Containing gold - arsenic sulfide concentrate roasting is performed within the boiling layer and the gold and pyrite arsenic pyrite reaches a set-up job dissociated. This method has been widely used in the production practice of foreign gold mining companies.
Studies by the Irkutsk branch of the Institute of Rare Metals in China show that it is impossible to obtain the lowest slag containing seeds and sulfur for the stage-burning of concentrates. This inevitably loses a lot of gold during the further processing.
Therefore, it is necessary to develop a method that can ensure the production of products suitable for melting in a copper smelter and the in-situ treatment of concentrates and extraction of precious metals.
Research by the National Institute of Nonferrous Metals Mining and Metallurgy and the National Institute of Rare Metals in Irkutsk has shown that two-stage roasting of concentrates that are more complex than the concentrates in the Bidarasong mine can be guaranteed to be very suitable. A cinder that is cyanidated and has a high gold recovery.
The device used in the semi-industrial test is a continuous operation two-stage boiling layer roasting device. The device comprises two successively arranged boiling furnaces. The first stage has a bottom area of ​​0.0336 m ² , the second stage roast has a bottom area of ​​0.089 m ² , a dry dust collector, an electric precipitator, an arsenic crystal chamber, and a bag. A wet scrubber for the dust collector and static gas (see Figure 1). The processing capacity of the device is 250~300 kg of concentrate per day and night.

In the first stage of calcination, As is sublimated in the second stage of calcination in a low calcination temperature and a weak acid atmosphere, sulfur is completely eliminated in the case where the high temperature and the remaining air are 1 to 2 times more than the theoretical requirement.
It can be seen from Fig. 2 that the sublimation rate of arsenic is the highest when the air excess ratio is equal to 0.75-1.0. At this time, the free oxygen in the gas does not exceed 2%. The desulfurization rate is 57 to 60%.

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As the amount of remaining air increases, the sublimation rate of arsenic decreases, and the desulfurization effect is also improved. When the air consumption is 0.75 lower than the theoretical requirement, the arsenic content in the slag is high.
When the calcination temperature is between 550 and 650 ° C, the sublimation rate of arsenic is the largest (see Figure 3). When the temperature is lower than 550 ° C, a large amount of unoxidized arsenopyrite remains in the slag.

As can be seen from the data in Figure 4, the calcination temperature has a definite effect on sulfur removal, and the decisive factor is the air consumption (see Figures 3 and 4).
The increase in arsenic content in the slag (see Figure 4) demonstrates that arsenic is not sublimated in the second stage of calcination, and the arsenic concentration in the slag is increased.

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The relationship between the quality of the slag and the rate of loading the concentrate into the roaster is shown in Figure 5. As seen from Fig. 5, the unit processing capacity in the first baking furnace is 7.0 to 9.5 tons/m2, day and night, and the second roaster is 3.5 to 4.7 tons/m2. The results obtained during day and night are better.
The following process regimes were identified during the semi-industrial test:

Paragraph I, paragraph II, boiling layer temperature °C 550~600 650~675
The excess coefficient of air, a 0.75~1.0 1.5~2.0
Gas flow rate in the boiling layer, cm / sec 0.1~0012 0.10
Day and night processing capacity, tons / square meter, 7.0 ~ 9.5 3.5 ~ 4.75
Under this process condition, the slag containing As 0.19~0.6% and S 0.9~l.3% was obtained.

According to the above process conditions, eight day and night balance tests were carried out on the continuous operation of the roasting apparatus (see table).

Metal balance calculations show that the error of the balanced metal is within the tolerances allowed in the chemical analysis process. A large amount of gold (79.8%) is enriched in the calcine, while the remaining gold remains in the soot of the dust collection equipment. Gold is not lost with gas.
The soot in the crystallization tank and the bag filter is characterized by a high arsenic content (about 63 to 49%) and requires special handling.
About 16% of the Au is transferred to the dust of the dry scrubber and the electrostatic precipitator. These soots are almost identical in terms of their chemical composition. Analysis of the forms of arsenic in these soots indicates that approximately 92% of the arsenic is arsenic trioxide.
According to previous tests, the possibility of simultaneously treating the soot in the precipitator and the electrostatic precipitator with the pre-granulated raw material was verified.
The above-mentioned soot was placed in a disc granulator having a diameter of 500 mm to form pellets. The rotation speed of the disc is 14-16 rpm, and the inclination angle is 52-55°. Only water is needed for granulation, and it is not necessary to add a binder. The particle size selected according to the conditions which can ensure the liquid layer of the material in the furnace is 100% - 5 + 1.0 mm. The coarse particles have a moisture content of 10 to 12% and a strength of -1.1 to 1.5 kg/particle. The proportion of the dust in the dust collector and the electrostatic precipitator should be determined according to the weight of various soot produced during the roasting process. The mixed soot is then sent to a granulator for granulation.
Both the roasting of concentrates and the return of soot are based on previously established systems. The average unit processing capacity of the first stage of roasting is 9 tons per square meter per day and night. Before the material balance is established, the amount of the returned soot mixture should be 19.5% of the concentrate weight, which is the value of the calcining unit's reduced ability to treat the original concentrate. The roasting work is characterized by stable temperature and air conditions; the quality of the slag is very good. The soot obtained in the second time is relatively poor in gold, about 5 to 3%. The yield of the slag is increased to 59-62% of the concentrate weight.
The results of the semi-industrial test show that the entire dust removal system including the dust collector, electrostatic precipitator, crystallization tank and bag filter can ensure the dust removal rate of the gas reaches 99.9% (see Figure 6). [next]

In the two-stage roasting method Dala Song beneficiation plant is not only practiced by: improved technology offers the possibility of economic indicators, but it is also possible to achieve local output of precious metals.

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