An industrial solid waste phosphogypsum composite material, its preparation method and application

Abstract

The present invention belongs to the technical field of building materials, and specifically relates to an industrial solid waste phosphogypsum composite material, its preparation method and application. The preparation method of the industrial solid waste phosphogypsum composite material is as follows: Mix industrial solid waste phosphogypsum, cement, microsilica powder, coal cinder, phenolic resin and water, and obtain a precursor through granulation and drying; Heat the precursor at 120°C to 140°C for 1h to 1.5h to obtain the industrial solid waste phosphogypsum composite material. The present invention realizes the transformation of industrial solid waste phosphogypsum into hemihydrate gypsum powder at a relatively low calcination temperature. The industrial solid waste phosphogypsum composite material obtained by the method of the present invention has high hardness, high strength and good durability. While overcoming the non-environmental protection technical defects existing in phosphogypsum, the industrial solid waste phosphogypsum composite material is applied to the road base.

Description

Technical Field

[0001] The present invention belongs to the technical field of building materials, and particularly relates to an industrial solid waste phosphogypsum composite material, a preparation method thereof, and an application thereof. Background Art

[0002] Phosphogypsum is a waste generated during the production of phosphoric acid in the phosphate fertilizer industry. Approximately 5 tons of waste residue are discharged for every 1 ton of phosphoric acid produced. Due to the rapid development of the phosphorus chemical industry, the output of phosphogypsum waste has also increased rapidly. The main chemical component of phosphogypsum is CaSO4·2H2O, which is similar to natural gypsum. However, since phosphogypsum contains soluble phosphorus, fluorine, free acid, and other impurities, random discharge will cause serious environmental pollution. Therefore, the waste residue is stacked for treatment, which not only occupies land, but also the long-term storage of phosphogypsum will have an impact on the ecological environment.

[0003] When applying phosphogypsum to building materials in the prior art, it is necessary to pretreat the phosphogypsum to remove impurities and reduce the environmental pollution caused by phosphogypsum. The traditional pretreatment processes of phosphogypsum include: water washing method, calcination method, and neutralization method. The water washing method removes soluble impurities in phosphogypsum through water washing, such as soluble phosphates, fluorine, and free phosphoric acid. However, the ability of water washing to remove impurities is limited, so it is necessary to wash repeatedly for many times, resulting in waste of water resources; at the same time, a large amount of water needs to be evaporated after water washing, and the treatment cost is high; in addition, the wastewater generated by water washing is likely to cause water resource pollution problems, so it is difficult to be widely applied on a large scale. The neutralization method uses lime to neutralize and treat phosphogypsum, which requires a large amount of lime. Generally, 10wt% of lime is required to effectively reduce the soluble phosphorus content, and the price of lime is expensive, so the neutralization method seriously reduces the economic benefits of enterprises.

[0004] The calcination process can transform phosphogypsum into hemihydrate gypsum powder, which has less environmental pollution during use and does not affect the setting time and strength of cement. However, the calcination requires a temperature of 150°C to 180°C and lasts for 1h to 2h, with high process energy consumption and limited output.

[0005] Currently, the materials used for highway pavement bases mainly come from crushed stones, gravel, and slag. The excessive exploitation and extraction of these materials have had a greater impact on the environment. Therefore, developing a new highway base material that meets environmental protection requirements and has a certain strength is the problem we need to solve.

[0006] However, due to the technical defects that phosphogypsum cannot be directly used and has a large treatment difficulty, the prior art cannot directly apply phosphogypsum to prepare highway base materials. Summary of the Invention

[0007] Aiming at the deficiencies of the above-mentioned existing technologies, the present invention provides an industrial solid waste phosphogypsum composite material, its preparation method and application. The present invention uses industrial solid waste phosphogypsum as a raw material, mixes it with cement, microsilica powder, coal cinder, phenolic resin and water, then granulates it, and then calcines it at 120°C to 140°C for 1h to 1.5h to obtain an industrial solid waste phosphogypsum composite material. Compared with the existing calcination process, the present invention can transform industrial solid waste phosphogypsum into hemihydrate gypsum powder at a lower calcination temperature and a shorter calcination time. Moreover, the industrial solid waste phosphogypsum composite material obtained by the method of the present invention has high hardness, high strength and good durability. While solving the environmental impact caused by the existing highway pavement base materials and the technical defect of non-environmental protection of phosphogypsum, the obtained industrial solid waste phosphogypsum composite material is applied to the highway base.

[0008] To solve the above technical problems, the present invention adopts the following technical solutions:

[0009] A preparation method of an industrial solid waste phosphogypsum composite material, comprising the following steps:

[0010] Mix industrial solid waste phosphogypsum, cement, microsilica powder, coal cinder, phenolic resin and water, granulate and dry to obtain a precursor; use industrial solid waste phosphogypsum as the main raw material, and use cement, microsilica powder, coal cinder and phenolic resin as modifiers to modify industrial solid waste phosphogypsum; cement and microsilica powder are gelling agents, coal cinder reduces the energy consumption of converting industrial solid waste phosphogypsum into hemihydrate gypsum powder, and phenolic resin improves the comprehensive performance of the industrial solid waste phosphogypsum composite material and overcomes the influence of the pores generated after the combustion of coal cinder on the mechanical properties of the industrial solid waste phosphogypsum composite material; then when realizing the application of converting industrial solid waste phosphogypsum into hemihydrate gypsum powder CaSO4·0.5H2O, an industrial solid waste phosphogypsum composite material with high hardness, high strength and good durability is obtained.

[0011] Heat the precursor at 120°C to 140°C for 1h to 1.5h to obtain an industrial solid waste phosphogypsum composite material. The calcination temperature for converting industrial solid waste phosphogypsum into hemihydrate gypsum powder in the existing technology is 150°C to 180°C. Since the present invention uses a combination of coal cinder and industrial solid waste phosphogypsum, the conversion of industrial solid waste phosphogypsum is achieved while reducing the calcination temperature; when the temperature is higher than 140°C, CaSO4·2H2O will be converted into anhydrous CaSO4, and when the temperature is lower than 120°C, the calcination will be incomplete, causing environmental pollution.

[0012] Preferably, the mass ratio of industrial solid waste phosphogypsum, cement, microsilica powder, phenolic resin and coal cinder is 100:20 - 40:3 - 6:5 - 10:4 - 8, and the amount of phenolic resin is higher than that of coal cinder to improve the mechanical properties of the industrial solid waste phosphogypsum composite material by using phenolic resin.

[0013] Preferably, both the particle sizes of the cinder and the phenolic resin are in the micron range. The cinder and phenolic resin with micron-sized particle sizes not only play a role in filling the voids of the cement, but also produce a porous structure after the cinder burns, facilitating the overflow of gas and enhancing the conversion efficiency of industrial solid waste phosphogypsum. Further, the particle size of the phenolic resin is less than 50 μm, and the particle size of the cinder is 50 μm to 100 μm. The microsilica, phenolic resin, and cinder form a particle size gradient, thereby achieving dense filling in the cement and enhancing the strength of the industrial solid waste phosphogypsum composite material.

[0014] Preferably, the industrial solid waste phosphogypsum is the waste generated during the production of phosphoric acid in the phosphate fertilizer industry, and its main chemical component is CaSO4·2H2O. The mass percentage of CaSO4·2H2O in the industrial solid waste phosphogypsum is 80% to 98%. The present invention processes highly pure CaSO4·2H2O and can achieve efficient conversion of CaSO4·2H2O.

[0015] Preferably, the microsilica is selected from Elkem 940 microsilica, and its average particle size is 0.1 μm to 0.15 μm. The microsilica not only plays a role in filling the voids of the cement, but also participates in the hydration of the cement. Therefore, when the particle size is smaller, the mixture of the cement and the microsilica is more uniform and forms a dense structure, enhancing the strength of the industrial solid waste phosphogypsum composite material after the cement hydrates.

[0016] The present invention also protects the industrial solid waste phosphogypsum composite material prepared by the above preparation method.

[0017] Preferably, the particle size of the industrial solid waste phosphogypsum composite material is 5 mm to 20 mm. When it is less than 5 mm, the particle size is too small and not convenient for application as a highway base material; when it is greater than 20 mm, slippage is likely to occur between the particles.

[0018] The present invention also protects the application of the above industrial solid waste phosphogypsum composite material in the preparation of highway base materials.

[0019] Preferably, the application method is: using the industrial solid waste phosphogypsum composite material as a filler to obtain a highway base material.

[0020] Preferably, the application method is: using the industrial solid waste phosphogypsum composite material as an aggregate, mixing it with concrete raw materials and curing to obtain a highway base material; the concrete raw materials include a water reducing agent, water, and also include additives, and the additives include but are not limited to fly ash, silica fume, mineral powder, and kaolin.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0022] 1. The present invention uses industrial solid waste phosphogypsum, cement, microsilica fume, coal cinder, phenolic resin and water as raw materials. Through mixing and granulation in sequence, a precursor is obtained, and then it is heated at 120°C to 140°C for 1h to 1.5h to obtain an industrial solid waste phosphogypsum composite material. In the precursor, industrial solid waste phosphogypsum is used as the main raw material, and cement, microsilica fume, coal cinder and phenolic resin are used as modifiers. After the coal cinder is compounded with the industrial solid waste phosphogypsum, the coal cinder provides combustion sites during calcination, and then rapid temperature rise is carried out to quickly convert the industrial solid waste phosphogypsum into hemihydrate gypsum powder. However, pores will be formed with the release of gas during the combustion of the coal cinder, and the pores affect the mechanical properties of the industrial solid waste phosphogypsum composite material. Based on this, phenolic resin is also compounded. The phenolic resin will undergo crosslinking and curing reaction at high temperature, polymerization occurs during the curing process, chemical bonds are formed between phenolic resin molecules, and then a three-dimensional network structure is formed. The formed three-dimensional network structure effectively overcomes the problem of strength weakening caused by pores.

[0023] In addition, the present invention also uses cement and microsilica fume to be compounded with industrial solid waste phosphogypsum to realize the application of the industrial solid waste phosphogypsum composite material in the road base. During the granulation and drying process, the cement undergoes a hydration reaction. At this time, the microsilica fume can participate in the hydration reaction of the cement to form a denser cement matrix, thereby improving the compressive strength and flexural strength of the industrial solid waste phosphogypsum composite material. In addition, due to the fine particles of the microsilica fume that can fill the gaps between cement particles, the capillary pores of the industrial solid waste phosphogypsum composite material are reduced, enhancing the overall strength.

[0024] In summary, the present invention uses industrial solid waste phosphogypsum, cement, microsilica fume, coal cinder, phenolic resin and water as raw materials, realizes the conversion of industrial solid waste phosphogypsum at a relatively low temperature, and at the same time considers from the selection of raw materials and combines the reactions occurring at high temperature to obtain an industrial solid waste phosphogypsum composite material with high hardness, high strength and good durability, and applies it as a road base material.

[0025] The industrial solid waste phosphogypsum composite material obtained by the preparation method of the present invention can directly replace the existing crushed stones, sand and gravels and slag, and be used as a road surface base material, overcoming the problem of environmental impact caused by over-exploitation and extraction of crushed stones, sand and gravels and slag; in addition, in the industrial solid waste phosphogypsum composite material, the industrial solid waste phosphogypsum is converted into hemihydrate gypsum powder CaSO4·0.5H2O, and the hemihydrate gypsum powder has little environmental pollution during use, overcoming the problem of environmental unfriendliness in the use of phosphogypsum.

[0026] 2. The present invention calcines at 120°C to 140°C to convert phosphogypsum into hemihydrate gypsum powder. The dried hemihydrate gypsum powder has strong hardening properties and good compressive strength. After calcination, the compounding of cement and hemihydrate gypsum powder is achieved. The hemihydrate gypsum powder can improve the strength and durability of cement, thereby enhancing the mechanical properties of the industrial solid waste phosphogypsum composite material. At the same time, the secondary application of the industrial waste phosphogypsum is realized.

[0027] 3. The present invention calcines at 120°C to 140°C. At this time, the cement may undergo certain physical and chemical changes, but the main components of the cement are calcium silicate and calcium aluminate, which remain stable at the calcination temperature of 120°C to 140°C. Such physical and chemical changes generally do not cause significant changes in the main chemical structure of the cement, and no major chemical reactions or structural changes occur, ensuring the structural stability of the industrial solid waste phosphogypsum composite material.

[0028] 4. In the present invention, microsilica powder and coal cinder are often regarded as industrial wastes. Therefore, while realizing the treatment of industrial solid waste phosphogypsum, the secondary utilization of industrial wastes is achieved, and the industrial solid waste phosphogypsum is transformed into a new material that can be used as a highway base material. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a scanning electron microscope image of the industrial solid waste phosphogypsum composite material obtained in Example 1 of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0030] The following is a detailed description of the specific embodiments of the present invention. However, it should be understood that the protection scope of the present invention is not limited by the specific embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the protection scope of the present invention. The experimental methods described in the embodiments of the present invention are all conventional methods unless otherwise specified.

[0031] Compared with the prior art, in the prior art, the calcination temperature of industrial solid waste phosphogypsum is 150°C to 180°C, and the calcination time is 1h to 2h. The calcination process has high energy consumption, resulting in limited output. In the present invention, through the compounding of coal cinder and industrial solid waste phosphogypsum, the calcination temperature is reduced to 120°C to 140°C, and the calcination time is reduced to 1h to 1.5h, that is, the preparation of hemihydrate gypsum powder is achieved while reducing energy consumption.

[0032] The following uses examples to further study the technical solutions of the present invention. The specific research methods and results are as follows:

[0033] Example 1

[0034] A preparation method of an industrial solid waste phosphogypsum composite material includes the following steps:

[0035] Mix industrial solid waste phosphogypsum, cement, microsilica fume, coal cinder, phenolic resin and water, granulate, and then dry at room temperature to obtain a precursor.

[0036] Among them, the particle size of the phenolic resin is 40 μm, the particle size of the coal cinder is 70 μm, and the mass ratio of industrial solid waste phosphogypsum, cement, microsilica fume, phenolic resin and coal cinder is 100:30:5:8:6.

[0037] Heat the precursor at 140 °C for 1 h to obtain an industrial solid waste phosphogypsum composite material.

[0038] Example 2

[0039] A preparation method of an industrial solid waste phosphogypsum composite material includes the following steps:

[0040] Mix industrial solid waste phosphogypsum, cement, microsilica fume, coal cinder, phenolic resin and water, granulate, and then dry at room temperature to obtain a precursor.

[0041] Among them, the particle size of the phenolic resin is 50 μm, the particle size of the coal cinder is 100 μm, and the mass ratio of industrial solid waste phosphogypsum, cement, microsilica fume, phenolic resin and coal cinder is 100:40:6:10:8.

[0042] Heat the precursor at 130 °C for 1 h to obtain an industrial solid waste phosphogypsum composite material.

[0043] Example 3

[0044] A preparation method of an industrial solid waste phosphogypsum composite material includes the following steps:

[0045] Mix industrial solid waste phosphogypsum, cement, microsilica fume, coal cinder, phenolic resin and water, granulate, and then dry at room temperature to obtain a precursor.

[0046] Among them, the particle size of the phenolic resin is 20 μm, the particle size of the coal cinder is 50 μm, and the mass ratio of industrial solid waste phosphogypsum, cement, microsilica fume, phenolic resin and coal cinder is 100:20:3:5:4.

[0047] Heat the precursor at 120 °C for 1.5 h to obtain an industrial solid waste phosphogypsum composite material.

[0048] Comparative Example 1

[0049] The preparation method of the industrial solid waste phosphogypsum composite material is the same as that of Example 1, except that no coal cinder and phenolic resin are added, and it includes the following steps:

[0050] Mix industrial solid waste phosphogypsum, cement, microsilica fume and water, granulate, and then dry at room temperature to obtain a precursor.

[0051] Among them, the mass ratio of industrial solid waste phosphogypsum, cement and microsilica fume is 100:30:5.

[0052] The precursor is heated at 140 °C for 1 h to obtain an industrial solid waste phosphogypsum composite material.

[0053] At this time, since the calcination temperature does not reach the conversion temperature of industrial solid waste phosphogypsum, the industrial solid waste phosphogypsum in the obtained industrial solid waste phosphogypsum composite material has a high pollution level, so it is not suitable for large-scale paving on the road surface.

[0054] Comparative Example 2

[0055] A method for preparing an industrial solid waste phosphogypsum composite material is the same as the preparation steps of Example 1, except that phenolic resin is not added, and it includes the following steps:

[0056] Industrial solid waste phosphogypsum, cement, microsilica fume, coal cinder and water are mixed, granulated, and dried at room temperature to obtain a precursor.

[0057] Among them, the particle size of the phenolic resin is 40 μm, the particle size of the coal cinder is 70 μm, and the mass ratio of industrial solid waste phosphogypsum, cement, microsilica fume and coal cinder is 100:30:5:6.

[0058] The precursor is heated at 140 °C for 1 h to obtain an industrial solid waste phosphogypsum composite material.

[0059] In Examples 1 to 3 of the present invention, industrial solid waste phosphogypsum composite materials with high hardness, high strength and good durability are all prepared. Taking the industrial solid waste phosphogypsum composite material of Example 1 as an example for research, and making a comparative study with Comparative Examples 1 to 2, the specific research methods and results are as follows:

[0060] According to the "Standard for Inspection and Evaluation of Concrete Strength (GB / T50107 - 2013)" and the "Standard for Test Methods of Long-Term Performance and Durability of Ordinary Concrete (GB / T50082 - 2009)", the performance of the industrial solid waste phosphogypsum composite materials of Example 1 and Comparative Examples 1 to 2 is tested. The test results are shown in Table 1:

[0061] Table 1 Performance test table of the industrial solid waste phosphogypsum composite materials of Example 1 and Comparative Examples 1 to 2

[0062]

[0063] The results show that the mechanical properties of Example 1 are significantly better than those of Comparative Example 1 and Comparative Example 2, and the apparent density indicates that the industrial solid waste phosphogypsum composite material of Example 1 has a higher density; comparing the apparent densities of Example 1 and Comparative Example 2 shows that phenolic resin effectively improves the density of the industrial solid waste phosphogypsum composite material. Comparing Comparative Example 1 and Comparative Example 2 shows that after the coal cinder burns, pores are generated, resulting in a decrease in the density of the industrial solid waste phosphogypsum composite material, and thus both the apparent density and mechanical properties decrease.

[0064] In accordance with "GB / T5484-2012 Chemical Analysis Method for Gypsum", "JC / T2073 Determination Methods for Phosphorus and Fluorine in Phosphogypsum", and "GB / T36141 Analysis Method for Phase Composition of Building Gypsum", the industrial solid waste phosphogypsum composite materials of Example 1 and Comparative Examples 1-2 were tested, and the test results are shown in Table 2:

[0065] Table 2 Component Content Table of Industrial Solid Waste Phosphogypsum Composite Materials in Example 1 and Comparative Examples 1-2

[0066] Phosphogypsum raw material Example 1 Comparative Example 1 Comparative Example 2 <![CDATA[CaSO4·2H2O%]]> 90.63 2.18 72.15 2.05 <![CDATA[CaSO4·0.5H2O%]]> -- 87.21 15.38 88.03 <![CDATA[Water-soluble P2O5%]]> 0.75 0.024 0.53 0.021 Water-soluble F% 0.29 0.015 0.22 0.014

[0067] The results in Table 2 show that the content of CaSO4·2H2O in the phosphogypsum raw material is 90.63%. In Example 1 and Comparative Example 2 where phosphogypsum and coal cinder were mixed and then calcined, CaSO4·2H2O was effectively reduced, while CaSO4·0.5H2O was effectively increased, indicating that the decomposition of CaSO4·2H2O was basically completely achieved with the assistance of coal cinder; since the raw material of Comparative Example 1 did not contain coal cinder, calcination at 140°C did not reach the complete decomposition temperature and only partial decomposition was achieved.

[0068] Compared with the phosphogypsum raw material, the water-soluble P2O5 and water-soluble F in Example 1 and Comparative Example 2 were effectively reduced, that is, the impurity content decreased significantly, overcoming the problem of environmental pollution of industrial solid waste phosphogypsum. While in Comparative Example 1, during the partial decomposition of CaSO4·2H2O, the combustion of soluble phosphorus and fluorine was also insufficient, resulting in still high contents of soluble phosphorus and fluorine.

[0069] Next, a scanning electron microscope test was carried out on the industrial solid waste phosphogypsum composite material of Example 1, and the results are as Figure 1 shown. It can be seen through Figure 1 that there are some pores in the industrial solid waste phosphogypsum composite material, which are introduced after the coal cinder burns; except for the pores, the industrial solid waste phosphogypsum composite material is a dense overall structure. The dense effect is on the one hand that microsilica powder, coal cinder and phenolic resin with different particle sizes are used as raw materials to fill the gaps between cement particles, and on the other hand that phenolic resin is used as the raw material to form a network structure after heating and achieve complete densification with the cement.

[0070] Obviously, those skilled in the art can make various modifications and deformations to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and deformations of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention is also intended to include these modifications and deformations. The above-described embodiments are only preferred embodiments cited to fully illustrate the present invention, and the scope of protection is not limited thereto. Equivalent substitutions or transformations made by those skilled in the art on the basis of the present invention are all within the scope of protection of the present invention, and the scope of protection of the present invention shall be subject to the claims.

Claims

1. A preparation method of an industrial solid waste phosphogypsum composite material, characterized in that, It includes the following steps: Mix industrial solid waste phosphogypsum, cement, microsilica fume, coal cinder, phenolic resin and water, and obtain a precursor through granulation and drying; Heat the precursor at 120°C to 140°C for 1h to 1.5h to obtain an industrial solid waste phosphogypsum composite material; The mass ratio of industrial solid waste phosphogypsum, cement, microsilica fume, phenolic resin and coal cinder is 100:20 - 40:3 - 6:5 - 10:4 - 8.

2. The preparation method of an industrial solid waste phosphogypsum composite material according to claim 1, characterized in that, The particle size of the phenolic resin is less than 50μm, and the particle size of the coal cinder is 50μm - 100μm.

3. The preparation method of an industrial solid waste phosphogypsum composite material according to claim 1, wherein The industrial solid waste phosphogypsum is the waste generated during the production of phosphoric acid in the phosphate fertilizer industry, and its main chemical component is CaSO4·2H2O. The mass percentage of CaSO4·2H2O in the industrial solid waste phosphogypsum is 80% - 98%.

4. The preparation method of an industrial solid waste phosphogypsum composite material according to claim 1, characterized in that, The microsilica fume is selected from Elkem 940 microsilica fume, and its average particle size is 0.1μm - 0.15μm.

5. An industrial solid waste phosphogypsum composite material prepared by the preparation method according to any one of claims 1 - 4.

6. The industrial solid waste phosphogypsum composite material according to claim 5, wherein The particle size of the industrial solid waste phosphogypsum composite material is 5mm - 20mm.

7. An application of the industrial solid waste phosphogypsum composite material according to claim 5 in the preparation of highway base materials.

8. The application according to claim 7, wherein The application method is: using the industrial solid waste phosphogypsum composite material as a filler to obtain a highway base material.

9. The application according to claim 7, characterized in that The application method is: using the industrial solid waste phosphogypsum composite material as an aggregate, and mixing and curing it with the raw materials of concrete to obtain a highway base material.

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