Harmless treatment process of semi-hydrated phosphogypsum and application of harmless phosphogypsum

Abstract

The invention belongs to the field of environmental protection, and particularly relates to a harmless treatment process of semi-hydrated phosphogypsum and application of harmless phosphogypsum. The semi-hydrated phosphogypsum harmless treatment process provided by the invention comprises the following steps: a) adjusting the pH value and the water content of a semi-hydrated phosphogypsum raw material to obtain adjusted semi-hydrated phosphogypsum; in the step a), a reagent used for adjusting the pH value is a calcareous alkaline agent; the pH value of the adjusted semi-hydrated phosphogypsum is 10-11, and the water content of the adjusted semi-hydrated phosphogypsum is 25-30 wt%; and b) stacking the adjusted semi-hydrated phosphogypsum to form a conical or cone-like stack, and stacking for a period of time to obtain the harmless phosphogypsum. The harmless treatment process provided by the invention is simple in flow, low in cost, high in efficiency, small in pollution and suitable for large-scale application.

Description

Technical Field

[0001] The invention belongs to the field of environmental protection, and in particular relates to a harmless treatment process of hemihydrate phosphogypsum and application of the harmless phosphogypsum. Background Art

[0002] The phosphogypsum produced as a byproduct of the wet-process phosphoric acid plant contains water-soluble phosphorus, eutectic phosphorus, and water-soluble fluorine impurities. During the storage process, harmful ions migrate to the surrounding environment with rainwater, causing water and soil pollution. It is imperative for phosphorus chemical-related enterprises to dispose of the phosphogypsum harmlessly. The semi-aqueous wet-process phosphoric acid plant has a high acid concentration, which can reduce energy consumption during the acid concentration process. With the production of high value-added product acid, the selection of the semi-aqueous wet-process phosphoric acid process is the future trend, and the disposal of the byproduct semi-aqueous phosphogypsum has become a top priority.

[0003] At present, the main methods for harmless disposal of phosphogypsum include purified water washing, lime neutralization modification, sintering solidification, and multi-agent coordinated harmless disposal.

[0004] (1) Purification water washing can remove impurities such as phosphorus and fluorine in phosphogypsum, but eutectic phosphorus is difficult to remove by water washing. Water-washed gypsum still contains a small amount of phosphorus and fluorine, which cannot meet the requirements of Class I solid waste standards. In addition, phosphogypsum washing water causes secondary pollution.

[0005] (2) Lime neutralizes and modifies phosphogypsum. The soluble phosphorus and fluorine in the phosphogypsum are solidified into insoluble phosphorus and fluorine. However, the solidification efficiency of lime for fluorine is low and the reaction time is long. In addition, the eutectic phosphorus in gypsum is slowly released, posing a long-term environmental pollution risk.

[0006] (3) After high-temperature calcination, the soluble phosphorus in the gypsum is sintered to form tricalcium phosphate, and the soluble fluorine overflows in the form of gas. However, high-temperature calcination consumes a lot of energy, which increases the processing cost.

[0007] (4) The coordinated use of multiple agents can effectively solidify water-soluble impurities such as phosphorus and fluorine in gypsum. Adding multiple agents for solidification increases the cost of disposing of phosphogypsum.

[0008] There are many problems with the above treatment methods. The harmless modification of phosphogypsum has high requirements for leaching indicators, and multiple treatment methods need to be coordinated to meet the harmless disposal index requirements. Summary of the invention

[0009] In view of this, the purpose of the present invention is to provide a harmless treatment process for hemihydrate phosphogypsum and the application of harmless phosphogypsum. The harmless treatment process provided by the present invention has a simple process, low cost, high efficiency, low pollution, and is suitable for large-scale application.

[0010] The present invention provides a harmless treatment process for hemihydrate phosphogypsum, comprising the following steps:

[0011] a) adjusting the pH value and moisture content of the semi-hydrated phosphogypsum raw material to obtain adjusted semi-hydrated phosphogypsum;

[0012] In step a), the reagent used to adjust the pH value is a calcium alkaline agent; after the adjustment, the pH value of the hemihydrate phosphogypsum is 10-11, and the water content is 25-30wt%;

[0013] b) piling the adjusted hemihydrate phosphogypsum to form a conical or quasi-conical pile, and after piling for a period of time, obtaining harmless phosphogypsum.

[0014] Preferably, in step a), the calcic alkaline agent is quicklime.

[0015] Preferably, in step a), the amount of the calcic alkaline agent used accounts for 1-3% of the total mass of the hemihydrate phosphogypsum raw material and the calcic alkaline agent.

[0016] Preferably, in step b), the weight of the pile is 800-1200t.

[0017] Preferably, in step b), the ratio of the diameter to the height of the pile is (3-3.5):1.

[0018] Preferably, in step b), the temperature of the pile during the storage process is 75-90°C.

[0019] Preferably, in step b), the storage time is ≤ 3 days.

[0020] Preferably, in step a), the free water content of the hemihydrate phosphogypsum raw material is 15-25wt%, the crystal water content is 6-7.5wt%, the pH value is 2.5-4.5, and the temperature is 50-70°C.

[0021] Preferably, the method further comprises the following step: crushing the harmless phosphogypsum obtained in step b).

[0022] The present invention also provides an application of harmless phosphogypsum obtained by the harmless treatment process described in the above technical solution in ecological restoration or mine filling.

[0023] Compared with the prior art, the present invention provides a harmless treatment process for hemihydrate phosphogypsum and the application of harmless phosphogypsum. The harmless treatment process for hemihydrate phosphogypsum provided by the present invention comprises the following steps: a) adjusting the pH value and water content of the hemihydrate phosphogypsum raw material to obtain adjusted hemihydrate phosphogypsum; in step a), the reagent used to adjust the pH value is a calcium alkaline agent; the pH value of the adjusted hemihydrate phosphogypsum is 10-11, and the water content is 25-30wt%; b) piling the adjusted hemihydrate phosphogypsum to form a conical or quasi-conical pile, and after piling for a period of time, harmless phosphogypsum is obtained. In the present invention, the hemihydrate phosphogypsum is hydrated into dihydrate gypsum during the storage process, and the dihydrate gypsums overlap each other to form a whole. Based on the poor thermal conductivity of gypsum, the heat released by the hydration of the hemihydrate phosphogypsum is utilized to form a high-temperature and high-humidity reaction environment by the stack body. Under this working condition, as the gypsum phase recrystallizes, eutectic phosphorus and intercrystalline phosphorus and fluorine are rapidly released, and the water-soluble phosphorus and water-soluble fluorine remaining in the gypsum react with the calcic alkaline agent to solidify. The curing reaction process is greatly accelerated under the high-temperature and high-humidity environment, and the calcic alkaline agent and fluoride react rapidly under this condition to form insoluble substances. In summary, the treatment process provided by the present invention utilizes hydration recrystallization on the one hand to continuously release eutectic phosphorus and intercrystalline phosphorus and fluorine in hemihydrate phosphogypsum; on the other hand, it utilizes hydration heat to accelerate the hydration of hemihydrate phosphogypsum and the release of harmful substances and form a high-temperature and high-humidity pile environment. Under high temperature and humidity environment, the reaction rate of calcium alkaline agent with fluorine and phosphorus elements is accelerated, and a stable solidified product is formed, thereby significantly improving the harmless treatment efficiency and treatment effect of hemihydrate phosphogypsum. The experimental results show that after hemihydrate phosphogypsum is stored for 3 days using the treatment process provided by the present invention, the phosphorus element (in terms of P) leached from the phosphogypsum is less than 0.5 mg / L, fluoride is less than 10 mg / L, and the pH is 6 to 9, which meets the requirements of the general industrial solid waste index of Class I in the General Industrial Solid Waste Storage and Landfill Pollutant Control Standard GB18599-2020. DETAILED DESCRIPTION

[0024] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] The present invention provides a harmless treatment process for hemihydrate phosphogypsum, comprising the following steps:

[0026] a) adjusting the pH value and moisture content of the semi-hydrated phosphogypsum raw material to obtain adjusted semi-hydrated phosphogypsum;

[0027] b) piling the adjusted hemihydrate phosphogypsum to form a conical or quasi-conical pile, and after piling for a period of time, obtaining harmless phosphogypsum.

[0028] In the treatment process provided by the present invention, in step a), the hemihydrate phosphogypsum raw material is hemihydrate phosphogypsum produced by a hemihydrate wet-process phosphoric acid device; the total P2O5 content of the hemihydrate phosphogypsum raw material is preferably 0.5-2wt%, specifically 0.5wt%, 0.83wt%, 1wt%, 1.27wt%, 1.5wt% or 2wt%; the water-soluble P2O5 content of the hemihydrate phosphogypsum raw material is preferably 0.1-1wt%, specifically 0.1wt%, 0.3wt%, 0.4wt%, 0.6wt%, 0.83wt%, 1.27wt%, 1.5wt% or 2wt%. 0.36wt%, 0.5wt%, 0.59wt%, 0.7wt% or 1wt%; the total F content of the hemihydrate phosphogypsum raw material is preferably 0.2-1wt%, specifically 0.2wt%, 0.43wt%, 0.5wt%, 0.7wt%, 0.83wt% or 1wt%; the water-soluble F content of the hemihydrate phosphogypsum raw material is preferably 0.1-0.5wt%, specifically 0.1wt%, 0.16wt%, 0.2wt%, 0.3wt% %, 0.4wt% or 0.5wt%; the eutectic phosphorus content of the semi-hydrated phosphogypsum raw material is preferably 0.1-0.5wt%, specifically 0.1wt%, 0.2wt%, 0.3wt%, 0.4wt%, 0.42wt% or 0.5wt%; the free water content of the semi-hydrated phosphogypsum raw material is preferably 15-25wt%, specifically 15wt%, 20wt%, 20.91wt%, 22.16wt% or 25wt%; the semi-hydrated phosphogypsum raw material The crystal water content is preferably 6-7.5wt%, specifically 6wt%, 6.5wt%, 6.64wt%, 6.8wt%, 7wt% or 7.5wt%; the pH value of the hemihydrate phosphogypsum raw material is preferably 2.5-4.5, specifically 2.5, 3, 3.1, 3.5, 4, 4.06 or 4.5; the temperature of the hemihydrate phosphogypsum raw material is preferably 50-70°C, specifically 50°C, 55°C, 60°C, 61°C, 63°C, 65°C or 70°C.

[0029] In the treatment process provided by the present invention, in step a), the reagent used to adjust the pH value is a calcic alkaline agent; the calcic alkaline agent is preferably quicklime; the amount of the calcic alkaline agent preferably accounts for 1 to 3% of the total mass of the hemihydrate phosphogypsum raw material and the calcic alkaline agent, specifically 1%, 1.2%, 1.5%, 1.7%, 2%, 2.3%, 2.5%, 2.7% or 3%.

[0030] In the treatment process provided by the present invention, in step a), the pH value of the adjusted hemihydrate phosphogypsum is 10-11, specifically 10, 10.1, 10.2, 10.3, 10.4, 10.5, 10.6, 10.7, 10.8, 10.9 or 11; the moisture content of the adjusted hemihydrate phosphogypsum is preferably 25-30wt%, specifically 25wt%, 25.5wt%, 26wt%, 26.5wt%, 27wt%, 27.5wt%, 28wt%, 28.5wt%, 29wt%, 29.5wt% or 30wt%.

[0031] In the treatment process provided by the present invention, in step b), the weight of the pile is preferably 800-1200t, specifically 800t, 900t, 1000t, 1100t or 1200t; the ratio of the diameter to the height of the pile is preferably (3-3.5):1, specifically 3:1, 3.1:1, 3.2:1, 3.3:1, 3.4:1 or 3.5:1.

[0032] In the treatment process provided by the present invention, in step b), during the storage process, the hemihydrate phosphogypsum is hydrated into a dihydrate phase, and the dihydrate gypsum crystals overlap each other to form a relatively dense pile; at the same time, the eutectic phosphorus and intercrystalline phosphorus and fluorine in the gypsum are rapidly released along with the recrystallization process of the gypsum phase. The thermal conductivity of phosphogypsum is low, and it has good heat insulation and heat preservation properties. By utilizing the temperature and moisture of the hemihydrate phosphogypsum, as well as the heat release of the hemihydrate phosphogypsum hydration and the heat release of the quicklime slaking, a high-temperature and high-humidity reaction environment can be formed in the phosphogypsum pile. In this environment, the water-soluble phosphorus and fluorine in the phosphogypsum react and solidify rapidly with the calcium alkaline agent.

[0033] In the treatment process provided by the present invention, in step b), the temperature of the pile during the storage process is preferably 75-90°C, specifically 75°C, 76°C, 77°C, 78°C, 79°C, 80°C, 81°C, 82°C, 83°C, 84°C, 85°C, 86°C, 87°C, 88°C, 89°C or 90°C; the storage time is preferably ≤3d, specifically 6h, 12h, 18h, 1d, 1.5d, 2d, 2.5d or 3d.

[0034] In the treatment process provided by the present invention, it is preferred that the following step is also included: crushing the harmless phosphogypsum obtained in step b).

[0035] The present invention also provides an application, specifically applying the harmless phosphogypsum obtained by the harmless treatment process described in the above technical solution to ecological restoration or mine filling.

[0036] The technical solution provided by the present invention adds a calcium alkaline agent to the semi-hydrated phosphogypsum produced as a by-product of the wet phosphoric acid process, and uses the hydration reaction of the phosphogypsum pile-hydration heat to construct a high-temperature and high-humidity reaction environment to solidify phosphorus and fluorine, so that phosphogypsum that meets the requirements of harmlessness index can be obtained in a short time. More specifically, the technical solution provided by the present invention has at least the following advantages:

[0037] (1) Based on the hydration and recrystallization of hemihydrate phosphogypsum, eutectic phosphorus and intercrystalline phosphorus and fluorine are released, avoiding the risk of long-term environmental pollution caused by slow release.

[0038] (2) By utilizing the hydration heat, the temperature and moisture brought out of the semi-hydrated phosphogypsum from the wet phosphoric acid unit, a high-temperature and high-humidity environment pile is constructed to fully utilize the heat.

[0039] (3) The high temperature and high humidity reaction environment greatly accelerates the curing reaction process and improves the curing reaction efficiency. In a short period of time (storage ≤ 3 days), the phosphogypsum meets the harmlessness index requirements.

[0040] (4) The harmless disposal process of phosphogypsum is simplified, with low energy consumption and harmless disposal cost, and it is capable of large-scale harmless disposal of phosphogypsum.

[0041] For the sake of clarity, the following examples and comparative examples are used to explain the present invention in detail. In the following examples and comparative examples of the present invention, unless otherwise specified, all percentages involved are by mass percentage.

[0042] Example 1

[0043] The chemical composition content of the semi-hydrated phosphogypsum produced as a by-product of the semi-hydrated wet phosphoric acid process is shown in Table 1. A calcium alkaline agent (quicklime) is added to the freshly discharged semi-hydrated phosphogypsum, and the added mass percentage composition is: 97.0% of semi-hydrated phosphogypsum and 3.0% of calcium alkaline agent. The materials are stirred and mixed evenly, and water is added until the water content of the phosphogypsum is about 30.0%. The pH value of the semi-hydrated phosphogypsum is adjusted to 10.40. The mixed materials are matured and stored in the temporary storage room of the phosphogypsum. The materials are piled up and shaped into a pile body by a forklift. The pile is similar to a cone, and the pile body diameter: height = 3.5:1. The pile body material is about 1100t. After 12h of storage, the internal temperature of the pile body is measured to be about 88.0℃, the free water content of the phosphogypsum is 18.20%, and the crystal water content is 18.74%. The phosphogypsum stored for 3d is recovered and crushed to prepare harmless phosphogypsum-1. The leachate of harmless phosphogypsum is obtained according to the method specified in HJ 557. The indicators of the leachate of harmless phosphogypsum meet the Class I indicators of GB18599-2020 General Industrial Solid Waste Storage and Landfill Pollutant Control Standards. The indicators of the leachate of harmless phosphogypsum are shown in Table 2.

[0044] Table 1 Content of some chemical components of semi-hydrated phosphogypsum produced as a by-product of semi-hydrated wet phosphoric acid process

[0045] <![CDATA[Total P2O5 / %]]> <![CDATA[Water-soluble P2O5 / %]]> Total F / % Water soluble F / % Eutectic phosphorus / % Free water / % Crystal water / % pH Discharge temperature / ℃ 1.27 0.59 0.83 0.40 0.42 22.16 6.80 3.10 61.0

[0046] Table 2 Characteristic pollution element indicators of harmless phosphogypsum leachate

[0047] Sample No. Phosphate (P) mg / L Fluoride (F) mg / L pH Hemihydrate gypsum 259.9 208.3 3.19 Harmless gypsum-1 0.03 6.47 7.83 GB18599-2020 Class I limit values ​​for solid waste ≤0.50 ≤10.0 6-9

[0048] Note: All other indicators meet the requirements of GB18599-2020 Solid Waste Class I Standard.

[0049] Example 2

[0050] On the basis of Example 1, the amount of water added was changed to add water until the water content of phosphogypsum was about 27.0%. After 12 hours of storage, the internal temperature of the pile was measured to be about 89.0°C, the free water content of phosphogypsum was 15.38%, and the crystallization water content was 18.15%. The phosphogypsum stored for 3 days was recovered and crushed to prepare harmless phosphogypsum-2. The harmless phosphogypsum was used to obtain a leachate according to the method specified in HJ 557. The index of the harmless phosphogypsum leachate met the Class I index of GB18599-2020 General Industrial Solid Waste Storage and Landfill Pollutant Control Standard, and the index of the harmless phosphogypsum leachate is shown in Table 3.

[0051] Table 3 Characteristic pollution element indicators of harmless phosphogypsum leachate

[0052] Sample No. Phosphate (P) mg / L Fluoride (F) mg / L pH Hemihydrate gypsum 259.9 208.3 3.19 Harmless gypsum-2 0.02 7.14 8.02 GB18599-2020 Class I limit values ​​for solid waste ≤0.50 ≤10.0 6-9

[0053] Note: All other indicators meet the requirements of GB18599-2020 Solid Waste Class I Standard.

[0054] Example 3

[0055] On the basis of Example 1, the pile is similar to a cone, the pile diameter is changed to 3.0:1, the pile material is about 1100t, the other conditions remain unchanged, and the internal temperature of the pile is measured to be about 85.0°C after 12h of storage, the free water content of phosphogypsum is 18.68%, and the crystal water content is 18.53%. The phosphogypsum stored for 3d is recovered and crushed to prepare harmless phosphogypsum-3. The harmless phosphogypsum is obtained by the method specified in HJ 557 to obtain a leachate, and the index of the harmless phosphogypsum leachate meets the Class I index of GB18599-2020 General Industrial Solid Waste Storage and Landfill Pollutant Control Standard, and the index of the harmless phosphogypsum leachate is shown in Table 4.

[0056] Table 4 Characteristic pollution element indicators of harmless phosphogypsum leachate

[0057]

[0058]

[0059] Note: All other indicators meet the requirements of GB18599-2020 Solid Waste Class I Standard.

[0060] Example 4

[0061] The chemical composition content of the semi-hydrated phosphogypsum produced as a by-product of the semi-hydrated wet phosphoric acid process is shown in Table 5. A calcium alkaline agent (quicklime) is added to the semi-hydrated phosphogypsum just discharged, and the added mass percentage composition is: 98.5% of semi-hydrated phosphogypsum and 1.5% of calcium alkaline agent. The materials are stirred and mixed evenly, and water is added until the water content of the phosphogypsum is about 30.0%. The pH value of the semi-hydrated phosphogypsum is adjusted to 10.70. The mixed materials are matured and stored in the temporary storage warehouse of phosphogypsum. The materials are piled up and shaped into a pile body by a forklift. The pile is similar to a cone, and the pile body diameter: height = 3.5:1. The pile body material is about 1100t. After 12h of storage, the internal temperature of the pile body is measured to be about 86.0℃, the free water content of the phosphogypsum is 18.93%, and the crystal water content is 19.55%. The phosphogypsum stored for 3d is recovered and crushed to prepare harmless phosphogypsum-4. The leachate of harmless phosphogypsum is obtained according to the method specified in HJ 557. The indicators of the leachate of harmless phosphogypsum meet the Class I indicators of GB18599-2020 General Industrial Solid Waste Storage and Landfill Pollutant Control Standards. The indicators of the leachate of harmless phosphogypsum are shown in Table 6.

[0062] Table 5 Content of some chemical components of semi-hydrated phosphogypsum produced as a by-product of semi-hydrated wet phosphoric acid process

[0063] <![CDATA[Total P2O5 / %]]> <![CDATA[Water-soluble P2O5 / %]]> Total F / % Water soluble F / % Eutectic phosphorus / % Free water / % Crystal water / % pH Discharge temperature / ℃ 0.83 0.36 0.43 0.16 0.30 20.91 6.64 4.06 63

[0064] Table 6 Characteristic pollution element indicators of harmless phosphogypsum leachate

[0065] Sample No. Phosphate (P) mg / L Fluoride (F) mg / L pH Hemihydrate gypsum 140.7 92.6 4.16 Harmless gypsum-4 0.03 5.39 7.82 GB18599-2020 Class I limit values ​​for solid waste ≤0.50 ≤10.0 6-9

[0066] Note: All other indicators meet the requirements of GB18599-2020 Solid Waste Class I Standard.

[0067] Comparative Example 1

[0068] On the basis of Example 4, the water content was adjusted, and no water was added after mixing. The water content of the material was 19.12%. After 12 hours of storage, the internal temperature of the pile was measured to be about 87.0°C, the free water content of phosphogypsum was 11.46%, and the crystallization water content was 16.80%. The phosphogypsum stored for 3 days was recovered and crushed to prepare harmless phosphogypsum-5. The harmless phosphogypsum was used to obtain a leachate according to the method specified in HJ557. The index of the harmless phosphogypsum leachate cannot meet the Class I index of GB18599-2020 General Industrial Solid Waste Storage and Landfill Pollutant Control Standard. The index of the harmless phosphogypsum leachate is shown in Table 7.

[0069] Table 7 Characteristic pollution element indicators of harmless phosphogypsum leachate

[0070]

[0071]

[0072] Note: All other indicators meet the requirements of GB18599-2020 Solid Waste Class I Standard.

[0073] Comparative Example 2

[0074] On the basis of Example 4, the water content was adjusted, and the water was added after mixing. The water content of the material was 36.00%. Due to the high water content of the material, the phosphogypsum was in a paste state and could not be piled and shaped, which affected the storage of materials in the temporary storage plant and failed to construct a high temperature and high humidity reaction environment. The material was measured for 12 hours to obtain a temperature of about 45.0°C, a free water content of phosphogypsum of 26.80%, and a crystal water content of 18.51%. The phosphogypsum stored for 3 days was recovered and crushed to prepare harmless phosphogypsum-6. The harmless phosphogypsum was used to obtain a leachate according to the method specified in HJ 557. The index of the harmless phosphogypsum leachate could not meet the Class I index of GB18599-2020 General Industrial Solid Waste Storage and Landfill Pollutant Control Standard, and the index of the harmless phosphogypsum leachate was shown in Table 8.

[0075] Table 8 Characteristic pollution element indicators of harmless phosphogypsum leachate

[0076] Sample No. Phosphate (P) mg / L Fluoride (F) mg / L pH Hemihydrate gypsum 140.7 92.6 4.16 Harmless gypsum-6 0.12 14.03 10.16 GB18599-2020 Class I limit values ​​for solid waste ≤0.50 ≤10.0 6-9

[0077] Note: All other indicators meet the requirements of GB18599-2020 Solid Waste Class I Standard.

[0078] Comparative Example 3

[0079] Based on Example 4, the phosphogypsum material was not stored, but was dispersed in the warehouse, and a high temperature and high humidity reaction environment could not be constructed. The material was measured for 12 hours and the temperature was about 31.0°C, the free water content of the phosphogypsum was 14.72%, and the crystallization water content was 16.35%. The phosphogypsum stored for 3 days was mined and crushed to prepare harmless phosphogypsum-7. The harmless phosphogypsum was used to obtain a leachate according to the method specified in HJ557. The index of the harmless phosphogypsum leachate could not meet the Class I index of GB18599-2020 General Industrial Solid Waste Storage and Landfill Pollutant Control Standard. The index of the harmless phosphogypsum leachate is shown in Table 9.

[0080] Table 9 Characteristic pollution element indicators of harmless phosphogypsum leachate

[0081] Sample No. Phosphate (P) mg / L Fluoride (F) mg / L pH Hemihydrate gypsum 140.7 92.6 4.16 Harmless gypsum-7 10.38 18.74 0.61 GB18599-2020 Class I limit values ​​for solid waste ≤0.50 ≤10.0 6-9

[0082] Note: All other indicators meet the requirements of GB18599-2020 Solid Waste Class I Standard.

[0083] In summary, the technical solution provided by the present invention solidifies phosphorus and fluorine by utilizing the hydration reaction of the phosphogypsum pile-hydration heat to construct a high temperature and high humidity reaction environment, which greatly accelerates the process of the curing reaction and improves the curing effect.

[0084] In a short period of time (disposal time ≤ 3 days), the phosphorus element (in terms of P) leached from harmless phosphogypsum is less than 0.5 mg / L, fluoride is less than 10 mg / L, and pH is 6-9, meeting the requirements of Class I general industrial solid waste indicators in GB18599-2020 General Industrial Solid Waste Storage and Landfill Pollutant Control Standards.

[0085] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A harmless treatment process for hemihydrate phosphogypsum, characterized in that: The following steps are involved: a) adjusting the pH value and moisture content of the semi-hydrated phosphogypsum raw material to obtain adjusted semi-hydrated phosphogypsum; In step a), the reagent used to adjust the pH value is a calcium alkaline agent; after the adjustment, the pH value of the hemihydrate phosphogypsum is 10-11, and the water content is 25-30wt%; b) piling the adjusted hemihydrate phosphogypsum to form a conical or quasi-conical pile, and after piling for a period of time, obtaining harmless phosphogypsum.

2. The harmless treatment process according to claim 1, characterized in that: In step a), the calcic alkaline agent is quicklime.

3. The harmless treatment process according to claim 1, characterized in that: In step a), the amount of the calcium alkaline agent used accounts for 1-3% of the total mass of the hemihydrate phosphogypsum raw material and the calcium alkaline agent.

4. The harmless treatment process according to claim 1, characterized in that: In step b), the weight of the pile is 800-1200t.

5. The harmless treatment process according to claim 1, characterized in that: In step b), the ratio of the diameter to the height of the pile is (3-3.5):

1.

6. The harmless treatment process according to claim 1, characterized in that: In step b), the temperature of the pile during the storage process is 75-90°C.

7. The harmless treatment process according to claim 1, characterized in that: In step b), the stacking time is ≤ 3 days.

8. The harmless treatment process according to claim 1, characterized in that: In step a), the free water content of the semi-hydrated phosphogypsum raw material is 15-25wt%, the crystal water content is 6-7.5wt%, the pH value is 2.5-4.5, and the temperature is 50-70°C.

9. The harmless treatment process according to claim 1, characterized in that: The following steps are also included: The harmless phosphogypsum obtained in step b) is crushed.

10. Use of the harmless phosphogypsum obtained by the harmless treatment process according to any one of claims 1 to 9 in ecological restoration or mine filling.

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