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2POSSIBILITIES OF COMPREHENSIVE PROCESSING OF MAN-MADE WASTE FROM COPPER PROCESSING PLANTS
1Abdurakhmonov S.A., 2Masidikov E.M., 3Akhtamov F.E.
1Professor of the «Metallurgical» department of Almalyk branch of Tashkent State Technical
University
2PhD student of the Department of Metallurgy of the Almalyk branch of Tashkent State
Technical University
3Associate Professor of the Department of Metallurgy, Navoi State Mining and Technological
University https://doi.org/10.5281/zenodo.13680705
Abstract. Currently in the world effective methods are being developed for processing mineral raw materials and industrial waste, completely extracting valuable components and increasing production capacity for the extraction of non-ferrous and precious metals, creating low-waste and non-waste technologies. This article presents the results of research on the development of effective methods for processing technogenic tailings with high recovery of valuable components. In addition, the results of experiments on processing waste from copper concentration factories and their granulometric, mineralogical and chemical compositions are presented. Storing this waste involves large material costs and at the same time causes some damage to the environment. It is important that the ability to separate iron minerals by the electromagnetic method has increased due to the fact that the amount of iron has increased several times after the extraction of silicon dioxide from waste from copper processing plants. Thanks to this, this type of waste serves as an additional source for the extraction of iron, gold, silver, copper and other valuable components. As a result of research, the developed technology for processing technogenic waste from a copper processing plant is effectively disposed of as a result of factors such as hermetically sealed at low temperatures, environmental safety, and energy efficiency, which makes it possible to effectively process waste from copper processing plants.
Keywords: ore, concentrate, flotation, tailings, leaching, solution, cake, crushing, grinding, physical and chemical properties.
Introduction
Today, it is important in the world to develop effective methods for processing mineral raw materials and polymetallic ores, to completely extract useful minerals from them, to increase the production capacity of rare and precious metals, to create low-waste and waste-free technologies. And also the involvement in the production of all types of man-made waste of the mining and metallurgical industry (waste from the mining industry, beneficiation plants, liquid and solid waste from hydrometallurgical and pyrometallurgical processes), the separation of silicate compounds of complex composition into individual oxides by returning the used reagents to the process, and, as a result, ensuring the extraction of useful components from the composition of man-made waste are urgent problems in this area. The technology for extracting useful components from ores is selected depending on the chemical nature of the ore being processed, in particular, copper ores are enriched mainly by the flotation method. The concentrate yield is 3-4 percent. 96-97% of the mined ore is considered waste (hosts) and is sent to the tailings dump. Currently, as a result of long-term processing of ores, the average amount of copper in two tailings dumps of Almalyk
Mining and Metallurgical Plant is 0.11%, 1459.5 million tons of man-made waste have accumulated. The total reserves of precious metals have been calculated taking into account the waste accumulated in the tailings dumps over many years, the results are presented in Table 1.
Table 1
The amount of waste and metals in them accumulated up to 2024
Tailings storage facility № Amount of accumulated waste, thousand tons. Number of metals
Copper Gold Silver
% Thousan d tons y/t t y/t T
1 573000 0,112 641,7 0,29 166,17 3,06 1753,38
2 886500 0,104 921,96 0,31 274,81 2,94 2606,31
Total 1 459 500 0,11 1563,66 0,3 440,98 3 4359,69
Table 2 presents the results of chemical analysis of samples accumulated over many years. From the data provided it follows that the obtained samples are characterized by a typical aluminosilicate: 67.31% SiO2 and 13.26% AhO3.
Table 2
Complete chemical composition of samples of man-made waste
Oxides and elements Compound, % Oxides and elements Compound, %
SiO2 67,3 Sso3 0,41
Fegeneral 8,69 SO2 0,90
Fe2O3 8,83 P2O5 0,17
FeO 3,23 ±H2O 0,49
TiO2 0,36 Cu 0,11
MnO 0,08 Pb 0,018
A12O3 11,57 Zn 0,026
CaO 1,30 As 0,0028
MgO 1,97 Sb -
K2O 4,27 Mo 0,0030
Na2O 0,44 Au, y/t 0,3
Sgeneral 2,77 Ag, г/т 3,0
S 2,36 Others 0,34
The sample taken from the waste of Almalyk KMK MBF has a sulfide content of 2.36%. The fractional composition of the waste and the distribution of metals by size fractions were also studied, the results are presented in Table 3.
Table 3 shows that a large proportion of precious metals (more than 80%) falls on the +0.1 fraction, which is explained by the fact that the elements contained in large quartz minerals remain in the tailings of flotation enrichment of copper ores.
Aluminum and silicon oxides make up the bulk of the waste from copper processing plants and are contained as follows: 67.31% SiO2 and 11.57% AhO3. If, during waste processing, the main attention is paid to the separation of FeO, SiO2 and AhO3, the amount of valuable metals in dealumosilicate waste will increase several times. This creates the possibility of complex waste processing without waste.
Table 3
Fractional composition of copper processing plant waste and distribution of metals in it
Size class, mm Fraction output Cupper Gold Silver
Content, % Mass, g Distribu tion, % content, g/t Mass, g Distributi on,% Conten t, г/т Mass, g Distribut ion, %
g %
+ 0,59 108 5,4 0,127 0,137 6,22 0,36 0,000039 6,5 3,62 0,00039 0,65
-0,59+0,3 648,8 32,44 0,112 0,726 33,0 0,34 0,00022 36,66 3,42 0,0222 37,0
-0,3+0,21 514 25,7 0,111 0,570 25,9 0,31 0,000159 26,5 3,28 0,0168 28,0
-0,21+0,15 274 13,70 0,109 0,298 13,58 0,30 0,000082 13,6 3,17 0,00868 14,46
-0,15+0,10 84,8 4,24 0,108 0,091 4,13 0,29 0,000024 4,0 2,95 0,0025 4,16
-0,10 +0,074 77,2 3,86 0,106 0,081 3,68 0,27 0,000021 3,5 2,86 0,0022 3,66
-0,074 +0,044 149,6 7,48 0,102 0,152 6,9 0,24 0,000036 6,0 2,75 0,00411 6,85
-0,044 143,6 7,18 0,101 0,145 6,59 0,13 0,000019 3,24 2,17 0,00312 5,1
Всего: 2000 100 0,11 2,2 100 0,3 0,0006 100 3,0 0,06 100
Based on this, the technology for processing technogenic waste using ammonium halides (NH4F) was chosen. The following reaction mainly occurs.
SiO2+ 6NH4F = (NH4)2SiF6 + 4NH3 + 2H2O (1) Ammonium hexafluorosilicate obtained by reaction 1 has technologically advantageous physicochemical properties. This substance is solid under normal conditions, and at temperatures above 320 °C it sublimates and passes into the gas phase. Another advantage of using ammonium fluoride as a desilication reagent is the possibility of its regeneration. At a temperature of 70 °C, the solubility of ammonium hexafluorosilicate reaches 370 g/l. HFSA (ammonium hexafluorosilicate) reacts with ammonia, causing the precipitation of SiO2.
(NH4)2SiF6 + 4NH4OH = SiO2 + 6NH4F + 2H2O (2) The possibility of ammonium fluoride regeneration ensures a continuous cycle of desilication and quartz extraction from waste in the form of SiO2 with small particles. After filtering silicon oxide from the solution, ammonium fluoride remains in the solution, and after evaporative crystallization it is returned to the waste desilication process. In order to extract useful components from the composition of technogenic waste of copper processing plants, it is first necessary to extract silicon oxide and iron oxides. For this purpose, a technological process for desilication of waste enrichment residues using ammonium halides (NH4F or NH4F-HF) was developed. Fig. 1 shows the cycle of desilication of technogenic waste using ammonium fluoride.
Figure 1. Scheme of the desilication cycle of industrial waste using ammonium fluoride
In order to determine the optimal parameters of sublimation roasting of copper processing plant waste, the dependence of various factors on the release of SiO2 into an amorphous product was studied. First, the dependence of the sublimation roasting temperature on the degree of SiO2 extraction was studied. Experiments were carried out in the temperature range from 100 °C to 500 °C for 1 hour. The constructed diagram of dependencies based on the results of the study is shown in Fig. 2.
Figure 2. Graph of the dependence of the degree of SiO2 extraction from copper processing
plant waste on the sublimation temperature
As can be seen from the diagram in Fig. 2, with an increase in the temperature of sublimation roasting of copper processing plant waste for 1 hour, the degree of SiO2 extraction increases and reaches a high value of 75% at 450 °C, further increase in temperature does not lead to a significant increase in the degree of SiO2 extraction. Based on this, the optimal temperature of sublimation roasting can be taken as 450 °C. Also, at the optimal temperature of 450 °C, the dependence of the degree of SiO2 extraction on the time of sublimation roasting was studied. The experiments were carried out in the time interval from 0.5 to 3 hours. The constructed diagram of dependencies based on the results of the study is shown in Fig. 3.
0 30 60 90 120 150 180
Firing rime, miti.
WWAV/A•vviiv WfiWWVW VvVvVvVW
Figure 3. Graph of the dependence of the degree of SiO2 extraction from copper processing plant waste on the duration of sublimation roasting at optimal temperatures
As can be seen from the diagram in Fig. 3, the degree of SiO2 extraction increases with the increase in the roasting time of copper processing plant waste at a temperature of 450 °C and reaches a high value of 99.77% in 120 minutes; further prolongation of the roasting time does not lead to an increase in SiO2 extraction. Based on this, the optimal duration of sublimation roasting can be considered 2 hours. To isolate SiO2 from the HFSA composition obtained as a result of sublimation roasting, it was treated with ammonia water (NH4OH). Experiments were carried out with 2, 4, 6, 8, 10 and 12% NH4OH solutions. As a result of the studies, it was found that the optimal concentration of NH4OH for the extraction of SiO2 from the HFSA composition is a 10% solution. One of the advantages of isolating SiO2 from the HFSA composition with ammonia water is the possibility of obtaining NH4OH required for the process by absorbing ammonia gases formed during sublimation roasting of copper processing plant waste using NH4F.
CONCLUSION
Thus, NH4F obtained by evaporative crystallization after the release of SiO2 is returned to sublimation roasting. This allows the desilication process to be carried out continuously and to extract finely dispersed silicon oxide from waste in the form of a white powder with a purity of 99.9.
Due to the fact that the main part of copper processing plant waste is silicon oxide (67.31% SiO2), if the main attention is paid to the release of SiO2, the ammount of precious metals in desilicate waste will increase several times and it becomes possible to effectively extract non-ferrous and precious metals.
In order to remove SiO2 from copper processing plant waste, the following optimal parameters of sublimation roasting with the addition of NH4F were determined: sublimation roasting temperature - 450°C, roasting time - 2 hours, optimal concentration of NH4OH during leaching of HFSA - 10%. The degree of SiO2 extraction reaches 99.77%, and SiO2 with a purity of 99.9% is obtained.
REFERENCES
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