Harmless preparation method of phosphogypsum

Abstract

The invention discloses a harmless preparation method of ardealite, and relates to the technical field of ardealite preparation, according to the harmless preparation method of ardealite, through scientific proportioning of ardealite, high-calcium silicon-aluminum fly ash and a curing agent, harmful substances such as free phosphorus, fluorine and the like in ardealite are effectively removed by utilizing acid-base neutralization reaction and hydration reaction; the total phosphorus content in the finally formed consolidated body leachate is less than or equal to 0.5 mg / L, and the fluoride content is less than or equal to 1.0 mg / L, so that the purpose of harmless treatment is achieved, and the risk of environmental pollution is reduced; the prepared consolidated body is mainly composed of crystallized gypsum, the compressive strength is greater than or equal to 5MPa, and the consolidated body has good mechanical properties; in the crystal structure, the dihydrate gypsum acicular crystal, the ettringite fibrous crystal and the hydroxyapatite amorphous phase interact, so that the stability and durability of the material are ensured, and various engineering application requirements can be met; the prepared consolidated body can be used as a mine filling material, a road base material, an ecological restoration base material and the like, resource utilization of the ardealite is realized, and the application field of the ardealite is expanded.

Description

Technical Field

[0001] The present invention relates to the technical field of phosphogypsum preparation, and in particular to a harmless preparation method of phosphogypsum. Background Art

[0002] The existing harmless preparation method of phosphogypsum still has the following drawbacks in actual use:

[0003] In the harmless preparation of phosphogypsum mine filling materials and road construction materials, the method of adding phosphogypsum paste to cement and curing agent is currently commonly used for processing and production; however, the cost of the cement and curing agent required is relatively high, and their economic benefits cannot compete with traditional earthwork and concrete when used in mine repair backfill and pouring of water-stabilized concrete, which is not conducive to the marketization of phosphogypsum products. Summary of the Invention

[0004] The purpose of the present invention is to provide a harmless preparation method for phosphogypsum to solve the problem that the cost of cement and curing agent is high, the economic benefits of using it in mine repair backfill and pouring water stabilization cannot compete with traditional earthwork and concrete, and it is not conducive to the marketization of phosphogypsum products.

[0005] In order to achieve the above object, the present invention provides the following technical solution: a method for harmless preparation of phosphogypsum, comprising the following steps:

[0006] S1. By mass percentage, 89% phosphogypsum, 10% high-calcium silicon-aluminum fly ash and 1% curing agent are mixed to form a mixed material;

[0007] S2. The mixture was stirred in a blender at a speed of 200-300r / min for 10-15 minutes until the material was uniform;

[0008] S3. Reaction curing: Spread the stirred material on a mold and press it heavily or roll it on the construction site. Allow it to react at room temperature (20-30°C) for 7-14 days to allow the free phosphorus and fluorine in the phosphogypsum to react with the high-calcium silicon-aluminum fly ash and curing agent to undergo acid-base neutralization and hydration reactions.

[0009] S4. Hardening and molding: After the reaction is completed, the material gradually hardens to form a solid body mainly composed of crystalline gypsum, with a compressive strength of ≥5MPa, and the total phosphorus content in the leachate is ≤0.5mg / L and the fluoride content is ≤1.0mg / L.

[0010] Furthermore, the chemical composition of the high calcium silicon aluminum fly ash is CaO ≥ 25 wt%, SiO2 ≥ 40 wt%, Al2O3 ≥ 15 wt%, and the specific surface area is ≥ 400 m 2 / kg;

[0011] The curing agent is a fluorosilicic acid curing agent, and the fluorosilicic acid curing agent chemically reacts with some components of the phosphogypsum.

[0012] Furthermore, the acid-base neutralization reaction in step S3 includes:

[0013] The free phosphoric acid H3PO4 in phosphogypsum reacts with CaO in high calcium fly ash to form hydroxyapatite: 10CaO+6H3PO4→Ca 10 (PO4)6(OH)2+18H2O

[0014] Fluoride CaF2 reacts with sodium silicate to form fluorosilicate precipitate:

[0015] C a F2+Na2SiO3→CaSiO3+2NaF↓.

[0016] Furthermore, the crystal structure of the solidified body in step S4 includes:

[0017] Dihydrate gypsum (CaSO4·2H2O) needle-shaped crystals, accounting for 60-70%;

[0018] ettringite (3CaO·AL2O3·3CaSO4·32H2O) fibrous crystals, accounting for 20-30%;

[0019] Hydroxyapatite (Ca 10 (PO4)6(OH)2) amorphous phase, accounting for 5-10%.

[0020] Furthermore, the consolidated body is suitable for the following application scenarios:

[0021] Mine filling material: directly backfill into the goaf, replacing traditional cement-based materials;

[0022] Road base material: replace traditional cement-stabilized soil and gravel, spread and compact in layers, with each layer being 30-40cm thick;

[0023] Ecological restoration substrate: used for acidic soil improvement, adjusting pH to 6.5-8.0.

[0024] Furthermore, the economic cost is 30-40% of the traditional cement solidification method, and can be commercialized without the need for additional subsidies.

[0025] Compared with the prior art, the harmless preparation method of phosphogypsum provided by the present invention has the following beneficial effects:

[0026] The harmless preparation method of phosphogypsum effectively removes harmful substances such as free phosphorus and fluorine in the phosphogypsum by scientifically proportioning phosphogypsum, high-calcium silicon-aluminum fly ash and a curing agent, and utilizes acid-base neutralization reaction and hydration reaction, so that the total phosphorus content in the leachate of the final solidified body is ≤0.5 mg / L and the fluoride content is ≤1.0 mg / L, thereby achieving the purpose of harmless treatment and reducing the risk of environmental pollution. The prepared solidified body is mainly composed of crystalline gypsum, has a compressive strength of ≥5 MPa, and has good mechanical properties; the dihydrate gypsum needle crystals, ettringite fibrous crystals and hydroxyapatite free crystals in its crystal structure are The interaction between the shaped phases ensures the stability and durability of the material, which can meet the needs of various engineering applications; the prepared solid body can be used as mine filling material, road base material, ecological restoration substrate, etc., realizing the resource utilization of phosphogypsum, expanding its application field, reducing the mining of natural sand and gravel and other resources, and promoting the development of a circular economy; the economic cost of this method is only 30-40% of the traditional cement solidification method, and it can be commercialized without the need for additional government subsidies, which greatly reduces production costs and improves the market competitiveness of products. It has significant economic benefits and broad market prospects. DETAILED DESCRIPTION

[0027] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below.

[0028] A method for harmlessly preparing phosphogypsum comprises the following steps:

[0029] S1. By mass percentage, 89% phosphogypsum, 10% high-calcium silicon-aluminum fly ash and 1% curing agent are mixed to form a mixed material;

[0030] S2. The mixture was stirred in a blender at a speed of 200-300r / min for 10-15 minutes until the material was uniform;

[0031] S3. Reaction curing: Spread the stirred material on a mold and press it heavily or roll it on the construction site. Allow it to react at room temperature (20-30°C) for 7-14 days to allow the free phosphorus and fluorine in the phosphogypsum to react with the high-calcium silicon-aluminum fly ash and curing agent to undergo acid-base neutralization and hydration reactions.

[0032] S4. Hardening and molding: After the reaction is completed, the material gradually hardens to form a solid body mainly composed of crystalline gypsum, with a compressive strength of ≥5MPa, and the total phosphorus content in the leachate is ≤0.5mg / L and the fluoride content is ≤1.0mg / L.

[0033] The chemical composition of high calcium silicon aluminum fly ash is CaO ≥ 25wt%, SiO2 ≥ 40wt%, Al2O3 ≥ 15wt%, and the specific surface area is ≥ 400m 2 / kg;

[0034] The curing agent is a fluorosilicic acid curing agent, and the fluorosilicic acid curing agent chemically reacts with some components of the phosphogypsum.

[0035] The acid-base neutralization reaction in step S3 includes:

[0036] The free phosphoric acid H3PO4 in phosphogypsum reacts with CaO in high calcium fly ash to form hydroxyapatite: 10CaO+6H3PO4→Ca 10 (PO4)6(OH)2+18H2O

[0037] Fluoride CaF2 reacts with sodium silicate to form fluorosilicate precipitate:

[0038] C a F2+Na2SiO3→CaSiO3+2NaF↓.

[0039] The crystal structure of the solidified body in step S4 includes:

[0040] Dihydrate gypsum (CaSO4·2H2O) needle-shaped crystals, accounting for 60-70%;

[0041] ettringite (3CaO·AL2O3·3CaSO4·32H2O) fibrous crystals, accounting for 20-30%;

[0042] Hydroxyapatite (Ca 10 (PO4)6(OH)2) amorphous phase, accounting for 5-10%.

[0043] Consolidation bodies are suitable for the following application scenarios:

[0044] Mine filling material: directly backfill into the goaf, replacing traditional cement-based materials;

[0045] Road base material: replace traditional cement-stabilized soil and gravel, spread and compact in layers, with each layer being 30-40cm thick;

[0046] Ecological restoration substrate: used for acidic soil improvement, adjusting pH to 6.5-8.0.

[0047] The economic cost is 30-40% of the traditional cement solidification method, and it can be commercialized without additional subsidies.

[0048] The above description is merely illustrative of certain exemplary embodiments of the present invention. It is understood that those skilled in the art will be able to modify the described embodiments in various ways without departing from the spirit and scope of the present invention. Therefore, the above description is illustrative in nature and should not be construed as limiting the scope of the claims.

Claims

1. A method for harmless preparation of phosphogypsum, characterized in that: The following steps are involved: S1. By mass percentage, 89% phosphogypsum, 10% high-calcium silicon-aluminum fly ash and 1% curing agent are mixed to form a mixed material; S2. The mixture was stirred in a blender at a speed of 200-300r / min for 10-15 minutes until the material was uniform; S3. Reaction curing: Spread the stirred material on a mold and press it heavily or roll it on the construction site. Allow it to react at room temperature (20-30°C) for 7-14 days to allow the free phosphorus and fluorine in the phosphogypsum to react with the high-calcium silicon-aluminum fly ash and curing agent to undergo acid-base neutralization and hydration reactions. S4. Hardening and molding: After the reaction is completed, the material gradually hardens to form a solid body mainly composed of crystalline gypsum, with a compressive strength of ≥5MPa, and the total phosphorus content in the leachate is ≤0.5mg / L and the fluoride content is ≤1.0mg / L.

2. The method for harmless preparation of phosphogypsum according to claim 1, characterized in that: The chemical composition of the high calcium silicon aluminum fly ash is CaO ≥ 25 wt%, SiO2 ≥ 40 wt%, Al2O3 ≥ 15 wt%, and the specific surface area is ≥ 400 m 2 / kg; The curing agent is a fluorosilicic acid curing agent, and the fluorosilicic acid curing agent chemically reacts with some components of the phosphogypsum.

3. The method for harmless preparation of phosphogypsum according to claim 1, characterized in that: The acid-base neutralization reaction in step S3 includes: The free phosphoric acid H3PO4 in phosphogypsum reacts with CaO in high calcium fly ash to form hydroxyapatite: 10CaO+6H3PO4→Ca 10 (PO4)6(OH)2+18H2O Fluoride CaF2 reacts with sodium silicate to form fluorosilicate precipitate: C a F2+Na2SiO3→CaSiO3+2NaF↓。 4. The method for harmless preparation of phosphogypsum according to claim 1, characterized in that: The crystal structure of the solidified body in step S4 includes: Dihydrate gypsum (CaSO4·2H2O) needle-shaped crystals, accounting for 60-70%; ettringite (3CaO·AL2O3·3CaSO4·32H2O) fibrous crystals, accounting for 20-30%; Hydroxyapatite (Ca 10 (PO4)6(OH)2) amorphous phase, accounting for 5-10%.

5. The method for harmless preparation of phosphogypsum according to claim 1, characterized in that: The consolidation body is suitable for the following application scenarios: Mine filling material: directly backfill into the goaf, replacing traditional cement-based materials; Road base material: replace traditional cement-stabilized soil and gravel, spread and compact in layers, with each layer being 30-40cm thick; Ecological restoration substrate: used for acidic soil improvement, adjusting pH to 6.5-8.

0.

6. The method for harmless preparation of phosphogypsum according to claim 1, characterized in that: The economic cost is 30-40% of the traditional cement solidification method, and can be commercialized without additional subsidies.