Phosphogypsum solidifying agent and phosphogypsum harmless treatment method

Abstract

The application provides a phosphogypsum solidifying agent and a phosphogypsum harmless treatment method.The phosphogypsum solidifying agent is mainly composed of calcium salt and solid waste, and is lower in cost than previous agents; the phosphogypsum solidifying agent continuously fixes the eutectic phosphorus released by the phosphogypsum after solidification; the phosphogypsum solidifying agent is based on the principle of 'co-precipitation-net capture', slag and high-silicon aluminum solid waste are activated by an alkaline activator, and the generated CaF2 is coated to reduce the contact area in water, so that the F in the treated phosphogypsum can be stable and meet the standard; the effective sites can continuously combine the released eutectic phosphorus, prevent the migration of phosphorus in the environment, and make the treated phosphogypsum stable and meet the standard; the slag and high-silicon aluminum solid waste are used to treat the phosphogypsum, waste is treated by waste, and the treatment cost of the phosphogypsum is effectively reduced.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of phosphogypsum harmless treatment, and particularly relates to a phosphogypsum solidifying agent and a phosphogypsum harmless treatment method. BACKGROUND

[0002] Phosphogypsum is a by-product produced in the process of sulfuric acid decomposition of phosphate rock in wet-process phosphoric acid production, and contains impurities such as P, F, heavy metals and organic matter. Random stacking of phosphogypsum will cause serious pollution to the surrounding soil, water and atmosphere. Therefore, it is imperative to harmlessly treat phosphogypsum.

[0003] At present, the harmless treatment of phosphogypsum mainly aims at the soluble P and F in phosphogypsum. The precipitation method, i.e. adding calcium oxide to the phosphogypsum slurry, converts P and F into CaHPO4·2H2O, Ca3(PO4)2·2H2O and CaF2 to prevent their migration in the environment and achieve the harmless treatment of phosphogypsum. However, due to the influence of the solubility of CaF2, the removal of F ions is unstable, and the enterprises will invest in excessive lime treatment, resulting in a too high pH of the treated phosphogypsum. At the same time, the precipitation method will also produce a large amount of sludge, which needs to be disposed of additionally, thereby increasing the treatment cost. In addition, after the traditional precipitation method is used for treatment, there is still a eutectic phosphorus in the phosphogypsum, which will continue to be released during the stacking process, exceeding the first level standard in GB 8978-1996.

[0004] Based on the defects existing in the current phosphogypsum harmless treatment, it is necessary to improve it. SUMMARY

[0005] Therefore, the application provides a phosphogypsum solidifying agent and a phosphogypsum harmless treatment method to solve the defects existing in the prior art.

[0006] In a first aspect, the application provides a phosphogypsum solidifying agent, which comprises the following components by weight: 1-10 parts of a precipitant, 1-15 parts of a net trapping agent, 0.01-1 parts of an alkaline activator, 20-50 parts of slag and high-silicon aluminum solid waste.

[0007] Preferably, the phosphogypsum solidifying agent comprises at least one of calcium oxide, calcium chloride and calcium hydroxide.

[0008] Preferably, the phosphogypsum solidifying agent comprises at least one of sodium silicate, sodium aluminate and sodium cellulose acid.

[0009] Preferably, the phosphogypsum solidifying agent comprises at least one of sodium hydroxide, potassium hydroxide, sodium chloride and sodium sulfate.

[0010] Preferably, the phosphogypsum solidifying agent comprises at least one of fly ash, steel slag, red mud and yellow phosphorus slag.

[0011] In a second aspect, the present application also provides a phosphogypsum harmless treatment method, comprising the following steps:

[0012] Mixing the phosphogypsum and water to obtain a phosphogypsum slurry;

[0013] Adding any of the precipitants or network trapping agents to the phosphogypsum slurry and stirring to react;

[0014] Adding any of the alkaline activators and slag or high-silicon aluminum solid waste to the reacted phosphogypsum slurry, continuing to stir to react, and filtering to obtain harmless phosphogypsum.

[0015] Preferably, in the phosphogypsum harmless treatment method, the mass ratio of the phosphogypsum, water, precipitant, network trapping agent, alkaline activator, and slag or high-silicon aluminum solid waste is (100-1000):(300-3000):(1-10):(1-15):(0.01-1):(20-50).

[0016] Preferably, in the phosphogypsum harmless treatment method, any of the precipitants or network trapping agents is added to the phosphogypsum slurry, and stirring to react at room temperature for 15-30 min.

[0017] Preferably, in the phosphogypsum harmless treatment method, any of the alkaline activators and slag or high-silicon aluminum solid waste is added to the reacted phosphogypsum slurry, stirring to react at room temperature for 15-30 min, and filtering to obtain harmless phosphogypsum.

[0018] Preferably, in the phosphogypsum harmless treatment method, the phosphogypsum is washed phosphogypsum, and the soluble P content in the washed phosphogypsum is ≤0.3% and the soluble F content is ≤0.2% by mass based on P2O5.

[0019] Compared with the prior art, the present application has the following beneficial effects:

[0020] 1. The phosphogypsum solidifying agent of the present application has lower cost than previous agents mainly composed of calcium salt and solid waste, and continuously fixes the eutectic phosphorus released by the phosphogypsum after solidification is completed.

[0021] 2. The application is based on the mechanism of "co-precipitation-net capture", combined with slag, high-silicon aluminum solid waste, and a low-cost universal solidifying agent for the continuous and stable solidification of multi-form P and F in phosphogypsum is explored. After treatment, the phosphogypsum reaches the first level standard of "Integrated Wastewater Discharge Standard" GB 8978-1996, reduces the environmental protection pressure of enterprises, and has certain practical value. The application has mild use conditions and simple process flow, and effectively reduces the operating cost in the treatment process of phosphogypsum. DETAILED DESCRIPTION

[0022] The technical solutions in the embodiments of the application will be clearly and completely described below with reference to the embodiments of the application. Obviously, the described embodiments are only part of the embodiments of the application, rather than all the embodiments of the application. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the application.

[0023] It should be noted that the description order of the following embodiments is not limited as the preferred order of the embodiments. In addition, in the description of the present application, the term "comprising" means "including but not limited to". Various embodiments of the application can exist in the form of a range; it should be understood that the description in the form of a range is only for the convenience and brevity, and should not be understood as a rigid limitation on the scope of the application; therefore, it should be considered that the described range has been specifically disclosed all possible sub-ranges and single values in the range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers in the range, such as 1, 2, 3, 4, 5 and 6, regardless of the range. In addition, whenever a numerical range is indicated in this document, it means that any cited number (fraction or integer) in the indicated range is included.

[0024] The phosphogypsum solidifying agent provided by the embodiments of the present application comprises the following components: the following components by weight: 1-10 parts of a precipitating agent, 1-15 parts of a net capturing agent, 0.01-1 parts of an alkaline activator, 20-50 parts of slag, high-silicon aluminum solid waste.

[0025] In some embodiments, the precipitating agent comprises at least one of calcium oxide, calcium chloride, and calcium hydroxide.

[0026] In some embodiments, the net capturing agent comprises at least one of sodium silicate, sodium aluminate, and sodium cellulose.

[0027] In some embodiments, the alkaline activator comprises at least one of sodium hydroxide, potassium hydroxide, sodium chloride, and sodium sulfate.

[0028] In some embodiments, the slag, high-silicon aluminum solid waste includes at least one of fly ash, steel slag, red mud, and yellow phosphorus slag.

[0029] The phosphogypsum solidifying agent of the present application has lower cost than previous agents mainly composed of calcium salt and solid waste; and the phosphogypsum solidifying agent of the present application continuously fixes the released eutectic phosphorus of the phosphogypsum after solidification ends;

[0030] The phosphogypsum solidifying agent of the present application is based on the principle of "co-precipitation-net capture", the slag, high-silicon aluminum solid waste is activated by the alkaline activator, the generated CaF2 is coated to reduce the contact area in water, so that the F in the treated phosphogypsum can be stable and up to standard. The effective site can continuously combine the released eutectic phosphorus, prevent the migration of phosphorus in the environment, and make the treated phosphogypsum stable and up to standard. The slag, high-silicon aluminum solid waste is used to treat the phosphogypsum, which is waste treatment with waste, effectively reducing the treatment cost of the phosphogypsum.

[0031] Based on the same inventive concept, the present application also provides a harmless treatment method for phosphogypsum, comprising the following steps:

[0032] S1, mixing the phosphogypsum and water to obtain a phosphogypsum slurry;

[0033] S2, adding the above-mentioned precipitant and net capture agent to the phosphogypsum slurry and stirring to react;

[0034] S3, adding the above-mentioned alkaline activator and slag, high-silicon aluminum solid waste to the reacted phosphogypsum slurry, continuing to stir to react, and filtering to obtain harmless phosphogypsum.

[0035] In some embodiments, the mass ratio of phosphogypsum, water, precipitant, net capture agent, alkaline activator, slag, high-silicon aluminum solid waste is (100-1000):(300-3000):(1-10):(1-15):(0.01-1):(20-50).

[0036] In some embodiments, the above-mentioned precipitant and net capture agent are added to the phosphogypsum slurry, and stirred to react at room temperature for 15-30 min.

[0037] In some embodiments, the above-mentioned alkaline activator and slag, high-silicon aluminum solid waste are added to the reacted phosphogypsum slurry, and stirred to react at room temperature for 15-30 min, and filtered to obtain harmless phosphogypsum.

[0038] In some embodiments, the phosphogypsum is washed phosphogypsum, and the soluble P mass content in the washed phosphogypsum is ≤0.3% and the soluble F mass content is ≤0.2% based on P2O5.

[0039] The phosphogypsum solidifying agent is used for harmless treatment of phosphogypsum, and the obtained harmless phosphogypsum is prepared according to the sample preparation method of the leaching toxicity leaching method of solid waste, horizontal oscillation method HJ557, and the measured P, F and pH of the phosphogypsum reach the first level standard of the Comprehensive Sewage Discharge Standard GB 8978-1996, so that the harmless treatment of the phosphogypsum is realized.

[0040] The present application has the following characteristics:

[0041] 1. The present application is based on the mechanism of "co-precipitation-net capture", and slag, high-silicon aluminum solid waste are used to explore a low-cost general-purpose solidifying agent that can be used for the continuous and stable solidification of multiple forms of P and F in phosphogypsum. The treated phosphogypsum reaches the first level standard of the Comprehensive Sewage Discharge Standard GB 8978-1996, thereby reducing the environmental protection pressure of enterprises and having certain practical value.

[0042] 2. The present application has mild use conditions and simple process flow, and effectively reduces the operating cost in the treatment process of phosphogypsum.

[0043] The following further illustrates the phosphogypsum solidifying agent and the phosphogypsum harmless treatment method of the present application with specific examples. This part further illustrates the content of the present application in combination with specific examples, but should not be understood as a limitation of the present application. If not specifically stated, the technical means used in the examples is the conventional means familiar to those skilled in the art. Unless specifically stated, the reagents, methods and equipment used in the present application are the conventional reagents, methods and equipment in the art.

[0044] Example 1

[0045] The present application provides a phosphogypsum harmless treatment method, which comprises the following steps:

[0046] S1, 100g of water-washed phosphogypsum and 300g of water are mixed and beaten to obtain a phosphogypsum slurry;

[0047] S2, a precipitating agent (a mixture of 1.8g of calcium oxide and 0.3g of calcium chloride), a net capturing agent (a mixture of 0.7g of sodium aluminate and 0.2g of sodium cellulose acid) are added to the phosphogypsum slurry in S1, and stirred and reacted at room temperature (25℃) for 15min;

[0048] S3, an alkaline activator (a mixture of 0.05g of sodium hydroxide and 0.5g of sodium chloride), 2g of fly ash are added to the phosphogypsum slurry after reaction in S2, and the stirring and reaction is continued at room temperature (25℃) for 15min, and then solid-liquid separation is performed, and the obtained solid is harmless phosphogypsum.

[0049] Example 2

[0050] The present application provides a phosphogypsum harmless treatment method, which comprises the following steps:

[0051] S1, 500g of washed phosphogypsum and 1500g of water were mixed to obtain a phosphogypsum slurry;

[0052] S2, a precipitating agent (a mixture of 10g of calcium oxide and 1.5g of calcium chloride), a network trapping agent (a mixture of 3.8g of sodium aluminate and 1.1g of sodium cellulose acid) were added to the phosphogypsum slurry in S1, and stirred at room temperature (25℃) for 15min;

[0053] S3, an alkaline activator (a mixture of 0.5g of sodium hydroxide and 2.5g of sodium chloride), 6g of fly ash, and 4g of red mud were added to the phosphogypsum slurry after reaction in S2, and continued to be stirred at room temperature (25℃) for 20min, and then solid-liquid separation was performed, and the obtained solid was the harmless phosphogypsum.

[0054] Example 3

[0055] The example of the present application provides a harmless treatment method of phosphogypsum, comprising the following steps:

[0056] S1, 1000g of washed phosphogypsum and 3000g of water were mixed to obtain a phosphogypsum slurry;

[0057] S2, a precipitating agent (a mixture of 20g of calcium oxide and 3.2g of calcium chloride), a network trapping agent (a mixture of 7g of sodium aluminate and 2g of sodium cellulose acid) were added to the phosphogypsum slurry in S1, and stirred at room temperature (25℃) for 15min;

[0058] S3, an alkaline activator (a mixture of 1g of sodium hydroxide and 5g of sodium chloride), 10g of fly ash, and 1g of steel slag were added to the phosphogypsum slurry after reaction in S2, and continued to be stirred at room temperature (25℃) for 15min, and then solid-liquid separation was performed, and the obtained solid was the harmless phosphogypsum.

[0059] Comparative Example 1

[0060] The comparative example provides a harmless treatment method of phosphogypsum, comprising the following steps:

[0061] S1, 500g of washed phosphogypsum and 1500g of water were mixed to obtain a phosphogypsum slurry;

[0062] S2, 20g of calcium oxide was added to the phosphogypsum slurry in S1, and stirred at room temperature (25℃) for 30min, and then filtration was performed to obtain the harmless phosphogypsum, and it was measured that the P (calculated as P) in the harmless phosphogypsum was 0.09mg / L, and the F was 17.2mg / L.

[0063] The soluble P (calculated as P, (mg / L)), soluble F (mg / L) content in the phosphogypsum after water washing in step S1 of the experimental test of Examples 1-3 and Comparative Example 1, and the soluble P (calculated as P, (mg / L)), soluble F (mg / L) content and pH value in the harmless phosphogypsum obtained by the method of Examples 1-3 and Comparative Example 1 were tested, and the results are shown in Table 1 below.

[0064] The test method of soluble P and soluble F is as follows:

[0065] Sample preparation:

[0066] First, the phosphogypsum samples before and after treatment were prepared according to the sample preparation standard (HJ 557-2010 Solid Waste Leaching Toxicity Leaching Method Horizontal Oscillation Method) cited in GB 18599-2020 General Industrial Solid Waste Storage and Filling Pollution Control Standard.

[0067] Soluble P detection:

[0068] The water quality analyzer was used to determine the content of phosphorus in the leaching solution according to HJ 671-2013 Water Quality Determination of Total Phosphorus Flow Injection-Ammonium Molybdate Spectrophotometric Method.

[0069] Soluble F detection:

[0070] The content of fluorine in the leaching solution was determined according to GB / T 7484-1987 Water Quality Determination of Fluoride Ion Selective Electrode Method.

[0071] pH test, the pH value of the leaching solution is the pH value of the phosphogypsum.

[0072] Table 1-Content of P and F in the harmless phosphogypsum obtained by Examples 1-3 and Comparative Example 1

[0073]

[0074] The content of P and F in the harmless phosphogypsum obtained in Example 1 was tested, and the results after 90 days were tracked, as shown in Table 2 below.

[0075] Table 2-Results of P and F tracking for 90 days in the harmless phosphogypsum obtained by Example 1

[0076]

[0077] The content of P and F in the harmless phosphogypsum obtained in Comparative Example 1 was tested, and the results after 14 days were tracked, as shown in Table 3 below.

[0078] Table 3-Results of P and F tracking for 14 days in the harmless phosphogypsum obtained by Comparative Example 1

[0079]

[0080] As can be seen from Tables 1-3, the phosphogypsum treated by only adding calcium oxide is difficult to meet the requirement of F in the "Integrated Wastewater Discharge Standard" GB 8978-1996, while the phosphogypsum treated by the solidifying agent can meet the requirements of P, F and pH in GB 8978, and the long-term tracking monitoring results show that the phosphogypsum treated by the solidifying agent still meets the requirements of GB 8978.

[0081] The above only describes the preferred embodiments of the present application and is not used to limit the present application, and any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for harmless treatment of phosphogypsum, which is a by-product produced in the process of sulfuric acid digestion of phosphate rock in the production of wet-process phosphoric acid, characterized in that, The method comprises the following steps: mixing phosphogypsum and water to obtain a phosphogypsum slurry; adding a precipitant and a network trapping agent to the phosphogypsum slurry and stirring to react; adding an alkaline activator and a slag and high-silicon aluminum solid waste to the reacted phosphogypsum slurry, continuing to stir to react, and filtering to obtain harmless phosphogypsum; the mass ratio of the phosphogypsum, water, precipitant, network trapping agent, alkaline activator, and slag and high-silicon aluminum solid waste is (100-1000):(300-3000):(1-10):(1-15):(0.01-1):(20-50); the precipitant comprises calcium oxide and calcium chloride; the network trapping agent comprises sodium aluminate and sodium cellulose; the alkaline activator comprises sodium hydroxide and sodium chloride; the slag and high-silicon aluminum solid waste comprises at least one of fly ash, steel slag, and red mud; the precipitant and network trapping agent are added to the phosphogypsum slurry, and stirring to react at room temperature for 15-30 min; the alkaline activator and slag and high-silicon aluminum solid waste are added to the reacted phosphogypsum slurry, stirring to react at room temperature for 15-30 min, and filtering to obtain harmless phosphogypsum; the phosphogypsum is washed with water, and the soluble P content in the washed phosphogypsum is ≤0.3% and the soluble F content is ≤0.2% in terms of P2O5.

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