CN111302377A - Method for removing impurities and whitening ardealite - Google Patents
Method for removing impurities and whitening ardealite Download PDFInfo
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- CN111302377A CN111302377A CN202010170550.3A CN202010170550A CN111302377A CN 111302377 A CN111302377 A CN 111302377A CN 202010170550 A CN202010170550 A CN 202010170550A CN 111302377 A CN111302377 A CN 111302377A
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- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
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Abstract
The invention discloses a method for removing impurities and whitening ardealite, which comprises the following steps: 1) performing fineness rough machining on the phosphogypsum raw material; 2) acid leaching the phosphogypsum obtained in the step 1) by using sulfuric acid, heating and keeping the temperature constant to obtain a material; 3) adding the material obtained in the step 2) into a flotation agent, and performing flotation, concentration and separation; 4) feeding the slurry obtained in the step 3) after flotation separation into gravity separation operation for impurity removal to obtain concentrate; 5) filtering the concentrate obtained in the step 4), washing a filter cake, drying, and crushing to obtain the finished product of purified gypsum. The invention relates to a method for preparing high-whiteness and high-purity anhydrous calcium sulfate from phosphogypsum by utilizing a flotation/extraction/gravity separation process in a weakly acidic environment.
Description
Technical Field
The invention relates to the technical field of phosphorus chemical industry, in particular to a method for removing impurities and whitening phosphogypsum, which is a method for preparing high-whiteness and high-purity anhydrous calcium sulfate from phosphogypsum by utilizing a flotation/extraction/reselection process in an acidic environment.
Background
Phosphogypsum is industrial waste residue produced in the process of preparing phosphoric acid by reacting phosphorus-containing minerals represented by apatite with sulfuric acid in the production process of phosphoric acid, and data investigation and related reports show that 1 ton of phosphoric acid (P) is produced2O5In terms of) will yield 4-5 tons of phosphogypsum. At present, the emission of the phosphogypsum all over the world reaches more than 2 hundred million tons every year, and the phosphorus chemical industry in China emits about 7000 million tons of phosphogypsum every year, and the emission rate is increased by 15 percent every year. At present, the production amount of phosphogypsum in China is accumulated to exceed 3 hundred million tons, the stock amount exceeds 2.5 hundred million tons, but the utilization rate is less than 10 percent, and the stacking occupies a large amount of land. The treatment and comprehensive utilization of phosphogypsum are currently a worldwide problem.
Phosphogypsum has slight peculiar smell, is yellow-white, light grey-white or black grey fine powdery solid, and the main component of the phosphogypsum is calcium sulfate dihydrate, but the phosphogypsum also contains various other impurities such as quartz, undecomposed apatite, trace phosphorus, fluorine, potassium, sodium, iron, aluminum, titanium, organic matters and the like; meanwhile, harmful components such as soluble phosphorus, fluorine and the like diffuse and permeate to the surrounding environment in the stacking process to form a secondary pollution environment, so that the phosphogypsum is stored to bring huge environmental risks. In conclusion, the phosphogypsum harmless treatment and comprehensive utilization become key research projects in the fields of solid waste treatment and disposal and resource utilization.
In the application research of various phosphogypsum, the SiO in the phosphogypsum is found to have the influence on the environment2Carbon-based impurities, water-soluble phosphorus and fluorine have great influence on the technical indexes of delay time in the cement industry and the technical indexes of whiteness in the building material industry and the paper making industry. Only by removing the impurities simultaneously can a high-whiteness and high-purity gypsum product be obtained. To achieve the purpose, the application range of the phosphogypsum is expanded, and the phosphogypsum is researched at home and abroadThe research personnel have carried out a great deal of research and exploration on impurity removal of phosphogypsum, and the technology of the research and exploration can be roughly divided into a water washing method, a lime neutralization method, a ball milling method, a screening method, a flotation method, a calcination method and a sulfuric acid pickling method.
The application process of the process is different in autumn, but the phosphogypsum raw materials from different sources have respective limitations, for example, some insoluble impurities are often difficult to completely remove by pure water washing, heavy impurities with large particle size are difficult to remove by pure direct flotation, hydrophobic impurities are often mixed into a concentrate product and are difficult to remove, and in addition, for the raw materials of a multilayer inclusion mineral phase, the whiteness and the purity are difficult to further improve by a single flotation method. When the single calcination is carried out, phosphoric acid and fluoride volatilize, the environment is polluted, equipment is corroded, the high-temperature calcination energy consumption cost is high, and the calcination method has no effect on quartz impurities. The acid leaching process is generally considered to be a more effective phosphogypsum purification technology, but the single acid leaching is difficult to treat organic impurities and quartz impurities, and the gypsum purity is seriously influenced.
So far, no patent report of inventions related to processes of phosphogypsum decarburization dephosphorization and whitening impurity removal by adopting impurity removal and flotation combined leaching-extraction process is found.
Disclosure of Invention
Aiming at the problems in the prior art, the invention aims to provide a method for removing impurities and whitening phosphogypsum, which utilizes hydrocarbon and amine collectors to artificially enlarge the hydrophobicity difference between insoluble impurities and calcium sulfate in a certain acid-base environment so as to completely separate the insoluble impurities and the calcium sulfate according to the mineralogy and chemical characteristics of the phosphogypsum, simultaneously utilizes the combined operation characteristics of gravity separation processes (such as centrifugal washing of a hydrocyclone, fine screening washing or other conventional gravity separation equipment) and combines extraction under necessary conditions to further separate the calcium sulfate from water-soluble phosphorus, fluorine impurities and insoluble high-density impurities. Specifically, phosphogypsum, particularly phosphogypsum discharged in wet-process phosphoric acid industry, is used as a raw material, the material is subjected to particle size grading treatment according to the particle size characteristics of the raw material and the distribution rule of related impurities, the material with qualified particle size is subjected to water washing and flotation roughing operation to remove part of impurities, the obtained rough concentrate is subjected to acid leaching treatment (a neutral extractant or a recovery aid is used for removing impurities if necessary) to further separate part of inclusion impurities from gypsum components, then the obtained slurry is subjected to flotation refining (including froth flotation or double liquid flotation) under the weakly acidic or neutral condition to extract carbon, phosphorus and fluorine impurities in the phosphogypsum, the calcium sulfate slurry obtained through two-phase separation is washed by using a gravity separation process after size mixing, the final product is filtered to prepare high-quality anhydrous calcium sulfate concentrate, and the acidic filtrate and the extractant can be recycled. The middlings obtained in the steps can be further subjected to scavenging separation.
Aiming at the characteristics that the phosphogypsum is rich in impurity elements and insoluble impurities besides calcium sulfate and the embedding characteristics of mutual inclusion of part of impurities, the method adopts the combination of acid leaching and physical separation to remove and whiten the phosphogypsum: processing the raw material to a certain fineness, fully dissolving inclusions in the raw material by using sulfuric acid, transferring soluble impurities to a solution phase, and exposing insoluble impurities; then selectively adding a floating separation (flotation for short) agent according to a certain proportion according to the specific characteristics of the phosphogypsum, artificially increasing the hydrophobicity difference between impurities and calcium sulfate in an acidic environment, collecting the impurity particles to an organic phase to realize separation of the impurities and the calcium sulfate, then carrying out washing separation by a gravity separation (gravity separation for short) means such as a high-frequency vibrating fine sieve, a hydrocyclone group or other gravity separation means, and continuously removing most of the rest impurities according to the density difference and the granularity difference, wherein the method simultaneously uses calcium oxide to adjust the pH value of the slurry. The method can combine extraction operation to remove impurities if necessary. The content of impurities such as silicon, fluorine, phosphorus, carbon, iron, insoluble substances and the like in the phosphogypsum is reduced, the crystal form of calcium sulfate mineral is improved, high-purity anhydrous calcium sulfate is obtained, the whiteness of the product is improved, the technical requirements of most industrial departments on the phosphogypsum are met, the phosphogypsum waste is harmless, and meanwhile, a technical basis is provided for the industrialization of the phosphogypsum waste.
The invention provides a method for removing impurities and whitening phosphogypsum, which comprises the following steps:
1) performing fineness rough machining on the phosphogypsum raw material;
2) acid leaching the phosphogypsum obtained in the step 1) by using sulfuric acid, heating and keeping the temperature constant to obtain a material;
3) adding the material obtained in the step 2) into a flotation agent, and performing flotation, concentration and separation;
4) feeding the slurry obtained in the step 3) after flotation separation into gravity separation operation for impurity removal to obtain concentrate;
5) filtering the concentrate obtained in the step 4), washing a filter cake, drying, and crushing to obtain the finished product of purified gypsum.
Preferably, the impurities separated in the previous step are simultaneously added into a flotation agent for flotation scavenging separation, and the gypsum product included in the impurities is recovered.
Preferably, step 1) further comprises adding the roughed product to a flotation agent for prefloating.
Preferably, the flotation agent in the step 1) comprises one or more than two of a collecting agent, a foaming agent and a pH adjusting agent, and further preferably, the collecting agent comprises aliphatic hydrocarbon and/or aromatic hydrocarbon; the foaming agent is a pinitol substance; the pH regulator comprises H2SO4CaO and Ca (OH)2One or more than two of the above; the dosage of the collecting agent is 1-60kg/t, and the dosage of the pH regulator is 0.1-10 kg/t.
Preferably, the flotation agent in the step 3) comprises one or more than two of a collecting agent, a foaming agent and a pH adjusting agent, and further preferably, the collecting agent comprises aliphatic hydrocarbon and/or aromatic hydrocarbon; the foaming agent is a pinitol substance; the pH regulator comprises H2SO4CaO and Ca (OH)2One or more than two of the above; wherein the dosage of the collecting agent is 1-60kg/t, and the dosage of the pH regulator is 0.1-10 kg/t. The value range belongs to the conventional dosage range in the conventional flotation process, and experiments show that the economic and technical requirements are completely met.
Preferably, the collector comprises aliphatic hydrocarbon and/or aromatic hydrocarbon; the foaming agent is a pinitol substance; the pH regulator comprises H2SO4CaO and Ca (OH)2One or more than two of them. The flotation agents such as collectors and frothers are selected from the group consisting of hydrocarbons, amines andone or a combination of several of alcohol substances.
Preferably, the fineness in the step 1) is controlled below 250 meshes of a Taylor sieve 100, and more preferably (150 to 250 meshes) more than 80% by mass.
Preferably, the mass concentration of the sulfuric acid solution in the step 2) is 30-50%, and the liquid-solid mass ratio of the sulfuric acid solution to the phosphogypsum is 1.5:1-7: 1. In consideration of economy and quality of purified products, the sulfuric acid solution is greatly wasted due to the fact that the liquid-solid ratio is too large, the recovery cost is increased, and the slurry flowing and process purifying effects are affected due to the fact that the liquid-solid ratio is too small, so that the range of the liquid-solid mass ratio is 1.5:1-7: 1.
Preferably, the flotation separation in the step 3) comprises froth separation or double-liquid flotation separation, and the lower slurry layer is concentrated and separated; separating the upper layer organic phase, removing impurities, and recycling, wherein in the foam flotation separation, the using amount of a collecting agent is 1-60kg/t, and the using amount of a foaming agent is 0.05-8 kg/t; in the double-liquid flotation separation, the mass ratio of the flotation agent to the phosphogypsum is 5:1-2: 1.
Preferably, under the necessary condition (such as severe raw material properties or high product index requirement, such as obvious bimodal raw material particle size distribution or requirement of blue light whiteness higher than 95% of the product), the step 2) or the step 3) further comprises adding an extracting agent to extract the slurry obtained in the step 2) or the step 3), and the extract phase is recycled after being filtered,
wherein the extractant is one or more of phosphorus-containing organic extractant, ion-exchange neutral phosphorus-type extractant and acidic phosphorus-type extractant, and the extractant is phosphorus-containing organic extractant and is mainly selected from ion-exchange neutral phosphorus-type extractants (such as TOPO and P)350Or TBP) or acidic phosphorus type extractants (e.g. P)204,P507). The pH regulator is H2SO4CaO or Ca (OH)2. The foaming agent is a pinitol substance. The mass ratio of the extracting agent to the phosphogypsum is 5:1-0.2: 1. The mass ratio is more than 5:1, which greatly wastes the extractant and increases the operation cost, and less than 0.2:1 reduces the purification effect.
Preferably, the reaction temperature in the step 2) is 20-100 ℃, and the reaction time is 15-120 min; concentrating the slurry after 15-120 minutes and recovering acid; and in the step 3), the reaction temperature is 20-100 ℃, and the reaction time is 15-120 min.
Preferably, the gravity separation operation in the step 4) includes one or more of centrifugal washing separation and impurity removal of the hydrocyclone group, impurity removal of the high-frequency vibration fine screen, impurity removal of the table, impurity removal of the jigging, impurity removal of the classification box and impurity removal of the spiral chute.
Preferably, the step 5) further comprises adding a pH regulator, wherein the dosage of the pH regulator is 0.1-10 kg/t; meanwhile, step 5) washes the filter cake to be between weak acid and weak alkaline.
Preferably, the washing water can be reused for preparing the sulfuric acid solution for recycling.
The invention provides a combined process of phosphogypsum flotation/extraction desilication and decarburization and impurity removal and whitening by combining acid leaching and gravity separation. After the phosphogypsum is crushed, screened, ground and graded, and size mixing is carried out, a leaching agent, a regulator, a collecting agent, a foaming agent and an extracting agent are quantitatively added according to the characteristics of the incoming materials in a specific order for dephosphorization, defluorination and decarburization flotation/extraction, and the insoluble impurities such as silicon and iron and the like and the calcium sulfate target components such as the water phase impurities are further separated according to the granularity or density difference by gravity separation process equipment such as hydrocyclone centrifugation, high-frequency fine screen washing and the like at the tail end of the working procedure.
The method for preparing high-purity anhydrous calcium sulfate from phosphogypsum under an acidic condition is characterized by comprising the following steps of firstly, washing or roughly selecting phosphogypsum raw materials processed to meet a certain granularity requirement by flotation so as to separate partial carbon-based impurities and soluble impurities from gypsum, then, carrying out acid leaching on rough concentrates by sulfuric acid to fully dissolve acid-soluble impurities and some inclusion structures in phosphogypsum particles with certain fineness, thereby fully exposing acid-insoluble impurities originally wrapped in the phosphogypsum, and then, carrying out foam flotation or double-liquid flotation selection operation by using a collecting agent and a foaming agent to timely capture the acid-insoluble impurities (such as organic impurities or insoluble phosphorus) to an organic phase or a foam phase; meanwhile, according to the specific chemical and mineralogical characteristics of the phosphogypsum, an extracting agent can be used for extracting other impurities in the phosphogypsum in an auxiliary manner; and finally, simultaneously carrying out high-speed washing or centrifugal separation on the slurry subjected to impurity removal and filtration under an alkaline or neutral condition, so that most of residual inorganic impurities and organic impurities in the phosphogypsum can be removed simultaneously, and the high-quality anhydrous calcium sulfate concentrate is prepared. And (3) outside the main flow, carrying out flotation or gravity scavenging operation on the impurity products in the steps by an auxiliary flow to obtain calcium sulfate products with different qualities.
Because the phosphogypsum contains a large amount of inorganic impurities and organic impurities, and the surface chemical properties and the specific gravity and other physical properties of the phosphogypsum are greatly different, the conventional method for removing impurities by adopting a single process usually eliminates the long negative, so that the whiteness or the purity are hardly considered. The organic impurities in the phosphogypsum mainly come from apatite symbiotic carbon-containing minerals mixed in surrounding rocks in a mining link in the process of phosphorite production and carbonization of apatite flotation reagents added in the process of mineral separation in the subsequent phosphorus chemical process, the carbon-based impurities are attached to the surface of the phosphogypsum and are difficult to remove by washing, and can be usually removed only by high-temperature calcination, but the calcination not only has high energy consumption, but also can not effectively remove inorganic impurities such as quartz and ferric oxide in the phosphogypsum, and the final gypsum product can be reddened by the iron-containing impurities in the calcination process.
According to the invention, a large number of researches show that once the carbon-based impurities and other fluorine and phosphorus insoluble impurities are subjected to monomer dissociation by a crushing, ore grinding or acid leaching method, the carbon-based impurities and other fluorine and phosphorus insoluble impurities can be easily separated from a gypsum phase (water phase) by a collecting agent or an extracting agent and transferred into a bubble layer or an organic layer. And then the organic filtrate for filtering impurities and the acid liquor filtered out from the rough concentrate can be recycled, the rough concentrate is subjected to size mixing and then enters a hydrocyclone centrifugal field to complete the physical removal of silicon and iron insoluble impurities, and meanwhile, the washing and filtering of the residual water soluble impurities are completed.
The whiteness of the anhydrous calcium sulfate product obtained by the method is over 90, and the purity of the calcium sulfate is over 99%.
Compared with the prior art, the invention has the advantages that:
on one hand, inorganic impurities in phosphogypsum are decomposed by sulfuric acid leaching, and meanwhile, indissolvable organic impurities in the phosphogypsum are exposed, on the other hand, a small amount of flotation reagent is adopted to separate indissolvable impurities in the phosphogypsum in time by a physical method, meanwhile, according to the mineralogical characteristics, an extracting agent is adopted to cooperatively collect and separate the impurities if necessary, and finally, gravity separation equipment such as a multistage cyclone or a fine sieve is used to carry out final washing and centrifugal separation on rough concentrate to remove insoluble inorganic impurities, so that almost all impurities in the phosphogypsum are efficiently removed.
In an acidic environment, a hydrocarbon collecting agent and a phosphorus type extracting agent are combined for synergistic action to remove impurities, and the purification and separation are enhanced by combining a gravity separation washing method under a neutral condition; the extractant and the collector are convenient to recycle; the acid-base pH regulator does not introduce new impurities; the sulfuric acid filtrate and the organic phase such as the flotation agent/extraction agent can be recycled. The impurity removal process is a normal temperature/low temperature/normal pressure process, the used medicament is cheap and easy to obtain or is convenient to recycle, the process combination has strong adaptability to the source of the phosphogypsum, and a technical support is provided for the industrial application of the phosphogypsum.
The method can realize the purpose of preparing high-quality anhydrous calcium sulfate products from the phosphogypsum waste residues, has flexible process combination, finds new cheap raw materials for increasing application requirements of calcium sulfate, and has good economic benefit and wide industrial application prospect; meanwhile, the reduction and the harmlessness of the bulk industrial waste are realized, and the method has good social benefits.
Drawings
FIG. 1 is a process flow diagram of the present invention;
FIG. 2a is a microscopic image of the original sample of the present invention, wherein black is the impurity fraction;
figure 2b is a microscopic topography (100X) of the purified phosphogypsum product of example 1 according to the invention;
FIG. 3a is a microscopic topography of an isolated contaminant according to the present invention;
figure 3b is a microscopic topography (200X) of the purified phosphogypsum product of example 3 of the present invention.
Detailed Description
The present invention will be further described with reference to the following specific examples.
The method for removing impurities and whitening ardealite specifically comprises the following steps:
(1) adjusting the particle size of the phosphogypsum to a specified fineness, and then carrying out water washing and flotation roughing (prefloating);
(2) putting the phosphogypsum obtained in the step (1) and sulfuric acid into a reaction kettle according to a certain mass ratio, stirring, heating and keeping the temperature of slurry according to certain process requirements, concentrating the slurry after 15-120 minutes, and recovering acid;
(3) adding a flotation collector into the slurry obtained in the step (2), and adding a foaming agent and a pH regulator according to requirements for size mixing.
(4) And (3) after the prepared slurry is uniformly stirred, performing foam or double-liquid flotation separation: concentrating and separating a lower slurry layer; separating the upper layer organic phase, removing impurities and recycling;
(5) extracting and standing the slurry obtained in the step (2) or (4) by using an extracting agent if necessary according to the process requirement, and filtering an extract phase for recycling;
(6) feeding the purified slurry obtained in (4) or (5) into a gravity separation operation such as a hydrocyclone unit for centrifugal washing separation and impurity removal or a high-frequency vibration fine screen for impurity removal (the gravity separation process or equipment also includes but is not limited to other gravity separation processes such as a shaking table, a jigging, a classification box or a spiral chute);
(7) filtering the overflow product in the step (6), taking out a filter cake, and adding a pH regulator to neutralize the filter cake if necessary;
(8) and washing the filter cake, drying and crushing to obtain the finished product of purified gypsum.
Preferably, the phosphogypsum in the step (1) is industrial waste residue phosphogypsum generated in the industrial production process of wet-process phosphoric acid.
Preferably, the operation temperature in the steps (2), (3) and (4) is 20-100 ℃, and the reaction time is 15-120 min. The reaction rate can be reduced due to supercooling of the temperature, the product quality is influenced, heat energy is wasted due to overhigh temperature, and great difficulty is brought to equipment, heat preservation and operation, so that the temperature range is 20-100 ℃. The time setting is also optimized according to the process conditions: the reaction time is too short, the reaction is not completely carried out, the reaction is too long, and the consumption is increased, so the range of the reaction time selected by the invention is 15-120 min.
Preferably, the organic phase obtained in step (4) or (5) is filtered to separate the liquid-phase chemical and the solid-phase residue, the chemical can be reused in step (3) or (5) for recycling, and the solid-phase residue phase can be further extracted and separated or used as fuel.
According to the chemical composition and the process mineralogy characteristics of the phosphogypsum, the flexible combination of 2 to 4 working procedures in the combined flow is selected, namely, the aims of purifying and whitening the phosphogypsum are achieved through the combined action of acid leaching, flotation, extraction and gravity separation. The anhydrous calcium sulfate product with high purity and whiteness is prepared.
The invention adopts a method combining acid leaching, flotation, extraction, cyclone and fine sieve to simultaneously remove organic matters and inorganic impurities such as SiO in phosphogypsum by comprehensively utilizing solution chemical, surface chemical and physical methods at lower temperature2And the like, and the high-whiteness and high-purity anhydrous calcium sulfate can be prepared, and the acidic aqueous solution and the organic agent can be recycled, so that the economic, simple, convenient, high-efficiency and high-quality purification of the phosphogypsum is realized.
Example 1
The chemical components of the dry basis of phosphogypsum of a certain enterprise are shown in the following table 1.
TABLE 1 phosphogypsum dry base chemical composition
| Composition (I) | SO3 | CaO | SiO2 | P2O5 | Al2O3 | Fe2O3 | K2O | TiO2 | MgO | SrO | Na2O | V2O5 | Cl |
| Content% | 56.40 | 37.15 | 4.63 | 0.79 | 0.36 | 0.23 | 0.16 | 0.09 | 0.08 | 0.046 | 0.045 | 0.024 | - |
1. Mixing phosphogypsum and 35% sulfuric acid in a mass ratio of 1: 1.5 putting into a reaction kettle, and stirring;
2. heating to 85 ℃, and keeping for 1.5 hours;
3. adding a collecting agent, wherein the ratio of phosphogypsum is 1: 2;
4. after being stirred evenly, the mixture is kept stand to separate a lower slurry layer;
5. the upper layer is filtered to remove impurities and then recycled;
6. filtering the lower layer slurry and washing to be neutral; recycling the acidic filtrate;
7. and washing the filter cake, drying and crushing to obtain the finished product of purified gypsum.
The chemical composition of the resulting calcium sulfate product is shown in table 2 below.
TABLE 2 calcium sulfate product chemistry
It can be seen that most of the impurities have been removed, while the blue whiteness of the sample is 88.7, while the hunter whiteness exceeds 90. With SO3+CaO>99 percent of the detection report shows that the product is mainly anhydrous calcium sulfate, phosphorus is difficult to detect, the fluorine content is lower than 1 order of magnitude of national standard, and the product reaches the national I-grade phosphogypsum standard. The under-mirror morphology of phosphogypsum before and after purification is shown in figure 2.
Example 2
Chemical compositions of phosphogypsum dry-based impurities, calculated as oxides, of another enterprise are shown in table 3 below.
TABLE 3 chemical composition of phosphogypsum dry base impurities by oxides
| Composition (I) | SiO2 | P2O5 | Al2O3 | Fe2O3 | K2O | TiO2 | MgO | SrO | Cl |
| Content% | 3.82 | 0.65 | 0.24 | 0.12 | 0.12 | 0.05 | 0.05 | 0.02 | 0.01 |
1. Mixing phosphogypsum and 30% sulfuric acid in a mass ratio of 1: 3, putting into a reaction kettle, and stirring;
2. heating to 90 ℃ and keeping for 1 hour;
3. adding a collecting agent, wherein the ratio of phosphogypsum is 1: 3;
4. after being stirred evenly, the mixture is kept stand to separate a lower slurry layer;
5. the upper layer is filtered to remove impurities and then recycled;
6. adding an extracting agent into the lower-layer slurry for continuous extraction, wherein the proportion of phosphogypsum is 1: 5;
7. the upper layer is filtered to remove impurities and then recycled;
8. filtering the lower layer slurry and washing to be neutral; recycling the acidic filtrate;
9. and washing the filter cake, drying and crushing to obtain the finished product of purified gypsum.
The impurity levels in the purified calcium sulfate product are shown in table 4 below.
TABLE 4 impurity content in calcium sulfate product after purification
| Composition (I) | SiO2 | P2O5 | Al2O3 | Fe2O3 | K2O | TiO2 | MgO | SrO | Cl |
| Content% | 0.058 | 0.025 | 0.019 | 0.008 | 0.007 | 0.043 | - | 0.043 | - |
It can be seen that most of the impurities of silicon, phosphorus and iron are removed, the blue light whiteness of the sample is 88.9, and the Hunter whiteness exceeds 90. With SO3+CaO>99 percent of the product is mainly anhydrous calcium sulfate, and reaches the national grade I phosphogypsum standard.
Example 3
The blue light whiteness of fresh phosphogypsum from a certain phosphoric acid plant is 25-30, the scheme related by the process is adopted to carry out impurity removal and purification treatment:
1. pre-screening and grading the phosphogypsum according to the granularity;
2. washing the product with qualified granularity and performing flotation roughing (the dosage of the flotation reagent is 8-40kg/t dry ore);
3. carrying out heating and normal-pressure acid leaching on the flotation rough concentrate, and adding a small amount of a harvest aid to separate and enrich impurities in time;
4. after size mixing, pulp obtained by acid leaching is subjected to flotation and fine selection (the dosage of flotation reagents is 1-14kg/t dry ore);
5. carrying out flotation scavenging on the impurity products obtained in each step, and recovering calcium sulfate products mixed in the impurities;
6. and filtering the calcium sulfate concentrate product, washing a filter cake, drying, and crushing to obtain the finished product purified gypsum.
The phosphorus content in the purified phosphogypsum product sample is extremely low, the fluorine content is between 0.01 and 0.02 percent, and the phosphogypsum product sample reaches the harmless standard. The blue-light whiteness of the phosphogypsum in the flotation and selection section is improved to 90, and the blue-light whiteness of the phosphogypsum in the flotation and scavenging section also reaches 82.
The shapes under the mirror of the impurities separated by purification and the purified product are shown in figure 3.
Finally, it should be noted that the above embodiments are only used for illustrating the technical solutions of the present invention and are not limited. Although the present invention has been described in detail with reference to the embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the spirit and scope of the invention as defined in the appended claims.
Claims (10)
1. An impurity-removing and whitening method of phosphogypsum comprises the following steps:
1) performing fineness rough machining on the phosphogypsum raw material;
2) acid leaching the phosphogypsum obtained in the step 1) by using sulfuric acid, heating and keeping the temperature constant to obtain a material;
3) adding the material obtained in the step 2) into a flotation agent, and performing flotation, concentration and separation;
4) feeding the slurry obtained in the step 3) after flotation separation into gravity separation operation for impurity removal to obtain concentrate;
5) filtering the concentrate obtained in the step 4), washing a filter cake, drying, and crushing to obtain the finished product of purified gypsum.
2. The method of claim 1, further comprising the step of adding the roughed product to a flotation agent for prefloating in step 1).
3. The method of claim 2, wherein the flotation agent of step 1) comprises one or more of a collector, a frother and a pH adjuster, preferably the collector comprises an aliphatic hydrocarbon and/or an aromatic hydrocarbon; the foaming agent is a pinitol substance; the pH regulator comprises H2SO4CaO and Ca (OH)2One or more than two of the above; the dosage of the collecting agent is 1-60kg/t, and the dosage of the pH regulator is 0.1-10 kg/t.
4. Method according to claim 1, characterized in that step 3) the flotationThe selecting agent comprises one or more than two of collecting agent, foaming agent and pH adjusting agent, preferably, the collecting agent comprises aliphatic hydrocarbon and/or aromatic hydrocarbon; the foaming agent is a pinitol substance; the pH regulator comprises H2SO4CaO and Ca (OH)2One or more than two of the above; wherein the dosage of the collecting agent is 1-60kg/t, and the dosage of the pH regulator is 0.1-10 kg/t.
5. The method according to claim 1, wherein the mass concentration of the sulfuric acid solution in the step 2) is 30-50%, and the liquid-solid mass ratio of the sulfuric acid solution to the phosphogypsum is 1.5:1-7: 1.
6. The method according to claim 1 or 4, wherein the flotation separation in step 3) comprises froth separation or two-liquid flotation separation, and the lower slurry layer is concentrated and separated; separating the upper layer organic phase, removing impurities, and recycling, wherein in the foam flotation separation, the using amount of a collecting agent is 1-60kg/t, and the using amount of a foaming agent is 0.05-8 kg/t; in the double-liquid flotation separation, the mass ratio of the flotation agent to the phosphogypsum is 5:1-2: 1.
7. The method of claim 1, characterized in that step 2) or step 3) further comprises adding an extractant to extract and assist separation of the slurry obtained in step 2) or step 3), the extract phase is recycled after filtration,
wherein the extracting agent is one or more than two of a phosphorus-containing organic extracting agent, an ion exchange neutral phosphorus type extracting agent and an acidic phosphorus type extracting agent, and the mass ratio of the extracting agent to the phosphogypsum is 5:1-0.2: 1.
8. The method according to claim 1, wherein the reaction temperature in the step 2) is 20-100 ℃, and the reaction time is 15-120 min; concentrating the slurry after 15-120 minutes and recovering acid; and in the step 3), the reaction temperature is 20-100 ℃, and the reaction time is 15-120 min.
9. The method according to claim 1, wherein the gravity separation operation in step 4) comprises one or more of centrifugal washing separation and impurity removal by a hydrocyclone group, impurity removal by a high-frequency vibration fine screen, impurity removal by a table, jigging impurity removal, classification box impurity removal and spiral chute impurity removal.
10. The method according to claim 1, wherein the step 5) further comprises adding a pH adjusting agent in an amount of 0.1 to 10 kg/t; meanwhile, step 5) washes the filter cake to be between weak acid and weak alkaline.
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| CN111545342A (en) * | 2020-05-15 | 2020-08-18 | 武汉格物致知矿业有限公司 | Method for purifying phosphogypsum based on flotation column and gravity separation column with filler |
| CN112429991A (en) * | 2021-01-08 | 2021-03-02 | 瓮福（集团）有限责任公司 | Device for flotation and water washing of phosphogypsum |
| CN112723770A (en) * | 2021-01-07 | 2021-04-30 | 湖北新洋丰新型建材科技有限公司 | Purification method of byproduct phosphogypsum of wet-process phosphoric acid |
| CN113072046A (en) * | 2021-04-09 | 2021-07-06 | 郑州大学 | Method for removing impurities and improving whiteness of phosphogypsum through flotation method |
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| CN114162845A (en) * | 2021-12-29 | 2022-03-11 | 贵州大学 | Method for preparing micron-sized anhydrous calcium sulfate by using phosphogypsum |
| CN114380318A (en) * | 2022-03-07 | 2022-04-22 | 武汉润豫科技有限公司 | Ardealite impurity removal and purification system |
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