Method for preparing high-strength light-weight ceramsite and recovering tin by using tin-containing tungsten tailings and red mud in cooperation

Abstract

The application discloses a method for preparing high-strength light-weight ceramsite and recovering tin by using tin-tungsten tailings and red mud, and belongs to the technical field of solid waste resource utilization. Raw materials such as tin-tungsten tailings and red mud are mixed with water to form a ball material, the ball material is dried, and then is transferred into a rotary kiln to be mixed with externally added coal to complete two-stage roasting, tin products are recovered from flue gas during the roasting process, and the solid products obtained through the roasting are subjected to physical separation to separate ceramsite products. The method utilizes the characteristics of high contents of iron, aluminum and sodium in the red mud to strengthen the decomposition and transformation of garnet in the tin-tungsten tailings to promote the volatilization of tin wrapped in the garnet, and forms high-strength light-weight ceramsite through raw material regulation. Compared with the method for simply recovering tin from the tin tailings, the method has a greatly reduced energy consumption, improved process added value, and no tailings produced, and therefore has important significance for the construction of tailings-free mines and the disposal of red mud, and has high economic feasibility.

Description

Technical Field

[0001] This invention relates to a method for the co-processing of tin-tungsten tailings and red mud, specifically a method for the co-processing of tin-tungsten tailings and red mud to prepare high-strength lightweight ceramsite and recover tin, belonging to the field of solid waste resource utilization technology. Background Technology

[0002] Tin, as an important non-ferrous metal, is widely used in industries such as electronics, metallurgy, and chemicals. As a key component of welding materials, tin plays an indispensable role in electronic equipment, communications, and semiconductors. It is also widely used in bronze alloys, tin plating, catalysts, and other fields, and has an irreplaceable role in machinery, shipbuilding, sculpture, and chemicals. Currently, domestic tin resources are relatively scarce, and the country relies heavily on imports. Although the region possesses certain tin ore resources, the grade is relatively low, and with the increasing depletion of high-quality tin ore, the domestic tin supply faces significant pressure.

[0003] In some regions of China, tungsten tailings contain tin resources of a certain grade and in huge quantities. However, due to the excessively fine particle size, traditional flotation technology is unable to achieve effective recovery and utilization. Pyrometallurgical reduction volatilization for tin recovery has become a feasible method. However, direct reduction roasting is difficult to destroy the garnet shell that encapsulates the tin, and the low basicity leads to roasting temperatures exceeding 1000℃, while the tin recovery rate is only about 80%. As the roasting slag has not achieved mineral phase transformation above 1300℃~1450℃, it can only be used as cement admixture, and the blending ratio is less than 10%, resulting in limited utilization of roasting slag and failure to achieve high-value utilization.

[0004] Red mud is an alkaline solid waste generated during the Bayer process for alumina production. China produces over 80 million tons of red mud annually, but its comprehensive utilization rate is less than 10%, causing multiple harms to the environment and resources, including leachate pollution of groundwater, land occupation due to stockpiling, dust pollution, and potential dam failure risks. To reduce the amount of red mud stockpiled, researchers are actively exploring comprehensive utilization methods, including its use as a building material in cement, expanded clay, and concrete. However, its alkalinity and safety issues need to be addressed.

[0005] To date, there have been no reports on technologies for the co-processing of tin-containing tungsten tailings and red mud to prepare high-strength lightweight ceramsite and recover tin. If the co-processing of tin-containing tungsten tailings and red mud can be achieved, it will be of great significance for ensuring the sustainable use of national tin resources and solving the problem of tailings and red mud stockpiling. Summary of the Invention

[0006] To address the technical problems of low tin recovery rate, high energy consumption, and low utilization value of roasting slag in existing pyrometallurgical reduction volatilization methods for tin-containing tungsten tailings, as well as the technical problems of large stockpiles, low utilization rate, and serious environmental pollution caused by red mud, the present invention aims to provide a method for co-preparing high-strength lightweight ceramsite from tin-containing tungsten tailings and red mud and recovering tin. This method fully utilizes the inherent mineral composition characteristics of both tin-containing tungsten tailings and red mud, combining them through a high-temperature solid-phase reaction to achieve efficient tin volatilization and recovery, while obtaining high-quality ceramsite products that meet the requirements of the 700 or 800 type high-strength lightweight coarse aggregate (GB / T17431.1-2010) standard. This truly realizes the resource utilization of both solid wastes. Compared with the process of simply using high-temperature volatilization of tin-containing tungsten tailings to recover tin, not only is the tin recovery rate improved, but there is also no tailings generated, significantly increasing the added value. This is of great significance for the construction of tailings-free mines and the disposal of red mud, and the process has extremely high economic feasibility.

[0007] To achieve the above-mentioned technical objectives, this invention provides a method for co-preparing high-strength lightweight ceramsite from tin-tungsten tailings and red mud, and recovering tin. The method involves mixing raw materials, including tin-tungsten tailings, red mud, coal powder, silicon powder, quicklime, silicon carbide, and ceramsite powder, with water to form pellets. After drying, the pellets are transferred to a rotary kiln and mixed with external coal to complete two-stage roasting. During the roasting process, tin products are recovered from the flue gas. The solid products obtained from roasting are physically sorted to separate the ceramsite products.

[0008] The key to this invention lies in the high-temperature roasting treatment of tin-tungsten tailings and red mud. Based on the composition of the ceramsite raw materials, red mud has the characteristics of high content of phases such as iron, aluminum, and sodium. It complements the tin-tungsten tailings in terms of phases such as silicon, aluminum, sodium, and calcium. By adjusting the proportion of raw materials, the composition requirements of the ceramsite can be met. Furthermore, the aluminum, sodium, and calcium phases in the red mud can induce the destruction of the garnet shell that encapsulates tin in the tin-tungsten tailings, thereby promoting the volatilization of tin. At the same time, the high iron content in the red mud also imparts magnetism to the ceramsite, which is beneficial for the subsequent separation of the ceramsite from coal powder. More specifically, garnet in tin-tungsten tailings encapsulates tin, hindering its reduction and volatilization at high temperatures. However, by combining it with red mud, which is high in iron, aluminum, and sodium, and subjecting it to high-temperature synergistic treatment, the decomposition and transformation of garnet are promoted by increasing the content of aluminum, sodium, and calcium phases. Among them, sodium and calcium phases can reduce the liquid phase formation temperature and viscosity of the roasting system by generating low-melting-point silicate liquid phases. In particular, sodium phase, as a strong alkaline oxide, has a significant fluxing effect, forming phases such as albite and sodium silicate. Aluminum and calcium phases provide additional aluminum and calcium sources, enhancing the bridging between aluminum, calcium, and silicon-oxygen in the system, making the silicon-oxygen tetrahedral network structure in garnet unstable and causing the silicate framework to reorganize. In addition, aluminum phases participate in the formation of ceramsite-supported framework phases such as mullite and spinel, while calcium phases participate in the formation of calcium silicate (such as C2S and C3S) phases. The successful decomposition of garnet releases the encapsulated tin components, thereby improving the efficiency of tin volatilization recovery. Furthermore, because the raw material composition meets the basic requirements of the three components of silicon, aluminum, and alkaline metal oxides in the Riley triangle, the liquid phase can be controlled by temperature regulation, thereby further producing ceramsite in the tin recovery process.

[0009] In the co-processing of tin-tungsten tailings and red mud of this invention, additional auxiliary materials are added, such as coal powder, silicon powder, quicklime, silicon carbide, and ceramsite powder, which are beneficial for ceramsite formation and promoting tin volatilization. Silicon carbide mainly acts as a foaming agent, primarily to compensate for the consumption of some coal powder during the reduction reaction and decomposition in the high-temperature roasting process. Ceramsite powder is mainly used to avoid the generation of solid waste; substandard ceramsite is crushed and returned to the ceramsite preparation process, and its addition has almost no impact on the performance of the ceramsite. Quicklime mainly acts as a binder. Since tin-tungsten tailings are fine sand with extremely low viscosity, a binder is required. Compared with bentonite, quicklime can also provide a calcium source. Calcium regulation can lower the roasting temperature and promote the formation of some calcium silicate phases, which helps the alkali activation effect in the later production of ceramsite concrete, and can also promote the separation of garnet. The deconversion process facilitates the volatilization of tin. Coal powder, as the main reducing component, not only acts as a reducing agent and provides a CO reducing atmosphere, which is conducive to the conversion of tin into easily volatile stannous oxide and improves the tin volatilization recovery efficiency, but it is also the main foaming component. The residual coal powder that is not consumed in the tin reduction stage continues to decompose at high temperature in the second stage of ceramsite expansion, generating gas, which, together with the gas generated by the decomposition of silicon carbide, promotes the foaming of ceramsite. The role of silicon powder is to supplement the silicon content of the system. The silicon component not only participates in the formation of mullite, spinel and other phases that support the ceramsite framework, but is also the main component of the glass phase. As a typical low-melting-point substance, the glass phase can indirectly control the formation temperature of low-melting-point substances by controlling the proportion of the glass phase by adjusting the silicon content. In conjunction with the metal flux, the ceramsite expansion temperature is made to be above the optimal volatilization temperature of tin, and the calcination temperature of ceramsite is reduced as much as possible while achieving a clear distinction between the two processes.

[0010] As a preferred embodiment, the raw materials comprise the following components by weight: 60-75 parts tin-tungsten tailings, 20-35 parts red mud, 3-5 parts coal powder, 5-10 parts silicon powder, 3-7 parts quicklime, 1-2 parts silicon carbide, and 10-15 parts ceramsite powder. The ratio of tin-tungsten tailings to red mud needs to meet the basic requirements for the phase composition of ceramsite. Simultaneously, the proportion of red mud must ensure a high proportion of iron in the ceramsite raw materials to impart strong magnetism to the ceramsite, thus facilitating subsequent magnetic separation. Silicon carbide acts as a foaming agent in the system, primarily to compensate for the consumption of some foaming material (coal powder) during reduction and decomposition in the first roasting stage. Therefore, its proportion needs to be added appropriately based on the proportion of coal powder. The incorporation ratio of ceramsite powder is mainly determined based on the output; within the preferred range, all of it can be incorporated, thereby reducing solid waste generation. Insufficient quicklime content leads to poor material adhesion, making it difficult to form pellets or prone to pulverization during drying. Excessive quicklime content results in excessively low liquid phase generation temperature, causing severe kiln caking and affecting production. For example, lowering the kiln temperature can lead to incomplete tin volatilization. Insufficient coal powder content weakens the reducing atmosphere inside the ceramsite, requiring internal tin reduction to rely on the internal diffusion of reducing gas from outside the pellets. This increases the internal tin reduction process, prolongs the reduction roasting time, and reduces the reduction effect and tin recovery rate. Conversely, excessive coal powder content results in a high residual amount after ceramsite firing, affecting the physical properties of the ceramsite.

[0011] As a preferred embodiment, the tin-tungsten tailings contain 0.4–0.6 wt.% tin, 5–10 wt.% Fe₂O₃, 45–60 wt.% SiO₂, 5–10 wt.% Al₂O₃, and 5–10 wt.% CaO. As another preferred embodiment, the red mud contains 20–30 wt.% Fe₂O₃, 5–15 wt.% SiO₂, 12–20 wt.% Al₂O₃, 5–15 wt.% CaO, and 4–8 wt.% Na₂O. As the main raw materials for preparing ceramsite, the existing tin-tungsten tailings and red mud have complementary chemical compositions in terms of the content of phases such as silicon, aluminum, sodium, and calcium. For example, tin-tungsten tailings have high silicon content, low aluminum content, and low sodium content, while red mud has low silicon content, high aluminum content, and high sodium content. By combining the two in an appropriate ratio, the requirements for generating major ceramic phases such as mullite and spinel can be fully met. In addition, the iron content in red mud must reach a certain amount, because in addition to participating in the reaction to form phases such as fir olivine, the main function of iron is to be magnetized and reduced to iron(III) oxide, which makes the pellets magnetic and facilitates separation from bituminous coal.

[0012] The quicklime of this invention undergoes significant volume increase upon contact with water for digestion. To avoid damage to the raw ceramsite pellets during pelletizing, the quicklime can be digested first.

[0013] As a preferred embodiment, the fineness of the tin-tungsten tailings meets the requirement that the mass content of -200 mesh particles is ≥70%.

[0014] As a preferred embodiment, the red mud has a fineness that satisfies the requirement that the mass content of -100 mesh particles is ≥75%.

[0015] As a preferred embodiment, the fineness of the pulverized coal meets the requirement that the mass content of -100 mesh particles is ≥85%.

[0016] The particle size of the tin-tungsten tailings, red mud, and coal powder in this invention is controlled within an appropriate particle size range, which is beneficial to the subsequent pelletizing and high-temperature roasting processes.

[0017] As a preferred embodiment, the pelletizing is achieved using a disc pelletizer, with the pellet size controlled within the range of 6–9 mm. Using a disc pelletizer ensures uniform pelletizing. Since the particle size distribution of ceramsite requires a narrow range, a disc pelletizer is used to guarantee stable process parameters and product requirements. If the green pellet size is too large, the diffusion path of tin within the pellet becomes longer, leading to incomplete tin volatilization. Furthermore, excessively large green pellets cause uneven sintering heat, affecting the uniform expansion and pore structure of the ceramsite, resulting in poor expansion and reduced lightweight, high-strength properties. Conversely, if the green pellet size is too small, although the tin volatilization path can be shortened, the pellets are prone to caking in the furnace, hindering long-term stable production in the rotary kiln. Additionally, excessively small particle sizes may prevent effective gas expansion during sintering, thus affecting the expansion effect of the ceramsite, and limiting the application range of ceramsite with excessively small particle sizes.

[0018] As a preferred embodiment, the drying process employs a combination of rotary kiln waste heat drying and microwave drying, with the drying aiming to control the moisture content of the pellets to ≤3 wt.%. By controlling the moisture content of the pellets at a low level, the risk of pellet bursting during subsequent roasting can be reduced.

[0019] As a preferred embodiment, the external coal is supplied via a rotary kiln tail-end coal supply method; the external coal accounts for 40% to 70% of the mass of the dried material balls. The external coal serves two purposes: firstly, it provides heat for combustion, and the combustion rate is controlled by adjusting the fan flow rate, thereby regulating the kiln temperature; secondly, it creates a reducing atmosphere, ensuring the entire kiln is under a reducing atmosphere by balancing the oxygen consumption of the external coal combustion with the oxygen supply from the fan. Insufficient external coal supply will result in incomplete combustion or insufficient coal quantity, leading to a drop and fluctuation in kiln temperature. Excessive supply will occupy kiln space, reducing throughput, and also increase the workload of sorting the roasted products.

[0020] As a preferred embodiment, during the two-stage roasting process, the temperature of the first-stage roasting is controlled between 800℃ and 900℃, and the roasting time is 30 to 60 minutes; the temperature of the second-stage roasting is controlled between 900℃ and 1000℃, and the roasting time is 20 to 40 minutes. The first-stage roasting temperature is relatively low, with tin volatilization being the primary process. At this temperature, only a very small amount of local liquid phase is generated within the ceramic particles, which can promote the transformation and decomposition of garnet without hindering tin volatilization. The second-stage roasting temperature is relatively high, with the formation of ceramic particles being the primary process. At this temperature, the increased amount of liquid phase initiates overall mineral phase regeneration, forming a ceramic particle support framework structure including mullite, spinel, and calcium silicate phases, which significantly encapsulates the gas, achieving the expansion effect on the ceramic particles.

[0021] As a preferred embodiment, the physical separation includes screening and dry air-magnetic separation. The physical separation process is as follows: the roasted solid product is first screened through a 5mm screen. The undersize product is then used as ceramsite pulverized material after being processed by a high-pressure roller mill. The oversize product is separated into ceramsite product and coal lumps by dry air-magnetic separation. The coal lumps are used as external coal blending material. Since the reduction and volatilization of tin are collected along with the flue dust, and the final roasted solid product contains very little powder, mainly consisting of lumpy coarse and fine-grained ceramsite and bituminous coal, the undersize product at -5mm screen mainly consists of ceramsite pulverized material and incompletely burned bituminous coal lumps. If this is directly fed into the rotary kiln for re-roasting, it is very easy to generate a large amount of pulverized material, causing kiln caking and reducing the tin grade in the flue dust collection system. It also reduces the permeability of the roasted material in the kiln, hindering tin volatilization. Therefore, the ceramsite pulverized material is returned to the ceramsite preparation raw material.

[0022] As a preferred embodiment, the output particle size of the high-pressure roller mill is controlled to have a mass ratio of -100 mesh particles ≥ 60%. If the particle size of the ceramsite powder is not controlled and it is used for ceramsite preparation, the excessively large bituminous coal particles will lead to incomplete combustion, reducing the strength and durability of the ceramsite. Furthermore, excessively large coal particles will release heat in a concentrated manner, causing cracks or irregular shapes in the ceramsite, affecting the expansion effect and performance.

[0023] Compared with the prior art, the beneficial technical effects of the technical solution of the present invention are as follows:

[0024] (1) According to the raw material composition, the present invention co-processes red mud and tin-containing tungsten tailings, utilizes the phase in the red mud to promote the phase transformation of the garnet shell, thereby promoting the volatilization of the tin encapsulated therein, increasing the tin reduction and volatilization recovery rate to more than 95%, and significantly reducing the roasting energy consumption.

[0025] (2) Based on the pyrometallurgical tin recovery, this invention successfully produces high-strength lightweight ceramic particles by adjusting raw materials and continuous reduction roasting in dual temperature zones, realizing the high-value utilization of roasting slag, which has reference significance for the construction of tailings-free mines and the disposal of red mud.

[0026] (3) This invention uses a synergistic approach and a set of processes to obtain two products: tin-rich flue dust and high-strength lightweight ceramic particles. This significantly reduces the roasting cost compared to simple pyrometallurgical reduction roasting for tin removal, and has great economic feasibility.

[0027] (4) This invention utilizes the co-processing of tin-containing tungsten tailings and red mud, achieving a tin recovery rate of ≥95% in the tin-containing tailings. Simultaneously, the diameter of the finished ceramsite is between 7 and 14 mm, and the bulk density is between 600 and 800 kg / m³. 3 Between these values, the compressive strength of the cylinder is ≥6.0MPa, and the water absorption rate in 1 hour is ≤5.50%, which meets the requirements of the 700 or 800 type high-strength lightweight coarse aggregate standard (GB / T17431.1-2010). Detailed Implementation

[0028] The technical solution of the present invention will be further described below through specific embodiments and comparative examples, so as to more clearly demonstrate the purpose, technical solution and advantages of the present invention.

[0029] A tin-tungsten tailings ore from southern Hunan Province was selected as the research object. Its main chemical composition is as follows: Sn content 0.44 wt.%, Fe2O3 content 7.42 wt.%, SiO2 content 55.13 wt.%, Al2O3 content 6.92 wt.%, CaO content 6.11 wt.%, and fineness (-200 mesh) 76%. Red mud from Guangxi Province was selected as a co-material, with Fe2O3 content 27.11 wt.%, SiO2 content 10.71 wt.%, Al2O3 content 17.21 wt.%, CaO content 11.42 wt.%, Na2O content 6.55 wt.%, and fineness (-100 mesh) 83%. Silica powder was obtained from an industrial silicon smelter in Guangxi Province, with SiO2 content 88.31 wt.%. Coal powder, silicon carbide, quicklime, and bituminous coal were commercially available industrial grade, with coal powder having a fineness (-100 mesh) of 87%.

[0030] The performance of expanded clay aggregate was tested according to the GB / T17431.2-2010 standard:

[0031] (1) Bulk density: Take 40L of ceramsite, dry it in a drying oven to constant weight, and divide it into two portions. Use a sampling spoon or shovel to evenly pour the ceramsite from 50mm above the container opening, allowing it to fall naturally without colliding with the measuring cylinder. After filling, make the ceramsite at the top of the measuring cylinder form a cone shape. Then, use a ruler to scrape the surface level from the center outwards along the edge of the measuring cylinder. Fill any depressions on the surface with smaller ceramsite particles, and then weigh the product. Calculate using the following formula.

[0032]

[0033] ρ bu Bulk density, measured in kilograms per cubic meter (kg / m³)3 ), calculated to an accuracy of 1 kg / m 3 ;

[0034] m t Total mass of expanded clay and measuring cylinder, in kilograms (kg);

[0035] m v The mass of the measuring cylinder is expressed in kilograms (kg).

[0036] V: The volume of the container, measured in liters (L).

[0037] The arithmetic mean of the two measurements was taken as the experimental result.

[0038] (2) Cylinder compressive strength: 5L of 5mm-15mm ceramsite is sieved and placed into a standard pressure-bearing cylinder with a bottom. The cylinder is placed on a concrete test vibrating table and vibrated for 3 seconds. Then, ceramsite is added until it exceeds the cylinder opening, and the cylinder is vibrated for another 5 seconds. The ceramsite is then scraped (or supplemented) to level the cylinder opening. The guide cylinder and stamping die are installed, aligning the lower graduation line of the stamping die with the upper edge of the guide cylinder. The pressure-bearing cylinder is placed on the lower pressure plate of the press, aligned with the center of the pressure plate, and a uniform load is applied at a speed of 300N-500N per second. When the stamping die penetrates to a depth of 20mm, the pressure value is recorded.

[0039] Calculate using the following formula.

[0040]

[0041] f a Compressive strength of cylinder, measured in megapascals (MPa);

[0042] P1: Pressure value when the indentation depth is 20mm, in Newtons (N);

[0043] P2: Mass of stamping die, in Newtons (N);

[0044] F: Pressure-bearing area (i.e., stamping die area F = 10000 mm²) 2 ).

[0045] The cylinder compressive strength is determined by the arithmetic mean of three measurements. If the difference between the maximum and minimum values ​​among the three measurements exceeds 15% of the average, a new sample is taken and the test is repeated.

[0046] (3) Water absorption rate: Take 4L of ceramsite and dry it to a constant weight. Mix the ceramsite evenly and divide it into three equal parts. Weigh each part separately and then put them into a container of water. If any particles float on the water, press them into the water. After soaking the ceramsite for 1 hour, take it out and drain it for 1-2 minutes. Then pour it onto a wrung-out damp towel. Hold both ends of the towel to make it into a trough shape and let the ceramsite roll back and forth on the towel 8-10 times to make it saturated and dry. Then weigh it. Calculate according to the following formula.

[0047]

[0048] w a 1-hour water absorption rate, %;

[0049] m0: Mass of soaked ceramsite, in grams (g);

[0050] m1: Mass of dried ceramsite, in grams (g).

[0051] The arithmetic mean of the three measurements was used as the experimental result.

[0052] Example 1

[0053] After drying, the tin-tungsten tailings and red mud are screened. The lumpy material on the screen is crushed and screened again to ensure the particle size meets the requirements. Quicklime is placed in a mixer, and 2.5 times its weight of cold water is gradually and slowly added while stirring. It is pre-digested and then cooled. The raw materials are batched by weight as follows: 65 parts tin-tungsten tailings, 30 parts red mud, 3 parts coal powder, 6 parts silicon powder, 5 parts quicklime, 1.5 parts silicon carbide, 12 parts undersize crushed material, and 21 parts water. The raw materials are mixed evenly using a two-stage mixing method, and pelletized using a disc pelletizer to control the pellet size between 6 and 9 mm. The waste heat airflow from the furnace is used for preliminary drying. After drying, the pellets are thoroughly dried in a microwave dryer until constant weight, then fed into a rotary kiln for roasting. Coal is supplied from the kiln tail, with an additional 50% wt of coal added based on the weight of the pellets entering the kiln. The first roasting temperature is controlled at 840℃ for 40 minutes, and the second roasting temperature is controlled at 960℃ for 30 minutes. The roasted product is first sieved through a 5mm screen. The undersized product is then ground in a high-pressure roller mill and used as ceramsite pulverizer. The oversized product is separated from the coal lumps by dry air-magnetic separation to obtain the final ceramsite product. The final tin recovery rate is 97.63%, and the bulk density of the ceramsite is 679 kg / m³. 3 The cylinder compressive strength is 6.42 MPa, and the water absorption rate is 5.11% in 1 hour.

[0054] Example 2

[0055] After drying, the tin-tungsten tailings and red mud are sieved. The lumpy material on the sieve is crushed and sieved again to ensure that the particle size meets the requirements. Quicklime is placed in a mixer and then gradually and slowly added with 2.5 times the weight of the quicklime in cold water while stirring. It is pre-digested and then cooled. An experiment was conducted using 70 parts by weight of tin-tungsten tailings, 23 parts of red mud, 5 parts of coal powder, 8 parts of silicon powder, 5 parts of quicklime, 1.5 parts of silicon carbide, 12 parts of undersized crushed material, and 21 parts of water. After the raw materials are batched, they are mixed evenly using a two-stage mixing method. Pelletizing is carried out using a disc pelletizer, and the pellet size is controlled between 6 and 9 mm. The waste heat airflow from the furnace is used for preliminary drying. After drying, the pellets are thoroughly dried in a microwave dryer until constant weight, then fed into a rotary kiln for roasting. Coal is supplied from the kiln tail, with an additional 50% wt of coal added based on the weight of the pellets entering the kiln. The first roasting temperature is controlled at 840℃ for 40 minutes, and the second roasting temperature is controlled at 940℃ for 30 minutes. The roasted product is first sieved through a 5mm screen. The undersized product is then ground in a high-pressure roller mill and used as ceramsite pulverizer. The oversized product is separated from the coal lumps by dry air-magnetic separation to obtain the final ceramsite product. The final tin recovery rate is 96.27%, and the bulk density of the ceramsite is 607 kg / m³. 3 The cylinder compressive strength is 6.14 MPa, and the water absorption rate is 4.22% in 1 hour.

[0056] Example 3

[0057] After drying, the tin-tungsten tailings and red mud are screened. The lumpy material on the screen is crushed and screened again to ensure that the particle size meets the requirements. Quicklime is placed in a mixer and then gradually and slowly added with 2.5 times the weight of the quicklime in cold water while stirring. It is pre-digested and then cooled. An experiment was conducted using 60 parts by weight of tin-tungsten tailings, 35 parts of red mud, 3 parts of coal powder, 5 parts of silicon powder, 6 parts of quicklime, 2 parts of silicon carbide, 10 parts of undersized crushed material, and 21 parts of water. The raw materials are mixed in a two-stage mixing process and pelletized using a disc pelletizer. The pellet size is controlled between 6 and 9 mm. The waste heat airflow from the furnace is used for preliminary drying. The pellets were then thoroughly dried in a microwave dryer until constant weight, and then fed into a rotary kiln for roasting. Coal was supplied from the kiln tail, with an additional 50% wt of coal added based on the weight of the pellets entering the kiln. The first-stage roasting temperature was controlled at 860℃ for 40 minutes, and the second-stage roasting temperature was controlled at 980℃ for 30 minutes. The roasted product was first sieved through a 5mm screen. The undersized product was then processed by a high-pressure roller mill and used as ceramsite pulverization material. The oversized product was separated from the coal lumps by dry air-magnetic separation to obtain the final ceramsite product. The final tin recovery rate was 98.11%, and the bulk density of the ceramsite was 742 kg / m³. 3 The cylinder compressive strength is 7.41 MPa, and the water absorption rate is 5.37% in 1 hour.

[0058] Example 4

[0059] After drying, the tin-tungsten tailings and red mud are screened. The lumpy material on the screen is crushed and screened again to ensure that the particle size meets the requirements. Quicklime is put into a mixer and then gradually and slowly added with 2.5 times the weight of the quicklime in cold water while stirring. It is pre-digested and then cooled. An experiment was conducted using 65 parts by weight of tin-tungsten tailings, 22 parts of red mud, 3 parts of coal powder, 6 parts of silicon powder, 5 parts of quicklime, 1 part of silicon carbide, 15 parts of undersize crushed material, and 21 parts of water. After the raw materials are mixed, they are mixed evenly using a two-stage mixing method. The pellets are then pelletized using a disc pelletizer, and the pellet size is controlled between 6 and 9 mm. The waste heat airflow from the furnace is used for preliminary drying. The pellets were then thoroughly dried in a microwave dryer until constant weight, and then fed into a rotary kiln for roasting. Coal was supplied from the kiln tail, with an additional 50% wt of coal added based on the weight of the pellets entering the kiln. The first roasting temperature was controlled at 890℃ for 60 minutes, and the second roasting temperature was controlled at 920℃ for 40 minutes. The roasted product was first sieved through a 5mm screen. The undersized product was then ground in a high-pressure roller mill and used as ceramsite pulverizer. The oversized product was separated from the coal lumps by dry air-magnetic separation to obtain the final ceramsite product. The final tin recovery rate was 95.34%, and the bulk density of the ceramsite was 705 kg / m³. 3 The cylinder compressive strength is 6.71 MPa, and the water absorption rate is 4.78% in 1 hour.

[0060] Example 5

[0061] After drying, the tin-tungsten tailings and red mud are screened. The lumpy material on the screen is crushed and screened again to ensure that the particle size meets the requirements. Quicklime is placed in a mixer and then gradually and slowly added with 2.5 times the weight of the quicklime in cold water while stirring. It is pre-digested and then allowed to cool. An experiment was conducted using 65 parts by weight of tin-tungsten tailings, 30 parts of red mud, 5 parts of coal powder, 5 parts of silicon powder, 7 parts of quicklime, 2 parts of silicon carbide, 12 parts of undersized crushed material, and 21 parts of water. After the raw materials are batched, they are mixed evenly using a two-stage mixing method. Pelletizing is carried out using a disc pelletizer, and the pellet size is controlled between 6-9 mm. The waste heat airflow from the furnace is used for preliminary drying. The pellets were then thoroughly dried in a microwave dryer until constant weight, and then fed into a rotary kiln for roasting. Coal was supplied from the kiln tail, with an additional 50% wt of coal added based on the weight of the pellets entering the kiln. The first roasting temperature was controlled at 820℃ for 60 minutes, and the second roasting temperature was controlled at 980℃ for 30 minutes. The roasted product was first sieved through a 5mm screen. The undersized product was then ground in a high-pressure roller mill and used as ceramsite pulverizer. The oversized product was separated from the coal lumps by dry pneumatic magnetic separation to obtain the final ceramsite product. The final tin recovery rate was 96.53%, and the bulk density of the ceramsite was 644 kg / m³. 3 The cylinder compressive strength is 6.35 MPa, and the water absorption rate is 5.46% in 1 hour.

[0062] Comparative Example 1

[0063] Compared to Example 1, with all other conditions unchanged, silicon carbide was removed and the amount of coal powder was changed to 5 parts, resulting in a final tin recovery rate of 97.58% and a bulk density of ceramsite of 839 kg / m³. 3 The cylinder compressive strength was 6.48 MPa, and the water absorption rate was 3.86% in 1 hour. The removal of silicon carbide led to a deterioration in the foaming effect, which could not be compensated for even after increasing the coal powder to 5 parts. At this point, the bulk density increased while the cylinder compressive strength increased slightly.

[0064] Comparative Example 2

[0065] Compared with Example 1, with all other conditions unchanged except for the removal of the undersize pulverized material, the final tin recovery rate was 95.47%, and the bulk density of the ceramsite was 775 kg / m³. 3 The compressive strength of the cylinder is 7.13 MPa, and the water absorption rate is 3.59% in 1 hour. The proportion of undersize crushed material has little impact on the physical properties of the ceramsite. Its main purpose is to reuse the roasting solid waste. Because the undersize crushed material contains a certain amount of coal powder, the removal of the undersize crushed material results in less coal powder being added. If the amount of coal powder added is not increased, it will lead to a lower tin recovery rate and a higher bulk density.

[0066] Comparative Example 3

[0067] Compared with Example 1, all other conditions remained the same, except that the roasting process was changed to a single roasting at 850°C for 60 minutes. The final tin recovery rate was 97.82%, and the bulk density of the ceramic particles was 1446 kg / m³. 3 The compressive strength of the cylinder is 12.15 MPa, and the water absorption rate is 1.93% in 1 hour. The low calcination temperature in the first stage resulted in insufficient liquid phase production, which failed to encapsulate the gas and achieve the expansion of the ceramsite.

[0068] Comparative Example 4

[0069] Compared with Example 1, all other conditions remained the same, except that the roasting process was changed to a single roasting at 950°C for 60 minutes. The final tin recovery rate was 83.31%, and the bulk density of the ceramic particles was 682 kg / m³. 3 The compressive strength of the cylinder is 6.53 MPa, and the water absorption rate is 4.63% in 1 hour. The first stage of calcination temperature was too high, which caused a large amount of liquid phase to be generated in the ceramic particles before the tin was completely volatilized, which hindered the outward diffusion of tin vapor. It was also accompanied by a glass-curing effect, which hindered the subsequent volatilization of tin.

[0070] Comparative Example 5

[0071] Compared with Example 1, with other conditions remaining unchanged, except that the pellet diameter was changed to 12-15 mm and the first-stage calcination time was extended to 60 min, the final tin recovery rate was 87.43% and the bulk density of the ceramsite was 532 kg / m³. 3The compressive strength of the cylinder is 4.21 MPa, and the water absorption rate is 6.14% in 1 hour. Increasing the diameter of the ceramsite pellets leads to a larger gap between the pellets, reducing the bulk density of the ceramsite. Furthermore, the larger pellet diameter makes the diffusion path of tin from the inside out longer and more difficult, resulting in a decrease in tin recovery rate.

[0072] Comparative Example 6

[0073] Compared with Example 1, all other conditions remained the same, except that the pellet ratio was changed to 85 parts tin-tungsten tailings, 8 parts coal powder, 8 parts quicklime, 2 parts silicon carbide, 13 parts undersize pulverized material, and 23 parts water. The final tin recovery rate was 87.46%, and the bulk density of the ceramsite was 726 kg / m³. 3 The compressive strength of the ceramsite is 2.84 MPa, and the water absorption rate is 3.96% in 1 hour. Furthermore, the non-magnetic nature of the ceramsite prevents effective and rapid separation from bituminous coal. The removal of red mud reduces the induced destruction of the tin garnet shell, and the lack of an iron source to provide magnetism leads to a decrease in tin recovery and ineffective separation.

[0074] The comparative examples show that tin-containing tungsten tailings and red mud have a good synergistic effect in promoting tin volatilization and preparing ceramsite. Through the complementarity of raw material components and the addition of auxiliary materials, a single process can be used to complete the reduction and volatilization of tin and the firing of high-strength lightweight ceramsite.

Claims

1. A method for co-preparing high-strength lightweight ceramsite from tin-containing tungsten tailings and red mud, and recovering tin, characterized in that: Raw materials, including tin-tungsten tailings, red mud, coal powder, silicon powder, quicklime, silicon carbide, and ceramsite powder, are mixed with water to form pellets. After drying, the pellets are transferred to a rotary kiln and mixed with external coal to complete two-stage roasting. During the roasting process, tin products are recovered from the flue gas. The solid products obtained from roasting are physically sorted to separate ceramsite products.

2. The method for co-preparing high-strength lightweight ceramsite from tin-containing tungsten tailings and red mud and recovering tin according to claim 1, characterized in that: The raw materials comprise the following components by weight: 60-75 parts of tin-tungsten tailings, 20-35 parts of red mud, 3-5 parts of coal powder, 5-10 parts of silicon powder, 3-7 parts of quicklime, 1-2 parts of silicon carbide, and 10-15 parts of ceramsite powder.

3. A method for co-preparing high-strength lightweight ceramsite from tin-containing tungsten tailings and red mud, and recovering tin, as described in claim 1 or 2, characterized in that: The tin-containing tungsten tailings contain 0.4–0.6 wt.% tin, 5–10 wt.% Fe2O3, 45–60 wt.% SiO2, 5–10 wt.% Al2O3, and 5–10 wt.% CaO. The red mud contains 20–30 wt.% Fe2O3, 5–15 wt.% SiO2, 12–20 wt.% Al2O3, 5–15 wt.% CaO, and 4–8 wt.% Na2O.

4. A method for co-preparing high-strength lightweight ceramsite from tin-containing tungsten tailings and red mud, and recovering tin, as described in claim 1 or 2, characterized in that: The fineness of the tin-tungsten tailings meets the requirement that the mass content of -200 mesh particles is ≥70%; The red mud has a fineness that meets the requirement that the mass content of -100 mesh particles is ≥75%; The fineness of the pulverized coal meets the requirement that the mass content of -100 mesh particles is ≥85%.

5. The method for co-preparing high-strength lightweight ceramsite from tin-containing tungsten tailings and red mud and recovering tin according to claim 1, characterized in that: The pelletizing process is achieved using a disc pelletizer, and the pellet size is controlled within the range of 6 to 9 mm.

6. The method for co-preparing high-strength lightweight ceramsite from tin-containing tungsten tailings and red mud and recovering tin according to claim 1, characterized in that: The drying process employs a combination of rotary kiln waste heat drying and microwave drying, with the moisture content of the pellets controlled to be ≤3wt.%.

7. The method for co-preparing high-strength lightweight ceramsite from tin-containing tungsten tailings and red mud and recovering tin according to claim 1, characterized in that: The external coal is supplied via a rotary kiln tail gasification system; the external coal accounts for 40% to 70% of the mass of the dried material balls.

8. The method for co-preparing high-strength lightweight ceramsite from tin-containing tungsten tailings and red mud and recovering tin according to claim 1, characterized in that: During the two-stage roasting process, the temperature of the first stage roasting is controlled between 800℃ and 900℃, and the roasting time is 30 to 60 minutes; the temperature of the second stage roasting is controlled between 900℃ and 1000℃, and the roasting time is 20 to 40 minutes.

9. The method for co-preparing high-strength lightweight ceramsite from tin-containing tungsten tailings and red mud and recovering tin according to claim 1, characterized in that: The physical separation includes screening and dry air-magnetic separation. The physical separation process is as follows: the roasted solid product is first screened through a 5mm screen, the undersize product is used as ceramsite powder after being ground by a high-pressure roller mill, and the oversize product is separated into ceramsite product and coal lumps by dry air-magnetic separation. The coal lumps are used as external coal blending.

10. The method for co-preparing high-strength lightweight ceramsite from tin-containing tungsten tailings and red mud and recovering tin according to claim 9, characterized in that: The output particle size of the high-pressure roller mill is controlled to have a mass ratio of -100 mesh particles ≥ 60%.

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