With the gold mine sand and single - the importance of addressing the arsenic-containing materials dwindling gold reserves of metals and concentrates, the composition of the metallurgical complex in gold is also growing. Many of the gold deposits that are being discovered and mined in the Soviet Union, Kazakhstan, Central Asia and Siberia are classified as intractable gold ore. Due to the presence of arsenic compounds in these ores, it is not only difficult to extract gold from them, but also poses a great threat to the surrounding environment.
Some Gold - Concentrate arsenic treatment process is very complex, due to the carbonaceous substance which is present in the concentrate, and the leaching of gold fine particles was closely associated with the state and arsenic pyrite and other minerals.
For many gold-arsenic concentrates, there is still no reasonable treatment to date. Some of these concentrates can be mixed with other metal concentrates, and some concentrates are simply unavailable.
The most common method of handling gold-containing materials is cyanidation. However, when this method is used to treat gold-arsenic concentrates, the recovery rate of gold can only reach 45-80%.
Gold-arsenic concentrates can also be smelted with copper smelters or lead smelters, but the results are not ideal. The trapped magazines are distributed among various products, complicating the next-step processing technology, especially the refining operation of the main metal, increasing the cost of refining, and causing serious environmental pollution during the smelting process due to the generation of highly toxic arsenic trioxide. Pollution and deterioration of working conditions. In addition, when the gold-arsenic concentrate containing no copper or lead is treated by the fire method, since the main metal is greatly lost with the slag, it is economically uneconomical.
In foreign and Soviet production practices. When arsenic and gold are recovered from gold-arsenic concentrates, the most widely used method is oxidative roasting of sulphide concentrates, followed by cyanidation of slag or slag and copper smelters or lead smelters. Furnace - from melting.
Arsenic is mainly present in the form of arsenic pyrite in sulfide concentrates. When arsenic pyrite is oxidized, volatile arsenic trioxide and iron oxides are formed. - Part of arsenic becomes arsenate of iron, lead and other metals, and the process of entering the lower stage with the slag-burning process results in a reduction in the gold recovery rate of the cyanidation operation and contamination of the smelted product. For some gold-arsenic concentrates, arsenic in the slag cannot be completely removed even after two stages of calcination.
Generated during roasting arsenic trioxide condensed compounds difficult, especially steam coal is particularly the case for strong gas mixture Dilute. This is also the case when boiling roasting of gold-arsenic concentrates. In order to capture and eliminate the highly toxic compounds such as arsenic trioxide in the gas, it is necessary to install some special and expensive devices.
Due to the limited use of arsenic dioxide, most of the arsenic trioxide obtained during the roasting of polymetallic concentrates must be stored in a dedicated storage yard filled with concrete. The cost of storage yards such as buildings sometimes exceeds the cost of major smelting operations. Therefore, solving the problem of rational treatment of gold-arsenic concentrate is still an important economic and ecological task in modern metallurgy.
With the continuous improvement of oxidative roasting and the further recovery of gold from slag, new methods for separating gold and arsenic from sulfide raw materials, such as chlorination metallurgy, bacterial leaching, adsorption and extraction, have also been developed. Direct hydrometallurgy and so on. Vacuum high temperature separation is one of them. In this way, arsenic can be removed from the sulphide concentrate containing arsenic pyrite at the beginning of the smelting operation, making it a non-toxic volatile state.
Heating in a neutral atmosphere or in a vacuum, the arsenic pyrite is decomposed to form a vaporizable metal and a solid ladder of pyrite. In the process of heat treatment of arsenic-containing pyrite concentrate. The vacuum method not only prevents the oxidation of arsenic, but also lowers the calcination temperature (this point is especially important when processing easily sintered concentrates) and improves the condensation conditions of difficult-to-dilute steam. The main advantage of the vacuum heat treatment method for arsenic-containing ores and concentrates is that arsenic can be effectively eliminated during the -stage treatment and is independent of the original content of arsenic, which means that the method is somewhat versatile and can be obtained non-toxic. Volatile matter.
Had various Kazakhstan, Central Asia and Siberia different Gold - Concentrate arsenic (arsenic wherein 0.6 to 34%; 4 to 32% of sulfur; 11% to 35% iron; 5 to 53.7% of silica; alumina 2.4~11%; carbon 0~22%; calcium oxide 1~18.7%; copper 0~6%; gold 25~70g/ton) were tested in laboratory and expanded. The results show that the temperature is 650. ~ 700 deg.] C, pressure of the remaining gas is under 5 ~ 10mm mercury column, within 10 to 15 minutes can cause more than 95% of the arsenic from the thin volatilize or pseudo liquefied layer. The ratio of arsenic pyrite and pyrite in the original material is different. The volatiles contained 64 to 99% arsenic and 34.1% sulfur. The reason for the large change in the composition of the volatiles is that the arsenic and sulfur which are discharged during the thermal decomposition of the arsenic pyrite and pyrite interact to form sulfides in the condensate. When the pure arsenic pyrite ore and its concentrate are subjected to vacuum heat treatment, the volatile matter itself contains about 1% impurity subordinate arsenic. The obtained mixed volatiles of metal arsenic and arsenic sulfide can be easily dissolved in a neutral medium and made into a block which is easy to transport and preserve.
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