CN108796612B - Method for preparing calcium sulfate whisker and co-producing ammonium sulfate by phosphogypsum cyclic decomposition - Google Patents
Method for preparing calcium sulfate whisker and co-producing ammonium sulfate by phosphogypsum cyclic decomposition Download PDFInfo
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Abstract
The invention discloses a method for preparing calcium sulfate whisker and co-producing ammonium sulfate by phosphogypsum cyclic decomposition, which specifically comprises the following steps: (a) Phosphogypsum is subjected to sulfuric acid reaction to remove impurities, then water is added to carry out slurry mixing, the phosphogypsum enters a phase inversion tank, and the phosphogypsum reacts with the ammonium carbonate mixed solution and is filtered to obtain ammonium sulfate solution I and calcium carbonate slag I; (b) Adding nitric acid into the calcium slag I for decomposition, and filtering to obtain silicon slag II and calcium nitrate filtrate II; (c) Reacting the calcium nitrate filtrate II with sulfuric acid, cooling for crystallization, filtering to obtain a filtrate III and a filter cake III, washing and drying the filter cake III to obtain calcium sulfate whiskers, and recycling acidolysis calcium slag from the filtrate III; (d) Neutralizing the ammonium sulfate filtrate with sulfuric acid until the pH value is 4.5-5.8, concentrating in vacuum, cooling, crystallizing and drying to obtain ammonium sulfate. The invention realizes the graded comprehensive utilization of sulfur, calcium, silicon and the like in phosphogypsum at a lower temperature without high temperature, and has lower energy consumption; the recycling of byproducts is realized, secondary pollution is not generated, and the environment-friendly effect is better; the obtained product ammonium sulfate and calcium sulfate has higher purity, wider application field and higher economic value.
Description
Technical Field
The invention belongs to the technical field of comprehensive utilization of phosphogypsum, and in particular relates to a method for preparing calcium sulfate whisker byproduct ammonium sulfate by using phosphogypsum, ammonia water, nitric acid and sulfuric acid as raw materials through cyclic decomposition.
Background
Phosphogypsum is a main byproduct of phosphoric acid by a wet method of a sulfuric acid method, and the main component of phosphogypsum is CaSO 4 2H 2 O, and generally contains 8-15% of SiO 2, free acid, metal ions, fluoride and the like, so that the phosphogypsum has a large number of impurity types and is difficult to treat. About 4.5 to 5.5 tons of phosphogypsum are produced per 1 ton of phosphoric acid on average, and about 2 to 3 hundred million tons are discharged every year worldwide. The phosphorus chemical industry in China discharges about 5000 ten thousand tons of phosphogypsum per year, and the annual growth rate is still 15 percent. Because of the huge amount of phosphogypsum produced and the limitation of the market capacity of phosphogypsum comprehensive utilization products (the utilization rate is less than 5%), most of phosphogypsum production enterprises mainly stack the phosphogypsum, which wastes precious calcium and sulfur resources and causes serious pollution to the surface environment and underground water systems, and the comprehensive utilization of phosphogypsum waste residues is urgent from the aspects of environment and technical safety.
In the prior art, most phosphogypsum is mainly used for producing construction materials such as sulfuric acid, cement, gypsum boards, sustained release agents and the like, and also is partially used for producing potassium sulfate (including wet process and thermal process), but is not popularized in industry due to the limitations of raw material cost, energy consumption and the like; and part of the factory household phosphogypsum is used for preparing ammonium sulfate, but the byproduct calcium carbonate is also provided with more silicon dioxide and acid insoluble matters, so that the quality of the calcium carbonate is not high, the application range is narrow, and the economic value is low. In order to further utilize the calcium carbonate slag, new process researches are carried out successively, and the method is mainly used for preparing high-activity calcium carbonate products, for example, patent CN 103524057A discloses a method for preparing ammonium sulfate by-product calcium carbonate from phosphogypsum as a raw material, spraying coal dust and air into a decomposing furnace, and heating and decomposing the mixture at the high temperature of 1200 ℃ to obtain lime. Liu Jian (Liu Jian, etc. nitric acid is used for leaching phosphogypsum calcium slag to prepare high-quality light calcium carbonate [ J ]. Environmental chemistry, 2010, 29 (4): 772-773), and the calcium slag is decomposed by nitric acid to obtain calcium nitrate, and then carbon dioxide is introduced to prepare the calcium carbonate. Meng Tiehong et al (Meng Tiehong et al. Process for preparing light calcium carbonate from phosphogypsum calcium slag. Research on the preparation of light calcium carbonate from phosphogypsum calcium slag [ J ]. Chemical minerals and processing, 2014, 08:9-12.), the method has the advantages of high energy consumption by calcining the phosphogypsum at high temperature to obtain calcium oxide, adding water to obtain calcium hydroxide, and introducing carbon dioxide to prepare calcium carbonate.
The calcium sulfate whisker is a fine short fiber, and has the characteristics of high strength, high toughness, high modulus, high temperature resistance, wear resistance, corrosion resistance and easy surface treatment, thus having wide application in industries such as paper making, rubber, plastics, asphalt, adhesives and the like. At present, the production of the calcium sulfate whisker mainly comprises an ordinary pressure acidification method and a hydrothermal reaction method, and the hydrothermal method is more studied but is limited by higher reaction temperature and pressure, so that industrialization is not realized at present. The normal pressure acidification method generally obtains the calcium sulfate whisker through acid dissolution and cold crystallization. For example, patent CN 104005086B discloses a method for preparing calcium sulfate whisker by dissolving phosphogypsum with hydrochloric acid, but the liquid-solid ratio of hydrochloric acid solution and calcium sulfate is larger, and the power consumption is higher. Cui Yishun (Cui Yishun. Study of phosphogypsum to prepare calcium sulfate whisker [ J ]. Inorganic salt industry, 2010, 42 (9): 49-50.) calcium sulfate whisker with average length-diameter ratio of 95 was prepared from sulfuric acid and phosphogypsum as raw materials, but the yield, purity and whiteness of the calcium sulfate whisker were lower, wherein the whiteness was 65.8%, the purity was 93.6l%, and the yield was 31.36%.
Disclosure of Invention
In order to solve the problems of high energy consumption, low purity of byproducts, low product value and the like in the phosphogypsum treatment process by the method, the invention aims to provide a method for preparing calcium sulfate whisker and ammonium sulfate with high purity and length-diameter ratio by low-temperature cyclic decomposition of phosphogypsum.
The technical scheme of the invention is that the method for preparing calcium sulfate whisker and co-producing ammonium sulfate by phosphogypsum cyclic decomposition comprises the following steps:
(a) Phase inversion procedure: phosphogypsum reacts with dilute sulfuric acid to remove impurities, filtering, washing to be neutral, then, adding water into a phase inversion tank to carry out slurry mixing, introducing ammonia water to absorb ammonium carbonate salt solution after tail gas of acidolysis procedure, carrying out phase inversion reaction, and filtering to obtain ammonium sulfate solution I and coarse calcium carbonate slag I;
(b) Acidolysis process: adding nitric acid into the coarse calcium carbonate I for acidolysis, and filtering to obtain slag II and calcium nitrate filtrate II; removing the slag II to produce cement, wherein the calcium nitrate filtrate is used for preparing calcium sulfate whiskers, and the tail gas is removed from ammonia water to be absorbed for decomposing phosphogypsum;
(c) Whisker preparation process: adding sulfuric acid into the calcium nitrate filtrate II, reacting, cooling, crystallizing and filtering to obtain a filter cake III and a filtrate III; washing and drying the filter cake III to obtain calcium sulfate whisker, and returning the filtrate III to the acidolysis process (b) for circularly decomposing the calcium carbonate slag I;
(d) Ammonium sulfate process: and adding sulfuric acid into the ammonium sulfate filtrate I to neutralize and adjust the pH to 4.5-5.8, then removing vacuum concentration crystallization and drying to obtain an ammonium sulfate finished product, and performing slurry mixing and washing in the condensed water phase-removal conversion process.
Further, in the phase conversion process, the mass ratio of phosphogypsum to total ammonia is 2.7-3.05: 1, the reaction temperature is 50-70 ℃, the stirring speed is 200-250 r/min, and the reaction time is 1.5-2.5 h.
3. The method for preparing calcium sulfate whisker and co-producing ammonium sulfate by phosphogypsum cyclic decomposition according to claim 1, which is characterized by comprising the following steps: in the acidolysis process, firstly adding water into the calcium carbonate slag I for pulping, then slowly adding nitric acid with the concentration of 40-60% for reaction, and controlling the mass ratio of the nitric acid to the calcium to be 2.0-2.05: 1, the reaction temperature is 70-80 ℃, the stirring speed is 250-300 r/min, and after 1.0-1.5 h of reaction, the calcium nitrate filtrate II and filter residue II are obtained by filtering.
Further, in the whisker preparation process, (1) sulfuric acid and calcium nitrate filtrate are simultaneously added into a reaction tank, and the mass ratio of the sulfuric acid to the calcium nitrate filtrate is 0.95-1.05: 1, a step of;
(2) The reaction temperature of sulfuric acid and the calcium-containing filtrate is 80-95 ℃, the stirring speed is 200r/min, and the reaction time is 1.0-1.5 h;
(3) Cooling and crystallizing the reaction feed liquid at 25-35 ℃ to 1.5-2.0 h, filtering to obtain a filter cake and mother liquor, washing and drying the filter cake III to obtain calcium sulfate whisker, mixing the filtrate III with washing water, adding concentrated nitric acid to adjust the concentration to 50-60%, and then circularly decomposing calcium carbonate slag II through an acidolysis procedure.
Further, the purity of the calcium sulfate whisker obtained in the whisker process is more than or equal to 98%, the length-diameter ratio is more than or equal to 45, and the whiteness is more than or equal to 95%;
and further, adding 40-60% sulfuric acid into the filtrate obtained in the phase conversion step to adjust the pH of the solution to 4.5-5.5, then sending the solution to vacuum concentration to the concentration of 1.35-1.36 g/ml, cooling, crystallizing and filtering at 58-60 ℃ to obtain ammonium sulfate crystals, and drying the crystals at 110-120 ℃ to obtain an ammonium sulfate product, wherein the N content of the obtained ammonium sulfate product is more than or equal to 21.0%.
The invention has the following advantages:
(1) The invention does not need high temperature condition, realizes the graded comprehensive utilization of phosphogypsum sulfur, calcium, silicon and the like at lower temperature, and has lower energy consumption;
(2) The tail gas carbon dioxide of the calcium carbonate absorption process by utilizing liquid ammonia is used for circularly decomposing phosphogypsum, the whisker filtrate is used for circularly decomposing calcium carbonate, and the condensed water of the ammonium sulfate process is used for washing and pulping phosphogypsum, so that the cyclic utilization of industrial three wastes is realized, secondary pollution is not generated, and the environment-friendly performance is good;
(3) The product obtained by decomposing phosphogypsum by adopting the method disclosed by the invention is an ammonium sulfate and calcium sulfate product with higher purity, wider application field and higher economic value.
DETAILED DESCRIPTION OF EMBODIMENT (S) OF INVENTION
Example 1
Adding sulfuric acid with the concentration of 30% and phosphogypsum into a pretreatment tank, reacting at the temperature of 50 ℃ and the stirring speed of 200r/min for 1.0 h, filtering, adding water into a filter cake for washing to be neutral, and conveying the filter cake to a phase inversion tank by a belt; the mass ratio of phosphogypsum to total ammonia is 2.95: adding a mixed solution of ammonia water and ammonium bicarbonate into a phase inversion tank, controlling the reaction temperature to be 70 ℃, reacting for 2.0 hours under the stirring condition of 200r/min, filtering to obtain ammonium sulfate filtrate I and calcium carbonate slag I, adding water into the calcium carbonate slag I, pulping, then entering an acidolysis tank, adding 40% sulfuric acid into the ammonium sulfate filtrate to adjust the pH value to be 5.0, then entering a vacuum concentration system to concentrate the ammonium sulfate filtrate until the concentration of slurry is 1.355g/L, cooling and crystallizing the slurry at 60 ℃, centrifugally separating the slurry to obtain ammonium sulfate crystals, and drying the crystals at 115 ℃ to obtain ammonium sulfate, wherein the N content of the obtained ammonium sulfate is 21.05%; the ratio of the amounts of nitric acid to calcium carbonate was 2.05:1, adding calcium carbonate slag slurry and 50% nitric acid into an acidolysis tank, controlling the reaction temperature to be 70 ℃, reacting for 1.0 hour at the stirring speed of 250 r/min, filtering to obtain calcium nitrate filtrate II and silicon slag II, preparing cement by the silicon slag, utilizing the calcium nitrate filtrate II in the next whisker procedure, and absorbing tail gas by 25% ammonia water; the ratio of the amounts of the substances is n (H 2SO4：Ca2+) =1.05: adding sulfuric acid with the concentration of 50% and calcium nitrate filtrate into a whisker reaction tank at the same time, controlling the temperature of the reaction feed liquid to be 80 ℃, stirring at the speed of 200r/min, allowing the reaction feed liquid to enter a crystallization tank after reacting 1.5 h, cooling and crystallizing 2.0 h at the temperature of 25 ℃, filtering and washing to obtain a filter cake III and a mother liquor III, washing the filter cake III with hot water at the temperature of 70-80 ℃, drying to obtain calcium sulfate whiskers, mixing the filtrate and washing water to obtain the mother liquor III, and delivering the mother liquor III to an acidolysis procedure to circularly decompose coarse calcium carbonate. The obtained calcium sulfate whisker has an aspect ratio of 48, a purity of 98.5% and a whiteness of 95.
Example 2
Example 2 is similar to example 1, except that in the phase inversion process, the ammonia and ammonium bicarbonate solution added in the phase inversion tank is obtained by absorbing the tail gas of the acidolysis process with 25% ammonia water, and the mass ratio of phosphogypsum to total ammonia is 3:1, a step of; in the acidolysis procedure, the added acid is mother liquor (or filtrate) obtained after preparing the calcium sulfate whisker in example 1, wherein the acid concentration is 55%; in the whisker preparation process, the concentration of sulfuric acid added is 40%, and the mass ratio of sulfuric acid to calcium nitrate is n (H 2SO4：Ca2+) =1.0: 1, cooling, crystallizing and filtering the reaction liquid to obtain calcium sulfate whisker, and washing the whisker with water at 25 ℃. By adopting the conditions, the obtained calcium sulfate whisker has the length-diameter ratio of 40, the purity of 97.5 percent and the whiteness of 95 percent.
Example 3
Adding sulfuric acid with the concentration of 40% and phosphogypsum into a pretreatment tank, reacting at the temperature of 40 ℃ and the stirring speed of 200r/min for 1.5 h, filtering, washing a filter cake to be neutral, and conveying to a phase inversion tank through a belt; the mass ratio of phosphogypsum to total ammonia is 3.05: adding a mixed solution of ammonia water and ammonium bicarbonate into a phase inversion tank, controlling the reaction temperature to be 60 ℃, reacting for 2.0 hours under the stirring condition of 250 r/min, filtering to obtain ammonium sulfate filtrate I and calcium carbonate slag I, adding water into the calcium carbonate slag I, pulping, then entering an acidolysis tank, adding 60% sulfuric acid into the ammonium sulfate filtrate to adjust the pH value to be 4.5, then entering a vacuum concentration system to concentrate until the concentration of slurry is 1.360g/L, cooling and crystallizing the slurry at 58 ℃, centrifugally separating to obtain ammonium sulfate crystals, and drying the crystals at 120 ℃ to obtain ammonium sulfate, wherein the N content of the obtained ammonium sulfate is 21.12%; the ratio of the amounts of nitric acid to calcium carbonate was 2.0:1, adding calcium carbonate slag slurry and 45% nitric acid into an acidolysis tank, controlling the reaction temperature to be 80 ℃, reacting for 1.5 hours at the stirring speed of 250 r/min, filtering to obtain calcium nitrate filtrate II and silicon slag II, preparing cement by the silicon slag, utilizing the calcium nitrate filtrate II in the next whisker procedure, and absorbing tail gas by 20% ammonia water; the ratio of the amounts of the substances is n (H 2SO4：Ca2+) =0.95: adding sulfuric acid with the concentration of 40% and calcium nitrate filtrate into a whisker reaction tank at the same time, controlling the temperature of the reaction feed liquid to be 95 ℃, stirring at the speed of 200r/min, allowing the reaction feed liquid to enter a crystallization tank after reacting 1.0 h, cooling and crystallizing 1.5: 1.5 h at the temperature of 35 ℃, filtering and washing to obtain a filter cake III and a mother liquor III, washing the filter cake III with hot water at the temperature of 70-80 ℃, drying to obtain calcium sulfate whiskers, mixing the filtrate and washing water to obtain the mother liquor III, and delivering the mother liquor III to an acidolysis procedure to circularly decompose coarse calcium carbonate. The obtained calcium sulfate whisker has an aspect ratio of 45, a purity of 98.8% and a whiteness of 97.
Example 4
Adding sulfuric acid with the concentration of 40% and phosphogypsum into a pretreatment tank, reacting at 42-45 ℃ and stirring at the speed of 200r/min for 1.5 h, filtering, washing a filter cake to be neutral, and conveying to a phase inversion tank through a belt; the mass ratio of phosphogypsum to total ammonia is 2.7: adding a mixed solution of ammonia water and ammonium bicarbonate into a phase inversion tank, controlling the reaction temperature to be 70 ℃, reacting for 2.0 hours under the stirring condition of 250 r/min, filtering to obtain ammonium sulfate filtrate I and calcium carbonate slag I, adding water into the calcium carbonate slag I, pulping, then entering an acidolysis tank, adding 60% sulfuric acid into the ammonium sulfate filtrate to adjust the pH value to 5.6, then entering a vacuum concentration system to concentrate the ammonium sulfate filtrate to the concentration of 1.360g/L, cooling and crystallizing the slurry at 58 ℃, centrifugally separating to obtain ammonium sulfate crystals, and drying the crystals at 120 ℃ to obtain ammonium sulfate, wherein the N content of the obtained ammonium sulfate is 21.24%; the ratio of the amounts of nitric acid to calcium carbonate was 2.0:1, adding calcium carbonate slag slurry and 45% nitric acid into an acidolysis tank, controlling the reaction temperature to be 75 ℃, reacting for 1.5 hours at the stirring speed of 250 r/min, filtering to obtain calcium nitrate filtrate II and silicon slag II, preparing cement by the silicon slag, utilizing the calcium nitrate filtrate II in the next whisker procedure, and absorbing tail gas by 20% ammonia water; the ratio of the amounts of the substances is n (H 2SO4：Ca2+) =0.95: adding sulfuric acid with the concentration of 40% and calcium nitrate filtrate into a whisker reaction tank at the same time, controlling the temperature of the reaction feed liquid to be 95 ℃, stirring at the speed of 200r/min, allowing the reaction feed liquid to enter a crystallization tank after reacting 1.0 h, cooling and crystallizing 1.5: 1.5 h at the temperature of 35 ℃, filtering and washing to obtain a filter cake III and a mother liquor III, washing the filter cake III with hot water at the temperature of 70-80 ℃, drying to obtain calcium sulfate whiskers, mixing the filtrate and washing water to obtain the mother liquor III, and delivering the mother liquor III to an acidolysis procedure to circularly decompose coarse calcium carbonate. The obtained calcium sulfate whisker has an aspect ratio of 44, a purity of 98.2% and a whiteness of 97.
Example 5
Adding sulfuric acid with the concentration of 40% and phosphogypsum into a pretreatment tank, reacting at 50 ℃ and stirring at the speed of 200r/min for 1 h, filtering, washing a filter cake to be neutral, and conveying to a phase inversion tank through a belt; the mass ratio of phosphogypsum to total ammonia is 2.80: adding a mixed solution of ammonia water and ammonium bicarbonate into a phase inversion tank, controlling the reaction temperature to be 70 ℃, reacting for 1.5 hours under the stirring condition of 250 r/min, filtering to obtain ammonium sulfate filtrate I and calcium carbonate slag I, adding water into the calcium carbonate slag I, pulping, then entering an acidolysis tank, adding 60% sulfuric acid into the ammonium sulfate filtrate to adjust the pH value to 5.8, then entering a vacuum concentration system to concentrate the ammonium sulfate filtrate to the concentration of 1.360g/L, cooling and crystallizing the slurry at 58 ℃, centrifuging the slurry to obtain ammonium sulfate crystals, and drying the crystals at 120 ℃ to obtain ammonium sulfate, wherein the N content of the obtained ammonium sulfate is 21.34%; the ratio of the amounts of nitric acid to calcium carbonate was 2.0:1, adding calcium carbonate slag slurry and 45% nitric acid into an acidolysis tank, controlling the reaction temperature to be 80 ℃, reacting for 1 hour at the stirring speed of 250 r/min, filtering to obtain calcium nitrate filtrate II and silicon slag II, preparing cement by the silicon slag, utilizing the calcium nitrate filtrate II in the next whisker procedure, and absorbing tail gas by 20% ammonia water; the ratio of the amounts of the substances is n (H 2SO4：Ca2+) =0.95: adding sulfuric acid with the concentration of 40% and calcium nitrate filtrate into a whisker reaction tank at the same time, controlling the temperature of the reaction feed liquid to be 95 ℃, stirring at the speed of 200r/min, allowing the reaction feed liquid to enter a crystallization tank after reacting 1.0 h, cooling and crystallizing 1.5: 1.5 h at the temperature of 35 ℃, filtering and washing to obtain a filter cake III and a mother liquor III, washing the filter cake III with hot water at the temperature of 70-80 ℃, drying to obtain calcium sulfate whiskers, mixing the filtrate and washing water to obtain the mother liquor III, and delivering the mother liquor III to an acidolysis procedure to circularly decompose coarse calcium carbonate. The obtained calcium sulfate whisker has an aspect ratio of 46, a purity of 98.9% and a whiteness of 97.
Example 6
Adding sulfuric acid with the concentration of 40% and phosphogypsum into a pretreatment tank, reacting at the temperature of 50 ℃ and the stirring speed of 200r/min for 1.5 h, filtering, washing a filter cake to be neutral, and conveying to a phase inversion tank through a belt; the mass ratio of phosphogypsum to total ammonia is 2.80: adding a mixed solution of ammonia water and ammonium bicarbonate into a phase inversion tank, controlling the reaction temperature to be 70 ℃, reacting for 2 hours under the stirring condition of 250 r/min, filtering to obtain ammonium sulfate filtrate I and calcium carbonate slag I, adding water into the calcium carbonate slag I to carry out slurry mixing, then entering an acidolysis tank, adding 60% sulfuric acid into the ammonium sulfate filtrate to adjust the pH value to be 5.6, then entering a vacuum concentration system to concentrate the ammonium sulfate filtrate to the concentration of 1.360g/L, cooling and crystallizing the slurry at 58 ℃, centrifugally separating the slurry to obtain ammonium sulfate crystals, and drying the crystals at 120 ℃ to obtain ammonium sulfate, wherein the N content of the obtained ammonium sulfate is 21.5%; the ratio of the amounts of nitric acid to calcium carbonate was 2.0:1, adding calcium carbonate slag slurry and 45% nitric acid into an acidolysis tank, controlling the reaction temperature to be 80 ℃, reacting for 1 hour at the stirring speed of 250 r/min, filtering to obtain calcium nitrate filtrate II and silicon slag II, preparing cement by the silicon slag, utilizing the calcium nitrate filtrate II in the next whisker procedure, and absorbing tail gas by 20% ammonia water; the ratio of the amounts of the substances is n (H 2SO4：Ca2+) =0.95: adding sulfuric acid with the concentration of 40% and calcium nitrate filtrate into a whisker reaction tank at the same time, controlling the temperature of the reaction feed liquid to be 95 ℃, stirring at the speed of 200r/min, allowing the reaction feed liquid to enter a crystallization tank after reacting 1.0 h, cooling and crystallizing for 2h at the temperature of 35 ℃, filtering and washing to obtain a filter cake III and a mother liquor III, washing the filter cake III with hot water at the temperature of 70-80 ℃ and then drying to obtain calcium sulfate whiskers, combining the filtrate and washing water to obtain the mother liquor III, and sending the mother liquor III to an acidolysis process to circularly decompose coarse calcium carbonate. The obtained calcium sulfate whisker has an aspect ratio of 46, a purity of 98.7% and a whiteness of 97.
The above embodiments are merely preferred embodiments of the present application, and should not be construed as limiting the present application, and the embodiments and features of the embodiments of the present application may be arbitrarily combined with each other without collision.
Claims (3)
1. A method for preparing calcium sulfate whisker and co-producing ammonium sulfate by phosphogypsum cyclic decomposition is characterized by comprising the following steps: the method comprises the following steps:
(a) Phase inversion procedure: phosphogypsum reacts with dilute sulfuric acid to remove impurities, filtering, washing to be neutral, then, adding water into a phase inversion tank to carry out slurry mixing, introducing ammonia water to absorb ammonium carbonate salt solution after tail gas of acidolysis procedure, carrying out phase inversion reaction, and filtering to obtain ammonium sulfate solution I and coarse calcium carbonate slag I;
(b) Acidolysis process: adding nitric acid into the coarse calcium carbonate slag I for acidolysis, and filtering to obtain slag II and calcium nitrate filtrate II; removing slag II to produce cement, wherein calcium nitrate filtrate II is used for preparing calcium sulfate whiskers, and tail gas ammonia water is removed for absorption to decompose phosphogypsum;
(c) Whisker preparation process:
(1) Sulfuric acid and calcium nitrate filtrate II are added into a reaction tank at the same time, and the mass ratio of the sulfuric acid to the calcium nitrate filtrate II is 0.95-1.05: 1, a step of;
(2) The reaction temperature of sulfuric acid and the calcium nitrate filtrate II is 80-95 ℃, the stirring speed is 200r/min, and the reaction time is 1.0-1.5 h;
(3) Cooling and crystallizing the reaction feed liquid at 25-35 ℃ to 1.5-2.0 h, filtering to obtain a filter cake III and a mother liquor, washing and drying the filter cake III to obtain calcium sulfate whisker, wherein the purity of the calcium sulfate whisker is more than or equal to 98%, the length-diameter ratio is more than or equal to 45, and the whiteness is more than or equal to 95%; mixing the mother solution with washing water, adding concentrated nitric acid to adjust the concentration to 50-60%, and then performing acidolysis to circularly decompose coarse calcium carbonate slag I;
(d) Ammonium sulfate process: neutralizing the ammonium sulfate filtrate I by adding sulfuric acid to adjust the pH to 4.5-5, removing vacuum concentration crystallization, drying to obtain an ammonium sulfate finished product, concentrating condensed water, performing a phase-removing conversion process, and performing size mixing and washing;
the phase conversion process comprises the following steps of: 1, the reaction temperature is 60-70 ℃, the stirring speed is 200-250 r/min, and the reaction time is 1.5-2 h.
2. The method for preparing calcium sulfate whisker and co-producing ammonium sulfate by phosphogypsum cyclic decomposition according to claim 1, which is characterized by comprising the following steps: in the acidolysis process, water is added into coarse calcium carbonate slag I for size mixing, nitric acid with the concentration of 40-60% is slowly added for reaction, and the mass ratio of the nitric acid to the calcium is controlled to be 2.0-2.05: 1, the reaction temperature is 70-80 ℃, the stirring speed is 250-300 r/min, and after 1.0-1.5 h of reaction, the calcium nitrate filtrate II and filter residue II are obtained by filtering.
3. The method for preparing calcium sulfate whisker and co-producing ammonium sulfate from phosphogypsum according to claim 1 is characterized in that: adding 40-60% sulfuric acid into the filtrate obtained in the phase conversion step to adjust the pH value of the solution to 4.5-5, then carrying out vacuum concentration until the slurry concentration is 1.35-1.36 g/ml, cooling, crystallizing and filtering at 58-60 ℃ to obtain ammonium sulfate crystals, and drying the crystals at 110-120 ℃ to obtain an ammonium sulfate product, wherein the N content of the obtained ammonium sulfate product is more than or equal to 21.0%.
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| CN111333050B (en) * | 2020-04-20 | 2023-03-07 | 武汉工程大学 | Combined production of magnesium ammonium phosphate and MgCO from phosphorus tailings and phosphogypsum 3 And by-product NH 4 Cl process |
| CN115504695B (en) * | 2022-09-06 | 2023-12-12 | 宜昌邦普循环科技有限公司 | A kind of recycling method of phosphogypsum |
| CN115924952B (en) * | 2022-12-14 | 2024-05-03 | 西南科技大学 | Anhydrite powder, gypsum whisker and preparation method thereof |
| CN116143141A (en) * | 2023-03-31 | 2023-05-23 | 贵州新东浩化工材料科技有限公司 | Process for producing ammonium sulfate by using phosphate rock and grading and utilizing calcium element |
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| CN101492178A (en) * | 2009-03-06 | 2009-07-29 | 瓮福（集团）有限责任公司 | Method for joint production of ammonium sulphate and calcium carbonate with phosphogypsum |
| CN108112248A (en) * | 2015-05-20 | 2018-06-01 | 费林有限责任公司 | Method for Composite Treatment of Phosphogypsum |
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| CN107879363A (en) * | 2017-11-06 | 2018-04-06 | 湖北三宁化工股份有限公司 | A kind of method that nitric acid decomposes phosphorus mine tailing extracting sulfuric acid calcium pyroborate by-product magnesium hydroxide and ammonium nitrate magnesium |
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| CN101492178A (en) * | 2009-03-06 | 2009-07-29 | 瓮福（集团）有限责任公司 | Method for joint production of ammonium sulphate and calcium carbonate with phosphogypsum |
| CN108112248A (en) * | 2015-05-20 | 2018-06-01 | 费林有限责任公司 | Method for Composite Treatment of Phosphogypsum |
Non-Patent Citations (2)
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| Solubility of Calcium Sulfate Dihydrate in Nitric Acid Solutions Containing Calcium Nitrate and Phosphoric Acid;Yu Zhang et al.;《Journal of Chemical and Engineering Data》;19890131;第34卷(第1期);参见正文第1页左栏第1段 * |
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