Production Practice of Flotation Process of a Gold Ore Containing Arsenic, Antimony and Organic Carbon

A gold mine of gold resources in Yunnan Tin abundant gold reserves of more than 75 t. Ore type containing arsenic, antimony, and organic carbon fine grained disseminated refractory gold ores. After the experimental research and the beneficiation process plan, the ore is firstly subjected to a flotation process to enrich the gold, produce gold concentrate, and then process the gold concentrate to reduce the investment and cost of the ore development and utilization.

The company's existing 300t/d flotation plant is planned to be expanded to 2000t/d. The recovery rate of flotation gold in production is low, and the economic benefits of enterprises are poor. In order to expand the scale of the development of gold ore fields and clear the obstacles in flotation technology, it was decided to use the existing 300t/d flotation plant to float on the characteristics of the ore gold and its carrier minerals, including arsenic, antimony and organic carbon. The improvement of the selection process is optimized to improve the gold flotation recovery rate.

First, the nature of the ore

The results of multi-element analysis of raw ore are shown in Table 1.

Table 1 Multi-element analysis results

The carbon phase analysis of the ore is shown in Table 2.

Table 2 Analysis results of raw ore carbon phase

The sulfur phase analysis in the ore is shown in Table 3.

Table 3 Results of raw ore sulfide phase analysis

Ore less metallic minerals, accounting for 3.84%, mainly pyrite, marcasite, a small amount of stibnite, arsenopyrite, limonite, occasionally yellow copper ore, sphalerite, galena, hematite, magnetite and the like; non-metallic minerals are quartz, sericite, calcite, dolomite, feldspar a small amount of graphite carbon, clay minerals, chlorite. The results of mineral composition determination are shown in Table 4.

Table 4 Determination of relative content of ore minerals

Metal sulfide minerals are closely related to gold. The results of particle size detection of sulfide minerals are shown in Table 5.

As can be seen from Table 5, the metal sulfide has a fine particle size of less than 0.037 mm and accounts for 73.1%. Among them, the size of the stibnite is relatively coarse, mostly between 0.037 and 0.074 ram. The size of the arsenopyrite is small, generally about 0.01mm, which is not conducive to the monomer dissociation of sulfide during the grinding process.

Table 5 Sulfide particle size test results

The gold particle size of the ore is fine, and the maximum gold particle seen under the microscope in the light sheet and the agglomerate sheet is 8.5 μm, and the others are mostly 2 to 5 μm. Gold in the sulfide has not been found in a large number of microscopic examinations. The selective gold analysis showed that the gold content of the sulfide accounted for 86.26% of the total gold. This part of the gold is microparticle gold and submicroscopic gold. The gold mineral particle size measurement results are shown in Table 6.

Table 6 Gold mineral particle size measurement analysis results

It can be seen from Table 6 that most of the gold is less than 5 μm. In particular, most of the gold in the sulfide is a submicroscopic gold, and it is difficult to dissociate the gold mineral monomer by mechanical grinding.

For the -0.074mm 90% of the ore, the selective gold dissolution method was used to detect the occurrence of gold in the ore. The results are shown in Table 7.

Table 7 Status of gold occurrence

Second, the original production overview and problems

The original production process is shown in Figure 1. The original production technical indicators are shown in Table 8: The original production process has problems:

(1) The original process adopts a rough selection, secondary selection, and secondary sweeping process structure. The tailings are sorted by a cyclone, and the overflow is used as the final tailings, and the grit is re-floated and then floated. The cyclic load in the process is difficult to operate and shortens the flotation time. The results of the process test indicate that the flotation time is only 38 minutes. The results of cyclone overflow and grit analysis showed that the overflow gold grade was 0.81g/t, and the grit gold grade 0.86g/t gold was not effectively enriched.

Figure 1 original production process

Table 8 Original production technical indicators

(2) The structure of the flotation tank is unreasonable, resulting in a poor working condition of the flotation tank. Some flotation tanks are grooved, and some flotation tanks do not scrape foam.

(3) The I-stage ball mill is not standardized due to the steel ball proportioning and supplementing system. The II-stage grinding products have not been subjected to control grading, resulting in lower grinding fineness and insufficient dissociation of sulfides. The results of the process test show that the fineness of the I section is -65 mesh, which accounts for 65%, the fineness of the second section, which is 200 mesh, accounts for 82.5%, and 34.6% of the sulfides in the tailings have no monomer dissociation. In addition, because the φ350mm cyclone often evacuates the ore pump, the working condition of the cyclone is unstable, the ore is uneven, the classification efficiency is low, and the flotation slurry surface is unstable.

(4) Due to the unsmooth discharge of the bottom flow of the slurry tank, water is often added to the mine, resulting in low concentration of flotation slurry. According to the process investigation, the concentration of coarsely selected pulp was 16.01%, and the concentration of sweeping slurry was 15.66%.

(5) The main gold-bearing minerals in the ore are pyrite, stibnite and arsenopyrite. Because the surface of arsenic and antimony minerals is more susceptible to oxidation, and because of the high carbon content, a large number of flotation reagents are adsorbed. Therefore, high-efficiency collectors and activators are needed to enhance the ability to capture useful minerals. The original process collector used a single Dinghuang drug, the amount of 700g / t is large, the effect is poor, 18.92% of the monomer sulfide in the tailings is not floating.

Third, the technical transformation program

In response to the problems existing in the original production, combined with the actual production, the technical transformation of the process has been carried out.

(1) Improve the process structure. The original cyclone tail is changed to stage grinding, flotation and tailing, so that the process is smooth and easy to operate.

(2) Improve the flotation cell structure to improve the sorting environment and improve the flotation mineralization effect.

(3) Install a return pipe at the overflow end of the cyclone to avoid evacuation of the sand pump to ensure the classification efficiency of the cyclone and the stability of its working conditions.

(4) The control and classification of the second-stage grinding products shall be carried out to improve the fineness of the second-stage grinding.

(5) Install a KP600 hose pump in the bottom of the slurry tank to stabilize and increase the concentration of flotation pulp.

(6) Establish a scientific ball mill ball ratio and supplement system to improve the fineness of grinding and the fine-grained capacity of the ball mill.

(7) In view of the characteristics that the ore and strontium minerals are easily oxidized and the organic carbon content is high, sP activator is added, and butyl xanthate and DNJ are combined to increase the synergistic effect of the agent.

(8) Increase the number of sweeping operations and extend the flotation time. Add a 1.1m flotation machine to the selected II tailings to avoid the selection of the II tank.

Fourth, the process flow and technical indicators after the transformation

The process flow after the transformation is shown in Figure 2.

The production technical indicators before and after the process transformation are shown in Table 9.

Table 9 Production technical indicators before and after transformation

V. Conclusion

1. Change the original production process to the stage grinding and floating process, which is easier to operate, and the early use and quick harvest of useful minerals in the ore containing higher impurities.

2. Adjusting the structure of the flotation machine, improving the sorting environment, and improving the mineralization effect of the flotation slurry, ensuring the stability of the indicators and smooth flow.

3, the establishment of a scientific ball mill steel ball ratio and supplement system, the grinding fineness from a 200 mesh accounted for 82.5% to a 200 mesh accounted for 92%, which is conducive to the monomer dissociation of sulfide.

4, butyl xanthate and DNJ combination medication, increase the synergy effect of the agent, add SP activation, increase a sweep, extend the flotation time and so on is an important measure to improve the flotation recovery rate.

5. Production practice shows that the recovery rate can reach 90.62% when the candidate grade is 3.32g/t, which is 8.82% higher than that before the technical transformation;

The newly added output value was 8.89 million yuan, and the new profits and taxes were 4,663,300 yuan. The success of technological transformation of the process provides a good technical support for the large-scale development of the gold field.

Process