The slurry is evenly distributed on the filter belt through the toothed plate of the feeding tank. The head wheel drives the filter belt to move forward at a speed of 0.35 m/min. When vacuum filtration, the filter disc and the filter belt move forward in the same direction and at the same speed, and the slurry on the filter disc is separated by the vacuum driving force. The slurry is divided into several sections on the filter belt by the isolator. After suction filtration and washing, the filter cake is sent to the suction drying zone, and the filter cake is removed into the hopper by the change of the curvature radius of the head wheel and the sheet scraper. After the filter belt is regenerated, tensioned and flattened, it is continuously fed by rolling and feeding. When the stroke device on the vacuum disk hits the contact of the limit device, the stroke of the vacuum filter is cut off, and the return stroke starts. At this time, the filter belt continues to move forward at the original speed. However, the vacuum switching valve starts to operate, so that the filter disc begins to release the vacuum, the filter belt is returned to the original position of the returning cylinder, and the next vacuum filtration stroke begins, and the cycle is repeated.
In continuous vacuum filters, rotary cylinder or Feiness type vacuum filters are most commonly used, because these two types of filters can effectively be used from concentrated slurry (containing 40% to 60% solids) or sometimes The fine particles are separated from the cyanide solution containing a small amount of solids, and it is convenient to wash the solid material. The disc type vacuum filter has the advantages of low investment, small floor space, etc., but the pulp is easy to form agglomerates thereon and affects the washing effect, and the filter cake is not easy to be discharged, so the use is less.
Another continuous vacuum filter worth mentioning is a belt filter. Belt filters have been used for at least 35 years in the paper and sugar industry sectors and have been successfully used for the filtration of cyanide pulp for nearly 20 years. Today, some cyanide plants in South Africa have used 60m2 and 120m2 belt filters consisting of ordinary steel or stainless steel frames, drive wheels, tail wheels and reinforced rubber conveyor belts with horizontal discharge grooves and drain holes in the center of the groove ( Figure 10). The conveyor belt is mounted between the drive wheel and the tail wheel and is supported by an air cushion driven by a variable speed motor. Below the belt are a vacuum box, a vacuum-sealed wear belt and a flexible filtrate discharge hose. The conveyor belt is a grooved belt or a rubber flange is attached to both sides to prevent the slurry from overflowing. When the belt passes the tail wheel, the rubber flange is flattened, the filter cloth is in contact with the conveyor belt, and is fixed by vacuum suction. The slurry is supplied through the slurry distributor and is tightly attached to the filter cloth of the conveyor belt. The vacuum suction filter causes the solution to enter the vacuum box through the drain hole on the conveyor belt through the drain hole and then discharge into the storage tank. The separation crucible divides the belt filter into three zones, namely a (vacuum) suction filtration zone, a washing zone and a suction zone. The filter cloth belt (reverse) is separated from the conveyor belt by the drying zone and the driving wheel. After the filter cake is removed by the discharge roller, the filter cloth belt passes through the jet washer, the tensioning wheel and the automatic distance adjusting system, and again at the tail wheel. Continuous automation with a conveyor belt. In order to grasp the condition of the filter cloth in time, South Africa developed a turbidity meter, and the turbidity of the filtrate was measured by the turbidity meter, so that the operator can know the working condition of the filter cloth at any time.

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The belt filter can be used for multi-stage filtration and washing without re-pulping, and the processing capacity is 1~3 times higher than that of the cylindrical vacuum filter. The filtered precious liquid can be returned to the washing to obtain a rich liquid, or it can be returned to the washing. The filter residue can be drained into a dry filter cake, and the wet tailings can also be drained. Although the belt filter investment in infrastructure, high maintenance costs, and requires careful operation and occasional loss of a large number of disadvantages such as expensive solution, but its low energy consumption, high efficiency, easy replacement of the filter cloth, which is expected in the production of gold A lot of adoption.
Among the filter presses used abroad, the best performance is the circular filter disc hydraulic press installed on the horizontal axis in the United States and the axial flow (candle) filter press in South Africa. Since they are all automated, they replace the plate and frame filter press. However, some old factories are still using the outdated Moore or Butters type intermittent frame filters.
The filtration of the vacuum filter feeds the leached slurry into the filter. Under the suction of the vacuum pump, the gold-containing solution passes through the filter cloth, and the solid material is tightly precipitated on the filter cloth to form a filter cake. In the vacuum filtration of cyanide pulp, the suction of the filter can destroy the flocculation in the filter cake, and the undissolved gold is often dissolved (especially the mud slurry). Therefore, it is important to wash the filter cake. According to the production practice experience, when washing the filter cake with dilute NaCN liquid, use the washing liquid with the same amount of liquid in the filter cake for washing, and wash the gold-containing solution with the mass fraction of 80%~85% from the filter cake. By washing with a washing solution containing twice the amount of the filter cake, 98% of the gold-containing solution can be washed out from the filter cake. Under normal circumstances, the filter cake should be washed several times. The first addition of dilute NaCN solution (or lean liquid) will adjust the filter cake to a 50% concentration slurry, wash and filter, then wash with water, and discard the tailings.
3) Dense-Filter Combined Washing The dense-filter combined washing process concentrates on the advantages of both thick washing and filtration washing, which is beneficial to both the washing rate and the environmental protection. Therefore, this washing process is used more in domestic cyanide plants, as shown in Figure 11.

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The characteristics of the combined washing process are: start washing with thickener, multi-stage countercurrent washing with single-layer thickener or multiple single-layer thickeners, counter-flow washing with multi-layer thickener, and finally using filter to carry out liquid Solid separation. The filtrate can be used as a washing water to return to the previous level of washing operation, or can be used as a immersion gold slurry water returning process to achieve the purpose of recovering dissolved gold and cyanide.
4) Wash column washing method The washing column is now used in hydrometallurgy of non-ferrous metals. Although a cyanide plant in China has been used in the washing test of cyanide pulp, it has achieved good washing effect, but in the cyanide gold-plating plant. There are no examples of applications in production.
The wash column is an elongated circular hollow column containing a slurry distributor and a wash liquid dispenser (Fig. 12). The slurry is supplied from the top of the column, and the washing liquid is supplied from the interface of the washing section and the compression section. In the countercurrent movement of the slurry and water, the solid material settles at the bottom of the column and is discharged from the discharge pipe; the gold-containing solution is discharged from the overflow raft at the top of the column to achieve solid-liquid separation.

3. Zinc replacement immersion gold The method for extracting gold from cyanide solution is: zinc substitution, activated carbon adsorption, ion exchange resin adsorption, aluminum replacement, electrowinning and extraction. From the beginning of the cyanidation process to the present, zinc replacement is the main method of sinking gold. However, since the 1970s, activated carbon adsorption and ion exchange resin adsorption have been widely used throughout the world. It can be considered that the role and status of the adsorption method will be greatly improved. Aluminum replacement method was used to mine silver cyanide process, but aluminum-substituted gold not been promoted. The electrowinning method and the extraction method are still in the experimental stage. Zinc replacement method is widely used today in the continuous vacuum precipitation method of zinc powder used in the Merrill Crowe cyanide plant. The cyanide noble liquid is replaced by zinc zinc precipitate which is commonly known as “cyanide gold mud”. Smelting.

Rotary Drilling Rig

1. XP-20A is applied to soft ground stabilization, seepage control of basement of high-rise buildings, renovation of big river and levee, reinforcement of railway, highway and pier, etc.