Method for harmlessly utilizing cyanidation tailings

Abstract

The invention provides a harmless utilization method of cyanidation tailings, and belongs to the field of cyanidation tailings solid waste resource utilization, cyanidation tailings are used as a main raw material, municipal sludge, fly ash and a purifying agent are matched, and after mixing and roasting (in an oxygen-free atmosphere), harmless lightweight aggregate meeting the standard is obtained. According to the method, the inert gas serves as the protective atmosphere, anaerobic pyrolysis is kept in the whole roasting process, hydrocarbon gas generated in the reaction process is beneficial to formation of pores in the lightweight aggregate, and the collapse degree of the generated pores can be reduced; in this way, the release degree of harmful substances in the cyanidation tailings in the environment is effectively reduced, and pollution to the environment is reduced; in addition, valuable building materials are produced, and waste recycling is achieved. A new solution is provided for treatment of the cyanidation tailings, and development of the environmental protection industry is promoted.

Description

Technical Field

[0001] The invention relates to the technical field of resource utilization of cyanidation tailings solid waste, and in particular to a method for harmless utilization of cyanidation tailings. Background Art

[0002] Most of the gold production in my country adopts the cyanidation method to extract gold. With the rapid development of my country's gold industry, mineral resources are constantly being developed, and the amount of cyanidation tailings is also increasing. Cyanidation tailings are solid powders discarded after gold and other useful components are recovered through ore dressing or gold extraction processes. At present, most of the full-mud cyanidation slag is harmlessly treated and disposed of in accordance with the tailings pond disposal requirements of the "Technical Specifications for Pollution Control of Cyanide Slag in the Gold Industry" (HJ943-2018). However, the full-mud cyanidation slag tailings pond disposal method brings many problems such as resources, environment, safety and land. Due to the high grinding fineness and low valuable element content of cyanidation tailings, it is impossible to carry out comprehensive utilization work such as valuable element recovery.

[0003] The patent with publication number CN115028433A provides a cyanide tailings-based sintered light aggregate and a preparation method thereof, which uses cyanide tailings as the main raw material, mixed with municipal sludge and contaminated soil, and sintered the light aggregate at high temperature. However, the light aggregate prepared by this method has a low bulk density and insufficient cylinder pressure strength, which hinders the subsequent use of the light aggregate.

[0004] In view of this, it is necessary to propose a method for harmless utilization of cyanide tailings to solve the above problems. Summary of the invention

[0005] In view of the technical problems existing in the background technology, the present application provides a method for harmless utilization of cyanide tailings, which aims to solve the technical problem of poor applicability of light aggregates formed in the prior art by roasting the cyanide tailings under an inert atmosphere to reduce the degree of collapse of the generated pores.

[0006] The present application embodiment provides a method for harmless utilization of cyanide tailings, comprising the following steps:

[0007] S1. Drying and grinding cyanide tailings, municipal sludge, fly ash and purifier respectively;

[0008] S2, mixing the cyanide tailings, the municipal sludge, the fly ash and the purifier in a predetermined proportion, adding water and stirring to prepare pellets; and then drying the pellets;

[0009] S3. Preheating, sintering and cooling the dried pellets in sequence to obtain harmless light aggregates.

[0010] In the technical solution of the embodiment of the present application, by mixing cyanide tailings with municipal sludge, fly ash, and purifiers and roasting them to convert them into harmless light aggregates, not only the release of harmful substances in the cyanide tailings into the environment is effectively reduced, reducing environmental pollution; but also valuable building materials are produced, realizing the resource utilization of waste. In addition, the prepared light aggregate has the characteristics of low density and good thermal insulation performance, and can be used as a building material in construction projects to improve the performance of building materials.

[0011] In some embodiments, in step S3, during the preheating, sintering, and cooling processes, an inert gas is used as a protective atmosphere; the rate of filling the inert gas in step S3 is 0.5-3.0 L / min; the inert gas includes but is not limited to nitrogen.

[0012] In this embodiment, by using inert gas as a protective atmosphere, the entire roasting process is maintained in anaerobic pyrolysis, and the hydrocarbon gas generated during the reaction is beneficial to the formation of pores in the light aggregate; in addition, compared with the reaction under high temperature aerobic conditions, the thermal weight loss of organic components in the sludge under anaerobic conditions can also be greatly reduced, thereby reducing the degree of collapse of the generated pores.

[0013] In some embodiments, the specific process of preheating, sintering and cooling in step S3 is as follows:

[0014] The preheating process is as follows: in a blast furnace, the temperature is raised to 400°C to 600°C at a rate of 10°C / min to 30°C / min, and kept warm for 30min to 60min for preheating; then the temperature is raised to 1000°C to 1200°C at a rate of 5°C / min to 20°C / min, and sintered for 20min to 60min; and finally, the temperature is naturally cooled with the furnace temperature.

[0015] In this embodiment, the organic matter and water in the mixed material are fully activated by preheating at a temperature of 400° C. to 600° C. before subsequent calcination.

[0016] In some embodiments, in step S2, the predetermined ratio is: the mass ratio of cyanide tailings: municipal sludge: fly ash is 50% to 70%: 10% to 30%: 5% to 20%; the amount of the purifier added is 5% to 10% of the total mass of cyanide tailings, municipal sludge and fly ash.

[0017] In this embodiment, by mixing cyanide tailings, municipal sludge, fly ash, and purifier in a suitable ratio, the toxic components in the cyanide tailings can be effectively neutralized, the stabilization of heavy metals in the cyanide tailings can be promoted, and the harm to the environment can be reduced.

[0018] In some embodiments, in step S2, the amount of water added is 22% to 27% of the total mass of cyanide tailings, municipal sludge, fly ash, and purifier.

[0019] In this embodiment, adding a proper amount of water helps the mixture to form pellets.

[0020] In some embodiments, the purifier includes chloride; the purifier includes one or a combination of potassium chloride, sodium chloride, calcium chloride, and magnesium chloride.

[0021] In this embodiment, by adding the purifier, not only can the harmful components in the cyanide tailings be promoted to undergo thermal decomposition or chemical reaction at high temperature, thereby reducing their toxicity and effectively ensuring that the heavy metal content in the finally prepared light aggregate can meet the emission standards, but the melting point of the mixture can also be reduced during the roasting process, which helps to form a liquid phase and promote solid-phase reaction, thereby improving the microstructure and properties of the light aggregate. To a certain extent, light aggregate can be prepared at a relatively low sintering temperature, thereby reducing energy consumption and being low-carbon and environmentally friendly.

[0022] In some embodiments, in step S1, the particle size of the cyanide tailings, the municipal sludge, the fly ash, and the purifier after grinding is greater than 200 meshes.

[0023] In this embodiment, by grinding the particle size of each raw material to above 200 meshes, the contact area between the raw materials can be increased, thereby improving the subsequent reaction efficiency between the raw materials.

[0024] In some embodiments, in step S2, the pellets need to be aged before drying; the aging time is 0.5h to 2h; and the particle size of the pellets is 10mm to 15mm.

[0025] In this embodiment, by aging the pellets for 0.5h to 2h, the material distribution inside the pellets can be made more uniform, and the moisture can be further evenly distributed, which helps to improve the mechanical strength and stability of the pellets, reduce the breakage of the pellets during subsequent drying and sintering, and also helps to densify the internal structure of the pellets and reduce the porosity, thereby forming a more uniform and dense lightweight aggregate in the subsequent sintering process.

[0026] In some embodiments, the drying process in step S3 is: drying at 100° C. to 110° C. for 1 hour to 4 hours.

[0027] In this embodiment, drying the mixed material before calcining can remove free moisture in the mixture, thereby reducing the volume change and structural damage of the material caused by water evaporation during the calcining process.

[0028] In some embodiments, in step S3, the blast furnace includes a box-type resistance furnace.

[0029] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solution of the present application, the following is a brief introduction to the drawings used in the present application. Obviously, the drawings described below are only some embodiments of the present application, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0031] Figure 1 This is a schematic diagram of the process flow of a method for harmless utilization of cyanide tailings provided in an embodiment of the present application. DETAILED DESCRIPTION

[0032] The following embodiments of the technical solution of the present application are described in detail in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present application, and are therefore only used as examples, and cannot be used to limit the scope of protection of the present application.

[0033] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians in the technical field to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" in the specification and claims of this application and the above-mentioned figure descriptions and any variations thereof are intended to cover non-exclusive inclusions.

[0034] In the description of the embodiments of the present application, the technical terms "first", "second", etc. are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features. In the description of the embodiments of the present application, the meaning of "multiple" is more than two, unless otherwise clearly and specifically defined.

[0035] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0036] In the description of the embodiments of the present application, the term "and / or" is only a description of the association relationship of the associated objects, indicating that there may be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0037] In the description of the embodiments of the present application, the term "multiple" refers to more than two (including two). Similarly, "multiple groups" refers to more than two groups (including two groups), and "multiple pieces" refers to more than two pieces (including two pieces).

[0038] In the description of the embodiments of the present application, the technical terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, which are only for the convenience of describing the embodiments of the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the embodiments of the present application.

[0039] In the description of the embodiments of the present application, unless otherwise clearly specified and limited, technical terms such as "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, and it can be the internal connection of two elements or the interaction relationship between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the embodiments of the present application can be understood according to the specific circumstances.

[0040] Cyanide tailings are the tailings discarded after gold extraction by cyanidation. They contain heavy metals, residual cyanide, mercury, various flotation agents and other highly toxic components, especially complex ion cyanide, which is easily converted into highly toxic cyanide due to changes in environmental pH. Improper treatment can easily cause serious pollution to the atmosphere, water bodies and soil. In the existing technology, the use of cyanide tailings to prepare cement, ceramics, glass-ceramics and other building materials has been studied. Because it contains cyanide and other harmful heavy metals, these components may not be completely decomposed or fixed during the expansion process, resulting in the risk of environmental pollution during the use of expanded ceramsite. In addition, the physical and chemical properties of cyanide tailings-based expanded ceramsite may not be as good as those of traditional ceramsite, such as strength, durability and water absorption, which limits its application in certain fields.

[0041] In order to solve the above-mentioned technical problems, the present application provides a method for harmless utilization of cyanide tailings, wherein cyanide tailings are used as the main raw material, and are mixed with municipal sludge, fly ash, and a purifier, and then roasted in an inert atmosphere, so as to reduce the release of harmful substances in the cyanide tailings into the environment, and the density, bulk density, and cylinder pressure strength of the prepared lightweight aggregate are also improved.

[0042] For the convenience of description, the following embodiments are described by taking a method for harmless utilization of cyanide tailings according to an embodiment of the present application as an example.

[0043] like Figure 1 As shown, the embodiment of the present application provides a method for harmless utilization of cyanide tailings, comprising the following steps:

[0044] S1. Drying and grinding cyanide tailings, municipal sludge, fly ash and purifier respectively;

[0045] S2, mixing the cyanide tailings, the municipal sludge, the fly ash and the purifier in a predetermined proportion, adding water and stirring to prepare pellets; and then drying the pellets;

[0046] S3. Preheating, sintering and cooling the dried pellets in sequence to obtain harmless light aggregates.

[0047] By using physical and chemical methods to convert harmful solid waste into harmless and valuable light aggregate, not only the release of harmful substances in cyanide tailings into the environment is effectively reduced, thus reducing environmental pollution; valuable building materials are also produced, thus realizing the resource utilization of waste.

[0048] Furthermore, in some embodiments, in step S3, during the preheating, sintering, and cooling process, an inert gas is used as a protective atmosphere; the rate of inert gas filling in step S3 is 0.5-3.0 L / min; the inert gas includes but is not limited to nitrogen. Using an inert gas as a protective atmosphere allows the entire roasting process to maintain anaerobic pyrolysis, and the hydrocarbon gas generated during the reaction is conducive to the formation of pores in the light aggregate; in addition, compared with the reaction under high temperature aerobic conditions, the thermal weight loss of organic components in the sludge under anaerobic conditions can also be greatly reduced, thereby reducing the degree of collapse of the generated pores.

[0049] Further, in some embodiments, the specific process of preheating, sintering and cooling in step S3 is:

[0050] The preheating process is as follows: in a blast furnace, the temperature is raised to 400°C to 600°C at a rate of 10°C / min to 30°C / min, and kept warm for 30min to 60min for preheating; then the temperature is raised to 1000°C to 1200°C at a rate of 5°C / min to 20°C / min, and sintered for 20min to 60min; and finally, the temperature is naturally cooled with the furnace temperature.

[0051] Preheating stage: The heating rate of 10℃ / min to 30℃ / min is selected to ensure that the moisture and volatile substances in the mixture can gradually escape, and to avoid rapid heating that causes the material to expand, rupture or form an uneven pore structure; the temperature range of 400℃ to 600℃ is sufficient to remove most of the moisture and some organic matter, and at the same time begin to promote certain chemical reactions, such as the dehydration of clay minerals and the thermal decomposition of carbonates; keeping warm for a period of time helps to homogenize the temperature inside the mixture, complete certain intermediate reactions, and fully activate the organic matter and moisture in the mixture, preparing for subsequent high-temperature sintering. Sintering stage: The heating rate of 5℃ / min to 20℃ / min is slower than that of the preheating stage. This is to ensure that the material gradually reaches thermal equilibrium at high temperature, reduce thermal stress, and prevent material rupture. At a temperature of 1000℃ to 1200℃, the silicate minerals in the mixture begin to melt and form a liquid phase, which helps to bond and recrystallize between particles and improve the strength and stability of the lightweight aggregate. The sintering time of 20 minutes to 60 minutes is to ensure that the chemical reaction in the mixture is fully carried out, the heavy metal ions are fixed, the silicate minerals are fully melted and recrystallized, and a stable lightweight aggregate structure is formed. Finally, natural cooling with the furnace temperature can prevent excessive internal stress of the lightweight aggregate caused by sudden temperature changes, resulting in cracking or deformation. Slow cooling helps to maintain the structure and performance of the lightweight aggregate.

[0052] Furthermore, in some embodiments, in step S2, the predetermined ratio is: the mass ratio of cyanidation tailings: municipal sludge: fly ash is 50% to 70%: 10% to 30%: 5% to 20%; the amount of the purifier added is 5% to 10% of the total mass of cyanidation tailings, municipal sludge, and fly ash. By mixing cyanidation tailings, municipal sludge, fly ash, and purifier in a suitable ratio, the toxic components in the cyanidation tailings can be effectively neutralized, the stability of heavy metals in the cyanidation tailings can be promoted, and the harm to the environment can be reduced.

[0053] Furthermore, in some embodiments, in step S2, the amount of water added is 22% to 27% of the total mass of cyanide tailings, municipal sludge, fly ash, and purifier. Adding an appropriate amount of water helps the mixture to form pellets.

[0054] In the technical scheme of the embodiment of the present application, the purifier includes chloride; the purifier includes one or more compounds of sodium chloride, calcium chloride, and magnesium chloride. By adding a purifier, not only can the harmful components (such as cyanide) in the cyanide tailings be thermally decomposed or chemically reacted at high temperature, thereby reducing its toxicity, effectively ensuring that the heavy metal content in the final prepared light aggregate can meet the discharge standards, but also can reduce the melting point of the mixture during the roasting process, help to form a liquid phase, promote solid phase reaction, thereby improving the microstructure and performance of the light aggregate, and to a certain extent, at a relatively low sintering temperature, the light aggregate can be prepared, thus reducing energy consumption, low carbon and environmental protection; in addition, the added chloride can react with silicates and aluminates in fly ash to generate stable minerals, and improve the mechanical strength and durability of the light aggregate. Calcium chloride and magnesium chloride can form stable complexes or precipitations with heavy metal ions, thereby fixing heavy metals and reducing their mobility in the environment. During the roasting process, the addition of chloride helps to form a uniform pore structure, so that the light aggregate has better thermal insulation performance and lower density. Through chemical reactions and physical adsorption, purifiers help reduce the emission of harmful substances in cyanide tailings and reduce the impact on the environment.

[0055] Furthermore, in some embodiments, in step S1, the particle size of the cyanide tailings, the municipal sludge, the fly ash, and the purifier after grinding is greater than 200 meshes. By grinding the particle size of each raw material to greater than 200 meshes, the contact area between the raw materials can be increased, and the subsequent reaction efficiency between the raw materials can be improved.

[0056] Furthermore, in some embodiments, in step S2, the pellets need to be aged before drying; the aging time is 0.5h to 2h; and the particle size of the pellets is 10mm to 15mm. By aging the pellets for 0.5h to 2h, the material distribution inside the pellets can be made more uniform, and the moisture can be further evenly distributed, which helps to improve the mechanical strength and stability of the pellets, reduce the breakage of the pellets during the subsequent drying and sintering process, and also helps to densify the internal structure of the pellets and reduce the porosity, thereby forming a more uniform and dense light aggregate in the subsequent sintering process.

[0057] Furthermore, in some embodiments, the drying process in step S3 is: drying at 100° C. to 110° C. for 1 hour to 4 hours. Drying the mixture before calcining can remove free water in the mixture and reduce the volume change and structural damage of the material caused by water evaporation during the calcination process.

[0058] Furthermore, in some embodiments, in step S3, the blast furnace includes a box-type resistance furnace.

[0059] Some specific embodiments are listed below. It should be noted that the embodiments described below are exemplary and are only used to explain the present application, and should not be construed as limiting the present application. If specific techniques or conditions are not specified in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. The reagents or instruments used without specifying the manufacturer are all conventional products that can be obtained commercially.

[0060] Example 1

[0061] A method for harmless utilization of cyanide tailings comprises the following steps:

[0062] S1. Drying and grinding cyanide tailings, municipal sludge, fly ash and purifier respectively;

[0063] The particle size of the cyanide tailings, the municipal sludge, the fly ash and the purifier after grinding treatment is above 200 meshes; the specific chemical composition of each raw material is shown in Table 1; the pollutant components of the cyanide tailings and the municipal sludge are analyzed, and the cyanide tailings contain harmful pollutants such as cyanide and heavy metals, and the municipal sludge contains organic pollutants, microorganisms and heavy metals, etc. The specific results are shown in Table 2;

[0064] S2, mixing the cyanide tailings, the municipal sludge, the fly ash and the purifier uniformly according to the mass ratio, adding water and stirring to prepare pellets; then aging and drying the pellets in sequence; the natural aging time in a cool and ventilated place is 0.5h; the particle size of the pellets is 10mm-15mm;

[0065] The ratio is: the mass ratio of cyanide tailings: municipal sludge: fly ash is 50%:30%:20%; the amount of the purifier added is 10% of the total mass of cyanide tailings, municipal sludge and fly ash;

[0066] The amount of water added is 25% of the total mass of cyanide tailings, municipal sludge, fly ash and purifier;

[0067] The purifier includes one or more of sodium chloride, calcium chloride and magnesium chloride;

[0068] S3, the pellets are first placed in an oven at 105°C for 1 hour for drying, and then placed in a box-type resistance furnace for preheating, sintering, and cooling in sequence to obtain harmless light aggregate;

[0069] During the preheating, sintering and cooling process, nitrogen was used as the protective atmosphere; the nitrogen filling rate was 1L / min;

[0070] The specific process of preheating, sintering and cooling is as follows:

[0071] The preheating process is as follows: in a blast furnace, the temperature is raised to 400° C. at a rate of 10° C. / min and kept for 30 minutes for preheating; then the temperature is raised to 1000° C. at a rate of 5° C. / min and sintered for 20 minutes; and finally, the blast furnace is naturally cooled with the furnace temperature.

[0072] Table 1 Chemical composition analysis of cyanide tailings and municipal sludge (%)

[0073] Components <![CDATA[SiO 2 ]]> CaO <![CDATA[Al 2 THE 3 ]]> <![CDATA[Fe 2 THE 3 ]]> MgO Cyanide tailings 67.38～72.63 1.0～1.5 13.5～18 3.5～5.8 0.3～0.54 Municipal sludge 9.5～15.3 10～15.78 3.23～4.27 3.5～4.2 0.58～0.7 Fly ash 32.9～59.7 0.9～8.4 15.5～35.6 4.5～19.5 0.36～0.8

[0074] Table 2 Analysis of pollutant components of cyanide tailings and municipal sludge (mg / kg)

[0075]

[0076]

[0077] The light aggregate prepared in this embodiment was analyzed and tested. The results of various indicators of the product light aggregate are shown in Table 3, the test results of pollutant content in the light aggregate are shown in Table 4, and the test results of leachable heavy metal content in the light aggregate are shown in Table 5.

[0078] Table 3 Lightweight aggregate product indicators

[0079]

[0080] Table 4 Analysis of pollutant components in light aggregate (mg / kg)

[0081]

[0082] Table 5 Analysis of leachable heavy metal content in lightweight aggregate (mg / L)

[0083]

[0084] It can be seen from the above results that, through the method for harmless utilization of cyanide tailings provided in this example, the density grade of the light aggregate prepared by mixing cyanide tailings, municipal sludge, fly ash and purifier at high temperature is 800, which meets the light aggregate product index requirements in "Light Aggregate and Its Test Methods" (GB17431.1-2010).

[0085] Example 2

[0086] Examples 2-4 and Comparative Examples 1 to 7 and Control Group 1 respectively provide a method for harmless utilization of cyanide tailings. Compared with Example 1, the difference is that the mass ratios of cyanide tailings, municipal sludge, fly ash and purifier in step S2 are changed respectively. The corresponding parameters corresponding to each embodiment and comparative example are shown in Table 6. The remaining steps and parameters are consistent with Example 1 and are not repeated here.

[0087] Table 6 Process parameters of Examples 2-4, Comparative Examples 1-7, and Control Group 1

[0088] project Cyanide tailings Municipal sludge Fly ash Purifier Example 1 50％ 30％ 20％ 10％ Example 2 70％ 10％ 10％ 10％ Example 3 65％ 30％ 5％ 10％ Example 4 50％ 30％ 20％ 5％ Comparative Example 1 40％ 30％ 20％ 10％ Comparative Example 2 75％ 5％ 20％ 10％ Comparative Example 3 50％ 40％ 10％ 10％ Comparative Example 4 67.5％ 30％ 2.5％ 10％ Comparative Example 5 50％ 20％ 30％ 10％ Comparative Example 6 50％ 30％ 20％ 3％ Comparative Example 7 50％ 30％ 20％ 15％ Control group 1 100％ 0％ 0％ 0％

[0089] Lightweight aggregates were prepared according to the methods provided in Examples 1-4 and Comparative Examples 1-7, and the products and harmful substances of the light aggregates were tested. The product properties are shown in Table 7, and the harmful substance test results are shown in Tables 8 and 9.

[0090] Table 7 Lightweight aggregate product indicators of Examples 2-4, Comparative Examples 1-7, and Control Group 1

[0091]

[0092]

[0093] Table 8 Analysis of pollutant components in light aggregate of Examples 2-4, Comparative Examples 1-7 and Control Group 1 (mg / kg)

[0094]

[0095]

[0096] Table 9 Analysis of leached heavy metal content of lightweight aggregates of Examples 2-4, Comparative Examples 1-7 and Control Group 1 (mg / L)

[0097]

[0098] It can be seen from Tables 7 to 9 that the parameters such as the mass ratio of cyanidation tailings, municipal sludge and fly ash in step S2 and the amount of purifier added will affect the product performance and compliance of light aggregate. Cyanidation tailings contain rich inorganic substances such as silicon aluminum oxides, which constitute the raw materials that meet the preparation of light aggregate; adding municipal sludge and other organic matter containing organic carbon to cyanidation tailings for balance adjustment is not only low-cost and waste treatment, but also helps to form a porous structure under high temperature conditions and reduce the packing density of light aggregate; the addition of fly ash improves the raw material composition of cyanidation tailings to a certain extent, and fluxing ensures the strength of light aggregate; the addition of purifiers is in a high temperature environment, which helps the volatilization of heavy metals in the raw materials and can ensure that the harmful substances in the product meet the standards.

[0099] Comparison of the examples shows that the amount of municipal sludge and fly ash added will affect the performance of the product. When the amount of municipal sludge added is less than 10% of the mixed components, the porous structure in the light aggregate is insufficient, resulting in an increase in the bulk density and an increase in the density grade of the light aggregate. When the amount of municipal sludge added is greater than 40% of the mixed components, the bulk density of the light aggregate is small, with a density grade of 800, but excessive organic matter will result in substandard cylinder pressure strength and failure to meet product standards. When the amount of fly ash added is less than 5%, the cylinder pressure strength of the light aggregate is less than 1.2, which fails to meet product standards. When the amount of fly ash added is greater than 20%, the cylinder pressure strength of the light aggregate is higher, but its bulk density is higher, with a density grade of 1100. When the amount of purifier added is less than 5%, the purification effect is poor, and the content of lead in the product exceeds the standard. When the amount of purifier added is greater than 10%, the product is stable and meets the standard, but its operating cost increases. Therefore, it is not recommended to add more than 10%.

[0100] Examples 5-6 and Comparative Examples 8-11 and Control Group 2

[0101] Examples 5-6, Comparative Examples 8-11 and Control Group 2 respectively provide a method for harmless utilization of cyanide tailings. Compared with Example 1, the difference is that the preheating temperature and preheating time in step S3 are changed respectively. The corresponding parameters corresponding to each embodiment and comparative example are shown in Table 10. The remaining steps and parameters are consistent with Example 1 and are not repeated here.

[0102] Table 10 Process parameters of Example 1, Examples 5-6, Comparative Examples 8-11 and Control Group 2

[0103] project Step 4 Preheating temperature (℃) Step 4 Preheating time (min) Example 1 400 30 Example 5 600 30 Example 6 400 60 Comparative Example 8 350 10 Comparative Example 9 650 10 Comparative Example 10 600 20 Comparative Example 11 600 70 Control group 2 0 0

[0104] Light aggregate was prepared according to the method provided in Example 1, Examples 5 to 6 and Comparative Examples 8 to 11, and the packing density of the light aggregate was tested. The test results of the packing density of the light aggregate are shown in Table 11.

[0105] Table 11 Lightweight aggregate product indicators of Example 1, Examples 5-6 and Comparative Examples 8-11

[0106]

[0107] It can be seen from Table 11 that the preheating temperature and preheating time in step S3 affect the bulk density and water absorption of the light aggregate, respectively, and ultimately affect the product performance of the light aggregate. When the preheating temperature is lower than 400°C, the organic matter and water in the mixed raw materials are not fully activated, the bulk density of the light aggregate after sintering increases, and the density grade of the light aggregate increases. When the preheating temperature is higher than 600°C, the fluxing substances in the mixed raw materials take effect in advance, which also leads to an increase in the bulk density of the light aggregate. When the preheating time is lower than 30 minutes, the organic matter and water in the mixed raw materials are not fully activated, the bulk density of the light aggregate is high, and the density grade increases. When the preheating time is higher than 60 minutes, the water absorption rate of the light aggregate decreases, but considering that the preheating time is too long, the economic effect is poor, so it is not recommended.

[0108] Examples 7-8 and Comparative Examples 12-15

[0109] Examples 7-8 and comparative examples 12-15 respectively provide a method for harmless utilization of cyanide tailings. Compared with Example 1, the difference is that the sintering temperature and sintering time in step S3 are respectively changed. The corresponding parameters of each embodiment and comparative example are shown in Table 10. The remaining steps and parameters are consistent with Example 1 and are not repeated here.

[0110] Table 10 Process parameters of Examples 1, 7-8 and Comparative Examples 12-15

[0111]

[0112]

[0113] Light aggregate was prepared according to the method provided in Example 1, Examples 7 to 8 and Comparative Examples 12 to 15, and the packing density of the light aggregate was tested. The test results of the packing density of the light aggregate are shown in Table 11.

[0114] Table 11 Lightweight aggregate product indicators of Examples 1, 7-8 and Comparative Examples 12-15

[0115]

[0116] It can be seen from Table 11 that the sintering temperature and sintering time in step S3 will affect the product performance of the light aggregate. When the sintering temperature is lower than 1000°C, the sintering and melting reaction of the light aggregate is incomplete, and the internal pore structure is not fully formed, resulting in a high bulk density of the product. When the sintering temperature is higher than 1200°C, the light aggregate is excessively melted, and some separation is difficult. The collapse of some pores causes a decrease in the cylinder pressure strength. The sintering temperature is too high, the energy consumption is high, and the operating cost increases. When the sintering time is lower than 20 minutes, the internal sintering of the light aggregate is insufficient, and the prepared light aggregate cylinder pressure strength is insufficient and does not meet the product standard. When the sintering time is higher than 60 minutes, the extension of the sintering time will make the internal structure of the light aggregate denser, the water absorption rate is lower, and the cylinder pressure strength increases, but the bulk density of the light aggregate will also increase accordingly. In addition, the sintering temperature is too high, the energy consumption is high, and the operating cost increases.

[0117] Comparative Example 16

[0118] Comparative Example 16 provides a method for harmless utilization of cyanide tailings. Compared with Example 1, the difference is that the atmosphere during preheating, sintering and cooling in step S3 is changed. The corresponding parameters corresponding to Example 1 and Comparative Example 16 are shown in Table 12. The remaining steps and parameters are consistent with Example 1 and are not repeated here.

[0119] Table 12 Process parameters of Example 1 and Comparative Example 16

[0120] project Sintering atmosphere Air flow rate (L / min) Example 1 Nitrogen 1.0 Comparative Example 16 Air 1.0

[0121] Light aggregate was prepared according to the method provided in Example 1 and Comparative Example 16, and the packing density of the light aggregate was tested. The test results of the packing density of the light aggregate are shown in Table 13.

[0122] Table 13 Lightweight aggregate product indicators of Example 1 and Comparative Example 16

[0123]

[0124] It can be seen from Table 13 that the atmosphere during preheating, sintering and cooling in step S3 will significantly affect the product performance of light aggregate. The municipal sludge in the light aggregate raw material contains organic carbon. In the inert gas atmosphere, the organic matter undergoes anaerobic cracking, continuously produces gas, and escapes from the light aggregate. In this process, the anaerobic pyrolysis of the organic matter produces gas to form pores inside the light aggregate. The prepared light aggregate has a relatively low bulk density, a high cylinder pressure strength, and a lower water absorption rate. In the air atmosphere, the organic matter undergoes oxidative decomposition in an aerobic environment, and the oxidation reaction is violent. A large amount of gas causes the collapse of some pores, which in turn causes an increase in bulk density and a decrease in cylinder pressure strength, and the water absorption rate is also relatively high.

[0125] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and embodiments having substantially the same structure as the technical idea and exerting the same effects within the scope of the technical solution of the present application are all included in the technical scope of the present application. In addition, within the scope of the subject matter of the present application, various modifications that can be thought of by those skilled in the art to the embodiments and other methods of combining some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A method for harmless utilization of cyanide tailings, characterized in that: The steps include: S1. Drying and grinding cyanide tailings, municipal sludge, fly ash and purifier respectively; S2, mixing the cyanide tailings, the municipal sludge, the fly ash, and the purifier in a predetermined proportion, adding water and stirring to prepare pellets; and then drying the pellets; S3. Preheating, sintering and cooling the dried pellets in sequence to obtain harmless light aggregates.

2. The method for harmless utilization of cyanide tailings according to claim 1, characterized in that: In step S3, during the preheating, sintering and cooling process, an inert gas is used as a protective atmosphere; the rate of filling the inert gas in step S3 is 0.5-3.0 L / min; the inert gas includes but is not limited to nitrogen.

3. The method for harmless utilization of cyanide tailings according to claim 2, characterized in that: The specific process of preheating, sintering and cooling in step S3 is as follows: The preheating process is as follows: in a blast furnace, the temperature is raised to 400°C to 600°C at a rate of 10°C / min to 30°C / min, and kept warm for 30min to 60min for preheating; then the temperature is raised to 1000°C to 1200°C at a rate of 5°C / min to 20°C / min, and sintered for 20min to 60min; and finally, the temperature is naturally cooled with the furnace temperature.

4. The method for harmless utilization of cyanide tailings according to claim 1, characterized in that: In step S2, the predetermined ratio is: the mass ratio of cyanide tailings: municipal sludge: fly ash is 50% to 70%: 10% to 30%: 5% to 20%; the added amount of the purifier is 5% to 10% of the total mass of cyanide tailings, municipal sludge and fly ash.

5. The method for harmless utilization of cyanide tailings according to claim 4, characterized in that: In step S2, the amount of water added is 22% to 27% of the total mass of cyanide tailings, municipal sludge, fly ash and purifier.

6. The method for harmless utilization of cyanide tailings according to claim 5, characterized in that: The purifier includes one or a combination of sodium chloride, calcium chloride and magnesium chloride.

7. The method for harmless utilization of cyanide tailings according to claim 1, characterized in that: In step S1, the cyanide tailings, the municipal sludge, the fly ash, and the purifier are ground to a particle size of 200 mesh or more.

8. The method for harmless utilization of cyanide tailings according to claim 1, characterized in that: In step S2, the pellets need to be aged before drying; the aging time is 0.5h to 2h; and the particle size of the pellets is 10mm to 15mm.

9. The method for harmless utilization of cyanide tailings according to claim 1, characterized in that: The drying process in step S3 is: drying at 100° C. to 110° C. for 1 h to 4 h.

10. The method for harmless utilization of cyanide tailings according to claim 3, characterized in that: In step S3, the blast furnace includes a box-type resistance furnace.

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