The optimum process conditions for two-stage roasting of concentrates are as follows:
                                                                                Stage 1 roasting        Stage II roasting
Unit processing capacity, tons / meter 2 · day and night                     6.0~6.5                     2.5~5.0
Calcination temperature, °C;
Within the layer                           500~550                   650~670
       Under the layer                                                         450~470           Not less than 560
Air excess coefficient                                                 0.5               1.5~1.8
Line speed of air in airflow, m / s                           0.1                             0.1
A lower degree of vacuum of the roof, mm mercury column      2~3             2~3
To be sure, the calcine is carried out at a muddy concentrate - the only step cyanide - when favorable baking products. The dust in the precipitator and the electric precipitator contains a lot of activated carbon during the roasting process. After granulation it should advance to paragraph 1 returns the firing furnace and fired again.
The research results prove that when the baking temperature exceeds
The maximum allowable content of carbon in the cyanide-raised calcine should not exceed 0.3% . The results of the study prove that the limit content of carbon in the calcine is 0.2% .
It is equally certain, calcine dust and there - is not part of the complete oxidation of arsenic is the cause of pyrite (FIG. 9) of gold cyanide substantial loss of time. The two worked muddy gold concentrate roasting developed - a optimum conditions, resulting in improved gold recovery and ensure access to qualified arsenic trioxide.
References cited data from laboratory and semi-industrial tests for two-stage boiling roasting of argillaceous gold-arsenic concentrates directly from the slurry. The main process parameters for the two methods of drying and boiling roasting of refractory gold-containing concentrates in the slurry were determined. This - feature of the process is the device structure is simple, durable and stable operation of the roaster is easy to realize comprehensive automation.
It must be pointed out that there is very little information on this aspect of the major gold producing countries in the world. In recent years, there have been few reports on the practice of deduction treatment of all gold-containing materials, especially for difficult-to-select gold-containing materials.
After analyzing and summarizing the existing data in the literature for laboratory, semi-industrial, industrial test and industrial applications of boiling roasting refractory gold-containing materials, it can be seen that the refractory gold-containing materials are subjected to boiling roasting before cyanidation. The method will be more widely used. But this method, whether it is the Soviet Union or in foreign countries, is still not the main method of gold mining companies. Bed-type roasters are still used in many countries, such as Canada, Australia, South Africa, Ghana, and the United States. There are about 50 such devices in Australia alone , which can be fired every day and night - more than a thousand tons of refractory gold-containing materials.
Since the boiling roasting method has many advantages, why is the speed of promotion so slow ? And what is the vitality of the bed roasting method ? The reason is that most gold mining companies are small in scale and have little processing ore. The cost of roasting - ton of gold-containing materials in these companies is 50 to 90 cents, and in some cases 20 to 25 cents. However, the cost of treating the same material using boiling roasting is a few dollars. For example, the US boiling plant's boiling roaster has a processing capacity of 40 tons / day and night, and the cost of processing - ton gold concentrate is $ 3.9 .
Despite this, the bed type roasting method has its disadvantages, for example, the calcining furnace has a low processing ability, the surface temperature distribution of the calcined material is uneven, and the furnace temperature and gas conditions are difficult to control. Therefore, the boiling roasting method should be promoted continuously in gold enterprises.
Especially after the merger of many small businesses and the need to expand the processing capacity and scale of the company, it is necessary to replace the bed roasting method with boiling boiling. In this case, a large number of small bed type roasting apparatuses are not suitable.
In recent years, in the Soviet Union and abroad, it has been studied to carry out chlorination of gold-containing materials in a boiling roaster. According to the reference, this method can more comprehensively recover various useful components.
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