Foamed ceramic prepared by using calcium and magnesium rich molybdenum tailings and preparation method thereof

Abstract

The application discloses a kind of foamed ceramics prepared by calcium-rich magnesium molybdenum tailings and preparation method, and raw materials are composed of base material and foaming agent, wherein, base material is as follows according to mass percentage: molybdenum tailings 50-70%, fly ash 15-25%, kaolin 10-25%, silicon tailings 5-15%, and aluminum oxide 2-8%; The mass of the foaming agent is 0.4-1.0% of the mass of the base material; The foamed ceramics provided by the application is based on Si-Al-Mg-Ca component system, not only realizes high utilization rate of molybdenum tailings, but also makes full use of other solid waste materials in the region, further improves the utilization rate of solid waste materials in foamed ceramics, and the utilization rate of molybdenum tailings in the application is not less than 50%, and the proportion of all solid waste materials is not less than 70%, and the foamed ceramics has uniform and dense pore structure.

Description

Technical Field

[0001] This invention relates to a foamed ceramic prepared using calcium-magnesium-molybdenum tailings and its preparation method, belonging to the field of comprehensive utilization technology of industrial waste. Background Technology

[0002] Molybdenum ore flotation processes produce tailings, which comprise over 95% of the total ore volume. Long-term stockpiling of these tailings not only occupies land but also poses environmental hazards. Foamed ceramic materials, possessing lightweight, high strength, thermal insulation, and fire resistance properties, have become a key area for development in new building materials. Utilizing molybdenum tailings to produce high-value-added foamed ceramic materials represents a significant strategy that balances large-scale disposal of molybdenum tailings with the high-value production of finished products. However, existing foamed ceramic formulations primarily use a Si-Al-Na(K) composition system. While silica-alumina raw materials such as silica tailings, high-alumina fly ash, and ceramic polishing waste can be fully utilized, the utilization rate of calcium- and magnesium-rich molybdenum tailings is low under the traditional Si-Al-Na(K) composition system. Improving the utilization rate of calcium- and magnesium-rich molybdenum tailings under a novel foamed ceramic composition system, and breaking the application limitations of the traditional Si-Al-Na(K) ternary system for calcium- and magnesium-rich molybdenum tailings (and other similar solid wastes), is a key technology with both environmental and economic benefits and practical value. Summary of the Invention

[0003] Addressing the technical challenge of low utilization rates of calcium- and magnesium-rich molybdenum tailings in Si-Al-Na(K) foamed ceramics, the first objective of this invention is to provide a foamed ceramic prepared using calcium- and magnesium-rich molybdenum tailings. This foamed ceramic, based on a Si-Al-Mg-Ca component system, not only achieves high utilization of molybdenum tailings but also fully utilizes other solid waste materials from the region, further improving the utilization rate of solid waste materials in the foamed ceramic. In this invention, the utilization rate of molybdenum tailings is no less than 50%, the proportion of total solid waste materials is no less than 70%, and the prepared foamed ceramic has a bulk density of 400-600 kg / m³. 3 It has a compressive strength of not less than 5.0 MPa, a thermal conductivity of 0.20-0.35 W / (m·K), and a uniform pore structure.

[0004] The second objective of this invention is to provide a method for preparing foamed ceramics using calcium-, magnesium-, and molybdenum-rich tailings.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] This invention discloses a foamed ceramic prepared using calcium-magnesium-molybdenum tailings. The raw materials consist of a base material and a foaming agent. The base material, by mass percentage, comprises: 50-70% molybdenum tailings, 15-25% fly ash, 10-25% kaolin, 5-15% silica tailings, and 2-8% alumina. The foaming agent comprises 0.4-1.0% of the base material mass. The molybdenum tailings, by mass percentage, have the following main chemical composition: 48-55% SiO2, 12-18% MgO, 8-13% CaO, 5-10% Al2O3, 4-8% Fe2O3, and 3-6% K2O.

[0007] Traditional foamed ceramic raw materials are mainly composed of silicon, aluminum, and sodium (or potassium), belonging to the Si-Al-Na(K) component system. Calcium, magnesium, and iron, along with potassium and sodium, belong to flux-type components. The role of flux components is to regulate the melting temperature and high-temperature liquid phase viscosity of the foamed ceramic body, so the content of flux components should not be too high. However, the main characteristic of high-calcium and high-magnesium molybdenum tailings is that they contain a high amount of calcium and magnesium elements, which cannot be used in large quantities in the Si-Al-Na(K) component system. The dosage is often no more than 10%, which greatly limits the application of high-calcium and high-magnesium solid waste raw materials in the field of foamed ceramics.

[0008] This invention cleverly utilizes the high calcium and high magnesium characteristics of high-calcium and high-magnesium molybdenum tailings, and improves the utilization rate of high-calcium and high-magnesium molybdenum tailings by constructing a Si-Al-Mg-Ca quaternary component system. Moreover, the auxiliary raw materials selected are mostly common solid waste raw materials, such as fly ash and silicon tailings, which can reduce the cost of raw materials while achieving the goal of multi-solid waste synergy.

[0009] However, for foamed ceramics to be successfully prepared, the melting and softening temperature of the green body and the foaming temperature of the foaming agent must be consistent. The raw materials and sintering process must be coordinated to form a suitable amount and viscosity of liquid phase for foaming. If the amount of liquid phase is too small or the viscosity is too low, foaming will not be possible. If the amount of liquid phase is too large or the viscosity is too low, the generated pores will be large and irregular. Only when the pores have a uniform and dense appearance can the basic performance be guaranteed. However, the molybdenum tailings with high calcium and magnesium content selected in this invention have a high calcium, magnesium and iron content (total close to 40%). The use of large quantities of these materials will significantly reduce the melting and softening temperature and high-temperature liquid phase viscosity of the green body, resulting in excessive pore growth, pore aggregation and deterioration. Therefore, the utilization rate of this type of raw material in the traditional quartz-kaolin-potassium (sodium) feldspar, that is, Si-Al-Na(K) component system, is often no more than 10%, and it is difficult to exceed 30% at most. Based on the characteristics of raw materials, this invention constructs a Si-Al-Mg-Ca component system by introducing common siliceous and aluminous raw materials, significantly improving the utilization rate of molybdenum tailings (over 50%). The SiO2 and Al2O3 components in the raw materials melt at high temperatures to form a glassy aluminosilicate network structure, which is the main source of strength in the foamed ceramic. The MgO and CaO components in the molybdenum tailings act as fluxes during sintering, which helps to lower the melting temperature of the green body, increase the amount of sintering liquid phase generated, and reduce the viscosity of the high-temperature liquid phase, thus promoting the foaming process. On the other hand, the MgO and CaO components, as network modifiers, can improve the pore structure through a synergistic mechanism. MgO increases the surface tension of bubbles, inhibiting pore growth and coalescence, effectively compensating for the potential pore structure deterioration caused by excessive CaO content. Furthermore, the Si-Al-Mg-Ca foamed ceramic component system constructed based on molybdenum tailings in this invention has quartz and anorthite as its main crystalline phases, with columnar anorthite dispersed in the glassy phase, which is beneficial for improving the strength of the foamed ceramic.

[0010] The preferred formulation has the following composition by mass percentage: 50-60% molybdenum tailings, 15-25% fly ash, 12-25% kaolin, 5-15% silicon tailings, and 2-3% alumina.

[0011] In a further preferred embodiment, the base material comprises the following components by mass percentage: 50-55% molybdenum tailings, 20-25% fly ash, 12-25% kaolin, 8-15% silicon tailings, and 2-3% alumina.

[0012] In this invention, in order to make full use of high-calcium, magnesium, and molybdenum tailings, molybdenum tailings are used as the matrix material, with a basic proportion of not less than 50%, to provide the main silicon source and form the network structure of the glass phase of the foamed ceramic; they also provide the main flux components to adjust the liquid phase properties during firing and affect the firing temperature. Of course, as the molybdenum tailings content increases, the content of Ca, Mg, and Fe in the green body also increases. These flux components will lower the melting and softening temperature of the green body, causing the pores to grow drastically at the same temperature. Therefore, they cannot be added in excess. If they exceed 70%, it will cause the pore structure to deteriorate, leading to a drastic decrease in the corresponding performance. By controlling the proportion within the above-mentioned preferred range, the final foamed ceramic will have the best performance.

[0013] In a preferred embodiment, the particle size of the molybdenum tailings is ≤74μm.

[0014] In a preferred embodiment, the kaolin, by mass percentage, has the following main chemical composition: SiO2 48-52%, Al2O3 44-48%. The kaolin provides aluminum components, thus contributing plasticity and strength to the foamed ceramic, broadening the sintering range. Increased kaolin content inhibits foaming and stabilizes bubble morphology, thereby improving the strength of the foamed ceramic.

[0015] Further preferred, the kaolin has a particle size ≤74μm.

[0016] In a preferred embodiment, the fly ash, by mass percentage, has the following main chemical composition: SiO2 35-45%, Al2O3 27-40%, CaO 1-5%, Fe2O3 1-6%, and MgO 0-3%. Fly ash replenishes silicon and aluminum components, lowers the melting temperature of the green body, further reduces the cost of foamed ceramic preparation, and improves the utilization rate of solid waste.

[0017] Further preferred, the fly ash has a particle size ≤74μm.

[0018] In a preferred embodiment, the silicon tailings, by mass percentage, have the following main chemical composition: SiO2 80-85%, Al2O3 2-5%, CaO 1-3%. Supplementing the silicon component with an appropriate amount of silicon tailings helps to improve strength.

[0019] Further preferred, the particle size of the silicon tailings is ≤74μm.

[0020] In a preferred embodiment, the foaming agent is industrial silicon carbide with a particle size ≤10μm.

[0021] In a preferred embodiment, the foamed ceramic has the following composition by mass percentage: SiO2 48-53%, Al2O3 16-24%, MgO 8-14%, CaO 6-12%, Fe2O3 0-6%, (K2O+Na2O) 0-3%.

[0022] The inventors discovered that by controlling the proportions of raw materials, the foamed ceramic can ultimately be a Si-Al-Mg-Ca component system within the aforementioned composition range, resulting in the foamed ceramic with optimal performance.

[0023] This invention discloses a method for preparing foamed ceramics using calcium-magnesium-molybdenum-rich tailings. The method involves mixing base material and foaming agent according to a designed ratio, wet ball milling and drying the base material and foaming agent to obtain a mixture, crushing the mixture to obtain powder, forming a blank, and sintering the blank to obtain the foamed ceramic.

[0024] The preferred method is to first dry the base material and foaming agent at 40-60℃.

[0025] In a preferred embodiment, during wet ball milling, the milling medium is water, wherein the mass ratio of the base material and foaming agent to water is 1:1-1.2.

[0026] In a preferred embodiment, the wet ball milling time is 20-30 minutes.

[0027] In a preferred embodiment, the molding method is either stacking molding or dry pressing molding.

[0028] Further preferred, the piling and molding process involves evenly spreading the powder to fill the mold and then compacting it.

[0029] Further preferably, the dry pressing process involves spraying 6-8% water or polyethylene glycol into the powder, aging it for 16-24 hours, and then pressing it into shape using a mold.

[0030] In a preferred embodiment, the sintering temperature is 1050-1200℃, preferably 1100-1150℃, and the sintering time is 20-40 minutes. Through the synergistic effect of the raw material formulation and the above-described sintering process, the foamed ceramics produced by this invention possess a uniform and dense pore structure and exhibit excellent performance.

[0031] In a further preferred embodiment, during sintering: the temperature is first increased to 850-950℃ at a heating rate of 8-12℃ / min, and then increased to the final temperature at a heating rate of 3-6℃ / min.

[0032] The foamed ceramic with the above heating rate has the best performance.

[0033] In practice, the foamed ceramic products will eventually be cut and polished to a certain size to meet the relevant performance testing and usage requirements.

[0034] Principles and advantages

[0035] According to the raw material ratio proposed in this invention, a suitable high-temperature liquid phase is formed in the green body at the corresponding sintering temperature. Simultaneously, the foaming agent decomposes within the same temperature range to form bubbles and overcome the resistance of the liquid phase to grow. After cooling, a foamed ceramic with a three-dimensional, independently closed-pore structure is formed, possessing lightweight, heat insulation, and a certain strength. The mechanism lies in the fact that the SiO2 and Al2O3 components in the raw materials melt at high temperatures to form a glassy aluminosilicate network framework, which is the main source of the glassy phase skeleton structure and strength of the foamed ceramic. The MgO and CaO components in the molybdenum tailings act as fluxes during sintering, which helps to lower the green body melting temperature, increase the amount of sintered liquid phase generated, and reduce the viscosity of the high-temperature liquid phase, thus promoting the foaming process. On the other hand, MgO and CaO components are both network modifiers, which can improve the pore structure through a synergistic mechanism. This is reflected in MgO increasing the surface tension of bubbles, which can inhibit pore growth and coalescence, effectively compensating for the potential pore structure deterioration caused by excessive CaO content. This invention relates to a Si-Al-Mg-Ca foamed ceramic component system constructed based on molybdenum tailings. Its main crystalline phases are quartz and anorthite, with columnar anorthite dispersed in the glass phase, which is beneficial to improving the strength of the foamed ceramic.

[0036] Compared with the prior art, the advantages of the present invention are:

[0037] (1) It effectively improves the utilization rate of calcium-rich, magnesium-molybdenum-rich tailings in foamed ceramic products, with a utilization rate of no less than 50%.

[0038] (2) In conjunction with other common solid wastes in the region, the utilization rate of solid waste materials in foamed ceramics has been further improved, with solid waste accounting for no less than 70% of the raw material usage.

[0039] (3) Within a relatively wide range of composition and firing temperature, foamed ceramics exhibit superior performance, with a bulk density of 400-600 kg / m³. 3 The compressive strength is greater than 5.0 MPa, the volume water absorption rate is not higher than 2.0%, and the thermal conductivity is not higher than 0.35 W / (m·K).

[0040] (4) The auxiliary raw materials are widely available, with few restrictions and low material costs.

[0041] (5) The preparation method is simple. Attached Figure Description

[0042] Figure 1 Physical image and scanning electron microscope image of the porous ceramic prepared in Example 3. Figure 1 (a) is a photograph of the porous ceramic prepared in Example 3. It can be seen that the porous ceramic has a uniform pore structure. Figure 1 (b) Figure 1 (c) are scanning electron microscope (SEM) images at different magnifications. The SEM images show columnar anorthite crystals distributed within the glass phase.

[0043] Figure 2 Comparative Example 4 and Comparative Example 5: actual object images. Figure 2 (a) is a physical image of Comparative Example 4, showing that the excessive use of fly ash led to deterioration of the pore structure. Figure 2 (b) is a physical image of Comparative Example 5, showing that insufficient molybdenum tailings resulted in inadequate foaming. Detailed Implementation

[0044] The origins and main components of the raw materials used in the following examples are shown in Table 1. All materials have a particle size ≤74μm. The formulations for Examples 1-6 are shown in Table 2.

[0045] Among them: the difference between Example 1 and Example 2 is the amount of foaming agent; the difference between Example 1 and Example 3 is the ratio of fly ash to kaolin; the difference between Example 4 and Example 5 is the sintering temperature; the difference between Example 4 and Example 6 is the ratio of molybdenum tailings to silicon tailings.

[0046] Table 1 Main Raw Materials of Examples

[0047]

[0048] Table 2 Raw material ratios and sintering regimes of the examples

[0049]

[0050] The preparation methods for Examples 1-6 are as follows:

[0051] (1) Weigh the pre-dried materials according to the weight ratios in Table 2, wherein, by mass percentage, the base material totals 100%, and SiC accounts for 0.4-1.0% of the base material mass.

[0052] Transfer the material and water in a 1:1 ratio into the ball mill and mill for 30 minutes.

[0053] (2) Remove the slurry from the ball mill, filter it, then dry the filter cake, crush it into powder, and pass it through a 200-mesh sieve for later use.

[0054] (3) Spread the billet evenly in the refractory mold and vibrate it to compact it.

[0055] (4) Transfer the billet along with the refractory mold into the high-temperature furnace. The heating process is set as follows: heat up to 900℃ at 10℃ / min, then heat up to the endpoint temperature set in Table 2 at 5℃ / min, then hold at the endpoint temperature for 30 minutes, and then cool to room temperature.

[0056] (5) The sample is machined to the required dimensions according to the subsequent testing requirements.

[0057] The results of the basic physical properties test of the samples obtained in the examples are shown in Table 3. Among them, the bulk density, compressive strength, and volume water absorption rate are in accordance with GB / T 1966—1996 "Test Methods for Properties of Porous Ceramics", the mechanical properties are in accordance with GB / T 1964-1996 "Test Method for Compressive Strength of Porous Ceramics", and the thermal conductivity is in accordance with GB / T 5990-2006 "Test Method for Thermal Conductivity of Refractory Materials (Hot Wire Method)".

[0058] Table 3. Sample test results of the embodiments

[0059]

[0060] The preparation method for the comparative example is the same as that for the example. The raw material ratio and sintering regime for the comparative example are shown in Table 4, and the test results are shown in Table 5.

[0061] Table 4 Comparative Example Raw Material Proportions and Sintering Regime

[0062]

[0063] Table 5. Test results of comparative samples

[0064]

[0065]

Claims

1. A method for preparing foamed ceramics using calcium-magnesium-molybdenum-rich tailings, characterized in that: The base material and foaming agent are prepared according to the design ratio. The base material and foaming agent are wet ball milled and dried to obtain a mixture. The powder obtained after crushing the mixture is shaped into a blank. The blank is sintered to obtain foamed ceramic. The sintering process is as follows: first, the temperature is increased to 850-950℃ at a heating rate of 8-12℃ / min, then the temperature is increased to 1100-1150℃ at a heating rate of 3-6℃ / min, and held for 20-40 minutes. The foamed ceramic is composed of a base material and a foaming agent. The base material, by mass percentage, consists of: 50-60% molybdenum tailings, 15-25% fly ash, 12-25% kaolin, 5-15% silica tailings, and 2-3% alumina. The foaming agent is 0.4-1.0% of the base material mass. The molybdenum tailings, by mass percentage, have the following main chemical composition: 48-55% SiO2, 12-18% MgO, 8-13% CaO, 5-10% Al2O3, 4-8% Fe2O3, and 3-6% K2O.

2. The method for preparing foamed ceramics using calcium-magnesium-molybdenum-rich tailings according to claim 1, characterized in that: First, dry the base material and foaming agent at 40-60℃; During the wet ball milling, the milling medium is water, and the mass ratio of the base material and foaming agent to water is 1:1-1.2; the wet ball milling time is 20-30 minutes.

3. The method for preparing foamed ceramics using calcium-magnesium-molybdenum-rich tailings according to claim 1, characterized in that: The molding method is either stacking molding or dry pressing molding; The piling and molding process involves evenly spreading and filling the mold with powder and then compacting it. The dry pressing process involves spraying 6-8% water or polyethylene glycol into the powder, aging it for 16-24 hours, and then pressing it into shape using a mold.

4. A method for preparing foamed ceramics using calcium-magnesium-molybdenum-rich tailings according to any one of claims 1-3, characterized in that: The particle size of the molybdenum tailings is ≤74 μm; The kaolin, by mass percentage, has the following main chemical composition: SiO2 48-52%, Al2O3 44-48%; The particle size of the kaolin is ≤74 μm; The fly ash, by mass percentage, has the following main chemical composition: SiO2 35-45%, Al2O3 27-40%, CaO 1-5%, Fe2O3 1-6%, MgO 0-3%; The particle size of the fly ash is ≤74 μm; The silicon tailings, by mass percentage, have the following main chemical composition: SiO2 80-85%, Al2O3 2-5%, CaO 1-3%; The particle size of the silicon tailings is ≤74 μm; The foaming agent is industrial silicon carbide with a particle size ≤10μm.

Images