WO2006111057A1

WO2006111057A1 - A method for comprehensively using of the raw material in wet-processing phosphorite and producing nano calcium carbonate with high purity and microsphere shape at the same time

Info

Publication number: WO2006111057A1
Application number: PCT/CN2005/002346
Authority: WO
Inventors: Shandong Wu; Zheng Wu
Original assignee: Shandong Wu; Zheng Wu
Priority date: 2005-04-18
Filing date: 2006-01-10
Publication date: 2006-10-26
Also published as: CN1686816A; CN1686816B

Abstract

The present invention provides a method for comprehensively using of the raw material in wet-processing phosphorite and producing nano calcium carbonate with high purity and microsphere shape at the same time, which solves the problems that calcium is abandoned and used acid is not reused in the existing processes. The method comprises: reacting phosphorite with acid to produce a solution containing water soluble Ca2+ ion and phosphate, adding material to the solution obtained to adjust the pH value; then purifying the solution, and adding precipitant into it to produce unitary and pure calcium compound precipitation. Each step of the method is operated in recycle mode, and is well compatible with the existing processes, and can produce many kinds of product at the same time. The method is simple. According to the method, nano calcium carbonate with high purity and microsphere shape, ammonium sulfate and ammonium nitrate can be produced in large scale.

Description

Comprehensive utilization of raw materials for acid phosphate rock

And co-production of high-purity microspheres of nanometer calcium carbonate technical field '

The present invention relates to the comprehensive utilization of phosphate rock and the acid which decomposes phosphate rock, and more particularly to the separation and extraction of calcium from phosphate rock and the secondary use of used acid. . Background technique .

Phosphate rock is a mineral containing calcium, phosphorus and a large amount of impurities, of which about 40-50% of calcium, less than 18% of phosphorus, mainly used as raw materials for the production of phosphorus products, such as phosphoric acid, ammonium phosphate, phosphate fertilizer. Now, the most cost-effective method is to use acid to break down phosphate rock. Typical processes are:

1. The acid hydrolysis equation for the preparation of phosphoric acid by extraction with an organic solvent:

Ca ₅ F(P0 ₄ ) ₃ + 10HC1 = 5CaCl ₂ + 3H ₃ P0 ₄ + HF t (1)

2. The acid hydrolysis equation for preparing ammonium phosphate with sulfuric acid:

Ca ₅ F(P0 ₄ ) ₃ + 5H ₂ S0 ₄ + 10H ₂ O = 5 CaS0 ₄ * 2 H ₂ 0 + 3H ₃ P0 ₄ + HF† (2)

3. The acid hydrolysis equation for preparing ammonium phosphate with nitric acid: .

Ca ₅ F(P0 ₄ )3 + 10HNO ₃ = 5Ca(N0 ₃ ) ₂ + 3H ₃ P0 ₄ + HF t (3) In these prior art, it is desirable to recover phosphorus, but not for calcium. High-efficiency utilization, and the recovery of calcium is very difficult, and the unused raw materials may cause certain harm to the environment. In formula (1), CaCl ₂ after extraction of 3⁄4P0 _{4 is} soluble and can be recovered by adding a suitable precipitant to produce pure calcium compound, but a large amount of water and chloride brought by HC1 brings recovery. Inconvenient; CaS0 ₄ * 2 H ₂ 0 in formula (2) is a mixture containing a large amount of sediment, CaS0 ₄ is insoluble and extremely difficult to purify; in formula (3), the acid solution is a calcium, phosphorus mixed system, calcium Phosphorus can only coexist in an ionic state under strong acid conditions. When the value is greater than 4, CaHP0 ₄ precipitates, and when the pH is greater than 9, there is almost no calcium phosphate in the acid solution. This is also the reason for decomposing the fluorine-containing calcium salt of the acidity, that is, the phosphate rock, with a strong acid. This makes the water-soluble calcium in formula (3) unable to directly react with the ammonium salt containing C0 ₃ ² ' in the ammonium bicarbonate industry, making full use of the calcium and the used acid to make pure calcium carbonate. And the corresponding ammonium salt, and the volatile ammonia increases the nitrogen utilization rate. .

On the other hand, nano-calcium carbonate is widely used due to its excellent properties, and the market demand for various particle size and crystal forms is very large, and the contradiction between supply and demand will become increasingly prominent. SUMMARY OF THE INVENTION

Purpose of the invention

The object of the present invention is to find a simple and effective method for the secondary comprehensive utilization of waste calcium and used acid in the phosphate rock processing industry, and the use of an acid which must be used for decomposing phosphate rock to change the easily volatile ammonia into fixed ammonium. A variety of products can be obtained by selecting different precipitants; the calcium in the phosphate rock powder is made into a pure compound and the high-purity microsphere nano calcium carbonate is produced in parallel. Technical solutions

The surgical solution of the present invention includes the following steps:

(a) reacting phosphate rock with an acid to prepare an acid hydrolyzate containing water-soluble calcium and phosphorus;

(b) adding a substance that adjusts the PH value of the acidolysis solution, and controlling the pH value in the range of 0-12;

(c) purifying the acid hydrolysate;

(d) A precipitant that forms a precipitate of a calcium compound is added to the acid solution. In a preferred embodiment of the present invention, the technical solution adopted by the present invention includes the following steps:

(a) reacting phosphate rock with an acid to prepare an acid hydrolysate containing water-soluble calcium and phosphorus;

Wherein the acid is preferably nitric acid, hydrochloric acid, phosphoric acid or any mixture thereof;

(b) Adding the acid hydrolysis solution to the acid solution obtained in step (a); the pH value of the substance, controlling the pH value in the range of 0-12, preferably pH 2-12, obtaining the solidified water-soluble calcium and phosphorus Acid solution;

(c) purifying the acid hydrolysate obtained in the step (b) to obtain an acid hydrolyzate containing water-soluble calcium, and a separated phosphorus-containing cured product;

(d) A precipitant which forms a precipitate of a calcium compound is added to the acid-soluble solution containing water-soluble calcium obtained in the step (c) to obtain a precipitate of a calcium compound such as calcium sulfate or calcium carbonate. '

The obtained calcium compound is treated to obtain high-purity microsphere nano calcium carbonate with a particle size of 20 nm--500.

In another preferred embodiment of the present invention, the technical solution for preparing a calcium compound precipitate of the present invention can be cyclically co-produced with a conventional acid hydrolysis phosphate method. Detailed description of the invention

In order to achieve the above object of the invention without affecting the preparation of the phosphorus product, the following conditions must be met for the recovery of calcium from the phosphate rock powder. First, calcium has a higher concentration of water solubility, can be purified, and can form a single calcium compound. Precipitation; Second, the existing phosphorus production process has improved; Third, there are a large number of available raw materials or products supported by industrial production processes; Fourth, there are high economic and social benefits.

The first concept of the present invention was developed from equation (3) to analyze how to obtain pure calcium.

The acid hydrolysis solution of the formula (3) is a highly acidic solution in which water-soluble calcium and phosphorus ions coexist, and can be purified by filtration, natural sedimentation, and removal of specific ions by adding a chemical reagent to obtain water-soluble calcium. Purified calcium in the purified acidolysis solution is separated by a precipitant capable of forming a calcium compound precipitate under strong acidic conditions. The added precipitant determines the process product orientation of formula (3). The invention selects a precipitant containing SO/—series, such as H ₂ S0 ₄ , Na ₂ S0 ₄ , K ₂ S0 ₄ , (NH 4 ) ₂ S0 _{4 ,} etc. containing cations such as H+, Na+, K ΝΗ+ _4, etc. It is water-soluble, purifiable, and has a single precipitation of CaS0 ₄ and has good compatibility with the original phosphorus product process.

When the above precipitating agent is reacted with the acid hydrolyzate purified by the formula (3), there are: '

5Ca(N0 ₃ ) ₂ + 3H ₃ P0 ₄ +5 H ₂ S0 ₄ =5 CaSQ ₄ \ + 3H ₃ PO ₄ +10 HN0 ₃ Formula (4) . The reaction can obtain both pure CaS0 ₄ and an acid capable of decomposing phosphate rock, that is, HN0 ₃ is regenerated, and a cyclic reaction is formed with the formula (3), in which the 3⁄4P0 ₄ forms a concomitant. HN0 ₃ forms a circulating medium.

5Ca(N0 ₃ ) ₂ + 3H ₃ P0 ₄ +5Na ₂ S0 ₄ =5 CaS0 ₄ I + 3H ₃ P0 ₄ +10 Na NO ₃ Formula ( 5 )

5Ca(N0 ₃ ) ₂ + 3H ₃ P0 ₄ +5 K ₂ S0 ₄ =5 CaS0 ₄ + 3H ₃ PO ₄ +10 K N0 ₃ (6 )

5Ca(N0 ₃ ) ₂ + 3H ₃ P0 ₄ +5( H4) ₂ S0 ₄ =5 CaS0 ₄ I + 3H ₃ P0 ₄ +10 NH ₄ N0 ₃ (7 ) As can be seen from the above reaction, both can be obtained pure CaS0 ₄ . After the precipitates of the formula (6) and the formula (7) are separated from the CaS0 ₄ precipitate, an extremely excellent ammonium phosphate ammonium nitrate raw material can be obtained, and after the amination, a binary nitrogen-phosphorus compound fertilizer and a ternary nitrogen-phosphorus-potassium compound fertilizer are formed. While Na N0 _{3 of} formula (5) is a good product and has a rich source of raw materials, it is difficult to separate from 3⁄4P0 ₄ .

The H ₃ P0 ₄ in the separation formula (4) is subjected to extraction. Although HN0 ₃ and H ₃ P0 ₄ can enter the compound fertilizer to prepare ammonium phosphate nitrate, but also lose HN0 ₃ at the same time, while the sulfuric acid method prepares the ammonium, there is neither extraction process nor a large amount of HN0 ₃ source, 'this takes The separation problem of 3⁄4P0 ₄ came.

: For this reason, another concept of the present invention is: using different forms of phosphate at different pH values, in the case of containing a large amount of water-soluble Ca ²⁺ , the calcium salt of each form of phosphoric acid has different solubility characteristics, and the acid is controlled. The phosphate content of the solution is such that the water-soluble phosphorus is limited to a certain range so that it does not affect the purity and quantity of the calcium compound, that is, the phosphorus is left in the solid without being decomposed into water-soluble, and Calcium is decomposed into water-soluble, calcium is first recovered, and high-phosphorus solids that have not been decomposed into water-soluble phosphorus are introduced into the process of producing phosphorus products such as ammonium, calcium, and calcium hydrogen phosphate. Although this method reduces the amount of calcium recovered, it has obtained two pure substances, especially pure calcium, which can be combined with the current original production process. Therefore, when the pH value is controlled to 4 or more (as long as the phosphate rock powder is excessively controlled, the pH value can be controlled to be greater than 4), there is the following formula:

PH>4

' Ca ₅ F(P0 ₄ ) ₃ + 4 H 0 ₃ = CaHP0 ₄ I +2 Ca(N0 ₃ ) ₂ + HF t (8)

After the acid hydrolysis of Ca ₅ F(P0 ₄ ) ₃ in the phosphate rock, at pH 4, the free H ₃ P0 _{4 is} less than one ten thousandth. There are only three forms of phosphorus in phosphate rock: Ca ₅ F(P0 ₄ )3 is not decomposed, CaHP0 ₄ is water insoluble, and Ca(H ₂ P0 ₄ ) ₂ is soluble in water, but the solubility is too small, water soluble. It is only 0.5 mol/l, and the rest remains in the solid mixed with various solids of phosphate rock.

After Ca(N0 ₃ ) _{2 of} formula (8) is purified, it reacts with H ₂ S0 ₄ :

2Ca(N0 ₃ ) ₂ + 2 H ₂ S0 ₄ =2 CaS0 ₄ \ + 4 HN0 ₃ (9)

In the cyclic reaction of formula (8) and formula (9), the cyclic reaction HN0 _{3 is} used for the cyclic reaction and the pH value of the acid solution is controlled, which solves the problem that the calcium salt in the formula (2) is insoluble and cannot be purified. At the same time, the separation of calcium and phosphorus of formula (4) and formula (5) is solved. '

In the cyclic reaction of formula (8) and formula (9), a large amount of water-soluble impurities are dissolved, such as Fe ²⁺ , Mg ^{2+ ,} etc., so that the medium nitric acid loses the ability to carry Ca ²⁺ , and then only In the purification process, the pH is increased to 8-9, and almost all of the phosphorus precipitated by CaHP0 ₄ can be separated. After separation, the pH is further increased to 9-12, and almost all impurities other than Ca ²⁺ can be separated. This can be achieved by adding a basic compound such as calcined phosphate rock, lime powder or lime milk to the acid solution. '

In the cyclic reaction of formula (8) and formula (9), Ca(H ₂ P0 ₄ ) ₂ also plays a certain role in media, and has the ability to carry Ca ²⁺ , but its dissolved enthalpy is too small, under strong acid It is also only about 0.5mol/l. Insufficient use is only an auxiliary function. The dominant role is HN0 ₃ , and its concentration can be artificially adjusted to within the range of near saturation. In order to obtain a good purification effect and a practical amount of calcium compound precipitation, the acid concentration is adjusted to control Ca ^{2 . †} in the practical range of 0.5- 8 mol / l, at 2-6 mol / 1 preferred. HN0 ₃ in the formulae - (8) and (9) may also be replaced by a mixed acid of any ratio of HCl or HN0 ₃ and HCl. The amount of acid used in this step-by-step decomposition method and the amount of acid used in the one-step decomposition method are equal in both theoretical analysis and actual 'implementation, except that the same amount of acid brings a very different result.

A third concept of the invention resides in the value of recovering pure calcium, that is, product orientation and source of raw materials. It can be seen in formula (4), formula (5), formula (6), and formula (7) that different precipitants have significant differences in the orientation of the process and product. In the implementation, it must contribute to the original process, and also solve the problem of sufficient source of precipitant. H ₂ S0 ₄ and Na ₂ S0 _{4 are} easily available, and K ₂ S0 ₄ and (N3⁄4) ₂ S04 are relatively difficult to solve, and the recovered pure CaS0 ₄ is not ideal as the product enters the market, and the price and the sales capacity are not satisfactory. On the other hand, the ammonium salt of carbonate is both purified and industrially supported. Because the ammonia contained therein is easily volatilized and reduces the nitrogen use rate, it can be used to form a mutually supporting cycle process with CaS0 ₄ , as shown in the following formula:

CaS0 ₄ + (NH ₄ ) ₂ C0 ₃ = ( H ₄ ) ₂ S0 ₄ + CaC0 ₃ \ (10)

(NH ₄ ) ₂ S0 ₄ (liquid) + 2KC1 (solid) = K ₂ S0 ₄ (solid) + 2NH ₄ C1 (liquid) Formula (11) Thus, formula ₍₆₎ and formula ₍₁₀₎ , formula (11) A recycling process is formed to provide raw materials that are mutually desirable. All processes for producing CaS0 ₄ can produce high-purity microsphere calcium carbonate and high-quality standard nitrogen fertilizer ammonium sulfate with formula (10). Formulas (7) and (10) form a recycling process, and also provide mutually needed raw materials. Sulfate acts as a circulating medium in these cycles, allowing large amounts of calcium and volatile ammonia to be obtained in high value product forms. Both formula (10) and formula (11) are current industrial production processes, and (NH ₄ ) ₂ C0 ₃ and ammonium salts containing CO can be largely derived from the current synthetic ammonia process.

Thus, the present invention accomplishes the following overall response:

Ca ₅ F(P0 ₄ ) ₃ + 5H ₂ S0 ₄ +5(NH ₄ ) ₂ C0 ₃ =5 CaC0 ₃ I +5(NH ₄ ) ₂ S0 ₄ +3H ₃ P0 ₄ + HF

Ca ₅ F(P0 ₄ ) ₃ +10 HN0 ₃ +5(NH ₄ ) ₂ C0 ₃ =5 CaC0 ₃ +10 NH ₄ N0 ₃ +3H ₃ P0 ₄ + HF† The reaction temperature of the formula (10) in the current process For 60-70 ° C, in order to obtain nano-scale calcium carbonate, the temperature can be lowered to below 30 ° C. The purity and whiteness are determined by the raw materials, and the microsphere type is a characteristic crystal form under the raw material conditions of the process. Calcium carbonates of various particle sizes have their uses, and this process will show great commercial value and far-reaching social benefits. 'Industrial applicability

When the invention is used in the process of preparing ammonium phosphate and phosphate fertilizer by the current sulfuric acid method, the process equipment for extracting phosphoric acid is not used in the process, and the large amount of HC1 and HN0 ₃ required for forming water-soluble calcium are not used, and only the stepwise decomposition method can be adopted. . Recycling partially purified calcium by cyclic acid hydrolysis of formula (8) and formula (9), the essence of which is acid pretreatment of phosphate rock, the calcium content of phosphate rock after pickling is greatly reduced, and phosphorus content Significantly improved, the improvement of the ammonium phosphate process is: Separation of almost all Mg ²⁺ and some Fe ²⁺ , Al ³⁺ impurities, because the ammonium phosphate process avoids chlorine, only HN0 ₃ can be used as the circulating medium. The nitrates entrained in the phosphate rock after pickling can significantly improve the phosphogypsum Crystallization, and greatly reduce the amount of slag discharged from phosphogypsum. The calcium phosphate and calcium hydrogen phosphate processes provide extremely excellent phosphate rock raw materials, which can significantly improve product quality. : . . ;

When the present invention for the existing process ammonium phosphate nitrate, because of its material advantages superior ΉΝ0 _3, of formula (6), the formula (7) has clearly expressed embodiment recovering pure calcium. The invention has the following help in the process: In the ammonium phosphate, due to the influence of no Ca ²⁺ , the total nutrient content and the water solubility of phosphorus can be greatly improved, especially the ammonium nitrogen is increased, and the nitrogen fertilizer is adsorbed in the soil. Increase, reduce loss, use better, and eliminate the freezing process.

In particular, the treatment of phosphate rock by the step-by-step decomposition method has unique advantages for the ammonium phosphate ammonium nitrate process: for the acid hydrolysis solution after decalcification of formula (8), adjusting the ffl value 8-9 to separate CaHP0 ₄ , CaF ₂ and After the iron and aluminum impurities are adjusted, the PH value is 9-12, and Mg(0H) _{2 is} separated to obtain the calcium hydrogen phosphate fertilizer mainly composed of CaHP0 ₄ , wherein the effective phosphorus is not easily fixed by iron and aluminum to reduce the fertilizer efficiency. A purer Mg (0H) ₂ can be obtained. This method is especially suitable for the development and utilization of high-iron, high-magnesium and low-grade phosphate rock.

The purified Ca(N0 ₃ ) ₂ can form a series of high-quality nitrates, which react with K ₂ S0 ₄ , (NH ₄ ) ₂ S0 ₄ , Na ₂ S0 ₄ , (N ) 2C0 ₃ , NH ₄ HC 0 ₃ , respectively. Two products, K N0 ₃ and CaS0 ₄ , NH ₄ N0 ₃ and CaS0 ₄ , Na N0 ₃ and CaS0 ₄ , N3⁄4 N0 ₃ and CaC0 ₃ , NH ₄ N0 ₃ , C0 ₂ and CaC0 ₃ . Under the conditions, the precipitant containing C0 ₃ ² - has great advantages, the process is simple, the product is pure, the reactant concentration is high, the investment is small, the effect is quick, and the original process can greatly reduce the load of the freezing process. Or save the freezing process. . 'Benefit effect

The beneficial effects of the invention: 1. Further utilizing the raw materials used for preparing the phosphorus product of the acid phosphate rock to prepare a plurality of pure products. 2. The invention has good compatibility with the current technology, and not only can co-produce many products, the development scale can be large or small, and the new process is simple and easy. 3. The process steps of the present invention adopt a recycling process, and there is no pollution of three wastes. 4. The invention can produce high-quality calcium carbonate, ammonium sulfate and ammonium nitrate in large quantities, especially to obtain high-purity, micro-sphere, nano-scale calcium carbonate, which not only provides market demand, but also has good economic, social and social benefits. . .

Figure 1 is a process flow diagram for preparing decalcified phosphate rock and pure calcium sulfate.

Figure 2 is a process flow diagram for the full recovery of calcium, phosphorus and acid from decalcified phosphate rock.

Figure 3 is a flow chart showing the process of producing high-purity microsphere nano-calcium carbonate from the separated high-purity calcium sulfate. BEST MODE FOR CARRYING OUT THE INVENTION

The invention is further illustrated below in conjunction with specific embodiments. It is to be understood that the examples are merely illustrative of the invention and are not intended to limit the scope of the invention. The methods in the following examples which do not specify the specific conditions are usually in accordance with conventional conditions. Or according to the conditions recommended by the manufacturer. Proportions and percentages are based on weight, unless Don't explain. Example 1 Preparation of Decalcified Phosphate Rock and Pure Calcium Sulfate

Process steps:

1. A nitric acid solution lm ^{3 having a} concentration of 5. mol/l was placed in an acid hydrolysis tank containing 500 kg of phosphate rock powder (containing P ₂ O ₅ 30%).

Prepare 9 mol/l of sulfuric acid into a dilute acid tank for use as a regenerative precipitant.

2. Adjust the pH value between 4 and 7 with phosphate rock under intermittent stirring, react for 0.5 hour, and stand still for 0.5 hour. The acid solution was sampled and analyzed, containing Ca ²⁺ 3m ₀ l/l.

3. The clear solution is filtered to clear and transparent into the Ca ²⁺ clear solution tank.

4. Take 200L of the clear solution and wash the CaS0 ₄ precipitate, then add 20-30 kg of water to wash, and combine all the washing liquid into the regeneration reaction tank. The washed CaS0 _{4 is} sent to the clean container for stock use. (For the first time, it can be washed without CaS0 ₄ precipitation, 200L of clear liquid is directly sent to the regeneration reaction tank)

60 L of 9 mol/l of dilute sulfuric acid was added to the regeneration reaction tank, and the reaction was carried out for 1 hour with intermittent stirring to form a large amount of white CaS0 ₄ precipitate. When the reaction time was long, the precipitated particle size was large. (Ca ²⁺ excess 5-10% to reduce SO)

5. The solid-liquid mixture in the regeneration reaction tank is sent to a solid-liquid separation suction filter tank for filtration, and the filtrate is regenerated acid and sent to the acid hydrolysis tank. '

6. Return to step 4. Return to step 2 when the Ca ²⁺ containing solution is used up.

Note: Recycled when the circulating acid solution contains Mg ²⁺ greater than 1 mol/1.

When the decalcified phosphate rock after pickling contains P ₂ 0 ₅ about 45%, the solid matter is taken out from the acid hydrolysis tank and filtered to a water content of about 25%. The molar ratio of nitrate nitrogen to 1.2%, Ca046%, . Ca ²⁺ /P0 ₄ ^3- was 1.3.

This embodiment has a particularly good effect on the treatment of high-iron and high-magnesium phosphate rock. Most of the iron and magnesium impurities enter the acid hydrolysis solution, and the pH value is mentioned to about 8 with lime milk, and CaHP0 ₄ and iron can be separated, and then PH The value mentions 12, Mg ²⁺ will precipitate completely, and the acid solution is pure Ca ²⁺ containing solution. Example 2 Full recovery of calcium, phosphorus and acid from decalcified phosphate rock

Process steps:

1. Take 120kg of wet decalcified phosphate rock (about 100kg dry basis) plus 40% HNO ₃ 130kg, put it into acid hydrolysis tank for 0.5 hour, and let it settle naturally for 1-2 hours.

2. Filter all the acid solution, filter it to clear and transparent, and obtain about 245kg of clear liquid. The filter residue is washed into the clear liquid with 5kg of clear water and the total weight is about 250kg.

3. Further filter into a colorless transparent square JiA reactor. 60% of (NH ₄ ) ₂ SO ₄ 180 kg (pH ₃ ^1 was previously adjusted) was added to the reactor to form a viscous CaS0 ₄ precipitate, which was repeatedly stirred and allowed to stand for 1 to 2 hours.

4. The product is transferred into a vacuum suction filter box for solid-liquid separation, and 100 kg of fresh water is added for washing three times. Put The strongly acidic filtrate and washing liquid were combined to about 380 kg, and sent to an evaporation process to be ammoniated and dried.

: 5, the CaS0 ₄ precipitate after washing is about 25% water, the total weight is 1.50kg, put it into a clean container for use. 6. 1 kg of the filtrate was ammoniated to pH 7 with NH ₄ HC0 ₃ , and stood still for 0.5 hour. The liquid had a small amount of turbidity, which was a precipitate of CaHP0 ₄ , and evaporated to dryness to obtain a mixture of NH ₄ N 0 ₃ and ammonium phosphate of about 0.4 kg.

(Note: By adding K ₂ S0 ₄ in step 3, N-P-K ternary compound fertilizer can be obtained.)

Analysis results: P ₂ O ₅ 30%, N28% (ammonium nitrogen 19%, nitrate nitrogen 9%), PH-8-9 after water dissolution, a small amount of ammonia, Ν0 ₃ 7Ρ0 ₄ ² · molar ratio 1.5. This indicates that about 20% of calcium is dissolved in the acid solution of step 2 in the form of Ca(H ₂ P0 ₄ ) ₂ and a near-saturated concentration, which is an economical saving of about 20%. The step of forming a high water-soluble phosphorus. Because of the calcium-free content of total ammonium, the total nutrient is greatly increased by about 50%. Example 3 Preparation of High Purity Microspheres Nano Calcium Carbonate with Separated High Purity Calcium Sulfate

Process steps: .

1. Take CaS0 ₄ 13.6kg (dry basis) into the reactor.

2. Stir the reaction until the volatile ammonia is less than 0.1 mol/l. After the static layering, take the upper supernatant and send it to the evaporation process. This is a more complete (NH ₄ ) ₂ S0 ₄ solution. (First time no reaction solution, omit this step).

3. Add 9.6kg of carbonized solution containing pure (NH ₄ ) ₂ C0 ₃ to the reactor (also can be replaced by 16kg of NH ₄ HC0 ₃ , but add 1.5 times of the calculated amount for the first time, and add ammonium sulfate solution, at least soak All solid).

4, at a temperature of 0- 30 ^Q C, the reaction was stirred for 2 ~ hours, solid-liquid separator for separating into CaC0 _3, 20kg of water was added, washed in three to five times CaC0 _3, washed until substantially no ammonia odor, and then sent Dry the oven. The filtrate and the washing liquid are combined and sent to the reactor, and the filtrate contains about 50% of the unreacted carbonizing solution.

5. Return to step 1.

After drying, CaC0 _{3 :} 10kg, powdery, non-caking, purity greater than 98%, whiteness greater than 98%, microsphere type, uniform particle size and less than '100 nm.

Claims

Rights request

1. A method for comprehensive utilization of raw materials for acid hydrolysis of phosphate rock and co-production of pure microsphere nano calcium carbonate, comprising the following steps:

(c) purifying the acid hydrolysate;

(d) A precipitant which forms a precipitate of a calcium compound is added to the acid solution.

2. The method of claim 1 wherein said pH is from 2 to 12.

3. The method of claim 1 wherein the acid comprises nitric acid, hydrochloric acid, phosphoric acid or any mixture thereof.

4. The method according to claim 1, wherein said substance for adjusting the pH of the acid-dissolving solution is a calcium-containing compound; and said precipitating agent is water-soluble containing S0 ₄ ² - or containing C0 ₃ ² - Sex compounds.

The method for comprehensively utilizing raw materials for acid-smelting phosphate rock and co-producing high-purity microsphere nano-calcium carbonate according to claim 2, wherein the calcium-containing compound is phosphate rock or lime milk; water-soluble compound is S0 ₄ ² _ _{_{_{¾S0 4, K 2 S0 4,}}} (NH 4) 2 S0 4, Na 2 S0 4, the containing C0 ₃ ² 'water-soluble compounds containing C0 ₃ ^2' ammonium salt.