Wet-process phosphoric acid production process for phosphorite all-element resource comprehensive utilization

Abstract

The invention relates to a wet-process phosphoric acid production process for phosphorite all-element resource comprehensive utilization, and belongs to the field of phosphorus chemical industry production. The process comprises the following steps: decomposing phosphorite, a decomposition solution and a base solution to obtain a primary decomposition solution and primary decomposition slag; crystallizing the primary decomposition liquid to obtain ammonium dihydrogen phosphate crystals and crystallization mother liquor thereof; ammonium dihydrogen phosphate is directly sold as a product or transformed to produce high-quality phosphoric acid, and the obtained crystallization mother liquor is returned to be used for preparing a decomposition solution or a decomposition base solution; transforming the primary decomposition slag by ammonium bicarbonate to obtain an ammonium sulfate solution and a calcium carbonate filter cake; returning the ammonium sulfate solution for preparing decomposition liquid or comprehensively utilizing; transforming the calcium carbonate filter cake through ammonium chloride to obtain a mixed gas containing CO2 and NH3, a calcium chloride solution and insoluble filter residues; the calcium chloride solution further produces a calcium-containing compound. According to the process provided by the invention, the phosphogypsum can be consumed from the source, the consumption of sulfuric acid is low, the fluorine leaching rate is high, the comprehensive utilization rate of calcium resources is high, and the quality of phosphoric acid obtained through transformation is good.

Description

Technical Field

[0001] The present invention relates to a wet-process phosphoric acid production process for comprehensive utilization of all elements of phosphate rock, belonging to the field of phosphochemical production. Background Art

[0002] Wet-process phosphoric acid, in a broad sense, refers to phosphoric acid produced by decomposing phosphate rock with inorganic acids such as nitric acid, hydrochloric acid, sulfuric acid, and fluosilicic acid. The process of decomposing phosphate rock with sulfuric acid is different from that of other inorganic acids. Its remarkable feature is that in addition to the phosphoric acid solution, calcium sulfate precipitate is also produced after decomposition, and the two can be separated by simple filtration. The industrial application of sulfuric acid process for wet-process phosphoric acid has a history of more than 100 years and has now become a complete and modern production system. At present, the vast majority of wet-process phosphoric acid is prepared by the sulfuric acid process. Therefore, in a narrow sense, the commonly referred to wet-process phosphoric acid usually means phosphoric acid prepared by decomposing phosphate rock with sulfuric acid.

[0003] The wet-process phosphoric acid process for decomposing phosphate rock with sulfuric acid is divided into: dihydrate process, anhydrous process, hemihydrate process, dihydrate-hemihydrate recrystallization process, and hemihydrate-dihydrate recrystallization process, etc., according to the different hydrated forms of calcium sulfate crystals.

[0004] In the dihydrate process, during the control of the phosphate rock decomposition process, calcium precipitates in the form of dihydrate (gypsum) CaSO 4 •2H 2 O. Its advantages are that the calcium sulfate dihydrate has good stability, the formed crystal particles are uniform and coarse, and it is easy to filter and wash. The disadvantage is that the concentration of the produced phosphoric acid is dilute, the P 2 O 5 concentration is 31%, and the conversion rate of phosphorus is relatively low, usually only 97.5%.

[0005] In the anhydrous process, during the control of the phosphate rock decomposition process, calcium precipitates in the form of anhydrous substance (CaSO 4 ). The advantage of the anhydrous process is that the concentration of the obtained finished phosphoric acid is high, and the P 2 O 5 concentration is 50 - 55%. Its disadvantages are that the passivation of the phosphate rock surface is serious, the recovery rate of phosphorus is low, usually only 93%, the crystal particles of the anhydrous substance are fine, and it is difficult to filter and wash, making it difficult to industrialize.

[0006] In the hemihydrate process, during the control of the phosphate rock decomposition process, calcium precipitates in the form of hemihydrate (CaSO 4 •1 / 2H 2 O). The advantage of the hemihydrate process is that the concentration of the obtained phosphoric acid can reach 40 - 45% P 2 O 5, large precipitate particles can be formed, and good filtration performance can be obtained in a concentrated phosphoric acid medium. Its disadvantage is that the surface of the phosphate rock is prone to passivation during the decomposition process, and the conversion rate of phosphorus is low, generally 92 - 95%.

[0007] The dihydrate - hemihydrate recrystallization process ensures that calcium precipitates in the form of dihydrate (CaSO 4 •2H 2 O) by controlling the temperature of sulfuric acid decomposition of phosphate rock and reducing the concentration of phosphoric acid in the solution. Then, the reaction slurry is heated and concentrated to convert the precipitate into hemihydrate, and recrystallization is carried out to improve the recovery rate of phosphorus and the purity of by - product phosphogypsum. Its advantages are that the recovery rate of phosphorus is increased. Its disadvantages are: (1) The concentration of the obtained product phosphoric acid is still too low for the production concentration of phosphochemical products; (2) The heat distribution in the process is unreasonable. When decomposing phosphate rock, in order to maintain the formation of dihydrate at a relatively low temperature, a large amount of reaction heat needs to be removed, and during the recrystallization process, the temperature of the slurry needs to be increased by heating, suffering from the "cold - hot disease" of the process; (3) The hemihydrate crystal of calcium sulfate is a metastable solid phase, and the treatment of hemihydrate filter residue is relatively difficult, and troubles are often encountered in the actual operation process; (4) It is difficult to prevent the generation of anhydrous substances during the recrystallization process. Once "excessive dehydration" occurs, it will lead to poor filtration performance of the filter residue.

[0008] The hemihydrate - dihydrate recrystallization process is further divided into a dilute acid process and a concentrated acid process. The dilute acid process means that after the calcium sulfate hemihydrate crystal is formed in dilute phosphoric acid, it is directly converted into dihydrate without filtration, and then filtered and washed. Only one filtration is arranged in the process, so it is called a one - step process. The advantage of the one - step process is that only one filtration is arranged, the process is simple, and there is no requirement for the particle size of the hemihydrate crystal. The recovery rate of phosphorus in the process can reach 98%. Its disadvantage is that the concentration of phosphoric acid in the slurry in the process can be at most 30 - 32% P 2 O 5 , the concentration of the obtained finished phosphoric acid is still relatively low, and strong heat exchange must be carried out during recrystallization to maintain the temperature of the slurry at 50 - 60°C. The concentrated acid process means that after the calcium sulfate hemihydrate crystal is formed in concentrated phosphoric acid, it is filtered and appropriately washed, and then made to absorb water and converted into a dihydrate slurry, and finally filtered and washed. Since two filtrations are arranged in its process, it is called a two - step process. The advantages of the two - step process are: (1) The concentration of the obtained finished phosphoric acid is high, generally 40 - 45% P 2 O 5 , and it can be directly used as the raw material for most phosphate fertilizer production; (2) P 2 O 5The conversion rate is high, generally reaching over 98%, which is the process commonly used in wet-process sulfuric acid at present. However, its disadvantages are that it requires two filtrations, the process flow is relatively long, the operation is cumbersome, and the total time-consuming of the process is also relatively long, generally taking 4 - 5 hours, resulting in low production efficiency.

[0009] A common feature of the above wet-process phosphoric acid production processes is that only a small part of the decomposition slurry is used for filtering to produce phosphoric acid during the decomposition of phosphate rock, and the vast majority of the rest is used as recycled slurry to control the crystal state of gypsum. In addition to calcium sulfate (accounting for over 90%) in the filter residue obtained by filtration, it also contains a small amount of undecomposed phosphate rock, fluorosilicate precipitates, unwashed phosphoric acid and fluosilicic acid, possible phosphate precipitates, and insoluble impurities brought in with the phosphate rock. Such calcium sulfate precipitates are collectively referred to as phosphogypsum. Nearly half of the fluorine in the phosphate rock remains in the phosphogypsum during the wet-process phosphoric acid production process, resulting in an astonishing waste of fluorine resources. The output of phosphogypsum in the phosphorus chemical industry is huge. For every 1 ton of P 2 O 5 produced by the dihydrate process, 4 - 4.5 tons of phosphogypsum will be produced. Due to the presence of soluble phosphorus and fluorine in phosphogypsum, its leachate is acidic and highly harmful to the ecological environment. The root cause of phosphogypsum generation is that calcium elements are not comprehensively utilized during the decomposition process of phosphate rock. Summary of the Invention

[0010] Aiming at the problems existing in the above-mentioned prior art, the purpose of the present invention is to provide a wet-process phosphoric acid production process for comprehensive utilization of all elements of phosphate rock. The process provided by the present invention can eliminate 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 the phosphoric acid produced has a high concentration and good quality.

[0011] To achieve the above purpose, the first aspect of the present invention is to provide a wet-process phosphoric acid production process for comprehensive utilization of all elements of phosphate rock, which includes:

[0012] (1) Decompose phosphate rock, decomposition liquid, and bottom liquid at a temperature of 60 - 120 °C for 0.25 - 2.5 h. When the mass concentration of P 2 O 5 in the slurry rises to 30 - 50%, adjust the pH value to 2.6 - 4.6 with an alkaline substance, filter and wash while it is hot to obtain a primary decomposition liquid and a primary decomposition residue; the decomposition liquid is a solution containing ammonium bisulfate, and the bottom liquid is water or a solution containing phosphoric acid;

[0013] (2) Crystallize the primary decomposition liquid to obtain ammonium dihydrogen phosphate crystals and a crystallization mother liquor; the crystallization mother liquor is returned for preparing the decomposition liquid or the decomposition bottom liquid;

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

[0015] (3) After slurrying the primary decomposition residue, mix it with ammonium carbonate salt, adjust the pH of the slurry to alkaline with ammonia or aqueous ammonia, and place it in a mixed atmosphere of CO 2 and NH 3 for ammonium bicarbonate transformation, then filter and separate to obtain ammonium sulfate solution and calcium carbonate filter cake;

[0016] The ammonium sulfate solution is returned for formulating the decomposition liquid or for comprehensive utilization;

[0017] The calcium carbonate filter cake and ammonium chloride are placed in a solution containing calcium chloride for ammonium chloride transformation and filtration to obtain a mixed gas containing CO 2 and NH 3 , as well as calcium chloride solution and insoluble filter residue;

[0018] Alternatively, the calcium carbonate filter cake and ammonium chloride are mixed and roasted for ammonium chloride transformation to obtain a mixed gas containing CO 2 and NH 3 and CaCl 2 calcined sand. The calcined sand is dissolved in water and filtered to obtain calcium chloride solution and insoluble filter residue;

[0019] The mixed gas containing CO 2 and NH 3 is recycled for the ammonium bicarbonate transformation and / or the production of calcium-containing compounds;

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

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

[0022] The present invention innovatively uses a solution containing ammonium bisulfate as the decomposition liquid 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 during the decomposition process is also much lighter. The heat generated by the reaction is consumed by the heat dissipation of the equipment, the endothermic evaporation of water, and the physical heat carried away by the materials. Further, the decomposition rate of phosphate rock in ammonium bisulfate is very fast, and there is no need to worry about the conversion rate of P 2 O 5 during the decomposition process of phosphate rock, nor the generation of phosphate rock passivation phenomenon. Moreover, the generated precipitate is easy to filter, does not cake during the filtration and washing processes, and there is no special requirement for the crystal state of the precipitate generated by the present invention. There is no need for specific selection, and the precipitate can be any one or several of dihydrate gypsum, hemihydrate gypsum, and anhydrous gypsum.

[0023] Furthermore, the decomposition of phosphate rock can be carried out in the temperature range of 60 - 120 °C, and the decomposition time only needs 0.25 - 2.5 h, which greatly improves the operation efficiency of phosphate rock decomposition. Due to the short time required for phosphate rock decomposition and the small amount of recycled slurry during the decomposition process, the power consumption for stirring and slurry transportation during the phosphate rock decomposition process is less, and at the same time, the filtration burden of the decomposed slurry is also reduced. In addition, after the primary decomposition residue of phosphate rock undergoes two transformations with ammonium bicarbonate and ammonium chloride, the phosphorus and fluorine in it are mainly concentrated in the insoluble filter residue. The insoluble filter residue is collected and returned to continue the secondary decomposition with a solution containing ammonium bisulfate to recover phosphorus and fluorine.

[0024] Furthermore, the ammonium dihydrogen phosphate in the primary decomposition liquid can be selectively crystallized out by cooling, realizing the effective separation of phosphorus and impurities. The purity of the obtained ammonium dihydrogen phosphate crystals will be further improved after recrystallization. Using the ammonium dihydrogen phosphate obtained by crystallization to produce phosphoric acid can obtain high-quality phosphoric acid products. Compared with the traditional wet-process phosphoric acid production process, it has the advantages of simple production process, good product quality, and low production cost.

[0025] The basic principle of the wet-process phosphoric acid production process for the comprehensive utilization of all elements of phosphate rock is as follows:

[0026] (NH 4 ) 2 SO 4 + H 2 SO 4 = 2NH 4 HSO 4 (1)

[0027] Ca 5 F(PO 4 ) 3 + 6NH 4 HSO 4 + 5xH 2 O =Δ= 3NH 4 H 2 PO 4 + 5CaSO 4 •xH 2 O↓ +

[0028] NH 4 F + (NH 4 ) 2 SO 4 ,x = 0~2 (2)

[0029] 4NH 4 HSO 4 + SiO 2 + 6NH 4 F = (NH 4 )2 SiF 6 + 4(NH 4 ) 2 SO 4 + 2H 2 O (3)

[0030] NH 4 H 2 PO 4 + HCl = H 3 PO 4 + NH 4 Cl↓ (4)

[0031] 2NH 4 H 2 PO 4 + NO + NO 2 = H 3 PO 4 + N 2 ↑ + 2H 2 O (5)

[0032] CaSO 4 •xH 2 O + 2NH 3 + CO 2 = (NH 4 ) 2 SO 4 + CaCO 3 ↓ + (x - 1)H 2 O (6)

[0033] CaCO 3 + 2NH 4 Cl =Δ= CaCl 2 + H 2 O + CO 2 ↑ + 2NH 3 ↑ (7)

[0034] CaCl 2 + CO 2 + 2NH 3 + H 2 O = CaCO 3 ↓ + 2NH 4 Cl (8)

[0035] CaCl 2 + (NH 4 ) 2 SO 4 + nH 2 O = CaSO4 •nH 2 O↓ + 2NH 4 Cl, n = 0~2 (9)

[0036] (NH 4 ) 2 SiF 6 + Na 2 SO 4 = (NH 4 ) 2 SO 4 + Na 2 SiF 6 ↓ (10)

[0037] Using the ammonium sulfate solution obtained by transforming the primary decomposition residue with ammonium bicarbonate to replace sulfuric acid for decomposing phosphate rock can not only effectively inhibit the dissolution of impurities during the decomposition process, but also enable the secondary utilization of sulfate radicals during the decomposition process of phosphate rock, significantly reducing the sulfuric acid consumption. Decompose the phosphate rock by adding ammonium bisulfate at 1 to 1.5 times the stoichiometric amount, heat and stir for 0.5 h, and the primary leaching rate of P 2 O 5 can reach 85-93%. After transforming the primary decomposition residue with ammonium bicarbonate to obtain calcium carbonate filter cake, perform ammonium chloride transformation again, and leach the obtained insoluble filter residue with a solution containing ammonium bisulfate, which can increase the decomposition rate of phosphorus to the extreme. The leaching rate of phosphorus during the decomposition process of phosphate rock ≥ 99%, the leaching rate of fluorine ≥ 97%, and the comprehensive utilization rate of calcium resources in the whole process ≥ 95%. Compared with the traditional process, the theoretical sulfuric acid consumption is saved by 40%. The reduction in the sulfuric acid consumption required for phosphate rock decomposition significantly reduces the cooling load of the reaction slurry during the phosphate rock decomposition process.

[0038] It should be noted that there are no special requirements for the type of phosphate rock and the composition and content of substances in the phosphate rock in the present invention, and those known in the art can be used.

[0039] As a preferred solution, purification and impurity removal are also included in step (2). The primary decomposition liquid is first purified and impurity-removed and then crystallized, or the mother liquor obtained after crystallization is purified and impurity-removed.

[0040] As a preferred solution, the method for purification and impurity removal is: mixing and stirring the mother liquor obtained after crystallization or the primary decomposition liquid with alkali metal sulfate for 45 min to 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 liquid is 1:2.5 to 4, so that fluorine crystallizes and separates in the form of fluorosilicate.

[0041] As a more preferred solution, the steps of purification and impurity removal are as follows: First, mix the crystallization mother liquor or the primary decomposition liquor with alkali metal sulfate and stir for 45 min to 80 min, so that fluorine in the crystallization mother liquor or the primary decomposition liquor crystallizes and separates in the form of fluorosilicate. Then, adjust the pH value of the liquid obtained after crystallization to 6 to 9 to precipitate the remaining impurities again. After filtration, the crystallization mother liquor is obtained, and then the purified crystallization mother liquor is returned for preparing the decomposition liquor or the decomposition bottom liquor.

[0042] As a preferred solution, in step (3), the specific steps of ammonium bicarbonate transformation include: slurrying the primary decomposition residue and mixing it with ammonium carbonate salt, adjusting the pH of the slurry to 8 to 9 with ammonia or ammonia water, and reacting it in a mixed atmosphere of CO 2 and NH 3 for 0.5 h to 2.5 h for ammonium bicarbonate transformation, and then filtering and separating to obtain ammonium sulfate solution and 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 to 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 liquor is ≥20%.

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

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

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

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

[0049] As a preferred solution, the mass concentration of P 2 O 5 in the phosphoric acid-containing solution is ≥10%, and the solid content is 0 to 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 liquid.

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

[0053] As a preferred solution, the operation of crystallizing the primary decomposition liquid includes: cooling the primary decomposition liquid to 0-30°C to selectively precipitate ammonium dihydrogen phosphate therefrom.

[0054] As a preferred solution, the method for producing phosphoric acid from ammonium dihydrogen phosphate crystals includes: using at least one of hydrochloric acid, HCl gas, a mixed gas of NO / NO with an equimolar ratio, and nitrous acid as a transformation agent to convert the ammonium dihydrogen phosphate into phosphoric acid. 2 Mixing gas and nitrous acid as a transformation agent to convert the ammonium dihydrogen phosphate into phosphoric acid.

[0055] As a more preferred solution, when using hydrochloric acid or HCl gas as the transformation agent, the method includes: first mixing and dissolving ammonium dihydrogen phosphate with hydrochloric acid or introducing HCl gas into the ammonium dihydrogen phosphate solution to convert ammonium dihydrogen phosphate into phosphoric acid and ammonium chloride, then cooling to precipitate ammonium chloride crystals, filtering to obtain ammonium chloride crystals and a phosphoric acid-containing solution, and finally evaporating and concentrating the phosphoric acid-containing solution to volatilize excess HCl to obtain a phosphoric acid product. The present invention ingeniously uses ammonium dihydrogen phosphate and its recrystallized product as raw materials for the production of wet-process phosphoric acid, greatly simplifies the production process of high-quality wet-process phosphoric acid, uses hydrochloric acid or HCl gas as the transformation agent, utilizes the principle of strong acid displacing weak acid, first converts ammonium dihydrogen phosphate into a phosphoric acid solution and ammonium chloride crystals, then evaporates and concentrates the obtained phosphoric acid solution to obtain a high-quality phosphoric acid product, collects and returns the obtained HCl gas to the transformation process for recycling, and also realizes the recycling of HCl in the phosphoric acid production process, having the advantages of simple process, good product quality, low production cost, environmental friendliness, etc.

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

[0057] As a preferred solution, the step of cooling to precipitate ammonium chloride crystals specifically includes: first cooling the solution obtained after transformation to 10-30°C, and precipitating ammonium chloride crystals under the action of the common ion effect of Cl - Ions, and after solid-liquid separation, deeply crystallizing ammonium chloride from the filtrate under the condition of 9°C to -35°C.

[0058] As a more preferred solution, with an equimolar ratio of NO / NO 2When a mixed gas and / or nitrous acid is used as a conversion agent, the method includes: introducing NO / NO 2 mixed gas and / or nitrous acid into the ammonium dihydrogen phosphate solution to convert ammonium dihydrogen phosphate into ammonium nitrite and phosphoric acid, then heating ammonium nitrite to gradually decompose and release nitrogen gas, and finally evaporating and concentrating the decomposed liquid to obtain a phosphoric acid product.

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

[0060] As a preferred embodiment, the operation of ammonium chloride conversion specifically includes: placing the calcium carbonate filter cake and ammonium chloride in a solution containing calcium chloride, and rapidly decomposing calcium carbonate at 105-175°C for 1-3 hours for ammonium chloride conversion to obtain a mixed gas containing CO 2 and NH 3 , as well as a calcium chloride solution and insoluble filter residue; the molar ratio of Ca element in the calcium carbonate filter cake to Cl element in the ammonium chloride is 1:2-3; the calcium chloride concentration in the solution containing calcium chloride is ≥20 wt.%. Selecting the calcium chloride-containing solution as the reaction bottom liquid is mainly based on the fact that the reaction of ammonium chloride decomposing calcium carbonate in an aqueous solution belongs to an endothermic reaction type. The purpose of selecting the calcium chloride-containing solution as the reaction bottom liquid is to: utilize the characteristic that the boiling point of the CaCl 2 solution increases with the increase of its concentration. When the concentration of the calcium chloride solution reaches 20%, the boiling point temperature of the CaCl 2 solution can be increased to ≥105°C, which can meet the process temperature required for the rapid decomposition of calcium carbonate by ammonium chloride in the solution, and the product obtained by the reaction is also CaCl 2 , which facilitates its recovery and utilization.

[0061] In the calcium chloride-containing solution of the present invention, the calcium chloride concentration is further preferably 30 wt.% - 55 wt.%.

[0062] As a preferred embodiment, the operation of ammonium chloride conversion specifically includes: mixing and roasting the calcium carbonate filter cake and ammonium chloride at 250-500°C for 1-3 hours to obtain a mixed gas containing CO 2 and NH 3 and CaCl 2 roasted sand. The roasted sand is dissolved in water and filtered to obtain a calcium chloride solution and insoluble filter residue; the molar ratio of Ca element in the calcium carbonate filter cake to Cl element in the ammonium chloride is 1:2-2.2.

[0063] As a preferred embodiment, the method of using the obtained calcium chloride solution for the production of calcium-containing compounds includes: introducing a mixed gas of CO 2 and NH 3 into the calcium chloride solution to generate calcium carbonate.

[0064] As a preferred embodiment, the method of using the obtained calcium chloride solution for the production of calcium-containing compounds includes: introducing a mixed gas of CO 2 and NH 3 into the calcium chloride solution, adjusting the pH value to 8-9 to precipitate calcium carbonate, and then filtering, washing, and drying to obtain the precipitated calcium carbonate product.

[0065] As a preferred embodiment, the washing water mentioned in the washing and the filtrate obtained by filtration are combined and then evaporated, concentrated, and crystallized to recover ammonium chloride, and the ammonium chloride is recycled and used in the ammonium chloride transformation process.

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

[0067] As a preferred embodiment, the method of using the obtained calcium chloride solution for the production of calcium-containing compounds includes: mixing the calcium chloride solution with solid sodium sulfate to produce calcium sulfate whiskers, and filtering to obtain calcium sulfate whiskers and the reaction solution.

[0068] As a preferred embodiment, the reaction solution is mixed with the calcium chloride solution, the precipitated sodium chloride crystals are filtered, and the obtained filtrate is returned to the calcium sulfate whisker production process for recycling.

[0069] As a preferred embodiment, the comprehensive utilization includes using ammonium sulfate solution to produce ammonium sulfate fertilizer and / or produce calcium sulfate.

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

[0071] (1) In the present invention, the ammonium bisulfate solution prepared by mixing the ammonium sulfate solution obtained by transforming the primary decomposition residue with sulfuric acid is used as the decomposition liquid of phosphate rock, significantly reducing the amount of sulfuric acid required for phosphate rock decomposition; and after the primary decomposition liquid is cooled, ammonium dihydrogen phosphate can be selectively crystallized out, and the ammonium dihydrogen phosphate obtained by crystallization is used to transform and produce phosphoric acid, and high-quality phosphoric acid products can be obtained. Compared with the traditional wet-process phosphoric acid production process, it has the advantages of simple production process, good product quality, low production cost, etc., and has strong market competitiveness.

[0072] (2) After the decomposition of phosphate rock, the primary decomposition residue is subjected to ammonium bicarbonate transformation and ammonium chloride transformation, and the resulting calcium chloride solution is used to produce industrial precipitated calcium carbonate, precipitated calcium sulfate and calcium sulfate whiskers, so that both calcium and sulfate radicals in it are fully utilized. This not only comprehensively utilizes the calcium in phosphate rock in a resourceful way, but also greatly improves the comprehensive economic benefits of the wet-process phosphoric acid production process.

[0073] (3) The process provided by the present invention can consume phosphogypsum from the source, and can effectively utilize phosphorus, fluorine and calcium with high utilization rates. Specific embodiments

[0074] In the ranges disclosed herein, the endpoints and any values are not limited to the exact ranges or values. These ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0075] The following further illustrates the present invention in conjunction with specific embodiments, but the protection scope of the present invention is not limited to the following specific embodiments. Obviously, the embodiments described below are only a part of the embodiments, and all other embodiments obtained by those skilled in the art without creative efforts still fall within the protection scope of the present invention.

[0076] Unless otherwise specifically stated, various raw materials, reagents, instruments and equipment used in the present invention can be obtained through market purchases or can be prepared by existing methods.

[0077] Example 1

[0078] Weigh 1000 g of phosphate rock powder with a P 2 O 5 content of 32.15 wt% and a CaO content of 50.16 wt%. First, adjust the slurry with water according to a solid-liquid ratio of 3:1 g / mL and heat it to a temperature of 65 °C. Then, slowly add an ammonium bisulfate solution with a mass concentration of 40% while stirring according to a Ca / S molar ratio of 1:1.2. After adding the ammonium bisulfate solution, raise the temperature of the solution to 85 °C, and keep stirring at a constant temperature for 0.5 h (at this time, the mass concentration of P 2 O 5 in the slurry is 41.9 wt%). Add diammonium phosphate to adjust the pH value of the slurry to 4.2, filter and wash while it is hot to obtain the primary decomposition liquid and the primary decomposition residue;

[0079] Cool the primary decomposition liquid to room temperature to crystallize out ammonium dihydrogen phosphate. Filter to obtain ammonium dihydrogen phosphate crystals and its crystallization mother liquor. Then, recrystallize the obtained ammonium dihydrogen phosphate crystals with saturated ammonium dihydrogen phosphate solution to obtain ammonium dihydrogen phosphate products that meet the quality requirements of Class I specified in HG / T 4133-2021 for industrial ammonium dihydrogen phosphate. Adjust the pH value of its crystallization mother liquor to 7 by adding ammonia water after first adding potassium sulfate to crystallize potassium fluorosilicate to remove fluorine according to a K / F molar ratio of 1:3. Filter to remove other impurities. The purified liquid after impurity removal is returned for preparing the decomposition liquid and the decomposition bottom liquid;

[0080] First, adjust the slurry concentration of the obtained primary decomposition residue by adding water according to a solid-liquid ratio of 1:1 g / mL, and then, according to a Ca / C molar ratio of 1:1.2, introduce a mixed gas of CO 2 and NH 3 into the slurry for ammonium bicarbonate transformation. Adjust the pH of the solution to 8.5 with ammonia and stir at room temperature for 1 h to convert calcium sulfate therein into calcium carbonate. Filter to obtain ammonium sulfate solution and calcium carbonate filter cake. Divide the obtained ammonium sulfate solution into two parts. One part is returned for preparing ammonium bisulfate solution, and the other part is used for comprehensive utilization. Mix the obtained calcium carbonate filter cake with ammonium chloride according to a Ca / Cl molar ratio of 1:2.1 to form pellets. After the pellets are air-dried, roast them at a temperature of 465 °C for 1 h to obtain roasted ore containing CaCl 2 and flue gas containing CO 2 and NH 3 . Collect the roasting flue gas for ammonium bicarbonate transformation of the primary decomposition residue. Dissolve the roasted ore in water and filter to obtain calcium chloride solution and insoluble filter residue. Continue to decompose the insoluble filter residue with ammonium bisulfate solution until the P content therein drops to <0.05%. Finally, divide the obtained calcium chloride solution into two parts. One part is stirred and mixed with the ammonium sulfate solution obtained from ammonium bicarbonate transformation according to a Ca / S molar ratio of 1:1, and then filtered to obtain precipitated calcium sulfate products. The other part is used as the reaction bottom liquid for ammonium chloride transformation of the calcium carbonate filter cake. The leaching rate of phosphorus in the process is 99.4%, the leaching rate of fluorine is 97.8%, and the comprehensive utilization rate of calcium resource reaches 96.7%.

[0081] Example 2

[0082] Weigh 500 g of phosphate rock powder with a P 2 O 5 content of 30.62 wt% and a CaO content of 49.05 wt% at -150 mesh, and add it to the purified and impurity-removed ammonium dihydrogen phosphate crystallization mother liquor obtained in Example 1 according to a solid-liquid ratio of 1:1 g / mL to form a slurry. Stir and heat, and slowly add a 47% ammonium bisulfate solution preheated to 85 °C, which is prepared by mixing the ammonium sulfate solution obtained in Example 1 with sulfuric acid, according to a Ca / S molar ratio of 1:1.2. After the addition of the ammonium bisulfate solution is complete, continue to stir and react at a constant temperature of 110 °C for 0.25 h (at this time, P 2 O5 with a mass concentration of 37.6 wt%), then first add 110 g of a slurry prepared from phosphate rock powder and water to roughly adjust the pH of the slurry, and then add concentrated ammonia water to adjust the pH of the slurry to 4.5. Filter and wash while it is hot to obtain a primary decomposition liquid and a primary decomposition residue;

[0083] The obtained primary decomposition residue is first slurried by adding water according to a solid-liquid ratio of 1:1 g / mL, and then ammonium bicarbonate is added to the slurry according to a Ca / C molar ratio of 1:1.2 for ammonium bicarbonate transformation. Use ammonia to adjust the pH of the solution to 8.2, stir at room temperature for 1 h to convert calcium sulfate into calcium carbonate, filter to obtain ammonium sulfate solution and calcium carbonate filter cake, and divide the obtained ammonium sulfate solution into two parts. One part is returned for preparing the decomposition liquid, and the other part is evaporated and concentrated to crystallize agricultural ammonium sulfate fertilizer. The obtained calcium carbonate filter cake is first mixed with ammonium chloride according to a Ca / Cl molar ratio of 1:2.4, and then slowly stirred and added to the calcium chloride-containing solution (the concentration of calcium chloride is 43.7 wt.%) heated to 120 °C obtained in Example 1 for reaction for 1.5 h to make it decompose rapidly and convert into a calcium chloride-containing slurry and a mixed gas containing CO 2 and NH 3 The mixed gas is collected and returned for ammonium bicarbonate transformation of the primary decomposition residue. The slurry is filtered to obtain a calcium chloride solution and an insoluble filter residue. The insoluble filter residue is continuously decomposed with ammonium bisulfate solution until the P content therein drops to 0.03% and the phosphorus leaching rate reaches 99.6%. Divide the obtained calcium chloride solution 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 through a mixed gas containing CO 2 and NH 3 The mixed gas causes calcium to precipitate out under the condition of a pH of 8.6. Filter, wash, and dry to obtain industrial precipitated calcium carbonate. The obtained filtrate and washing water are combined and evaporated and concentrated to crystallize and recover ammonium chloride, and the ammonium chloride crystals are returned to the ammonium chloride transformation process for recycling. The comprehensive utilization rate of calcium resources in the whole process is 97.6%.

[0084] The primary decomposition solution is naturally cooled and crystallized to precipitate ammonium dihydrogen phosphate. After filtration, ammonium dihydrogen phosphate crystals and their crystallization mother liquor are obtained. Then, the crystallization mother liquor is purified to remove impurities. First, potassium sulfate is added to the crystallization mother liquor according to a K / F molar ratio of 1:3 to crystallize potassium fluorosilicate for defluorination. Then, ammonia water is added to adjust the pH value to 7, and other impurities are removed by filtration. The purified solution after impurity removal is returned for preparing the decomposition solution and the bottom decomposition solution. The obtained ammonium dihydrogen phosphate crystals are recrystallized with a saturated ammonium dihydrogen phosphate solution, and the ammonium dihydrogen phosphate solution obtained by recrystallization is transformed to produce phosphoric acid. Hydrochloric acid is used as the transformation agent. First, the recrystallized product is added to 37% hydrochloric acid according to a solid-liquid ratio of 1:1 g / mL (the molar ratio of ammonium dihydrogen phosphate to HCl based on dry basis is 1:1.4). It is stirred and heated to dissolve, and then naturally cooled. When the solution temperature drops to room temperature, it is placed in an environment of -25°C for freeze crystallization for 16 h to force the deep crystallization of ammonium chloride. After filtration, the filtrate is heated and evaporated and concentrated. The HCl volatilized during the concentration process is collected and reused. When the specific gravity of the solution rises to 1.54 g / mL, heating is stopped, and it is cooled to room temperature. Sampling and testing show that its quality meets the quality standard of food additive - phosphoric acid specified in the national food safety standard GB 1886.15 - 2015. The consumption of sulfuric acid in the process is 65.8% of that in the traditional process, and the fluorine leaching rate is 98.1%.

[0085] Example 3

[0086] Weigh 500 g of phosphate rock powder with a P 2 O 5 content of 29.64 wt% and a CaO content of 48.73 wt%. Add it to the purified and impurity-removed ammonium dihydrogen phosphate crystallization mother liquor obtained in Example 2 according to a solid-liquid ratio of 1:1 g / mL to form a slurry. Stir and heat it to a temperature of 98°C, and slowly add an ammonium bisulfate solution with a mass concentration of 36% preheated to 95°C and prepared by blending ammonium sulfate solution and sulfuric acid obtained in Example 2 according to a Ca / S molar ratio of 1:1.1. After the addition of the ammonium bisulfate solution is completed, continue to stir and react at a constant temperature of 115°C for 0.5 h (at this time, the mass concentration of P 2 O 5 in the slurry is 41.8 wt%). Use calcium carbonate powder to adjust the pH of the slurry to 3.5, filter and wash while it is hot to obtain the primary decomposition solution and the primary decomposition residue;

[0087] The obtained primary decomposition residue is first slurried by adding water according to a solid-liquid ratio of 1:1 g / mL, and then transformed by adding ammonium bicarbonate to the slurry according to a Ca / C molar ratio of 1:1.2. Use ammonia to adjust the pH of the solution to 8.5, and stir at room temperature for 1 h to convert calcium sulfate into calcium carbonate. Filter to obtain ammonium sulfate solution and calcium carbonate filter cake. Add the obtained ammonium sulfate solution for transformation with sodium bicarbonate according to stoichiometry, evaporate and concentrate, and crystallize to obtain solid sodium sulfate. The CO 2 and NH3 Collect the mixed gas and return it for the ammonium bicarbonate transformation of the primary decomposition residue. First, mix the obtained calcium carbonate filter cake with ammonium chloride according to a Ca / Cl molar ratio of 1:2.3, and then slowly stir and add it to the calcium chloride-containing solution heated to 130 °C obtained in Example 2 (the concentration of calcium chloride is 51.6 wt.%) and react for 1 h to cause rapid decomposition, converting it into a calcium chloride-containing slurry and a mixed gas containing CO 2 and NH 3 The mixed gas is collected for the production of ammonium carbonate. The slurry is filtered to obtain a calcium chloride solution and an insoluble filter residue. The insoluble filter residue is continuously decomposed with an ammonium bisulfate solution until the P content therein drops to 0.04%, the calcium dissolution rate is 98.1%, and the phosphorus leaching rate reaches 99.3%. Then, solid sodium sulfate is slowly added to the obtained calcium chloride solution with stirring, and the reaction is carried out at 45 °C for 8 h. After filtration and washing, gypsum whiskers with an aspect ratio of 10 - 100 and its reaction mother liquor are obtained. After the obtained gypsum whiskers are washed, they are dried at 400 °C for 2 h to obtain an anhydrous gypsum whisker product with a whiteness > 96%. Then, a calcium chloride solution with a concentration of 45% is added to the reaction mother liquor to force the crystallization of sodium chloride. After filtration, the obtained sodium chloride crystals are dissolved in water to form a saturated solution, and CO 2 and NH 3 The mixed gas is first allowed to crystallize out sodium bicarbonate, and then cooled and crystallized to separate ammonium chloride. The obtained sodium bicarbonate and ammonium chloride are both returned to the process for recycling.

[0088] Heat and keep the primary decomposition liquid warm, and slowly add sodium sulfate to it with stirring according to a Na / F molar ratio of 1:3. After the addition of sodium sulfate is complete, continue stirring for 1 h, and then perform secondary filtration while it is hot to separate the crystallized sodium fluorosilicate crystals. Then, let the defluorinated liquid cool and crystallize to separate ammonium dihydrogen phosphate. After filtration, ammonium dihydrogen phosphate crystals and the purified crystallization mother liquor are obtained. The purified crystallization mother liquor is returned for preparing the decomposition liquid and the decomposition bottom liquid; and the obtained ammonium dihydrogen phosphate crystals are recrystallized with the saturated ammonium dihydrogen phosphate solution used in Example 2, and the obtained recrystallized product is transformed to produce phosphoric acid. Use a NO / NO 2 The mixed gas is used as a transformation agent. First, add the recrystallized product to water according to a solid-liquid ratio of 1:2 g / mL, stir and dissolve it, and then pressurize and introduce a NO / NO 4 + / NO 2 - mixed gas according to a molar ratio of 1:1.5 to convert it into ammonium nitrite and phosphoric acid, and then slowly release the pressure to let the excess NO / NO 2 mixed gas 2The mixed gas volatilizes and is recovered. When no bubbles are generated in the solution, heat is applied to slowly and orderly decompose ammonium nitrite in the solution to release nitrogen gas. Then, the obtained decomposed solution is evaporated and concentrated. When the specific gravity of the solution rises to 1.57 g / mL, heating is stopped, and it is cooled to room temperature. A sample is taken for testing, and its quality meets the quality standard of the first-class product of 75% phosphoric acid 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] Weigh 300 g of phosphate rock powder with a P 2 O 5 content of 29.64 wt% and a CaO content of 48.73 wt%. Adjust the slurry with water at a solid-liquid ratio of 1:1 g / mL, and then slowly add 98% concentrated sulfuric acid at a Ca / S molar ratio of 1:1.5. Maintain the temperature of the reaction solution at 65-85 °C, stir and react for 2 h, filter and wash to obtain a phosphoric acid solution with a P 2 O 5 concentration of 32.1% and 436.62 g of phosphogypsum containing 0.36% P.

[0091] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. Within the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, including any other suitable combination of each technical feature. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.

Claims

1. A wet-process phosphoric acid production process for comprehensive utilization of all elements of phosphate ore, characterized by: The process includes: (1) Decomposing the phosphate rock, decomposition liquid and bottom liquid at a temperature of 60-120° C. for 0.25-2.5 h, and when the mass concentration of P2O5 in the slurry rises to 30-50%, adjusting the pH value to 2.6-4.6 with an alkaline substance, filtering and washing while hot to obtain a primary decomposition liquid and a primary decomposition slag; the decomposition liquid is a solution containing ammonium bisulfate, and the bottom liquid is water or a solution containing phosphoric acid; (2) crystallizing the primary decomposition liquid to obtain diammonium phosphate crystals and a crystallization mother liquor; the crystallization mother liquor is returned to prepare the decomposition liquid or the decomposition base liquid; Using the diammonium phosphate crystals as a raw material for the production of phosphoric acid and phosphates or directly selling them as products; (3) slurrying the primary decomposition slag and mixing it with ammonium carbonate salt, adjusting the pH of the slurry to alkaline with ammonia or ammonia water, placing it in a mixed atmosphere of CO2 and NH3 for carbonate-ammonium transformation, filtering and separating to obtain ammonium sulfate solution and calcium carbonate filter cake; The ammonium sulfate solution is returned for preparing the decomposition solution or for comprehensive utilization; The calcium carbonate filter cake and ammonium chloride are placed in a solution containing calcium chloride, and the ammonium chloride is transformed and filtered to obtain a mixed gas containing CO2 and NH3, as well as a calcium chloride solution and an insoluble filter residue; Alternatively, the calcium carbonate filter cake is mixed with ammonium chloride and roasted to transform the ammonium chloride to obtain a mixed gas containing CO2 and NH3 and CaCl2 roasted sand, and the roasted sand is dissolved in water and filtered to obtain a calcium chloride solution and an insoluble filter residue; The mixed gas containing CO2 and NH3 is recycled in the carbon ammonium transformation and / or the production of calcium-containing compounds; The calcium chloride solution is used as the production of calcium-containing compounds and / or as the base liquid for the transformation of ammonium chloride; (4) The insoluble filter residue is subjected to secondary decomposition using the decomposition liquid to extract the residual phosphorus.

2. The wet-process phosphoric acid production process for comprehensive utilization of all elements of phosphate rock according to claim 1, characterized in that: Step (2) also includes purification and impurity removal, wherein the primary decomposition liquid is first purified and impurity removed before crystallization, or the mother liquor obtained after the crystallization is purified and impurity removed; The purification and impurity removal method is: mixing the mother liquor or the primary decomposition liquid obtained after crystallization with alkali metal sulfate and stirring for 45 minutes to 80 minutes, wherein the molar ratio of the alkali metal element in the alkali metal sulfate to the fluorine element in the mother liquor or the primary decomposition liquid obtained after crystallization is 1:2.5 to 4, so that fluorine is crystallized and separated in the form of fluorosilicate.

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

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

6. A wet-process phosphoric acid production process for comprehensive utilization of all elements of phosphate ore according to claim 1 or 2, characterized in that: The operation of crystallizing the primary decomposition liquid includes: cooling the primary decomposition liquid to 0-30° C. to allow the ammonium dihydrogen phosphate therein to selectively crystallize and precipitate.

7. A wet-process phosphoric acid production process for comprehensive utilization of all elements of phosphate ore according to claim 1 or 2, characterized in that: The method for producing phosphoric acid from diammonium phosphate crystals comprises: using at least one of hydrochloric acid, HCl gas, NO / NO2 mixed gas with an equal molar ratio and nitrous acid as a conversion agent to convert the diammonium phosphate into phosphoric acid.

8. The wet-process phosphoric acid production process for comprehensive utilization of all elements of phosphate rock according to claim 7, characterized in that: The method for producing phosphoric acid from diammonium phosphate crystals comprises: When hydrochloric acid or HCl gas is used as a conversion agent, the method comprises: firstly dissolving ammonium dihydrogen phosphate and hydrochloric acid in a mixture or introducing HCl gas into the ammonium dihydrogen phosphate solution to convert the ammonium dihydrogen phosphate into phosphoric acid and ammonium chloride, then cooling the ammonium chloride to crystallize out, filtering to obtain ammonium chloride crystals and a phosphoric acid-containing solution, and finally evaporating and concentrating the phosphoric acid-containing solution to volatilize excess HCl to obtain a phosphoric acid product; or, When NO / NO2 mixed gas and / or nitrous acid in an equal molar ratio are used as the conversion agent, the method comprises: introducing NO / NO2 mixed gas and / or nitrous acid into a diammonium phosphate solution to convert the diammonium 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 a phosphoric acid product.

9. A wet-process phosphoric acid production process for comprehensive utilization of all elements of phosphate ore according to claim 1 or 2, characterized in that: The operation of ammonium chloride transformation specifically includes: The calcium carbonate filter cake and ammonium chloride are placed in a solution containing calcium chloride, and the calcium carbonate is rapidly decomposed at 105-175° C. for 1-3 hours, and ammonium chloride is transformed to obtain a mixed gas containing CO2 and NH3, as well as a calcium chloride solution and an insoluble filter residue; the molar ratio of the Ca element in the calcium carbonate filter cake to the Cl element in the ammonium chloride is 1:2-3; the calcium chloride concentration in the solution containing calcium chloride is ≥20wt.%; Alternatively, the calcium carbonate filter cake is mixed with ammonium chloride and calcined at 250-500° C. for 1-3 hours to obtain a mixed gas containing CO2 and NH3 and CaCl2 calcined sand, the calcined sand is dissolved in water and filtered to obtain a calcium chloride solution and an insoluble filter residue; the molar ratio of the Ca element in the calcium carbonate filter cake to the Cl element in the ammonium chloride is 1:2-2.

2.

10. A wet-process phosphoric acid production process for comprehensive utilization of all elements of phosphate rock according to claim 9, characterized in that: The method for producing the obtained calcium chloride solution as a calcium-containing compound comprises: Passing a mixed gas of CO2 and NH3 into the calcium chloride solution to generate calcium carbonate; or, The calcium chloride solution is mixed with a solution containing ammonium sulfate or ammonium sulfate crystals to produce calcium sulfate; the molar ratio of the Ca element in the calcium chloride solution to the S element in the ammonium sulfate calculated on a dry basis is 1:0.8-1.2; or, The calcium chloride solution is mixed with sodium sulfate solid to produce calcium sulfate whiskers, and the calcium sulfate whiskers and a post-reaction liquid are obtained by filtering; Preferably, the reaction liquid is mixed with a calcium chloride solution, the precipitated sodium chloride crystals are filtered, and the obtained filtrate is returned to the calcium sulfate whisker production process for recycling.