CN116143141A - Process for producing ammonium sulfate by using phosphate rock and grading and utilizing calcium element - Google Patents
Process for producing ammonium sulfate by using phosphate rock and grading and utilizing calcium element Download PDFInfo
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Abstract
A process for producing ammonium sulfate by using phosphorite and grading and utilizing calcium element, which comprises the following steps: step S1 carbonization: reacting phosphogypsum with 45-50% ammonium carbonate solution by mass fraction to obtain a reaction material; step S2, filtering: filtering the reaction materials to obtain a calcium carbonate filter cake and an ammonium sulfate filtrate; step S3, concentration: concentrating the ammonium sulfate filtrate to obtain an ammonium sulfate concentrated solution with the mass fraction of 41% -50%; step S4, neutralization: adding sulfuric acid into the ammonium sulfate concentrated solution, and controlling the pH value to be 5.0-6.8; step S5, granulating and drying: granulating and drying the neutralized ammonium sulfate concentrate to obtain granular ammonium sulfate; step S6, grading utilization of calcium carbonate. The process for producing ammonium sulfate by using the phosphogypsum and grading the calcium element has strong adaptability to phosphogypsum and great competitive advantage of products with strong flexibility of device process.
Description
Technical Field
The invention relates to the technical field of industrial solid waste recycling, in particular to a method for producing ammonium sulfate and grading and utilizing calcium carbonate by taking phosphogypsum as a raw material.
Background
Phosphogypsum is a solid byproduct of wet-process phosphoric acid production, and 1 ton of P is produced per production 2 O 5 The wet phosphoric acid by-product is approximately 5 tons of phosphogypsum, which contains a large amount of impurities (such as SiO 2 P, F, etc.). For a long time, the piling is the main stream treatment means of phosphogypsum, and the total piling amount of phosphogypsum in China is about 6.0 hundred million tons at present. Yield of 7810 ten thousand tons in phosphogypsum industry in 2020 is reported, comprehensive utilization rate is 3260 ten thousand tons, and utilization rate is 44%. In 2021, the yield of phosphogypsum industry in China is about 7460 ten thousand tons, and the comprehensive utilization rate is less than 48.0%. The pressure for fully utilizing phosphogypsum is still huge. Along with the discharge of the environment-friendly policy of 'constant production with slag', reasonable utilization of phosphogypsum becomes the primary problem facing the high-quality development of wet-process phosphorus chemical enterprises. For this reason, one of the technologies has been to prepare ammonium sulfate by gypsum method and to produce calcium carbonate as a byproduct.
Patent CN101269823a discloses a method for producing ammonium sulfate by using phosphogypsum as raw material, and the phosphogypsum reacts with lime and ammonium carbonate solution to obtain light calcium carbonate and crystal ammonium sulfate.
Patent CN113336242a discloses a method for preparing ammonium sulfate for water treatment by a solid-phase ball milling method by adding glass balls, phosphogypsum and ammonium bicarbonate into a ball mill.
Patent CN112225228A discloses a method and system for preparing ammonium sulfate by using kiln tail waste gas of cement kiln and phosphogypsum. The ammonia water is used for absorbing CO in the tail gas of the cement kiln 2 An ammonium carbonate solution was obtained. And mixing and grinding and leaching the ammonium carbonate solution and phosphogypsum, and carrying out solid-liquid separation to obtain ammonium sulfate and solid residues.
Ding Wenjin et al publication of phosphogypsum mineralized CO 2 Preparation of high purity calcium carbonate and product Regulation preparation of high purity CaCO by researching ammonia enhanced phosphogypsum leachate in ammonium chloride System using phosphogypsum as raw material 3 Is a reaction process of (a).
The time-cooling phosphogypsum slurry after water washing is stirred and heated in the research of preparing light calcium carbonate and morphology regulation of the byproduct phosphogypsum, and then ammonium carbonate solution is added dropwise. And after the reaction is finished, filtering to obtain light calcium carbonate and ammonium sulfate.
Disclosure of Invention
The invention aims to provide a process for processing solid waste phosphogypsum into a high value-added product.
The invention solves the technical problems by adopting the following technical scheme.
The invention provides a process for producing ammonium sulfate by using phosphorus stone and grading and utilizing calcium element, which is characterized by comprising the following steps:
step S1 carbonization: reacting phosphogypsum with 45-50% ammonium carbonate solution by mass fraction to obtain a reaction material;
the main component of phosphogypsum is CaSO 4 It contains a large amount of impurities such as SiO 2 、SO 4 2- F, fe, mg, al, K, na and P. Wherein SiO is 2 And SO 4 2- The content of (2) is the highest. Carbonization refers to the reaction of 45-50% by mass of ammonium carbonate solution with phosphogypsum to generate calcium carbonate and ammonium sulfate. The reaction (formula below) is a liquid-solid two-phase exothermic reaction. The reaction equation is as follows:
CaSO 4 ·2H 2 O(s)+(NH 4 ) 2 CO 3 (l)＝CaCO 3 (s)+(NH 4 ) 2 SO 4 (l)+2H 2 O(l)
specifically, the carbonization temperature in the reaction is 40-90 ℃, the carbonization pressure is less than or equal to 0.3MPaG, the reaction residence time is 3-6 h, and the mass fraction of the ammonium carbonate solution is 45-50%.
The reaction effect is better when the carbonization pressure is 4-90 kPaG;
wherein the degree of carbonization of the ammonium carbonate solution (2 n [ NH ] 3 ]/n[CO 2 ]）=（1.2 to 1): 1, so as to ensure the alkalinity of the solution, be favorable for the generation of calcium carbonate and promote the improvement of the conversion rate of carbonization reaction. .
Preferably, the (NH) in the ammonium carbonate solution is a solution that is easily decomposed at ordinary temperature 4 ) 2 CO 3 And CaSO in phosphogypsum 4 The ratio of the amounts of the substances is [ (NH) 4 ) 2 CO 3 ]：[CaSO 4 ]= (1 to 1.2): 1. because the quality of phosphogypsum is not constant, the CaSO in phosphogypsum should be treated before the reaction 4 Is measured.
Preferably, the carbonization is multistage, and the reaction effect is better. The reason is that ammonium carbonate is unstable and is easy to decompose when stored at normal temperature, and ammonia gas and ammonium bicarbonate are formed. Ammonium carbonate is added for multiple times in the grading reaction, so that the decomposition of the ammonium carbonate can be inhibited.
Preferably, carbonization comprises:
first-stage carbonization: the temperature is 65-90 ℃, the pressure is less than or equal to 120kPaG, the residence time is 0.5-1 h, ammonia is added to adjust the pH to be more than or equal to 7, and the amount of the added ammonium carbonate substance is n 1 ；
Second-stage carbonization: the temperature is 65-90 ℃, the pressure is less than or equal to 100kPaG, the residence time is 0.5-1 h, ammonia is added to adjust the pH to be more than or equal to 7, and the amount of the added ammonium carbonate substance is n 2 ；
Third-stage carbonization: the temperature is 50-65 ℃, the pressure is less than or equal to 80kPaG, the residence time is 1-2 h, and ammonia is added to adjust the pH to be more than or equal to 7;
fourth-stage carbonization: the temperature is 40-50 ℃, the pressure is less than or equal to 40kPaG, the residence time is 1-2 h, and ammonia is added to adjust the pH to be more than or equal to 7;
wherein n is 1 ：n 2 =3~7；
And (3) carrying out reaction on the excessive ammonium carbonate and phosphogypsum for 3-6 hours in four pressure-maintaining stirring reaction kettles connected in series to realize full conversion of phosphogypsum. Ammonium carbonate is unstable and is easy to decompose when stored at normal temperature, and ammonia gas and ammonium bicarbonate are formed. The ammonium carbonate is distributed into the first two stages of reactions in proportion, so that the decomposition of the ammonium carbonate can be effectively inhibited. The ammonia gas is supplied to ensure that the reaction is performed in an alkaline environment, so that the decomposition reaction of ammonium carbonate can be reversely performed, and the decomposition of ammonium carbonate can be inhibited. The temperature of the materials in the reaction kettle can be sequentially increased from high to low according to the flow direction of the materials, namely the rapid reaction of the prior first-stage carbonization is realized, and the decomposition of ammonium carbonate is reduced. And the carbonization reaction pressure is high, and the decomposition of ammonium carbonate can be restrained.
Preferably, the material of at least one of the first stage carbonization, the second stage carbonization, the third stage carbonization and the fourth stage carbonization is crushed by a high speed shear. The reactants and the products of the carbonization reaction are all solid, so that the solid materials are broken in the reaction process to avoid wrapping, and the reaction process can be greatly accelerated.
Step S2, filtering: the reaction materials are subjected to first filtration to obtain a calcium carbonate filter cake and an ammonium sulfate filtrate; the carbonization reaction is caused by excessive ammonium carbonate, and a small amount of ammonium carbonate remains in the ammonium sulfate filtrate.
Step S3, concentration: concentrating the ammonium sulfate filtrate to obtain an ammonium sulfate concentrated solution with the mass fraction of 41% -50%; the unreacted ammonium carbonate remained in the ammonium sulfate filtrate is decomposed into ammonia gas entering the tail gas and ammonium bicarbonate remained in the solution by heating.
Preferably, the mass fraction of the ammonium sulfate concentrated solution is controlled to be 44% -48%. The final granulation effect at the above concentration is more excellent.
Step S4, neutralization: adding sulfuric acid into the ammonium sulfate concentrated solution, and controlling the pH value to be 5.0-6.8; the above steps can neutralize part of the ammonium bicarbonate and a small amount of free ammonia remained in the ammonium sulfate concentrated solution.
Preferably, phosphoric acid is added to the ammonium sulfate concentrate, and the phosphoric acid and sulfuric acid jointly neutralize the ammonium sulfate concentrate; the addition amount of phosphoric acid is required to meet the content of P in impurity ammonium phosphate salt in granular ammonium sulfate 2 O 5 The mass fraction of (2) is 0.1% -4%. Part of phosphoric acid is added into the neutralization acid, so that the particle strength of the granulated ammonium sulfate obtained by granulation can be effectively improved. And the ammonium sulfate obtained by adopting the granulating step is convenient to transport.
Step S5, granulating and drying: the neutralized ammonium sulfate concentrated solution is subjected to second granulation and drying to obtain granular ammonium sulfate; the neutralized ammonium sulfate concentrated solution can be sent into a rotary drum granulator through a nozzle and synchronously contacted with hot air to realize drying, thus preparing granular ammonium sulfate.
Preferably, in step S5, one of monoammonium phosphate, monoammonium phosphate and potassium salt is added to prepare the compound fertilizer. The monoammonium phosphate and monoammonium phosphate can be used as raw materials of compound fertilizers and can also be used as an adhesive to enhance the strength of product particles.
Step S6, grading utilization of calcium carbonate. The calcium carbonate is reasonably utilized in a layering way, so that the utilization rate is improved.
Preferably, step S6 comprises preparing calcium carbonate powder: and drying and crushing the calcium carbonate filter cake to obtain calcium carbonate powder. Wherein, the calcium carbonate filter cake is washed by clean water, and the attached ammonium sulfate solution is removed. The washing water returns to prepare ammonium carbonate solution needed by carbonization. So as to improve the utilization rate of waste and save the cost. The prepared calcium carbonate powder can meet the requirements of GB/T35164-2017 limestone powder for cement, mortar and concrete.
Preferably, step S6 comprises preparing calcium carbonate powder: the mixed alkali liquor and the calcium carbonate filter cake are subjected to pressure maintaining reaction for 4-6 hours at the temperature of 100-150 ℃ and the pressure of less than or equal to 0.65MPaG, and then are subjected to third filtration and washing to obtain a refined filter cake and sodium silicate filtrate, and the refined filter cake is dried and crushed to obtain calcium carbonate powder; wherein the mixed alkali solution contains 20-30% by mass of NaOH and 0.05-0.2% by mass of Na 2 CO 3 Or the mixed alkali solution contains 20-30% of KOH and 0.05-0.2% of K 2 CO 3 。
Wherein the mixed alkali solution contains 20-30% by mass of NaOH and 0.05-0.2% by mass of Na 2 CO 3 In this case, calcium carbonate satisfying HG/T2226-2019 and industrial sodium silicate satisfying GB/T4209-2008 can be produced. The mixed alkali solution contains 20-30% by mass of KOH and 0.05-0.2% by mass of K 2 CO 3 In this case, calcium carbonate and potash water glass satisfying HG/T2226-2019 can be produced.
Preferably, step S6 comprises preparing a granular heavy calcium/compound fertilizer: mixing and reacting the calcium carbonate filter cake with phosphoric acid to obtain a mixture, and drying the mixture through first granulating to obtain granular heavy calcium.
Preferably, step S6 further comprises preparing calcium nitrate crystals: and mixing part of the calcium carbonate filter cake with insufficient nitric acid for reaction, then performing second filtration to obtain calcium nitrate filtrate, and crystallizing, filtering and drying to obtain calcium nitrate crystals.
Preferably, extracting part of the calcium nitrate filtrate to the mixture, delivering the filter residue obtained by the second filtration to the mixture, and drying the mixture through first granulation to obtain the granular compound fertilizer;
preferably, the calcium nitrate filtrate reacts with the barium nitrate solution before crystallization, and the prepared barium sulfate filter residue is sent to a mixture, and is subjected to first granulation and drying to prepare the granular compound fertilizer.
Compared with the prior art, the invention has the following beneficial effects:
(1) Has strong adaptability to phosphogypsum. Phosphogypsum coming off line from a wet-process phosphoric acid plant directly reacts with ammonium carbonate, and pretreatment procedures such as water washing, lime neutralization, floatation desilication and the like are not needed. Can be applied to phosphogypsum with various qualities.
(2) The device has strong process flexibility. The method can produce various products such as granular ammonium sulfate, granular heavy calcium carbonate, light calcium carbonate, compound fertilizer, full water-soluble calcium nitrate and the like, has rich product system and quality classification, and can adjust the product structure according to the quality of raw materials and market demands. The impurities carried by phosphogypsum can be fully digested.
(3) The product has great competitive advantage. The added value of granular ammonium sulfate with high particle strength, full water-soluble calcium nitrate, high-purity light calcium carbonate and the like in the product system is high. Meanwhile, products such as heavy calcium, compound fertilizer and the like can fully contain impurities brought by phosphogypsum. Compared with the prior device, the method disclosed by the patent has obviously improved economical efficiency, and is beneficial to the long-term stable operation of the phosphogypsum recycling device
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings that are needed in the embodiments will be briefly described below, it being understood that the following drawings only illustrate some embodiments of the present invention and therefore should not be considered as limiting the scope, and other related drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic illustration of the process flow of embodiment 1 of the present invention;
FIG. 2 is a schematic diagram of the carbonization process in step S1 of example 1 of the present invention.
Description of the embodiments
In order to make the objects, technical solutions and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below. The specific conditions are not noted in the examples and are carried out according to conventional conditions or conditions recommended by the manufacturer.
The ammonium sulfate is an excellent nitrogenous fertilizer (commonly known as fertilizer field powder), is suitable for general soil and crops, can make branches and leaves grow vigorously, improves fruit quality and yield, enhances the resistance of crops to disasters, and can be used as base fertilizer, additional fertilizer and seed fertilizer. Meanwhile, the modified polyurethane foam is widely applied to industries such as leather, metallurgy, biological fermentation, printing and dyeing, flame retardance and the like. The by-products or the discharged waste gas in the production are used for absorbing by sulfuric acid or ammonia water (such as the sulfuric acid absorbs ammonia in coke oven gas, the ammonia water absorbs sulfur dioxide in the flue gas of a smelting plant, the ammonia in the production of the capron or the sulfuric acid waste liquid in the production of titanium dioxide by a sulfuric acid method) in industry. There are also methods for preparing ammonium sulfate by gypsum method (natural gypsum or phosphogypsum, ammonia and carbon dioxide are used as raw materials), but the cost is high, and the method has no market advantage.
Calcium carbonate is an important chemical raw material, and is widely used in the departments of papermaking, metallurgy, glass, alkali production, rubber, medicine, food, pigment, functional material, organic chemical industry and the like, and the general purity requirement is higher than or equal to 97%, even more than or equal to 99.9%.
The triple superphosphate, which is simply weighed, can be used as a fertilizer for various soils and crops, and can be used as a raw material of base fertilizer, additional fertilizer and compound (mixed) fertilizer. Is widely applicable to various grain crops and economic crops such as rice, wheat, corn, sorghum, cotton, melons, fruits, vegetables and the like. It is also used for glass manufacture, plastic stability and livestock auxiliary feed.
Calcium nitrate is used in the electronics industry for coating cathodes, analytical reagents and firework materials, and is also a typical fast acting foliar fertilizer for use in agriculture as a fast acting fertilizer for acid soil and a fast calcium supplement for plants. Calcium nitrate with low water insoluble content is a high-end full water-soluble fertilizer, and is very popular in the market.
The invention will be further described with reference to the following description and examples, which include but are not limited to the following examples.
Examples
The embodiment provides a process for producing ammonium sulfate by using phosphorus stone and grading and utilizing calcium element, which specifically comprises the following steps:
step S1 carbonization: phosphogypsum is reacted with 48% ammonium carbonate solution by mass fraction to obtain a reaction material. Wherein the degree of carbonization of the ammonium carbonate solution (2 n [ NH ] 3 ]/n[CO 2 ]) = (1.2 to 1): 1. the phosphogypsum has variable quality, and the CaSO in the phosphogypsum should be treated before the reaction 4 Is measured. Specifically, the present embodiment adopts a four-stage carbonization reaction, and the mixture contains 100mol of CaSO according to the mass 4 The phosphogypsum and an ammonium carbonate solution containing 90mol of ammonium carbonate are fed to a first stage of carbonization. The reaction temperature was 80℃and the residence time was 0.75h, the pressure was 100kPaG. The output of the first stage carbonization and an ammonium carbonate solution containing 20mol of ammonium carbonate were fed to a second stage carbonization at a temperature of 70℃and a residence time of 0.75h at a pressure of 80kPaG. The discharged material of the second stage carbonization enters the third stage carbonization, the temperature is 60 ℃, the residence time is 1.5h, and the pressure is 60kPaG. The discharged material of the third stage carbonization enters the fourth stage carbonization, the temperature is 45 ℃, the retention time is 1.5h, and the pressure is 30kPaG. The four-stage carbonization is equipped with a high-speed shearing machine for circularly crushing the materials in the dispersion kettle. And ammonia gas is introduced into the four-stage carbonization to adjust the pH to 8-9.
Step S2, filtering: the reaction materials are subjected to first filtration to obtain a calcium carbonate filter cake and an ammonium sulfate filtrate; the carbonization reaction is caused by excessive ammonium carbonate, and a small amount of ammonium carbonate remains in the ammonium sulfate filtrate.
Step S3, concentration: the ammonium sulfate filtrate was concentrated to 46% by mass of an ammonium sulfate concentrate.
Step S4, neutralization: sulfuric acid and phosphoric acid were added to the ammonium sulfate concentrate to neutralize a portion of the ammonium bicarbonate and a small amount of free ammonia remaining in the ammonium sulfate concentrate solution, and ph=6.0 was controlled. The addition amount of phosphoric acid is required to meet the content of P in impurity ammonium phosphate salt in granular ammonium sulfate 2 O 5 The mass fraction of (2) is 0.1% -4%.
Step S5 manufacturingAnd (3) drying the granules: delivering the neutralized ammonium sulfate concentrate into a rotary drum granulator through a nozzle, adding monoammonium phosphate, synchronously contacting with hot air, and performing second granulation and drying to obtain 16-20 compound fertilizer (16 represents that the mass fraction of N is more than or equal to 16%,20 represents that P) 2 O 5 The mass fraction is more than or equal to 20 percent.
The step S6 of classifying and utilizing the calcium carbonate comprises the following steps:
preparing calcium carbonate powder: will contain 25% by mass of NaOH and 0.12% by mass of Na 2 CO 3 The mixed alkali liquor and the washed partial calcium carbonate filter cake react for 5 hours under the pressure maintaining condition of 0.5MPaG at the temperature of 120 ℃, and then the refined filter cake and sodium silicate filtrate are obtained after the third filtering and washing, and the sodium silicate filtrate meets the industrial sodium silicate of GB/T4209-2008. And drying and crushing the refined filter cake to obtain the calcium carbonate powder meeting HG/T2226-2019.
Preparing calcium nitrate crystals: and mixing and reacting the washed partial calcium carbonate filter cake with insufficient nitric acid, and then performing second filtration to obtain calcium nitrate filtrate, and crystallizing, filtering and drying the calcium nitrate filtrate to obtain the high-purity tetrahydrate calcium nitrate crystal.
Preparing a granular compound fertilizer: and mixing and reacting the washed partial calcium carbonate filter cake with phosphoric acid to obtain a mixture. And simultaneously extracting part of calcium nitrate filtrate to the mixture. The rest of calcium nitrate filtrate reacts with barium nitrate solution before crystallization, and the prepared barium sulfate filter residue is sent to the mixture. And (3) conveying filter residues obtained by the second filtration to the mixture, and drying the mixture through the first granulation to obtain the granular compound fertilizer.
Examples
This example provides a process for producing ammonium sulfate using a phosphorus stone and classifying the use of a calcium element, which is different from example 1 in that:
the step S6 of classifying and utilizing the calcium carbonate comprises the following steps:
preparing calcium carbonate powder: will contain 25% by mass of NaOH and 0.12% by mass of Na 2 CO 3 The mixed alkali liquor and the washed partial calcium carbonate filter cake react for 5 hours under the pressure maintaining condition of 0.5MPaG at the temperature of 120 ℃, and then the refined filter cake and sodium silicate filtrate are obtained after the third filtering and washing, and the sodium silicate filtrate meets the industrial sodium silicate of GB/T4209-2008. The refined filter cake is dried and crushed,the calcium carbonate powder meeting HG/T2226-2019 can be prepared.
Preparing calcium nitrate crystals: and mixing and reacting the washed partial calcium carbonate filter cake with insufficient nitric acid, and then performing second filtration to obtain calcium nitrate filtrate, and crystallizing, filtering and drying the calcium nitrate filtrate to obtain the high-purity tetrahydrate calcium nitrate crystal.
Preparing granular heavy calcium: and mixing and reacting the washed partial calcium carbonate filter cake with phosphoric acid to obtain a mixture. And then the granular heavy calcium is obtained after the first granulation and drying.
Examples
This example provides a process for producing ammonium sulfate using a phosphorus stone and classifying the use of a calcium element, which is different from example 1 in that:
the fractional utilization of the calcium carbonate in step S6 does not include the preparation of calcium carbonate powder.
Examples
This example provides a process for producing ammonium sulfate using a phosphorus stone and classifying the use of a calcium element, which is different from example 1 in that:
the staged utilization of the calcium carbonate in step S6 does not involve the preparation of a granular compound fertilizer.
Examples
This example provides a process for producing ammonium sulfate using a phosphorus stone and classifying the use of a calcium element, which is different from example 2 in that:
the fractional utilization of the calcium carbonate of step S6 does not involve the preparation of calcium nitrate crystals.
Examples
This example provides a process for producing ammonium sulfate using a phosphorus stone and classifying the use of a calcium element, which is different from example 1 in that:
the preparation of the calcium carbonate powder in the step S6 of classifying and utilizing the calcium carbonate comprises the following steps: and drying and crushing the washed calcium carbonate filter cake to obtain calcium carbonate powder.
Examples
The embodiment provides a process for producing ammonium sulfate by using phosphorus stone and grading and utilizing calcium element, which specifically comprises the following steps:
step S1 carbonization: phosphogypsum is reacted with 45% ammonium carbonate solution by mass percent to obtain a reaction material. Wherein, the liquid crystal display device comprises a liquid crystal display device,degree of carbonization of ammonium carbonate solution (2 n [ NH ] 3 ]/n[CO 2 ]) = (1.2 to 1): 1. the phosphogypsum has variable quality, and the CaSO in the phosphogypsum should be treated before the reaction 4 Is measured. Specifically, the present embodiment adopts a four-stage carbonization reaction, and the mixture contains 100mol of CaSO according to the mass 4 The phosphogypsum and an ammonium carbonate solution containing 90mol of ammonium carbonate are fed to a first stage of carbonization. The reaction temperature was 65℃and the residence time was 0.5h, the pressure was 120kPaG. The output of the first stage carbonization and an ammonium carbonate solution containing 30mol of ammonium carbonate are fed to a second stage carbonization at a temperature of 90℃and a residence time of 0.5h at a pressure of 100kPaG. The discharged material of the second stage carbonization enters the third stage carbonization, the temperature is 65 ℃, the retention time is 1h, and the pressure is 80kPaG. The discharged material of the third stage carbonization enters the fourth stage carbonization, the temperature is 50 ℃, the retention time is 1h, and the pressure is 40kPaG. The four-stage carbonization is equipped with a high-speed shearing machine for circularly crushing the materials in the dispersion kettle. And the liquid ammonia is introduced into the four-stage carbonization to adjust the pH value to 7.
Step S2, filtering: the reaction materials are subjected to first filtration to obtain a calcium carbonate filter cake and an ammonium sulfate filtrate; the carbonization reaction is caused by excessive ammonium carbonate, and a small amount of ammonium carbonate remains in the ammonium sulfate filtrate.
Step S3, concentration: the ammonium sulfate filtrate was concentrated to a 41% by mass ammonium sulfate concentrate.
Step S4, neutralization: sulfuric acid was added to the ammonium sulfate concentrate to neutralize a part of the ammonium bicarbonate and a small amount of free ammonia remaining in the ammonium sulfate concentrate solution, and ph=6.8 was controlled.
Step S5, granulating and drying: and (3) delivering the neutralized ammonium sulfate concentrate into a rotary drum granulator through a nozzle, adding ammonium dihydrogen phosphate, synchronously contacting with hot air, and performing second granulation and drying to obtain the 16-20 compound fertilizer.
The step S6 of classifying and utilizing the calcium carbonate comprises the following steps:
preparing calcium carbonate powder: will contain 20% by mass of NaOH and 0.05% by mass of Na 2 CO 3 The mixed alkali liquor of (2) and the washed partial calcium carbonate filter cake react for 4 hours under the pressure maintaining condition of 0.65MPaG at 150 ℃, and then the refined filter cake and sodium silicate filtrate are obtained after the third filtration and washing, and the sodium silicate filtrate meets the GB/T4209-2008 sodium silicate. And drying and crushing the refined filter cake to obtain the calcium carbonate powder meeting HG/T2226-2019.
Preparing calcium nitrate crystals: and mixing and reacting the washed partial calcium carbonate filter cake with insufficient nitric acid, and then performing second filtration to obtain calcium nitrate filtrate, and crystallizing, filtering and drying the calcium nitrate filtrate to obtain the high-purity tetrahydrate calcium nitrate crystal.
Preparing a granular compound fertilizer: and mixing and reacting the washed partial calcium carbonate filter cake with phosphoric acid to obtain a mixture. And simultaneously extracting part of calcium nitrate filtrate to the mixture. The rest of calcium nitrate filtrate reacts with barium nitrate solution before crystallization, and the prepared barium sulfate filter residue is sent to the mixture. And (3) conveying filter residues obtained by the second filtration to the mixture, and drying the mixture through the first granulation to obtain the granular compound fertilizer.
Examples
The embodiment provides a process for producing ammonium sulfate by using phosphorus stone and grading and utilizing calcium element, which specifically comprises the following steps:
step S1 carbonization: phosphogypsum is reacted with 50% ammonium carbonate solution by mass fraction to obtain a reaction material. Wherein the degree of carbonization of the ammonium carbonate solution (2 n [ NH ] 3 ]/n[CO 2 ]) = (1.2 to 1): 1. the phosphogypsum has variable quality, and the CaSO in the phosphogypsum should be treated before the reaction 4 Is measured. Specifically, this embodiment employs a four-stage carbonization reaction, and contains 79mol of CaSO, based on the amount of the substance 4 The phosphogypsum and an ammonium carbonate solution containing 70mol of ammonium carbonate are fed to a first stage of carbonization. The reaction temperature was 90℃and the residence time was 1h, the pressure was 110kPaG. The output of the first stage carbonization and an ammonium carbonate solution containing 10mol of ammonium carbonate are fed to a second stage carbonization at a temperature of 65℃and a residence time of 1h at a pressure of 90kPaG. The discharged material of the second stage carbonization enters the third stage carbonization, the temperature is 50 ℃, the retention time is 2h, and the pressure is 70kPaG. And the discharged material of the third-stage carbonization enters a fourth-stage carbonization, the temperature is 40 ℃, the retention time is 2h, and the pressure is 20kPaG. The four-stage carbonization is equipped with a high-speed shearing machine for circularly crushing the materials in the dispersion kettle. And ammonia gas is introduced into the four-stage carbonization to adjust the pH value to 7.
Step S2, filtering: the reaction materials are subjected to first filtration to obtain a calcium carbonate filter cake and an ammonium sulfate filtrate; the carbonization reaction is caused by excessive ammonium carbonate, and a small amount of ammonium carbonate remains in the ammonium sulfate filtrate.
Step S3, concentration: the ammonium sulfate filtrate was concentrated to a 48% by mass ammonium sulfate concentrate.
Step S4, neutralization: sulfuric acid and phosphoric acid were added to the ammonium sulfate concentrate to neutralize a portion of the ammonium bicarbonate and a small amount of free ammonia remaining in the ammonium sulfate concentrate solution, and ph=5.0 was controlled. The addition amount of phosphoric acid is required to meet the content of P in impurity ammonium phosphate salt in granular ammonium sulfate 2 O 5 The mass fraction of (2) is 0.1% -4%.
Step S5, granulating and drying: feeding the neutralized ammonium sulfate concentrate into a rotary drum granulator through a nozzle, and adding KH 2 PO 4 And (3) synchronously contacting the slurry with hot air, and performing second granulation and drying to obtain the NPK compound fertilizer (nitrogen-phosphorus-potassium compound fertilizer).
The step S6 of classifying and utilizing the calcium carbonate comprises the following steps:
preparing calcium carbonate powder: will contain 30% by mass of NaOH and 0.2% by mass of Na 2 CO 3 The mixed alkali liquor and the washed partial calcium carbonate filter cake react for 6 hours under the pressure maintaining condition of 0.6MPaG at the temperature of 100 ℃, and then the refined filter cake and sodium silicate filtrate are obtained after the third filtering and washing, and the sodium silicate filtrate meets the industrial sodium silicate of GB/T4209-2008. And drying and crushing the refined filter cake to obtain the calcium carbonate powder meeting HG/T2226-2019.
Preparing calcium nitrate crystals: and mixing and reacting the washed partial calcium carbonate filter cake with insufficient nitric acid, and then performing second filtration to obtain calcium nitrate filtrate, and crystallizing, filtering and drying the calcium nitrate filtrate to obtain the high-purity tetrahydrate calcium nitrate crystal.
Preparing a granular compound fertilizer: and mixing and reacting the washed partial calcium carbonate filter cake with phosphoric acid to obtain a mixture. And simultaneously extracting part of calcium nitrate filtrate to the mixture. The rest of calcium nitrate filtrate reacts with barium nitrate solution before crystallization, and the prepared barium sulfate filter residue is sent to the mixture. And (3) conveying filter residues obtained by the second filtration to the mixture, and drying the mixture through the first granulation to obtain the granular compound fertilizer.
Examples
This example provides a process for producing ammonium sulfate using a phosphorus stone and classifying the use of a calcium element, which is different from example 1 in that:
step S6 classifying utilization of calcium carbonate comprising 25% by mass of NaOH and 0.12% by mass of Na 2 CO 3 The mixed alkali liquor of (2) is replaced by: comprises 25% by mass of KOH and 0.12% by mass of K 2 CO 3 Is added to the mixed alkali liquor. The product is changed from industrial sodium silicate of GB/T4209-2008 to potash water glass which can meet HG/T2226-2019.
Examples
This example provides a process for producing ammonium sulfate using a phosphorus stone and classifying the use of a calcium element, which is different from example 7 in that:
step S6 classification of calcium carbonate comprising 20% by mass of NaOH and 0.05% by mass of Na 2 CO 3 The mixed alkali liquor of (2) is replaced by: comprises 20% by mass of KOH and 0.12% by mass of K 2 CO 3 Is added to the mixed alkali liquor. The product is changed from industrial sodium silicate of GB/T4209-2008 to potash water glass which can meet HG/T2226-2019.
Examples
This example provides a process for producing ammonium sulfate using a phosphorus stone and classifying the use of a calcium element, which is different from example 8 in that:
step S6 classification of calcium carbonate comprising 30% by mass of NaOH and 0.2% by mass of Na 2 CO 3 The mixed alkali liquor of (2) is replaced by: comprises 30% by mass of KOH and 0.2% by mass of K 2 CO 3 Is added to the mixed alkali liquor. The product is changed from industrial sodium silicate of GB/T4209-2008 to potash water glass which can meet HG/T2226-2019.
Examples
This example provides a process for producing ammonium sulfate using a phosphorus stone and classifying the use of a calcium element, which is different from example 1 in that:
step S5, granulating and drying: and (3) delivering the neutralized ammonium sulfate concentrate into a rotary drum granulator through a nozzle, and performing second granulation and drying to obtain granular ammonium sulfate.
In conclusion, the process for producing ammonium sulfate by using the phosphogypsum and grading and utilizing the calcium element has the advantages of strong adaptability to phosphogypsum, strong flexibility of device process and great product competitive advantage.
The embodiments described above are some, but not all embodiments of the invention. The detailed description of the embodiments of the invention is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Claims (10)
1. A process for producing ammonium sulfate from a phosphorus stone and classifying the use of a calcium element, comprising the steps of:
step S1 carbonization: reacting phosphogypsum with 45-50% ammonium carbonate solution by mass fraction to obtain a reaction material;
step S2, filtering: the reaction materials are subjected to first filtration to obtain a calcium carbonate filter cake and an ammonium sulfate filtrate;
step S3, concentration: concentrating the ammonium sulfate filtrate to obtain an ammonium sulfate concentrated solution with the mass fraction of 41% -50%;
step S4, neutralization: adding sulfuric acid into the ammonium sulfate concentrated solution, and controlling the pH value to be 5.0-6.8;
step S5, granulating and drying: the neutralized ammonium sulfate concentrated solution is subjected to second granulation and drying to obtain granular ammonium sulfate;
step S6, grading utilization of calcium carbonate.
2. The process for producing ammonium sulfate using fluorite and classifying the calcium element according to claim 1, wherein the step S6 includes preparing calcium carbonate powder: and drying and crushing the calcium carbonate filter cake to obtain calcium carbonate powder.
3. The process for producing ammonium sulfate using fluorite and classifying the calcium element according to claim 1, wherein the step S6 includes preparing calcium carbonate powder: mixing alkali liquor with the calcium carbonate filter cake at 100-150 DEG CPressure maintaining reaction is carried out for 4-6 hours under the pressure of less than or equal to 0.65MPaG, then the third filtration and the washing are carried out, so as to obtain a refined filter cake and sodium silicate filtrate, and the refined filter cake is dried and crushed, so as to obtain calcium carbonate powder; wherein the mixed alkali solution contains 20-30% by mass of NaOH and 0.05-0.2% by mass of Na 2 CO 3 Or the mixed alkali solution contains 20-30% by mass of KOH and 0.05-0.2% by mass of K 2 CO 3 。
4. A process for the production of ammonium sulphate by means of hawse and the fractional utilization of elemental calcium according to any one of claims 1-3 wherein step S6 comprises the preparation of granular heavy calcium/compound fertilizer: and mixing the calcium carbonate filter cake with phosphoric acid to react to obtain a mixture, and performing first granulation and drying to obtain granular heavy calcium.
5. The process for producing ammonium sulfate and classifying calcium element by use of phosphorus stone according to claim 4, wherein said step S6 further comprises preparing calcium nitrate crystals: mixing part of the calcium carbonate filter cake with insufficient nitric acid for reaction, then performing second filtration to obtain calcium nitrate filtrate, and crystallizing, filtering and drying to obtain calcium nitrate crystals;
preferably, extracting part of the calcium nitrate filtrate to the mixture, delivering the filter residue obtained by the second filtration to the mixture, and drying the mixture through the first granulation to obtain the granular compound fertilizer;
preferably, the calcium nitrate filtrate reacts with the barium nitrate solution before crystallization, and the prepared barium sulfate filter residue is sent to a mixture, and is subjected to first granulation and drying to prepare the granular compound fertilizer.
6. The process for producing ammonium sulfate by using the phosphoite and classifying the calcium element according to claim 1, wherein in the step S1, the carbonization temperature is 40-90 ℃, the carbonization pressure is less than or equal to 0.3MPaG, the reaction residence time is 3-6 h, and the mass fraction of the ammonium carbonate solution is 45-50%;
preferably, the carbonization pressure is 4-120 kPaG;
preferably, the carbonic acidDegree of carbonization of ammonium solution (2 n [ NH ] 3 ]/n[CO 2 ]）=（1.2~1）：1。
7. The process for producing ammonium sulfate using fluorite and classifying calcium element according to claim 1, wherein in the step S1, (NH 4 ) 2 CO 3 And CaSO in the phosphogypsum 4 The ratio of the amounts of the substances is [ (NH) 4 ) 2 CO 3 ]：[CaSO 4 ]=（1~1.2）：1。
8. The process for producing ammonium sulfate and classifying calcium element by use of phosphorus stone according to claim 7, wherein in said step S1, said carbonization is in multiple stages;
preferably, the carbonizing includes:
first-stage carbonization: the temperature is 65-90 ℃, the pressure is less than or equal to 120kPaG, the residence time is 0.5-1 h, ammonia is added to adjust the pH to be more than or equal to 7, and the amount of the added ammonium carbonate substance is n 1 ；
Second-stage carbonization: the temperature is 65-90 ℃, the pressure is less than or equal to 100kPaG, the residence time is 0.5-1 h, ammonia is added to adjust the pH to be more than or equal to 7, and the amount of the added ammonium carbonate substance is n 2 ；
Third-stage carbonization: the temperature is 50-65 ℃, the pressure is less than or equal to 80kPaG, the residence time is 1-2 h, and ammonia is added to adjust the pH to be more than or equal to 7;
fourth-stage carbonization: the temperature is 40-50 ℃, the pressure is less than or equal to 40kPaG, the residence time is 1-2 h, and ammonia is added to adjust the pH to be more than or equal to 7;
wherein n is 1 ：n 2 =3~7；
Preferably, the material of at least one of the first stage carbonization, the second stage carbonization, the third stage carbonization and the fourth stage carbonization is crushed by a high speed shearer.
9. The process for producing ammonium sulfate by using fluorite and classifying calcium according to claim 1, wherein phosphoric acid is added to the ammonium sulfate concentrate in the step S4, and the phosphoric acid neutralizes the ammonium sulfate concentrate together with the sulfuric acid.
10. The process for producing ammonium sulfate by using fluorite and classifying calcium element according to claim 1, wherein in the step S5, one of monoammonium phosphate, monoammonium phosphate and potassium salt is added to produce a compound fertilizer.
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