Types of Gold Extraction Equipment

01Composition of the cyanide leaching system

The conventional cyanide leaching process generally includes three steps: leaching process, washing process, and zinc powder replacement process. In the CIP and CIL process, we use activated carbon to extract gold, so the last step of these two processes becomes activated carbon adsorption process.

The main gold extraction equipment used in the cyanide leaching system are as follows: the leaching agitation tank, the high-efficiency low-consumption rapid desorption electrowinning system, the washing thickener, the zinc powder replacing device, and etc. The leaching agitation tank is applied to the conventional cyanide leaching process, the CIP and the CIL process; the desorption and electrowinning system is mainly applied in the stage of activated carbon adsorption; the zinc powder replacement device is the main gold extraction equipment used in the zinc powder replacement stage; The thickener is the primary gold extraction equipment used in the washing stage of the conventional cyanide leaching process.

This article will be followed by a separate explanation for each device.

02Gold ore leaching agitation tank

The leaching agitation tank is mechanical agitation equipment used in cyanide leaching operation of gold mine. There are two kinds of leaching agitation tank: single impeller leaching agitation tank and double impeller leaching agitation tank. The working principle of leaching agitation tank is: the slurry flows from the top to the bottom in the center under the action of impeller pushing and throwing. Then, it is diffused through the peripheral baffles, and air is supplied to the lower end of the shaft (the air is fed by the hollow shaft) and the slurry is circulated upward to form a uniform suspension mixture.

Compared with the single impeller leaching agitation tank, the advantages of the double impeller leaching agitation tank are fourfold:

1. The movement of ores is smooth, the slurry is evenly mixed, and the power consumption is small,

2. The air is uniform because the air entering the tank through the drive center shaft will be agitated by the impeller.

3. The device has a compact structure and is easy maintenance

4. The impeller has low speed and long service life because of the rubber liner.

The shortcomings of the long double impeller leaching agitation tank are as follows:

1. The double impeller leaching agitation tank limits the fineness of raw materials----usually -200 mesh is required to be more than 90%, which requires that the raw materials must be finely ground to use. And the fine grinding equipment has high power consumption, fast wear, and maintenance troubles.

2. The double impeller leaching agitation tank limits concentration. When the concentration is in the range of 40-45%, the leaching effect would be best.

Now the mines and refineries need continuously leaching, so the slurry concentration deeply affects the leaching rate of gold. If the slurry concentration was too low, the leaching time of pulp would be reduced; if the slurry concentration was too high, the requirements on the pump would be stricter (Generally, the conveying concentration of slurry pump should not exceed 30%. Once it exceeds 30%, the conveying quantity would be affected). In short, double impeller leaching agitation tank has the following advantages, reliable, easy to operate, convenient to maintain, and highly applicable, except requiring high concentration and fineness of the slurry, which made it widely used in the gold processing industry.

03Gold ore desorption Electrolysis System

The desorption electrolysis system is used for extracting gold adsorbed in activated carbon, which usually works under high temperature and high-pressure conditions, including carbon lifting pump, carbon screen, desorption solution tank, desorption column and others. The advantages of this gold extraction equipment system are as follows:

1. Fast desorption, short time and high efficiency

The working temperature of desorption electrolysis system is as high as 150°C, which is about 55°C higher than the working temperature of the heating and atmospheric pressure process; the pressure is up to 0.5 Mpa, which is 0.2 Mpa to 0.5 Mpa higher than the normal temperature and pressure process. Under this high temperature and pressure condition, the desorption electrolysis rate of gold-loaded carbon is obviously accelerated----only 2 to 6 hours to desorb 98% of the gold, which greatly improves the absorption efficiency, shortens the desorption time by nearly ten times, and reduces the lean carbon grade to 50g/t. It also has a regenerative activation effect on activated carbon.

2. No cyanogen desorption, low energy consumption

Compared with the heating atmospheric pressure process, the desorption electrolysis system only needs sodium hydroxide as the desorption solution, and does not need sodium cyanide, which not only reduces the operating cost, but also meets the requirements of environmental protection. In addition, the whole desorption process is basically carried out under the same temperature and pressure, desorption solution can be directly into the electrolytic cell without cooling treatment, which greatly saves the consumption of heat energy, and the consumption of electricity is only 1/2 ~ 1/4 of the heating atmospheric pressure process, truly realizing cyanogen free low-consumption desorption.

3. High degree of automation and intelligence

During the operation of the system, the amount of liquid in the system will fluctuate to some extent due to the liquid vaporization and pressure change of the system. Therefore, technicians specially set up a liquid level buffer mechanism to automatically offset liquid level changes and maintain the normal operation of the system. In addition, for it is configured with a temperature control system, when the temperature reached set value, the system will automatically pick the open part of the electric heater, residual electric heater automatically maintain system working temperature, when the system temperature is lower than the set limit, was torn open electric heater automatically into start, ensuring that the system has been stable in temperature range.

4. Triple security protection measures

Considering the safety of the system, the technicians took three safety measures.

A. the system itself is intelligent. The electric heater can be automatically put into or stop working according to the circulating pump running state or pressure level, without manual operation.

B. Automatic pressure limiting and pressure releasing mechanism. When the system pressure rises to a certain value, this mechanism will automatically open the pressure relief and adjust the pressure to the normal value.

C. Safety valve. If the above two measures fail, the safety valve will automatically start to avoid causing great losses.