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Application of Hydrocyclone in Gold Ore Tailings

Xinhai 2020-05-26(02:05:07) 333 0

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In this post, we are talking about the application of hydrocyclone in gold ore tailings.

We are going to introduce 4 application in gold ore tailings:

  • Gold tailings filling

  • Gold tailings classification

  • Gold tailings preconcentration

  • Gold tailings enrichment

Let's dive right in!

The hydrocyclone is a high-efficiency classification equipment that separate two-phase fluids by centrifugal force fields. It can carry out some operations such as liquid clarification, slurry concentration, solid particle separation, and separation of non-mutual solution. Hydrocyclone has been widely used in mineral dressing due to its huge merits including its simple structure, no moving parts, compact equipment, small footprint, low cost, large processing capacity, easy installation and maintainance.

In recent years, hydrocyclones have greatly applied in the beneficiation industry, especially for the tailing treatment. 

hydrocyclone used in gold ore tailings

1.Gold Tailings Filling

At present, most mines use tailings to fill the mined-out area. Tailings need to be desilted (-30-70um) to obtain high concentration (about 70%) tailings sand which also needs special treatment before filling. The requirement of tailings sand is to obtain the high-concentration grit by removing the fine-grained grade. Generally, the equipment used in this operation are desilting hopper, inclined thickener, and spiral classifier. Because of the characteristics of simple facility and convenient configuration, cyclone is the best equipment for tailings filling. It can achieve the dual purpose of desilting and increasing the concentration by using the cyclone to prepare the filling material in the mined-out area.

In order to increase the backfill rate of tailings, the gold beneficiation plant needs to increase the sand sedimentation rate of the cyclone and ensure the sand sediment concentration. According to the theoretical calculation and the actual measurement of the flow distribution and pressure loss of the cyclone, the dressing plant design a test plan of the two-stage cyclone in series:

The tailing slurry is pumped into the first-stage hydrocyclone, and most of the solid particles settled through the concentration and grading are discharged through the grit outlet. It is unnecessary to add a transfer pump, the sand setting of one-stage and two-stage hydrocyclones can be used for filler.

The source of the test material is from flotation gold ore tailings, the particle size is -200 mesh 53.7%, the feed concentration of the cyclone is 20%, and the feed pressure is adjusted by the frequency converter. On the basis of the test conditions, the overflow pipes and grit nozzles needs to adjusted. The specific process is as follows:

Schematic diagram of flotation gold ore tailings test

The test results found that when the feed concentration was 20%, the two-stage concentration and dehydration of the series hydrocyclone, the overflow concentration could be reduced to about 6%, the comprehensive sand production rate of the series hydrocyclone was 78.3%, and the sedimentation flow rate was the total treatment 20.23% of the amount.

2. Gold Tailings Classification

Generally, the gold beneficiation plant will reasonably research and apply the separation of coarse and fine particles of the tailings classification based on the loss of the tailings particle size metal amount without affecting the original production, so as to further recover the gold in the tailings and improve the concentration recovery rate, make full use of mineral resources, and improve the economic benefits of enterprises. When classifying gold mine tailings, hydrocyclones are often selected for operation. The hydrocyclone is used to classify the coarse particles of the tailings. The classification efficiency is high, the processing capacity is large, and the operation flexibility is well, which reduces the waste of resources to a certain extent.

In order to improve the recovery rate, a gold ore flotation plant uses a hydrocyclone for classification. Then the underflow sorts after grit grinding, and the overflow is sent to the goaf for filling. In the light of the actual situation of the tailings, theoretical calculations show that when the concentration of the cyclone reaches more than 70%, it can achieve a better grinding effect. In order to achieve the best effect, the plant has designed a large cone angle hydrocyclone whose characteristic is that the fluid resistance becomes larger as the cone angle of the cyclone increases, so that when the liquid moves in the large cone, the tangential velocity increases Large, downward resistance increases, thereby reducing the sedimentation rate of the hydrocyclone.

Samples of tailings were intercepted on site, with concentrations ranging from 25% to 35%, -200 mesh content from 57.6% to 66.4%, -150 mesh content from 70% to 74%, and feed pressure at 0.1Mpa. It can get the required experimental data and do some analysis by adjusting the diameter ratio between the sand nozzle and the overflow pipe of the cyclone.

The test results found that when the feed concentration was 25% -30%, the content of -200 mesh in the cyclone reached 83% -98%, the content of 150 mesh reached 100%, and the concentration of grit was 72% -73%. The yield is 34% -43%, which basically remains stable. According to the calculation of 200 mesh and 150 mesh, the hydrocyclone classification efficiency is higher.

3.Gold Tailings Preconcentration

Thickeners is the traditional equipment used for concentrating and dehydrating tailings. Generally, the tailings concentration can be increased from 15% -20% to 35% -40%. However, the thickener covers a large area, requires high investment, and limits the control of underflow concentration. The hydrocyclone covers a small area, requires little investment, and has good rapid concentration. In general, the concentration of tailings can be increased from 10% -40% to 45% -70%.

At present, most gold mines use hydrocyclones and thickeners in combination to improve concentration effect. Before the gold mine tailings are concentrated in the thickener, it will separate coarse-grained tailings that are easy to concentrate from the tailings by cyclone, and then the hydrocyclone overflow is sent to the thickener for concentration. In this way, it not only can get high-density grit and improve the tailings processing capacity, but also can reduce the load of the thickener and facilitate the transportation of subsequent processes.

hydrocyclone used in gold tailings preconcentration

According to the existing experimental research results, the concentration of grit of the cyclone can reach more than 60%, and the grit yield is 40% -70% in a gold rock tailings process. The comprehensive tailings concentration can reach 45% -50%. The promotion of this combined process can not only play the role of tailings concentration equipment, but also reduce the investment of thickeners.

4.Gold Tailings Enrichment

Gold mines often contain a lot of valuable associated minerals, such as iron, silver and copper. When processing gold ore, it is necessary to not only improve the grade of gold rock, but also comprehensively recycle other by-products. However, sometimes the gold ore tailings still contain a relatively low amount of gold after sorting. In order to achieve maximum recovery and improve the recovery rate of metals, the mines use hydrocyclone to enrich and recover low-grade gold in tailings accroding to the characteristics of concentration, large processing capacity and operation flexibility.

There is a copper-gold ore tailings with lower grade copper-gold content (copper grade 0.07%, gold 0.08g / t). The inlay size of the tailings is fine. But on account of the large processing capacity, copper, gold and gold Granular monomer gold is very valuable for recycling among the coarse-grained grades. The mine chose a short-cone hydrocyclone to enrich and recycle it.

After a semi-industrial test of cyclone recovery of copper and gold in tailings, a short-cone hydrocyclone was used to enrich the total tailings once, then it can get similar grit of the original ore. The yield of test tailings was 9%, the copper grade was 0.18% -0.25%, the gold grade was 0.08- 0.16g / t, and the enrichment ratio is 2.8 times. According to the conventional grinding-floating process, the grit is further sorted to obtain a concentrate with a copper grade of 18% and a gold grade of 6.88g / t. The comprehensive recovery rate of copper and gold (relative to the original ore) increased by 2.04% and 1.85% respectively.

Conclusion

The hydrocyclone is increasingly used in the tailings process of concentrators due to its unique concentration and classification performance. However, the process requirements vary from the nature of tailings in different dressing plants. In order to give full play to the hydrocyclone's efficient operating capacity, it's recommended that each mine owner should choose the appropriate hydrocyclone structure and combination form according to the actual situation.

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