Rapid curing agent for phosphorus and fluorine in phosphogypsum and harmless method

Abstract

The invention discloses a rapid curing agent for phosphorus and fluorine in phosphogypsum and a harmless method. The rapid curing agent for phosphorus and fluorine in phosphogypsum is composed of an alkaline neutralizer, a calcium-aluminum salt catalyst and a solvent. The alkaline neutralizer realizes accurate pH regulation and control of the phosphogypsum leaching solution system; the calcium-aluminum salt catalyst synchronously captures soluble phosphorus, soluble fluorine and heavy metal ions; the solvent ensures proper humidity of the curing agent reaction. According to the innocent treatment method for the ardealite, the curing rate of soluble phosphorus in the ardealite reaches 99.2% and the leaching concentration of soluble fluorine is lower than 1.5 mg / L within 3 days through the processes of crushing and homogenizing the ardealite raw slag, stirring and curing and controllable aging. According to the technology, the technical problems of long reaction period, long on-site mixing time, low synergistic fixation efficiency of soluble phosphorus and fluorine and difficulty in capturing heavy metal ions in most phosphogypsum harmless treatment technologies are solved, the treated phosphogypsum can stably reach the standard, and the treatment cost is effectively reduced by treating the phosphogypsum with the red mud and fly ash solid waste.

Description

Technical Field

[0001] The present invention belongs to the technical field of harmless treatment of industrial phosphogypsum, and specifically relates to a rapid curing agent for phosphorus and fluorine in phosphogypsum and a harmless treatment method. Background Art

[0002] Phosphogypsum is a solid waste generated in the wet-process phosphoric acid industry, and its main component is calcium sulfate dihydrate. For every 1 ton of phosphoric acid produced, 4 - 6 tons of phosphogypsum are generated. By 2024, the stockpile of phosphogypsum exceeded 800 million tons, and the annual production of phosphogypsum is about 80 million tons. Soluble phosphorus, fluorine, and heavy metal ions pollute the environment under the influence of factors such as wind erosion and rain erosion. Therefore, the harmless treatment of phosphogypsum has become a research hotspot in the treatment field.

[0003] In the traditional lime neutralization method for treating phosphogypsum, soluble phosphorus, fluorine, and heavy metal ions react with calcium hydroxide to form insoluble precipitates. Experimental results show that the lime neutralization method has a slow curing rate and low efficiency. Therefore, it is necessary to explore new high-efficiency curing agents to further improve the curing rate of soluble phosphorus, fluorine, and heavy metal ions in order to achieve the harmless treatment of phosphogypsum. Summary of the Invention

[0004] One of the purposes of the present invention is to provide a rapid curing agent for phosphorus and fluorine in phosphogypsum.

[0005] Another purpose of the present invention is to provide a harmless treatment method for phosphogypsum using the said curing agent.

[0006] The present invention provides a rapid curing agent for phosphorus and fluorine in phosphogypsum, which is composed of an alkaline neutralizer, a calcium-aluminum salt catalyst, and a solvent.

[0007] The mass ratio of the alkaline neutralizer, the calcium-aluminum salt catalyst, and the solvent is (0.5 - 10):(0.05 - 5):(5 - 20).

[0008] Further, the alkaline neutralizer is one or more of calcium oxide, red mud, and fly ash in any ratio mixture.

[0009] Further, the calcium-aluminum salt catalyst is one or more of calcium-aluminum layered double hydroxides and calcium-aluminum layered double hydroxides after high-temperature calcination in any ratio mixture.

[0010] Preferably, the preparation method of the calcium-aluminum layered double hydroxide after high-temperature calcination is: calcining the calcium-aluminum layered double hydroxide at a calcination temperature of 300 - 500 °C for 0.5 - 3 h.

[0011] Further, the solvent is water.

[0012] The present invention also provides a harmless treatment method for phosphogypsum using the said curing agent, including the following steps:

[0013] S1. Crush and homogenize the original phosphogypsum residue to obtain powdered phosphogypsum;

[0014] S2. Mix and stir the curing agent and the powdered phosphogypsum at room temperature to obtain pretreated phosphogypsum;

[0015] S3. Age the pretreated phosphogypsum to complete the harmless treatment of phosphogypsum.

[0016] Furthermore, in step S1, the water content of the original phosphogypsum residue is 8-11%; the particle size of the powdered phosphogypsum is 200 mesh - 400 mesh;

[0017] Furthermore, in step S2, the process conditions of the mixing and stirring reaction are: the stirring rate is 115 - 295 revolutions per minute, and the stirring time is 15 - 30 min.

[0018] In step S2, based on the mass of the powdered phosphogypsum, the addition amount of the alkaline neutralizer in the curing agent is 0.5% - 10% of the mass of the phosphogypsum, the addition amount of the calcium-aluminum salt catalyst is 0.05% - 5% of the mass of the phosphogypsum, and the addition amount of the solvent is 5% - 20% of the mass of the phosphogypsum.

[0019] Furthermore, in step S3, the aging time is 1 - 15 days.

[0020] Principle of the present invention:

[0021] In the present invention, the large lumps in the original phosphogypsum residue are first broken up to ensure that subsequent agents can migrate between phosphogypsum particles, and then the curing agent is added. The alkaline neutralizer in the curing agent can regulate the alkalinity of the phosphogypsum system (pH = between 9 - 10.5), ensuring the release of hydrogen ions in dihydrogen phosphate and hydrogen phosphate ions. Calcium ions, aluminum ions, iron ions, etc. contained in the alkaline neutralizer can form insoluble or poorly soluble precipitates with phosphate and fluoride ions. The calcium-aluminum salt catalyst can fix soluble phosphorus, soluble fluoride, and heavy metal ions through ion exchange and complexation reactions. The calcium-aluminum salt catalyst undergoes ion exchange and surface complexation with harmful components such as soluble phosphorus and fluoride in the phosphogypsum through the high specific surface area of its layered structure, and at the same time fixes heavy metal ions through the intercalation effect of interlayer anions, realizing the efficient and stable fixation of harmful components. The addition of the solvent ensures the wettability of the phosphogypsum sample mixture. Without a suitable micro-wetting environment, the reaction cannot be effectively carried out. However, the addition amount of the solvent should not be too high. When the water content in the original phosphogypsum plus the addition amount of the solvent exceeds 28% of the mass of the powdered phosphogypsum, the stirred sample will become a slurry state and is not suitable for stacking.

[0022] Beneficial effects of the present invention:

[0023] (1) The present invention can significantly improve the pH value of the phosphogypsum system by using alkaline neutralizers such as calcium oxide, red mud and fly ash, and can efficiently fix more than 98% of soluble phosphorus and fluorine, forming insoluble or slightly soluble substances such as calcium phosphate, iron phosphate, calcium fluoride and aluminum fluoride in a very short time;

[0024] (2) The present invention can achieve ultra-high-efficiency solidification of soluble phosphorus, fluorine and heavy metals in phosphogypsum through the synergistic effect of calcium aluminum salt catalyst, and its fixation efficiency can be controlled within 15 days, which is a relatively fast rate;

[0025] (3) The present invention realizes a single-feeding process, without the need to add alkaline neutralizers and calcium aluminum salt catalysts in batches, and without the need to pre-adjust the alkalinity of the system. All reagents can be added at one time and the reaction can be completed quickly, shortening the traditional harmless treatment process that takes several hours to less than 30 minutes, and rapidly improving the treatment efficiency;

[0026] (4) The process of the present invention is extremely simple, the cost of the harmless treatment reagents used is relatively low and the raw materials are easily available, and the harmless treatment of phosphogypsum can be achieved immediately and efficiently, which has significant advantages in industrial promotion. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of the process flow of the present invention;

[0028] Figure 2 is a composition diagram of red mud in an embodiment of the present invention;

[0029] Figure 3 is a composition diagram of fly ash in an embodiment of the present invention;

[0030] Figure 4 This is a SEM image of the calcium aluminum layered double hydroxide in an embodiment of the present invention;

[0031] Figure 5 This is a SEM image of the calcium aluminum layered double hydroxide after high temperature calcination in an embodiment of the present invention;

[0032] Figure 6 1 is an XRD diagram of the calcium aluminum layered double hydroxide and the calcium aluminum layered double hydroxide after high-temperature calcination in the embodiment of the present invention. DETAILED DESCRIPTION

[0033] The following further illustrates the phosphorus and fluorine rapid curing agent and harmless method in phosphogypsum of the present application with specific examples. The present invention is further illustrated below in conjunction with the examples, but is not intended to be a basis for limiting the present invention. Unless otherwise specified, the technical means used in the examples are conventional means well known to those skilled in the art. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the art.

[0034] In the embodiments of the present invention, the original phosphogypsum residue used is the phosphogypsum residue from the Longjingwan Phosphogypsum Yard in Guizhou City.

[0035] The calcium-aluminum layered double hydroxide used is purchased directly.

[0036] The calcium-aluminum layered double hydroxide after high-temperature calcination used is obtained by calcining the calcium-aluminum layered double hydroxide at a calcination temperature of 500 °C for 30 minutes.

[0037] Example 1

[0038] The present invention provides a method for harmless treatment of phosphogypsum, and the schematic process flow diagram is as Figure 1 shown, including the following steps:

[0039] Take 200 g of the original phosphogypsum residue, and obtain powdery phosphogypsum with a particle size of 200 mesh after crushing and homogenization;

[0040] Add the alkaline neutralizer (3 g of calcium oxide, 6 g of red mud and 2 g of fly ash) and the calcium-aluminum salt catalyst (0.4 g of calcium-aluminum layered double hydroxide) to the powdery phosphogypsum;

[0041] Stir the powdery phosphogypsum mixed with the alkaline neutralizer and the calcium-aluminum salt catalyst at room temperature at a speed of 295 revolutions per minute for 20 minutes, and add 20 mL of water during the stirring.

[0042] The composition diagram of the red mud used is as Figure 2 shown, and the composition diagram of the fly ash is as Figure 3 shown.

[0043] The SEM diagram of the calcium-aluminum layered double hydroxide used is as Figure 4 shown.

[0044] Example 2

[0045] Compared with Example 1, in this example, only the calcium-aluminum salt catalyst is replaced from 0.4 g of calcium-aluminum layered double hydroxide to 0.4 g of calcium-aluminum layered double hydroxide after high-temperature calcination, and the other conditions remain unchanged.

[0046] The SEM diagram of the calcium-aluminum layered double hydroxide after high-temperature calcination used is as Figure 5 shown.

[0047] X-ray diffraction is performed on the calcium-aluminum layered double hydroxide and the calcium-aluminum layered double hydroxide after high-temperature calcination to obtain the XRD diagrams of the calcium-aluminum layered double hydroxide and the calcium-aluminum layered double hydroxide after high-temperature calcination, as Figure 6 shown.

[0048] Example 3

[0049] Compared with Example 1, in this example, the alkaline neutralizer is replaced from (3 g of calcium oxide, 6 g of red mud, and 2 g of fly ash) to (3 g of calcium oxide, 3 g of red mud, and 2 g of fly ash), and the water added during stirring is changed from 20 ml to 30 ml, with other conditions remaining unchanged.

[0050] The leachate of phosphogypsum treated harmlessly in Examples 1 - 3 was detected, and the index results at different times are shown in Table 1.

[0051] Table 1 Index results of the leachate of phosphogypsum treated harmlessly in Examples 1 - 3

[0052]

[0053] The heavy metal indexes such as soluble fluorine, soluble phosphorus, hexavalent chromium, mercury, arsenic, chromium, and lead in the leachate of phosphogypsum treated in Examples 1 - 3 were detected, and the detection results are shown in Table 2. Among them, the results of Example 1 and Example 2 were detected after 13 days of aging, and the result of Example 3 was detected after 10 days of aging.

[0054] Table 2 Detection results of heavy metal indexes in the harmless treatment of phosphogypsum in Examples 1 - 3

[0055] Monitoring factor Unit Original phosphogypsum Example 1 of the present invention Example 2 of the present invention Example 3 of the present invention Standard limit pH Dimensionless 1.8 8.53 8.12 8.09 6-9 Soluble fluorine mg / L 76 1.58 3.12 1.57 10 Soluble phosphorus mg / L 126 0.04 0.04 0.05 0.5 Hexavalent chromium mg / L 0.03 0.005 0.006 0.0035 0.5 Mercury mg / L 0.02 0.035 0.022 0.025 0.05 Arsenic mg / L 0.2 0.003 0.004 0.004 0.5 Chromium mg / L 0.03 0.008 0.007 0.004 1.5 Cadmium mg / L 0.03 0.0004 0.0002 0.00017 0.1 Lead mg / L 0.1 0.0035 0.0015 0.0008 1.0

[0056] From the results in Table 1 and Table 2, it can be seen that the harmless treatment of phosphogypsum in the present invention meets the technical index requirements of Class I general industrial solid waste in the "Pollution Control Standards for Storage and Landfill of General Industrial Solid Wastes" (GB 18599 - 2020).

[0057] As mentioned above, the above is only the preferred specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, makes equivalent substitutions or changes, and should be covered by the protection scope of the present invention.

Claims

1. A rapid curing agent for phosphorus and fluorine in phosphogypsum, characterized in that, The curing agent is composed of an alkaline neutralizer, a calcium-aluminum salt catalyst and a solvent; the solvent is water.

2. The rapid curing agent for phosphorus and fluorine in phosphogypsum according to claim 1, wherein The mass ratio of the alkaline neutralizer, the calcium-aluminum salt catalyst and the solvent is (0.5-10):(0.05-5):(5-20).

3. The quick curing agent for phosphorus and fluorine in phosphogypsum according to claim 1, characterized in that, The alkaline neutralizer is any ratio mixture of one or more of calcium oxide, red mud and fly ash.

4. The quick curing agent for phosphorus and fluorine in phosphogypsum according to claim 1, characterized in that, The calcium-aluminum salt catalyst is any ratio mixture of one or more of calcium-aluminum layered double hydroxides and calcium-aluminum layered double hydroxides after high-temperature calcination.

5. The quick curing agent for phosphorus and fluorine in phosphogypsum according to claim 3, characterized in that, The preparation method of the calcium-aluminum layered double hydroxide after high-temperature calcination is: calcine the calcium-aluminum layered double hydroxide at a calcination temperature of 300-500 °C for 0.5-3 h.

6. A method for harmless treatment of phosphogypsum using the phosphorus and fluorine quick curing agent described in any one of claims 1 to 5, characterized in that, It includes the following steps: S1. Crush and homogenize the raw phosphogypsum slag to obtain powdered phosphogypsum; S2. Mix and stir the curing agent and the powdered phosphogypsum at room temperature to obtain pretreated phosphogypsum; S3. Age the pretreated phosphogypsum to complete the harmless treatment of phosphogypsum.

7. The harmless method according to claim 6, characterized in that, In step S1, the water content of the raw phosphogypsum slag is 8-11%; the particle size of the powdered phosphogypsum is 200 mesh - 400 mesh.

8. The harmless method according to claim 6, characterized in that, In step S2, the process conditions of the mixing and stirring reaction are: the stirring rate is 115-295 revolutions per minute, and the stirring time is 15-30 min.

9. The harmless method according to claim 6, characterized in that, In step S2, based on the mass of the powdered phosphogypsum, the addition amount of the alkaline neutralizer in the curing agent is 0.5%-10% of the mass of the phosphogypsum, the addition amount of the calcium-aluminum salt catalyst is 0.05%-5% of the mass of the phosphogypsum, and the addition amount of the solvent is 5%-20% of the mass of the phosphogypsum.

10. The harmless method according to claim 6, wherein In step S3, the aging time is 1-15 days.

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