A method for resource utilization of low-grade refractory tin-containing tailings

Abstract

The application discloses a method for resource utilization of low-grade and refractory tin-containing tailings, and belongs to the technical field of solid waste resource utilization. The method comprises the following steps: uniformly mixing the low-grade and refractory tin-containing tailings with a fluorine-containing calcium compound, an alkalinity adjusting agent and a carbonaceous reducing agent, and then performing reduction roasting, recovering tin products from roasting flue gas, and using the remaining roasting tailings to prepare cementing materials. The method can not only efficiently recover tin from the low-grade tin-containing tailings, but also can use the tailings after tin recovery to prepare cementing materials with high added value, so that the resource utilization of the tailings is realized.

Description

TECHNICAL FIELD

[0001] The present application relates to a processing method of low-grade and refractory tin-containing tailings, in particular to a method for tin recovery and resource utilization of roasting tailings from low-grade and refractory tin-containing tailings, and belongs to the technical field of resource utilization of bulk mine solid waste. BACKGROUND

[0002] In China, polymetallic ore resources containing tin are abundant, and most of them belong to skarn type deposits. Such deposits are often associated with elements such as tungsten, tin, antimony, zinc and iron. Although the grade of tin has exceeded the minimum grade of 0.1-0.2% for exploitation, a large number of studies have shown that the tin minerals in such tin-containing deposits are mainly cassiterite, which is mostly in the form of medium-fine or coarse aggregate inclusions in fluorite or silicates, and a small number of inclusions in magnetite, sphalerite and arsenopyrite are metasomatic in gangue, or in the form of fine vein or disseminated distribution, and are mostly hosted in the intergranular and fissure space of calcium iron pyroxene and calcium iron garnet. The mineral types are various, and the associated relationship is complex, which leads to great difficulty in efficient recovery and utilization of cassiterite resources. Through conventional beneficiation process, the amount of tailings discarded is huge, and the processing cost is high, so it is very urgent to find a suitable method for recovering cassiterite resources in view of the current situation.

[0003] A Chinese invention patent (publication number CN113731628A) discloses a method for efficiently recovering cassiterite from fine-grained disseminated tin polymetallic ore, emphasizing the separation by conventional multi-ore dressing process, wherein the coarse-grained middlings and tin middlings are re-ground and re-processed middlings are returned to the respective grinding operation in turn, forming a grinding-gravity separation large cycle, although the qualified tin concentrate and tailings are finally output, the process is complex and the procedure is tedious. A Chinese invention patent (publication number CN115155824A) discloses a method for recovering tin from tin-containing fine sludge, emphasizing the use of technical means in the field of mineral processing to process and recover cassiterite, but the process is gradually becoming complex, and the flotation reagent system used is intensive, although the comprehensive recovery rate of tin obtained by processing can reach more than 80%, however, there are still a large amount of tailings that have not been processed. A Chinese invention patent (publication number CN102965522A) discloses a method for separating and recovering tin from tin-containing tailings, aiming at low-grade and refractory tin-containing tailings that are difficult to process by traditional ore dressing process, a method of volatilizing tin under weak reducing atmosphere is adopted, the tin volatilization rate mentioned in the invention is only 70-80%, the recovery efficiency is not high, and the treatment of subsequent tailings is mentioned less. A Chinese patent (publication number CN118222834A) discloses a method for resource utilization of garnet-type tin-containing tailings, which specifically mixes the garnet-type tin-containing tailings with an alkalinity adjusting agent and a carbonaceous reducing agent uniformly, then reduces and roasts under an oxygen-free atmosphere, recovers tin products from the roasting flue gas, and uses the remaining roasting tailings for composite portland cement or cementitious material. The tin recovery rate of this method is not ideal, and the roasting tailings obtained can only be used as a composite portland cement admixture, or used to prepare cementitious materials with PO425 cement, desulfurization gypsum, etc., which has a low dosage in cement or cementitious materials and is difficult to realize large-scale application.

[0004] Therefore, finding a way to efficiently process low-grade and refractory tin-containing tailings to recover valuable tin resources, and to dispose of the roasting slag for resource utilization, not only meets the development requirements of green mines, but also significantly improves social, economic and environmental benefits. SUMMARY

[0005] In view of the technical problems of low recovery efficiency of valuable metal elements in low-grade and refractory tin-containing tailings and low resource utilization rate of tailings in the prior art, the purpose of the present application is to provide a resource utilization method for low-grade and refractory tin-containing tailings, which can not only efficiently recover tin from low-grade tin-containing tailings, but also use the tailings after recovering tin to prepare cementitious materials with high added value, realizing the resource utilization of tailings.

[0006] In order to realize the above technical purpose, the application provides a method for resource utilization of low-grade and refractory tin-containing tailings, which comprises the following steps: mixing the low-grade and refractory tin-containing tailings with a fluorine-containing calcium compound, an alkalinity adjusting agent and a carbonaceous reducing agent, and then performing reduction roasting, recovering tin products from roasting flue gas, and using the remaining roasting tailings for cementing materials.

[0007] In the high-temperature reduction process, the carbonaceous reducing agent plays a role in promoting tin volatilization, mainly reducing SnO2 with high boiling point in the tailings into SnO with relatively low boiling point, thereby promoting tin volatilization and recovery, and providing a reduction environment for the roasting process; the fluorine-containing calcium compound acts as a mineralizer, which can not only promote and supplement the clinkerization reaction effect and element loss of the tailing composition during high-temperature roasting, but also play a good mineralization effect, enhance the clinkerization degree of silicate minerals in the tailings in a lower temperature range (900-1150 DEG C) during the roasting process, and improve the pozzolanic activity of the roasting tailings; and the alkalinity adjusting agent can improve the volatilization effect of tin by adjusting the alkalinity of the tailings, so as to obtain a higher tin volatilization recovery rate.

[0008] As a preferred scheme, the mass ratio of the low-grade refractory tin-containing tailings, the fluorine-containing calcium compound, the alkalinity adjusting agent and the carbonaceous reducing agent is 100:5-10:5-10:1-8. The introduction ratio of the fluorine-containing calcium compound, the alkalinity adjusting agent and the carbonaceous reducing agent has a relatively large influence on the volatilization recovery efficiency of tin in the low-grade refractory tin-containing tailings and the curing process of other minerals in the high-temperature reduction roasting process. More specifically, the amount of the carbonaceous reducing agent is not suitable to be too high. Since the grade of tin in the low-grade refractory tin-containing tailings is low, it is not suitable to set a too high amount of the reducing agent in the designed temperature range, mainly in order to avoid that a strong reducing atmosphere causes the reaction of magnetite and cassiterite in the tin-containing tailings to produce iron-tin alloy, so that tin cannot be volatilized, thereby causing the tin recovery rate to be reduced. However, the amount of the carbonaceous reducing agent is also not suitable to be too low, which will cause SnO2 to be difficult to be converted into SnO with a relatively low boiling point, thereby affecting the volatilization rate of tin. Meanwhile, the carbonaceous reducing agent also has the function of promoting the reconstruction of the crystal form of other minerals, and a too low content of the carbonaceous reducing agent will reduce the difficulty of the components of the tailings to be sufficiently cured, thereby reducing the pozzolanic activity. The mass ratio of the low-grade refractory tin-containing tailings and the carbonaceous reducing agent is further preferably 100:1.5-5. The fluorine-containing calcium compound is introduced as an important mineralizer. The calcium element in the fluorine-containing calcium compound is introduced as a calcium source, which is conducive to the conversion of silicate minerals in the low-grade refractory tin-containing tailings into high pozzolanic activity minerals. The fluorine element in the fluorine-containing calcium compound is a good mineralization component, which can reduce the melting temperature in the roasting process of the tailings, promote the clinkerization reaction of the calcium element and the silicate minerals, and the formed molten state is stirred by carbon dioxide, carbon monoxide and other gases in the reducing atmosphere, thereby reducing the gas volatilization path and being conducive to the reduction and volatilization of tin. Therefore, a too low introduction ratio of the fluorine-containing calcium compound is not conducive to the volatilization recovery of tin and the curing of minerals in the low-grade refractory tin-containing tailings. However, a too high ratio will more easily form a molten phase in the high-temperature calcination process, thereby causing the calcined material to be melted or bonded, affecting the fluidity and structure of the material. The alkalinity adjusting agent can react with the silicon dioxide (SiO2) in the fluorine-containing calcium compound, thereby increasing the alkalinity of the reacted clinker of the silicate minerals, generating calcium silicate (CaSiO3), and removing SiO2. This process reduces the impurity content in the reduction reaction, and the generated calcium silicate slag helps to reduce the viscosity of the molten slag, so that tin is more easily volatilized and discharged. In addition, the calcium oxide can also adjust the temperature gradient in the blast furnace, reduce the erosion in the high-temperature region, increase the fluidity of the slag, promote the mixing and dispersion of the material, and ensure the uniform reaction. Therefore, an appropriate amount of the alkalinity adjusting agent is very conducive to the volatilization of tin and the curing of minerals.

[0009] As a preferred scheme, the low-grade refractory tin-containing tailings contain quartz, feldspar, garnet, calcium iron pyroxene and magnetite, wherein the mass content of silicate minerals is greater than 75%, and the tin grade is 0.16-0.35%. Based on the characteristics of high content of silicate minerals, low tin grade and a small amount of magnetite in the low-grade refractory tin-containing tailings, it is determined that a high proportion of fluorine calcium compound, alkalinity regulator and a low proportion of carbonaceous reducing agent need to be added in the high-temperature reduction roasting process, so as to ensure efficient volatilization and recovery of tin, and at the same time, to realize full maturation of residual tailings and improve the pozzolanic activity.

[0010] As a preferred scheme, the fluorine calcium compound includes at least one of calcium monofluorophosphate, calcium fluorophosphate and calcium fluorosilicate. The preferred fluorine calcium compound contains calcium and fluorine elements, the calcium element can convert silicate or silicon dioxide and the like into calcium silicate and the like with pozzolanic activity, and the fluorine element can play a good mineralization effect, enhance the degree of clinkerization of silicate minerals in a lower temperature range (900-1150℃) during the roasting process of tailings, and improve the pozzolanic activity of the roasted tailings.

[0011] As a preferred scheme, the carbonaceous reducing agent includes at least one of anthracite, bituminous coal, semi-coke and coke. On the one hand, the carbonaceous reducing agent can reduce SnO2 with a high boiling point in the tailings into SnO with a relatively low boiling point at high temperature, thereby promoting the volatilization and recovery of tin, and on the other hand, the carbonaceous reducing agent provides a reducing environment for the roasting process.

[0012] As a preferred scheme, the alkalinity regulator includes calcium oxide. The preferred calcium oxide as the alkalinity regulator can react with silicon dioxide (SiO2) in the tailings, improve the alkalinity of the reaction clinker of silicate-containing minerals, generate calcium silicate (CaSiO3), and thereby remove SiO2. This process reduces the impurity content in the reduction reaction, and the generated calcium silicate slag helps to reduce the viscosity of the molten slag, so that the tin therein is more easily volatilized and discharged. In addition, the calcium oxide can also adjust the temperature gradient in the blast furnace, reduce the erosion in the high-temperature region, increase the fluidity of the slag, promote the mixing and dispersion of the materials, and ensure uniform reaction.

[0013] As a preferred scheme, the conditions of the reduction roasting are: from room temperature to 900-1150 DEG C, and holding for 30-60 min. In the preferred reduction roasting process, the reduction of the tin dioxide mineral into SnO can be realized, and the SnO enters the flue gas in the form of gas, and then forms solid SnO2 and Sn through the disproportionation reaction. Meanwhile, in the high-temperature environment and under the reduction of the carbonaceous reducing agent, the reconstruction of the silicate mineral in the tailings can be promoted, and the roasting tailings with the activity of the volcanic ash can be converted, so that the roasting tailings can be used for preparing the cementitious material. The conditions of the reduction roasting are further preferably: from room temperature to 950-1050 DEG C, and holding for 35-60 min.

[0014] As a preferred scheme, after the roasting tailings and the activator are activated, the roasting tailings are mixed with the ground granulated blast furnace slag to obtain the cementitious material. The roasting tailings and the activator are activated by using the high-energy ball milling. The specific surface area of the ball-milled material is controlled to be 760±10 m 2 / kg.

[0015] As a preferred scheme, the activator includes anhydrous sodium silicate with a modulus of 1.4-3.4; and the mass of the activator is 15-30% of the mass of the roasting tailings.

[0016] As a preferred scheme, the roasting tailings and the ground granulated blast furnace slag are mixed according to the mass percentage of 50-80%:20-50%. The roasting tailings have high activity of the volcanic ash, and the content of the roasting tailings is greatly improved.

[0017] As a more preferred scheme, the ground granulated blast furnace slag is the commercially available ground powder with the grade of S95.

[0018] The method for resource utilization of the low-grade and refractory tin-containing tailings provided by the application includes the following steps.

[0019] (1) Recovery of tin from the low-grade and refractory tin-containing tailings: the low-grade and refractory tin-containing tailings are pressure-filtered and dried, mixed with a carbonaceous reducing agent, a fluorine-containing calcium compound and an alkalinity adjusting agent in a mixer, and then the mixture is subjected to reduction roasting in a tubular vacuum furnace. The roasting process is: from room temperature to a preset temperature of 900-1150 DEG C, and holding for 30-60 min at the preset temperature. The tubular vacuum furnace is continuously supplied with a protective gas (the protective gas is preferably argon with a purity of >99%), and the gas flow is controlled to ensure that the roasting process is in an oxygen-free environment. The flue gas dusting system is used to recover the flue dust converted from the volatilized gaseous tin.

[0020] (2) Resource utilization of roasting tailings slag to prepare cementitious material: in a planetary ball mill, add roasting tailings slag, activator, ball mill speed is 600 r / min, grinding activation 60 min, medium filling rate is 18.5%. The activated tailings slag and slag powder are mixed uniformly, namely the cementitious material; wherein, the mass ratio of roasting tailings slag and slag powder is calculated according to the mass of slag powder replacing roasting tailings slag, namely 20-50%; the dosage of activator is 15-30wt% of the mass of roasting tailings slag.

[0021] Compared with the prior art, the technical scheme of the present application has the following beneficial technical effects:

[0022] 1. According to the occurrence form of tin in low-grade and difficult-to-select tin-containing tailings and the mineral composition, through high-temperature reduction roasting treatment, not only can tin be recovered by volatilization to realize high-value recovery of metal resources, but also can realize the reconstruction of silicate minerals and other phases in the tailings to obtain clinker with high pozzolanic activity, realizing the resource utilization of tailings, forming a closed loop of no tailings discharge mode for mining enterprises, creating new economic benefits, and solving the problems of solid waste utilization and environmental pollution in mines, with significant social and environmental benefits.

[0023] 2. The low-grade and difficult-to-select tin-containing tailings used in the present application contain more than 75% of silicate minerals. In the high-temperature reduction roasting process for recovering tin, by adding fluorine-containing calcium compounds as mineralizers, the low-temperature clinkerization degree can be strengthened, and the pozzolanic activity of the roasted tailings slag is further improved.

[0024] 3. In the high-temperature roasting process of low-grade and difficult-to-select tin-containing tailings, the key is to use carbonaceous reducing agent, fluorine-containing calcium compound and alkalinity adjusting agent. The carbonaceous reducing agent plays a reducing role and can promote the reduction of tin dioxide minerals in the tailings to stannous oxide with a relatively low boiling point. The fluorine-containing calcium compound strengthens and supplements the clinkerization process and elements of the tailings, and promotes the reconstruction of silicate minerals in the tailings under the action of the alkalinity adjusting agent, improves the clinkerization degree, and gives the roasted tailings high pozzolanic activity. The alkalinity adjusting agent can improve the volatilization effect of tin by adjusting the alkalinity of the tailings, so as to obtain a high tin volatilization recovery rate, and the tin recovery rate can reach more than 95%.

[0025] 4. The present application aims to realize the comprehensive utilization of tailings, and further utilizes the roasted tailings slag, achieving the goal of no tailings mine and expanding the utilization field of building material resources. By simplifying the preparation process of cementitious material, the prepared cementitious material is used as geopolymer for underground filling cementitious material in mines, which benefits the self-production and self-sale mode of mines, greatly utilizes the resource advantages of mines, realizes efficient resource utilization of solid waste, has obvious application value, and has significant economic and social benefits. DETAILED DESCRIPTION

[0026] The technical solutions of the present application are further described in detail below in combination with specific examples, but the protection scope of the claims is not limited to the examples.

[0027] The chemical reagents involved in the following specific examples are conventional industrial reagents if not otherwise specified.

[0028] In the following specific examples, the low-grade refractory tin-containing tailings used mainly have the following chemical composition: SiO237.85wt%, Al2O310.40wt%, CaO 20.17wt%, Fe2O325.66wt%, and tin grade 0.20-0.50%.

[0029] Example 1

[0030] A method for recovering tin from low-grade refractory tin-containing tailings and resource utilization thereof, comprising the following steps:

[0031] (1) Recovery of tin from tailings: The tailings are pressure-filtered and dried, mixed with 1.5% of bituminous coal, 8.6% of calcium fluophosphate, and 6.5% of calcium oxide in a mixer, and the mixture is roasted in a tubular vacuum furnace. The roasting process is from room temperature to a preset temperature of 955℃, and then the temperature is maintained for 35 min. Argon gas is continuously introduced into the tubular vacuum furnace as a protective gas, and the gas flow is controlled to ensure an oxygen-free environment during the roasting process. The volatilized tin is recovered by a flue gas dust collection system with oxygen. The recovery rate of tin is shown in Table 5.

[0032] (2) Preparation of cementitious material from roasted tailings slag: In a planetary ball mill, roasted tailings slag and activator are added, wherein the modulus of sodium silicate is 2.3, the dosage of activator is 25%, the ball mill speed is 600 r / min, the medium filling rate is 18.5%, and the grinding activation is 60 min. Then the activated tailings slag is mixed with slag powder at a weight ratio of 70:30 to obtain a cementitious material for underground mine filling.

[0033] Example 2

[0034] The differences from Example 1 are shown in Table 1 and Table 2.

[0035] Example 3

[0036] The differences from Example 1 are shown in Table 1 and Table 2.

[0037] Example 4

[0038] The differences from Example 1 are shown in Table 1 and Table 2.

[0039] Comparative Example 1

[0040] A conventional commercially available cementing powder is used as a control.

[0041] Comparative Example 2

[0042] The difference from Example 2 is that:

[0043] The roasting tailings in the cementing powder raw material was replaced by slag powder, and then mixed with the activator.

[0044] Comparative Example 3

[0045] The difference from Example 3 is referred to Table 1 and Table 2.

[0046] Comparative Example 4

[0047] The difference from Example 4 is referred to Table 1 and Table 2.

[0048] Comparative Example 5

[0049] The difference from Example 2 is referred to Table 1 and Table 2.

[0050] Table 1 Reduction roasting raw material composition and conditions

[0051] Name SnO2 grade / % Reducing agent type Reducing agent dosage / % Mineralizer type Mineralizer dosage / % Calcium oxide / % Roasting temperature / °C Soaking time / min Example 1 0.22 Bituminous coal 1.5 Calcium fluoro-phosphate 8.6 6.5 955 35 Example 2 0.26 Lan coal 5 Calcium fluoro-silicate 9.7 8.1 975 60 Example 3 0.18 Coke 2.4 Calcium mono-fluoro-phosphate 5.4 9.4 1050 41 Example 4 0.32 Coke 3.1 Calcium fluoro-phosphate 6.5 5.7 963 50 Comparative Example 3 0.18 Coke 2.4 / / 9.4 1050 41 Comparative Example 4 0.32 Coke 3.1 Calcium fluoro-phosphate 6.5 / 965 50 Comparative Example 5 0.26 Lan coal 15 Calcium fluoro-silicate 9.7 8.1 975 60

[0052] Table 2 Example and comparative example cementing material raw material composition

[0053] Name Roasting tailings / % Slag micro-powder / % Modulus of sodium silicate Sodium silicate dosage / % Example 1 70 30 2.3 25 Example 2 76 24 1.4 30 Example 3 64 36 2.3 18 Example 4 57 43 2.8 22 Comparative Example 2 0 100 1.4 30 Comparative Example 3 64 36 2.3 18 Comparative Example 4 57 43 2.8 22 Example 5 76 24 1.4 30

[0054] Performance test

[0055] Examples 1-4 and Comparative Examples 1-5 were respectively tested for compressive strength and fluidity. The test selected fluorite ore dressing full tailings with a concentration of 73.5%, and the method was compared according to GB / T 20100972-T-609, GB / T 31289-2014. The compressive strength mold selected 40x40x40mm three-way test mold. The tin volatilization rate of Examples 1-4 was tested. The test results are shown in Table 3.

[0056] Table 3 Performance test results and tin volatilization rate

[0057]

[0058] The test results show that the volatilization rate of tin in the examples of the present application under the condition of reduction roasting is greater than 95%. Increasing the amount of reducing agent will not improve the volatilization rate of tin, but will reduce it, because excessive reducing agent will cause incomplete reaction and produce unwanted by-products. For example, during the reduction process, excessive reducing agent may react with oxides or other reactants to generate gaseous or solid by-products, such as hydrogen, carbide or other impurities, affecting the purity of the product. The performance of the cementing material prepared by incorporating the roasting tailings is better than that of Comparative Example 2, indicating that after mineralization roasting, the activity of the tailings increases significantly. The results of Comparative Examples 2 and 3 also show that without the action of mineralizing agent, the effect of roasting clinkerization of tailings is poor, affecting its reactivity, and also has a certain weakening effect on the volatilization rate. The method implemented in the present application not only recovers valuable resources efficiently, but also utilizes the remaining solid waste in large quantities, which not only increases the efficiency of new products for mining enterprises, but also meets the energy saving and consumption reduction, realizes the purpose of developing and constructing green mines, and has popularization and reference significance for many mining enterprises.

[0059] It should be noted that the above examples are only part of the preferred modes of implementing the present application, not all. Obviously, based on the above examples of the present application, all other examples obtained by a person of ordinary skill in the art without creative labor should belong to the scope of protection of the present application.

Claims

1. A method for the resource utilization of low-grade, difficult-to-process tin-bearing tailings, characterized in that: Low-grade, difficult-to-select tin-containing tailings are mixed with fluorine-containing calcium compounds, alkalinity adjusters and carbonaceous reducing agents and then subjected to reduction roasting. Tin products are recovered from the roasting flue gas, and the remaining roasting tailings are used as cementitious materials. The mass ratio of the low-grade, difficult-to-process tin-bearing tailings to the fluorine-containing calcium compound, the alkalinity adjuster, and the carbonaceous reducing agent is 100: 5~10: 5~10: 1~8; The low-grade, difficult-to-process tin-bearing tailings contain quartz, feldspar, garnet, hedonicite, and magnetite, of which silicate minerals account for more than 75% and tin grade is 0.16-0.35%.

2. The method for resource utilization of low-grade, difficult-to-process tin-bearing tailings according to claim 1, characterized in that: The fluorinated calcium compound includes at least one of calcium monofluorophosphate, calcium fluorophosphate, and calcium fluorosilicate.

3. The method for resource utilization of low-grade, difficult-to-process tin-bearing tailings according to claim 1, characterized in that: The carbonaceous reducing agent includes at least one of anthracite, bituminous coal, semi-coke, and coke.

4. The method for resource utilization of low-grade, difficult-to-process tin-bearing tailings according to claim 1, characterized in that: The alkalinity adjuster includes calcium oxide.

5. The method for resource utilization of low-grade, difficult-to-process tin-bearing tailings according to claim 1, characterized in that: The conditions for reduction calcination are: raising the temperature from room temperature to 900~1150℃ and holding for 30~60 minutes.

6. A method for resource utilization of low-grade, difficult-to-process tin-bearing tailings according to claim 1, characterized in that: The roasted tailings and activator are activated and then mixed evenly with slag powder to obtain a cementitious material.

7. A method for resource utilization of low-grade, difficult-to-process tin-bearing tailings according to claim 6, characterized in that: The activator comprises anhydrous sodium silicate with a modulus of 1.4 to 3.4; the mass of the activator is 15 to 30% of the mass of the roasting tailings.

8. A method for resource utilization of low-grade, difficult-to-process tin-bearing tailings according to claim 6, characterized in that: The roasted tailings and the slag powder are mixed at a mass percentage of 50-80%: 20-50%.

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