Pretreatment method for ore containing sulfur and arsenic

Abstract

The invention discloses a pretreatment method and system for sulfur-containing and arsenic-containing ore. The method comprises the steps of crushing, alkaline wet ore grinding, strong alkaline pre-oxidation, cyanidation leaching, cyanogen removal treatment and high alkaline flotation. In the pretreatment process, liquid caustic soda is added into an ore grinding system, and oxygen is introduced into a cyanidation serial stirring tank for pre-oxidation treatment, so that the oxidation activation effect of the arsenic-sulfur minerals is remarkably enhanced, and the gold release efficiency and the cyanidation leaching rate are improved. The same group of serially connected stirring tanks is adopted for pre-oxidation and cyanidation leaching, and the first three stirring tanks are used for pre-oxidation and subsequently communicated with the stirring tanks for cyanidation reaction, so that process integration and equipment reuse are realized. Experimental results show that the comprehensive recovery rate of gold can be remarkably increased, the agent consumption can be reduced, and the method has good industrial application value.

Description

Technical Field

[0001] The present invention relates to the technical field of mineral processing and metallurgy, and in particular to a pretreatment method for sulfur - containing and arsenic - containing ores. Background Art

[0002] The recovery rates of sulfur - containing and arsenic - containing ores are relatively low. Especially in cyanidation and flotation processes, when arsenopyrite (arsenical pyrite) is the main arsenic mineral, its floatability is poor and the flotation effect is not good. Arsenic minerals undergo chemical reactions during cyanidation, affecting the cyanidation leaching efficiency. Due to the mineral complexity and reaction characteristics of arsenic - containing and sulfur - containing ores, the difficulty of gold extraction is increased. Optimization in flotation and cyanidation processes is required to improve the gold recovery rate. Conventional flotation or cyanidation processes fail to effectively treat arsenopyrite and cannot significantly improve the recovery rate, affecting the overall economic benefits. Summary of the Invention

[0003] In order to solve the above - mentioned technical problems, the present invention provides a pretreatment method for sulfur - containing and arsenic - containing ores, aiming to improve the gold recovery rate, effectively reduce the contents of arsenic and sulfur at the same time, and reduce the consumption of cyanide. The following technical solutions are adopted:

[0004] A pretreatment method for arsenic - containing and sulfur - containing ores includes the following steps:

[0005] (1) Crush the arsenic - containing and sulfur - containing ores, send the crushed ores into a ball mill, and at the same time add liquid caustic soda. Perform wet grinding in an alkaline environment with a pH value of 12 - 12.5 to obtain pulp.

[0006] (2) Perform strong - base pre - oxidation on the pulp.

[0007] (3) Perform cyanidation leaching on the pulp pre - oxidized in step (2) to obtain cyanidation tailings.

[0008] (4) Perform de - cyanidation treatment on the cyanidation tailings.

[0009] (5) Float the pulp after de - cyanidation treatment in step (4) to obtain gold concentrate.

[0010] Further, in step (1), the crushing particle size of the arsenic - containing and sulfur - containing ores is ≤120 mm.

[0011] Further, in step (1), the fineness of the grinding product is such that - 0.074 mm accounts for more than 80% - 85%, and the pulp concentration is controlled at 38% - 40%.

[0012] Further, the strong - base pre - oxidation in step (2) includes feeding the pulp obtained in step (1) into a pre - oxidation stirring tank, adding liquid caustic soda to maintain the pH value in the tank at 12 - 12.5, introducing oxygen or high - pressure air so that the dissolved oxygen in the pulp ≥10 ppm, and stirring for 9 hours.

[0013] Further, the cyanidation in step (3) includes feeding the pre-oxidized pulp into a cyanidation stirring tank, adding sodium cyanide, and filling with oxygen-enriched high-pressure air. The cyanidation time is 21 hours, and the pH value in the cyanidation stirring tank in this step ranges from 11.5 to 12.

[0014] Further, the de-cyanidation treatment in step (4) includes adding sodium metabisulfite and copper sulfate to the cyanidation tailings, and simultaneously introducing oxygen or compressed air to react for 2 hours to reduce the total cyanide content to below 5 ppm.

[0015] Further, the concentration of the pulp after de-cyanidation treatment in step (5) ranges from 25% to 33%, and the pH value ranges from 10.5 to 11. Flotation reagents (including copper sulfate, xanthate, and foaming agent) are added in sequence, and flotation is carried out for 30 minutes to obtain gold concentrate.

[0016] To implement the above method, the present invention provides a system for the pretreatment of arsenic- and sulfur-containing ores, including:

[0017] A crushing device for crushing arsenic- and sulfur-containing ores;

[0018] A grinding device including a mill and a hydrocyclone, and an automatic liquid caustic adding device for the mill;

[0019] A pre-oxidation unit including a pre-oxidation stirring tank for strong alkali pre-oxidation;

[0020] A cyanidation unit including a cyanidation stirring tank for cyanidation leaching reaction;

[0021] A de-cyanidation tank for de-cyanidation;

[0022] A flotation machine for flotation of the pulp after de-cyanidation treatment.

[0023] Further, the pre-oxidation unit and the cyanidation unit share a stirring device composed of N series-connected stirring tanks, where N is greater than 3. The first 3 stirring tanks are connected in series and used as pre-oxidation stirring tanks. After the pulp is pre-oxidized, the first 3 stirring tanks are connected to all the subsequent stirring tanks and used as cyanidation stirring tanks to jointly complete the cyanidation leaching step.

[0024] Further, in the stirring device composed of the above N series-connected stirring tanks, N = 10.

[0025] Through the above technical solutions, the beneficial effects of the present invention are as follows:

[0026] (a) Optimize the reagent addition process: Liquid sodium hydroxide is added at the grinding stage to achieve the synergistic effect of pulp temperature rise and dissociation of mineral particles, significantly enhancing the oxidation and activation effect of arsenic and sulfur minerals;

[0027] (b) Adopt a strong base flotation environment: Break through the limitation of the relatively low alkalinity of the traditional flotation environment, conduct flotation in a high-alkaline environment, and significantly improve the recovery effect of refractory minerals.

[0028] (c) Innovative technological process sequence: Propose a new process sequence of "strong base pre-oxidation → cyanidation leaching → de-cyanidation treatment → high-alkaline flotation", effectively improving the comprehensive recovery efficiency of gold in the ore.

[0029] After implementing this technical solution, the cyanidation leaching rate of gold increases by more than 8%, the recovery rate of the flotation operation increases by more than 30%, and the overall comprehensive recovery rate increases by more than 9%; the removal rates of arsenic and sulfur in the ore reach more than 23% and more than 20% respectively, showing good comprehensive economic and environmental benefits. Specific implementation method

[0030] As a typical refractory gold ore resource, the development and utilization of arsenic-bearing sulfur gold ore has long been restricted by problems such as the formation of passivation films on the surface of sulfide minerals, slow interfacial reaction kinetics, and insufficient adaptability of traditional cyanidation-flotation processes. For this type of ore, the present invention proposes a "strong base oxidation pretreatment - cyanidation first and then flotation" collaborative process path. By introducing liquid NaOH at the grinding stage to establish a super-strong alkaline environment with pH≥12 and combining an oxygen charging system for high-pressure enhanced oxidation, effectively dissolve and remove the passivation films of low-valent sulfates, arsenites, and polysulfides formed on the surfaces of arsenopyrite and pyrite, thereby exposing the surface of gold particles and increasing the kinetic rate of gold cyanidation leaching; at the same time, the surface activity of minerals is enhanced, which helps to improve the flotation recovery rate. The technical solution of the present invention is further illustrated by the following examples:

[0031] Example 1:

[0032] The raw material is arsenic-bearing sulfur ore containing 4.8 g / t of gold, 0.8% of sulfur, and 0.13% of arsenic. The specific technological process is as follows:

[0033] (1) Crushing: The raw ore is fed into a C100 jaw crusher through a 1500×7000 heavy-duty plate feeder. The particle size of the crushed product is -120 mm, and the crushing capacity is 200 t / h.

[0034] (2) Grinding: The crushed product is fed into a Φ4700×10200 semi-autogenous mill through a belt conveyor, and 50% NaOH solution is added to the grinding system. The grinding pulp concentration is 80%-82%, and the pulp pH reaches 12-12.5. The above grinding products are screened by a vibrating screen, and the oversize stones are recycled and crushed and returned to the mill. The undersize materials enter a hydrocyclone group for classification. The cyclone underflow returns to the mill for re-grinding, and the overflow pulp (concentration 38%-40%, fineness -200 mesh 80%-85%) enters the cyanidation system.

[0035] (3) Strong alkali pre-oxidation: Before the mill overflow pulp enters the cyanidation system, it first enters the pre-oxidation unit. Liquid alkali is added to the pre-oxidation agitation tank to keep the pulp pH value at 12 - 12.5. Oxygen is introduced with an oxygen flow rate of 80 m 3 / h, oxygen purity of 85%, agitation residence time of 9 hours, and the dissolved oxygen in the pulp ≥ 10 ppm to achieve the oxidative cracking of arsenopyrite and pyrite and improve the subsequent leachability of gold.

[0036] (4) Cyanidation leaching: The cyclone overflow pulp concentration is 38% - 40%, and the fineness is -200 mesh 80% - 85%. The pulp sequentially enters 7 leaching tanks with a diameter of Φ9000×9500. Sodium cyanide is added (200 - 220 ppm in the first tank and 100 - 120 ppm in the last tank), the pulp pH value is maintained at 11.5 - 12, and oxygen is introduced to make the dissolved oxygen reach 5 - 10 ppm. The cyanidation cycle is 21 hours.

[0037] (5) Cyanide removal: The cyanidation tailings flow by gravity into 4 agitation tanks with a diameter of Φ5000×6500. Sodium metabisulfite 1.2 kg / t and copper sulfate 0.22 kg / t are added. At the same time, oxygen or compressed air is introduced, and the reaction lasts for 2 hours to ensure that the total cyanide content in the tailings pulp is reduced to less than 5 ppm.

[0038] (6) Flotation: The cyanide removal tailings pulp concentration is 38% - 40%. After adding water to dilute the pulp concentration to 25% - 33%, it sequentially passes through a two-rougher, one-scavenger, and one-cleaner flotation system. Copper sulfate 150 g / t, xanthate 150 g / t, and foaming agent 20 g / t are added. The flotation time is 30 minutes to obtain gold concentrate with a grade of 12 - 15 g / t.

[0039] (7) Desorption and electrolysis: The gold-loaded carbon obtained by flotation enters a desorption column with a diameter of Φ1300×8700 after pickling. Each time, 5.5 t of carbon is loaded, and the desorption temperature is 140 °C. The desorbed solution is electrolytically deposited to obtain gold mud, and the electrolytic cell voltage is 2 - 3 V.

[0040] (8) Calcination and smelting: The gold mud is loaded into a stainless steel tray, calcined at 700 °C, and then flux is added. It is melted and ingoted in an intermediate frequency furnace at 1200 °C to obtain crude gold with an alloy content of Au + Ag > 95%.

[0041] (9) Activated carbon regeneration: The gold-depleted carbon after desorption is regenerated in a regeneration kiln to restore the carbon activity, 750 °C (zone I) and 650 °C (zone II), and is recycled.

[0042] Compared with the conventional process, the cyanidation leaching recovery rate in this example has increased by more than 8%, the flotation recovery rate has increased by more than 30%, the comprehensive recovery rate exceeds 96%, and the consumption of cyanide and flotation reagents has been effectively reduced, achieving good economic and environmental benefits and having obvious industrial application advantages.

[0043] Comparative example 1:

[0044] The raw materials are arsenic- and sulfur-bearing ores with the same properties as those in the above embodiment, containing 4.8 g / t of gold, 0.8% of sulfur, and 0.13% of arsenic. Except for the pre-oxidation step, the other steps of the process flow are exactly the same as those in the embodiment. Specifically, they are: crushing, grinding, cyanidation leaching, de-cyanidation, flotation, desorption electrolysis, calcination and smelting, and activated carbon regeneration. The pulp without the pre-oxidation step directly enters the cyanidation leaching step. The single consumption of sodium cyanide is slightly higher, about 0.45 kg / t of ore. The cyanidation recovery rate is 74.8%, the recovery rate of the flotation operation is 51.3%, and the comprehensive recovery rate is 87.6%. The consumption of cyanidation agents increases significantly, and the environmental load increases.

[0045] Thus, it can be seen that the process proposed by the present invention effectively improves the recovery rate of gold, significantly reduces the consumption of agents and the environmental load, and enhances the overall efficiency of the process by adding a pre-oxidation step.

[0046] Example 2:

[0047] Taking a sulfur- and arsenic-bearing ore in a certain mine pit as an example, the gold grade of the ore is 4.8 g / t, the sulfur content is 0.8%, and the arsenic content is 0.13%. After the ore is initially crushed by a jaw crusher, the particle size is controlled to be ≤120 mm and fed into a Φ4700×10200 mm semi-autogenous mill. The grinding medium is steel balls, the rotation speed is 16 r / min, and the ball loading is 16%-20% of the mill volume. During the grinding process, the pulp concentration is controlled at 80%, the dosage of 50% NaOH solution is 0.8% of the ore mass, the pulp pH reaches 12-12.5, and the grinding fineness of -0.074 mm accounts for 85%.

[0048] The ground pulp is first fed into 3 modified pre-oxidation agitation tanks connected in series (the first three tanks of the original cyanidation agitation tanks are used in this embodiment), and the volume of each tank is 540 m 3 , the agitation rotation speed is 50 rpm. By adding 50% NaOH solution into the first tank, the pulp pH value is controlled at 12-12.5. Through the oxygen pipeline at the bottom of the tank body, oxygen with a purity of 85% is introduced at a flow rate of 80 m 3 / h to maintain the dissolved oxygen concentration in the pulp at about 10 ppm. The total residence time is 6 hours to complete the pre-oxidation step.

[0049] After the pre-oxidation is completed, all 3 pre-oxidation agitation tanks are connected to the subsequent 7 cyanidation agitation tanks to form a cyanidation leaching unit with a total of 10 tanks connected in series. 0.31 kg / t of ore of sodium cyanide is added to the cyanidation leaching unit. At this time, the pulp pH value is between 11.5-12, and cyanidation leaching is carried out. The total residence time is 21 hours. During the cyanidation process, the oxygen flow rate is 140 m 3 / h, and the oxygen purity is 80%.

[0050] The pulp after grinding first enters the first three of the existing 10 series-connected stirring tanks for strong alkaline pre-oxidation. These three tanks are connected in series with each other, and the total residence time is about 9 hours. During this period, the pH value of the pulp is maintained at 12 - 12.5, and oxygen or high-pressure air is introduced to make the dissolved oxygen ≥ 10 ppm, thereby significantly oxidizing arsenopyrite and pyrite, removing part of sulfur and arsenic and fully exposing gold particles. After that, the pulp after pre-oxidation does not need to be switched to other pipelines, but continues to flow through the subsequent 7 cyanidation stirring tanks in sequence along the series-connected path, together with the first three tanks in the front section, to form 10 series-connected tanks to complete cyanidation leaching. At this time, sodium cyanide is added to the fourth tank, and in an environment with a pH value of 11.5 - 12, the total leaching time is 21 hours. Since the pulp has been treated with strong alkali oxidation in the first three tank stages, the consumption of cyanide is effectively reduced and the leaching rate of gold is increased when entering cyanidation. Finally, the pulp flows out from the 10th tank, completing the whole process operation of the integration of strong alkali pre-oxidation and cyanidation leaching.

[0051] The cyanided pulp is sent to the de-cyanidation tank. The volume of each tank of the de-cyanidation tank is 100m 3 (4 tanks), 1.20 kg / t of ore of sodium metabisulfite and 0.22 kg / t of ore of copper sulfate are added, and compressed air is introduced into the de-cyanidation tank through a Roots blower, with a flow rate of 2315m 3 / h, and the stirring reaction is carried out for 2 hours to ensure that the cyanide meets the discharge standards.

[0052] The de-cyanided pulp enters the roughing and scavenging flotation section. This section is equipped with 8 pneumatic mechanical agitation flotation machines with a single machine volume of 20m 3 for subsequent flotation operations. The pulp concentration is controlled at 25% - 33%. During flotation, 0.23 kg / t of ore of xanthate and 0.23 kg / t of ore of copper sulfate are added, and the flotation time is 30 minutes, obtaining a concentrate grade of 12 - 15 g / t.

[0053] Comparative Example 2:

[0054] Using sulfur-containing and arsenic-containing ores with the same properties as those in the above embodiment as raw materials, a conventional process with the same other process steps except the pre-oxidation step is used for treatment. After the ore goes through the same crushing and grinding steps, the pulp concentration is also controlled at 38% - 40%, and the fineness of the grinding product -0.074mm accounts for 80% - 85%. The pulp after grinding directly enters the cyanidation leaching tank composed of 8 series-connected stirring tanks, without a pre-oxidation step. The addition amount of sodium cyanide is 0.45 kg / t of ore, the pH is controlled at 10.5, and the total residence time of cyanidation leaching is 24 hours, and the oxygen flow rate is 140m 3 / h. The cyanided pulp is then subjected to the same de-cyanidation treatment and flotation treatment.

[0055] Comparison data of Example 2:

[0056] Index Comparative Example 2 Example 2 Recovery rate of gold cyanidation 74.8％ 83.2％ Recovery rate of flotation operation 51.3％ 82.0％ Comprehensive recovery rate 87.6％ 96.7％ Sulfur content 0.79％ 0.62％ Arsenic content 0.13％ 0.10％

[0057] In summary, by introducing an alkaline pre-oxidation unit, the present invention significantly improves the release efficiency and recovery rate of gold, reduces the consumption of cyanide agents and flotation reagents, has strong process continuity, is suitable for industrial promotion, and has significant technical and economic advantages. The results of industrial verification show that compared with the traditional process without a pre-oxidation step, the process of the present invention can increase the comprehensive recovery rate of gold by about 9%. While ensuring the efficient recovery of gold, this co-treatment process effectively alleviates long-existing problems such as high consumption of cyanide agents and poor flotation adaptability, demonstrates strong resource adaptation ability and process stability, and has good prospects for popularization and application.

Claims

1. A pretreatment method for arsenic- and sulfur-containing ores, characterized in that, It includes the following steps: (1) Crush the arsenic and sulfur-containing ore, send the crushed ore into a ball mill, and add liquid caustic soda at the same time. Carry out wet grinding in an alkaline environment with a pH value of 12 - 12.5 to obtain pulp; (2) Carry out strong base pre-oxidation on the pulp; (3) Carry out cyanidation leaching on the pulp pre-oxidized in step (2) to obtain cyanidation tailings; (4) Carry out de-cyanidation treatment on the cyanidation tailings; (5) Float the pulp after de-cyanidation treatment in step (4) in an alkaline environment to obtain gold concentrate.

2. The pretreatment method for arsenic- and sulfur-containing ore according to claim 1, wherein In step (1), the crushing particle size of the arsenic and sulfur-containing ore is ≤ 120 mm.

3. The pretreatment method for arsenic and sulfur-containing ore according to claim 2, characterized in that, In step (1), the fineness of the grinding product is such that -0.074 mm accounts for 80% - 85%, and the pulp concentration is controlled at 38% - 40%.

4. The pretreatment method for arsenic- and sulfur-containing ore according to claim 1, wherein The strong base pre-oxidation in step (2) includes feeding the pulp obtained in step (1) into a pre-oxidation stirring tank, adding liquid caustic soda, maintaining the pH value of the pulp at 12 - 12.5, introducing oxygen or high-pressure air to make the dissolved oxygen in the pulp ≥ 10 ppm, and stirring for 9 hours.

5. A pretreatment method for arsenic- and sulfur-containing ore according to claim 1, characterized in that The cyanidation in step (3) includes feeding the pre-oxidized pulp into a cyanidation stirring tank, adding sodium cyanide, and filling with oxygen-enriched high-pressure air. The cyanidation time 21 is hours, and the pH value is controlled at 11.5 - 12.

6. A pretreatment method for arsenic- and sulfur-containing ore according to claim 1, characterized in that, The de-cyanidation treatment in step (4) includes adding sodium metabisulfite and copper sulfate to the cyanidation tailings, introducing oxygen or compressed air at the same time and reacting for 2 hours to reduce the total cyanide content to below 5 ppm.

7. A pretreatment method for arsenic- and sulfur-containing ore according to claim 1, characterized in that, The flotation in step (5) includes adding flotation reagents in sequence under the conditions of a pulp concentration of 25% - 33% and a pH value of 10.5 - 11. The flotation reagents include copper sulfate, xanthate, and foaming agent, and carry out flotation for 30 minutes to obtain gold concentrate.

8. An application system for the pretreatment method of arsenic- and sulfur-containing ore according to any one of claims 1 to 7, characterized in that, It includes the following units: Crushing equipment, used for crushing the arsenic and sulfur-containing ore; Grinding equipment, including a mill, a hydrocyclone, and an automatic liquid caustic soda dosing device for the mill; Pre-oxidation unit, including a pre-oxidation stirring tank, used for strong base pre-oxidation; Cyanidation unit, including a cyanidation stirring tank, used for cyanidation leaching reaction; De-cyanidation tank, used for de-cyanidation; Flotation machine, used for flotation of the pulp after de-cyanidation treatment.

9. The application system according to claim 8, wherein The pre-oxidation unit and the cyanidation unit share a set of stirring devices composed of N series-connected stirring tanks, where N is greater than 3; the first 3 stirring tanks in the stirring device are connected in series and used as pre-oxidation stirring tanks. After the pulp is pre-oxidized, the first 3 stirring tanks are connected to all the subsequent stirring tanks and used as cyanidation stirring tanks.

10. The application system according to claim 8, characterized in that, The number N of stirring tanks in the stirring device is 10.