Expanded porous lightweight ceramsite, its preparation method and application

Abstract

The application provides an expanded porous lightweight ceramsite and a preparation method and application thereof, and belongs to the technical field of solid waste recycling. In the application, the soil, red mud, silica ash, fly ash, phosphor tailings and rice husk powder scraped from the weathered layer of granite are used as raw materials, the raw materials are granulated and formed through reasonable design of raw material ratio, and the expanded porous lightweight ceramsite with the advantages of small bulk density, high strength, good heat preservation and heat insulation effect, good fire resistance, good moisture absorption and the like is obtained through a suitable calcination procedure. The dependence on traditional raw materials in the production of the expanded porous lightweight ceramsite is reduced, and the purpose of recycling and utilizing various solid wastes into harmless resources is realized.

Description

Technical Field

[0001] This invention belongs to the field of solid waste recycling technology, and particularly relates to the recycling of solid wastes such as weathered granite surface soil, red mud, phosphorus tailings, fly ash and silica fume. Specifically, it relates to a method for preparing expanded porous lightweight ceramsite using the above-mentioned raw materials, the expanded porous lightweight ceramsite prepared according to the method, and the application of the expanded porous lightweight ceramsite. Background Technology

[0002] Expanded porous lightweight ceramsite is an environmentally friendly functional material with excellent properties such as high strength, lightweight, thermal insulation, sound absorption, fire resistance, and earthquake resistance. It is widely used in construction, metallurgy, chemical industry, and petroleum. Currently, expanded porous lightweight ceramsite on the market is mainly prepared from traditional raw materials such as clay and shale. However, the resources of these traditional raw materials are dwindling, and environmental pollution problems are becoming increasingly serious.

[0003] Red mud, phosphorus tailings, fly ash, and silica fume are solid wastes generated during industrial production. Weathered granite surface soil refers to the soil removed by mechanically agitating and scrubbing weathered granite. The large-scale accumulation of these solid wastes not only occupies significant land resources but also causes severe environmental pollution. Red mud is an insoluble residue, primarily derived from the alumina refining process of bauxite. It contains a large amount of highly alkaline chemicals; even after a 10-fold dilution, its pH value remains between 11.25 and 11.50. This extremely high pH value determines the strong corrosiveness of red mud to organisms, metals, and siliceous materials. Highly alkaline wastewater seeping into the ground or entering surface water raises the pH value of water bodies, exceeding national standards. Large accumulations of fly ash generate dust, polluting the atmosphere; if discharged into waterways, it causes river siltation, and its toxic chemicals pose a threat to human health and other organisms. Phosphate tailings are solid waste generated during the smelting of phosphate rock. They contain large amounts of heavy metals and harmful substances such as cadmium, lead, mercury, and arsenic, posing significant risks to the environment and human health. Accumulated silica ash pollutes soil, water, and air; furthermore, excessive silica ash content in concrete can harm human health and negatively impact concrete durability. Therefore, using these solid wastes as raw materials to prepare expanded porous lightweight ceramsite can reduce reliance on traditional raw materials such as clay and shale, achieve resource recycling of solid waste, and simultaneously reduce environmental pollution and product manufacturing costs. Summary of the Invention

[0004] This invention provides a method for preparing expanded porous lightweight ceramsite using soil, red mud, silica fume, fly ash, phosphorus tailings, and rice husk powder washed from weathered granite layers as raw materials. This method achieves the goal of recycling and reusing solid waste resources, and produces expanded porous lightweight ceramsite with advantages such as low bulk density, high strength, good thermal insulation, good fire resistance, and good moisture absorption.

[0005] Specifically, the present invention achieves the above objectives through the following technical solutions:

[0006] A method for preparing expanded porous lightweight ceramsite includes the following steps:

[0007] W1. Raw material pretreatment: The weathered granite is crushed, and water is added to the crushed weathered granite particles for mechanical stirring. The stirred slurry is then settled, and the tailings are collected. The tailings are dried and ground to obtain the surface soil of the weathered granite. Phosphate tailings, red mud, silica fume, fly ash, and rice husk powder are ground separately. All ground raw materials are sieved, and the undersize material is dried. Then, the chemical composition of each raw material is tested.

[0008] W2. Determine the amount of raw materials: Based on the Riley phase diagram and the chemical composition of each raw material in step W1, the raw material ratio is determined by experiment as follows: 30-70 parts of weathered granite surface soil, 20-50 parts of red mud, 10-30 parts of silica fume, 30-50 parts of fly ash, 20-50 parts of phosphorus tailings, and 10-30 parts of rice husk powder.

[0009] W3. Mixing and molding: Weigh all raw materials according to the mass proportions in step W2, mix them evenly, add water, mix evenly, granulate into spherical particles of 5-25mm, and dry and mold them.

[0010] W4. Firing of ceramsite: Place the dried and shaped ceramsite from step W3 into a muffle furnace and preheat it to the first temperature; then continue to heat it to the second temperature for firing to obtain expanded porous lightweight ceramsite.

[0011] After a series of treatments, the soil washed off from the weathered granite contains high levels of SiO2, Al2O3, and fluxing agents, which are similar to the composition of clay shale, the raw material for producing ceramsite, making it suitable for producing lightweight ceramsite.

[0012] Red mud, with its rough surface, large specific surface area, and high porosity, can be added to raw materials to produce ceramsite, which not only eliminates solid waste but also produces high-performance ceramsite.

[0013] Fly ash has a low bulk density and a large specific surface area. Using it as a raw material to prepare ceramsite can improve the compressive strength of ceramsite and reduce its bulk density.

[0014] Silica fume contains a high content of amorphous silica. Adding it to the ceramsite raw material adjusts the proportion of the raw material, so that the chemical composition of the ceramsite is within the expansion range.

[0015] Rice husk powder contains a large amount of cellulose and lignin, which can produce gas when burned. Its small particle size allows it to be used as a raw material for expanded clay aggregate (ECA), creating porosity within the aggregate. This process also helps dispose of solid waste, protects the ecological environment, and yields considerable economic and social benefits. Furthermore, rice husk powder can improve the compressive strength and durability of ECA.

[0016] In a preferred embodiment, the particle size of the weathered granite particles in step W1 is 1.18–4.75 mm.

[0017] In a preferred embodiment, the amount of water added in step W1 is such that the concentration of the slurry is 20-60%.

[0018] In a preferred embodiment, the water in step W3 accounts for 20% to 35% of the total mass of all raw materials.

[0019] In a preferred embodiment, the first temperature in step W4 is 300–550°C, and the preheating time is 10–30 min.

[0020] In a preferred embodiment, the heating rate to the first temperature in step W4 is 10°C / min.

[0021] In a preferred embodiment, the second temperature in step W4 is 1100-1200°C, and the calcination time is 10-30 min.

[0022] In a preferred embodiment, the heating rate to the second temperature in step W4 is 10°C / min.

[0023] In a preferred embodiment, the weathered granite surface soil contains, by mass percentage, 40-55% SiO2, 15-30% Al2O3, 2-3% Fe2O3, 2-3% K2O, 3-4% Na2O, 1-2% CaO, and 1-2% MgO.

[0024] In a preferred embodiment, the red mud contains, by mass percentage, 30-40% SiO2, 10-20% Al2O3, 35-45% Fe2O3, 3-4% Na2O, 3-4% TiO2, 1-2% CaO, and 1-2% MgO.

[0025] In a preferred embodiment, the fly ash contains, by mass percentage, 50-65% SiO2, 20-40% Al2O3, 2-5% Fe2O3, 3-4% CaO, 3-4% K2O, 1-2% Na2O, and 1-2% MgO.

[0026] In a preferred embodiment, the phosphorus tailings contain, by mass percentage, 4-5% SiO2, 1-2% Al2O3, 1-2% Fe2O3, 40-70% CaO, 20-40% MgO, 1-2% TiO2, and 1-2% Na2O.

[0027] In a preferred embodiment, the silica fume mainly contains 95-98% SiO2 and 0-1% Al2O3, 0-1% Fe2O3, 0-1% TiO2, 0-1% Na2O, 0-1% K2O, 0-1% CaO, and 0-1% MgO by mass percentage.

[0028] This invention also provides expandable porous lightweight ceramsite prepared according to the above preparation method. The expandable porous lightweight ceramsite has an expansion rate between 100% and 180% and a bulk density between 280 and 700 kg / m³. 3 The apparent density is between 480 and 850 kg / m³. 3 It has a porosity between 45% and 75%, a compressive strength between 5 and 15 MPa, and a water absorption rate between 1.0% and 3.0% per hour; its performance meets the standards for high-strength lightweight aggregates specified in GB / T 17431.1-2010, and can be used to prepare products with at least one of the following properties: lightweight and high strength, heat insulation, fire resistance, moisture absorption, and sound insulation.

[0029] This expanded porous lightweight ceramsite, due to its lightweight and high strength characteristics, can be used to prepare concrete to reduce the overall weight of buildings and has great potential for application in load-bearing structures. Because of its expansion rate exceeding 90%, the high expansion rate and the gas-trapping enamel layer on the surface of the ceramsite result in numerous closed, non-interconnected pores within the ceramsite. Therefore, concrete prepared using this ceramsite has a lower thermal conductivity, which improves the thermal insulation effect of the concrete.

[0030] The present invention has the following beneficial effects: (1) The present invention uses weathered granite surface soil, red mud, silica fume, fly ash, phosphorus tailings and rice husk powder as raw materials. By designing a reasonable raw material ratio, the raw materials are granulated and calcined in a suitable manner to prepare expanded porous lightweight ceramsite, which reduces the dependence on traditional raw materials (clay, shale, etc.) and realizes the purpose of harmless resource recycling of various solid wastes. (2) The expanded porous lightweight ceramsite prepared by the method of the present invention has the characteristics of being lightweight and high-strength (bulk density of 280-700 kg / m³).3 Between these, the minimum compressive strength is significantly higher than the minimum compressive strength of 3MPa required for high-strength ceramsite, which has obvious advantages in the construction field. Using the ceramsite prepared by this invention to make wall materials can not only reduce the total weight of the building, but also give it great potential in load-bearing structures. (3) The ceramsite prepared by the preparation method of this invention has thermal insulation properties. Due to its expansion rate of more than 90%, the high expansion rate and the glaze layer on the surface of the ceramsite trap gas, so that the ceramsite contains more closed and unconnected pores. When it is used to prepare concrete, it can reduce the thermal conductivity of the concrete. In addition, the produced ceramsite has a low bulk density. The combination of the two makes the ceramsite have good thermal insulation properties. (4) The ceramsite prepared by the preparation method of this invention has excellent fire resistance. Ordinary ceramsite concrete or ceramsite concrete blocks integrate thermal insulation, earthquake resistance, frost resistance and fire resistance. In particular, the fire resistance is more than 4 times that of ordinary concrete. For the same fire resistance period, the thickness of ceramsite concrete slabs is 20% thinner than that of ordinary concrete. In addition, ceramsite can also be used to prepare refractory concrete with a refractoriness of less than 1200℃. (5) The ceramsite prepared by the preparation method of the present invention has good moisture absorption. The ceramsite has high porosity and good moisture absorption, making it suitable for use in humid environments. (6) The ceramsite prepared by the preparation method of the present invention has sound absorption and sound insulation properties. Because the ceramsite prepared by the present invention contains a lot of pores, when sound passes through the ceramsite, a large amount of sound waves will be absorbed by the pores and will not penetrate, so it has excellent sound absorption performance. (7) The preparation method in the present invention is simple and easy to mechanize. While eliminating a large amount of solid waste, the process is low-cost, quick to take effect, and has no waste discharge. The preheating generated after firing in the muffle furnace is also well utilized. The qualified products obtained can be widely used in the construction, refractory insulation materials, and chemical and petroleum industries. Detailed Implementation

[0031] The following description, in conjunction with embodiments, clearly and completely illustrates the technical solutions of the present invention, enabling those skilled in the art to fully understand the invention. Obviously, the described embodiments are merely some preferred embodiments of the present invention, and not all embodiments. Any equivalent modifications or substitutions made by those skilled in the art to the following embodiments without creative effort are within the protection scope of the present invention.

[0032] Ordinal numbers used herein, such as "first" and "second," are for descriptive purposes only to distinguish similar objects and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Methods not described in detail in the following embodiments are conventional methods well-known to those skilled in the art.

[0033] In the following embodiments, the weathered granite surface soil used refers to the granite surface soil obtained by cutting, crushing, roller-rolling, magnetic separation, and sieving the weathered granite. Granite particles with a diameter of 1.18–4.75 mm are placed in a mechanical mixing tank with a certain amount of water (e.g., water with a slurry concentration of 40%) and stirred. The water is then deposited, and the deposit is the weathered granite surface soil. By mass percentage, this weathered granite surface soil contains 40-55% SiO2, 15-30% Al2O3, 2-3% Fe2O3, 2-3% K2O, 3-4% Na2O, 1-2% CaO, and 1-2% MgO.

[0034] The red mud used refers to the polluting waste residue discharged after refining alumina from bauxite. Its red color is due to the high iron oxide content. By mass percentage, red mud contains 30-40% SiO2, 10-20% Al2O3, 35-45% Fe2O3, 3-4% Na2O, 3-4% TiO2, 1-2% CaO, and 1-2% MgO.

[0035] Fly ash refers to the fine ash collected from the flue gas after coal combustion and is a major solid waste discharged from coal-fired power plants. Fly ash is usually gray or grayish-black. By mass percentage, fly ash contains 50-65% SiO2, 20-40% Al2O3, 2-5% Fe2O3, 3-4% CaO, 3-4% K2O, 1-2% Na2O, and 1-2% MgO.

[0036] The phosphate tailings used are solid waste generated during the phosphate ore mining and beneficiation process, mainly originating from the tailings slag remaining after the concentrate extraction, and are classified as mining solid waste. Their main chemical composition includes calcium oxide, magnesium oxide, silicon dioxide, and phosphorus pentoxide. By mass percentage, phosphate tailings contain 4-5% SiO2, 1-2% Al2O3, 1-2% Fe2O3, 40-70% CaO, 20-40% MgO, 1-2% TiO2, and 1-2% Na2O.

[0037] The silica fume used is an ultrafine siliceous powder material, formed when SiO2 and Si gas produced during the smelting of ferrosilicon alloys and industrial silicon are rapidly oxidized and condensed by oxygen in the air. The main component of silica fume is extremely fine (0.1–0.2 μm) amorphous silica, with an average particle size 100 times smaller than cement and a specific surface area of ​​approximately 15–20 m². 2 / g. By mass percentage, silica fume mainly contains 95-98% SiO2 and 0-1% Al2O3, 0-1% Fe2O3, 0-1% TiO2, 0-1% Na2O, 0-1% K2O, 0-1% CaO, and 0-1% MgO.

[0038] The rice husk powder used is a byproduct extracted from rice. It is the part left after removing the rice husk and cleaning the rice during the rice processing. The main components are rice bran and rice husk fragments, and a small amount of rice flour. It contains a large amount of cellulose, lignin, and silicon dioxide. The carbon released from its combustion can be used to create pores.

[0039] The method for preparing expanded porous lightweight ceramsite in the following embodiments includes the following steps:

[0040] W1. Raw Material Pretreatment: After the collected weathered granite is crushed and rolled, water (to a slurry concentration of 20-60%) is added to the weathered granite particles with a particle size of 1.18-4.75mm for mechanical stirring. The stirred slurry is then allowed to settle, and tailings are collected. The tailings are dried and ground, and phosphate tailings, red mud, silica fume, fly ash, and rice husk powder are ground separately. All ground raw materials are individually sieved through a 200-mesh sieve. The undersize material is dried at 105±5℃, and then the chemical composition of each raw material is tested.

[0041] W2. Determine the raw material dosage: Referring to the Riley phase diagram and based on the chemical composition of each raw material tested in step W1, determine the following proportions through experiments: 30-70 parts weathered granite surface soil, 20-50 parts red mud, 10-30 parts silica fume, 30-50 parts fly ash, 20-50 parts phosphate tailings, and 10-30 parts rice husk powder. The chemical composition range of the raw materials that form sintering expansion properties according to the Riley phase diagram is: SiO2: 40%-79%, Al2O3: 10%-25%, and flux: 13-26%.

[0042] W3. Mixing and Molding: Weigh all the raw materials according to the mass proportions in step W2, mix them evenly, add water accounting for 20-35% of the total mass of the raw materials, mix evenly, granulate into spherical particles of 5-25mm, and dry and mold them at 105±5℃.

[0043] W4. Firing of ceramsite: Place the dried and shaped ceramsite from step W3 into a muffle furnace and heat it from room temperature to 300-550℃ at a heating rate of 10℃ / min for 10-30 minutes; then continue heating at a heating rate of 10℃ / min to 1100-1200℃ for 10-30 minutes to obtain expanded porous lightweight ceramsite.

[0044] In step W1, depending on the actual situation of the raw materials, the original phosphorus tailings can be crushed, rolled, and ball-milled first; the muddy red mud can be dried, crushed, and ball-milled; silica fume powder and fly ash smaller than 100 mesh can be ball-milled; and the untreated rice husks can be stirred into powder in a small wall-breaking machine. Then, all the obtained raw materials can be sieved independently through a 200-mesh sieve.

[0045] Unless otherwise specified, all parts in this document are parts by weight. Components not listed in the various raw materials and their contents do not affect the technical effect of the present application.

[0046] Example 1

[0047] This embodiment provides an expanded porous lightweight ceramsite, comprising the following raw materials in parts by weight: 50 parts weathered granite surface soil, 50 parts red mud, 20 parts silica fume, 40 parts fly ash, 20 parts phosphorus tailings, and 20 parts rice husk powder. The weathered granite surface soil contains 55% SiO2, 15% Al2O3, 2.5% Fe2O3, 2.99% K2O, 3.89% Na2O, 1.99% CaO, 1.54% MgO, and 0.22% TiO2; the red mud contains 30% SiO2, 15% Al2O3, 40% Fe2O3, 3.12% Na2O, 3.96% TiO2, 1.31% CaO, and 1.23% MgO; the silica fume contains 95% SiO2 and 0.67% Al2O3, 0.23% Fe2O3, 0.29% K2O, 0.56% TiO2, 0.98% CaO, 0.34% MgO, and 0.76% Na2O; and the fly ash contains 50%... The phosphate tailings contain 4.23% SiO2, 1.23% Al2O3, 1.45% Fe2O3, 60% CaO, 28% MgO, 1.56% TiO2, and 1.43% Na2O.

[0048] The preparation method of the expanded porous lightweight ceramsite includes the following steps:

[0049] W1. Raw Material Pretreatment: The collected weathered granite is crushed and rolled in a series of processes. Water (to a slurry concentration of 40%) is added to the 1.18mm weathered granite particles for mechanical stirring. The stirred slurry is then allowed to settle, and tailings are collected. The tailings are dried and ball-milled. Phosphate tailings are crushed, rolled, and ball-milled. Red mud in its muddy state is dried, crushed, and ball-milled. Silica fume and fly ash smaller than 100 mesh are ball-milled. Untreated rice husks are ground into powder in a small high-speed blender. All raw materials are independently sieved through a 200-mesh sieve. The undersize material is dried at 105±5℃ and then subjected to chemical composition analysis for mineral composition.

[0050] W2. Determine the amount of raw materials: Based on the Riley phase diagram, determine the composition range of the expanded chemical components, and calculate the amount of each raw material based on its composition. Specifically, the amount of weathered granite surface soil is 50 parts, red mud is 50 parts, silica fume is 20 parts, fly ash is 40 parts, phosphorus tailings is 20 parts, and rice husk powder is 20 parts.

[0051] W3. Mixing and Molding: Weigh all the raw materials according to the mass proportions in step W2, mix them evenly, add water accounting for 20% of the total mass of the raw materials, mix evenly, granulate into 20mm spherical particles, and dry at 105±5℃.

[0052] W4. Firing of ceramsite: Place the dried and shaped ceramsite from step W3 into a muffle furnace and heat it from room temperature to 450℃ at a heating rate of 10℃ / min for 10 min; then continue heating at a heating rate of 10℃ / min to 1200±10℃ for 15 min to obtain expanded porous lightweight ceramsite.

[0053] Example 2

[0054] This embodiment provides an expanded porous lightweight ceramsite, comprising the following raw materials in parts by weight: 60 parts weathered granite surface soil, 30 parts red mud, 10 parts silica fume, 45 parts fly ash, 50 parts phosphorus tailings, and 25 parts rice husk powder. The weathered granite surface soil contains 53% SiO2, 30% Al2O3, 3% Fe2O3, 2.87% K2O, 3.02% Na2O, 1.5% CaO, and 1.02% MgO; the red mud contains 34% SiO2, 20% Al2O3, 35% Fe2O3, 3.19% Na2O, 3.01% TiO2, 1.11% CaO, and 1.98% MgO; the silica fume contains 97% SiO2 and 0.37% Al2O3, 0.26% Fe2O3, 0.03% K2O, 0.25% TiO2, 0.63% CaO, 0.01% MgO, and 0.32% Na2O; and the fly ash contains 54% SiO2, 33% Al2O3, 3.02% Fe2O3, and 3.12% MgO. CaO, 3.06% K2O, 1.01% Na2O, 1.97% MgO; the phosphate tailings contain 4.01% SiO2, 1.14% Al2O3, 1.04% Fe2O3, 55% CaO, 35% MgO, 1.99% TiO2, and 1.01% Na2O.

[0055] The preparation method of expanded porous lightweight ceramsite in this embodiment is basically the same as that in Example 1, except that:

[0056] In step W, the particle size of the weathered granite is 1.70 mm, and the slurry concentration is 20%.

[0057] In step W2, the surface soil of the weathered granite layer consists of 60 parts, red mud 30 parts, silica fume 10 parts, fly ash 45 parts, phosphorus tailings 50 parts, and rice husk powder 25 parts.

[0058] In step W3, add water accounting for 27% of the total mass of the raw materials, mix evenly, and then granulate into 5mm spherical particles.

[0059] In step W4, the temperature is increased from room temperature to 550℃ at a heating rate of 10℃ / min and preheated for 20min; then the temperature is increased to 1150±10℃ at a heating rate of 10℃ / min and calcined for 10min to obtain expanded porous lightweight ceramsite.

[0060] Example 3

[0061] This embodiment provides an expanded porous lightweight ceramsite, comprising the following raw materials in parts by weight: 70 parts weathered granite surface soil, 20 parts red mud, 30 parts silica fume, 35 parts fly ash, 35 parts phosphorus tailings, and 10 parts rice husk powder. The weathered granite surface soil contains 50% SiO2, 25% Al2O3, 2.16% Fe2O3, 2.02% K2O, 3.56% Na2O, 1.65% CaO, and 1.32% MgO; the red mud contains 31% SiO2, 13% Al2O3, 45% Fe2O3, 3.99% Na2O, 3.56% TiO2, 1.04% CaO, and 1.02% MgO; the silica fume contains 98% SiO2 and 0.13% Al2O3, 0.014% Fe2O3, 0.23% K2O, 0.05% TiO2, 0.013% CaO, 0.09% MgO, and 0.012% Na2O; and the fly ash contains 65% SiO2, 20% Al2O3, 5% Fe2O3, and 3.01% Na2O. CaO, 3.04% K2O, 1.96% Na2O, 1.04% MgO; the phosphate tailings contain 4.12% SiO2, 1.34% Al2O3, 1.03% Fe2O3, 70% CaO, 20% MgO, 1.03% TiO2, and 1.08% Na2O.

[0062] The preparation method of expanded porous lightweight ceramsite in this embodiment is basically the same as that in Example 1, except that:

[0063] In step W, the particle size of the weathered granite particles is 2.36 mm, and the slurry concentration is 45%.

[0064] In step W2, the surface soil of the weathered granite layer consists of 70 parts, red mud 20 parts, silica fume 30 parts, fly ash 35 parts, phosphorus tailings 35 parts, and rice husk powder 10 parts.

[0065] In step W3, add water accounting for 30% of the total mass of the raw materials, mix evenly, and then granulate into 25mm spherical particles.

[0066] In step W4, the temperature is increased from room temperature to 400℃ at a heating rate of 10℃ / min and preheated for 30min; then the temperature is increased to 1100±10℃ at a heating rate of 10℃ / min and calcined for 25min to obtain expanded porous lightweight ceramsite.

[0067] Example 4

[0068] This embodiment provides an expanded porous lightweight ceramsite, comprising the following raw materials in parts by weight: 30 parts weathered granite surface soil, 35 parts red mud, 25 parts silica fume, 30 parts fly ash, 30 parts phosphorus tailings, and 15 parts rice husk powder. The weathered granite surface soil contains 48% SiO2, 29% Al2O3, 2% Fe2O3, 2.67% K2O, 3.98% Na2O, 1.34% CaO, and 1.99% MgO; the red mud contains 40% SiO2, 11% Al2O3, 38% Fe2O3, 3.01% Na2O, 3.21% TiO2, 1.97% CaO, and 1.09% MgO; the silica fume contains 96% SiO2 and 0.03% Al2O3, 0.96% Fe2O3, 0.33% K2O, 0.67% TiO2, 0.35% CaO, 0.01% MgO, and 0.995% Na2O; and the fly ash contains 55% SiO2, 29% Al2O3, 4.56% Fe2O3, and 3.98% Na2O. CaO, 3.97% K2O, 1.45% Na2O, 1.67% MgO; the phosphate tailings contain 4.06% SiO2, 1.02% Al2O3, 1.96% Fe2O3, 60% CaO, 29% MgO, 1.01% TiO2, and 1.08% Na2O.

[0069] The preparation method of expanded porous lightweight ceramsite in this embodiment is basically the same as that in Example 1, except that:

[0070] In step W, the particle size of the weathered granite is 3.35 mm, and the slurry concentration is 50%.

[0071] In step W2, the surface soil of the weathered granite layer consists of 30 parts, red mud 35 parts, silica fume 25 parts, fly ash 30 parts, phosphorus tailings 30 parts, and rice husk powder 15 parts.

[0072] In step W3, add water accounting for 35% of the total mass of the raw materials, mix evenly, and then granulate into 10mm spherical particles.

[0073] In step W4, the temperature is increased from room temperature to 350℃ at a heating rate of 10℃ / min and preheated for 25min; then the temperature is increased to 1170±10℃ at a heating rate of 10℃ / min and calcined for 20min to obtain expanded porous lightweight ceramsite.

[0074] Example 5

[0075] This embodiment provides an expanded porous lightweight ceramsite, comprising the following raw materials in parts by weight: 65 parts weathered granite surface soil, 25 parts red mud, 15 parts silica fume, 50 parts fly ash, 40 parts phosphorus tailings, and 30 parts rice husk powder. The weathered granite surface soil contains 40% SiO2, 30% Al2O3, 2.54% Fe2O3, 2.13% K2O, 3.01% Na2O, 1.01% CaO, and 1.34% MgO; the red mud contains 35% SiO2, 10% Al2O3, 44% Fe2O3, 3.21% Na2O, 3.09% TiO2, 1.23% CaO, and 1.43% MgO; the silica fume contains 95% SiO2 and 0.97% Al2O3, 0.28% Fe2O3, 0.53% K2O, 0.63% TiO2, 0.98% CaO, 0.46% MgO, and 0.76% Na2O; and the fly ash contains 62% SiO2, 24% Al2O3, 3.69% Fe2O3, and 3.03% MgO. CaO, 3.21% K2O, 1.23% Na2O, 1.23% MgO; the phosphate tailings contain 4.98% SiO2, 1.975% Al2O3, 1.31% Fe2O3, 40% CaO, 40% MgO, 1.42% TiO2, and 2% Na2O.

[0076] The preparation method of expanded porous lightweight ceramsite in this embodiment is basically the same as that in Example 1, except that:

[0077] In step W, the particle size of the weathered granite is 4.75 mm, and the slurry concentration is 60%.

[0078] In step W2, the surface soil of the weathered granite layer consists of 65 parts, red mud 25 parts, silica fume 15 parts, fly ash 50 parts, phosphorus tailings 40 parts, and rice husk powder 30 parts.

[0079] In step W3, add water accounting for 27% of the total mass of the raw materials, mix evenly, and then granulate into 15mm spherical particles.

[0080] In step W4, the temperature is increased from room temperature to 300℃ at a heating rate of 10℃ / min and preheated for 20min; then the temperature is increased to 1130±10℃ at a heating rate of 10℃ / min and calcined for 30min to obtain expanded porous lightweight ceramsite.

[0081] Comparative Example 1

[0082] This comparative example provides an expanded porous lightweight ceramsite, whose composition is the same as that of Example 1, and whose preparation method is basically the same as that of Example 1, except that:

[0083] In step W4, the temperature is increased from room temperature to 450℃ at a heating rate of 10℃ / min and preheated for 10 min; then the temperature is increased to 1300℃ at a heating rate of 10℃ / min and calcined for 15 min to obtain expanded porous lightweight ceramsite.

[0084] Comparative Example 2

[0085] This comparative example provides an expanded porous lightweight ceramsite, whose composition is the same as that of Example 3, and whose preparation method is basically the same as that of Example 3, except that:

[0086] In step W4, the temperature is increased from room temperature to 400℃ at a heating rate of 10℃ / min and preheated for 30min; then the temperature is increased to 1000℃ at a heating rate of 10℃ / min and calcined for 25min to obtain expanded porous lightweight ceramsite.

[0087] Ceramsite performance test

[0088] 1. The expansion rate, bulk density, apparent density, porosity, cylinder compressive strength, and 1-hour water absorption rate of the ceramsite in Examples 1-5 and Comparative Examples 1 and 2 were tested according to the methods in GB / T 17431.2-2010 "Lightweight aggregates and their test methods Part 2: Lightweight aggregates test methods". The test results are shown in Table 1.

[0089] Table 1. Performance tests of expanded clay in Examples 1-5 and Comparative Examples 1-2

[0090]

[0091] As can be seen from Table 1, the expansion rate of the ceramsite in Examples 1 to 5 is between 100% and 180%, and the bulk density is between 280 and 700 kg / m³. 3 The apparent density is between 480 and 850 kg / m³. 3 The porosity is between 45% and 75%, the compressive strength is between 5 and 15 MPa, and the water absorption rate is between 1.0% and 3.0% per hour; its performance meets the standards for high-strength lightweight aggregates specified in GB / T 17431.1-2010 "Lightweight aggregates and their test methods Part 1: Lightweight aggregates".

[0092] 2. Heavy metal content test in the expanded clay aggregate of Example 1

[0093] After crushing and sieving the ceramsite from Example 1 and Comparative Example 2 to a particle size of less than 3 mm, pure water and fine ceramsite powder were mixed at a mass ratio of 10:1. The mixture was then vibrated at 110 rpm for 8 hours on a horizontal shaker and allowed to stand for 16 hours. The metal concentration in the supernatant was then tested, and the test results are shown in Table 2.

[0094] Table 2. Test results of heavy metal content in expanded clay aggregates of Example 1 and Comparative Example 2.

[0095] heavy metal Example 1 Comparative Example 2 Limit As (mg / L) 0.01 0.03 0.05 Cr (hexavalent) (mg / L) Not detected 0.04 0.05 Cd (mg / L) Not detected 0.002 0.005 Ni (mg / L) Not detected 0.03 0.02 Zn (mg / L) 0.002 0.134 1 Pb (mg / L) Not detected 0.013 0.01 Cu (mg / L) 0.342 0.567 1 Ba (mg / L) 0.031 0.234 0.7

[0096] As shown in Table 2, As, Zn, Cu, and Ba were all detected in the raw materials used to prepare the ceramsite, but their contents were all below the limits specified in GB 5085.3-2007 "Identification Standard for Hazardous Waste - Leaching Toxicity Identification". Cr, Cd, Ni, and Pb were not detected. However, the concentrations of heavy metals As, Cr, Cd, Ni, Zn, Pb, Cu, and Ba in Comparative Example 2 were all higher than the metal ion concentrations in Example 1. Furthermore, the concentrations of metal ions Ni and Pb were both higher than the limits specified in GB 5085.3-2007. This indicates that after the raw solid waste is calcined at a suitable temperature to prepare expanded porous lightweight ceramsite, heavy metals can be effectively solidified within the ceramsite.

[0097] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Various modifications and variations can be made to the present invention by any person skilled in the art. Any simple equivalent changes and modifications made based on the scope of protection of the present invention and the content of the specification should be included within the scope of protection of the present invention.

Claims

1. A method for preparing expanded porous lightweight ceramsite, characterized in that, The method comprises the following steps: W1, raw material pretreatment: crushing weathered granite, adding water to the crushed weathered granite particles for mechanical stirring, and collecting tailings after the stirred slurry is settled; drying and grinding the tailings to obtain weathered granite surface soil; Phosphorus tailings, red mud, silica ash, fly ash and rice husk powder are respectively ground; all the ground raw materials are respectively sieved, and the undersize materials are dried, and then the chemical components of each raw material are tested; W2, determining the amount of raw materials: based on the Riley phase diagram and the chemical components of each raw material in step W1, the raw material ratio is determined through experiments: weathered granite surface soil 30-60 parts, red mud 30-50 parts, silica ash 10-30 parts, fly ash 30-50 parts, phosphorus tailings 20-50 parts, and rice husk powder 15-25 parts; W3, mixing and forming: according to the mass fraction in step W2, various raw materials are weighed and mixed uniformly, water is added, and the mixture is granulated into spherical particles with a diameter of 5-25 mm, and then dried and formed; W4, firing of the ceramic particles: the ceramic particles after drying and forming in step W3 are placed in a muffle furnace, heated to a first temperature for preheating, and then continuously heated to a second temperature for calcination, to obtain expanded porous lightweight ceramic particles.

2. The method of producing expanded lightweight ceramsite according to claim 1, characterized in that, The mass of water in step W3 is 20%-35% of the total mass of the raw materials.

3. The method of producing expanded lightweight ceramsite according to claim 1, characterized in that, In step W4, the first temperature is 300-550°C, and the preheating time is 10-30 min; or / and the second temperature is 1100-1200°C, and the calcination time is 10-30 min.

4. The method of producing expanded lightweight ceramsite according to claim 1, characterized in that, The weathered granite surface soil contains 40-55% SiO2, 15-30% Al2O3, 2-3% Fe2O3, 2-3% K2O, 3-4% Na2O, 1-2% CaO, and 1-2% MgO, by mass percentage.

5. The method of producing expanded lightweight ceramsite according to claim 1, characterized in that, The red mud contains 30-40% SiO2, 10-20% Al2O3, 35-45% Fe2O3, 3-4% Na2O, 3-4% TiO2, 1-2% CaO, and 1-2% MgO, by mass percentage.

6. The method of producing expanded lightweight ceramsite according to claim 1, characterized in that, The fly ash contains 50-65% SiO2, 20-40% Al2O3, 2-5% Fe2O3, 3-4% CaO, 3-4% K2O, 1-2% Na2O, and 1-2% MgO, by mass percentage.

7. The method of producing expanded lightweight ceramsite according to claim 1, characterized in that, The phosphorus tailings contain 4-5% SiO2, 1-2% Al2O3, 1-2% Fe2O3, 40-70% CaO, 20-40% MgO, 1-2% TiO2, and 1-2% Na2O, by mass percentage.

8. The method of producing expanded lightweight ceramsite according to claim 1, characterized in that, The silica ash mainly contains 95-98% SiO2, 0-1% Al2O3, 0-1% Fe2O3, 0-1% TiO2, 0-1% Na2O, 0-1% K2O, 0-1% CaO, and 0-1% MgO, by mass percentage.

9. The expanded porous lightweight ceramic particles prepared by the preparation method of any one of claims 1-8.

10. Use of the expanded lightweight ceramic aggregate according to claim 9 for the production of a product having at least one of the following properties: lightweight, high strength, thermal insulation, fire resistance, moisture absorption, sound insulation.

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