A method for purifying solid waste gypsum by grinding and flotation

Abstract

The present invention discloses a method for purifying solid waste gypsum by grinding and flotation, comprising the following steps: (1) grinding the solid waste gypsum; (2) mixing the ground solid waste gypsum with water, stirring to form a gypsum suspension slurry, adding an adjusting agent to adjust the pH, sequentially adding a reverse flotation collector and a frother, performing reverse flotation, and obtaining reverse flotation concentrate I and tailings I; (3) adjusting the pH value of the reverse flotation concentrate I slurry, sequentially adding an inhibitor and a forward flotation collector, performing forward flotation, and obtaining concentrate II and tailings II. The present invention can improve the whiteness of the solid waste gypsum from 20% to 46% to 65% to 80% by grinding, removing impurities by reverse flotation, and recovering gypsum by forward flotation, the content of calcium sulfate dihydrate (CaSO4·2H2O) can reach more than 93%, and the yield of gypsum concentrate can reach more than 70%, thereby realizing efficient purification of solid waste gypsum.

Description

Technical Field

[0001] The invention belongs to the technical field of industrial by-product gypsum solid waste treatment, and in particular relates to a method for purifying solid waste gypsum through grinding and flotation. Background Art

[0002] Solid waste gypsum is a by-product produced in industrial processes, including phosphogypsum produced by the phosphorus chemical industry, desulfurization gypsum produced by flue gas desulfurization in steel, power plants and non-ferrous metal smelting, titanium gypsum produced by the titanium dioxide industry, and lithium gypsum produced by lithium extraction from spodumene by sulfuric acid roasting. This type of gypsum often contains a high content of calcium sulfate dihydrate (CaSO4·2H2O), which can theoretically replace traditional gypsum, but the presence of impurities has seriously restricted the market application of this type of gypsum. Taking phosphogypsum as an example, phosphogypsum is a solid waste produced by the wet production of phosphoric acid. The main component is calcium sulfate dihydrate (CaSO4·2H2O), with a content of more than 85%. It also contains a large amount of impurities such as phosphorus, fluorine, and organic matter. It is a recycled gypsum resource with great potential. Every ton of wet phosphoric acid produced will produce about 4-5 tons of phosphogypsum. At present, my country has a large stockpile of phosphogypsum. Due to the influence of impurities, a large amount of phosphogypsum cannot be effectively utilized as a resource, and the utilization rate is only about 50%. The phosphogypsum produced by the wet phosphoric acid process often carries organic matter from the original ore and organic flotation agents. These organic substances will be carbonized during sulfuric acid extraction, making the phosphogypsum light gray or black. At the same time, a small amount of SiO2 and metal ion impurities such as iron, magnesium, and aluminum are also mixed in the phosphogypsum. These factors lead to a low whiteness of the phosphogypsum, making it more difficult to recycle the phosphogypsum. Most solid waste gypsum is stored or landfilled because it cannot be recycled. This not only occupies a large amount of land, but the impurities contained in the stored solid waste gypsum are very likely to pollute the surrounding atmosphere, water bodies, and soil, thereby endangering human health and the normal survival of other organisms.

[0003] There are many reasons for the low utilization rate of solid waste gypsum. First, the presence of a large amount of impurities seriously limits the quality and utilization of solid waste gypsum products. Secondly, the low added value of solid waste gypsum products greatly restricts the sales radius of the product. Finally, the reuse of solid waste gypsum cannot make profits for enterprises in the short term. Therefore, reducing the impurity content in solid waste gypsum is an urgent task for large-scale resource utilization of solid waste gypsum. CN117920466A discloses a method for synchronous desiliconization and organic matter removal of phosphogypsum co-reverse flotation, using dimethyl tertiary amine as a collector and an alcohol foaming agent. After a one-step co-reverse flotation process, a concentrate with SiO2 content reduced to 2.358% and whiteness of 57.85 in phosphogypsum can be obtained. However, there are problems such as long flotation process, large dosage of reagents, and limited increase in whiteness and purity of calcium sulfate dihydrate. CN117259017A discloses a flotation inhibitor for whitening and improving the quality of phosphogypsum, and its preparation method and application. However, the impurity removal agent of the method is a compound agent of inorganic inhibitors, organic small molecule inhibitors, polysaccharide inhibitors, polyphenol inhibitors and polymer inhibitors. There are many types of agents and the process is complicated. In addition, the flotation process of "one reverse and two positive" is adopted, which has the problems of complex process, long time consumption, high cost, etc. CN113245068A discloses a flotation collector for improving the whiteness of phosphogypsum by flotation impurity removal and its application. The main raw materials are vinyl trimethoxysilane, ether amine, fatty alcohol, and dodecylamine. It can effectively remove organic matter in phosphogypsum and improve the whiteness of phosphogypsum. However, the removal rate of mineral impurities such as SiO2 is low, resulting in low purity of the by-product phosphogypsum.

[0004] In summary, a variety of patented technologies have been published for the removal of impurities and whitening of solid waste gypsum. In order to efficiently improve the effect of removing impurities and whitening of solid waste gypsum, it is extremely important to find a simple, low-cost and effective impurity removal process for the comprehensive utilization of solid waste gypsum. Summary of the invention

[0005] The technical problem to be solved by the present invention is to overcome the shortcomings and defects mentioned in the above background technology, and provide a method for efficiently purifying solid waste gypsum by grinding and flotation, which solves the problems of poor effect of existing solid waste gypsum impurity removal and whitening process, complex process, many types of flotation agents, large dosage and high cost.

[0006] In order to solve the above technical problems, the technical solution proposed by the present invention is:

[0007] A method for purifying solid waste gypsum by grinding and flotation, comprising the following steps:

[0008] (1) Grinding solid waste gypsum;

[0009] (2) mixing the solid waste gypsum after grinding with water, stirring to form a gypsum suspension slurry, adding an adjusting agent to adjust the pH, and sequentially adding a reverse flotation collector and a frother to perform reverse flotation to obtain reverse flotation concentrate I and tailings I;

[0010] The reverse flotation collector is one or more of waste lubricating oil, waste engine oil, waste hydraulic oil and waste transformer oil;

[0011] (3) adjusting the pH value of the reverse flotation concentrate I pulp, adding a depressant and a forward flotation collector in sequence, and performing forward flotation to obtain concentrate II and tailings II;

[0012] The positive flotation collector is one or more of sodium laureth sulfate, sodium N-lauroyl sarcosine, sodium lauroyl amphoacetate, sodium lauroyl glutamate, lauroyl lysine, and alkyl polysaccharide.

[0013] As a further improvement, the method further includes the following steps: (4) the concentrate II after flotation separation is subjected to solid-liquid separation and then dried.

[0014] As a further improvement, the solid waste gypsum in step (1) includes one or more of phosphogypsum, desulfurized gypsum and lithium gypsum; and / or, the grinding is performed by placing the solid waste gypsum in a vibrating mill for grinding for 1-10 minutes.

[0015] As a further improvement, the solid mass fraction in the gypsum suspension slurry in step (2) is 20-35wt%.

[0016] As a further improvement, in step (2), the pH is adjusted to 1.5-4.0.

[0017] As a further improvement, the reverse flotation collector in step (2) is waste lubricating oil and / or waste engine oil, and the amount of the reverse flotation collector used is 20-500 g / t.

[0018] As a further improvement, in step (3), the pH value of the reverse flotation concentrate I slurry is adjusted to 6-8.

[0019] As a further improvement, the alkyl polysaccharide in step (3) is one or more of lauryl glucoside, octyl glucoside, decyl glucoside, coconut glucoside, n-hexyl glucoside, fatty alcohol polyoxyethylene ether glucoside, and isooctyl glucoside.

[0020] As a further improvement, the positive flotation collector in step (3) is a compound of sodium N-lauroyl sarcosinate and alkyl polysaccharide, wherein the mass fraction of sodium N-lauroyl sarcosinate in the compound is 75% to 90%.

[0021] As a further improvement, the dosage of the positive flotation collector in step (3) is 50-450 g / t.

[0022] The main function of grinding in the present invention is to fully release the impurities in the gypsum inclusions. The reverse flotation process mainly floats the solid colored impurities in the solid waste gypsum, including colored organic matter and impurities such as aluminosilicates that adsorb colored matter. The forward flotation process mainly floats the dihydrate gypsum product.

[0023] In the process of positive flotation, the carboxyl and amide groups in sodium N-lauroyl sarcosinate can form coordination bonds with the calcium points on the surface of the mineral, resulting in the generation of chemical adsorption. Therefore, it is a good selective collector for the flotation of calcium-containing minerals and has foaming properties. Alkyl polysaccharides are a type of non-ionic surfactant formed by connecting fatty alcohols and glucose through glycosidic bonds. Their molecular structure contains hydrophilic glucose groups and hydrophobic alkyl chains. The hydrophilic glucose molecules contain multiple hydroxyl groups (–OH), which can interact with the calcium points on the surface of the calcium-containing minerals through hydrogen bonds or coordination bonds, while the hydrophobic alkyl chains form a hydrophobic surface outward to combine with bubbles, thereby floating the calcium-containing minerals and separating the calcium-containing minerals from other minerals. Relatively speaking, sodium N-lauroyl sarcosinate has stronger flotation selectivity for calcium-containing minerals, but alkyl polysaccharides have good dispersing ability, which can effectively prevent the agglomeration of fine particles in the slurry, maintain the stability of the slurry, and promote the separation of mineral particles; at the same time, during the flotation process, alkyl polysaccharides can adjust the properties of the foam to form moderate and stable foam, which is beneficial to the attachment and separation of mineral particles. Therefore, the addition of alkyl polysaccharides can form a good synergistic effect with sodium N-lauroyl sarcosinate and promote the flotation separation of calcium-containing minerals.

[0024] The present invention uses a grinding and flotation method to efficiently remove impurities in solid waste gypsum and purify solid waste gypsum. Compared with the prior art, the present invention has the following beneficial effects:

[0025] 1) The process flow of the present invention is simple and easy to operate;

[0026] 2) The cost of the agent of the present invention is low and the efficiency of impurity removal is high;

[0027] 3) The reverse flotation agent of the present invention uses waste oil, etc., which can reduce the emission of harmful substances, and at the same time realize the secondary utilization of waste resources, reduce production costs, and improve resource utilization efficiency;

[0028] 4) The present invention can improve the whiteness of solid waste gypsum from 20% to 46% to 65% to 80% through grinding, reverse flotation to remove impurities and forward flotation to recover gypsum, the content of calcium sulfate dihydrate (CaSO4·2H2O) can reach more than 93%, and the yield of gypsum concentrate can reach more than 70%, thereby realizing efficient purification of solid waste gypsum. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0030] Figure 1 It is a process flow chart of the present invention. DETAILED DESCRIPTION

[0031] In order to facilitate the understanding of the present invention, the present invention will be described more comprehensively and carefully in combination with preferred embodiments below, but the protection scope of the present invention is not limited to the following specific embodiments.

[0032] Unless otherwise defined, all professional terms used below have the same meanings as those generally understood by those skilled in the art. The professional terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention.

[0033] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or prepared by existing methods.

[0034] like Figure 1 As shown, the method of the present invention for efficiently purifying solid waste gypsum by grinding and flotation comprises the following steps:

[0035] (1) Grinding solid waste gypsum.

[0036] The solid waste gypsum of the present invention comprises one or more of phosphogypsum produced by the phosphorus chemical industry, desulfurization gypsum produced by flue gas desulfurization, and lithium gypsum produced in the spodumene smelting process, and the mass fraction of calcium sulfate dihydrate (CaSO4·2H2O) in the solid waste gypsum is ≥75%.

[0037] In some embodiments, the solid waste gypsum is placed in a vibrating mill for grinding, and the grinding time is 1-10 minutes, preferably 2-5 minutes.

[0038] (2) The solid waste gypsum after grinding is mixed with water and stirred to form a gypsum suspension slurry, an adjusting agent is added to adjust the pH value, and a reverse flotation collector and a frother are added in sequence to perform reverse flotation to obtain reverse flotation concentrate I and tailings I.

[0039] The adjusting agent is a conventional pH adjusting agent in the art, such as an acid such as sulfuric acid.

[0040] In some embodiments, the solid mass fraction in the gypsum suspension slurry is 20-35wt%, preferably 25-30wt%.

[0041] In some embodiments, the pH of the gypsum suspension slurry is adjusted to 1.5-4.0, preferably 1.5-2.5.

[0042] In some embodiments, the reverse flotation collector is one or more of waste lubricating oil, waste engine oil, waste hydraulic oil, and waste transformer oil, and is more preferably one or more of waste lubricating oil and waste engine oil. It is more preferably waste low-viscosity engine oil, and is more preferably waste engine oil with grades of 0W-20, 0W-30, 5W-20, and 5W-30. The amount of the reverse flotation collector is 20-500 g / t.

[0043] In some embodiments, the foaming agent is one or more of pine oil, octanol, methyl isobutyl carbinol (MIBC), triethoxybutane (TEB), and polypropylene glycol ether. The amount of the foaming agent is 50-450 g / t.

[0044] In some embodiments, the stirring speed is preferably 1500-2100 rpm when adding the reagent. After adding the frother and stirring, reverse flotation is performed, air is added, the flow rate is controlled at 2-3 L / min, and the scraping flotation is performed for 2-4 min.

[0045] (3) Adjust the pH value of the reverse flotation concentrate I pulp, add a depressant and a forward flotation collector in sequence, and perform forward flotation to obtain concentrate II and tailings II.

[0046] In some embodiments, the pH value of the reverse flotation concentrate I slurry is adjusted to 6-8, preferably 6.5-7.5. The pH of the reverse flotation concentrate I can be adjusted to the above range by conventional pH adjusters in the art, such as alkalis such as sodium hydroxide.

[0047] In some embodiments, the positive flotation collector is one or more of sodium laureth sulfate, sodium N-lauroyl sarcosinate, sodium lauroyl amphoacetate, sodium lauroyl glutamate, lauroyl lysine, and alkyl polysaccharides, wherein the alkyl polysaccharides are one or more of lauryl glucoside, octyl glucoside, decyl glucoside, coconut glucoside, n-hexyl glucoside, fatty alcohol polyoxyethylene ether glucoside, and isooctyl glucoside. Preferably, sodium N-lauroyl sarcosinate. More preferably, it is a compound agent of sodium N-lauroyl sarcosinate and alkyl polysaccharides, wherein the mass fraction of sodium N-lauroyl sarcosinate in the compound agent is 75% to 90%. The dosage of the positive flotation collector is 50-450g / t.

[0048] In some embodiments, the inhibitor is water glass, starch, dextrin, or carboxymethyl cellulose, and the amount used is 500 g / t to 2000 g / t.

[0049] In some embodiments, the stirring speed is preferably 1500-2100 rpm when adding the reagent. After adding the positive flotation collector and stirring, positive flotation is performed, air is added, the flow rate is controlled at 2-3 L / min, and the scraping flotation is performed for 2-4 min.

[0050] (4) After flotation separation, the concentrate II is subjected to solid-liquid separation and dried (the drying temperature is preferably 60°C) to obtain a high-purity solid waste gypsum product.

[0051] Example 1

[0052] First, phosphogypsum (CaSO4·2H2O content of 83.5%, SiO2 content of 3.6%, whiteness of 45.6%) was placed in a vibrating mill and ground for 2.0 min. Then, 400 mL of pure water and 100.0 g of ground phosphogypsum were added to the flotation tank to make its solid content reach 20%. The phosphogypsum suspension was formed by stirring. The pH of the slurry was adjusted to 2.0, stirring was started, and the stirring speed was 1700 rpm. Waste engine oil (grade 0W-20) was added at 80 g / t. After stirring for 3 min, MIBC was added. 300g / t, stirred for 5min, reverse flotation, then aerated and scraped bubbles were started at 2.5L / min, scraped bubbles for 3min, all black foam was scraped out, and reverse flotation concentrate I and tailings I were obtained; then the pH of the reverse flotation concentrate slurry was adjusted to 7, stirring was started, the stirring speed was 1700rpm, 1000g / t of water glass was added, stirred for 3min, and a compound agent of sodium N-lauroyl sarcosinate and lauryl glucoside (quality of sodium N-lauroyl sarcosinate: 1000g / t) was added. The fraction is 85%) 100g / t, after stirring for 3min, positive flotation is carried out, and then aeration and scraping are turned on at the same time, the aeration flow rate is 2.5L / min, and the scraping is carried out for 3min, and all white foam is scraped out to obtain concentrate II and tailings II; finally, concentrate II is immediately filtered and washed, and then transferred to an oven for drying at 60℃ with forced air to constant weight, and finally a high-purity gypsum product is obtained, wherein the yield of gypsum concentrate II is 81.4%, the whiteness of the gypsum product is 80.1%, and the content of calcium sulfate dihydrate is 93.5%.

[0053] Example 2

[0054] First, phosphogypsum (CaSO4·2H2O content of 83.5%, SiO2 content of 3.6%, whiteness of 45.6%) was placed in a vibrating mill and ground for 1.0 min. Then, 375 mL of pure water and 125.0 g of ground phosphogypsum were added to the flotation tank to make its solid content reach 25%. The phosphogypsum suspension was formed by stirring, and the pH of the slurry was adjusted to 2.5. The stirring was started at a stirring speed of 1700 rpm. Waste engine oil (grade 5W-30) was added at 150 g / t. After stirring for 3 min, MIBC was added. 300g / t, stirred for 5min, reverse flotation was carried out, then aeration was started and scraping was started at the same time, the aeration flow rate was 2.5L / min, the scraping was carried out for 3min, all the black foam was scraped out, and reverse flotation concentrate I and tailings I were obtained; then the pH of the reverse flotation concentrate slurry was adjusted to 6, stirring was started, the stirring speed was 1700rpm, 1500g / t of water glass was added, and after stirring for 3min, a compound agent of sodium N-lauroyl sarcosinate and n-hexyl glucoside (sodium N-lauroyl sarcosinate) was added. The mass fraction of 80%) was 200g / t, stirred for 3min, and then positive flotation was carried out. Then, aeration was started and the scraping was started at the same time. The aeration flow rate was 2.5L / min, and the scraping was carried out for 3min. All the white foam was scraped out to obtain concentrate II and tailings II. Finally, the concentrate II was separated from the solid and liquid, and moved into an oven to be dried at 60℃ with air blast to constant weight, and finally a high-purity gypsum product was obtained, of which the yield of gypsum concentrate II was 82.1%, the whiteness of the gypsum product was 79.8%, and the content of calcium sulfate dihydrate was 92.1%.

[0055] Example 3

[0056] First, phosphogypsum (CaSO4·2H2O content of 81.2%, SiO2 content of 3.9%, whiteness of 44.7%) was placed in a vibration mill and ground for 1.0 min. Then, 350 mL of pure water and 150.0 g of ground phosphogypsum were added to the flotation tank to make its solid content reach 30%. The phosphogypsum suspension was formed by stirring. The pH of the slurry was adjusted to 3.0, stirring was started, and the stirring speed was 2100 rpm. Waste engine oil (brand 0W-30) was added at 150 g / t. After stirring for 3 min, MIBC was added. 300g / t, stirred for 5min, reverse flotation, then aerated and started scraping bubbles at the same time, the aeration flow rate was 2.5L / min, scraped bubbles for 3min, all black foams were scraped out, and reverse flotation concentrate I and tailings I were obtained; then the pH of the reverse flotation concentrate slurry was adjusted to 8, stirring was started, the stirring speed was 1700rpm, 1500g / t of water glass was added, and after stirring for 3min, 200g / t of sodium N-lauroylsarcosinate was added, and after stirring for 3min, positive flotation was carried out, then aerated and started scraping bubbles at the same time, the aeration flow rate was 2.5L / min, scraped bubbles for 3min, all white foams were scraped out, and concentrate II and tailings II were obtained; finally, concentrate II was separated from solid and liquid, and moved into an oven to be dried at 60℃ with air blast to constant weight to obtain the final high-grade phosphogypsum, wherein the yield of gypsum concentrate II was 76.7%, the whiteness of the gypsum product was 76.3%, and the content of calcium sulfate dihydrate was 91.7%.

[0057] Example 4

[0058] First, lithium gypsum (CaSO4·2H2O content of 78.5%, SiO2 content of 6.33%, Al2O3 content of 11.4%, whiteness of 55.6%) was placed in a vibrating mill for grinding for 3.0 min. Then, 400 mL of pure water and 100.0 g of ground lithium gypsum were added to the flotation tank to make its solid content reach 20%. The suspension was stirred to form a lithium gypsum suspension. The pH of the slurry was adjusted to 2.0, stirring was started, and the stirring speed was 1700 rpm. 80 g / t of waste lubricating oil was added. After stirring for 3 min, 300 g / t of MIBC was added and stirred for 5 min for the first reverse flotation. Then, the scraping was started while aerating. The aeration flow rate was 2.5 L / min, and the scraping was performed for 3 min to scrape out all the yellow foam. 80 g / t of waste engine oil (grade 5W-20) was added again. After stirring for 3 min, MIBC was added. 300g / t, stirred for 5min, and then the second reverse flotation was carried out, and then the scraping was turned on at the same time of aeration, the aeration flow rate was 2.5L / min, the scraping was carried out for 3min, and all the yellow foam was scraped out to obtain concentrate I; then the pH of the reverse flotation concentrate slurry was adjusted to 6.5, stirring was turned on, the stirring speed was 1700rpm, 1000g / t of water glass was added, and after stirring for 3min, 300g / t of sodium lauroylamphoacetate was added, and after stirring for 3min, positive flotation was carried out, and then the scraping was turned on at the same time of aeration, the aeration flow rate was 2.5L / min, and the scraping was carried out for 3min, and all the white foam was scraped out to obtain concentrate II; finally, the concentrate II was filtered and washed, and it was moved into an oven and dried at 60℃ with air blast to constant weight, and finally a high-purity gypsum product was obtained, wherein the yield of gypsum concentrate II was 71.7%, the whiteness of the gypsum product was 73.5%, and the content of calcium sulfate dihydrate was 91.2%.

[0059] Example 5

[0060] First, lithium gypsum (CaSO4·2H2O content of 78.5%, SiO2 content of 6.33%, Al2O3 content of 11.4%, whiteness of 55.6%) was placed in a vibration mill and ground for 5.0 min. Then, 400 mL of pure water and 100.0 g of ground lithium gypsum were added to the flotation tank to make its solid content reach 20%. The suspension was stirred to form a lithium gypsum suspension. The pH of the slurry was adjusted to 2.0, stirring was started, and the stirring speed was 1700 rpm. 150 g / t of waste transformer oil was added. After stirring for 3 min, 300 g / t of MIBC was added and stirred for 5 min for the first reverse flotation. Subsequently, the scraping was started while aerating. The aeration flow rate was 2.5 L / min, and the scraping was performed for 3 min to scrape out all the yellow foam. 150 g / t of waste transformer oil was added again, and after stirring for 3 min, MIBC was added. 300g / t, stirred for 5min, carried out the second reverse flotation, then aerated and started scraping bubbles at the same time, the aeration flow rate was 2.5L / min, scraped bubbles for 3min, scraped out all yellow foam, and obtained concentrate I; then adjusted the pH of the reverse flotation concentrate slurry to 7, started stirring, the stirring speed was 1700rpm, added water glass 850g / t, stirred for 3min, added N-lauroyl sarcosine sodium 200g / t, stirred for 3min, carried out the first positive flotation, then aerated and started scraping bubbles at the same time, the aeration flow rate was 2.5L / min, scraped bubbles for 3min, scraped out white foam; added N-lauroyl sarcosine sodium 200g / t again After stirring for 3 minutes, the second positive flotation was carried out, and then aeration and scraping were started at the same time. The aeration flow rate was 2.5L / min, and the scraping was carried out for 3 minutes. All the white foam was scraped out to obtain concentrate II. Finally, the concentrate II was separated from the solid and liquid, and moved into an oven to be dried at 60°C with air blast to constant weight to obtain the final high-grade gypsum, of which the yield of gypsum concentrate II was 73.1%, the whiteness of the gypsum product was 73.2%, and the content of calcium sulfate dihydrate was 90.8%.

[0061] It can be seen from Examples 3 to 5 that the use of sodium N-lauroyl sarcosinate alone, or sodium lauroyl amphoacetate and sodium N-lauroyl sarcosinate as a positive flotation collector will affect the whiteness of the product, and the whiteness of the product is not as good as that of Examples 1 to 2 using a compound agent of sodium N-lauroyl sarcosinate and alkyl polysaccharide.

[0062] Example 6

[0063] The method and steps are the same as those in Example 5, except that 200 g / t of lauryl glucoside is added as the positive flotation collector. The yield of the obtained gypsum concentrate II is 70.9%, the whiteness of the gypsum product is 71.5%, and the content of calcium sulfate dihydrate is 89.9%.

[0064] It can be seen that when alkyl polysaccharide is used alone as a positive flotation collector, the whiteness of the product is also low and the content of calcium sulfate dihydrate is low. The combination of sodium N-lauroyl sarcosinate and alkyl polysaccharide produces a synergistic effect.

[0065] Comparative Example 1

[0066] The method and steps are the same as those in Example 1, except that the amount of waste engine oil added is 10 g / t, the yield of the obtained gypsum concentrate is 82.2%, the whiteness of the gypsum product is 64.7%, and the content of calcium sulfate dihydrate is 85.7%.

[0067] It can be seen that too low a dosage of waste oil will affect the product whiteness and calcium sulfate dihydrate content.

[0068] Comparative Example 2

[0069] The method and steps are the same as those in Example 1, except that the grinding process is not performed. The yield of the obtained gypsum concentrate is 83.2%, the whiteness of the gypsum product is 58.9%, and the content of calcium sulfate dihydrate is 80.3%.

[0070] It can be seen that grinding helps to improve the whiteness and content of calcium sulfate dihydrate in the product.

[0071] Comparative Example 3

[0072] The method and steps are the same as those in Example 1, except that 40 g / t of a compound agent of sodium N-lauroyl sarcosinate and n-hexyl glucoside (the mass fraction of sodium N-lauroyl sarcosinate is 80%) is added, and the yield of the obtained gypsum concentrate is 67.8%, the whiteness of the gypsum product is 78.2%, and the content of calcium sulfate dihydrate is 91.2%.

[0073] It can be seen that the amount of the compound agent of sodium N-lauroyl sarcosinate and n-hexyl glucoside added is too small, which affects the whiteness of the product.

[0074] Comparative Example 4

[0075] The method and steps are the same as those in Example 1, except that when the waste engine oil is replaced with sodium oleate, the yield of the obtained gypsum concentrate is 80.7%, the whiteness of the gypsum product is 65.3%, and the content of calcium sulfate dihydrate is 85.4%.

[0076] It can be seen that the reverse flotation collector using sodium oleate is not as good as waste oil in terms of product whiteness and calcium sulfate dihydrate content.

[0077] Comparative Example 5

[0078] The method and steps are the same as those in Example 2, except that the pH of the slurry during reverse flotation is 5, the yield of the obtained gypsum concentrate is 80.2%, the whiteness of the gypsum product is 60.2%, and the content of calcium sulfate dihydrate is 83.8%.

[0079] It can be seen that a reverse flotation pH that is too high will affect the product whiteness and calcium sulfate dihydrate content.

[0080] Comparative Example 6

[0081] Comparative Example 2, except that when the waste engine oil was replaced with kerosene, the yield of the obtained gypsum concentrate was 81.2%, the whiteness of the gypsum product was 66.7%, and the content of calcium sulfate dihydrate was 87.0%.

[0082] It can be seen that the reverse flotation collector using kerosene is not as good as waste engine oil in terms of product whiteness and calcium sulfate dihydrate content.

[0083] Comparative Example 7

[0084] The method and steps are the same as those in Example 4, except that the waste lubricating oil is replaced with sodium hydroxyoleate. The yield of the obtained gypsum concentrate is 70.8%, the whiteness of the gypsum product is 65.2%, and the content of calcium sulfate dihydrate is 84.7%.

[0085] It can be seen that the reverse flotation collector using sodium hydroxyoleate is not as good as the waste lubricating oil in terms of product whiteness and calcium sulfate dihydrate content.

[0086] Comparative Example 8

[0087] The method and steps are the same as those in Example 4, except that the pH of the slurry during positive flotation is 5, the yield of the obtained gypsum concentrate is 57.1%, the whiteness of the gypsum product is 43.2%, and the content of calcium sulfate dihydrate is 69.6%.

[0088] It can be seen that a too low pH value in positive flotation will affect the product whiteness and calcium sulfate dihydrate content.

[0089] The above is only a preferred embodiment of the present invention and does not limit the present invention in any form. Therefore, any simple modification, equivalent change and modification made to the above embodiment according to the technical essence of the present invention without departing from the content of the technical solution of the present invention shall fall within the scope of protection of the technical solution of the present invention.

Claims

1. A method for purifying solid waste gypsum by grinding and flotation, characterized in that: The steps include: (1) Grinding solid waste gypsum; (2) mixing the solid waste gypsum after grinding with water, stirring to form a gypsum suspension slurry, adding an adjusting agent to adjust the pH to 1.5-4.0, adding a reverse flotation collector and a frother in sequence, and performing reverse flotation to obtain reverse flotation concentrate I and tailings I; The reverse flotation collector is waste lubricating oil, and the amount of the reverse flotation collector is 20-500g / t; (3) Adjusting the pH value of the reverse flotation concentrate Ⅰ slurry to 6-8, adding a depressant and a forward flotation collector in sequence, and performing forward flotation to obtain concentrate Ⅱ and tailings Ⅱ; The positive flotation collector is a compound reagent of sodium N-lauroyl sarcosinate and alkyl polysaccharide, wherein the mass fraction of sodium N-lauroyl sarcosinate in the compound reagent is 75%-90%, and the dosage of the positive flotation collector is 50-450g / t.

2. The method for purifying solid waste gypsum by grinding and flotation according to claim 1, characterized in that: The method also includes the following steps: (4) solid-liquid separation of concentrate II after flotation separation, and then drying.

3. The method for purifying solid waste gypsum by grinding and flotation according to claim 1, characterized in that: The solid waste gypsum in step (1) comprises one or more of phosphogypsum, desulfurized gypsum and lithium gypsum; and / or the grinding is to grind the solid waste gypsum in a vibrating mill for 1-10 minutes.

4. The method for purifying solid waste gypsum by grinding and flotation according to claim 1 or 3, characterized in that: The solid mass fraction in the gypsum suspension slurry in step (2) is 20-35wt%.

5. The method for purifying solid waste gypsum by grinding and flotation according to claim 1, characterized in that: The alkyl polysaccharide in step (3) is one or more of lauryl glucoside, octyl glucoside, decyl glucoside, coconut glucoside, n-hexyl glucoside, fatty alcohol polyoxyethylene ether glucoside and isooctyl glucoside.

Images