Non-roasting process for extracting gold and silver from refractory sulfide concentrate
For the gold-containing arsenic, pyrite concentrate of disseminated gold dissociation, so that the next - Step cyanide, in recent years many new hydrometallurgical method. From the environmental point of view, it is reasonable to adopt these methods, but in addition to the process effects, these methods have many serious shortcomings. Mechanical crushing with planetary gear mills and jet mills is a promising process in this area. In the ultra-fine grinding, the dissociation ability of the gold-containing sulfide minerals can be improved, and the decomposition of the gold mineral can be realized under the condition that the conditions are not strict, the chemical consumption is moderate, and the equipment shape is simple. As can be seen from the table, the index of adsorption cyanidation of concentrates depends on the pre-alkali treatment scheme. When the spray process is combined with the leaching of sodium hydroxide solution (according to Table 1), the highest recovery string of precious metals can be guaranteed. At this time, the recovery rate of gold was 88.9% and silver was 96.2%. The adsorption cyanide of the jet milled concentrate is not more than 77.3%, As 71.3%, and the content of the leaching slag is 12.15 and 76 g/ton, respectively, without prior alkali leaching. When the treated product has a particle size of -6 microns and -15 microns, in fact, the same metric can be achieved. The above facts prove that it is possible to perform jet grinding with equipment used in production. The consumption of caustic soda is 85 kg / ton and cyanide 10 kg / ton. [next] Pp Saving Case Box Mold,Pulp Egg Box Mould,Injection Mould For Fan,Die Casting Mould Part Yuyao Hongzhou Plastic Technology Co., Ltd. , https://www.hongzhoumould.com
The raw material used in this test is one of the concentrates of Yakutia, and the concentrate is finely ground and then treated by hydrometallurgy. The study was carried out with concentrates containing 56 g/t Aa, 260 g/t Ag5.4% As, 16.8% S and 10.0% C. Free gold does not exceed 6~8%, there is no natural silver .
Jet milling was carried out using a mill of MCII-05 and MCII-005. Using compressed air as energy carrier, the gauge pressure is 0.45 ~ 0.50MIIa, when consumption 80 m 3 / hr. Approximately 100 kg of concentrate was processed under various grinding regimes. The material imbalance is 1.0~0.5%. The fine material is mainly lost with the bag filter exhaust gas.
The rotation speed of the grader rotor is increased from 20 to 50c-1, and the fine fraction yield can be increased: the content of -6+0 micron is increased from 45% to 87%, in this case, -9+6 microns. The grade of the grade decreased from 49% to 12%, while the medium grade particles decreased from 5 to 3.5 microns.
The sulfide minerals in the concentrates in the above-mentioned size range are characterized by high chemical activity (9 to 15 times higher than that of the original minerals), and can be decomposed with sodium hydroxide solution at normal temperature and normal pressure. Under this condition, arsenic is mainly transferred into the solution in the form of arsenate ions, and sulfur enters the solution in the form of thiosulfate and sulfate ions. Under the optimal conditions, arsenic pyrite is decomposed by 80-85% and pyrite is 40~45%. After mechanical crushing, the adsorption capacity of the pulverized mineral composite is increased.
In order to suppress secondary adsorption of Au and As, adsorption leaching must be carried out using an AM-26 type anion exchanger (8.05%). The recovery of precious metals during cyanidation depends on the pre-alkali treatment time (Ï„). If this time is increased from 12d to 48 hours, and other conditions are also ideal: liquid: solid = 6:1, sodium oxide concentration is 50 g / decimeter 3 , then the Au leaching rate will be 75 The % increased to 89.5% and the silver leaching rate increased from 81.5% to 96.6%. The cyanidation time is 48 hours, the liquid: solid = 4:1, and the NaCN concentration is 0.4%, the cyanidation is more reasonable. The leaching kinetics curve of the precious metal during the cyanidation of the concentrate is shown in Fig. 1. 
In order to remove arsenic from the alkaline solution for reuse, the leaching slurry should be concentrated and filtered. The unit area for concentration is 0.58~0.85 m2 (ton, day and night). When polyacrylamide is added, it can be reduced to 0.18~0.23 m2 (ton, day and night). Concentration results of the leached pulp product indicate that the amounts of -6 and -15 microns are actually equal. The unit productivity of the filter is 3~7 tons / (m 2 , day and night), that is, the usual process equipment can be utilized.
The obtained alkaline solution contained As 2 to 3.9 g/dm 3 and S 2.8 to 8.9 g/dm 3 . The remaining concentration of sodium hydroxide is 30 to 35 g/dm 2 . Most of the arsenic in the alkaline solution can be precipitated by the usual method of adding lime, and the mother liquor can be recycled (the residual concentration of As does not exceed 0.3 to 0.4 g/dm 3 ). Part of the sulfur precipitates simultaneously with arsenic, and the precipitate contains 37.6% calcium arsenate and 16.8% calcium sulfate, which means that the product actually meets the process requirements of arsenate. Sodium hydroxide is regenerated 20 to 30% during the treatment. The solution was purged playing license to the limit concentration, may be added in the phosphate solution for deep purification.
According to the results of the concentrate treatment research, the following processes are recommended, including: air jet grinding (milling the prepared product to a particle size of -15 microns), leaching with sodium hydroxide solution, adsorption cyanidation, and pre-existing products according to production. The metal flow desorbs gold and silver, and the alkaline mother liquor is repeatedly purified for recycling or disposal (Figure 2). Technical and economic calculations show that the cost of concentrate processing is 30% lower than the actual situation of MJI3 after arsenic removal.