Low-thermal-conductivity expanded ceramsite based on rare earth modification and fly ash solid waste and preparation method thereof

Abstract

The present application relates to the technical field of ceramsite, in particular to a low-thermal-conductivity expanded ceramsite based on rare earth modification and fly ash solid waste and a preparation method thereof, which is made of the following raw materials in parts by weight: 5-15 parts of high-aluminum poly-light waste brick powder, 40-60 parts of fly ash, 10-20 parts of waste anvil powder, 10-15 parts of coal gangue powder, 5-9 parts of rare earth modified light powder and 1-3 parts of additional additives. The rare earth modified light powder is prepared by wet co-grinding, spray granulation and high-temperature sintering of fly ash powder and lanthanum cerium carbonate powder. The present application uses solid waste such as high-aluminum poly-light waste brick powder, fly ash, waste anvil powder and coal gangue powder to prepare low-thermal-conductivity expanded aggregate through scientific proportioning and reasonable process, and the raw materials are widely distributed, easy to obtain and low in cost. The sintering temperature in the preparation process is low, energy is saved, and the prepared product is low in density, high in strength, smooth in surface and low in water absorption.

Description

Technical fields:

[0001] This invention belongs to the field of ceramsite technology, specifically relating to a low thermal conductivity sintering ceramsite based on rare earth modification and fly ash solid waste, and its preparation method. Background technology:

[0002] According to relevant data, the five major industries in my country—electricity and heat production and supply, ferrous metal smelting and rolling, non-ferrous metal mining and beneficiation, coal mining and washing, and ferrous metal mining and beneficiation—account for nearly 80% of the total solid waste generated. The large amounts of industrial solid waste accumulated in my country, as well as the new waste generated each year, not only encroach on valuable land resources but also cause varying degrees of pollution to the soil, water, and air.

[0003] Fly ash is a solid waste generated during the production process of coal-fired power plants, accounting for approximately 5% to 20% of the total coal consumption. my country's annual fly ash emissions are approximately 500 million tons, and the current amount of fly ash stockpiled in my country exceeds 2 billion tons, with ash storage sites occupying approximately 4 × 10⁴ km² of land. 2 This not only severely pollutes the environment but also occupies a large amount of land resources. Fly ash contains a large amount of silicon and aluminum oxides. If the main components of fly ash are utilized, it can be "turned from waste into treasure" and achieve the goal of protecting the environment. Currently, there are technologies for preparing ceramsite, fracturing proppant, building materials, and daily-use ceramics by doping fly ash, but the consumption of fly ash is not very large.

[0004] Coal gangue is a type of solid waste in the mining industry, generated during tunneling, mining, and coal washing. It includes washed gangue from coal washing plants, hand-sorted gangue from coal production, coal and rock discharged during semi-coal and rock tunnel excavation, and a mixture of white gangue (excluding coal-bearing strata) piled together with the gangue. Coal gangue is a mixture of carbonaceous, argillaceous, and sandy shale, with a low calorific value. It contains 20%–30% carbon and some contains humic acid. China has accumulated approximately 1000 Mt of coal gangue over the years, and continues to discharge about 100 Mt annually, not only occupying land but also posing a risk of spontaneous combustion, air pollution, and fires. Coal gangue is mainly used in the production of gangue cement, lightweight aggregate for concrete, refractory bricks, and other building materials. It can also be used for coal recycling, coal-gangue co-firing for power generation, the production of crystalline aluminum chloride, water glass, and other chemical products, the extraction of precious and rare metals, and as fertilizer. Coal gangue is a rock composed of organic and inorganic compounds deposited along with coal during the coal-forming process. It typically occurs in thin layers within or at the top and bottom of coal seams. Based on its main mineral content, coal gangue is classified into claystone, sandstone, carbonate, and aluminous rocks. According to its source and final state, it can be divided into three main categories: tunneling gangue, coal washing gangue, and natural gangue. The amount of coal gangue discharged varies considerably depending on coal seam conditions, mining conditions, and washing processes. Generally, tunneling gangue accounts for about 10% of raw coal production, while coal washing gangue accounts for 12% to 18% of the raw coal processed.

[0005] High-alumina lightweight waste brick powder is a low-density thermal insulation refractory material produced in the refractory materials industry. It is used for thermal insulation parts of various high-temperature kilns. The consumption is large and the recycling rate is insufficient. However, due to its lightweight properties, it can be recycled and reused for the remanufacturing of lightweight, low-conductivity products.

[0006] Saggers are used by rare earth enterprises to sinter rare earth oxides and fluorides. Baotou rare earth enterprises alone use as many as 60,000 to 80,000 worn-out saggers annually. If these are not utilized, they will generate a large amount of solid waste, occupying factory space and impacting the environment. The main components of these waste saggers are Al2O3 ≥ 40.6%, SiO2 ≥ 45%, Fe2O3 ≤ 1.8%, and MgO ≥ 4%. If they can be recycled and effectively utilized, they will have extremely high economic and social value.

[0007] Rare earth elements are hailed as "vitamins of industry," possessing irreplaceable superior magnetic, optical, and electrical properties. They play a significant role in improving product performance, increasing product variety, and enhancing production efficiency. Due to their extensive use and limited quantity, rare earth elements have become crucial for improving product structure, enhancing technological content, and promoting technological progress in various industries, finding widespread applications in metallurgy, military, petrochemicals, glass and ceramics, agriculture, and new materials.

[0008] Low thermal conductivity sintering expanded clay aggregate has the characteristics of light weight, high strength, low thermal conductivity, heat insulation and fireproofing, and heat and sound insulation. These excellent properties have led to its increasing application in the field of high-rise building materials. It not only reduces the weight of building materials, but also gives them sufficient strength, and also has heat insulation and sound insulation effects.

[0009] Fly ash ceramsite is a type of artificial lightweight aggregate made from fly ash as the main raw material, with the addition of small amounts of auxiliary materials (binders, fluxes, combustion aids, etc.) through sintering. It possesses advantages such as light weight, corrosion resistance, frost resistance, earthquake resistance, and good insulation. However, some challenges remain in its industrial production. Traditional expanded clay aggregates may rely too heavily on natural raw materials (such as clay and shale) and fail to fully utilize the advantages of industrial solid waste (such as fly ash, coal gangue, and waste refractory materials), thus failing to give full play to the advantages of the lightweight and active components of solid waste.

[0010] Existing expanded clay aggregates mostly rely on a single foaming agent (such as calcium carbonate or iron oxide) to generate gas within a narrow temperature range, which easily leads to pore coalescence, uneven pore size, and low closed-cell rate, making it difficult to achieve both bulk density and strength. Using natural raw materials or a single foaming agent may result in problems such as high resource consumption, high cost, and high carbon emissions.

[0011] Traditional ceramsite forms fewer types of crystal phases during firing (such as mainly quartz and mullite) and lacks a multiphase composite reinforcement mechanism (such as kyanite, cristobalite, magnesium aluminum spinel, cordierite, etc.), resulting in poor toughness of the skeleton structure and low compressive strength.

[0012] Due to the non-uniform pore structure, single crystal phase, and few grain and phase boundaries, the phonon scattering effect is weak, and the heat conduction path is relatively unobstructed, resulting in a high thermal conductivity and unsatisfactory heat preservation performance. Furthermore, existing technologies may rely on high temperatures (>1200℃) to form a liquid phase or crystals. Summary of the Invention: To address the shortcomings of existing technologies, this invention provides a low thermal conductivity sintering ceramsite based on rare earth modification and fly ash solid waste. This invention utilizes solid waste high-alumina lightweight waste brick powder, fly ash, waste crucible powder, and coal gangue powder, and prepares low thermal conductivity sintering aggregate through scientific proportioning and a reasonable process. The raw materials are widely distributed, readily available, and low in cost; the firing temperature during preparation is low, saving energy; the prepared product has low density, high strength, smooth surface, and low water absorption. Specifically, this invention uses materials with certain lightweight and high-strength properties (high-alumina lightweight waste brick powder and rare earth modified lightweight powder), and simultaneously employs a temperature-phase gradient pore-forming process: Lanthanum and cerium carbonate of rare earth are introduced, and the carbonate ions gradually decompose starting at around 900℃. On one hand, this transforms into higher-strength rare earth oxides to strengthen the skeletal structure of the aggregate product; on the other hand, the CO2 gas generated during decomposition acts as a gas-flow pore-forming agent to reduce bulk density. In the higher temperature range, the pore-forming effect is dominated by the introduced silicon carbide, which can react with oxides in the raw materials to form silicon oxide at high temperatures, releasing CO2 gas. Within this temperature range, high-alumina lightweight waste brick powder, fly ash, waste crucible powder, and coal gangue powder work together to form a low-melting-point liquid phase, which effectively encapsulates the gas. Ultimately, the ceramsite forms small and dense closed pores, resulting in greater cylinder compressive strength and lower thermal conductivity compared to ordinary sintered ceramsite. At high temperatures, lanthanum and cerium carbonate promote the decomposition of low-melting-point sodium feldspar and potassium feldspar phases in solid waste raw materials. During the reaction, the rare earth oxides produced by the high-temperature decomposition of rare earth carbonates can promote the formation of low-melting-point liquid phases, providing a more sufficient ionic thermal motion environment for the aluminum phase (mainly provided by high-alumina lightweight waste brick powder, coal gangue powder, and waste crucible powder) and the silicon phase (mainly provided by fly ash and coal gangue powder, providing active silica). This promotes the formation of kyanite and cristobalite phases at lower temperatures. The waste crucible powder contains MgO, which can form a small amount of magnesium aluminum spinel and cordierite phases, increasing the toughness of the ceramsite and further enhancing the strength of the ceramsite skeleton components, thus improving the compressive strength of the ceramsite. Furthermore, because the ceramsite provided by this invention contains a variety of crystal phases and crystal forms, by refining the grains or introducing a multiphase structure, the number of grain boundaries and phase boundaries is increased, thereby enhancing the scattering of phonons and reducing the mean free path, further reducing the thermal conductivity and improving the thermal insulation performance.

[0013] Specifically, the first aspect of the present invention provides a low thermal conductivity sintering ceramsite based on rare earth modification and fly ash solid waste. The ceramsite is made from the following raw materials in parts by weight: 5-15 parts of high-alumina lightweight waste brick powder, 40-60 parts of fly ash, 10-20 parts of waste crucible powder, 10-15 parts of coal gangue powder, 5-9 parts of rare earth modified lightweight powder, and 1-3 parts of additives.

[0014] As a further explanation of the present invention, the rare earth modified light powder is prepared by wet co-milling of fly ash powder and lanthanum and cerium carbonate powder, spray granulation, and high-temperature sintering.

[0015] As a further explanation of the present invention, the added additives include rare earth lanthanum and cerium carbonate and silicon carbide.

[0016] As a further explanation of the present invention, its performance meets the following requirements: bulk density ≤724 kg / m³, cylinder compressive strength ≥10MPa, and thermal conductivity ≤0.25 W / (m·K).

[0017] A second aspect of this invention provides a method for preparing the above-mentioned low thermal conductivity sintering ceramsite based on rare earth modification and fly ash solid waste, comprising the following steps: S1: Weigh each raw material according to the above weight proportions, and mix the pretreated high-alumina lightweight waste brick powder, fly ash, waste crucible powder, coal gangue powder, rare earth modified lightweight powder and additives evenly to obtain mixed raw materials. S2: After adding water to the mixed raw materials, raw material balls with a particle size of 2-12 mm are formed; S3: The raw material balls are fired in a stepped heating process, with the highest firing temperature being 1160-1200℃. The highest temperature point is held for 1-2 hours. After firing, the material balls are cooled to room temperature to obtain the finished product of low thermal conductivity sintered ceramsite.

[0018] As a further explanation of the present invention, the pretreatment process in S1 specifically includes: drying high-alumina lightweight waste brick powder, fly ash, waste crucible powder and coal gangue powder respectively, ball milling them and passing them through a 200-mesh sieve, with a sieve residue of less than 5%, and then packaging them for later use.

[0019] As a further explanation of the present invention, the preparation process of the rare earth modified light powder in S1 specifically includes: grinding fly ash powder and lanthanum and cerium carbonate powder together in an aqueous phase containing a dispersant until the particle size is less than 1 μm to form a slurry; spray drying the slurry to granulate it; and sintering the resulting light powder at 1000℃-1100℃ to obtain rare earth modified light powder.

[0020] As a further explanation of the present invention, the mass ratio of the fly ash powder to the lanthanum and cerium carbonate powder is (92-98):(2-8); the pH value of the suspension is controlled at 8-10 during grinding; and the inlet temperature of the spray granulation is 100℃-150℃.

[0021] As a further explanation of the present invention, in S2, the raw material pellets are prepared by an automatic pelletizing machine, and the rotation speed of the pelletizing machine is controlled within the range of 25 to 35 r / min.

[0022] As a further explanation of the present invention, the specific process of the stepped heating firing is as follows: the temperature is increased from room temperature to 200°C in 1-2 hours and held for 1-2 hours; the temperature is increased from 200°C to 900°C in 2-3 hours and held for 0.5-1 hours; the temperature is increased from 900°C to 1050°C in 1-2 hours and held for 1-2 hours; the temperature is increased from 1050°C to the highest temperature point of 1160-1200°C in 0.5-1 hours and held at this temperature point for 1-2 hours.

[0023] Compared with the prior art, the present invention has the following beneficial technical effects: 1. The main raw materials are solid waste (≥90%), which are widely distributed, readily available, and low in cost: Currently, my country has over 2 billion tons of fly ash stockpiled, which not only seriously pollutes the environment but also occupies a large amount of land resources. Therefore, the raw material cost is extremely low, and it is widely distributed and readily available. Other main raw materials (high-alumina lightweight waste brick powder, waste crucible powder, and coal gangue powder) are bulk industrial solid wastes, hence their extremely low cost.

[0024] 2. Low firing temperature and energy saving during preparation: The low thermal conductivity sintering ceramic particles provided by this invention have a firing temperature range of 1160~1200℃, resulting in low firing temperature and low energy consumption. Rare earth carbonates lanthanum and cerium carbonate have certain fluxing, sintering, gas generation, and pore-forming effects, which also reduce energy consumption to some extent and help reduce the density of the ceramic particles.

[0025] 3. The prepared product has low density, high strength, high porosity, high refractoriness, and low thermal conductivity: the low thermal conductivity sintering expanded ceramsite aggregate provided by this invention has a pelletizing qualification rate ≥95%, a sintering qualification rate ≥90%, and a bulk density ≤724kg / m³. 3 The cylinder compressive strength is ≥10MPa, the porosity is ≥35%, the refractoriness is ≥1200℃, and the thermal conductivity is ≤0.25W / (m·K).

[0026] 4. This provides a new approach for the resource utilization of solid waste high-alumina lightweight waste brick powder, fly ash, waste crucible powder, and coal gangue powder, filling the gap in the field of preparing lightweight high-strength aggregates from solid waste high-alumina lightweight waste brick powder, fly ash, waste crucible powder, coal gangue powder, and rare earth carbonates. Attached image description: Figure 1 The flowchart illustrates the process for preparing low thermal conductivity sintering ceramsite based on rare earth modification and fly ash solid waste, as provided in this embodiment of the invention.

[0027] Figure 2 The XRD analysis diagram of the ceramsite provided in Embodiment 1 of the present invention is shown. In the diagram, □: Al 2.272 Si 0.728 O 4.864 ;○: Mg2Bi 0.116 (Al4Si5O18 ) ;★:Al2O 3。 Detailed implementation method:

[0028] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] In the following examples, "parts" refers to parts by weight.

[0030] Example 1 This embodiment provides a low thermal conductivity sintering ceramsite based on rare earth modification and fly ash solid waste, and its preparation process is as follows: a. Raw material screening: The solid waste raw materials such as high-alumina lightweight waste brick powder, fly ash, waste crucible powder and coal gangue powder are dried in a 110℃ electric heating blast drying oven. The dried solid waste raw materials are then ball-milled to a certain extent, and then passed through a 200-mesh sieve. The residue is less than 5%, and the raw materials are packaged for later use.

[0031] b. Preparation of rare earth modified luminous powder: Add 100 parts of deionized water and 0.2 parts of ammonium polyacrylate to the dispersion tank of a grinding mill. After stirring and dispersing evenly, turn on the grinding mill and gradually add 95 parts of sieved fly ash powder and 5 parts of lanthanum and cerium carbonate powder. During the grinding process, control the pH value of the suspension at 9. When the particle size of the powder in the suspension is less than 1 μm, stop grinding. Then turn on the spray granulator, control the inlet temperature at 130℃, and uniformly feed the slurry into the spray granulator. Collect the luminous powder in the collector, and then sinter it at 1050℃ to obtain rare earth modified luminous powder.

[0032] c. Dispersion and mixing: According to the weight percentage composition: 15% high-alumina lightweight waste brick powder, 40% fly ash, 20% waste crucible powder, 15% coal gangue powder, 9% rare earth modified lightweight powder, and 1% external additives (0.5% each of rare earth lanthanum and cerium carbonate and silicon carbide). Weigh each raw material and then mix them evenly to obtain the mixed raw material.

[0033] d. Mechanical forming: Add an appropriate amount of water to the mixed raw materials and use a pelletizing machine to automatically form pellets. The pellet size range is 4-11 mm, and the speed of the pelletizing machine is controlled within 35 r / min.

[0034] e. Firing: Spread the calcined alumina powder evenly on the bottom of a square crucible, and evenly disperse the shaped aggregate balls into the square crucible; place the square crucible containing the shaped aggregate balls in an electric resistance furnace or kiln, heat for 1 hour between room temperature and 200℃, and hold for 1 hour; heat for 2 hours between 200℃ and 900℃, and hold for 1 hour; heat for 2 hours between 900℃ and 1050℃, and hold for 1 hour; heat for 1 hour between 1050℃ and the highest temperature point of 1200℃, and hold for 1 hour at the highest temperature point.

[0035] f. Finished product: The calcined aggregate pellet sample is taken out after it has cooled naturally to room temperature as the furnace temperature decreases, and the resulting low thermal conductivity calcined aggregate finished product is obtained.

[0036] The rare earth modified fly ash ceramsite prepared in this embodiment has the following performance test results: pelletizing qualification rate 95%, sintering qualification rate 93%, and bulk density 724 kg / m³. 3 The cylinder compressive strength is 13.1 MPa, the porosity is 35%, the refractoriness is 1250℃, and the thermal conductivity is 0.25 W / (m·K).

[0037] Example 2 This embodiment provides a low thermal conductivity sintering ceramsite based on rare earth modification and fly ash solid waste, and its preparation process is as follows: a. Raw material screening: The solid waste raw materials such as high-alumina lightweight waste brick powder, fly ash, waste crucible powder and coal gangue powder are dried in a 110℃ electric heating blast drying oven. The dried solid waste raw materials are then ball-milled to a certain extent, and then passed through a 200-mesh sieve. The residue is less than 5%, and the raw materials are packaged for later use.

[0038] b. Preparation of rare earth modified luminous powder: Add 100 parts of deionized water and 0.2 parts of ammonium polyacrylate to the dispersion tank of a grinding mill. After stirring and dispersing evenly, turn on the grinding mill and gradually add 95 parts of sieved fly ash powder and 5 parts of lanthanum and cerium carbonate powder. During the grinding process, control the pH value of the suspension at 9. When the particle size of the powder in the suspension is less than 1 μm, stop grinding. Then turn on the spray granulator, control the inlet temperature at 130℃, and uniformly feed the slurry into the spray granulator. Collect the luminous powder in the collector, and then sinter it at 1050℃ to obtain rare earth modified luminous powder.

[0039] c. Dispersion and mixing: According to the weight percentage composition: 5% high-alumina lightweight waste brick powder, 60% fly ash, 15% waste crucible powder, 10% coal gangue powder, 7% rare earth modified lightweight powder, and 3% external additives (1% rare earth lanthanum and cerium carbonate, 2% silicon carbide). Weigh each raw material and then mix them evenly to obtain the mixed raw material.

[0040] d. Mechanical forming: Add an appropriate amount of water to the mixed raw materials and use a pelletizing machine to automatically form pellets. The pellet size range is 3-10 mm, and the speed range of the pelletizing machine is controlled at 25 r / min.

[0041] e. Firing: Spread the calcined alumina powder evenly on the bottom of a square crucible, and evenly disperse the shaped aggregate balls into the square crucible; place the square crucible containing the shaped aggregate balls in an electric resistance furnace or kiln, heat between room temperature and 200℃ for 2 hours, and hold for 1 hour; heat between 200℃ and 900℃ for 3 hours, and hold for 0.5 hours; heat between 900℃ and 1050℃ for 1 hour, and hold for 2 hours; heat between 1050℃ and the highest temperature point of 1160℃ for 1 hour, and hold at the highest temperature point for 2 hours.

[0042] f. Finished product: The calcined aggregate pellet sample is taken out after it has cooled naturally to room temperature as the furnace temperature decreases, and the resulting low thermal conductivity calcined aggregate finished product is obtained.

[0043] The rare earth modified fly ash ceramsite prepared in this embodiment has the following performance test results: pelletizing qualification rate 96%, sintering qualification rate 91%, and bulk density 611 kg / m³. 3 The cylinder compressive strength is 10.3 MPa, the porosity is 41%, the refractoriness is 1200℃, and the thermal conductivity is 0.15 W / (m·K).

[0044] Example 3 This embodiment provides a low thermal conductivity sintering ceramsite based on rare earth modification and fly ash solid waste, and its preparation process is as follows: a. Raw material screening: The solid waste raw materials such as high-alumina lightweight waste brick powder, fly ash, waste crucible powder and coal gangue powder are dried in a 110℃ electric heating blast drying oven. The dried solid waste raw materials are then ball-milled to a certain extent, and then passed through a 200-mesh sieve. The residue is less than 5%, and the raw materials are packaged for later use.

[0045] b. Preparation of rare earth modified luminous powder: Add 100 parts of deionized water and 0.2 parts of ammonium polyacrylate to the dispersion tank of a grinding mill. After stirring and dispersing evenly, turn on the grinding mill and gradually add 95 parts of sieved fly ash powder and 5 parts of lanthanum and cerium carbonate powder. During the grinding process, control the pH value of the suspension at 9. When the particle size of the powder in the suspension is less than 1 μm, stop grinding. Then turn on the spray granulator, control the inlet temperature at 130℃, and uniformly feed the slurry into the spray granulator. Collect the luminous powder in the collector, and then sinter it at 1050℃ to obtain rare earth modified luminous powder.

[0046] c. Dispersion and mixing: According to the weight percentage composition: 11% high-alumina lightweight waste brick powder, 56% fly ash, 10% waste crucible powder, 13% coal gangue powder, 8% rare earth modified lightweight powder, and 2% external additives (1% each of rare earth lanthanum and cerium carbonate and silicon carbide). Weigh each raw material and then mix them evenly to obtain the mixed raw material.

[0047] d. Mechanical forming: Add an appropriate amount of water to the mixed raw materials and use a pelletizing machine to automatically form pellets. The pellet size range is 5-12mm, and the speed range of the pelletizing machine is controlled at 31r / min.

[0048] e. Firing: Spread the calcined alumina powder evenly on the bottom of a square crucible, and evenly disperse the shaped aggregate balls into the square crucible; place the square crucible containing the shaped aggregate balls in an electric resistance furnace or kiln, and heat between room temperature and 200℃ for 2 hours, and hold for 1 hour; heat between 200℃ and 900℃ for 2 hours, and hold for 0.5 hours; heat between 900℃ and 1050℃ for 2 hours, and hold for 1 hour; heat between 1050℃ and the highest temperature point of 1180℃ for 0.5 hours, and hold at the highest temperature point for 2 hours.

[0049] f. Finished product: The calcined aggregate pellet sample is taken out after it has cooled naturally to room temperature as the furnace temperature decreases, and the resulting low thermal conductivity calcined aggregate finished product is obtained.

[0050] The rare earth modified fly ash ceramsite prepared in this embodiment has the following performance tests: pelletizing qualification rate 96%, sintering qualification rate 92%, and bulk density 652 kg / m³. 3 The cylinder compressive strength is 11.6 MPa, the porosity is 36%, the refractoriness is 1210℃, and the thermal conductivity is 0.18 W / (m·K).

[0051] Example 4 This embodiment provides a low thermal conductivity sintering ceramsite based on rare earth modification and fly ash solid waste, and its preparation process is as follows: a. Raw material screening: The solid waste raw materials such as high-alumina lightweight waste brick powder, fly ash, waste crucible powder and coal gangue powder are dried in a 110℃ electric heating blast drying oven. The dried solid waste raw materials are ball-milled to a certain extent, and then the solid waste raw materials are passed through a 200-mesh sieve. The residue is less than 5%, and the materials are packaged for later use. b. Preparation of rare earth modified luminous powder: Add 100 parts of deionized water and 0.2 parts of ammonium polyacrylate to the dispersion tank of a grinding mill. After stirring and dispersing evenly, turn on the grinding mill and gradually add 95 parts of sieved fly ash powder and 5 parts of lanthanum and cerium carbonate powder. During the grinding process, control the pH value of the suspension at 9. When the particle size of the powder in the suspension is less than 1 μm, stop grinding. Then turn on the spray granulator, control the inlet temperature at 130℃, and uniformly feed the slurry into the spray granulator. Collect the luminous powder in the collector, and then sinter it at 1050℃ to obtain rare earth modified luminous powder.

[0052] c. Dispersion and mixing: According to the weight percentage composition: 7% high-alumina lightweight waste brick powder, 55% fly ash, 18% waste crucible powder, 12% coal gangue powder, 5% rare earth modified lightweight powder, and 3% external additives (1% each of rare earth lanthanum and cerium carbonate and silicon carbide). Weigh each raw material and then mix them evenly to obtain the mixed raw material.

[0053] d. Mechanical forming: Add an appropriate amount of water to the mixed raw materials and use a pelletizing machine to automatically form pellets. The pellet size range is 6-11 mm, and the speed range of the pelletizing machine is controlled at 28 r / min.

[0054] e. Firing: Spread the calcined alumina powder evenly on the bottom of a square crucible, and evenly disperse the shaped aggregate balls into the square crucible; place the square crucible containing the shaped aggregate balls in an electric resistance furnace or kiln, and heat between room temperature and 200℃ for 1.5 hours, and hold for 1.5 hours; heat between 200℃ and 900℃ for 2.5 hours, and hold for 1 hour; heat between 900℃ and 1050℃ for 1.5 hours, and hold for 1.5 hours; heat between 1050℃ and the highest temperature point of 1200℃ for 1 hour, and hold at the highest temperature point for 1.5 hours.

[0055] f. Finished product: The calcined aggregate pellet sample is taken out after it has cooled naturally to room temperature as the furnace temperature decreases, and the resulting low thermal conductivity calcined aggregate finished product is obtained.

[0056] The rare earth modified fly ash ceramsite prepared in this embodiment has the following performance tests: pelletizing qualification rate 95%, sintering qualification rate 94%, and bulk density 679 kg / m³. 3 The cylinder compressive strength is 12.2 MPa, the porosity is 38%, the refractoriness is 1230℃, and the thermal conductivity is 0.21 W / (m·K).

[0057] Comparative Example 1: This comparative example provides a type of ceramsite whose preparation process differs from that of Example 1 in that the high-alumina lightweight waste brick powder component is omitted. The composition by weight percentage is: 0% high-alumina lightweight waste brick powder, 40% fly ash, 35% waste crucible powder, 15% coal gangue powder, 9% rare earth modified lightweight powder, and 1% additives (0.5% each of rare earth lanthanum and cerium carbonate and silicon carbide). Each raw material is weighed and then uniformly mixed to obtain a mixed raw material.

[0058] The performance of the expanded clay prepared in this comparative example is as follows: bulk density 820 kg / m³ 3 It has a porosity of 25% and a thermal conductivity of 0.41 W / (m·K).

[0059] The bulk density of the product provided in this comparative example is increased (>750 kg / m³). 3 The porosity decreased (<30%) and the thermal conductivity increased [>0.3W / (m·K)], both exceeding the peak values ​​of the three indicators involved in this invention, making it impossible to obtain the high-adaptability, low-thermal-conductivity scalding-expansion ceramic particles of this invention.

[0060] Comparative Example 2: This comparative example provides a type of ceramsite whose preparation process differs from Example 1 in that the fly ash component is omitted. The composition by weight percentage is: 45% high-alumina lightweight waste brick powder, 0% fly ash, 20% waste crucible powder, 15% coal gangue powder, 9% rare earth modified lightweight powder, and 1% additives (0.5% each of rare earth lanthanum and cerium carbonate and silicon carbide). Each raw material is weighed and then uniformly mixed to obtain a mixed raw material.

[0061] In addition to providing silicon and aluminum sources, fly ash also plays an important role in ball-forming and binding in the formulation of this invention (the specific surface area of ​​the fly ash used in this invention is ≥300 m² / kg). If this component is removed, the ball-forming qualification rate will be below 10%, and it may even be impossible to carry out the process step "d, mechanical forming".

[0062] Comparative Example 3: This comparative example provides a type of ceramsite whose preparation process differs from that of Example 1 in that the waste crucible powder component is omitted. The composition by weight percentage is: 15% high-alumina lightweight waste brick powder, 60% fly ash, 0% waste crucible powder, 15% coal gangue powder, 9% rare earth modified lightweight powder, and 1% additives (0.5% each of rare earth lanthanum and cerium carbonate and silicon carbide). Each raw material is weighed and then uniformly mixed to obtain a mixed raw material.

[0063] The performance of the ceramsite prepared in this comparative example is as follows: compressive strength 7.3 MPa, refractoriness 1090℃.

[0064] Waste sagger powder contains a large amount of high-strength crystalline phase - mullite phase and high thermal shock stability phase - cordierite phase. Removing this component will result in a serious decrease in compressive strength (less than 8 MPa) and a decrease in refractoriness (<1200℃), making it impossible to obtain high-strength, high-refractive-strength, low-thermal-conductivity sintered ceramsite.

[0065] Comparative Example 4: This comparative example provides a type of ceramsite whose preparation process differs from that of Example 1 in that the coal gangue powder component is omitted. The composition by weight percentage is: 15% high-alumina lightweight waste brick powder, 40% fly ash, 35% waste crucible powder, 0% coal gangue powder, 9% rare earth modified lightweight powder, and 1% additives (0.5% each of rare earth lanthanum and cerium carbonate and silicon carbide). Each raw material is weighed and then uniformly mixed to obtain a mixed raw material.

[0066] The performance of the expanded clay prepared in this comparative example is as follows: bulk density 783 kg / m³ 3 It has a porosity of 28%, a thermal conductivity of 0.34 W / (m·K), and a sintering pass rate of 65%.

[0067] In addition to providing silicon and aluminum sources, coal gangue powder also plays an important role in promoting combustion and gas generation in the formulation of this invention (the coal gangue powder used in this invention contains 8% residual carbon). If this component is removed, then: in the process step "e, firing", a higher firing temperature and a longer firing time are required, which increases energy consumption costs and will affect the reduction of bulk density and the increase of porosity, reducing the sintering pass rate (<70%). It is impossible to obtain qualified low thermal conductivity sintered ceramsite under the process system of this invention.

[0068] Comparative Example 5: This comparative example provides a type of ceramsite whose preparation process differs from that of Example 1 in that step "b. Preparation of rare earth modified light powder" is omitted. The raw materials are weighed according to the following weight percentages: 15% high-alumina polylight waste brick powder, 49% fly ash, 20% waste crucible powder, 15% coal gangue powder, 0% rare earth modified light powder, and 1% additives (0.5% each of rare earth lanthanum and cerium carbonate and silicon carbide). The raw materials are then uniformly mixed to obtain a mixed raw material.

[0069] The performance of the expanded clay prepared in this comparative example is as follows: bulk density 762 kg / m³ 3 It has a porosity of 29% and a thermal conductivity of 0.31 W / (m·K).

[0070] Increased bulk density (>750 kg / m³) 3 The porosity decreased (<30%), and the thermal conductivity increased [>0.3W / (m·K)], both exceeding the peak values ​​of the three indicators involved in this invention. Furthermore, the cylinder compressive strength decreased to a certain extent, making it impossible to obtain the high-adaptability, low-thermal-conductivity scald-expanding ceramic granules of this invention.

[0071] Comparative Example 6: This comparative example provides a type of ceramsite whose preparation process differs from that of Example 1 in that step "b, preparation of rare earth modified light powder" is omitted, and the rare earth modified light powder in step "c" is replaced with an equal mass percentage of rare earth lanthanum and cerium carbonate powder.

[0072] The performance of the ceramsite prepared in this comparative example is as follows: pelletizing qualification rate 86%, sintering qualification rate 77%, and cylinder compressive strength 4.8 MPa.

[0073] Based on the performance test results of this comparative example and Example 4, it can be seen that direct addition will reduce the product's pelletizing rate, sintering pass rate, and cylinder compressive strength.

[0074] It should be noted that, in this document, terms such as “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0075] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A low thermal conductivity sintering ceramsite based on rare earth modification and fly ash solid waste, characterized in that, The ceramsite is made from the following raw materials in parts by weight: 5-15 parts high-alumina lightweight waste brick powder, 40-60 parts fly ash, 10-20 parts waste crucible powder, 10-15 parts coal gangue powder, 5-9 parts rare earth modified lightweight powder, and 1-3 parts additives.

2. The low thermal conductivity sintering ceramsite based on rare earth modification and fly ash solid waste as described in claim 1, characterized in that, The rare earth modified light powder is prepared by wet co-milling of fly ash powder and lanthanum and cerium carbonate powder, spray granulation, and high-temperature sintering.

3. The low thermal conductivity sintering ceramsite based on rare earth modification and fly ash solid waste as described in claim 1, characterized in that, The added additives include rare earth lanthanum and cerium carbonate and silicon carbide.

4. The low thermal conductivity sintering ceramsite based on rare earth modification and fly ash solid waste as described in claim 1, characterized in that, Its performance meets the following requirements: bulk density ≤724 kg / m³, cylinder compressive strength ≥10 MPa, and thermal conductivity ≤0.25 W / (m·K).

5. A method for preparing low thermal conductivity sintering ceramsite based on rare earth modification and fly ash solid waste, as described in any one of claims 1 to 4, characterized in that, Includes the following steps: S1: Weigh each raw material according to the weight proportions described in claim 1, and uniformly mix the pretreated high-alumina lightweight waste brick powder, fly ash, waste crucible powder, coal gangue powder, rare earth modified lightweight powder, and additives to obtain mixed raw materials. S2: After adding water to the mixed raw materials, raw material balls with a particle size of 2-12 mm are formed; S3: The raw material balls are fired in a stepped heating process, with the highest firing temperature being 1160-1200℃. The highest temperature point is held for 1-2 hours. After firing, the material balls are cooled to room temperature to obtain the finished product of low thermal conductivity sintered ceramsite.

6. The preparation method according to claim 5, characterized in that, The pretreatment process in S1 specifically includes: drying, ball milling, and passing high-alumina lightweight waste brick powder, fly ash, waste crucible powder, and coal gangue powder separately, then passing them through a 200-mesh sieve with a residue of less than 5%, and packaging them for later use.

7. The preparation method according to claim 5, characterized in that, The preparation process of the rare earth modified calcite described in S1 specifically includes: Fly ash powder and lanthanum and cerium carbonate powder are co-ground in an aqueous phase containing a dispersant until the particle size is less than 1 μm to form a slurry; the slurry is spray-dried and granulated, and the resulting light powder is sintered at 1000℃-1100℃ to obtain rare earth modified light powder.

8. The preparation method according to claim 7, characterized in that, The mass ratio of fly ash powder to lanthanum and cerium carbonate powder is (92-98):(2-8); the pH value of the suspension is controlled at 8-10 during grinding; and the inlet temperature of spray granulation is 100℃-150℃.

9. The preparation method according to claim 5, characterized in that, In S2, raw material pellets are prepared using an automatic pelletizing machine, with the machine's rotation speed controlled within the range of 25–35 r / min.

10. The preparation method according to claim 5, characterized in that, The specific procedure for the stepped heating firing is as follows: The temperature is increased from room temperature to 200℃ in 1-2 hours and held for 1-2 hours; then increased from 200℃ to 900℃ in 2-3 hours and held for 0.5-1 hour; then increased from 900℃ to 1050℃ in 1-2 hours and held for 1-2 hours; and finally increased from 1050℃ to the highest temperature point of 1160-1200℃ in 0.5-1 hour and held for 1-2 hours at that temperature point.

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