Patent EP-3363918-A1 (EP)
Inventor: CÁRDENAS ARBIETO FRANCISCO JAVIER
IPC: C22B5/02
Filed: 2016-08-15
Abstract: The invention entitled "Method for extracting metals prom concentrated sulphurated minerals containing metals by direct reduction with regeneration and recycling of the reducing agent, iron, and of the flux, sodium carbonate" is presented as an alternative to conventional processes for extracting ferrous and non-ferrous metals from sulphurated minerals containing them, applying the improved direct reduction process, i.e. without sulphur dioxide emissions and without producing the slag generated by conventional metallurgy, thus minimizing environmental pollution. In addition, operating costs of the metallurgical process are substantially reduced by regenerating and recycling the reducing agent, iron, and the flux, sodium carbonate.  Nowadays, the extraction of metals from mining activity is carried out by conventional and modern processes. On the one hand, we find conventional pyrometallurgical processes, which involve the previous toasting of the mineral before extracting metals in furnaces, and on the other hand, combined pyro, hydro and electrometallurgical processes, in which sulphurated minerals are toasted first, and the dissolved metal to be extracted is then leached and electro-deposited. These processes are highly polluting, though. With respect to modern processes, we find biometallurgy, which uses bacteria for the extraction of metal, with the disadvantage of being slow processes. On the other hand, hydrometallurgy is also used at high pressure, which involves high investment and operating costs.  The new metallurgical process consists of: 
- Extraction of metals in the smelting furnace using iron as a reducing agent and sodium carbonate as a flux 
- Selective dissolution in water of sodium sulphide from slag and filtering of waste, ferrous oxide 
- Regeneration of sodium carbonate for recycling 
- Removal of hydrogen sulphide gas and obtaining elemental sulphur 
- Sintering of ferrous oxide agglomerates for subsequent reduction of iron metal 
- Generation of reducing gases, carbon monoxide and hydrogen 
- Regeneration of metal iron for recycling from ferrous oxide  The proposed technological innovation combines novel pyrometallurgical and hydrometallurgical processes, different from conventional ones, which do not require a prior toasting of the sulphurated mineral concentrate, and are technically and economically more advantageous than the currently used processes because it reduces to zero the positive oxidation state of the metal directly, using a single reactor for the extraction of metal. It regenerates and recycles metallurgical inputs with complementary processes, with a high speed in the kinetics of chemical reactions and, all this, without generating slag or polluting gases. As a result, the extraction of metals is achieved at a low operating cost, in an environmentally sustainable manner, thus avoiding high costs for environmental remediation.  It is important to point out that the proposed invention can also be applied to the treatment of tailings and environmental liabilities, solving a problem that has been accumulating for years due to mining activity that is not very environmentally responsible and which, until now, has not been possible to remedy due to the high costs involved.  Consequently, by applying this process, the economic viability of mining projects is increased, even under a scenario of lower metal prices. The process involved allows mining companies to obtain lower cut-offs and cash costs for their extractive activity and, in turn, allows them to generate higher revenues from the export of metals, rather than the export of mineral concentrates. In addition, as it is a clean and environmentally friendly technology, it allows mine closure costs to be radically reduced. As a result, this process provides a higher level of profitability and sustainability of mining activity.  On the other hand, with a gradual implementation of the proposed process in mining activity, the Government will benefit thanks to the increase in the Trade Balance, resulting from increased exports, and to the higher tax revenue that will be generated by higher business income. This, in turn, positively affects regional and local governments for the higher revenues that will be generated from mining royalties. Increased mining activity will imply greater sources of direct and indirect employment generation, as well as boosting other sectors of the economy, such as the steel, metalworking and construction industries. Added to this are the lower costs of remediation of environmental liabilities. In short, it has the potential to generate higher incomes for the Government, and thus greater socio-economic well-being for the population.  The advantages of this technological innovation in the environmental field range from the regeneration and recycling of inputs, and the elimination of slag and polluting gases from the extractive process, to the remediation of tailings from current mining activity as well as existing environmental liabilities, resulting in less pollution of rivers, agricultural fields and less impact on natural reserves. In other words, it significantly reduces the environmental footprint of mining activity.  Finally, and as a consequence of the aforementioned, this invention manages to improve health standards in the population adjacent to the mines by reducing emissions and toxic waste, as well as by eliminating risks derived from the potential rupture of dams in tailings. Similarly, mining activity, by ceasing to interfere with the population's agricultural, fishing and livestock activities, reduces the possible emergence of social conflicts, thus allowing the viability of mining projects to increase, which in turn translates into greater social works and an increase in the income of the surrounding population. In conclusion, this innovative process for the extraction of metals has the capacity to generate harmony between mining activity, the environment and the population.