阅读说明：本技术 一种湿法磷酸的副产磷石膏的提纯方法 (Purification method of byproduct phosphogypsum of wet-process phosphoric acid ) 是由 王良杰 李国海 贺军 余金涛 于 2021-01-07 设计创作，主要内容包括：一种湿法磷酸的副产磷石膏的提纯方法,它包括以下步骤：S1、浮选槽脱色：磷酸工序的副产磷石膏加水调节矿浆,按比例加入脱色药剂,溢流进入浮选槽；S2、跳汰重选柱脱硅:将S1中浮选槽得到的脱色磷石膏精矿浆补水,泵入脱硅重选柱跳汰分级,硅尾渣矿浆进入带式过滤机过滤,得到硅尾渣；顶部溢流精矿浆送去浓密过滤；S3、过滤水洗脱磷：将S2得到的脱硅后的磷石膏精矿浆泵入斜板浓密机浓密脱水,底流得到磷石膏精矿浆,再泵入带式过滤机进行过滤,洗涤后的滤饼排到仓库,得到精制磷石膏产品。本发明适用于大型工业化装置,能连续稳定可靠生产,对副产磷石膏适应性强,特别适应目前用低品质磷矿石的磷酸装置的副产磷石膏。(A method for purifying a byproduct phosphogypsum of wet-process phosphoric acid comprises the following steps: s1, decoloring in a flotation tank: adding water into the phosphogypsum byproduct of the phosphoric acid procedure to adjust the pulp, adding a decolorizing agent in proportion, and overflowing into a flotation tank; s2, desiliconizing the jigging gravity concentration column, namely replenishing water to the decolored phosphogypsum concentrate slurry obtained by the flotation tank in the S1, pumping the slurry into the desiliconizing gravity concentration column for jigging and grading, and filtering the silicon tailing slurry by a belt filter to obtain silicon tailings; the top overflow concentrate pulp is sent to be concentrated and filtered; s3, filtering, washing and dephosphorizing: pumping the desiliconized phosphogypsum concentrated pulp obtained in the step S2 into an inclined plate thickener for thickening and dewatering, obtaining phosphogypsum concentrated pulp from bottom flow, pumping the phosphogypsum concentrated pulp into a belt filter for filtering, and discharging a washed filter cake into a warehouse to obtain a refined phosphogypsum product. The invention is suitable for large-scale industrialized devices, can continuously, stably and reliably produce, has strong adaptability to the byproduct phosphogypsum, and is particularly suitable for the byproduct phosphogypsum of the current phosphoric acid device using low-quality phosphate ores.)

1. A method for purifying a byproduct phosphogypsum of wet-process phosphoric acid is characterized by comprising the following steps:

s1, decoloring in a flotation tank: adding water into the byproduct phosphogypsum in the phosphoric acid process to adjust the byproduct phosphogypsum into ore pulp with the mass concentration of 25-40%, pumping into a dosing stirring barrel, simultaneously adding a decolorizing agent in proportion, uniformly mixing, and overflowing into a flotation tank; after flotation treatment, the bottom material is decolorized concentrate and enters the next process, and the upper tailings are subjected to filter pressing by a membrane filter press to obtain decolorized tailings;

s2, desiliconizing a jigging gravity concentration column, namely, adjusting the decolored phosphogypsum concentrate slurry obtained from the flotation tank in S1 into a mass concentration of 15-25% by water supplementation, pumping the concentrated phosphogypsum slurry into the desiliconizing gravity concentration column, simultaneously adding water and introducing compressed air, carrying out jigging classification by means of a jigging generator, separating useful minerals from large-particle phosphate ores and silicon-containing impurities, discharging the large-particle phosphate ores and the silicon-containing impurities from the bottom, adding water to adjust the large-particle phosphate ores and the silicon-containing impurities into silicon tailing slurry with a mass concentration of 40-50%, and filtering the silicon tailing slurry in a belt filter to obtain silicon tailing; concentrated ore pulp with the mass concentration of 10-20% overflowing from the top is sent to be concentrated and filtered;

s3, filtering, washing and dephosphorizing: pumping the desiliconized phosphogypsum concentrated pulp with the mass concentration of 10-20% obtained in the step S2 into an inclined plate thickener for thickening and dewatering, pumping the underflow to obtain the phosphogypsum concentrated pulp with the mass concentration of 40-50%, pumping the phosphogypsum concentrated pulp into a belt filter for filtering, and discharging the washed filter cake into a warehouse to obtain the final refined phosphogypsum product.

2. The method for purifying the byproduct phosphogypsum of wet-process phosphoric acid according to claim 1, which is characterized in that phosphogypsum concentrate slurry with the mass concentration of 40-50% obtained from underflow in S3 is pumped into a belt filter for filtering, and water at the temperature of 30-70 ℃ is added in the filtering process to wash a filter cake so as to remove water-soluble impurities in the phosphogypsum.

3. The method for purifying the byproduct phosphogypsum of wet-process phosphoric acid according to claim 1, which is characterized in that under the action of aeration and stirring, the ore pulp collides with micro bubbles and is adsorbed, carbon-containing particles and organic impurities are adhered to the foams in the flotation tank in S1, the foams are lifted by virtue of the buoyancy of the bubbles and are separated from minerals, useful minerals sink to decolored phosphogypsum concentrate pulp, and the concentrate pulp is discharged from the bottom and enters the next process; the carbonaceous particles and organic impurities are discharged from the upper portion.

4. The method for purifying phosphogypsum as a byproduct of wet-process phosphoric acid according to claim 1, wherein the flotation equipment in S1 is not limited to a flotation tank, and a flotation column can be used.

5. The method for purifying phosphogypsum as a byproduct of wet-process phosphoric acid, according to claim 1, wherein the decolorizing agent is added into S1 according to the proportion of 0.1-0.2 ‰.

6. The method for purifying the byproduct phosphogypsum of wet-process phosphoric acid according to claim 1, which is characterized in that the content of organic matters in the decolored tailings in S1 reaches 25 percent and the method is used for producing organic fertilizer; the purity of the silicon tailings in the S2 reaches 70 percent, and the silicon tailings are used for baking-free hollow silica bricks or used as a raw material for producing silicon fertilizer.

7. The method for purifying the byproduct phosphogypsum of wet-process phosphoric acid according to claim 1, wherein the concentration filtration in S2 uses an inclined plate thickener, the sewage generated by the inclined plate thickener is collected in a sewage collecting tank, lime is added for neutralization, phosphorus and fluorine-containing impurities are precipitated, the supernatant is used as the return water for internal recycling, and the concentrate concentration equipment in S2 is not limited to the inclined plate thickener, and can also be concentrated by a deep cone thickener or a thickener.

8. The method for purifying phosphogypsum as a byproduct of wet-process phosphoric acid according to claim 1, wherein the filter equipment in S2 and S3 is not limited to a belt filter, and a disc filter or a filter press can be used.

9. The method for purifying the byproduct phosphogypsum of wet-process phosphoric acid according to claim 1, which is characterized in that a phosphogypsum purification system is adopted for treatment, wherein the phosphogypsum purification system comprises a raw gypsum slurrying tank (1), a flotation tank (2), a desilication and mineral separation tank (3), a plurality of groups of desilication and gravity separation columns (4), an inclined plate thickener (5), a silicon slag buffer tank (6), a first vacuum belt filter (7) and a second vacuum belt filter (8);

the raw gypsum slurry mixing tank (1) mixes and conveys raw gypsum slurry to a dosing and stirring barrel (11) through a pipeline and a slurry conveying pump (10), and the dosing and stirring barrel (11) discharges the raw gypsum slurry added with a decolorizing agent to the flotation tank (2); the upper part of the flotation tank (2) is connected to a gypsum tailing pump pool (16) through a pipeline, and the gypsum tailing pump pool (16) is connected to a filter press through a pipeline and a gypsum tailing transfer pump (17); the bottom of the flotation tank (2) is connected to a flotation pump pool (12) through a pipeline, the flotation pump pool (12) conveys the decolored phosphogypsum concentrated ore pulp to the desiliconization ore separation box (3) through a pipeline and a desiliconization gravity separation column feeding pump (13), and the desiliconization ore separation box (3) is connected with a plurality of groups of desiliconization gravity separation columns (4); the bottoms of the multiple groups of desiliconization gravity separation columns (4) are connected to the silicon slag buffer tank (6) through pipelines, and the bottom of the silicon slag buffer tank (6) is connected with a second vacuum belt filter (8) through a pipeline; the top of the multiple groups of desiliconization gravity separation columns (4) is connected with the inclined plate thickener (5) through a pipeline, the bottom of the inclined plate thickener (5) is connected with the desiliconization pump pool (14) through a pipeline, and the desiliconization pump pool (14) is connected with the first vacuum belt filter (7) through a fine paste filtering and feeding pump (15) and a pipeline.

Technical Field

The invention relates to the technical field of phosphogypsum, in particular to a purification method of a byproduct phosphogypsum of wet-process phosphoric acid.

Background

The phosphogypsum is a chemical by-product which is generated by taking calcium sulfate as a main component in the process of preparing phosphoric acid by a wet method by taking phosphate rock as a raw material. Approximately five tons of phosphogypsum are produced simultaneously per ton of phosphoric acid produced. The phosphogypsum also contains undecomposed phosphorite and SiO₂Alumina, ferric oxide, magnesium oxide, fluorine-containing substances, acidic insoluble organic matters and the like, which are harmful to human health and biological growth and influence the quality of phosphogypsum products; phosphogypsum is different from natural gypsum, although its CaSO₄·2H₂The content of O is higher, but the P content is 0.3-2.0 percent₂O₅0.1 to 1.5 percent of F, the wet-base phosphogypsum is acidic. At present, the stacking quantity of the Chinese phosphogypsum reaches more than 6 hundred million tons, the phosphogypsum is increased at a speed of more than 7000 million tons every year, but the effective utilization rate is less than 20 percent, and a large amount of phosphogypsum is stored in a direct stacking mode, thereby not only occupying land resources and bringing heavy burden to production enterprises, but also generating potential safety hazards and environmental pollution. The national safety supervision administration has brought the phosphogypsum library into the safety supervision range of non-coal mines and implemented a safety production permission system for the phosphogypsum library. The phosphogypsum warehouse enterprises must obtain the safety production license and cannot produce the phosphogypsum warehouse enterprises which do not obtain the safety production license after the period. The comprehensive utilization of the byproduct phosphogypsum is urgent from the aspects of the requirement of normal production of enterprises and the treatment of potential safety hazard and environmental pollution.

The phosphogypsum can be used as a building material, but the performance of the obtained building material is greatly influenced if the phosphogypsum obtained by production is directly utilized, wherein the influence of phosphorus on the performance of the phosphogypsum is the largest, and the specific expression is that the setting time of the phosphogypsum is prolonged, and the strength of a hardened body is reduced. The phosphorus component in the phosphogypsum mainly has three forms of soluble phosphorus, eutectic phosphorus and precipitated phosphorus, and the soluble phosphorus has the greatest influence on the performance. Soluble phosphorus is absorbed by dihydrate gypsum crystals in phosphogypsumThe soluble phosphorus and Ca in the solution are dissolved when the soluble phosphorus is hydrated and distributed on the surface of the dihydrate gypsum crystal²⁺Reaction to form insoluble Ca₃(PO₄)₂Attached to the surface of the gypsum to prevent the further dissolution and hydration of the gypsum, so that the setting time of the phosphogypsum is prolonged, the structure is loose and the strength is reduced; whereas the soluble fluorine F present in phosphogypsum^-The phosphorus building gypsum is accelerated, when the content of the phosphorus building gypsum is less than 0.3%, the influence on the strength of the building gypsum is small, and when the content of the phosphorus building gypsum exceeds 0.3%, the strength is rapidly reduced along with the increase of soluble fluorine F; the organic matters in the phosphogypsum are derived from organic impurities in phosphate ores and organic additives added in the production process, and mainly comprise ethylene glycol monomethyl ether acetate, isothiocyanic methane, 3-methoxy-n-pentane and the like. The impurities are distributed on the surface of the dihydrate gypsum crystal, which can obviously increase the water demand of the phosphogypsum cementing material, and can weaken the joint between dihydrate gypsum crystals, so that the hardened body has a loose structure and the strength is reduced. The silicon-containing impurities in the phosphogypsum mainly exist in the form of quartz, are introduced by phosphate ore and are slightly mixed with F^-Complexing to form Na₂SiF₆. They are inert in phosphogypsum and have no harmful effect, but have certain economic utilization value.

The byproduct phosphogypsum cannot reach the first-grade utilization standard of the national standard GB/T23456-2018, and the direct utilization of the byproduct phosphogypsum can generate extremely bad influence on the performance of the prepared building material and restrict the large-scale standardized utilization of the building material, so that the improvement of the quality of the phosphogypsum through subsequent process means is not only beneficial to the improvement of the performance of the building material, but also can realize the industrialized large-scale continuous production, thereby improving the comprehensive utilization rate of the byproduct phosphogypsum.

In the existing literature, research on the removal of soluble salts and organic matters by removing silicon from phosphogypsum separately by flotation and other beneficiation methods has been reported, but the industrial device for completely removing three types of impurities affecting comprehensive utilization in phosphogypsum, namely soluble salts such as soluble phosphorus, organic matters and other impurities affecting gypsum whiteness and silicates mainly comprising quartz chalcedony, by using a continuous process and equipment is not mature enough.

Disclosure of Invention

In view of the above, the present invention aims to provide a method for purifying phosphogypsum as a byproduct of wet-process phosphoric acid, which comprises the following steps:

s1, decoloring in a flotation tank: adding water into the byproduct phosphogypsum in the phosphoric acid process to adjust the byproduct phosphogypsum into ore pulp with the mass concentration of 25-40%, pumping into a dosing stirring barrel, simultaneously adding a decolorizing agent in proportion, uniformly mixing, and overflowing into a flotation tank; after flotation treatment, the bottom material is decolorized concentrate and enters the next process, and the upper tailings are subjected to filter pressing by a membrane filter press to obtain decolorized tailings;

s2, desiliconizing a jigging gravity concentration column, namely, adjusting the decolored phosphogypsum concentrate slurry obtained from the flotation tank in S1 into a mass concentration of 15-25% by water supplementation, pumping the concentrated phosphogypsum slurry into the desiliconizing gravity concentration column, simultaneously adding water and introducing compressed air, carrying out jigging classification by means of a jigging generator, separating useful minerals from large-particle phosphate ores and silicon-containing impurities, discharging the large-particle phosphate ores and the silicon-containing impurities from the bottom, adding water to adjust the large-particle phosphate ores and the silicon-containing impurities into silicon tailing slurry with a mass concentration of 40-50%, and filtering the silicon tailing slurry in a belt filter to obtain silicon tailing; concentrated ore pulp with the mass concentration of 10-20% overflowing from the top is sent to be concentrated and filtered;

s3, filtering, washing and dephosphorizing: pumping the desiliconized phosphogypsum concentrated pulp with the mass concentration of 10-20% obtained in the step S2 into an inclined plate thickener for thickening and dewatering, pumping the underflow to obtain the phosphogypsum concentrated pulp with the mass concentration of 40-50%, pumping the phosphogypsum concentrated pulp into a belt filter for filtering, and discharging the washed filter cake into a warehouse to obtain the final refined phosphogypsum product.

Pumping the phosphogypsum concentrate pulp with the mass concentration of 40-50% obtained from underflow in S3 into a belt filter for filtering, adding water at 30-70 ℃ in the filtering process to wash a filter cake, and removing water-soluble impurities in the phosphogypsum.

In S1, under the action of inflation and stirring, the ore pulp collides and adsorbs microbubbles, carbon-containing particles and organic impurities are adhered to foams, the foams rise by virtue of buoyancy of the bubbles and are separated from minerals, useful minerals sink to decolorized phosphogypsum concentrated ore pulp, and the decolorized phosphogypsum concentrated ore pulp is discharged from the bottom and enters the next process; the carbonaceous particles and organic impurities are discharged from the upper portion.

The flotation equipment in S1 is not limited to a flotation cell, and a flotation column can be used.

0.1-0.2 per mill of decolorizing agent is added into S1.

The organic matter content in the decolored tailings in the S1 reaches 25 percent, and the decolored tailings are used for producing organic fertilizer; the purity of the silicon tailings in the S2 reaches 70 percent, and the silicon tailings are used for baking-free hollow silica bricks or used as a raw material for producing silicon fertilizer.

In S2, the concentration filtration uses an inclined plate thickener, the sewage and the sewage generated by the inclined plate thickener are collected in a sewage collecting pool, lime is added for neutralization, phosphorus and fluorine-containing impurities are precipitated, the upper clear liquid is used as the return water for internal recycling, and the concentrate thickener in S2 is not limited to the inclined plate thickener, and can also be used for concentration by a deep cone thickener or a thickener.

The filter equipment in S2 and S3 is not limited to a belt filter, and a disk filter or a filter press may be used.

Adopting a phosphogypsum purification system for treatment, wherein the phosphogypsum purification system comprises a raw gypsum slurry mixing tank, a flotation tank, a desilication and ore separation box, a plurality of groups of desilication and gravity separation columns, an inclined plate thickener, a silicon slag buffer tank, a first vacuum belt filter and a second vacuum belt filter;

the raw gypsum slurry mixing tank conveys the raw gypsum slurry to a dosing stirring barrel through a pipeline and a slurry conveying pump, and the dosing stirring barrel discharges the raw gypsum slurry added with the decolorizing agent to the flotation tank; the upper part of the flotation tank is connected to a gypsum tailing pump pool through a pipeline, and the gypsum tailing pump pool is connected to a filter press through a pipeline and a gypsum tailing transfer pump; the bottom of the flotation tank is connected to a flotation pump pool through a pipeline, the flotation pump pool conveys the decolored phosphogypsum fine ore pulp to the desiliconization ore separation box through a pipeline and a desiliconization gravity separation column feeding pump, and the desiliconization ore separation box is connected with a plurality of groups of desiliconization gravity separation columns; the bottoms of the multiple groups of desiliconization gravity separation columns are connected to the silicon slag buffer tank through pipelines, and the bottoms of the silicon slag buffer tank are connected with the second vacuum belt filter through pipelines; the top of the desiliconization gravity separation columns is connected with the inclined plate thickener through a pipeline, the bottom of the inclined plate thickener is connected with a desiliconization pump pool through a pipeline, and the desiliconization pump pool is connected with the first vacuum belt filter through a fine paste filtering and feeding pump and a pipeline.

The invention has the advantages that: 1. is suitable for large-scale industrialized devices and can realize continuous, stable and reliable production. 2. The adaptability to the byproduct phosphogypsum is strong, and the method is particularly suitable for the byproduct phosphogypsum of the current phosphoric acid device using low-quality phosphate ores. 3. The method can comprehensively and systematically remove most harmful impurities in the phosphogypsum, greatly improve the purity, and obtain finished product concentrate which is suitable for producing high-quality building gypsum and has great economic and social benefits. 4. The tailings are solid with high purity, are easy to store, transport and use, can be completely recycled, and have no waste. 5. The sewage is recycled in the whole interior, and the environmental protection requirement is met. 6. Normal temperature purification treatment, less consumption of auxiliary materials such as medicaments, low water and electricity consumption and low total energy consumption, and conforms to the policy of energy conservation and emission reduction.

Drawings

FIG. 1 is a schematic process flow diagram of the present invention.

Fig. 2 is a schematic structural diagram of the phosphogypsum purification system of the present invention.

Detailed Description

The present invention will be further illustrated with reference to the following examples.

The phosphogypsum raw material used in the embodiment of the invention is phosphogypsum discharged from a phosphoric acid filtering section in the production process of Hubei Xinyangfeng agricultural science and technology Limited company, and the chemical composition of the phosphogypsum is shown as the following table:

table 1 properties of phosphogypsum raw materials

Reference numerals 1 and 2 denote two ore sources. Firstly, the raw ore grade is high (see the 1 st ore source in table 1), and the requirement of a downstream use working section on the grade is not high; secondly, the raw ore grade is low (see the 2 nd ore source in table 1), and the downstream use section has higher requirement on the grade.

< example 1>

In this embodiment, a method for purifying a byproduct phosphogypsum of wet-process phosphoric acid includes the following steps:

A. decoloring in a flotation tank: 420 tons of byproduct phosphogypsum in the phosphoric acid process is added with water to be adjusted into ore pulp with the mass concentration of 38 percent, the ore pulp is pumped into a dosing stirring barrel, simultaneously, a decolorizing agent is added according to 0.15 per mill of the mass concentration, the mixture is uniformly mixed, and overflows into a flotation tank. Under the action of inflation and stirring, ore pulp collides with microbubbles and is adsorbed, impurities such as carbon-containing particles, organic matters and the like are adhered to the foams due to the difference of physicochemical properties of the surfaces of mineral particles, the impurities rise by virtue of the buoyancy of the bubbles and are separated from the minerals, 378 tons of useful minerals sink to form concentrate, and the concentrate is discharged from the bottom and enters the next process; 42 tons of impurities such as carbon-containing particles and organic matter are discharged from the upper part.

B. B, desiliconizing the jigging gravity concentration column, namely, adjusting the decolored phosphogypsum concentrated ore pulp (378 tons of minerals) with the mass concentration of 50 percent obtained in the step A into 25 percent of mass concentration by supplementing water, pumping the concentrated phosphogypsum concentrated ore pulp into the desiliconizing gravity concentration column, simultaneously adding water and introducing compressed air, carrying out jigging classification by using a jigging generator, separating useful minerals with small specific gravity (about 2.2) and phosphate ores and silicon-containing impurities with large specific gravity (about 2.6) particles, discharging the phosphate ores and the silicon-containing impurities from the bottom, adding water to adjust the phosphate ores and the silicon-containing impurities into silicon tailing ore pulp with the mass concentration of 50 percent, and overflowing the silicon tailing ore pulp into a belt filter to be filtered to obtain 84 tons; 294 tons of useful minerals overflow from the top to form concentrate with the mass concentration of 20 percent, and the concentrate is sent to dense filtration.

The process can remove most of silicon-containing impurities and phosphate rock particles in the phosphogypsum and improve the grade of the phosphogypsum (the content of calcium sulfate dihydrate) to more than 90 percent. In actual production, the process can be changed according to the grade of raw ore and the application of downstream phosphogypsum: the method comprises the steps of firstly, enabling the raw ore to be high in grade (see the 1 st ore source in the table 1), directly entering the step C from the step A when the requirement on the grade of a downstream use working section is not high, and secondly, enabling the raw ore to be low in grade (see the 2 nd ore source in the table 1), enabling multistage desiliconization to be carried out when the requirement on the grade of the downstream use working section is high, and enabling the concentrate grade to be improved by more than 90%.

C. Filtering, washing and dephosphorizing: and D, concentrating the desiliconized phosphogypsum concentrate slurry with the mass concentration of 20% obtained in the step B by using an inclined plate thickener mentioned in a patent CN101569868B of Kunming metallurgy research institute. The top overflow clear water returns to the system for water supplement; pumping the phosphogypsum concentrate slurry with the mass concentration of 50 percent obtained by underflow into a belt filter for filtering. And (3) adding clear water to wash the filter cake in the filtering process, removing most of water-soluble impurities in the phosphogypsum, mainly water-soluble phosphorus, fluorine, magnesium, sodium, chlorine and the like, and carrying out the water-soluble impurities along with the washing water. Discharging the washed filter cake to a warehouse to obtain the final 294 tons of refined phosphogypsum products.

< example 2>

In this embodiment, a method for purifying a byproduct phosphogypsum of wet-process phosphoric acid includes the following steps:

A. decoloring in a flotation tank: 420 tons of byproduct phosphogypsum in the phosphoric acid process is added with water to be adjusted into ore pulp with the mass concentration of 28 percent, the ore pulp is pumped into a dosing stirring barrel, simultaneously, a decolorizing agent is added according to 0.18 per mill of the mass concentration, the mixture is uniformly mixed, and overflows into a flotation tank. Under the action of inflation and stirring, ore pulp collides with microbubbles and is adsorbed, impurities such as carbon-containing particles, organic matters and the like are adhered to the foams due to the difference of physicochemical properties of the surfaces of mineral particles, the impurities rise by virtue of the buoyancy of the bubbles and are separated from the minerals, 378 tons of useful minerals sink to form concentrate, and the concentrate is discharged from the bottom and enters the next process; 42 tons of impurities such as carbon-containing particles and organic matter are discharged from the upper part.

B. B, desiliconizing the jigging gravity concentration column, namely, adjusting the decolored phosphogypsum concentrated ore pulp (378 tons of minerals) with the mass concentration of 40 percent obtained in the step A into the mass concentration of 15 percent through water supplementation, pumping the concentrated phosphogypsum concentrated ore pulp into the desiliconizing gravity concentration column, simultaneously adding water and introducing compressed air, carrying out jigging classification by means of a jigging generator, separating useful minerals with small specific gravity (about 2.2) and phosphate ores and silicon-containing impurities with large specific gravity (about 2.6) particles, discharging the phosphate ores and the silicon-containing impurities from the bottom, adding water to adjust the phosphate ores and the silicon-containing impurities into silicon tailing ore pulp with the mass concentration of 40 percent, and overflowing the silicon tailing ore pulp into a belt filter to be filtered to obtain 104; 270.8 tons of useful minerals overflow from the top to become concentrate with the mass concentration of 12 percent and are sent to dense filtration.

The process can remove most of silicon-containing impurities and phosphate rock particles in the phosphogypsum and improve the grade of the phosphogypsum (the content of calcium sulfate dihydrate) to more than 90 percent. In actual production, the process can be changed according to the grade of raw ore and the application of downstream phosphogypsum: the method comprises the steps of firstly, enabling the raw ore to be high in grade (see the 1 st ore source in the table 1), directly entering the step C from the step A when the requirement on the grade of a downstream use working section is not high, and secondly, enabling the raw ore to be low in grade (see the 2 nd ore source in the table 1), enabling multistage desiliconization to be carried out when the requirement on the grade of the downstream use working section is high, and enabling the concentrate grade to be improved by more than 90%.

C. Filtering, washing and dephosphorizing: and D, concentrating the desiliconized phosphogypsum concentrate slurry with the mass concentration of 12% obtained in the step B by using an inclined plate thickener mentioned in a patent CN101569868B of Kunming metallurgy research institute. The top overflow clear water returns to the system for water supplement; pumping the phosphogypsum concentrate slurry with the mass concentration of 40 percent obtained by underflow into a belt filter for filtering. And (3) adding clear water to wash the filter cake in the filtering process, removing most of water-soluble impurities in the phosphogypsum, mainly water-soluble phosphorus, fluorine, magnesium, sodium, chlorine and the like, and carrying out the water-soluble impurities along with the washing water. Discharging the washed filter cake to a warehouse to obtain a final 270.8 ton refined phosphogypsum product.

The results of the tests of examples 1 and 2 are shown in Table 2 below:

TABLE 2

The phosphogypsum concentrate of the embodiment meets the primary standard of national standard GB/T23456-2018 phosphogypsum.

The internal circulation flow of the sewage of the embodiment is as follows: and (3) feeding internal circulating water and a phosphoric acid byproduct phosphogypsum into a size mixing tank to form slurry, and then respectively carrying out decolorization, desiliconization and treatment, filtering the generated tailings, and pumping the sewage into a sewage collection tank. The sewage generated after the concentrate enters the inclined plate thickener for concentration and the sewage generated by filtering are both removed from the sewage collecting tank, lime is added for neutralization, impurities containing phosphorus, fluorine and the like are precipitated, and the supernatant is recycled as the return water: inputting the mixture into a slurry mixing tank of a phosphoric acid workshop for slurry mixing; adding water for decolouring, desiliconizing, thickening and filtering. In the whole process, no redundant sewage is generated, clear water is not required to be supplemented, and the sewage is completely internally sealed and recycled.

In the process, four places for generating sewage comprise decolored tailing pressure filtration water, desiliconized tailing filtration water, inclined plate thickening overflow water and concentrate filtration washing liquid water, and the water discharge is 68.49+6.25+129.62+30.9 =235.26 tons; the sewage consumption place has four kinds of repulping tank size mixing, flotation tank moisturizing, desilicication moisturizing and concentrate filtration washing water, and the consumption is: 61.9+29.28+130.01+14.07 =235.26 tons, and the water carrying capacity of the concentrate, the decolored tailings and the desiliconized tailings is 4.75+0.68+2.08=7.51 tons, and 7.51 tons of sewage input by a phosphoric acid working section is needed to keep the sewage balance.

Sealing water of the vacuum pump, the air compressor and various slurry pumps is collected into a clean water tank in a centralized manner, and is pumped into each part for circulation after being cooled by a water cooling tower, so that the internal circulation of the clean water is realized.

Therefore, the whole purification system completely realizes separate and respective circulation of clear water and sewage, realizes zero emission and meets the current emission reduction requirement.

The present example produces mainly three solid substances: phosphogypsum concentrate, silicon slag and decoloration tailings. Wherein the silicon slag has a purity of 70 percent and is 84 tons, and the silicon slag can be directly used for baking-free hollow silica bricks or used as a raw material for producing silicon fertilizer inside a company. 42 tons of decolored tailings with the organic matter content of 25 percent are used for producing organic fertilizers inside companies.

The method adopts a phosphogypsum purification system for treatment, wherein the phosphogypsum purification system comprises a raw gypsum slurry mixing tank 1, a flotation tank 2, a desilication and ore separation tank 3, a plurality of groups of desilication and gravity separation columns 4, an inclined plate thickener 5, a silicon slag buffer tank 6, a first vacuum belt filter 7 and a second vacuum belt filter 8;

the raw gypsum slurry mixing tank 1 conveys the raw gypsum slurry to a dosing and stirring barrel 11 through a pipeline and a slurry conveying pump 10, and the dosing and stirring barrel 11 discharges the raw gypsum slurry added with the decolorizing agent to the flotation tank 2; the upper part of the flotation tank 2 is connected to a gypsum tailing pump pool 16 through a pipeline, and the gypsum tailing pump pool 16 is connected to a filter press through a pipeline and a gypsum tailing transfer pump 17; the bottom of the flotation tank 2 is connected to a flotation pump pool 12 through a pipeline, the flotation pump pool 12 conveys the decolored phosphogypsum concentrated ore pulp to the desiliconization ore separation box 3 through a pipeline and a desiliconization gravity separation column feeding pump 13, and the desiliconization ore separation box 3 is connected with a plurality of groups of desiliconization gravity separation columns 4; the bottoms of the multiple groups of desiliconization gravity separation columns 4 are connected to the silicon slag buffer tank 6 through pipelines, and the bottom of the silicon slag buffer tank 6 is connected with the second vacuum belt filter 8 through a pipeline; the tops of the multiple groups of desiliconization gravity separation columns 4 are connected with the inclined plate thickener 5 through pipelines, the bottom of the inclined plate thickener 5 is connected with a desiliconization pump pool 14 through a pipeline, and the desiliconization pump pool 14 is connected with the first vacuum belt filter 7 through a fine paste filtering and feeding pump 15 and a pipeline.