Around 1880, the company knew about the method of recovering gold from solution with activated carbon. However, the problem of desorbing gold from charcoal cannot be solved. In order to recover gold, activated carbon must be calcined, and activated carbon is very expensive. This greatly restricts the development of carbon extraction technology. It was not until the 1970s that the method of recovering gold from gold-loaded charcoal was developed to enable the reuse of activated carbon, which led to a rapid development of the carbon-paste gold extraction process. The key to the process consists of three steps: the first step, the dissolution of gold from the slurry - leaching and adsorption; the second step, the desorption of gold from the gold-loaded carbon - desorption; the third step, depositing gold from the gold-containing solution - Electrowinning. In recent years, it applied to the production of alumina years axial flow stirring tank, after improvement has been successfully used in the CIP process. The axial flow agitation tank has two types: air agitation and mechanical agitation. In the center of the axial flow mechanical agitation tank (Fig. 2) there is an inflation tube with a downwardly pumped hydrofoil impeller. Since the impeller has an axial flow type and the impeller section is curved, it has the characteristics of small impeller tip speed, large axial flow velocity, and small radial flow velocity. There are many small grooves in the wall of the central inflation tube for the small circulation of the slurry. This tank differs from other mechanical agitation tanks in that it must be filled with slurry to operate, and the ratio of the height to the diameter of the tank can be up to 2:1. The four axial-flow agitation tanks used in the Pinson gold ore plant in the United States have been in operation for three years. Practice has proved that if the diameter of the central inflation tube is properly selected, its power consumption is only 30% of the ordinary mechanical agitation tank, and the solid material is uniformly suspended, the activated carbon wear is small, and the gold recovery rate is high, which solves the problem of oil pollution and power failure. Sand and cyanide consumption are high, and it is expected to become the main equipment of the carbon pulp plant. The pre-screening of the activated carbon is carried out before the adsorption of the activated carbon. The function of the pre-screening is to remove the impurities in the slurry and avoid mixing with the gold-loaded charcoal in the future. A 28 mesh (0.6 mm) sieve is generally used, and the pre-screened sieve is mainly wood chips. The sawdust easily blocks the separation of the slurry and the gold-loaded carbon sieve. In addition, in the grinding, gold particles, quartz and other mineral particles are embedded in the wood chips, so that the gold content is increased; in the cyanidation process, the wood chips not only adsorb the gold cyanide complex, but also use the general washing method, it is difficult to put the wood chips on Gold elutes. At the same time, in the carbon slurry method, a small amount of wood chips present in the adsorption tank will reduce the adsorption efficiency of gold. Therefore, before the slurry is immersed, it is necessary to remove the swarf by 1~2 times. Compared with the carbon leaching method, the carbon slurry solution has a high gold concentration, and the amount of carbon stored in the tank is small, so the amount of carbon deposited is also higher. The carbon leaching method usually does not add carbon to the first two tanks, and specializes in gold dissolution, the purpose of which is to increase the amount of gold carried by the carbon. 2) Bridge Screen The Bridge Screen is another vertical fixed screen that is currently being used in selected plants in the United States and South Africa. The maximum length of the sieve is approximately equal to 4 times the diameter of the carbon slurry tank. A sieve usually consists of more than 10 detachable sieve plates, the sieve passes through the groove wall of the adsorption tank, and the operation platform is arranged in the middle of the bridge sieve. When the adsorption tanks arranged in a step are arranged in a single row, the bridge sieve adopts a straight line arrangement. (Figure 5). When the adsorption tanks are arranged in a double row, the bridge screens are arranged at right angles (Fig. 6). The bridge screen operates on a similar principle to the surrounding screen and also cleans the screen surface with high pressure air. When the raft is added to the screen surface, the flow rate can be increased to 50 t/m 2 . Self Balancing Electric Scooters It has an invisible stand that can stand when no one is using it,more safety and more convenient for everyone. Scooters Electric,Self Balancing Electric Scooters,Electric Scooters Powerful Adult Foldable,Off Road Self Balancing Electric Scooter Yongkang Mysail Technology Co., Ltd. , https://www.mysail-scooter.com
1. Leaching and adsorption
In the carbon slurry CIP process, the leaching tank is used for cyanide leaching of the slurry, and the carbon slurry tank is used for the adsorption of gold by activated carbon. In the CIL process, the leaching of the slurry and the adsorption of gold are carried out in the same tank, so it is generally referred to as a leaching tank or a carbon slurry tank. In order to improve work efficiency, gold leaching and recovery, and reduce carbon consumption, various studies have been conducted on improving the structure of carbon slurry tanks. Nowadays, for the slurry of -0.208mm (-65 mesh) or 70%~80% -0.074mm (-200 mesh), the Dole stirring tank and the Pachuca air stirring tank which are stirred at low speed center are often used. In order to reduce the wear of carbon, the Masbate plant in the Philippines uses a rubber-coated double propeller agitation tank to reduce the speed of the impeller tip (Fig. 1). 
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The slurry from the leaching operation is fed into the first adsorption tank to enter the adsorption operation, and continuously flows through several adsorption tanks in series, and the activated gold is used to adsorb the gold dissolved in the slurry, and then discharged from the last adsorption tank, which is the cyanide tail. mine. Fresh activated carbon is added to the last adsorption tank, and the carbon is lifted by an air lift pump or a concave impeller vertical centrifugal pump to make countercurrent contact between the activated carbon and the slurry. The gold-loaded charcoal discharged from the first adsorption tank is sieved and washed before being sent to the desorption process.
Separation of pulp from charcoal is achieved using a sieve. The activated carbon used in the carbon slurry method usually has a particle size of 6 to 16 mesh, and the carbon pre-screening is generally 20 mesh. Thus the slurry fed to the first adsorption tank is typically screened on a 28 mesh screen to remove large particulate material. When the cyanide tailings leave the last adsorption tank, they are also sieved on a 28 mesh screen in order to recover the fine carbon and send it to the smelting to recover the adsorbed gold. The middle sieve is 20 mesh.
The factors affecting the adsorption efficiency include: the concentration of carbon in each ton of pulp, the number of adsorption tanks, the relative speed of carbon movement, the residence time of the slurry in the adsorption section, and the amount of gold carried by the carbon. These parameters are determined experimentally and empirically based on the change in the grade of gold fed to the slurry and the gold content of the final discharged slurry. Generally, about 40g of charcoal is added per liter of slurry, and 4 to 7 adsorption tanks are used. The adsorption rate is 99% or more.
Studies have confirmed that the adsorption equilibrium capacity of carbon to gold is closely related to the concentration of gold in liquid (see Figure 3). The adsorption isotherm of carbon is similar to that obtained when ion exchange and solvent extraction. The equilibrium concentration in the solution is almost in the range of (0.1~10)×10 -6 . It was also found that the lower the gold concentration, the slower the equilibrium was established. Therefore, in order to obtain tailings with extremely low gold content, it is necessary to have a longer residence time and increase the concentration of carbon in the slurry. This means that the final amount of gold on the charcoal will be significantly lower than the equilibrium loading that it can reach. This has been confirmed by production practices. In general, the higher the concentration of the solution gold, the higher the amount of gold loaded. [next]
Carbon adsorption system equipment requirements: 1 in the adsorption tank, the carbon and slurry should have the most complete contact; 2 loading gold and slurry on the sieve for the most effective separation; 3 to reduce the wear of the carbon particles in the entire adsorption system as much as possible; 4 In the adsorption tank should try to avoid the phenomenon of short circuit of the slurry.
2. Intermediate sieve
The intermediate screen is the key equipment for the reverse process of slurry and charcoal in the charcoal process plant. Vibrating screens and fixed screens are used in each factory. The fixed sieve can be further divided into a peripheral sieve, a bridge sieve and an immersion sieve.
1) Peripheral screen The peripheral screen is a kind of vertical fixed screen developed by South Africa. It is currently used in factories such as the Pingsen plant in the United States. The maximum length of the sieve is several times the diameter of the adsorption tank. It is installed around a series of stepped suction tanks, and the slurry and charcoal are lifted from the tank to the screen by an air lifter. After separation, the activated carbon is returned to the tank, and the slurry flows through the peripheral screen to the next carbon slurry tank (Fig. 4), and the sieve is cleaned with high pressure air. Since the sieve is fixed, the activated carbon is less worn. However, with such a sieve, the collection of the slurry is difficult, the operation and maintenance are inconvenient, and a wide operating platform is required. [next]