Ceramsite preparation method and ceramsite

Abstract

The invention discloses a ceramsite preparation method and ceramsite, the method comprises the following steps: (1) pretreatment: bauxite tailings and fly ash are crushed and sieved to respectively obtain bauxite tailing powder and fly ash powder; (2) mixing: uniformly mixing the bauxite tailing powder, the fly ash powder, starch and bentonite to obtain a material mixture; (3) forming: adding water to wet the material mixture, and granulating to obtain raw material balls; (4) drying: drying the raw material nodules to obtain dry raw material nodules; and (5) preheating and roasting: preheating the dry raw material nodules, and roasting to obtain the ceramsite. According to the invention, bauxite tailings and fly ash are used as main raw materials for firing ceramsite, which is an effective way for recycling two solid wastes, namely bauxite tailings and fly ash, and appropriate chemical components of the raw materials, proportions of the raw materials, preheating temperature, roasting temperature and other factors are selected, so that a ceramic shell is formed, the surface is smooth, and the vitrification effect is good; the size is expanded, and the appearance is complete.

Description

Technical Field

[0001] The present invention relates to the technical field of chemical industry, and in particular to a preparation method of ceramsite and the ceramsite. Background Art

[0002] Ceramic particles are a type of lightweight aggregate that expands significantly after high-temperature firing, becoming spherical in shape. They have a smooth, hard surface, a ceramic shell that traps moisture and retains gas, and a closed, microporous interior. Their color depends on the firing process and materials used; most are dark red or ochre-red, while other specialized varieties can appear grayish-yellow, off-white, or grayish-black. Depending on the raw material, ceramsite can be categorized as bauxite, clay, garbage, sludge, and fly ash. Its water-repellent, gas-retaining shell and its closed, fine, and meticulously cellular structure provide excellent resistance to pressure, shock, alkali, heat, and cold, along with numerous advantages such as light weight, low density, high porosity, and low water absorption. Because of its many excellent properties, it is used in many industries, such as as a petroleum proppant in the oil industry, as a greening material in the garden industry, as a biofilter biofilm carrier in the environmental protection industry, as pipeline insulation, replacing natural river sand in the building materials industry, and as a soilless cultivation mechanism in agriculture.

[0003] With the rapid expansion of the aluminum industry, bauxite mining is also increasing. Bauxite is primarily mined through open-pit mining, and the resulting tailings are mostly stored in the open. In addition to occupying land resources, long-term storage can kill plants, affect the physical and chemical properties of the soil, and damage the land's ability to grow crops. The hazards of bauxite mining cannot be underestimated. Fly ash, a solid waste formed by the combustion of fuel (primarily coal), is composed primarily of tiny particles of ash. It primarily comes from the coal-fired power and heating industries. With the systematization, automation, and mechanization of industrial and agricultural production, the increasing popularity of new energy vehicles, the widespread use of electronic products, and the increasing demand for higher quality of life, the power industry's power generation capacity has continued to grow, leading to record highs in fly ash emissions.

[0004] In the early days, clay was the primary raw material for ceramsite firing. However, with the decline of land resources, changes in national policies, and the continuous increase in the total amount of solid waste, the development and utilization of solid waste for ceramsite firing has become a trend. Bauxite tailings and fly ash, due to their similar physical and chemical properties to clay, are very suitable as raw materials for ceramsite firing. Therefore, it is crucial to fully utilize solid wastes such as bauxite tailings and fly ash and use them rationally to produce high-quality ceramsite. Summary of the Invention

[0005] The purpose of the present invention is to overcome the defects of the prior art and provide a method for preparing ceramsite.

[0006] In order to solve the above technical problems, the purpose of the present invention is achieved through the following technical solutions:

[0007] A method for preparing ceramsite comprises the following steps:

[0008] (1) Pretreatment: crushing and sieving the bauxite tailings and fly ash to obtain bauxite tailings powder and fly ash powder respectively;

[0009] (2) Mixing: uniformly mixing bauxite tailings powder, fly ash powder, starch, and bentonite to obtain a material mixture;

[0010] (3) Molding: adding water to moisten the material mixture and granulating to obtain raw material balls;

[0011] (4) Drying: Drying the raw balls to obtain dry raw balls;

[0012] (5) Preheating and roasting: After preheating the dry raw material balls, roasting them to obtain the ceramsite.

[0013] Preferably, in step (1), the bauxite tailings and fly ash are crushed and passed through a 100-mesh sieve to obtain bauxite tailings powder and fly ash powder, respectively.

[0014] Preferably, in step (2), 20% of bauxite tailings powder, 20% of fly ash powder, 10% of starch, and 50% of bentonite are mixed uniformly by mass percentage to obtain a material mixture.

[0015] Preferably, in step (3), the particle size of the raw balls is 5 mm.

[0016] Preferably, in step (4), the drying temperature is 105° C. and the drying time is 2 h.

[0017] Preferably, in step (5), the dry raw balls are placed in an electric boiler for preheating at a temperature of 750° C. for 15 minutes.

[0018] Preferably, in step (5), the calcination temperature is 1100-1150° C., and the calcination time is 30 minutes.

[0019] Preferably, in step (5), the calcination temperature is 1150° C. and the calcination time is 30 min.

[0020] As an advantage, further comprising the steps of:

[0021] (6) Screening: After roasting is completed, use the water density method to screen and select the products with a density less than 1g / cm 3 The ceramsite is used as the finished ceramsite product.

[0022] The present invention also provides ceramsite prepared by the above-mentioned preparation method of ceramsite.

[0023] The beneficial effects of the present invention compared with the prior art are:

[0024] The present invention uses bauxite tailings and fly ash as primary raw materials to produce ceramsite, an effective way to recycle these two major solid wastes. Furthermore, the present invention selects appropriate raw material chemical compositions, raw material ratios, preheating temperatures, calcination temperatures, and other factors to produce ceramsite with a smooth ceramic shell, good vitrification, and a well-defined appearance. The present invention rationally utilizes both bauxite tailings and fly ash, two major solid wastes, to achieve the goal of treating waste with waste. The fired ceramsite exhibits a good degree of vitrification and a smooth surface. The present invention significantly increases the combined utilization rate of bauxite tailings and fly ash, resulting in significant economic value.

[0025] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0027] Figure 1 Schematic diagram of the preparation method of ceramsite in this embodiment.

[0028] Figure 2 This is a diagram of the ceramsite product prepared under different ratios in the present invention.

[0029] Figure 3 This is a diagram of the ceramsite products prepared at different roasting temperatures in the present invention. DETAILED DESCRIPTION

[0030] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0031] Table 1 Raw materials and their chemical compositions

[0032]

[0033] In this embodiment, the above raw materials are used as the main raw materials for making ceramsite, and the specific steps are as follows:

[0034] (1) Pretreatment: Bauxite tailings and fly ash are already dry solids and do not require drying. They are also free of impurities during collection and transportation, so no special treatment is required. Use a crusher to initially crush the raw materials, then grind them finely in a mortar. Use a 100-mesh sieve to sieve out the 100-mesh bauxite tailings and fly ash for later use.

[0035] (2) Mixing: Mix bauxite tailings, starch, bentonite and fly ash according to the ratio in the firing plan and stir them thoroughly.

[0036] (3) Molding: Add an appropriate amount of water according to the weighed amount of material, and granulate into raw material balls with a particle size of 5 mm.

[0037] (4) Drying: Place the raw material balls in an electric blast drying oven for drying at a temperature of 105°C for 2 hours.

[0038] (5) Preheating and roasting: Take out the raw material balls after drying and place them on a graphite plate, put them into a muffle furnace, and set the preheating and roasting temperature and time according to the firing plan.

[0039] (6) Screening: The temperature of the ceramsite to be fired is lowered to room temperature. The ceramsite with a smooth surface and a ceramic shell that has expanded in volume after firing is selected by visual inspection, and the firing plan of this ceramsite is recorded. By screening the ceramsite, the purpose of screening the firing plan is achieved.

[0040] (7) Finished product: The qualified expanded clay is bagged for subsequent testing of the expanded clay bulk density and porosity.

[0041] Through the above method, the present invention conducts experiments with different ratios and different roasting temperatures, as follows:

[0042] The experimental schemes with different proportions are shown in Table 2, where the preheating temperature is 750℃, the preheating time is 15min, the roasting temperature is 1150℃, the roasting time is 30min, and the ceramsite raw material proportions are as follows:

[0043] Table 2 Experimental raw material ratio

[0044]

[0045] from Figure 2 As can be seen from a, when the raw material ratio is the ratio of Example 1, the ceramsite forms a ceramic shell with a smooth surface, good vitrification effect, volume expansion, and a complete appearance; Figure 2 As can be seen from Figure b, when the raw material ratio is the ratio of Example 2, the ceramsite forms a ceramic shell with a smooth surface, a low degree of vitrification, no volume expansion, and a complete appearance; Figure 2It can be seen from Figure c that when the raw material ratio is the ratio of Example 3, the ceramsite forms a ceramic shell with a smooth surface, a lower degree of vitrification, no volume expansion, and a complete appearance; Figure 2 It can be seen from Figure d that when the raw material ratio is the ratio of Example 4, the ceramsite does not form a ceramic shell, the surface is rough, the volume does not expand, the shape is incomplete, and ash falls off; Figure 2 It can be seen from Figure e that when the raw material ratio is the ratio of Example 5, the ceramsite does not form a ceramic shell, the surface is rough, the volume does not expand, the shape is incomplete, more ash falls off, and a small amount of ceramsite is broken; Figure 2 As can be seen from Figure f, when the raw material ratio is that of Example 6, the ceramsite does not form a ceramic shell, the surface is rough, the volume does not expand, the shape is incomplete, a lot of ash falls off, and a small amount of ceramsite is broken. Comparative Examples 1 to 6 show that the degree of ceramic formation of the ceramsite becomes lower and lower until no ceramic shell is formed, the surface becomes increasingly rough, and the degree of ceramsite formation becomes increasingly lower.

[0046] Chemical components can be divided into three categories based on their role in the firing process: gas-producing components, skeleton components, and fluxing components. Gas-producing components are the primary components responsible for the volume expansion of ceramsite and the formation of its internal microporous structure. Skeleton components, being insoluble, provide support during firing, forming the ceramic shell. Fluxing components regulate the melting point of the raw materials and influence the sintering temperature. Among the raw materials fired this time, the gas-producing components are mainly Fe2O3 and C. Both bauxite and fly ash have gas-producing components. The content of gas-producing components in bauxite is 20.69%, and the content of gas-producing components in fly ash is 16.25%. Because the content of gas-producing components in bauxite is higher than that in fly ash, the expansion properties of bauxite are better than those of fly ash in the firing experiment; the skeleton components are mainly Al2O3 and SiO2. The total amount of Al2O3 and SiO2 in bauxite is 49.48%, and the total amount of Al2O3 and SiO2 in fly ash is 57.83%. The skeleton component in fly ash is higher than that in bauxite; Al2O3 in the skeleton component is positively correlated with the sintering temperature, that is, the higher the Al2O3 content in the ceramsite, the higher the sintering temperature required for the ceramsite in theory. The Al2O3 content in bauxite is 38.23%, and the Al2O3 content in fly ash is 21.32%. In terms of Al2O3 content, bauxite is higher than fly ash. In the firing experiment, bauxite contributes more to increasing the sintering temperature of ceramsite. The fluxing components are mainly alkali metals and alkaline earth metals, namely TiO2 and CaO. The fluxing component content in bauxite is 0.96%, and the total fluxing component in fly ash is 6.54%. The fluxing component of fly ash is higher than that of bauxite. In the firing experiment, fly ash can show good fluxing properties, which is beneficial to reduce the sintering temperature of the skeleton component, form a ceramic shell, and enclose the gas produced by the chemical reaction of the gas-producing component to expand the volume of the ceramsite. From Figure 1It can be seen that the ratio of Example 1 is the best ratio among the 6 ratios. In the ratios of Examples 1 to 6, the amount of the skeleton component increases continuously, and the amount of the auxiliary melting component also increases, but the increase is lower than the increase of the skeleton component. That is, the theoretical sintering temperature of Examples 1 to 6 increases continuously, and the molding degree of the ceramsite corresponding to the ratios of Examples 1 to 6 at the same firing temperature becomes lower and lower.

[0047] The experimental scheme of different calcination temperatures is shown in Table 3. The optimal ratio of ceramsite (Example 1) is used for calcination, the preheating temperature is 750°C, the preheating time is 15 minutes, and the experimental scheme is as follows:

[0048] Table 3

[0049]

[0050] The effect of roasting temperature on the molding of ceramsite can be seen Figure 3 The morphology of ceramsite at different calcination temperatures.

[0051] from Figure 3 As can be seen in a, the ceramsite forms a ceramic shell with a smooth surface, good vitrification effect, volume expansion and complete appearance; Figure 3 As can be seen in Figure b, the ceramsite forms a ceramic shell with a smooth surface, low degree of vitrification, low density, no volume expansion, and a complete appearance. Comparing the two figures, 1150°C is the optimal firing temperature among the set firing temperatures.

[0052] The sintering process of ceramsite typically includes preheating and calcining. In the present invention, a muffle furnace is used to sinter the ceramsite, and the preheating and calcining stages are linked using a temperature setting program. This integration of the ceramsite sintering process is achieved using the muffle furnace. The sintering process determines the ceramsite's shape, such as whether a ceramic shell forms on the surface and the degree of formation, and whether and how much the volume expands. Whether the ceramsite forms a ceramic shell, as well as the degree of vitrification and density of the ceramic shell, are influenced by the raw material ratio and sintering temperature. The influence of ceramic raw materials primarily manifests itself in the ratio between the skeleton component and the fluxing component, which influences the degree of ceramic surface formation. Specifically, the ratio between the skeleton component Al2O3 and the fluxing components TiO2 and CaO influences the theoretical temperature required for ceramic surface formation. The melting point of Al2O3 is approximately 2050°C, and the skeleton component Al2O3 is directly proportional to the sintering temperature. A high Al2O3 content results in extremely high temperatures required to sinter the skeleton component to form a ceramic shell. The fluxing component, however, adjusts the melting point of the raw materials, lowering the melting point of the skeleton component, allowing the ceramic shell to form at lower sintering temperatures. The ratio between the skeleton component and the fluxing component determines the theoretical sintering temperature for ceramic surface formation. When the actual sintering temperature coincides with the theoretical ceramic surface formation temperature, the ceramic shell is fully formed. The degree of ceramic shell formation influences the ceramic volume expansion. When a ceramic shell with good vitrification and high density is formed, the shell can contain the gas generated by the gas-producing components, causing the ceramic volume to expand. Whether the volume of expanded clay expands is not only affected by the degree of ceramic formation, but also by the gas-producing components.

[0053] In the present invention, in addition to the gas-producing component Fe2O3 contained in bauxite and fly ash, an additional gas-producing component, starch, is added. Therefore, the gas-producing components of the present invention include Fe2O3 and C. During the sintering process of ceramsite, the gas-producing components undergo a variety of complex chemical reactions. From the perspective of reactants, the chemical reactions are not only affected by the chemical components and the ratio of the ceramsite raw materials, but also by the chemical reaction products. This is because most experiments in the ceramsite sintering process are continuous experiments, that is, the product of the previous experiment is used as a reactant to initiate the next chemical reaction. From the perspective of reaction conditions, that is, temperature, different sintering temperatures result in different chemical reactions. During the sintering process, the C on the surface of the ceramsite burns, producing CO2 and CO. Due to poor thermal conductivity, the surface temperature of the ceramsite is higher than the internal temperature. The reaction CO2+C→CO occurs in the high-temperature area of ​​the surface, and CO→C+CO2 occurs in the low-temperature area of ​​the interior. Due to the different temperatures, different chemical reactions occur on the surface and inside of the ceramsite, producing different types and amounts of gases. The different amounts of gas between the outside and the inside produce a pressure difference, which causes CO to migrate and diffuse from the high-temperature area of ​​the surface to the low-temperature area of ​​the interior, while CO2 diffuses from the low-temperature area of ​​the interior to the high-temperature area of ​​the outside. Fe2O3 reacts differently with different reactants and different sintering temperatures. If Fe2O3 undergoes the following reactions under anaerobic conditions:

[0054] 3Fe2O3+CO==2Fe3O4+CO2

[0055] When the sintering temperature is higher than 570℃, the reaction is:

[0056] Fe3O4+4CO==3FeO+CO2

[0057] FeO+CO→Fe+CO2

[0058] When the sintering temperature is lower than 570℃, the reaction is:

[0059] Fe3O4+4CO==3Fe+4CO2

[0060] If Fe2O3 undergoes the following reaction under aerobic conditions [4]:

[0061] Fe2O3→FeO+O2

[0062] FeO+Fe2O3→Fe3O4

[0063] Fe3O4→FeO+O2

[0064] Under oxygen conditions, the temperature required for the gas-producing component Fe2O3 is 1100℃ and above. The roasting temperatures of 1100℃ and 1150℃ fully meet the temperature required for the gas-producing component to undergo chemical reactions to produce gas. Therefore, when the roasting temperatures are 1100℃ and 1150℃, whether the ceramsite volume expands or not depends only on the degree of ceramic formation of the ceramsite.

[0065] Figure 3 The volume of the ceramsite in a did not expand because the temperature of 1100°C did not form a complete ceramic shell for the ceramsite, thus failing to enclose the generated gas. Figure 3 The volume expansion of the ceramsite in (b) is due to the fact that 1150°C forms a complete ceramic shell, encapsulating the gases produced by the chemical reaction of the gas-producing components within the ceramsite. These gases cause the ceramsite to expand in a short period of time. Overall, as the calcination temperature increases, the degree of ceramsite formation increases, and the degree of expansion also increases.

[0066] Preheating and roasting are mainly divided according to the difference in temperature. Although different reactions occur in different stages, the chemical experiments in the sintering process of ceramsite are continuous and mutually influential. The present invention uses a muffle furnace to integrate the preheating stage and the roasting stage, that is, to connect the two stages from the objective conditions, so that the product of the chemical reaction in the preheating stage directly affects the chemical reaction in the roasting stage. Therefore, when exploring the influence of a single factor of roasting temperature on ceramsite molding, it is inevitable that it will be affected to a certain extent by the preheating temperature. The present invention takes this problem into consideration and uses control variables to weaken the influence of their mutual influence, so the experimental results of the present invention can still reflect the influence of a single factor of roasting temperature on ceramsite molding.

[0067] From the above, it can be seen that the raw material ratio, preheating temperature, and roasting temperature in the present invention affect the formation of ceramsite. The raw material ratio of ceramsite theoretically determines the theoretical roasting temperature of ceramsite. The greater the ratio of skeleton component to flux component, the greater the sintering temperature required. As the preheating temperature increases, the degree of ceramic formation of the surface layer of ceramsite increases. As the roasting temperature increases, the degree of ceramic formation of the surface layer of ceramsite increases. Whether the ceramsite expands is positively correlated with the degree of ceramic formation of the surface layer of ceramsite. The success or failure of ceramsite firing is closely related to factors such as the chemical composition of the raw materials, the proportion of each raw material, the preheating temperature, and the roasting temperature. The firing of ceramsite is a complex chemical process, and there are many factors that affect the formation of ceramsite. Not only the influence of a single factor on the formation of ceramsite, but also the coordination relationship between the various factors also have a significant impact on the formation of ceramsite.

[0068] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and such modifications or substitutions are intended to be within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be subject to the scope of protection of the claims.

Claims

1. A method for preparing ceramsite, characterized in that: Including steps: (1) Pretreatment: crushing and sieving the bauxite tailings and fly ash to obtain bauxite tailings powder and fly ash powder respectively; (2) Mixing: uniformly mixing bauxite tailings powder, fly ash powder, starch, and bentonite to obtain a material mixture; (3) Molding: adding water to moisten the material mixture and granulating to obtain raw material balls; (4) Drying: Drying the raw balls to obtain dry raw balls; (5) Preheating and roasting: After preheating the dry raw material balls, roasting them to obtain the ceramsite.

2. The method for preparing ceramsite according to claim 1, wherein In step (1), the bauxite tailings and fly ash are crushed and passed through a 100-mesh sieve to obtain bauxite tailings powder and fly ash powder, respectively.

3. The preparation method of ceramsite according to claim 1, wherein In step (2), 20% of bauxite tailings powder, 20% of fly ash powder, 10% of starch and 50% of bentonite are mixed uniformly by mass percentage to obtain a material mixture.

4. The method for preparing ceramsite according to claim 1, wherein In step (3), the particle size of the raw material balls is 5 mm.

5. The method for preparing ceramsite according to claim 1, wherein In step (4), the drying temperature is 105° C. and the drying time is 2 h.

6. The method for preparing ceramsite according to claim 1, wherein In step (5), the dry raw material balls are placed in an electric boiler for preheating at a temperature of 750° C. for 15 minutes.

7. The method for preparing ceramsite according to claim 1, wherein In step (5), the calcination temperature is 1100-1150° C., and the calcination time is 30 minutes.

8. The method for preparing ceramsite according to claim 8, wherein In step (5), the calcination temperature is 1150° C. and the calcination time is 30 minutes.

9. The method for preparing ceramsite according to claim 1, wherein . Also includes the steps: (6) Screening: After roasting is completed, use the water density method to screen and select the products with a density less than 1g / cm 3 The ceramsite is used as the finished ceramsite product.

10. Ceramic granules prepared by the method for preparing ceramic granules according to any one of claims 1 to 9.

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