Development and Implementation of Innovative Technologies That Ensure an Increase in The Extraction of Non-ferrous, Noble, Rare, Rare- Earth Metals

Received Dec 03, 2021 Revised Jan 25, 2022 Accepted Jan 30, 2022 The article presents the most innovative technologies developed by Satbayev University, "Institute of Metallurgy and Ore Beneficiation" JSC (Republic of Kazakhstan, Almaty) in recent years. The implementation of these works on an industrial scale will lead to significant economic and environmental effects. The following technologies are described: synthesis of a new foaming agent for intensification of flotation enrichment of gold-bearing ores; multicomponent microflotation, which allows to increase the extraction of valuable metals at existing deposits and to develop new, relatively poor and previously economically unpromising deposits; flotation enrichment of persistent goldcontaining ore; contractile pyrometallurgical selection, which allows direct melting of persistent gold-containing raw materials with the transfer to the gas phase of arsenic, sulfur and other volatile components, followed by their neutralization and concentration of gold, silver and other non-ferrous metals in matte melt; continuous conversion of copper matte in the Vanyukov furnace; processing of liquid metallurgical slags in a furnace with an electrically heated coke filter; vacuum distillation refining of rough selenium; extraction of rare earth metals from extraction phosphoric acid obtained during the processing of phosphorites; processing of high-grade low-quality bauxite. New technical solutions have been developed in the field of mineral and man-made raw materials enrichment, metallurgy of non-ferrous, noble, rare and rare earth metals, which have high economic efficiency and the feasibility of their introduction into production. The novelty of the presented works is confirmed by the security documents of the Republic of Kazakhstan.


INTRODUCTION
The Republic of Kazakhstan is rich in natural resources. Almost all the elements of the Periodic Table  are in its depths, most of them in industrial quantities: copper, aluminum, lead, zinc, cadmium, chromium, molybdenum, rhenium, selenium, tellurium, gold and other non-ferrous and rare metals [1]. As a result, at present, metallurgy forms the basis of the Republic's industrial power and its export potential [2]. Involvement in the processing of refractory, complex in composition mineral and technogenic raw materials is an urgent problem for the metallurgical industry around the world. Industrial development of such raw materials in Kazakhstan is limited due to the lack of efficient and cost-effective technologies. At present, the most important problem of the metallurgical industry is the development and implementation of innovative technologies enabling to extract with maximum completeness non-ferrous, rare and rare-earth metals contained in ores, industrial waste and secondary raw materials [3].
In recent years, the Institute has developed innovative and modernized existing technologies for the extraction of non-ferrous, noble, rare and rare-earth metals from mineral, technogenic and secondary raw materials, ensuring an increase in the extraction of non-ferrous, noble, rare, rare-earth metals that are implemented at the production facilities of industrial enterprises of the metallurgical complex of the Republic. Kazakhstan. These works are aimed to increase production parameters and improve the environmental parameters of non-ferrous metallurgy enterprises in general [4].
The use of continuous converting eliminates the periodicity of the blister copper production process, enables to use oxygen-enriched blast, to obtain a stable flow of sour gas of constant composition, to reduce sulfur dioxide emissions to the atmosphere to a minimum, to increase the degree of sulfur utilization that contributes to an improvement in the environmental situation. It is recommended for use in non-ferrous metallurgy enterprises with a copper matte conversion process [17]. Figure 2 shows a diagram of a two-zone Vanyukov furnace (melting in a liquid bath). Main parameters of the two-zone PV furnace: -matte consumption, t / h -69-96; -coal consumption, t / h -0.5-2.5; -flux consumption, t / h -1.0-7.5; -oxygen consumption, nm 3 / h -12000-24000; -air consumption, nm 3 / h -3000-10000; -specific oxygen consumption, nm 3 / t -160-295; -temperature in the reduction zone, ° С -1280-1300; -matte temperature, °С -1125-1250; -outlet gas temperature, °С -320-565; -bath height, mm -2250-2400; -width of the recovery zone, mm -2200; -length of the recovery zone, mm -6000; -Cu content in matte,% -43.5-63.6; -Cu content in slag,% -0.4-0.8; -SiO2 content in slag,% -30.0-32.8. The existing methods of depletion of non-ferrous metallurgy slags do not provide a sufficiently complete extraction of metals from slags. The processing technology for liquid metallurgical slag in a furnace with an electrically heated coke oven filter enables to obtain a metallized phase that concentrates iron, copper and precious metals; fumes containing lead and zinc; slags completely dumping for non-ferrous metals, suitable for the production of building materials [18]. Figure 3 shows a diagram of a combined unit, including a Vanyukov smelting furnace and a coke filter for slag processing% -0.4-0.8; -SiO2 content in slag, % -30.0-32.8.
The heating of the coke filter is performed in the most economical way in an electric furnace with electric energy that enables to significantly reduce the consumption of scarce coke used in this case as a reagent, and to obtain a minimum amount of waste gases with a significant reduction in the cost of cleaning them. The copper extraction into an iron-copper alloy was 91.9%, iron about 70%, and lead and zinc into sublimates -94 and 88%, respectively. Average coke consumption is 5-7% of the processed slag mass. The average specific power consumption is 250 kWh/t of liquid slag. It is recommended for use in non-ferrous metallurgy enterprises. When autogenous technologies are used to smelt sulphide raw materials, slags are formed that require separate processing for additional recovery of non-ferrous metals [19]. The main principles of the continuous smelting process for copper sulphide concentrates with reduction finishing of slags in the tail zone of the PV furnace (Vanyukov melting furnace) have been developed to obtain slags with a minimum copper content of 0.5-0.7% [20]. Slag reduction is performed by adding a carbon-containing reductant (coal, coke, shungite, etc.) to the reduction zone of the furnace. This technology enables to use the tail end of the PV furnace to reduce slag processing by installing a baffle dividing the furnace into an oxidizing smelting zone and a reduction zone, where magnetite and partially zinc and lead are reduced enablig to obtain slags poor in copper and lead-zinc sublimates. Basic parameters of continuous matte conversion furnace: -matte output, t/h -55-65; -copper content in matte, % -55-60; -matte humidity, max, % -6; -dimensions of melting zone in tuyeres area: length, width -9 x 2, area, m 2 -18; -height of tuyeres installation from bed in melting zone, mm -1600; -number of tuyeres in melting zone, pcs. -Quantity of oxygen-containing blast for one lance, nm 3 /h -1000; -Blast volume per 1 t of matte, nm 3 /h -220. It is recommended for use in non-ferrous metallurgy enterprises. Recommended for use in non-ferrous metallurgy enterprises.     Copper electrolyte production slimes containing selenium are formed in the process to obtain copper. We have developed technologies to extract elemental selenium from this middling product with subsequent refining by vacuum distillation [21,22]. An industrial prototype of a vacuum distillation unit was made, with a capacity of up to 2.0 tons of refined selenium per month, where large-scale tests of the technology were performed [23]. Table 2 shows the material balance of the distribution of selenium by the products of vacuum distillation processing of crude selenium obtained as a result of processing copper electrolyte sludge in the Kaldo furnace.
X-ray fluorescence analysis in ingots of refined selenium determined the following content of elements, wt. %: 99.543 -Se; 0.217 -O; 0.003 -S; 0.003 -Pb; 0.021 -Mg; 0.007 -Ni;0.005 -Al; 0.122 -Te; 0.005 -Cl; 0.003 -Si; 0.031 -Sb; 0.033 -Cr; 0.002 -Cu; 0.005 -Fe. The output of refined selenium was 96.07%. Selenium was converted to raffinate by 98.96%. Selenium was not found in the bulk residue from the distillation, while the silver content was 2.05 wt. %. The increased iron content in bauxite rsults in serious sintering problems. Therefore, it is required to preliminarily separate ferruginous compounds as much as possible -iron sands from the bauxite bulk. The processing of ferruginous sands is an important practical task the solution of which will increase the profitability of the existing alumina production. The technology developed for processing ferruginous sands includes the production of cast iron, concentrates of rare metals, rare earth elements, red and black pigments and titanium dioxide [24,25]. The Process flow for the processing of ferruginous sands of alumina production is shown in Figure 5. Concentrates of rare metals -gallium and vanadium of the composition, wt. %: 30.0 Al2O3, 0.32 Ga2O3 and 4.85 V2O5 -were obtained from the aluminate leaching solution. As a result of the reduction melting of the ferrous sand leaching cake at a temperature of 1450°C, cast iron and unmetallic slag were obtained. The iron yield in cast iron was 99.4%. A concentrate containing 20.74% of REE and titanium dioxide with a content of 61.8% TiO2 was obtained from unmetallic cast iron slag. As a result of the research, the Technological Regulations for the integrated processing of ferruginous sands of alumina production and a preliminary business plan were developed. The importance to solve the problem of use of the products of chromium ore dressing in waste processing is associated not only with the environment but also with the need to increase the chromium production. The enterprise engaged in the extraction and beneficiation of chromium raw materials in Kazakhstan is Donskoy MPP. During the operation of the concentrating factories, the plant has stockpiled about 15 million tons of sludge tailings, the loss of Cr2O3 by the beneficiation technology is up to 25.5%. The known methods of utilization of ferrochrome production middlings and waste products do not enable to extract accompanying valuable components -rare metals and rare earth elements -along the way [26]. A technological scheme has been developed, shown in Figure 6, for the complex processing of chromium waste, including leaching in a solution of ammonium hydrosulfate, to obtain a concentrate of rare metals gallium and vanadium, a concentrate of rare earth elements with a content of 21.58 % and a chromium concentrate with a Cr2O3 content of 59.1 % [27]. High technological indicators of the technology for obtaining concentrate of rare metals, gallium and vanadium from wet gas purification sludge of ferrochrome production are confirmed by experimental tests. The following rare metal concentrate composition, wt. % was obtained: 30 [28]. A technology has been developed for the extraction of rare earth metals from extraction phosphoric acid obtained by processing phosphorites [28,29].
Technological modes of desorption for rare-earth metals from a cation exchanger to obtain a concentrate of rare-earth metals have been worked out. Various desorbing solutions have been tested: ammonium chloride; ammonium sulfate; a mixture of nitric acid with ammonium nitrate; a mixture of hydrochloric acid with 8 ammonium chloride; a mixture of sulfuric acid with ammonium sulfate. The optimal conditions for the desorption of REM from the Purosorb 140 cation exchanger have been determined: the precipitation parameters of REM salts have been determined and a conditioned 92.22% REM concentrate has been obtained. Table 3 shows a material balance of REM extraction from phosphoric acid extraction.
Experimental tests of the developed technology of REM extraction from unpaired dihydrate EPA resulted in determination of sorption and desorption parameters, modes of selective precipitation of iron and REM. Oxide concentrate with REM content of 97% was obtained [30,31]. When bauxites are processed in Kazakhstan, along with alumina, only gallium is extracted in an amount of 7-8% of the input. Other rare metals that make up their composition are of industrial interest but their behavior in the processes of alumina production has been insufficiently studied [32].
On the basis of existing alumina production operation studies for processing high-ferrous bauxites of Aluminum of Kazakhstan JSC, intermediate products containing rare metals -recycled soda, ferrous sands and red mud were selected and a technological scheme for their joint processing was developed to obtain a collective concentrate with a content of 0.4% Ga and 14.31% V2O5. Vanadium pentoxide was obtained with a content V2O5 99,1 % with the help of ammonia technology. An electrolysis method on a rotating galvanized cathode has been developed to obtain metallic gallium. The extraction during electrolysis was 95.9% with an electric power consumption of 87.7 kWh/kg gallium. A gradual decrease in the high-quality bauxite production, high operating costs and energy intensity of the methods used for the extraction and processing of raw materials, in combination with their environmentally unfavorable impact, are, in aggregate, an objective basis to use low-quality aluminum-containing raw materials in the production [33]. Alumina production in the Republic of Kazakhstan with the help of Bayer-sintering technology becomes less profitable and competitive and requires serious modernization. The developed Bayer-hydro-garnet technology enables to solve the problem of high-iron low-quality bauxite processing with minimization of alkali and alumina losses, reduction of electricity consumption and material costs [34,35,36]. The technological scheme of the Bayer-Hydrogranate technology is shown in Figure  7.  The technology includes the red mud processing from the Bayer branch using the hydro-garnet technology and the conversion of aluminate solutions to obtain aluminum hydroxide. The use of hydro-garnet processing made it possible to extract an additional 10.23% of alumina. The technology includes the processing of red mud of the Bayer branch using the hydro-garnet technology and the conversion of aluminate solutions to obtain aluminum hydroxide. The use of hydro-garnet processing made it possible to extract an additional 10.23% of alumina. The possibility of obtaining pig iron from hydro-garnet sludge by means of reduction melting at a temperature of 1650 °C has been determined. The pig iron yield was 39.5% of the weight of the initial charge [37].

CONCLUSION
Thus, the technologies presented in the work have passed laboratory and pilot tests, some of them have been tested on a pilot scale. The conducted studies correspond to the level of research conducted in the world in the field of metallurgy and many, due to the specificity of Kazakhstan raw materials, are original. Thus, for the first time, the main design parameters of the two-zone Vanyukov furnace were determined, the technology of selenium extraction from industrial products of refining production was developed, effective modified flotation reagents were proposed to increase the extraction of copper and molybdenum into coppermolybdenum concentrate. It is shown that the use of an oxidizer (a mixture of calcium hypochlorite and trichloroisocyanuric acid) helps to increase the extraction of gold. Unique technologies have been developed for processing ferrous sands of alumina production to produce cast iron, concentrates of rare metals, rare earth elements and titanium dioxide and to obtain gallium and vanadium concentrate from the tailings of chromite ore enrichment. The parameters of desorption of rare earth metals from Purosorb 140 ionite saturated with REM from extraction phosphoric acid were determined. A unique Bayer-hydrogranate technology for processing high-iron bauxite has been developed and a pilot plant with a capacity of 50 kg/hour for alumina, which has no analogues in the world, has been created.