A method for firing a sulfuric acid residue-based ceramicized aggregate with adjustable expansion ratio

Abstract

This invention belongs to the field of solid waste resource utilization technology, and relates to a method for firing sulfuric acid slag-based vitrified aggregate with adjustable expansion ratio. The method involves drying sulfuric acid slag, phosphorus mud, and contaminated soil, followed by ball milling to obtain powder; mixing the powder with an expansion agent to obtain a mixture; granulating the mixture with water to form aggregate blanks; heating the aggregate blanks to 100-120℃ for drying; preheating the dried aggregate blanks to 300-600℃, then further heating to 1080-1200℃ for firing; and finally, rapidly cooling the sintered aggregate blanks at room temperature to obtain the final product. This firing method not only allows for adjustment of the expansion ratio and density of sulfuric acid slag-based vitrified aggregates during the preparation process, but also enables high-value resource utilization of various difficult-to-treat solid wastes.

Description

Technical Field

[0001] This invention belongs to the field of solid waste resource utilization technology, and relates to a method for firing sulfuric acid slag-based vitrified aggregate with adjustable expansion ratio. Background Technology

[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] Sulfuric acid slag is the solid residue produced after pyrite is roasted, desulfurized, and oxidized in a fluidized bed furnace to produce sulfuric acid. Each ton of sulfuric acid produced generates 0.8–1.1 tons of slag, resulting in a huge annual output. The main components of sulfuric acid slag are Fe₂O₃, Fe₃O₄, CaSO₄, and SiO₂, while also containing toxic and harmful heavy metals such as copper, lead, zinc, sulfur, and arsenic. Long-term storage not only occupies a large amount of land but also causes significant pollution to the environment if it enters water and soil. Therefore, it is necessary to develop high-value-added technologies for the resource utilization of sulfuric acid slag to meet the needs of zero-waste city construction.

[0004] In the process of preparing ceramsite and ceramic materials, clay or binders must be added to form the desired shape. The inventors discovered that in the preparation of vitrified aggregates from raw materials such as sulfuric acid slag, the chemical composition varies significantly due to differences in region and batch. This makes it difficult to effectively control the expansion ratio and density during the preparation of vitrified aggregates, thus hindering the increase in the yield of sulfuric acid slag vitrified aggregates and affecting the high-value utilization of sulfuric acid slag in building materials. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the purpose of this invention is to provide a method for firing sulfuric acid slag-based vitrified aggregate with adjustable expansion ratio. This method not only enables the adjustment of the expansion ratio and density of sulfuric acid slag-based vitrified aggregate during the preparation process, but also enables the high-value resource utilization of various difficult-to-treat solid wastes.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows:

[0007] On one hand, a method for firing sulfuric acid slag-based vitrified aggregate with adjustable expansion ratio involves drying sulfuric acid slag, phosphorus mud, and contaminated soil, followed by ball milling to obtain powder; mixing the powder with an expansion agent to obtain a mixture; granulating the mixture with water to form aggregate blanks; heating the aggregate blanks to 100-120°C for drying; preheating the dried aggregate blanks to 300-600°C, then continuing the preheating process to 1080-1200°C for firing; and finally, rapidly cooling the sintered aggregate blanks at room temperature to obtain the final product.

[0008] The composition, by dry weight, consists of 40-60 parts sulfuric acid residue, 10-30 parts phosphorus mud, 10-50 parts contaminated soil, and 0.5-1 part expanding agent.

[0009] The expansion mechanism of the vitrified aggregate prepared by this invention is as follows: during the high-temperature firing process, Fe2O3, C and other substances inside the raw material react to release gas, and at the same time, the liquid phase formed encapsulates the gas, and after cooling, a honeycomb porous structure is formed.

[0010] The sulfuric acid slag raw material used in this invention has a SiO2 content between 30% and 42% and an Fe2O3 content between 45% and 55%. The high Fe2O3 content reacts with the phosphorus mud, contaminated soil, and C in the added expanding agent to release gases such as CO and CO2. During the rapid heating stage, these gases are enveloped by the generated liquid phase, causing the aggregate to expand. In addition to the influence of the raw material composition, the sintering regime of the aggregate also has a certain influence on the expansion of the aggregate; the possible reactions during the preparation process are as follows (1)-(5):

[0011] C + O₂ → CO₂ (1)

[0012] C + CO₂ → 2CO (2)

[0013] 2Fe₂O₃ + C → 4FeO + CO₂ (3)

[0014] 3Fe₂O₃ + CO → 2Fe₃O₄ + CO₂ (4)

[0015] Fe3O4 + C → 3FeO + CO (5)

[0016] This invention achieves the purpose of controlling the expansion ratio and density of vitrified aggregate by adjusting different raw material ratios, expansion agent addition ratios, heating programs, and firing temperatures to generate gas of different volumes in aggregates under different conditions.

[0017] On the other hand, a sulfuric acid slag-based vitrified aggregate is obtained by the above-mentioned firing method.

[0018] Thirdly, the application of the aforementioned sulfuric acid slag-based vitrified aggregate as a building material in construction.

[0019] The beneficial effects of this invention are as follows:

[0020] (1) Compared with the traditional sintering method for preparing aggregates, the present invention can control the expansion of vitrified aggregates under the condition of meeting the standards for lightweight aggregates in concrete. While increasing the output of vitrified aggregates, the prepared products have low density and high strength, which can be adapted to different application scenarios.

[0021] (2) The raw materials of the sulfuric acid slag vitrified aggregate prepared by this invention are all from solid waste, which greatly reduces the amount of solid waste, realizes the high-value resource utilization of solid waste, and greatly saves natural resources.

[0022] (3) In the high-temperature preparation stage, the present invention can burn, decompose and fix organic pollutants, heavy metals and other substances in sulfuric acid residue, polluted soil and phosphorus mud into aggregates, thereby achieving the harmless treatment of solid waste. Detailed Implementation

[0023] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0024] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0025] Given that current methods for firing aggregates are difficult to effectively control the expansion ratio and density of sulfuric acid slag-based vitrified aggregates, this invention proposes a method for firing sulfuric acid slag-based vitrified aggregates with adjustable expansion ratios.

[0026] A typical embodiment of the present invention provides a method for firing sulfuric acid slag-based vitrified aggregate with adjustable expansion ratio. The method involves drying sulfuric acid slag, phosphorus mud, and contaminated soil, followed by ball milling to obtain powder; mixing the powder with an expansion agent to obtain a mixture; granulating the mixture with water to form aggregate blanks; heating the aggregate blanks to 100–120°C for drying; preheating the dried aggregate blanks to 300–600°C, then further preheating to 1080–1200°C for firing; and finally, rapidly cooling the sintered aggregate blanks at room temperature to obtain the final product.

[0027] The composition, by dry weight, consists of 40-60 parts sulfuric acid residue, 10-30 parts phosphorus mud, 10-50 parts contaminated soil, and 0.5-1 part expanding agent.

[0028] In some embodiments, sulfuric acid residue, phosphorus mud, and contaminated soil are dried until the moisture content is less than 0.5% by mass. The drying process is carried out at a temperature of 100–120°C for 4–8 hours.

[0029] In some embodiments, the particle size of the powder is 80-100 mesh.

[0030] In some embodiments, the ball milling conditions are: ball mill speed set to 200-250 r / min, tumbling speed set to 4-8 times / min, and ball milling time set to 20-40 min.

[0031] In some embodiments, the drying time of the aggregate blank is 2 to 6 hours.

[0032] In some embodiments, the programmed heating rate of the preheating treatment is 5 to 15 °C / min.

[0033] In some embodiments, the heat preservation time for preheating is 10 to 25 minutes.

[0034] In some embodiments, the temperature rise rate of the firing process is 10–30 °C / min.

[0035] In some embodiments, the holding time for the firing process is 8 to 20 minutes.

[0036] Another embodiment of the present invention provides a sulfuric acid slag-based vitrified aggregate, obtained by the above-described firing method.

[0037] In some embodiments, the density is 300–700 kg / m³. 3 The cylinder compressive strength is 4-8 MPa.

[0038] In some embodiments, the expansion factor is 0.5 to 7.

[0039] A third embodiment of the present invention provides an application of the above-mentioned sulfuric acid slag-based vitrified aggregate as a building material in construction.

[0040] To enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments.

[0041] In the following examples, density and compressive strength were tested in accordance with the standard "Lightweight aggregates and their test methods - Part 1: Lightweight aggregates" (GB / T17431.1-2010).

[0042] The formula for calculating the expansion factor is:

[0043]

[0044] In the formula: V2 is the volume of vitrified aggregate, in cm. 3 V1 is the volume of the unembryo, in cm. 3 .

[0045] Example 1

[0046] A method for firing sulfuric acid slag-based vitrified aggregate with adjustable expansion ratio, comprising the following raw materials by mass parts (dry weight):

[0047] 50 parts by weight of sulfuric acid residue, 10 parts by weight of phosphorus mud, 40 parts by weight of contaminated soil, and 0.5 parts by weight of expanding agent.

[0048] The specific steps are as follows:

[0049] (1) Dry the sulfuric acid residue, phosphorus mud and contaminated soil at 110℃ for 6 hours until the moisture content of the raw materials is less than 0.5%.

[0050] (2) Set the ball mill speed to 220 r / min and the turning speed to 6 times / min. Put the dried raw material into the ball mill and mill it for 30 minutes. Then filter and sieve to obtain powder of 80-100 mesh.

[0051] (3) Mix the above powder with the expanding agent evenly to obtain a mixture.

[0052] (4) Add the mixture to the disc granulator and mix with water to make vitrified aggregate blanks.

[0053] (5) The prepared vitrified aggregate blank is dried in an oven at 105°C for 4 hours.

[0054] (6) Place the dried vitrified aggregate blank into a high-temperature furnace and preheat it to 450°C at a heating rate of 10°C / min, and hold it for 15 minutes.

[0055] (7) After preheating, heat the temperature to 1170℃ at a rate of 10℃ / min and hold for 10min.

[0056] (8) After firing, the sintered balls are taken out of the high-temperature furnace and placed at room temperature for rapid cooling to obtain sulfuric acid slag vitrified aggregate with adjustable expansion ratio.

[0057] The density of the sulfuric acid slag vitrified aggregate prepared in this embodiment is 510 kg / m³. 3 The cylinder compressive strength is 5.2 MPa. The expansion ratio is 2.7.

[0058] Example 2

[0059] A method for firing sulfuric acid slag-based vitrified aggregate with adjustable expansion ratio, comprising the following raw materials by mass parts (dry weight):

[0060] 45 parts by weight of sulfuric acid residue, 22 parts by weight of phosphorus mud, 32 parts by weight of contaminated soil, and 1 part by weight of expanding agent.

[0061] The specific steps are as follows:

[0062] (1) Dry the sulfuric acid residue, phosphorus mud and contaminated soil at 110℃ for 6 hours until the moisture content of the raw materials is less than 0.5%.

[0063] (2) Set the ball mill speed to 220 r / min and the turning speed to 6 times / min. Put the dried raw material into the ball mill and mill it for 30 minutes. Then filter and sieve to obtain 80-100 mesh powder.

[0064] (3) Mix the above powder with the expanding agent evenly to obtain a mixture.

[0065] (4) Add the above mixture to a disc granulator and mix with water to make a vitrified aggregate blank.

[0066] (5) The prepared vitrified aggregate blank is dried in an oven at 110°C for 3 hours.

[0067] (6) Place the dried vitrified aggregate blank into a high-temperature furnace and preheat it to 500°C at a heating rate of 15°C / min, and keep it at that temperature for 25 minutes.

[0068] (7) After preheating, heat the temperature to 1100℃ at a rate of 15℃ / min and hold for 15min.

[0069] (8) After firing, the sintered balls are taken out of the high-temperature furnace and placed at room temperature for rapid cooling to obtain sulfuric acid slag vitrified aggregate with adjustable expansion ratio.

[0070] The density of the sulfuric acid slag vitrified aggregate prepared in this embodiment is 400 kg / m³. 3 The cylinder compressive strength is 4.3 MPa. The expansion ratio is 4.6.

[0071] Example 3

[0072] A method for firing sulfuric acid slag-based vitrified aggregate with adjustable expansion ratio, comprising the following raw materials by mass parts (dry weight):

[0073] 56 parts by weight of sulfuric acid residue, 28 parts by weight of phosphorus mud, 16 parts by weight of contaminated soil, and 0.7 parts by weight of expanding agent.

[0074] The specific steps are as follows:

[0075] (1) Dry the sulfuric acid residue, phosphorus mud and contaminated soil at 110℃ for 6 hours until the moisture content of the raw materials is less than 0.5%.

[0076] (2) Set the ball mill speed to 220 r / min and the turning speed to 6 times / min. Put the dried raw material into the ball mill and mill it for 30 minutes. Then filter and sieve to obtain 80-100 mesh powder.

[0077] (3) Mix the above powder with the expanding agent evenly to obtain a mixture.

[0078] (4) Add the above mixture to a disc granulator and mix with water to make a vitrified aggregate blank.

[0079] (5) The prepared vitrified aggregate blank is dried in an oven at 115°C for 5 hours.

[0080] (6) Place the dried vitrified aggregate blank into a high-temperature furnace and preheat it to 600°C at a heating rate of 15°C / min, and keep it at that temperature for 10 minutes.

[0081] (7) After preheating, heat the temperature to 1150℃ at a rate of 20℃ / min and hold for 20min.

[0082] (8) After firing, the sintered balls are taken out of the high-temperature furnace and placed at room temperature for rapid cooling to obtain sulfuric acid slag vitrified aggregate with adjustable expansion ratio.

[0083] The density of the sulfuric acid slag vitrified aggregate prepared in this embodiment is 365 kg / m³. 3 The cylinder compressive strength is 4.1 MPa. The expansion ratio is 6.1.

[0084] It should be noted that the above-described embodiments provide a detailed explanation of the technical solution of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, additions, or similar substitutions made within the scope of the principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for firing sulfuric acid slag-based vitrified aggregate with adjustable expansion ratio, characterized in that, Sulfuric acid residue, phosphorus mud, and contaminated soil are dried and then ball-milled to obtain powder. The powder is mixed evenly with an expanding agent to obtain a mixture. The mixture is granulated with water to form aggregate blanks. The aggregate blanks are heated to 100-120 ℃ and dried. The dried aggregate blanks are preheated to 300-600 ℃ and then further preheated to 1080-1200 ℃ for firing. The sintered balls after firing are rapidly cooled at room temperature to obtain the final product. The composition, by dry weight, is as follows: 40-60 parts sulfuric acid residue, 10-30 parts phosphorus mud, 10-50 parts contaminated soil, and 0.5-1 part expanding agent. The preheating process has a temperature ramp rate of 5~15 ℃ / min; Alternatively, the heat preservation time for preheating is 10~25 min; The heating rate for the firing process is 10~30 ℃ / min; Alternatively, the holding time for firing treatment is 8~20 min.

2. The method for firing sulfuric acid slag-based vitrified aggregate with adjustable expansion ratio as described in claim 1, characterized in that, The sulfuric acid residue, phosphorus mud, and contaminated soil were dried until the moisture content was less than 0.5%.

3. The method for firing sulfuric acid slag-based vitrified aggregate with adjustable expansion ratio as described in claim 1, characterized in that, The particle size of the powder is 80~100 mesh.

4. The method for firing sulfuric acid slag-based vitrified aggregate with adjustable expansion ratio as described in claim 1, characterized in that, The ball milling conditions are as follows: ball mill speed set to 200~250 r / min, turning speed set to 4~8 times / min, and ball milling time set to 20~40 min.

5. A sulfuric acid slag-based vitrified aggregate, characterized in that, Obtained by the firing method described in any one of claims 1 to 4.

6. The sulfuric acid slag-based vitrified aggregate as described in claim 5, characterized in that its density... 300~700 kg / m 3 The cylinder compressive strength is 4~8 MPa.

7. The sulfuric acid slag-based vitrified aggregate as described in claim 5, characterized in that, The expansion factor is 0.5 to 7.

8. The application of the sulfuric acid slag-based vitrified aggregate as described in any one of claims 5 to 7 as a building material in construction.

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