Method for preparing basalt-like aggregate by controlling oxygen fugacity of cyanide tailings

Abstract

The present application relates to the technical field of solid waste resource utilization, and discloses a method for preparing basalt-like aggregate from cyanide tailings by oxygen fugacity regulation. The method comprises the following steps: mixing cyanide tailings and flotation tailings under the assistance of ultrasonic waves; obtaining green granules by mechanical shearing and granulation; establishing precise temperature gradient and gas-phase O2 content gradient in a countercurrent calcination kiln through multi-parameter coordinated control, precisely regulating the oxygen fugacity of each temperature zone system within the thermodynamic window required for the directional generation of basalt-like mineral phases, and obtaining basalt-like aggregate; and after dust removal and heat exchange, the sulfur-containing flue gas generated by sintering enters an absorption tower to co-produce high-quality sodium metabisulfite. The present application realizes the harmless disposal and resource utilization of cyanide tailings, the road performance of the obtained basalt-like aggregate meets the requirements of high-grade highway asphalt pavement, and the high-value utilization of sulfur resources is realized, which has significant economic and environmental benefits.

Description

Technical Field

[0001] This invention relates to the field of solid waste resource utilization technology, specifically a method for preparing basalt-like aggregate from cyanide tailings with oxygen fugacity control. Background Technology

[0002] Cyanide tailings are hazardous waste generated during gold production. Currently, gold smelting enterprises pre-treat cyanide tailings and then use flotation to enrich FeS2 in the tailings, obtaining high-sulfur cyanide tailings and low-sulfur cyanide tailings. The high-sulfur cyanide tailings are sold as pyrite concentrate, while the low-sulfur cyanide tailings mainly consist of SiO2, Al2O3, and residual CN. - Pyrite, as well as heavy metals such as copper, lead, cadmium, and chromium, are difficult to utilize comprehensively, and are currently mainly stored in stockpiles.

[0003] In the field of road engineering, there are strict mechanical performance requirements for coarse aggregates used in asphalt pavements of high-grade highways. Natural basalt, with its mineral composition dominated by pyroxene and plagioclase, possesses excellent properties such as high-pressure crushing resistance, low abrasion value, and low water absorption, making it the preferred aggregate for high-grade highways. The formation of the pyroxene phase in natural basalt is closely related to the oxygen fugacity conditions during the magma cooling process. Under suitable oxygen fugacity conditions, iron is converted into Fe... 2+ To maintain its stable form, it preferentially enters the pyroxene lattice to form a CaMg(Fe)Si2O6 solid solution, endowing the aggregate with excellent mechanical properties. With the continuous growth in infrastructure construction demand, high-quality natural basalt mineral resources are becoming increasingly scarce, making the development of high-performance basalt-like artificial aggregates using solid waste as raw materials an important research direction.

[0004] However, existing sintering technologies for preparing aggregates from solid waste resources have the following drawbacks: Current sintering processes rely primarily on controlling the sintering temperature profile. Under the oxidizing atmosphere of traditional industrial sintering, it is difficult to form the pyroxene solid solution structure necessary for mimicking basalt mineral phases. This results in low pyroxene phase content in the finished aggregates, leading to significant differences in mechanical properties compared to natural basalt, making it difficult to meet the requirements for high-grade road aggregates. Furthermore, during the high-temperature sintering of cyanide tailings, cyanide decomposes thermally, and FeS2 oxidizes and decomposes simultaneously, releasing high-concentration SO2 flue gas. Both need to be treated simultaneously in the same flue gas treatment system, but their requirements for flue gas oxygen content are fundamentally contradictory: on the one hand, the complete detoxification of cyanide requires maintaining sufficient O2 content in the flue gas; on the other hand, the high-concentration SO2 resource-based preparation of sodium metabisulfite requires strict control of the O2 content in the flue gas entering the absorption tower to prevent the sodium sulfite intermediate generated during sodium carbonate absorption from being further oxidized into useless sodium sulfate by excessive O2, thereby ensuring the purity of the sodium metabisulfite product. The two constraints mentioned above are opposite in direction and mutually restrictive in terms of controlling the oxygen content in flue gas. There is no systematic solution in the existing technology. Usually, SO2 is only neutralized with alkali before being discharged, which not only wastes a lot of sulfur resources, but also generates secondary pollution of saline wastewater, thus restricting the economic benefits of comprehensive utilization of cyanide tailings.

[0005] In summary, existing technologies for the comprehensive utilization of artificial aggregates prepared from cyanide tailings suffer from several problems, including insufficient formation of basalt-like mineral phases due to the limited means of mineral phase control, and difficulty in coordinating the treatment of cyanide-containing flue gas with the high-value utilization of sulfur resources. There is an urgent need to provide an intensive and efficient comprehensive utilization method. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a method for preparing basalt-like aggregate from cyanide tailings with oxygen fugacity controlled, while simultaneously utilizing sintering flue gas to co-produce high-quality sodium metabisulfite under precise oxygen content control.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a method for preparing basalt-like aggregate from cyanide tailings with oxygen fugacity control, comprising the following steps: (1) Ultrasonic homogenization mixing: Cyanide tailings and flotation tailings are mixed at a mass ratio of 1:0.2~1, water is added to a moisture content of 12%~18%, and the mixture is put into a horizontal mixer equipped with an ultrasonic transducer array for wet mixing. The mixing time is 30~40 minutes to obtain the mixture. (2) Mechanical shearing granulation: The mixture is fed into the roller extrusion-crushing-screening combined device, and is extruded by the roller extruder to form a compact. After the compact is crushed twice, it is graded and screened by a double-layer vibrating screen (the screen holes are 8mm and 15mm respectively). Irregular angular raw material particles with a particle size of 8~15mm are collected. The mixture above and below the screen is returned to the extrusion process for recycling to obtain raw material particles. (3) Sintering in a calcining kiln: The raw material particles are calcined in a calcining kiln at a maximum temperature of 1150~1200℃ and the kiln running time is 40~60min. Through the coordinated control of the process, basalt-like aggregate and sulfur-containing flue gas are obtained. (4) Preparation of sodium metabisulfite from sulfur-containing flue gas: The sulfur-containing flue gas formed in step (3) with a gas phase O2 content of 0.5%~1% at the feed tail end is filtered by bag filter and cooled by heat exchange, and then enters the sodium carbonate absorption tower to produce sodium metabisulfite; the mass fraction of the sodium metabisulfite is ≥96.5%.

[0008] Preferably, the flotation tailings in step (1) are tailings generated during the gold beneficiation process, containing silicon, aluminum, potassium, calcium, sodium and magnesium elements; the mass fraction of FeS2 in the chemical composition of the mixture is 3.5%~7%.

[0009] Preferably, in step (1), the ultrasonic transducer array has an ultrasonic frequency of 20~80kHz and an ultrasonic power density of 0.5~3.0W / mL.

[0010] Preferably, in step (3), the calcining kiln is a calcining kiln in which the material direction and the flue gas direction are opposite. The raw material particles are fed from the kiln tail and the burner is located at the kiln head. Three online O2 analyzers and PID-controlled air intake regulating valves are set along the length of the kiln body, respectively located at the flue gas discharge pipe at the kiln tail end (feeding tail end), the sampling port (middle section) in the middle of the kiln body, and the burner area at the kiln head (discharge head end).

[0011] Preferably, the coordinated control of the process in step (3) specifically involves dividing the kiln into three temperature zones along the material movement direction: a low-temperature zone at the feed tail end, a reduction zone in the middle section, and a high-temperature sintering zone at the discharge head end. The temperature distributions of the low-temperature zone at the feed tail end, the reduction zone in the middle section, and the high-temperature sintering zone at the discharge head end are 350~600℃, 600~1000℃, and 1000~1200℃, respectively. The temperature distribution of each zone is achieved by jointly adjusting the burner heat load and the kiln running time. By adjusting the burner air-fuel ratio, the gas phase O2 content at the discharge head end is controlled to be 3%~5%. After the countercurrent flue gas is consumed step by step by oxygen-consuming reactions such as FeS2 decomposition and FeS oxidation along the process, the gas phase O2 content in the middle section decreases to 1%~2%, and the gas phase O2 content at the feed tail end decreases to 0.5%~1%.

[0012] Preferably, under the combined constraints of the temperature distribution and the gas phase O2 content in each of the above temperature zones, the fO2 distribution in each temperature zone reaches the following: Low-temperature zone at the feed tail end: The system fO2 is constrained by the FeS2 / FeS mineral phase equilibrium buffer and maintained in the low value range, lg(fO2 / atm) is -20~-15; under this condition, FeS2 decomposes step by step along the FeS2→FeS+S↑, S+O2→SO2↑ path, forming a microporous network along the mineral grain boundary inside the particles, releasing the sintering internal stress and preventing particle cracking; at the same time, SO2 is continuously released to provide sulfur source for step (4); In the mid-reduction zone: the gaseous O2 content, along with the FeS / Fe3O4 and Fe3O4 / Fe2O3 mineral phase equilibrium buffering effect, maintains the system's fO2 within a weakly reducing thermodynamic window, with lg(fO2 / atm) ranging from -10 to -8; some Fe... 3+ Directed reduction to active Fe 2 + The iron source required for the formation of pyroxene phase is continuously supplied to the high-temperature sintering zone at the discharge head. High-temperature sintering zone at the discharge head: The gas phase O2 content and high-temperature conditions together maintain the system's fO2 within a suitable oxidation window, with lg(fO2 / atm) ranging from -6 to -4; active Fe 2+ Under these fO2 conditions, it enters the pyroxene lattice and reacts with Ca. 2+ Mg 2+ The CaMg(Fe)Si2O6 pyroxene solid solution phase is formed synergistically; the plagioclase phase undergoes liquid-phase sintering and densification simultaneously.

[0013] In summary, this application includes at least one of the following beneficial technical effects: (1) Improved efficiency of the mixing process.

[0014] The cavitation effect generated by ultrasound produces local high-temperature and high-pressure micro-jets at the material particle interface, effectively breaking up agglomerates; the acoustic flow effect drives macroscopic convection of the slurry, promoting the microscopic uniform distribution of each component. The above synergistic effect can achieve good homogenization effect in a short time, which is better than the traditional aging process, eliminating the need for aging stockpiles and reducing the risk of leakage and dust caused by large-scale long-term storage of cyanide-containing hazardous waste.

[0015] (2) Multi-parameter collaborative control realizes precise directional generation of basalt mineral phases, resulting in excellent aggregate road performance.

[0016] By coordinating the control of multiple parameters such as burner heat load, air-fuel ratio and kiln running time, a precise temperature gradient and gas phase O2 content gradient are established in the kiln, and the fO2 of each temperature zone system is precisely controlled within the thermodynamic window required for the directional generation of basalt mineral phase.

[0017] The fO2 in the low-temperature zone at the feed tail end is maintained in the low value range. The decomposition of FeS2 in the raw material forms a uniformly distributed microporous network along the mineral grain boundary inside the particles, releasing the thermal stress accumulated during the heating process. This effectively prevents the particles from cracking due to stress concentration during the heating stage, significantly improving the yield. At the same time, FeS produced by the decomposition of FeS2 serves as a solid oxygen-consuming medium in the subsequent weak reducing atmosphere in the middle stage, continuously participating in O2 consumption. In the intermediate reduction zone, fO2 is maintained within a weak reduction window. Precise control of the burner's air-fuel ratio, combined with the synergistic effect of FeS solid-phase oxidation oxygen consumption, maintains the gas-phase O2 content in this zone at 1%–2%, corresponding to weak reduction thermodynamic conditions. Under these fO2 conditions, Fe… 3+ Directed reduction to active Fe 2+ , active Fe 2+ It accumulates in large quantities in the middle section, continuously providing a highly active iron source for the formation of the pyroxene phase at the first end of the subsequent discharge; In the high-temperature sintering zone at the discharge end, fO2 is maintained within a moderate oxidation window. This fO2 range highly corresponds to the geochemical oxygen fugacity conditions of the pyroxene phase formed during the crystallization of natural basalt magma. Under these conditions, active Fe... 2+ Entering the pyroxene lattice, with Ca 2+ Mg 2+ Together, they form a CaMg(Fe)Si2O6 pyroxene solid solution phase. At the same time, the plagioclase phase undergoes liquid-phase sintering and densification under a moderate oxidizing atmosphere, forming a microtexture in which the pyroxene and plagioclase phases coexist.

[0018] (3) By utilizing the precise control window of O2 content, sodium metabisulfite can be produced from sulfur-containing flue gas at high value.

[0019] Through precise multi-parameter linkage control, the O2 content of the flue gas is stably maintained within a precise window of 0.5%~1%. Within this window, the O2 content is sufficient to ensure the complete oxidation of residual organic matter, while effectively inhibiting the further oxidation of Na2SO3 to Na2SO4. After passing through bag filter dust collection and heat exchange cooling, the flue gas directly enters the sodium carbonate absorption tower. The resulting sodium metabisulfite product has a Na2S2O5 content ≥96.5%, meeting the requirements of superior grade in HG / T 2826-2008. Compared with the traditional alkaline neutralization treatment method, this method converts the sulfur resources in the flue gas into high-value-added chemical products, realizing a dual-track resource utilization path of "solid waste → aggregate + sulfur chemical products" in the hazardous waste sintering disposal process.

[0020] (4) Multifunctional coupling utilization of FeS2 component throughout the sintering process.

[0021] This invention repositions the inherent FeS2 in cyanide tailings from a "harmful impurity" traditionally considered to require "harmless treatment" into a "multifunctional thermosensitive coupling medium" that runs throughout the entire sintering process. It performs different functions sequentially in three consecutive stages: thermal decomposition at the low-temperature zone at the feed tail end forms a microporous network, improving aggregate yield; after conversion to FeS, it participates in solid-phase oxygen consumption in the mid-stage reduction zone, helping to maintain a weak reducing atmosphere and promoting Fe... 2+ Accumulation; the SO2 released throughout the process serves as a continuous sulfur source for the co-production of sodium metabisulfite. All three functions mentioned above are naturally achieved by the inherent components of the raw materials during sintering, without the need for additional mineral phase control additives. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] To better understand the above technical solutions, the following will provide a detailed explanation of the technical solutions in conjunction with specific embodiments.

[0024] Example 1 (1) Ultrasonic homogenization mixing: Cyanide tailings and flotation tailings were mixed at a mass ratio of 1:0.2. The flotation tailings were tailings generated during the gold beneficiation process and contained silicon, aluminum, potassium, calcium, sodium and magnesium. Water was added to a moisture content of 18% and the mixture was put into a horizontal mixer equipped with an ultrasonic transducer array for wet mixing. The ultrasonic frequency was set to 20kHz, the ultrasonic power density was 0.5W / mL, and the mixing time was 30min to obtain a mixture. The mass fraction of FeS2 in the chemical composition of the mixture was 3.5%. (2) Mechanical shearing granulation: The mixture is fed into the roller extrusion-crushing-screening combined device, and is extruded by the roller extruder to form a compact. After the compact is crushed twice, it is graded and screened by a double-layer vibrating screen (the screen holes are 8mm and 15mm respectively). Irregular angular raw material particles with a particle size of 8~15mm are collected. The mixture above and below the screen is returned to the extrusion process for recycling to obtain raw material particles. (3) Sintering in the calcining kiln: The calcining kiln is a calcining kiln in which the material flow direction is opposite to the flue gas flow direction. The raw material particles are fed from the kiln tail and the burner is located at the kiln head. Three online O2 analyzers and PID-controlled air intake regulating valves are installed along the length of the kiln body. They are located at the flue gas discharge pipe at the kiln tail end (feed tail end), the sampling port (middle section) in the middle of the kiln body, and the burner area at the kiln head (discharge head end). The raw material particles are calcined in the calcining kiln. The maximum temperature is 1200℃ and the kiln running time is 40 minutes. n, control the gas phase O2 content at the discharge head to be 3%, the gas phase O2 content in the middle section to be 1%, and the gas phase O2 content at the feed tail to be 0.5%, and then adjust lg(fO2 / atm) in the low temperature zone (350~600℃) at the feed tail to be -20, lg(fO2 / atm) in the middle reduction zone (600~1000℃) to be -10, and lg(fO2 / atm) in the high temperature sintering zone (1000~1200℃) at the discharge head to be -6, to obtain basalt-like aggregate and sulfur-containing flue gas; (4) Preparation of sodium metabisulfite from sulfur-containing flue gas: The sulfur-containing flue gas formed in step (3) with a gas phase O2 content of 0.5% at the feed tail end is filtered by bag filter and cooled by heat exchange before entering the sodium carbonate absorption tower to produce sodium metabisulfite.

[0025] Example 2 (1) Ultrasonic homogenization mixing: Cyanide tailings and flotation tailings are mixed at a mass ratio of 1:1. The flotation tailings are tailings generated during the gold beneficiation process and contain silicon, aluminum, potassium, calcium, sodium and magnesium. Water is added to a moisture content of 12% and the mixture is put into a horizontal mixer equipped with an ultrasonic transducer array for wet mixing. The ultrasonic frequency is set to 80kHz, the ultrasonic power density is 3W / mL, and the mixing time is 40min to obtain a mixture. The mass fraction of FeS2 in the chemical composition of the mixture is 7%. (2) Mechanical shearing granulation: The mixture is fed into the roller extrusion-crushing-screening combined device, and is extruded by the roller extruder to form a compact. After the compact is crushed twice, it is graded and screened by a double-layer vibrating screen (the screen holes are 8mm and 15mm respectively). Irregular angular raw material particles with a particle size of 8~15mm are collected. The mixture above and below the screen is returned to the extrusion process for recycling to obtain raw material particles. (3) Sintering in the calcining kiln: The calcining kiln is a calcining kiln in which the material flow direction is opposite to the flue gas flow direction. The raw material particles are fed from the kiln tail, and the burner is located at the kiln head. Three online O2 analyzers and PID-controlled air intake regulating valves are installed along the length of the kiln body, located at the flue gas discharge pipe at the kiln tail end (feed tail end), the sampling port (middle section) in the middle of the kiln body, and the burner area at the kiln head (discharge head end), respectively. The raw material particles are calcined in the calcining kiln, with a maximum temperature of 1150℃ and a kiln running time of 60 minutes. The gas phase O2 content at the discharge head is controlled to be 5%, the gas phase O2 content in the middle section is 2%, and the gas phase O2 content at the feed tail end is 1%. Then, the lg(fO2 / atm) in the low temperature zone (350~600℃) at the feed tail end is adjusted to -15, the lg(fO2 / atm) in the middle reduction zone (600~1000℃) is adjusted to -8, and the lg(fO2 / atm) in the high temperature sintering zone (1000~1150℃) at the discharge head end is adjusted to -4 to obtain basalt-like aggregate and sulfur-containing flue gas. (4) Preparation of sodium metabisulfite from sulfur-containing flue gas: The sulfur-containing flue gas formed in step (3) with a gas phase O2 content of 1% at the feed tail end is filtered by bag filter and cooled by heat exchange before entering the sodium carbonate absorption tower to produce sodium metabisulfite.

[0026] Example 3 (1) Ultrasonic homogenization mixing: Cyanide tailings and flotation tailings were mixed at a mass ratio of 1:0.6. The flotation tailings were tailings generated during the gold beneficiation process and contained silicon, aluminum, potassium, calcium, sodium and magnesium. Water was added to a moisture content of 15% and the mixture was put into a horizontal mixer equipped with an ultrasonic transducer array for wet mixing. The ultrasonic frequency was set to 50kHz, the ultrasonic power density was 1.5W / mL, and the mixing time was 35min to obtain a mixture. The mass fraction of FeS2 in the chemical composition of the mixture was 5.5%. (2) Mechanical shearing granulation: The mixture is fed into the roller extrusion-crushing-screening combined device, and is extruded by the roller extruder to form a compact. After the compact is crushed twice, it is graded and screened by a double-layer vibrating screen (the screen holes are 8mm and 15mm respectively). Irregular angular raw material particles with a particle size of 8~15mm are collected. The mixture above and below the screen is returned to the extrusion process for recycling to obtain raw material particles. (3) Sintering in the calcining kiln: The calcining kiln is a calcining kiln in which the material flow direction is opposite to the flue gas flow direction. The raw material particles are fed from the kiln tail and the burner is located at the kiln head. Three online O2 analyzers and PID-controlled air intake regulating valves are installed along the length of the kiln body. They are located at the flue gas discharge pipe at the kiln tail end (feed tail end), the sampling port (middle section) in the middle of the kiln body, and the burner area at the kiln head (discharge head end). The raw material particles are calcined in the calcining kiln. The maximum temperature is 1170℃ and the kiln running time is 50min. The gas phase O2 content at the discharge head is controlled to be 4%, the gas phase O2 content in the middle section is 1.5%, and the gas phase O2 content at the feed tail end is 0.75%. Then, the lg(fO2 / atm) in the low temperature zone (350~600℃) at the feed tail end is adjusted to -17, the lg(fO2 / atm) in the middle reduction zone (600~1000℃) is adjusted to -9, and the lg(fO2 / atm) in the high temperature sintering zone (1000~1170℃) at the discharge head end is adjusted to -5, so as to obtain basalt-like aggregate and sulfur-containing flue gas. (4) Preparation of sodium metabisulfite from sulfur-containing flue gas: The sulfur-containing flue gas formed in step (3) with a gas phase O2 content of 0.75% at the feed tail end is filtered by bag filter and cooled by heat exchange before entering the sodium carbonate absorption tower to produce sodium metabisulfite.

[0027] Comparative Example 1 Compared with Example 3, the difference in this comparative example is that in step (3), the gas phase O2 content at the discharge head, middle section and feed tail is controlled at 8% throughout the process, and the lg(fO2 / atm) of each temperature zone is always in the range of -3 to -1, so as to obtain basalt-like aggregate and sulfur-containing flue gas.

[0028] Comparative Example 2 Compared with Example 3, the difference in this comparative example is that in step (3), the gas phase O2 content at the discharge head is controlled to be 2%, the gas phase O2 content in the middle section is 0.8%, and the gas phase O2 content at the feed tail is 0.3%. Then, the lg(fO2 / atm) of the low temperature zone at the feed tail is adjusted to -25, the lg(fO2 / atm) of the middle reduction zone is adjusted to -12, and the lg(fO2 / atm) of the high temperature sintering zone at the discharge head is adjusted to -7, so as to obtain basalt-like aggregate and sulfur-containing flue gas.

[0029] Comparative Example 3 The difference between this comparative example and Example 3 is that in step (1), the mass fraction of FeS2 in the chemical composition of the mixture is 3%.

[0030] Table 1: Performance of each embodiment and comparative example product.

[0031]

[0032] Comparison of Comparative Example 1 and Example 3: Under high O2 atmosphere conditions throughout the process, fO2 in each temperature zone of the kiln remained in the strong oxidation range, and the weak reduction thermodynamic conditions in the middle section could not be established at all. 3+ Continuously stable, active Fe 2+ The accumulation was almost zero, and the pyroxene phase content in the sintered product was only 13%, which was 32.5% of that in Example 3. The three indicators of aggregate crushing value, Los Angeles abrasion value and water absorption rate did not meet the requirements of JTGF40-2004. The gas phase O2 at the feed tail end was as high as 8%, and after entering the sodium carbonate absorption tower, a large amount of Na2SO3 was oxidized to Na2SO4, and the Na2S2O5 content was only 87.4%. The sodium metabisulfite product was also unqualified.

[0033] Comparison of Example 2 and Example 3: Under low O2 atmosphere conditions throughout the process, the lg(fO2 / atm) in the high-temperature sintering zone at the discharge end drops to -7, deviating from the optimal thermodynamic window for the pyroxene phase. The appropriate oxidizing atmosphere required for the liquid phase sintering of the plagioclase phase is lacking. Iron remains in the glass phase in the form of FeO and does not enter the pyroxene lattice in a directional manner. The pyroxene phase content is only 24%, and the densification degree of the plagioclase phase is poor. The three indicators of aggregate crushing value, Los Angeles abrasion value, and water absorption rate do not meet the requirements of JTGF40-2004. More importantly, the gas phase O2 content at the feed tail end is only 0.3%, which may lead to the inability of cyanide-containing flue gas HCN to be fully oxidized and decomposed, posing a significant environmental safety risk.

[0034] Comparison of Example 3 and Example 3: Under the same O2 control parameters as Example 3, because the FeS2 content of the mixture decreased to 3%, the oxygen consumption of the FeS solid phase in the middle section was insufficient. Under the same air-fuel ratio setting, the solid phase buffer support of the weak reducing atmosphere in the middle section was significantly weakened, and the active Fe... 2+ The accumulation was reduced, with the pyroxene phase content at only 26%, compared to 65% in Example 3. The aggregate crushing value, Los Angeles abrasion value, and water absorption rate all failed to meet the requirements of JTGF40-2004. This comparative example demonstrates that the setting of the lower limit for the FeS2 content in the mixture has sufficient technical basis. FeS2 not only provides a sulfur source for SO2 but also serves as a solid-phase buffer medium to maintain a weakly reducing atmosphere in the intermediate stage; both factors jointly determine the rationality of the FeS2 content range.

[0035] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0036] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

[0037] Those skilled in the art should understand that the above descriptions are merely several specific embodiments of the present invention, and not all embodiments. It should be noted that many modifications and improvements can be made by those skilled in the art, and all modifications or improvements not exceeding the scope of the claims should be considered within the protection scope of the present invention.

Claims

1. A method for preparing basalt-like aggregate from cyanide tailings with oxygen fugacity controlled, characterized in that, Includes the following steps: (1) Ultrasonic homogenization mixing: Cyanide tailings and flotation tailings are mixed together, water is added to a moisture content of 12%~18%, and the mixture is put into a horizontal mixer equipped with an ultrasonic transducer array for wet mixing. The mixing time is 30~40 minutes to obtain the mixture. (2) Mechanical shearing granulation: The mixture is fed into the roller extrusion-crushing-screening combined device, and is extruded by the roller extruder to form a compact. After the compact is crushed twice, it is graded and screened by a double-layer vibrating screen (the screen holes are 8mm and 15mm respectively). Irregular angular raw material particles with a particle size of 8~15mm are collected. The mixture above and below the screen is returned to the extrusion process for recycling to obtain raw material particles. (3) Sintering in a calcining kiln: The raw material particles are calcined in a calcining kiln at a maximum temperature of 1150~1200℃ for 40~60 minutes. The kiln is divided into three temperature zones along the material movement direction: a low-temperature zone at the feed end, a reduction zone in the middle section, and a high-temperature sintering zone at the discharge end. The temperature distributions of the three zones are 350~600℃, 600~1000℃, and 1000~1200℃, respectively. The gaseous O2 content at the discharge end is... The amount is 3%~5%, the gas phase O2 content in the middle section decreases to 1%~2%, and the gas phase O2 content at the feed tail end decreases to 0.5%~1%; the fO2 in each temperature zone reaches the following distribution: lg(fO2 / atm) in the low temperature zone at the feed tail end is -20~-15, lg(fO2 / atm) in the middle reduction zone is -10~-8, and lg(fO2 / atm) in the high temperature sintering zone at the discharge head end is -6~-4, thus obtaining basalt-like aggregate and sulfur-containing flue gas; (4) Preparation of sodium metabisulfite from sulfur-containing flue gas: The sulfur-containing flue gas formed in step (3) with a gas phase O2 content of 0.5%~1% at the feed tail end is filtered by bag filter and cooled by heat exchange, and then enters the sodium carbonate absorption tower to produce sodium metabisulfite; the mass fraction of the sodium metabisulfite is ≥96.5%.

2. The method for preparing basalt-like aggregate from cyanide tailings with oxygen fugacity control according to claim 1, characterized in that, The flotation tailings in step (1) are tailings generated during the gold beneficiation process, containing silicon, aluminum, potassium, calcium, sodium and magnesium elements; the mass fraction of FeS2 in the chemical composition of the mixture is 3.5%~7%.

3. The method for preparing basalt-like aggregate from cyanide tailings with oxygen fugacity control according to claim 1, characterized in that, In step (1), the ultrasonic transducer array has an ultrasonic frequency of 20~80kHz and an ultrasonic power density of 0.5~3.0W / mL.

4. The method for preparing basalt-like aggregate from cyanide tailings with oxygen fugacity control according to claim 1, characterized in that, In step (3), the calcining kiln is a calcining kiln in which the material direction and the flue gas direction are opposite. The raw material particles are fed from the kiln tail and the burner is located at the kiln head. Three online O2 analyzers and PID-controlled air intake regulating valves are set along the length of the kiln body, respectively located at the flue gas discharge pipe at the kiln tail end (feed tail end), the sampling port (middle section) in the middle of the kiln body, and the burner area at the kiln head (discharge head end).

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