Introduction of Rock Gold CIP Process Plant
The gold carbon in pulp (CIP) Processing refers to the process of grinding all the gold ore into a slurry (-200 mesh content accounts for more than 90-95%). Cyanide leaching was carried out first, then activated carbon was used to absorb the Gold loaded carbon from the pulp, purification and smelting of the gold-loaded Gold in the medium adsorption of dissolved Gold, and the carbon desorption of the electro-deposited gold mud.
Including raw material preparation, stirring and cyanidation leaching activated carbon countercurrent adsorption, Gold loaded carbon desorption and Gold Desorption Electrolysis, gold mud separation, purification, and smelting ingot casting, triggered carbon activation and regeneration, and cyanide wastewater treatment, and other operation stages
1. Raw material preparation stage
1.1 Crushing stage
Generally, two-stage open-circuit crushing or two-stage one-closed-circuit crushing process is adopted. The gold-bearing materials are pre-screened, and the coarse materials on the screen enter the first crushing stage. After crushing, they will enter the grinding operation after being crushed by the second stage of screening.
The purpose of the operation is mainly to control the crushing ratio of each section and ensure the particle size of the second-stage crushed product. The use of the second-stage and one closed-circuit process can more strictly guarantee the particle size of the crushed material. Generally, the crushing ratio of each section is 3-5. Too large or too small are not conducive to improving crushing efficiency, reducing costs, and protecting equipment. The particle size of the second-stage crushed product should be less than 1-1.5cm, and the maximum height should not exceed 3cm, which can be controlled by adjusting the size of the crusher’s discharge outlet. The principle of “pre-screening, more breaking, and less grinding” must be implemented in production.
1.2 Grinding stage
Two – section two – closed – circuit grinding process is more widely used
The first-stage closed-circuit grinding and grading process consists of a grate ball mill and spiral classifier. The second-stage closed-circuit grinding and grading process consists of an overflow ball mill and hydro cyclone. Combining the pre-classification and inspection classification of the second stage of the closed-circuit grinding and classification process improves the grinding efficiency and ensures the fineness of the product. After the crushed gold-bearing materials pass through the first-stage closed-circuit grinding and grading process, the -200 mesh content in the slurry is 55%-65%. After the second-stage closed-circuit grinding and grading process, the content of -200 mesh material in the slurry can reach more than 90%-95%, which meets the fineness requirements of the all-slime cyanidation process. This operation mainly controls the grinding concentration, overflow concentration, and overflow fineness. General grinding concentration: 75%-80% for the first stage, 60%-65% for the second stage; Overflow concentration: 25%-30% for the first stage, 14%-20% for the second stage; Overflow fineness (-200 mesh content): the first stage is 55%-65%, and the second stage is above 90%-95%.
Grinding concentration is mainly controlled by adjusting the water supply, ore supply, and sand return ratio. If the grinding concentration is too high, increase the water supply, reduce the ore supply, increase the sand return ratio, etc., and vice versa. The overflow concentration can be controlled by adjusting the overflow water supply, the height of the overflow weir, the size of the inlet, the discharge outlet, the overflow outlet, etc. The control of the overflow fineness requires adjusting the height of the overflow weir and overflow outlet, the number of steel balls, proportions of the big and small balls, sand return ratio, grinding concentration, overflow concentration, etc. In short, in the grinding operation, all the technical parameters are related to each other, complement each other, and restrict each other. Therefore, in the process of adjustment and control, it is necessary to consider and coordinate comprehensively.
1.3 Removing chip work
Multi-stage chip removal process.
The first-stage chip removal operation is set up before the crushing, and the wood chips and other debris in the raw ore must be manually detected. The second-stage chip removal operation is located at the overflow of the spiral classifier, using a flat-screen with an aperture of 2-3mm. In the third stage, the chip removal operation is set before the hydro cyclone feeds the ore, and a 20-mesh flat screen is used. The fourth-stage chip removal operation is set up before the concentration and dehydration, using 24-28 mesh arc screens.
In this section of the operation, the debris on the screen must be removed in time, and the use of the screen should be checked frequently, and the damage should be replaced in time to ensure the quality of pulp removal.
The pulp needs to be strictly removed before cyanidation leaching because the wood chips, gravel, fuse, woven bag fragments, slag, and other debris brought in by the raw ore are likely to cause the slurry inlet and grit inlet of the hydrocyclone, and the thickener Blockage of discharge ports, pipes, interstage screens, etc.; the presence of sand and gravel will increase the wear of activated carbon; the presence of wood chips, etc. will adsorb the dissolved Gold and cause the loss of Gold, and the wood chips may turn into fragile in the regeneration kiln Carbon reduces the actual yield of Gold. Therefore, the chip removal operation is essential.
Set up as many dust removal screen levels as possible in the order of fineness.
1.4 Pulping stage
It is mainly carried out in thickeners, and most of them are high-efficiency thickeners, single-layer thickeners, or multi-layer thickeners. The slurry that meets the gold extraction process conditions of the all-slime cyanide carbon slurry method has a slurry concentration of 40%-45%, PH value is 10-11, and slurry concentration of 14%-20% delivered by the grinding operation, PH value is 7-10. This section of the process needs to control the slurry concentration by adjusting the bottom flow rate of the thickener and the amount of flocculant, and control the PH value of the slurry by adjusting the amount of lime added to the ball mill or the amount of sodium hydroxide added to the thickener, So that it meets the requirements of the next step of leaching and adsorption operations.
(Figure 3).
2. Stirring cyanide leaching stage
Stirred cyanide leaching is also called pre-soaking operation, generally composed of two high-efficiency & energy-saving leaching tanks (No. 1 and No. 2) in series. The slurry is transported from the upper operation to the No. 1 tank and then flows from the No. 1 tank into the No. 2 tank by gravity. This section of the operation mainly controls the cyanide ion concentration and oxygen content in the leaching pulp. The appropriate cyanide ion concentration is 0.05%~0.08%, which is owned by adjusting the dosage of sodium fluoride. The oxygen content in the pulp is usually expressed by the aeration amount and the aeration pressure, the general aeration amount is 0.02 m3/m3 min, and the aeration pressure is 100Kpa. In production, it is usually appropriate to uniformly disperse 5~15mm diameter tiny bubbles on the surface of the pulp; it is controlled by adjusting the main valve of the air pump and the inflation valve of each tank.
3. Activated carbon countercurrent adsorption stage
The countercurrent adsorption stage of activated carbon is also called immersion & suction operation. The so-called countercurrent adsorption means that the direction of the activated carbon being lifted and transported by the carbon extractor is opposite to the flow direction of the slurry through the extraction of carbon, a string of carbon, and carbon addition. This operation section generally consists of five high-efficiency & energy-saving adsorption tanks (No. 3, No. 4, No. 5, No. 6, and No. 7) in series and five carbon extractors. In sequence, the ore pulp flows from the No. 2 leaching tank into the No. 3, No. 4, No. 5, No. 6, and No. 7 adsorption tanks. After the gold-loaded carbon is extracted from the No. 3 tank, it is then strung from No. 4 to No. 3 and No. 5 No. 4, No. 6 to No. 5, No. 7 to No. 6, and No. 7 tank is filled with new carbon. The leading technical indicators controlled in this section of the operation are fluoride concentration, oxygen content.. bottom carbon density, stringing speed, stringing amount, the gold content of gold-loaded carbon, tailing liquid gold content, tailing grade, etc.
3.1 Concentration of cyanide in pulp
It is slightly lower than the stirring cyanidation leaching stage, which is 0.02%~0.05%, and it is gradually reduced from the No. 3 tank to the subsequent tanks, and the minimum of the No. 7 tank is 0.02%~0.03%. It is controlled by adjusting the amount of sodium cyanide added.
3.2 Oxygen content of pulp
It is slightly lower than the stirring and leaching stage, controlled by adjusting the gas filling valve of each tank.
3.3 Bottom carbon density
The bottom carbon density is the content of activated carbon per liter of pulp, generally 10~15g/L. To ensure the recovery rate of Gold, usually, the bottom carbon density of the No. 7 tank is slightly higher, 15~20g/L. The base carbon density can be passed by the amount of carbon addition, string carbon amount, and carbon extraction amount to control.
3.4 Carbon stringing speed
Carbon stringing speed, also known as stringing frequency, refers to the number of carbon stringing per unit time. According to the study on the mass balance of Gold in the adsorption system, the product of the speed of stringing carbon and the amount of Gold loaded on the carbon is constant. To maintain a suitable amount of Gold in the carbon, a certain carbon speed must be selected, usually once a day.
3.5 Amount of carbon stringing
To maintain the balance of the total amount of Gold in the adsorption system and maintain the adsorption performance of the carbon in the tank or tank, there should be an appropriate percentage between the amount of carbon string and the amount of activated carbon stored in the tank. This ratio is generally 10-20%. Adjusting the length of time for stringing carbon can control the amount of stringing inflammation.
3.6 Carbon gold loading
Under the premise of ensuring the adsorption rate, the gold loading on carbon should be as high as possible, but the higher the gold loading on the carbon, the more gold is stored in the adsorption system, and the capital turnover will be affected. Therefore, the appropriate gold loading on carbon, a reasonable method of stringing carbon, is significant to the carbon pulp mill. Generally, the final gold-loaded carbon has a 4-6g/kg gold content, which can be controlled by adjusting the amount of carbon extracted.
3.7 Tailings gold content
The gold content in the tailings slurry solution is generally 0.02~01g/m3. When this value is exceeded, it indicates a problem with activated carbon adsorption, and the adsorption rate is reduced. You can increase the bottom carbon density, reduce the gold-loaded carbon content, and shorten the stringing time. To control.
3.8 House and mine grade
Generally, it is 02~03g/t, and the highest is not more than 05g/t. The adjustment and control of this technical index are more complicated. In the existing equipment and technology, it can be comprehensively adjusted and controlled by methods such as improving the grinding fineness, reducing the slurry concentration, reducing the processing volume, and extending the leaching time.
In short, the above-mentioned technical indicators are not isolated but are interconnected and unified, and the role of any adjustment method is not unilateral. Therefore, in the production operation, careful consideration should be made according to the specific situation. , To find out the best control measures to increase the total recovery rate of Gold and achieve the best economic benefits.
4. Gold-loaded carbon desorption and electrowinning stage
The desorption electrowinning of gold-loaded carbon mainly adopts the process of heating and pressurizing desorption, high temperature, and constant pressure combined with a closed-circuit circulation process. There are more mature desorption electrowinning devices with a higher degree of automation control—the preparation of the desorption electro effect: 1% NaOH and 1% NaCN mixed solution. The anode of the electrowinning cell is a stainless steel plate with holes, and the cathode is unique, high-quality steel wool. In the production operation, as long as you frequently observe the various instruments on the equipment and touch or turn the multiple buttons or knobs on the equipment to control the temperature, pressure, flow, voltage, and desorption electrowinning time of the desorption electrowinning operation, you can achieve better performance. Ideal desorption electrowinning effect. Generally, the desorption temperature is 105C, the pressure is 2000Kpa, and the time is 14~16h (when the temperature of the desorption column reaches 70C, the timing starts). The electrowinning temperature is 70C~80C, the voltage is 3~4V, and the electrowinning liquid flow rate is 300L/h. The above technical parameters are easier to control and relatively stable.
5. Separation, purification, smelting, and ingot casting of gold mud
This stage of work needs to be carried out under strict supervision and security conditions. According to the formal method of gold and silver smelting, the electrowinning gold mud should be pyro-smelted first so that the Gold and silver in it will be formed into crude gold and silver ingots, and then concentrated from the gold and silver ingots to further separate and purify the Gold and silver. However, to speed up the capital turnover, the method of directly separating and purifying the electrowinning gold mud, smelting, and casting ingots can also be used.
5.1 Separation and purification of gold mud (acid method)
1)First, add a certain amount of hydrochloric acid to the gold mud, entirely react to remove residual steel wool and some other splashed metals, filter and wash, then add a certain amount of nitric acid, entirely react to remove most of the silver and other splashed metals, and then filter and clean. This step mainly controls the amount of acid added, the reaction time, and the degree of washing. The amount of acid is related to the number of impurities in the gold mud. The reaction time should be determined according to the reaction conditions and actual reaction conditions, but the general reaction should be no less than 2~3h. The degree of washing is very important, every washing must be neutral, and washing with water should be faster.
2)Add 3 to 4 times the weight of aqua regia to the washed gold mud in batches, stir to dissolve the Gold, and then heat and boil it to make the gold enter the solution in an ion state, and filter to obtain the gold-containing solution and sediment. In this step, attention should be paid to the violent reaction when adding aqua regia to prevent the overflow of gold liquid. The reaction time for dissolving Gold is generally not less than 2~3h. Pay attention to the change of sediment color.
3)Sponge gold can be obtained by adding excess anhydrous sodium sulfite to the gold-containing solution. Before this, the gold-containing solution must be acidified to PH=6~7. When adding anhydrous sodium sulfite, add a small amount gradually until it is excessive, and at the same time, keep heating and stirring
5.2 Smelting and casting of sponge gold (coke furnace)
1) Add borax 10%~15%, sodium carbonate 5%~10%, glass powder 3%~5% to the sponged Gold, mix well, put it into the preheated graphite crucible, put it in the furnace for smelting and smelting. The total time is 1.5~2.0h, and the melting temperature is 1200~1300℃. This step should pay attention to control the furnace temperature and melting time and often observe the crucible placement and the melting of the materials in the crucible.
2) After the meeting is complete, take out the crucible with a clamping crucible, and pour the melt into the mold. In this step, it should be noted that the mold must be preheated, and a layer of black smoke with a thickness of 1mm should be uniformly smoked on the inner surface. When casting, pay attention to the order of slow first, then fast, then slow, and the casting time is 10 seconds. After taking out the gold ingot, soak it in dilute nitric acid or hydrochloric acid solution for about 5~10min, wash it with water to remove the acid, and soak it in alcohol for a while, then take it out and wipe it dry. Gold ingot fineness is 99.9%.
6 .Activated carbon activation and regeneration stage
6.1 Activation and regeneration by the acid method
Every time activated carbon is used in a cycle—adsorption-desorption—– it must be activated and regenerated by acid. The specific operation is to use 3% to 5% concentration of the hydrochloric acid solution and degolden carbon to stir in the pickling vessel for 1.5 to 2 hours, then wash with clear water, and then rinse with 1% concentration of NaOH solution until it is neutral. The acid activation regeneration is mainly to remove the acid-soluble substances such as calcium, magnesium, and sodium adsorbed on the activated carbon. It should be noted that highly toxic hydrocyanic acid will be generated during the acid treatment, and appropriate measures must be taken to ensure safety.
6.2 Fire activation and regeneration
Generally, activated carbon is activated and regenerated by fire every 5-10 cycles. Fire activation and regeneration are carried out in a steel pipe kiln. There are two heating zones in the steel pipe kiln. The temperature of the first heating zone is 600°C, and a steam atmosphere is generated. The temperature of the second heating zone is above 650℃, and the carbon is activated and regenerated in this zone. The specific operation is to add wet carbon from the feeding end of the steel pipe kiln. The steel pipe transports the carbon to the discharge end during the rotation process, passing through the air. It can be put into use after cooling. Fire activation regeneration is mainly through heat treatment to eliminate the effect of organic fouling on carbon activity.
7. Treatment stage of cyanide-containing wastewater
The operation of this section consists of two sewage treatment tanks connected in series, which are treated by the alkali-chlorine method. Under alkaline conditions, the bleaching powder is directly added to the sewage treatment tank, stirred, and chlorinated to decompose the cyanide in the sewage to achieve the purpose of detoxification, purification, and pollution elimination. In actual production, the chloride concentration in the sewage is lower than 0.5mg/L by adjusting the amount of bleaching powder. Then the sewage is pumped into the sedimentation tank or tailing pond for natural degradation.
The gold extraction smelting process of the all-peat chlorinated carbon slurry method is highly adaptable to ore. It has the characteristics of simplified process flow, simple process, low investment, low cost, stable process, easy operation, and high total gold recovery rate. It is currently domestic The internationally popular gold beneficiation technology is also the trend of gold beneficiation development.
