Cyanide tailings roasting and resource utilization process

Abstract

The cyanide tailings roasting and resource utilization process includes cyanide tailings pretreatment and roasting, flue gas cascade separation and utilization, sodium sulfite preparation, fine grinding of roasting slag and secondary cyanide leaching of gold, SO2 de-cyanation treatment of secondary cyanide tailings, preparation of de-cyanation tailings for non-burning bricks and full-process closed-loop control, specifically including six process steps and conditions, which can realize harmless disposal of cyanide tailings, cascade high-value utilization of flue gas SO2, secondary efficient recovery of gold resources and full resource utilization of solid waste, forming a closed loop of "roasting-gold extraction-de-cyanation-resource utilization", thereby reducing the processing cost, improving the environmental protection and economic benefits and the like.

Description

Technical Field

[0001] This invention relates to the field of cyanide tailings treatment and resource recovery technology, and in particular to a process for the synergistic resource utilization of cyanide tailings roasting. Background Technology

[0002] Cyanide gold extraction technology is widely used in the gold smelting industry due to its high gold recovery rate and simple process. However, this process generates a large amount of cyanide tailings. These tailings contain highly toxic cyanides and heavy metal ions, and are classified as hazardous waste. Direct storage not only occupies a large amount of land but also easily leads to environmental and safety hazards such as leachate leakage and dam failure. At the same time, a certain amount of refractory gold remains in the tailings, which can be recovered by roasting. However, the roasting process releases SO2-containing flue gas. If not effectively treated, this will not only waste resources but also pollute the atmosphere.

[0003] Currently, existing cyanide tailings treatment processes have several shortcomings: First, the roasting process is poorly controlled, easily leading to over- or under-roasting, resulting in incomplete cyanide breakdown, insufficient SO2 release, or sintering and coking of the roasting slag, affecting subsequent gold extraction. Second, roasting flue gas is mostly directly desulfurized without cascade utilization, resulting in low sulfur resource utilization efficiency, and impurities in the flue gas easily lead to low purity of desulfurization byproducts. Third, the cyanide removal process for tailings after cyanide leaching is simplistic, with insufficient removal efficiency, and the solid waste after cyanide removal is not fully disposed of, still posing a risk of stockpiling. Fourth, the entire process does not form a closed-loop cycle, with wastewater, waste residue, and waste gas being disposed of separately, resulting in poor economic efficiency and significant pressure to meet environmental standards. Fifth, the process has limited adaptability, making it difficult to simultaneously meet the dual requirements of deep cyanide removal from high-cyanide-concentration tailings and efficient recovery of low-grade gold, with prominent issues of equipment corrosion and catalyst loss.

[0004] Unable to resolve the aforementioned issues, several patents have been published, including CN107354307B, "A method for environmentally friendly extraction of gold and other metals from raw ore or cyanide tailings without tailings and for brick making." This method involves first removing cyanide, then selecting sulfur, and finally using the tailings to make bricks. However, this method does not involve the cascade resource utilization of roasting flue gas, and the cyanide removal relies on ammonium halide decyanating agents, resulting in high costs. It also fails to address the impact of roasting conditions on gold extraction efficiency. Utility model patent CN214990511U, authorized for publication, discloses a sulfur dioxide pressurized pre-oxidation cyanide-breaking system, which only optimizes the cyanide-breaking equipment and cannot achieve the coordinated resource utilization of flue gas, solid waste, and valuable metals.

[0005] Therefore, it is of great significance to develop a process for the synergistic resource utilization of cyanide tailings roasting. Summary of the Invention

[0006] The objective of this invention is to overcome the shortcomings of existing technologies and provide a synergistic resource utilization process for cyanide tailings roasting. This process enables the harmless disposal of cyanide tailings, the tiered high-value utilization of flue gas SO2, the secondary and efficient recovery of gold resources, and the full resource utilization of solid waste, forming a closed-loop cycle of "roasting-gold extraction-cyanide removal-resource utilization". This reduces processing costs and improves environmental and economic benefits.

[0007] The objective of this invention is achieved through the following technical solution:

[0008] The cyanide tailings roasting and co-processing resource utilization technology includes cyanide tailings pretreatment and roasting, flue gas cascade utilization, sodium sulfite preparation, roasting slag fine grinding and secondary cyanide leaching for gold, secondary cyanide tailings SO2 treatment, cyanide removal treatment of cyanide tailings to prepare non-fired bricks, and closed-loop management of the entire process. Specifically, it includes the following process steps and conditions:

[0009] S1. Pretreatment and roasting of cyanide tailings: The cyanide tailings are dried sequentially to a moisture content of less than 8%, pre-screened to remove large impurities larger than 5cm, and then fed into a rotary kiln for roasting. The roasting conditions are controlled at 600~750℃, oxidizing atmosphere, roasting time of 1.5~3h, and material layer thickness of 5~10cm. During the roasting process, cyanide ions are pyrolyzed and destroyed, sulfur components are oxidized and release SO2 flue gas, and gold minerals in the roasting slag are dissociated and activated. The flue gas generated by roasting is sequentially treated by cyclone dust collector, bag filter dust collector, rapid cooling and washing, and demisting and arsenic and fluorine removal to remove dust, heavy metals, arsenic and fluorine and other impurities from the flue gas, resulting in purified SO2 flue gas. At the same time, a waste heat recovery device is installed to recover the high-temperature flue gas and the waste heat of the kiln. The generated steam is used for subsequent leaching insulation and sodium sulfite evaporation and crystallization processes.

[0010] S2. Cascaded diversion and utilization of flue gas: The SO2 flue gas purified in step S1 is intelligently diverted, with 50-80% of the flue gas sent to the sodium sulfite preparation system and the remaining flue gas sent to the cyanide tailings decyanation system. During the diversion process, the flue gas distribution ratio is dynamically adjusted according to the cyanide concentration and processing volume of the subsequent decyanation tailings to ensure that the amount of SO2 required for decyanation matches the amount of flue gas supplied.

[0011] S3. Sodium sulfite preparation: The SO2 flue gas diverted from step S2 to the sodium sulfite preparation system is fed into the absorption tower and contacted countercurrently with the soda ash or caustic soda absorbent. The absorption pH is controlled at 6.5~7.5, the liquid-to-gas ratio at 8~12 L / m³, and the absorption temperature at 30~45℃. After absorption, the gas is purified by wet ion exchange resin to remove impurities such as calcium and magnesium, and then deeply decolorized by activated carbon. It is then sent to the evaporator crystallizer, where the residual heat recovered in step S1 is used to evaporate and crystallize at 60~80℃ to obtain sodium sulfite product and crystallization mother liquor. 60~80% of the crystallization mother liquor is returned to the absorption tower for recycling, and the remaining part is further evaporated to produce sodium sulfate, achieving zero discharge of waste liquid. A final-stage alkaline absorption tower is added to the tail gas of the absorption tower to capture trace amounts of SO2, and the absorbent is reused in the main absorption system.

[0012] S4. Fine grinding of roasted slag and secondary cyanide leaching: The roasted slag produced in step S1 is fed into a staged grinding and classification system that links a ball mill and a spiral classifier. It undergoes coarse grinding, classification, and fine grinding in sequence. The fineness of the slurry after fine grinding is controlled to be 85-95% of the particles being -200 mesh. The finely ground slurry is then fed into a cyanide leaching tank, where sodium cyanide, an alkali regulator, and a leaching aid are added. The concentration of sodium cyanide is controlled to be 0.05-0.12%, the pH of the slurry to be 10-11, the leaching time to be 24-48 hours, and the slurry concentration to be 40%-50%. Activated carbon is added during the leaching process for pre-adsorption to improve gold recovery efficiency. After leaching, gold in the leaching solution is recovered through a carbon adsorption process. The resulting secondary cyanide tailings slurry is then sent to a decyanation system for further processing.

[0013] S5. SO2 decyanation treatment of secondary cyanide tailings: The secondary cyanide tailings slurry generated in step S4 is sent to the decyanation reaction tank, and the SO2 flue gas diverted in step 2 is introduced. The SO2-air oxidation process is used for decyanation. After decyanation, the slurry is sent to a thickener and a filter press for dewatering. The moisture content of the filter cake is controlled to be 15-25%. The decyanation tailings are returned to the cyanide leaching process.

[0014] S6. Preparation of non-fired bricks from decyanated tailings: The tailings after decyanation in step S5 are used as the main raw material, combined with coarse aggregate, fly ash and slag, and the particle size distribution is optimized. The content of decyanated tailings is 60-80%. Cement binder and heavy metal passivating agent are added, and after being mixed evenly, they are sent to a high-pressure molding machine for molding. The molding pressure is 15-25 MPa. The molded brick blanks are sent to a steam curing chamber and cured at 80-100℃ for 8-12 hours to obtain the finished non-fired bricks.

[0015] S7. Closed-loop management of the entire process: The dust collected by the bag filter in step S1 is returned to the rotary kiln roasting system to recover valuable metals. The tailings of the decyanation in step S5, the condensate from the salt production in step S3, and the flue gas scrubbing water in step S1 are all recycled and reused to achieve zero wastewater discharge.

[0016] Compared with the prior art, the innovative points, advantages, and effects of this invention are as follows:

[0017] (1) By using roasting pyrolysis to break down cyanide and SO2-air oxidation to remove cyanide, combined with alkaline washing liquid to deeply remove arsenic, fluorine and heavy metals, the environmental safety hazards of cyanide tailings are completely eliminated, and the requirements for harmless disposal of hazardous waste are met.

[0018] (2) Optimize the flue gas diversion ratio, first prepare high-purity sodium sulfite product, and use the remaining flue gas for tailings decyanation to avoid resource waste and air pollution; recover the crystallization mother liquor to produce sodium sulfate, realizing full utilization of sulfur resources and zero discharge of waste liquid. Precisely control the fineness of staged grinding, and combine it with coconut shell activated carbon pre-adsorption with specific parameters and compound leaching aid to solve the problem of gold mineral encapsulation, greatly improve the efficiency of secondary gold leaching, and increase the company's resource benefits.

[0019] (3) The cyanide-removed tailings are used to prepare non-fired bricks with a high admixture content of 60%~80%. Combined with an optimized aggregate and cementitious material system, the product strength reaches MU15 grade or above, replacing traditional stockpiling and forming a "tailings-building materials" circular chain, saving land resources. Wastewater and dust are fully recycled and reused, and waste heat is efficiently utilized to reduce energy consumption. No independent hazardous waste disposal unit is required. The overall economic efficiency is better than the existing decentralized treatment process, and environmental protection and economic benefits are synergistically improved. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of a process for the co-processing and resource utilization of cyanide tailings roasting, based on the present invention.

[0021] The present invention will now be described in further detail with reference to the accompanying drawings. Detailed Implementation

[0022] As attached Figure 1 As shown, the cyanide tailings roasting and co-processing resource utilization technology includes cyanide tailings pretreatment and roasting, flue gas cascade utilization, sodium sulfite preparation, roasting slag fine grinding and secondary cyanide leaching, secondary cyanide tailings SO2 decyanation treatment, decyanation tailings preparation of non-fired bricks, and closed-loop management of the entire process. Specifically, it includes the following process steps and conditions:

[0023] S1. Pretreatment and roasting of cyanide tailings: The cyanide tailings are dried sequentially to a moisture content of less than 8%, pre-screened to remove large impurities larger than 5cm, and then fed into a rotary kiln for roasting. The roasting conditions are controlled at 600~750℃, oxidizing atmosphere, roasting time of 1.5~3h, and material layer thickness of 5~10cm. During the roasting process, cyanide ions are pyrolyzed and destroyed, sulfur components are oxidized and release SO2 flue gas, and gold minerals in the roasting slag are dissociated and activated. The flue gas generated by roasting is sequentially treated by cyclone dust collector, bag filter dust collector, rapid cooling and washing, and demisting and arsenic and fluorine removal to remove dust, heavy metals, arsenic and fluorine and other impurities from the flue gas, resulting in purified SO2 flue gas. At the same time, a waste heat recovery device is installed to recover the high-temperature flue gas and the waste heat of the kiln. The generated steam is used for subsequent leaching insulation and sodium sulfite evaporation and crystallization processes.

[0024] S2. Cascaded diversion and utilization of flue gas: The SO2 flue gas purified in step S1 is intelligently diverted, with 50-80% of the flue gas sent to the sodium sulfite preparation system and the remaining flue gas sent to the cyanide tailings decyanation system. During the diversion process, the flue gas distribution ratio is dynamically adjusted according to the cyanide concentration and processing volume of the subsequent decyanation tailings to ensure that the amount of SO2 required for decyanation matches the amount of flue gas supplied.

[0025] S3. Sodium sulfite preparation: The SO2 flue gas diverted from step S2 to the sodium sulfite preparation system is fed into the absorption tower and contacted countercurrently with the soda ash or caustic soda absorbent. The absorption pH is controlled at 6.5~7.5, the liquid-to-gas ratio at 8~12 L / m³, and the absorption temperature at 30~45℃. After absorption, the gas is purified by wet ion exchange resin to remove impurities such as calcium and magnesium, and then deeply decolorized by activated carbon. It is then sent to the evaporator crystallizer, where the residual heat recovered in step S1 is used to evaporate and crystallize at 60~80℃ to obtain sodium sulfite product and crystallization mother liquor. 60~80% of the crystallization mother liquor is returned to the absorption tower for recycling, and the remaining part is further evaporated to produce sodium sulfate, achieving zero discharge of waste liquid. A final-stage alkaline absorption tower is added to the tail gas of the absorption tower to capture trace amounts of SO2, and the absorbent is reused in the main absorption system.

[0026] S4. Fine grinding of roasted slag and secondary cyanide leaching: The roasted slag produced in step S1 is fed into a staged grinding and classification system that links a ball mill and a spiral classifier. It undergoes coarse grinding, classification, and fine grinding in sequence. The fineness of the slurry after fine grinding is controlled to be 85-95% of the particles being -200 mesh. The finely ground slurry is then fed into a cyanide leaching tank, where sodium cyanide, an alkali regulator, and a leaching aid are added. The concentration of sodium cyanide is controlled to be 0.05-0.12%, the pH of the slurry to be 10-11, the leaching time to be 24-48 hours, and the slurry concentration to be 40%-50%. Activated carbon is added during the leaching process for pre-adsorption to improve gold recovery efficiency. After leaching, gold in the leaching solution is recovered through a carbon adsorption process. The resulting secondary cyanide tailings slurry is then sent to a decyanation system for further processing.

[0027] S5. SO2 decyanation treatment of secondary cyanide tailings: The secondary cyanide tailings slurry generated in step S4 is sent to the decyanation reaction tank, and the SO2 flue gas diverted in step 2 is introduced. The SO2-air oxidation process is used for decyanation. After decyanation, the slurry is sent to a thickener and a filter press for dewatering. The moisture content of the filter cake is controlled to be 15-25%. The decyanation tailings are returned to the cyanide leaching process.

[0028] S6. Preparation of non-fired bricks from decyanated tailings: The tailings after decyanation in step S5 are used as the main raw material, combined with coarse aggregate, fly ash and slag, and the particle size distribution is optimized. The content of decyanated tailings is 60-80%. Cement binder and heavy metal passivating agent are added, and after being mixed evenly, they are sent to a high-pressure molding machine for molding. The molding pressure is 15-25 MPa. The molded brick blanks are sent to a steam curing chamber and cured at 80-100℃ for 8-12 hours to obtain the finished non-fired bricks.

[0029] S7. Closed-loop management of the entire process: The dust collected by the bag filter in step S1 is returned to the rotary kiln roasting system to recover valuable metals. The tailings of the decyanation in step S5, the condensate from the salt production in step S3, and the flue gas scrubbing water in step S1 are all recycled and reused to achieve zero wastewater discharge.

[0030] The process of the present invention can be further described as follows:

[0031] In step S1, the rapid cooling wash uses an alkaline washing solution, and the washing pH is controlled at 9-11 to improve the removal effect of arsenic, fluorine and heavy metals.

[0032] In step S4, the alkali regulator is either lime or sodium hydroxide, the leaching aid is a compound system of sodium lignosulfonate and calcium chloride with a compound ratio of 3:1 and an addition amount of 0.02% to 0.05% of the slurry mass, and the activated carbon is 2-3 mm coconut shell activated carbon with an iodine value ≥1000 mg / g and an addition amount of 15-35 g / L slurry.

[0033] In step S5, the decyanation process controls the reaction pH to be 8-10, the reaction temperature to be 10-50℃, the reaction time to be 1-2h, and the air aeration rate to be 0.5-1.0m³ / (m³·h).

[0034] In step S6, the coarse aggregate has a particle size of 5-10 mm and a dosage of 5-10%, the fly ash dosage is 5-8%, the slag dosage is 5-7%, the cementitious material is P·O42.5 ordinary Portland cement with a dosage of 5-10%, the heavy metal passivating agent is phosphate or sulfide stabilizer with an addition amount of 0.3%-0.8% of the cyanide tailings mass, and the steam curing adopts a segmented curing mode: first preheating at 60℃ for 2 hours, and then heating to 80-100℃ for 6-10 hours to avoid brick cracking and improve the brick strength to MU15 grade or above.

[0035] Example 1

[0036] Cyanide tailings with a cyanide concentration of 80 mg / kg and a gold content of 1.5 g / t were selected. The specific treatment steps and parameters are as follows: Tailings pretreatment and roasting: The cyanide tailings were dried to a moisture content of 7% and pre-screened to remove large impurities larger than 5 cm; they were then fed into a rotary kiln for roasting, with the temperature controlled at 700℃ and an oxidizing atmosphere for 2 hours, and the material layer thickness at 8 cm; the roasting flue gas was sequentially treated by cyclone dust collector, bag filter dust collector, alkaline rapid cooling washing (pH=10), and demisting and arsenic and fluorine removal to obtain purified flue gas with an SO2 concentration of 9%; the waste heat recovery unit generates 0.35 MPa steam for subsequent leaching insulation and evaporation crystallization; the flue gas is then used in a cascaded diversion process. Based on an estimated cyanide concentration of 50 mg / kg in the secondary cyanide tailings, 65% of the purified SO2 flue gas is sent to the sodium sulfite preparation system, and 35% is sent to the secondary cyanide tailings decyanation system, dynamically matching the SO2 removal requirements: Sodium sulfite preparation: Caustic soda absorbent is introduced into the absorption tower and contacted countercurrently with the SO2 flue gas, controlling pH=7.0, liquid-to-gas ratio=10L / m³, and absorption temperature=38℃; the absorbent is purified by ion exchange resin to remove calcium and magnesium impurities and deeply decolorized by activated carbon, then sent to an evaporator crystallizer, where waste heat steam is used for evaporation and crystallization at 70℃ to obtain the finished sodium sulfite; 70% of the crystallization mother liquor is returned to the absorption tower for recycling, and 30% is... Further evaporation is used to produce sodium sulfate; the tail gas is treated by the final alkaline absorption tower, and the SO2 emission concentration is <35mg / m³; fine grinding and secondary cyanide leaching of roasted slag: the roasted slag is ground and classified by a ball mill and a spiral classifier, and the fineness of the slurry after fine grinding is controlled to be 90% of -200 mesh; the slurry is sent to the cyanide leaching tank, 0.08% sodium cyanide is added, the pH of the slurry is adjusted to 10.5 with sodium hydroxide, a compound leaching aid (sodium lignosulfonate: calcium chloride = 3:1, added at 0.035% of the slurry mass) is added, and 2~3mm coconut shell activated carbon (iodine value 1050mg / g, added at 25g / L slurry) is added; the slurry concentration is controlled at 45% and the leaching time is 40h, and the activated carbon pre-adsorbs gold during the leaching process; after leaching, the gold is adsorbed by carbon. Gold is recovered from the process. The cyanide concentration in the secondary cyanide tailings slurry is 50 mg / kg, which is then sent to the decyanation system. SO2 decyanation treatment of the secondary cyanide tailings: The secondary cyanide tailings slurry is sent to the decyanation reaction tank, and diverted SO2 flue gas is introduced. SO2-air oxidation is used, controlling the reaction pH at 9.0, temperature at 35℃, air aeration rate at 0.8 m³ / (m³・h), and reaction time at 1.5 h. After the reaction, the slurry is concentrated by a thickener and dewatered by a filter press, controlling the filter cake moisture content at 18%. All decyanation tailings are returned to the cyanide leaching process for recycling. Preparation of non-fired bricks from decyanation tailings: Decyanation tailings are used as the main raw material (70% admixture), combined with coarse aggregate (5~10 mm, 8% admixture), fly ash (7%), slag (5%), P・O42.5 ordinary Portland cement (8%), and phosphate heavy metal passivator (0).(5% of the cyanide-removing tailings by weight), after being thoroughly mixed, is fed into a high-pressure molding machine and molded under 20 MPa pressure; the brick blanks are preheated at 60℃ for 2 hours, then steam-cured at 90℃ for 8 hours to obtain the finished non-fired bricks; the entire process is under closed-loop control: the flue gas collected by the bag filter is returned to the rotary kiln firing system to recover valuable metals and gold; the cyanide-removing tailings, salt-making condensate, and flue gas scrubbing water are all recycled and reused, achieving zero wastewater discharge.

[0037] Example 2

[0038] The specific treatment steps and parameters for cyanide tailings with a cyanide concentration of 60 mg / kg and a gold content of 1.2 g / t are as follows:

[0039] Cyanide tailings pretreatment and roasting: The cyanide tailings are dried to a moisture content of 6% and pre-screened to remove large impurities larger than 5cm; they are then fed into a rotary kiln for roasting at a controlled temperature of 650℃ in an oxidizing atmosphere for 2.5 hours, with a material layer thickness of 7cm; the roasting flue gas undergoes multi-stage purification to obtain purified flue gas with an SO2 concentration of 8%, and a waste heat recovery unit generates 0.3MPa. Steam: Cascaded utilization of flue gas: Based on the estimated cyanide concentration of 38 mg / kg in the secondary cyanidation tailings, 70% of the purified SO2 flue gas is sent to the sodium sulfite preparation system, and 30% to the decyanation system. Sodium sulfite preparation: Caustic soda absorbent is introduced into the absorption tower, controlling pH=7.3, liquid-to-gas ratio=10.5 L / m³, and absorption temperature=40℃. After refining and decolorization, the absorbent is evaporated and crystallized at 75℃ using residual heat to produce sodium sulfite. 65% of the crystallization mother liquor is refluxed, and 35% is used to produce sodium sulfate. The SO2 emission concentration in the tail gas is <32 mg / m³. Fine grinding of roasted slag and secondary cyanidation leaching: Roasted slag is ground to -200 mesh (92% content). 0.09% sodium cyanide is added to the cyanidation leaching tank, the pH is adjusted to 10.8, a compound leaching aid of 0.04% is added, and coconut shell activated carbon is added at 28 g / L of slurry. The slurry concentration was controlled at 46%, the leaching time at 42h, and gold was recovered by carbon adsorption. The cyanide concentration of the secondary cyanide tailings slurry was 38mg / kg. The secondary cyanide tailings underwent SO2 decyanation treatment. The decyanation reaction was controlled at pH=8.8, temperature at 38℃, air aeration rate at 0.85m³ / (m³・h), and reaction time at 1.2h. The filter cake after slurry dewatering had a moisture content of 19%. The decyanation tailings were returned to the cyanide leaching process. The decyanation tailings were used to prepare non-fired bricks. The decyanation tailings were mixed with 72% coarse aggregate, 9% fly ash, 6% slag, 5.5% P・O42.5 cement, and 0.5% phosphate passivating agent. The bricks were formed under high pressure at 21MPa. The brick blanks were preheated at 60℃ for 2h and then steam-cured at 92℃ for 8.5h to obtain the finished non-fired bricks. The process was closed-loop controlled: the flue gas was returned to the kiln for firing, and the wastewater from the entire process was recycled and reused, with no external discharge.

[0040] Example 3

[0041] The specific treatment steps and parameters for cyanide tailings with a cyanide concentration of 95 mg / kg and a gold content of 1.8 g / t are as follows:

[0042] Tailings pretreatment and roasting: Dry to 8% moisture content, pre-screen to remove impurities, then feed into a rotary kiln for oxidative roasting at 750℃ for 1.5h, with a material layer thickness of 10cm; SO2 concentration after flue gas purification is 10%, and waste heat recovery produces 0.4MPa steam; cascade utilization: the estimated cyanide concentration in the secondary cyanidation tailings is 58mg / kg, 60% of the purified flue gas is sent to the sodium sulfite system, and 40% is sent to the decyanation system; sodium sulfite preparation: the caustic soda absorbent is controlled at pH=6.8, liquid-to-gas ratio=9L / m³, and absorption temperature= 35℃; 65℃ residual heat evaporation crystallization, 75% of mother liquor refluxed, 25% used to produce sodium sulfate; tail gas SO2 emission concentration <30mg / m³: slag fine grinding and secondary cyanide leaching: grinding to -200 mesh (88%), cyanide leaching with 0.10% sodium cyanide added, pH adjusted to 10.2, compound leaching aid added at 0.03%, coconut shell activated carbon added at 30g / L slurry; slurry concentration 48%, leaching time 45h, carbon Adsorption and recovery of gold: SO2 decyanation treatment of cyanide tailings: The decyanation reaction is controlled at pH=9.2, temperature 30℃, air aeration rate of 0.7m³ / (m³・h), and reaction time of 2h; the filter cake after slurry dewatering has a moisture content of 20%, and the tailings are recycled and leached: Tailings preparation of non-fired bricks: 68% of the decyanated tailings are added, along with 7% coarse aggregate, 8% fly ash, 6% slag, 9% P・O42.5 cement, and 0.6% sulfide passivating agent, and high-pressure molding at 22MPa; after preheating at 60℃ for 2h, the bricks are cured at 95℃ for 9h to obtain the finished non-fired bricks: Closed-loop management of the process: dust recirculation and zero wastewater discharge, realizing full-process circulation.

[0043] Comparative Example 1

[0044] The process of cascade diversion and utilization of flue gas was eliminated, and all 100% purified SO2 flue gas was sent to the sodium sulfite preparation system. The secondary cyanide tailings decyanation adopted the traditional sodium hypochlorite oxidation method. The remaining process steps and parameters were completely consistent with those in Example 1.

[0045] Comparative Example 2

[0046] The secondary cyanidation gold leaching process of roasted slag was eliminated. After grinding, the roasted slag was directly sent to the SO2 decyanation system. After decyanation, it was directly used to make non-fired bricks. The remaining process steps and parameters were completely consistent with those in Example 1.

[0047] Comparative Example 3

[0048] When preparing non-fired bricks from cyanide-removed tailings, no heavy metal passivating agent was added and the content of cyanide-removed tailings was increased to 85%, the molding pressure was reduced to 10 MPa, and the remaining process steps and parameters were completely consistent with those in Example 1.

[0049] Comparative Example 4

[0050] The roasting process uses a neutral atmosphere and a roasting temperature of 550℃ (lower than the core range of this invention). The remaining process steps and parameters are completely consistent with those in Example 1.

[0051] Test results

[0052] The processing effects, resource recovery efficiency, product performance, and operating costs of the above embodiments and comparative examples were statistically analyzed, and the results are shown in the table below:

[0053] Table 1. Comparison of Experimental Results for Each Column

[0054] Group Gold recovery rate (%) Cyanide concentration in tailings after cyanide removal (mg / kg) <![CDATA[SO2 resource utilization rate (%)]]> Strength grade of unfired bricks Cyanide / heavy metal leaching of non-fired bricks Comprehensive cost of reagents (RMB / ton of tailings) Example 1 87.1 ＜0.5 100 MU18 All are below national standards 38.5 Example 2 85.8 ＜0.5 100 MU19 All are below national standards 37.2 Example 3 88.5 ＜0.5 100 MU17 All are below national standards 40.1 Comparative Example 1 87 ＜0.5 65 MU18 All are below national standards 59.8 Comparative Example 2 0 ＜0.5 100 MU16 All are below national standards 32.3 Comparative Example 3 87.2 ＜0.5 100 MU10 Excessive heavy metal leaching 35.6 Comparative Example 4 62.3 45.2 78 MU15 Excessive cyanide leaching 42.7

[0055] As shown in the summary table, the results of Examples 1-3 of this invention verify the stability of the process: After treatment with this process, the gold recovery rate of cyanide tailings with different cyanide concentrations and gold contents is ≥85.8%, the cyanide concentration of the tailings after decyanation is <0.5mg / kg, SO2 is 100% utilized, the strength of the produced non-fired bricks is ≥MU17 and the leaching of cyanide and heavy metals meets the standards, and the comprehensive cost of the reagents is controlled within 40.1 yuan / ton of tailings, which reflects the process's impact resistance and synergistic resource utilization advantages.

[0056] Comparative Example 1 highlights the economic advantages of cascaded flue gas diversion: While traditional sodium hypochlorite decyanation can achieve cyanide removal to meet standards, it requires additional oxidant, increasing reagent costs by 55.3% compared to Example 1. Furthermore, only 65% ​​of the SO2 flue gas is utilized, with the remaining flue gas being directly discharged, resulting in resource waste and environmental pressure. This verifies the necessity of cascaded flue gas diversion. Comparative Example 2 demonstrates the core value of secondary cyanide leaching: After eliminating the secondary cyanide leaching process, the dissociated and activated gold resources in the roasting slag are not recovered, resulting in a gold recovery rate of 0%. Although the processing cost is slightly reduced, the secondary recovery benefits of gold resources are lost, significantly decreasing resource utilization efficiency. Comparative Example 3 illustrates the importance of passivating agents and process parameters: The absence of heavy metal passivating agents, excessive tailings addition, and insufficient molding pressure resulted in a non-fired brick strength of only MU10 (below the standard for building bricks), and excessive heavy metal leaching. This prevents the harmless disposal of solid waste, achieving only a form of resource utilization without meeting environmental requirements. Comparative Example 4 verifies the rationality of the roasting process parameters: Neutral low-temperature roasting cannot fully pyrolyze and destroy cyanide ions, and the gold mineral dissociation and activation are insufficient, resulting in a gold recovery rate of 62.3%. After decyanation, the cyanide concentration in the tailings is still 45.2 mg / kg. After brick making, cyanide leaching exceeds the standard, and SO2 release is insufficient, with a resource utilization rate of only 78%. This proves that the 600~750℃ oxidative roasting parameters of this invention are the key to achieving cyanide removal and gold dissociation.

[0057] In summary, this invention achieves the harmless treatment and full resource synergistic utilization of cyanide tailings through a closed-loop process design of "roasting-gold extraction-denitrification-resource utilization". It solves the problems of disconnection between various links in traditional processes, low resource utilization efficiency and high environmental risks. The process parameters are synergistically matched, and the industrial application prospects are significant.

[0058] As described above, the present invention can be well implemented. The above embodiments are only the best implementations of the present invention, but the implementation of the present invention is not limited to the above embodiments. Other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention should be considered equivalent substitutions and are all included within the protection scope of the present invention.

Claims

1. A process for the co-processing and resource utilization of cyanide tailings roasting, characterized in that... It includes cyanide tailings pretreatment and roasting, flue gas cascade utilization, sodium sulfite preparation, roasting slag fine grinding and secondary cyanide leaching, secondary cyanide tailings SO2 decyanation treatment, decyanation tailings preparation of non-fired bricks, and closed-loop management of the entire process. Specifically, it includes the following process steps and conditions: S1. Pretreatment and roasting of cyanide tailings: The cyanide tailings are dried sequentially to a moisture content of less than 8%, pre-screened to remove large impurities larger than 5cm, and then fed into a rotary kiln for roasting. The roasting conditions are controlled at 600~750℃, oxidizing atmosphere, roasting time of 1.5~3h, and material layer thickness of 5~10cm. During the roasting process, cyanide ions are pyrolyzed and destroyed, sulfur components are oxidized and release SO2 flue gas, and gold minerals in the roasting slag are dissociated and activated. The flue gas generated by roasting is sequentially treated by cyclone dust collector, bag filter dust collector, rapid cooling and washing, and demisting and arsenic and fluorine removal to remove dust, heavy metals, arsenic and fluorine and other impurities from the flue gas, resulting in purified SO2 flue gas. At the same time, a waste heat recovery device is installed to recover the high-temperature flue gas and the waste heat of the kiln. The generated steam is used for subsequent leaching insulation and sodium sulfite evaporation and crystallization processes. S2. Cascaded diversion and utilization of flue gas: The SO2 flue gas purified in step S1 is intelligently diverted, with 50-80% of the flue gas sent to the sodium sulfite preparation system and the remaining flue gas sent to the cyanide tailings decyanation system. During the diversion process, the flue gas distribution ratio is dynamically adjusted according to the cyanide concentration and processing volume of the subsequent decyanation tailings to ensure that the amount of SO2 required for decyanation matches the amount of flue gas supplied. S3. Sodium sulfite preparation: The SO2 flue gas diverted from step S2 to the sodium sulfite preparation system is fed into the absorption tower and contacted countercurrently with the soda ash or caustic soda absorbent. The absorption pH is controlled at 6.5~7.5, the liquid-to-gas ratio at 8~12 L / m³, and the absorption temperature at 30~45℃. After absorption, the gas is purified by wet ion exchange resin to remove impurities such as calcium and magnesium, and then deeply decolorized by activated carbon. It is then sent to the evaporator crystallizer, where the residual heat recovered in step S1 is used to evaporate and crystallize at 60~80℃ to obtain sodium sulfite product and crystallization mother liquor. 60~80% of the crystallization mother liquor is returned to the absorption tower for recycling, and the remaining part is further evaporated to produce sodium sulfate, achieving zero discharge of waste liquid. A final-stage alkaline absorption tower is added to the tail gas of the absorption tower to capture trace amounts of SO2, and the absorbent is reused in the main absorption system. S4. Fine grinding of roasted slag and secondary cyanide leaching: The roasted slag produced in step S1 is fed into a staged grinding and classification system that links a ball mill and a spiral classifier. It undergoes coarse grinding, classification, and fine grinding in sequence. The fineness of the slurry after fine grinding is controlled to be 85-95% of the particles being -200 mesh. The finely ground slurry is then fed into a cyanide leaching tank, where sodium cyanide, an alkali regulator, and a leaching aid are added. The concentration of sodium cyanide is controlled to be 0.05-0.12%, the pH of the slurry to be 10-11, the leaching time to be 24-48 hours, and the slurry concentration to be 40%-50%. Activated carbon is added during the leaching process for pre-adsorption to improve gold recovery efficiency. After leaching, gold in the leaching solution is recovered through a carbon adsorption process. The resulting secondary cyanide tailings slurry is then sent to a decyanation system for further processing. S5. SO2 decyanation treatment of secondary cyanide tailings: The secondary cyanide tailings slurry generated in step S4 is sent to the decyanation reaction tank, and the SO2 flue gas diverted in step 2 is introduced. The SO2-air oxidation process is used for decyanation. After decyanation, the slurry is sent to a thickener and a filter press for dewatering. The moisture content of the filter cake is controlled to be 15-25%. The decyanation tailings are returned to the cyanide leaching process. S6. Preparation of non-fired bricks from decyanated tailings: The tailings after decyanation in step S5 are used as the main raw material, combined with coarse aggregate, fly ash and slag, and the particle size distribution is optimized. The content of decyanated tailings is 60-80%. Cement binder and heavy metal passivating agent are added, and after being mixed evenly, they are sent to a high-pressure molding machine for molding. The molding pressure is 15-25 MPa. The molded brick blanks are sent to a steam curing chamber and cured at 80-100℃ for 8-12 hours to obtain the finished non-fired bricks. S7. Closed-loop management of the entire process: The dust collected by the bag filter in step S1 is returned to the rotary kiln roasting system to recover valuable metals. The tailings of the decyanation in step S5, the condensate from the salt production in step S3, and the flue gas scrubbing water in step S1 are all recycled and reused to achieve zero wastewater discharge.

2. The process according to claim 1, characterized in that: In step S1, the rapid cooling wash uses an alkaline washing solution, and the washing pH is controlled at 9-11 to improve the removal effect of arsenic, fluorine and heavy metals.

3. The process according to claim 1, characterized in that: In step S4, the alkali regulator is either lime or sodium hydroxide, the leaching aid is a compound system of sodium lignosulfonate and calcium chloride with a compound ratio of 3:1 and an addition amount of 0.02% to 0.05% of the slurry mass, and the activated carbon is 2-3 mm coconut shell activated carbon with an iodine value ≥1000 mg / g and an addition amount of 15-35 g / L slurry.

4. The process according to claim 1, characterized in that: In step S5, the decyanation process controls the reaction pH to be 8-10, the reaction temperature to be 10-50℃, the reaction time to be 1-2h, and the air aeration rate to be 0.5-1.0m³ / (m³·h).

5. The process according to claim 1, characterized in that: In step S6, the coarse aggregate has a particle size of 5-10 mm and a dosage of 5-10%, the fly ash dosage is 5-8%, the slag dosage is 5-7%, the cementitious material is P·O42.5 ordinary Portland cement with a dosage of 5-10%, the heavy metal passivating agent is phosphate or sulfide stabilizer with an addition amount of 0.3%-0.8% of the cyanide tailings mass, and the steam curing adopts a segmented curing mode: first preheating at 60℃ for 2 hours, and then heating to 80-100℃ for 6-10 hours to avoid brick cracking and improve the brick strength to MU15 grade or above.

Images