Extruded ceramic and method of making same

Abstract

The present application relates to a kind of sintered ceramic and its preparation method.The sintered ceramic includes siliceous solid waste, iron solid waste, aluminum solid waste, magnesium solid waste and fluxing agent, and the mass ratio of the siliceous solid waste, iron solid waste, aluminum solid waste, magnesium solid waste and fluxing agent is 40-50:10-15:20-30:2-12:3-5.The present application proposes to use magnesite tailings to provide magnesium oxide, and by controlling the content of magnesium oxide to regulate the generation of spinel phase at high temperature, so that the ceramic foam has good effect, uniform pore structure, high content of high-strength mineral phase and good grain development, thereby preparing sintered ceramic with excellent mechanical properties, while having low density and low water absorption performance.This method of cooperatively using solid waste to prepare high-strength ceramic not only reduces the cost, but also promotes the efficient utilization of solid waste resources.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of solid waste treatment and resource utilization, and particularly relates to a sintered expanded ceramsite and a preparation method thereof. BACKGROUND

[0002] A large amount of industrial solid waste, such as red mud, tailings and the like, has brought huge pressure to society, economy and environment, and how to effectively dispose of the solid waste so as to make it develop in harmony with economy has become a big problem we are facing. From the aspects of physical and chemical properties, the solid waste is a potential renewable resource, which can be widely used in production of building materials and extraction of metals, so as to reduce pollution and cost, and relieve resource and environmental pressure. The ceramsite aggregate is used in large quantity in engineering application, and has a large potential for absorbing solid waste, so that it is good in prospect and market to use the solid waste such as red mud and tailings to replace the traditional natural mineral to prepare the ceramsite.

[0003] The ceramsite is mainly prepared from siliceous and aluminous raw materials, and is obtained after granulation and sintering / expansion at high temperature. The sintered expanded ceramsite has obvious expansion behavior in the sintering process, high internal porosity and low density, and has the advantages of light weight, heat preservation, sound insulation, waterproof and fire resistance, and low requirement on the properties of raw materials, so that it can absorb a large amount of industrial solid waste. Based on the above characteristics, the sintered expanded ceramsite can be widely used in the building and environmental protection industries. At present, the mechanical properties of the sintered expanded ceramsite are bottlenecked due to the porous internal structure, so that the sintered expanded ceramsite is often limited in practical application. Therefore, how to improve the mechanical properties of the sintered expanded ceramsite is very crucial to improve the application level. SUMMARY

[0004] The application provides a sintered expanded ceramsite with good mechanical properties and a preparation method thereof.

[0005] To achieve the above object, the application adopts the following technical scheme:

[0006] A sintered expanded ceramsite, which comprises siliceous solid waste, ferruginous solid waste, aluminous solid waste, magnesic solid waste and fluxing agent, and the mass ratio of the siliceous solid waste, the ferruginous solid waste, the aluminous solid waste, the magnesic solid waste and the fluxing agent is 40-50:10-15:20-30:2-12:3-5.

[0007] In the above scheme, the siliceous solid waste is copper tailings or quartz tailings.

[0008] In the above scheme, the ferruginous solid waste is red mud or steel slag.

[0009] In the above scheme, the aluminous solid waste is fly ash or kaolin.

[0010] In the scheme, the magnesium solid waste is magnesite tailings, and the content of MgO in the magnesite tailings is greater than 40wt%.

[0011] In the scheme, the fluxing agent is sodium silicate or sodium carbonate.

[0012] In the scheme, the main crystal phase of the sintered expanded ceramsite is spinel phase, hematite phase and quartz phase.

[0013] In the scheme, the spinel phase is magnesium-iron-aluminum composite spinel and iron spinel.

[0014] In the scheme, the chemical composition of the sintered expanded ceramsite, in terms of oxides, comprises SiO2: 45-57wt%, Al2O3: 17-22wt%, Fe2O3: 6-10wt%, MgO: 2-6wt%, Na2O+K2O+CaO: 5-13wt%, and impurity oxides: 4-5wt%. The impurity oxides are titanium oxide and the like.

[0015] The preparation method of the sintered expanded ceramsite comprises the following steps:

[0016] Each raw material is put into a ball mill tank for fully mixing to obtain a uniform mixture;

[0017] The mixture is then poured into a mold for compression molding;

[0018] The compression-molded sample is placed in a muffle furnace, first raised from 25℃ to 900℃, and then continuously raised to 1150-1200℃, and kept for 30-60min, and then cooled with the furnace to obtain the sintered expanded ceramsite.

[0019] The mechanism of the application is that by controlling the content of MgO to change the Mg / Al and Mg / Fe ratios, the spinel microcrystals are generated by the interaction of Al2O3 and Fe2O3 in the red mud at high temperature. After the addition of the magnesite tailings, the MgO can reduce the high-temperature liquid viscosity and broaden the sintering temperature, so that the pore structure is uniform, and the magnesium-iron-aluminum spinel microcrystals are generated, the granular spinel has a small size (1-5μm), has good high-temperature fluidity, can promote the uniform growth of pores and improve the integrity of the pore wall, so that the sintered expanded ceramsite with excellent mechanical properties and uniform pore structure is obtained, which is conducive to promoting the diversified utilization of the sintered expanded ceramsite.

[0020] Compared with the prior art, the application has the following beneficial effects:

[0021] (1) The application cooperatively utilizes fly ash, copper tailings, red mud and other solid wastes, explores the suitable raw material ratio of the fly ash, copper tailings and red mud for preparing the sintered expanded ceramsite, greatly improves the solid waste disposal rate, reduces the preparation cost, and has simple process, green environmental protection, good social and economic environmental protection benefits, and is conducive to promoting the diversified utilization of the sintered expanded ceramsite.

[0022] (2) The present application adopts a pressing forming method, the strength of the sintered expanded haydite is high, the water content is low, the energy consumption and the storage cost of the pre-drying process are reduced, the economic benefits are great, and the feasibility of preparing haydite from solid waste in situ is improved.

[0023] (3) The present application introduces magnesite tailings to control the generation of spinel microcrystals from the crystal phase of the haydite, thereby improving the mechanical properties of the haydite. At high temperatures, MgO can react with Fe2O3 and Al2O3 to generate spinel phase and promote the stable growth of the pores. The microparticulate spinel is beneficial to improve the stability and uniformity of the pores, and has a wider sintering temperature range, effectively improving the strength of the sintered expanded haydite.

[0024] (4) The sintered expanded haydite obtained by the present application has good internal pore wall integrity and high foaming degree, and has good pore structure and mechanical properties, which is beneficial to reduce the water absorption of the material and improve the durability of the material application.

[0025] (5) The present application uses magnesite tailings to provide magnesium oxide, greatly reducing the production and preparation cost, and the utilization rate of solid waste can reach 80%.

[0026] (6) The spinel phase generated in the present application is beneficial to the effective solidification of heavy metals in the mineral, and the waste residue and waste water generated in the experimental processing process do not need harmless treatment and meet the environmental safety requirements.

[0027] (7) The apparent density of the sintered expanded haydite prepared by the present application is 0.63-1.20 g / cm 3 , the compressive strength is 1.5-3.6 MPa, and the 1-hour water absorption is 0.32-0.89%. The specific strength (compressive strength / apparent density) in a certain range is obviously improved with the increase of the MgO content. The amorphous phase content of the samples with MgO contents of 0.65wt%, 2.03wt%, 3.95wt%, 5.96wt%, and 8.07wt% is 51.81%, 56.25%, 60.36%, 61.79%, and 59.86%, respectively. XRD shows that when the MgO content is less than 6%, the increase of the content can promote the formation of the high-temperature liquid phase of the haydite body, the diffraction peak intensity of the quartz phase gradually decreases, and the magnesium-iron-aluminum spinel phase is slightly enhanced. At the same time, the increase of the liquid phase can fill the crystal boundary and the pores, optimize the ratio of the crystal phase (such as spinel) and the glass phase, and enhance the structural uniformity. When the MgO content reaches 8%, the amorphous phase content decreases, and the diffraction peak of the quartz phase appears to be enhanced, indicating that excessive MgO content cannot promote the generation of the liquid phase. That is, the introduction of MgO should be within a proper range. Therefore, a reasonable amount can improve the ratio of the crystal phase and the liquid phase and the microstructure, further homogenize the pores, and maximize the strength of the haydite. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 XRD diffraction patterns of the expanded ceramsite of the examples and comparative examples of the present application.

[0029] 1-Quartz-PDF # 46-1045;

[0030] 2-Hematite-PDF # 33-0664;

[0031] 3-Mg-Fe-Al Spinel-PDF # 21-0540;

[0032] 4-Hercynite-PDF # 82-0583. DETAILED DESCRIPTION

[0033] In order to make the objectives, technical solutions and advantages of the present application clearer, the present application will be further described in detail below in conjunction with examples. It should be understood that the specific examples described herein are only used to explain the present application and are not used to limit the present application.

[0034] In the following examples, magnesia is provided by using magnesite tailings, and the mass fraction of magnesia is set to 2-6wt%.

[0035] In the following examples, the copper tailings used are bulk solid waste generated in the mine. In the present application, the SiO2 content of the copper tailings is 71.05wt%, and the Al2O3 content is 11.92wt%.

[0036] In the following examples, the waste residue and waste water generated during the experimental processing process do not need to be harmlessly treated and meet the environmental safety requirements, and can be directly discharged or stored.

[0037] In the following examples, the particle size of the copper tailings, fly ash and red mud is below 100 mesh, and the chemical components are shown in Table 1. It should be understood that the specific raw material composition described herein is only used to explain the present application and is not used to limit the present application. Various changes (including raw material origin) can be made within the scope of the present application.

[0038] Table 1 Main chemical components of raw materials (wt. %)

[0039]

[0040] Example 1

[0041] The present example provides a preparation method of expanded ceramsite, comprising the following steps:

[0042] (1) copper tailings, red mud, fly ash, magnesite tailings and fluxing agent were weighed according to the mass ratio of 48:15:29:3:5, then put into a mixer to stir for 10-15 minutes and dry to obtain a mixed material with uniform mixture; the chemical composition of the mixed material is: SiO2: 55.28%, Al2O3: 19.90%, Fe2O3: 8.88%, CaO: 2.21%, MgO: 2.03%, K2O: 3.05%, Na2O: 3.99%, and other: 4.66%.

[0043] (2) the mixed material was made into a cylindrical sample of φ20mm by dry pressing method;

[0044] (3) the cylindrical sample was placed in a sintering furnace, first increased from 25°C to 900°C at 10°C / min, kept for 10 min, then continued to increase to 1180°C at 10°C / min, kept for 60 min and cooled with the furnace to obtain the sintered ceramsite.

[0045] The apparent density thereof is 0.77 g / cm 3 , the compressive strength is 2.73 MPa, the specific strength (compressive strength / apparent density) is 3.58, the 1h water absorption is 0.28%, the sample pore size distribution is 0.8-2mm, the pore size distribution standard deviation (SD) is 0.19, and the average pore size is 1.15mm.

[0046] At this time, the main crystalline phase in the matrix is quartz and iron oxide phase, and there is a small amount of granular spinel microcrystalline, the pore density is large, and the open porosity is high.

[0047] Example 2

[0048] This example is basically the same as Example 1, except that step (1) is:

[0049] (1) copper tailings, red mud, fly ash, magnesite tailings and fluxing agent were weighed according to the mass ratio of 48:15:29:3:5, then put into a mixer to stir for 10-15 minutes and dry to obtain a mixed material with uniform mixture; the chemical composition of the mixed material is: SiO2: 55.28%, Al2O3: 19.90%, Fe2O3: 8.88%, CaO: 2.21%, MgO: 2.03%, K2O: 3.05%, Na2O: 3.99%, and other: 4.66%.

[0050] The apparent density of the sintered ceramsite obtained is 0.71 g / cm 3 , the compressive strength is 2.56 MPa. The specific strength is 3.62, the 1h water absorption is 0.37%, the sample pore size distribution is 0.6-2mm, the pore size distribution standard deviation (SD) is 0.17, and the average pore size is 1.08mm.

[0051] Compared with Example 1, the MgO content is increased to 3.95wt%, the specific strength is increased by 1.12%, and the pore size standard deviation is reduced by 10.53%.

[0052] The quartz and iron oxide diffraction peaks in the matrix are obviously reduced, and more magnesium iron aluminum spinel phases appear. When the quartz is converted into spinel crystals, Si 4+ into the glass phase, the polymerization degree of Si-O ion in the alkali-rich melt is increased, and the melt viscosity is increased. The increase in viscosity is beneficial to the uniform distribution of small pores generated in the foaming stage in the matrix, which significantly improves the foaming effect, makes the pore size distribution uniform, and improves the integrity of the pore wall.

[0053] Example 3

[0054] This example is basically the same as Example 1, except that step (1) is different:

[0055] (1) The copper tailings, red mud, fly ash, magnesite tailings and fluxing agent are weighed according to a mass ratio of 45:15:24:11:5, and then put into a mixer for stirring for 10 minutes to obtain a uniformly mixed mixture; the chemical composition of the uniformly mixed mixture is: SiO2: 52.60%, Al2O3: 18.56%, Fe2O3: 9.04%, CaO: 2.12%, MgO: 5.96%, K2O: 2.95%, Na2O: 4.03%, and other: 4.74%.

[0056] The apparent density of the sintered ceramsite obtained is 0.63g / cm 3 , the compressive strength is 2.29MPa, the specific strength is 3.63, the 1h water absorption is 0.46%, the pore size distribution of the sample is 0.5-1.7mm, the pore size distribution standard deviation (SD) is 0.16, and the average pore size is 0.97mm.

[0057] Compared with Example 1, the MgO is increased to 5.96wt%, the specific strength is increased by 0.28%, and the pore size standard deviation is reduced by 5.88%.

[0058] At this time, the matrix crystal phase is basically quartz and magnesium iron aluminum spinel phase, and the magnesium iron aluminum spinel microcrystals are uniformly dispersed in the melt and liquid-gas phase interface, which reduces the liquid-gas phase contact area and pore nucleation energy, and forms a large number of uniformly distributed small pores, so that the pore structure and the integrity of the pore wall are improved. The improvement of the integrity of the pore wall not only improves the compressive strength of the sintered ceramsite, but also is beneficial to reducing the water absorption of the material and improving the frost resistance of the material.

[0059] Comparative Example 1

[0060] This comparative example is basically the same as Example 1, except that step (1) is different:

[0061] (1) copper tailings, red mud, fly ash, magnesite tailings and fluxing agent were weighed according to the mass ratio of 43:15:22:15:5, then put into a mixer and stirred for 10 minutes to obtain dry mixture with uniform mixing; the chemical composition of the raw material was: SiO2: 51.07%, Al2O3: 17.97%, Fe2O3: 9.12%, CaO: 2.07%, MgO: 8.07%, K2O: 2.87%, Na2O: 4.05%, and other: 4.78%.

[0062] The apparent density of the sintered ceramsite obtained was 0.66 g / cm3, the compressive strength was 1.91 MPa, the specific strength was 2.89, and the 1h water absorption was 0.63%. The pore size distribution of the sample was 0.5-2.3 mm, the pore size distribution standard deviation (SD) was 0.28, and the average pore size was 1.49 mm. 3

[0063] Compared with Example 1, the MgO content increased to 8.07 wt%, and the specific strength decreased by 20.39%. At this time, the main crystal phase in the matrix was still quartz and spinel phase, but the pore distribution of the sample was uneven (the pore size difference increased), which caused the strength to decrease. At the same time, the excess MgO may not be able to fully participate in the spinel reaction, and is easy to precipitate in the form of periclase, which makes the pore structure uniformity of the material worse and the mechanical properties decrease.

[0064] Comparative Example 2

[0065] This comparative example was substantially the same as Example 1, except that step (1) was:

[0066] (1) copper tailings, red mud, fly ash, magnesite tailings and fluxing agent were weighed according to the mass ratio of 43:15:22:15:5, then put into a mixer and stirred for 10 minutes to obtain dry mixture with uniform mixing; the chemical composition of the raw material was: SiO2: 51.07%, Al2O3: 17.97%, Fe2O3: 9.12%, CaO: 2.07%, MgO: 8.07%, K2O: 2.87%, Na2O: 4.05%, and other: 4.78%.

[0067] The apparent density of the sintered ceramsite obtained was 0.66 g / cm3, the compressive strength was 1.91 MPa, the specific strength was 2.89, and the 1h water absorption was 0.63%. The pore size distribution of the sample was 0.5-2.3 mm, the pore size distribution standard deviation (SD) was 0.28, and the average pore size was 1.49 mm.

[0068] When the magnesium oxide content was 0.65 wt%, the crystal phase in the sample contained a large amount of quartz and iron oxide phase. Studies have shown that during the growth of the pore expansion, too much quartz and iron oxide phase will significantly increase the liquid phase viscosity, hinder the growth of the pore, and make the pore size uniformity of the sample decrease, and the open porosity is very high.​

[0069] Table 2

[0070]

[0071] The above embodiments are merely examples for clearly illustrating the present application, and are not intended to limit the embodiments. Based on the above description, those skilled in the art can further make other different forms of changes or modifications without departing from the spirit of the present application, and the changes or modifications are also within the scope of the present application.

Claims

1. A kind of expanded ceramsite, characterized in that: The intumescent ceramsite comprises siliceous solid waste, ferrous solid waste, aluminum solid waste, magnesium solid waste and flux, and the mass ratio of the siliceous solid waste, ferrous solid waste, aluminum solid waste, magnesium solid waste and flux is: 40~50:10~15:20~30:2~12:3~5, the siliceous solid waste is copper tailings, the ferrous solid waste is red mud, the aluminum solid waste is fly ash, and the magnesium solid waste is magnesite tailings. The MgO content in the magnesite tailings is greater than 40wt%. The chemical composition of the intumescent ceramsite, calculated as oxides, comprises SiO2: 45~57wt%, Al2O3: 17~22wt%, Fe2O3: 6~10wt%, MgO: 2~6wt%, Na2O+K2O+CaO: 5~13wt%, and impurity oxides: 4~5wt%.

2. The expanded ceramsite according to claim 1, wherein The flux is sodium silicate or sodium carbonate.

3. The expanded ceramsite according to claim 1, wherein The main crystal phases of the expanded ceramsite are spinel phase, hematite phase and quartz phase.

4. The expanded ceramsite according to claim 3, wherein The spinel phase is magnesium-iron-aluminum composite spinel and iron spinel.

5. The method for preparing the expanded ceramsite according to any one of claims 1 to 4, wherein: The steps include: Put all raw materials into a ball mill and mix them thoroughly to obtain a uniform mixture; Then pour the mixture into the mold and press it into shape; The pressed sample was placed in a muffle furnace, first raised from 25°C to 900°C, kept warm for 5-15 minutes, then continued to rise to 1150-1200°C, kept warm for 30-60 minutes, and then cooled with the furnace to obtain the sintered ceramsite.

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