Ardealite source harmless treatment method

Abstract

The invention relates to the technical field of solid waste treatment, in particular to a phosphogypsum source harmless treatment method. Washing the tail section of the crystal growing slurry filtering system with clean water, and obtaining phosphogypsum after washing, wherein the ratio of the water consumption of the clean water to the phosphogypsum is (1: 10)-(1: 1) cubic / ton; performing size mixing on filter cloth washing water in a crystal growing slurry filtering system and the obtained ardealite to obtain ardealite slurry with the concentration of 20wt%-60wt%; adding a harmless treatment agent A into the obtained ardealite slurry, uniformly stirring and mixing, and reacting for 5-60 minutes to obtain first-stage reaction slurry; adding a harmless agent B into the obtained first-stage reaction slurry, uniformly stirring and mixing, reacting for 20-60 minutes, and filtering to obtain filtrate and harmless ardealite. The comprehensive recovery rate of fluorine and phosphorus valuable components in the wet-process phosphoric acid industry is realized through simple process improvement, and the pollutant content of the phosphogypsum after washing and filtering is reduced; according to the phosphogypsum harmless treatment method, the idea that industrial solid waste is used for treating pollution with waste is utilized, the agent preparation raw materials are wide in source and low in cost, and the agent is a toxic representative for solid waste pollution prevention and control cooperative control and assistant pollution reduction and carbon reduction synergistic interaction.

Description

Technical Field

[0001] The invention relates to the technical field of solid waste treatment, and in particular to a method for harmless treatment of phosphogypsum source. Background Art

[0002] Phosphogypsum is the main by-product produced in the wet production of phosphoric acid and phosphate fertilizer. The solid produced by the three-stage countercurrent washing and filtration of the bottom flow slurry of the phosphoric acid reactor is phosphogypsum, and the filtrate is returned to extract fluorine and phosphorus. Every ton of phosphoric acid produced can produce about 4.5 to 5.0 tons of phosphogypsum. In 2022, my country's phosphogypsum production will be about 77 million tons, the unutilized rate will exceed 50%, and the accumulated stockpile will be about 820 million tons. The solid waste of phosphogypsum produced by most companies is hazardous waste and poses a high environmental risk. Therefore, how to achieve low-cost, large-scale and harmless treatment of phosphogypsum at the source is a key and difficult problem that the industry urgently needs to solve.

[0003] At present, the methods for harmless treatment of phosphogypsum sources are mainly divided into the method of adding reagents and the method of washing process. CN117102219A discloses a method for harmless treatment of phosphogypsum by adding alkaline materials and neutral calcium raw materials. In addition to the need to add a variety of reagents, the method also needs to be carried out in a reactor under high temperature and high pressure. CN112871457A discloses a method for purifying and removing impurities from phosphogypsum, in which phosphogypsum is prepared into a slurry by adding water, quicklime is added to precipitate soluble phosphorus and fluorine, water glass is added under strong stirring, the generated phosphorus and fluorine precipitates are dispersed with lime, and then a decolorizing agent and an adsorbent agent are added to finally obtain a gypsum concentrate. This method requires the addition of a large amount of reagents, resulting in high costs. CN106977123A discloses a method for removing impurity fluorine from phosphogypsum, that is, adding phosphogypsum to citric acid water for water washing, then washing the phosphogypsum sample, and finally removing impurities through a water washing process. This method may bring out soluble organic matter in phosphogypsum during the water washing process, causing secondary pollution. At the same time, multiple water washings consume a large amount of water and the processing cost is high. Summary of the invention

[0004] In view of the above technical problems, the present invention provides a method for harmless treatment of phosphogypsum at the source. Based on the problems existing in the three-stage countercurrent water washing of phosphogypsum in the wet phosphoric acid industry, the present invention makes technical improvements to the water washing and filtration section, thereby achieving the goal of improving the comprehensive recovery rate of fluorine and phosphorus resources while reducing the content of harmful components in phosphogypsum; in addition, the improved phosphogypsum is subjected to slurry adjustment and two-stage dosing and stirring to achieve the goal of green, large-scale, and low-cost harmless treatment, so as to expand the comprehensive utilization channels of phosphogypsum. The present invention treats phosphogypsum, a solid hazardous waste, with industrial solid waste to "treat waste with waste", without the need for external temperature and pressure conditions, and treats phosphogypsum at low cost, on a large scale, and harmlessly. It is a very effective environmental protection technology, which enables the harmlessly treated phosphogypsum to meet the requirements of Class I general solid waste.

[0005] A method for harmless treatment of phosphogypsum source, comprising the following steps:

[0006] Step 1, source pollution reduction: the final water washing of the growing crystal slurry filtration system is carried out with clean water, the ratio of clean water to phosphogypsum is 1:10-1:1 cubic / ton, and phosphogypsum is obtained after washing; generally, the final stage is the third stage, and source pollution reduction is a necessary condition for harmless treatment of non-phosphogypsum sources. This stage only helps to improve the recovery rate of fluorine and phosphorus and reduce the amount of harmless agents used in the later stage;

[0007] Step 2, mixing and stirring to prepare slurry: mixing the filter cloth washing water in the growing crystal slurry filtration system with the phosphogypsum obtained in step 1 to prepare a phosphogypsum slurry with a concentration of 20wt% to 60wt%;

[0008] Step 3, a first-stage mixing and stirring reaction: add the harmless treatment agent A to the phosphogypsum slurry obtained in step 2, stir and mix evenly, and react for 5-60 minutes to obtain a first-stage reaction slurry;

[0009] Step 4, two-stage mixing and stirring reaction: add the harmless agent B to the first-stage reaction slurry obtained in step 3, stir and mix evenly, the reaction residence time is 20 to 60 minutes, and filter to obtain the filtrate and harmless phosphogypsum.

[0010] The clean water in step 1 is fresh water or treated production wastewater with low fluoride and phosphate impurity contents.

[0011] The washing water after the final water washing in step 1 is sequentially returned to the previous water washing, and after being filtered through the first water washing, is returned to the extraction section to recover fluorine and phosphorus.

[0012] In step 3, the harmless treatment agent A is one of steel slag, coal gangue, yellow phosphorus slag, fly ash, boiler ash, building material waste, water-quenched slag, red mud, and aluminum ash, or a mixture of multiple agents in any proportion, and the added amount is 0.5% to 2.5% of the mass of the treated phosphogypsum.

[0013] In step 4, the harmless treatment agent B is one of carbide slag, lime, and alkali slag, or a mixture of multiple agents in any proportion, and the added amount is 0.1% to 1.5% of the mass of the treated phosphogypsum.

[0014] The filtrate in step 4 is returned to the crystal growing slurry filtration system as filter cloth flushing water, and is mixed with phosphogypsum for slurry preparation after flushing.

[0015] Compared with the prior art, the present invention has the following beneficial effects:

[0016] (1) The present invention achieves the comprehensive recovery rate of fluorine and phosphorus valuable components in the wet-process phosphoric acid industry through simple process improvements, and reduces the pollutant content of phosphogypsum after water washing and filtration; the present invention significantly reduces the fluoride and phosphate content in the phosphogypsum after source pollution reduction through source pollution reduction, and in the subsequent phosphogypsum treatment process, the amount of added drugs is reduced by 50-70% compared with the amount of drugs without source pollution reduction.

[0017] (2) The harmless treatment of phosphogypsum utilizes the concept of "using waste to treat pollution" of industrial solid waste, and the raw materials for the preparation of the agent are widely available and low in cost. The harmless treatment process of phosphogypsum of the present invention is simple to operate and has a short process. The harmless treatment process is completed in the slurry, and the treatment scale is flexible and the reaction is sufficient. The properties of the harmless phosphogypsum are stable. It is a green, environmentally friendly and energy-saving source harmless treatment technology for phosphogypsum. The properties of the phosphogypsum treated by this method meet the standards of Class I general industrial solid waste. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a process flow chart of the present invention. DETAILED DESCRIPTION

[0019] The present invention will be further described below in conjunction with the accompanying drawings and specific implementation methods.

[0020] Example 1

[0021] The method for harmless treatment of phosphogypsum source comprises the following steps:

[0022] Step 1: Source pollution reduction: The wet phosphoric acid production line of a certain enterprise A produces 200t / h of phosphogypsum. The third stage of the water washing of the crystal slurry filtration system is washed with clean water. The ratio of clean water to phosphogypsum is 1:10 cubic meters / ton, that is, the water consumption for water washing is 20m 3 / h, and phosphogypsum is obtained after washing; generally, the last stage is the third stage, which is a necessary condition for the source pollution reduction and harmless treatment of non-phosphogypsum. This stage only helps to improve the recovery rate of fluorine and phosphorus and reduce the amount of harmless agents used in the later stage;

[0023] Step 2, mixing and stirring to prepare slurry: mixing the filter cloth washing water in the growing crystal slurry filtration system with the phosphogypsum obtained in step 1 to prepare a phosphogypsum slurry with a concentration of 45 wt%;

[0024] Step 3, a first-stage mixing and stirring reaction: the phosphogypsum slurry obtained in step 2 is pumped to a first-stage harmless mixing and stirring tank, and reagent A (red mud, yellow phosphorus slag, and stone cutting waste are prepared in a ratio of 1:1:1) is added at the same time, the addition amount is 3 t / h (1.5% of the mass of the treated phosphogypsum), the stirring speed is 70 r / min, the mixing is uniform, and the reaction time at room temperature is 30 min to obtain a first-stage reaction slurry;

[0025] Step 4, two-stage mixed stirring reaction: the first-stage reaction slurry obtained in step 3 is gravity-flowed or rushed to the second-stage mixed stirring reaction tank, and at the same time, a harmless agent B (calcium carbide slag and lime are prepared in a ratio of 1:2) is added, and the addition amount is 2t / h (1% of the mass of the treated phosphogypsum). The mixture is stirred and mixed evenly at a stirring speed of 70r / min, and the reaction residence time is 40min at room temperature. After filtering, a filtrate and harmless phosphogypsum are obtained. Before and after the harmless treatment, the phosphogypsum is leached in accordance with the "Horizontal Oscillation Method for Toxicity Leaching of Solid Waste" (HJ557-2010). The characteristic pollution indicators of the leachate are shown in Table 1, and the pollutant content meets the requirements of Class I general industrial solid waste.

[0026] Comparative Example 1

[0027] The method for harmless treatment of phosphogypsum source includes the following steps (without implementing source pollution reduction improvement, directly implementing harmless treatment):

[0028] Step 1: Mixing and slurry preparation: The wet phosphoric acid production line of a certain enterprise A produces 200t / h of phosphogypsum. The third stage of the water washing of the crystal slurry filtration system is the leachate produced by the phosphogypsum reservoir. The ratio of water consumption for water washing to phosphogypsum is 1:10 cubic meters / ton, that is, the water consumption for water washing is 20m 3 / h, after washing, washing water and phosphogypsum are obtained, and the washing water is returned in turn as the second stage and the first stage washing water. After the first stage washing and filtration, the filtrate is returned to the extraction section to recover fluorine and phosphorus, and the produced phosphogypsum is mixed with the filter cloth washing water to form a slurry with a solid content of 45%.

[0029] Step 2, a first-stage mixing and stirring reaction: the phosphogypsum slurry obtained in step 1 is pumped to a first-stage harmless mixing and stirring tank, and reagent A (red mud, yellow phosphorus slag, and stone cutting waste are prepared in a ratio of 1:1:1) is added at the same time, the addition amount is 6 t / h (3% of the mass of the treated phosphogypsum), the stirring speed is 70 r / min, the mixing is uniform, and the reaction time at room temperature is 30 min to obtain a first-stage reaction slurry;

[0030] Step 3, two-stage mixed stirring reaction: the first-stage reaction slurry obtained in step 2 is gravity-flowed or rushed to the second-stage mixed stirring reaction tank, and at the same time, a harmless agent B (calcium carbide slag and lime are prepared in a ratio of 1:2) is added, and the addition amount is 6t / h (3% of the mass of the treated phosphogypsum). The mixture is stirred and mixed evenly at a stirring speed of 70r / min, and the reaction residence time is 40min at room temperature. After filtering, a filtrate and harmless phosphogypsum are obtained. Before and after the harmless treatment, the phosphogypsum is leached in accordance with the "Horizontal Oscillation Method for Toxicity Leaching of Solid Waste" (HJ557-2010). The characteristic pollution indicators of the leachate are shown in Table 1, and the pollutant content meets the requirements of Class I general industrial solid waste.

[0031] Table 1 Pollutant content of phosphogypsum leachate before and after harmless treatment of Example 1 and Comparative Example 1 (mg / L)

[0032]

[0033] From the comparison between Example 1 and Comparative Example 1, it can be seen that after source pollution reduction in Example 1, the amount of drugs added in the first-stage reaction was reduced by 50%, and the amount of drugs added in the second-stage reaction was reduced by 67%, which significantly reduced the production cost of harmless treatment.

[0034] Comparative Example 2

[0035] The method for harmless treatment of phosphogypsum source comprises the following steps (only one stage of reaction):

[0036] The method for harmless treatment of phosphogypsum source comprises the following steps:

[0037] Step 1: Source pollution reduction: The wet phosphoric acid production line of a certain enterprise A produces 200t / h of phosphogypsum. The third stage of the water washing of the crystal slurry filtration system is washed with clean water. The ratio of clean water to phosphogypsum is 1:10 cubic meters / ton, that is, the water consumption for water washing is 20m 3 / h, and phosphogypsum is obtained after washing; generally, the last stage is the third stage, which is a necessary condition for the source pollution reduction and harmless treatment of non-phosphogypsum. This stage only helps to improve the recovery rate of fluorine and phosphorus and reduce the amount of harmless agents used in the later stage;

[0038] Step 2, mixing and stirring to prepare slurry: mixing the filter cloth washing water in the growing crystal slurry filtration system with the phosphogypsum obtained in step 1 to prepare a phosphogypsum slurry with a concentration of 45 wt%;

[0039] Step 3, one-stage mixing and stirring reaction: the phosphogypsum slurry obtained in step 2 is pumped to a harmless mixing and stirring tank, and reagent A (red mud, yellow phosphorus slag, and stone cutting waste are prepared in a ratio of 1:1:1) is added at the same time, the addition amount is 12t / h (6% of the mass of the treated phosphogypsum), the stirring speed is 70r / min, and the stirring and mixing are uniform, and the reaction time at room temperature is 30min to obtain a first-stage reaction slurry; after filtration, a filtrate and harmless phosphogypsum are obtained. Before and after harmless treatment, the phosphogypsum is leached in accordance with the "Horizontal Oscillation Method for Toxicity Leaching of Solid Waste" (HJ557-2010), and the characteristic pollution indicators of the leachate are shown in Table 2.

[0040] Table 2 Pollutant content of phosphogypsum leachate before and after harmless treatment of Example 1 and Comparative Example 2 (mg / L)

[0041]

[0042] It can be seen from Example 1 and Comparative Example 2 that the pollutant content in Comparative Example 2 does not meet the requirements of Class I general industrial solid waste. That is, without the two specific harmless treatment steps of the present invention, it is impossible to obtain the technical effect of the present invention.

[0043] Comparative Example 3

[0044] The method for harmless treatment of phosphogypsum source comprises the following steps (the reagents added in the first-stage reaction and the second-stage reaction are the same):

[0045] The method for harmless treatment of phosphogypsum source comprises the following steps:

[0046] Step 1: Source pollution reduction: The wet phosphoric acid production line of a certain enterprise A produces 200t / h of phosphogypsum. The third stage of the water washing of the crystal slurry filtration system is washed with clean water. The ratio of clean water to phosphogypsum is 1:10 cubic meters / ton, that is, the water consumption for water washing is 20m 3 / h, and phosphogypsum is obtained after washing; generally, the last stage is the third stage, which is a necessary condition for the source pollution reduction and harmless treatment of non-phosphogypsum. This stage only helps to improve the recovery rate of fluorine and phosphorus and reduce the amount of harmless agents used in the later stage;

[0047] Step 2, mixing and stirring to prepare slurry: mixing the filter cloth washing water in the growing crystal slurry filtration system with the phosphogypsum obtained in step 1 to prepare a phosphogypsum slurry with a concentration of 45 wt%;

[0048] Step 3, a first-stage mixing and stirring reaction: the phosphogypsum slurry obtained in step 2 is pumped to a first-stage harmless mixing and stirring tank, and reagent A (red mud, yellow phosphorus slag, and stone cutting waste are prepared in a ratio of 1:1:1) is added at the same time, the addition amount is 6 t / h (3% of the mass of the treated phosphogypsum), the stirring speed is 70 r / min, the mixing is uniform, and the reaction time at room temperature is 30 min to obtain a first-stage reaction slurry;

[0049] Step 4, two-stage mixing and stirring reaction: The first-stage reaction slurry obtained in step 3 is gravity-flowed or rushed to the second-stage mixing and stirring reaction tank, and the harmless agent B (red mud, yellow phosphorus slag, and stone cutting waste are prepared in a ratio of 1:1:1) is added at the same time, and the addition amount is 6 t / h (3% of the mass of the treated phosphogypsum). The mixture is stirred and mixed evenly at a stirring speed of 70 r / min, and the reaction residence time at room temperature is 40 min. After filtering, the filtrate and harmless phosphogypsum are obtained. The phosphogypsum before and after the harmless treatment is leached according to the "Horizontal Oscillation Method for Toxicity Leaching of Solid Waste" (HJ557-2010), and the characteristic pollution indicators of the leachate are shown in Table 3.

[0050] Table 3 Pollutant content of phosphogypsum leachate before and after harmless treatment of Example 1 and Comparative Example 3 (mg / L)

[0051]

[0052] It can be seen from Example 1 that the pollutant content in Comparative Example 3 does not meet the requirements of Class I general industrial solid waste. That is, without the harmless steps of different types of reagents in different reaction stages specified by the present invention, it is impossible to obtain the technical effect of the present invention.

[0053] Example 2

[0054] like Figure 1 As shown, the method for harmless treatment of phosphogypsum source comprises the following steps:

[0055] Step 1: Source pollution reduction: The third-stage water washing water of the wet-process phosphoric acid production crystal slurry filtration system is improved to process water. The ratio of water washing water to phosphogypsum is 1:10 cubic meters per ton, that is, the water washing water is 20m 3 / h, of which the process water has a fluoride content of 5.6 mg / L and a phosphate content of 0.2 mg / L. After washing and filtration, washing water and phosphogypsum are obtained. The washing water is returned in turn as water for the front-stage washing. After the first-stage washing and filtration, the filtrate is returned to the extraction section to recover fluorine and phosphorus. The content of phosphogypsum pollutants produced by the phosphogypsum before and after the implementation of source pollution reduction is shown in Table 4.

[0056] Table 4 Comparison of phosphogypsum quality before and after source pollution reduction implementation

[0057]

[0058] Step 2, mixing and stirring to prepare slurry: mixing the filter cloth washing water in the growing crystal slurry filtration system with the phosphogypsum obtained in step 1 to prepare a phosphogypsum slurry with a concentration of 45 wt%;

[0059] Step 3, one-stage mixing and stirring reaction: pump the phosphogypsum slurry obtained in step 2 to a one-stage mixing and stirring reaction tank, and add reagent A (yellow phosphorus slag and water-quenched slag prepared in a ratio of 1:1) at the same time, the addition amount is 5 t / h (3% of the mass of the treated phosphogypsum), the stirring speed is 70 r / min, the mixing is uniform, the reaction time at room temperature is 40 min, and a one-stage reaction slurry is obtained;

[0060] Step 4, two-stage mixed stirring reaction: The first-stage reaction slurry obtained in step 3 is self-flowed or pumped to the second-stage mixed stirring reaction tank, and reagent B (calcium carbide slag and alkali slag are prepared in a ratio of 2:1) is added at the same time, the addition amount is 6t / h (3% of the mass of the treated phosphogypsum), the stirring speed is 70r / min, and the mixture is stirred and mixed evenly. The reaction residence time at room temperature is 40min, and the filtrate and harmless phosphogypsum are obtained after filtration. Before and after harmless treatment, the phosphogypsum is leached according to the "Horizontal Oscillation Method for Toxicity Leaching of Solid Waste" (HJ557-2010). The characteristic pollution indicators of the leachate are shown in Table 5, and the pollutant content meets the requirements of Class I general industrial solid waste.

[0061] Table 5 Analysis results of leachate before and after harmless treatment of phosphogypsum source

[0062]

[0063] Example 3

[0064] like Figure 1 As shown, the method for harmless treatment of phosphogypsum source comprises the following steps:

[0065] Step 1: Source pollution reduction: The third-stage water washing water of the wet-process phosphoric acid production crystal slurry filtration system is improved to process water. The ratio of water washing water to phosphogypsum is 1:8 cubic meters per ton, that is, the water washing water is 25m 3 / h, of which the clean water has a fluoride content of 5.6 mg / L and a phosphate content of 0.2 mg / L. After washing and filtration, washing water and phosphogypsum are obtained. The washing water is returned in turn as water for the front-stage washing. After the first-stage washing and filtration, the filtrate is returned to the extraction section to recover fluorine and phosphorus. The content of phosphogypsum pollutants produced by the phosphogypsum before and after the implementation of source pollution reduction is shown in Table 6.

[0066] Table 6 Comparison of phosphogypsum quality before and after source pollution reduction implementation

[0067]

[0068] Step 2, mixing and stirring to prepare a slurry: mixing the filter cloth washing water in the growing crystal slurry filtration system with the phosphogypsum obtained in step 1 to prepare a phosphogypsum slurry with a concentration of 50 wt%;

[0069] Step 3, one-stage mixing and stirring reaction: pump the phosphogypsum slurry obtained in step 2 to a one-stage mixing and stirring reaction tank, and add reagent A (prepared with steel slag and fly ash in a ratio of 1:1) at the same time, the addition amount is 5 t / h (2.5% of the mass of the treated phosphogypsum), the stirring speed is 70 r / min, and the mixture is stirred evenly, and the reaction time at room temperature is 20 min to obtain a one-stage reaction slurry;

[0070] Step 4, two-stage mixed stirring reaction: The first-stage reaction slurry obtained in step 3 is self-flowed or pumped to the second-stage mixed stirring reaction tank, and reagent B (prepared from carbide slag) is added at the same time, the addition amount is 8t / h (4% of the mass of the treated phosphogypsum), the stirring speed is 70r / min, and the mixture is stirred and mixed evenly, and the reaction residence time at room temperature is 60min. After filtering, the filtrate and harmless phosphogypsum are obtained. Before and after harmless treatment, the phosphogypsum is leached according to the "Solid Waste Leaching Toxicity Leaching Method Horizontal Oscillation Method" (HJ557-2010), and the characteristic pollution indicators of the leachate are shown in Table 7, and the pollutant content meets the requirements of Class I general industrial solid waste.

[0071] Table 7 Analysis results of leachate before and after harmless treatment of phosphogypsum source

[0072]

[0073] Example 4

[0074] like Figure 1 As shown, the method for harmless treatment of phosphogypsum source comprises the following steps:

[0075] Step 1: Source pollution reduction: The third-stage water washing water of the wet-process phosphoric acid production crystal slurry filtration system is improved to process water. The ratio of water washing water to phosphogypsum is 1:6.7 cubic meters per ton, that is, the water washing water consumption is 30m 3 / h, where the process water has a fluoride content of 1.6 mg / L and a phosphate content of 0.6 mg / L. After washing and filtration, wash water and phosphogypsum are obtained. The wash water is returned in turn as water for the front-stage washing. After the first-stage washing and filtration, the filtrate is returned to the extraction section to recover fluorine and phosphorus. The content of phosphogypsum pollutants produced by the phosphogypsum before and after the implementation of source pollution reduction is shown in Table 8.

[0076] Table 8 Comparison of phosphogypsum quality before and after source pollution reduction implementation

[0077]

[0078]

[0079] Step 2, mixing and stirring to prepare slurry: mixing the filter cloth washing water in the growing crystal slurry filtration system with the phosphogypsum obtained in step 1 to prepare a phosphogypsum slurry with a concentration of 35 wt%;

[0080] Step 3, one-stage mixing and stirring reaction: pump the phosphogypsum slurry obtained in step 2 to a one-stage mixing and stirring reaction tank, and add reagent A (aluminum ash and building material waste prepared in a ratio of 1:1) at the same time, the addition amount is 3 t / h (1.5% of the mass of the treated phosphogypsum), the stirring speed is 70 r / min, the mixing is uniform, the reaction time at room temperature is 40 min, and a one-stage reaction slurry is obtained;

[0081] Step 4, two-stage mixed stirring reaction: The first-stage reaction slurry obtained in step 3 is self-flowed or pumped to the second-stage mixed stirring reaction tank, and reagent B (prepared from alkali residue) is added at the same time, the addition amount is 10t / h (5% of the mass of the treated phosphogypsum), the stirring speed is 70r / min, and the mixture is stirred and mixed evenly, and the reaction residence time at room temperature is 60min. After filtering, the filtrate and harmless phosphogypsum are obtained. Before and after harmless treatment, the phosphogypsum is leached according to the "Solid Waste Leaching Toxicity Leaching Method Horizontal Oscillation Method" (HJ557-2010), and the characteristic pollution indicators of the leachate are shown in Table 9, and the pollutant content meets the requirements of Class I general industrial solid waste.

[0082] Table 9 Analysis results of leachate before and after harmless treatment of phosphogypsum source

[0083]

[0084] The specific implementation modes of the present invention are described in detail above in conjunction with the accompanying drawings, but the present invention is not limited to the above implementation modes, and various changes can be made within the knowledge scope of ordinary technicians in this field without departing from the purpose of the present invention.

Claims

1. A method for harmless treatment of phosphogypsum source, characterized in that The following steps are involved: Step 1: Source pollution reduction: The final water washing of the growing crystal slurry filtration system is performed with clean water, and the ratio of clean water to phosphogypsum is 1:10 to 1:1 cubic meters per ton, and phosphogypsum is obtained after washing; Step 2, mixing and stirring to prepare slurry: mixing the filter cloth washing water in the growing crystal slurry filtration system with the phosphogypsum obtained in step 1 to prepare a phosphogypsum slurry with a concentration of 20wt% to 60wt%; Step 3, a first-stage mixing and stirring reaction: add the harmless treatment agent A to the phosphogypsum slurry obtained in step 2, stir and mix evenly, and react for 5-60 minutes to obtain a first-stage reaction slurry; Step 4, two-stage mixing and stirring reaction: add the harmless agent B to the first-stage reaction slurry obtained in step 3, stir and mix evenly, the reaction residence time is 20 to 60 minutes, and the slurry is filtered to obtain a filtrate and harmless phosphogypsum.

2. The method for harmless treatment of phosphogypsum source according to claim 1, characterized in that: The purified water in step 1 is fresh water or production wastewater or treated process water with fluoride and phosphate impurity contents less than 10 mg / L and 1 mg / L respectively.

3. The method for harmless treatment of phosphogypsum source according to claim 2, characterized in that: The washing water after the final water washing in step 1 is sequentially returned to the previous water washing, and after being filtered through the first water washing, is returned to the extraction section to recover fluorine and phosphorus.

4. The method for harmless treatment of phosphogypsum source according to claim 1 or 3, characterized in that: In step 3, the harmless treatment agent A is one of steel slag, coal gangue, yellow phosphorus slag, fly ash, boiler ash, building material waste, water-quenched slag, red mud, and aluminum ash, or a mixture of multiple agents in any proportion, and the added amount is 0.5% to 2.5% of the mass of the treated phosphogypsum.

5. The method for harmless treatment of phosphogypsum source according to claim 1, characterized in that: In step 4, the harmless treatment agent B is one of carbide slag, lime, and alkali slag, or a mixture of multiple agents in any proportion, and the added amount is 0.1% to 1.5% of the mass of the treated phosphogypsum.

6. The method for harmless treatment of phosphogypsum source according to claim 1, characterized in that: The filtrate in step 4 is returned to the crystal growing slurry filtration system as filter cloth flushing water.

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