then ammonium chloride is separated by cooling and crystallization, and the obtained sodium bicarbonate and ammonium chloride are both returned to the process for recycling.

[0088] The primary decomposition liquid is heated and kept warm, and sodium sulfate is slowly added into the liquid with stirring according to a Na / F molar ratio of 1:3. After the addition of sodium sulfate is completed, the stirring is continued for 1 h, and then the solution is filtered twice while hot to separate the crystallized sodium fluorosilicate. Then, the solution is allowed to cool naturally to crystallize ammonium dihydrogen phosphate, which is filtered to obtain ammonium dihydrogen phosphate crystals and a purified crystallization mother liquor. The purified crystallization mother liquor is returned to be used for preparing the decomposition liquid and the decomposition bottom liquid. The obtained ammonium dihydrogen phosphate crystals are recrystallized with the saturated ammonium dihydrogen phosphate solution used in Example 2, and the recrystallized product is converted into phosphoric acid by using an equimolar ratio of NO / NO2 mixed gas as a conversion agent. The recrystallized product is first added into water according to a solid-liquid ratio of 1:2 g / mL, and then stirred and dissolved. Then, the solution is pressurized and the NO / NO2 mixed gas is introduced according to an NH4 + / NO2 - molar ratio of 1:1.5, so that the solution is converted into ammonium nitrite and phosphoric acid. Then, the solution is slowly depressurized to allow the excess NO / NO2 mixed gas to volatilize and be recovered. When no gas bubbles are generated in the solution, the solution is heated to allow the ammonium nitrite to decompose slowly and orderly to release nitrogen gas. The solution is evaporated and concentrated until the specific gravity of the solution is increased to 1.57 g / mL. The heating is stopped, and the solution is cooled to room temperature. The quality of the sample is tested, and the quality of the sample reaches the quality standard of 75% phosphoric acid superior product specified in the national food safety standard GB / T 2091-2008. The consumption of sulfuric acid in the process is 63.2% of that in the traditional process, and the leaching rate of fluorine is 97.3%.

[0089] Comparative example

[0090] 300 g of phosphate rock powder with a P2O5 content of 29.64 wt% and a CaO content of 48.73 wt% is weighed, and water is added to the phosphate rock powder according to a solid-liquid ratio of 1:1 g / mL. Then, 98% concentrated sulfuric acid is slowly added dropwise according to a Ca / S molar ratio of 1:1.5, and the temperature of the reaction solution is maintained at 65-85°C. The stirring is continued for 2 h, and then the solution is filtered and washed to obtain 272.02 g of a phosphoric acid solution with a P2O5 concentration of 32.1% and 436.62 g of phosphogypsum with a P content of 0.36%.

[0091] The preferred embodiments of the application are described in detail above, but the application is not limited thereto. Within the technical concept of the application, various simple modifications can be made to the technical solutions of the application, including the combination of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as disclosed by the application and fall within the protection scope of the application.

Claims

1. A wet-process phosphoric acid production process for comprehensive utilization of phosphate rock full-element resources, characterized by comprising the following steps: The process comprises: ​ (1) decomposing phosphate ore, a decomposition solution and a base solution at a temperature of 60-120℃ for 0.25-2.5h, raising the mass concentration of P2O5 in the slurry to 30-50%, adjusting the pH value to 2.6-4.6 using an alkaline substance, filtering and washing while hot to obtain a primary decomposition solution and a primary decomposition residue; the decomposition solution is a solution containing ammonium bisulfate, and the base solution is water or a solution containing phosphoric acid; (2) crystallizing the primary decomposition solution to obtain ammonium dihydrogen phosphate crystals and a crystallization mother liquor; the crystallization mother liquor is returned to be used for preparing the decomposition solution or the base solution; using the ammonium dihydrogen phosphate crystals as a raw material for producing phosphoric acid and phosphate or directly selling them as products; (3) mixing the primary decomposition residue after slurry preparation with an ammonium carbonate salt, adjusting the pH value of the slurry to alkaline using ammonia or aqueous ammonia, placing it in a mixed atmosphere of CO2 and NH3 to perform ammonium carbonate transformation, and then filtering to obtain an ammonium sulfate solution and a calcium carbonate filter cake; the ammonium sulfate solution is returned to be used for preparing the decomposition solution or for comprehensive utilization; the calcium carbonate filter cake is placed in a solution containing calcium chloride with ammonium chloride to perform ammonium chloride transformation and filtering to obtain a mixed gas containing CO2 and NH3, a calcium chloride solution and an insoluble residue; alternatively, the calcium carbonate filter cake is mixed with ammonium chloride and calcined to perform ammonium chloride transformation to obtain a mixed gas containing CO2 and NH3 and CaCl2 calcine, dissolving the calcine in water and filtering to obtain a calcium chloride solution and an insoluble residue; the mixed gas containing CO2 and NH3 is returned to be used in the ammonium carbonate transformation and / or the production of calcium-containing compounds; the calcium chloride solution is used for the production of calcium-containing compounds and / or as a base solution for ammonium chloride transformation; (4) using the decomposition solution to perform secondary decomposition on the insoluble residue to extract residual phosphorus.

2. The wet-process phosphoric acid production process for comprehensive utilization of phosphate rock full-element resources according to claim 1, characterized in that: In step (2), impurity removal is also included, i.e., the primary decomposition solution is first purified to remove impurities and then crystallized, or the mother liquor obtained after crystallization is purified to remove impurities; the method for purifying and removing impurities is as follows: mixing the mother liquor obtained after crystallization or the primary decomposition solution with an alkali metal sulfate and stirring for 45-80min, the molar ratio of the alkali metal element in the alkali metal sulfate to the fluorine element in the mother liquor obtained after crystallization or the primary decomposition solution is 1:2.5-4, so that the fluorine is crystallized and separated in the form of fluosilicate.

3. The wet-process phosphoric acid production process for comprehensive utilization of phosphate rock full-element resources according to claim 1, characterized in that: The mass concentration of ammonium bisulfate in the decomposition solution is ≥20%.

4. The wet-process phosphoric acid production process for comprehensive utilization of phosphate rock full-element resources according to claim 1, characterized in that: In step (1), the molar ratio of Ca element in the phosphate ore to S element in the decomposition solution is 1:1-1.5; and / or, the solid-liquid ratio of the phosphate ore to the base solution is 1-5:1 g / mL.

5. The wet-process phosphoric acid production process for comprehensive utilization of phosphate rock full-element resources according to claim 1 or 2, characterized in that: The alkaline substance includes at least one of phosphate ore, calcium carbonate, diammonium phosphate, triammonium phosphate, ammonia and aqueous ammonia.

6. The wet-process phosphoric acid production process for comprehensive utilization of phosphate rock full-element resources according to claim 1 or 2, characterized in that: The operation of crystallizing the primary decomposition solution includes: cooling the primary decomposition solution to 0-30℃ to selectively crystallize ammonium dihydrogen phosphate.

7. The wet-process phosphoric acid production process for comprehensive utilization of phosphate rock full-element resources according to claim 1 or 2, characterized in that: The method for producing phosphoric acid from ammonium dihydrogen phosphate includes: using at least one of hydrochloric acid, HCl gas, a mixed gas of NO / NO2 with an equimolar ratio and nitrous acid as a transformation agent to convert the ammonium dihydrogen phosphate into phosphoric acid. 8.The wet-process phosphoric acid production process for comprehensive utilization of phosphate rock full-element resources according to claim 7, characterized in that: The method for producing phosphoric acid from ammonium dihydrogen phosphate crystals comprises: When hydrochloric acid or HCl gas is used as the transformation agent, the method comprises: firstly mixing and dissolving ammonium dihydrogen phosphate with hydrochloric acid or introducing HCl gas into the ammonium dihydrogen phosphate solution to convert the ammonium dihydrogen phosphate into phosphoric acid and ammonium chloride, then cooling to crystallize the ammonium chloride, filtering to obtain ammonium chloride crystals and a solution containing phosphoric acid, and finally evaporating and concentrating the solution containing phosphoric acid to volatilize excess HCl to obtain the phosphoric acid product; Alternatively, When an equimolar ratio of NO / NO2 mixed gas and / or nitrous acid is used as the transformation agent, the method comprises: introducing NO / NO2 mixed gas and / or nitrous acid into the ammonium dihydrogen phosphate solution to convert the ammonium dihydrogen phosphate into ammonium nitrite and phosphoric acid, then heating the ammonium nitrite to gradually decompose and release nitrogen, and finally evaporating and concentrating the decomposed liquid to obtain the phosphoric acid product. 9.The wet-process phosphoric acid production process for comprehensive utilization of phosphate rock full-element resources according to claim 1 or 2, characterized in that: The operation of ammonium chloride transformation specifically comprises: The calcium chloride-containing solution has a calcium chloride concentration of ≥20 wt.%; The method for producing calcium-containing compounds using the obtained calcium chloride solution comprises: 10.The wet-process phosphoric acid production process for comprehensive utilization of phosphate rock full-element resources according to claim 9, characterized in that: Introducing the mixed gas of CO2 and NH3 into the calcium chloride solution to generate calcium carbonate; Alternatively, Mixing the calcium chloride solution with a solution containing ammonium sulfate or ammonium sulfate crystals to produce calcium sulfate; the molar ratio of Ca in the calcium chloride solution to S in the ammonium sulfate on a dry basis is 1:0.8-1.2; Alternatively, Mixing the calcium chloride solution with sodium sulfate solid to produce calcium sulfate whiskers, and filtering to obtain calcium sulfate whiskers and a post-reaction liquid. Mixing the post-reaction liquid with the calcium chloride solution, filtering the precipitated sodium chloride crystals, and recycling the obtained filtrate to the calcium sulfate whisker production process. 11.The wet-process phosphoric acid production process for comprehensive utilization of phosphate rock full-element resources according to claim 10, characterized in that: ​