Periodic Reporting for period 3 - METGROW PLUS (Metal Recovery from Low Grade Ores and Wastes Plus)
Reporting period: 2019-02-01 to 2020-01-31
The primary objective of METGROW+ was to create, demonstrate and validate an industrially viable and flexible New Metallurgical Systems Toolbox, which allows to smartly combine pyro-, hydro-, electro-, bio-, solvo- and ionometallurgical unit operations, as well as residual matrix valorisation technologies, to valorise EU’s low-grade, polymetallic primary and secondary resources. The toolbox allows producing innovative, systems based, metallurgical solutions to recover metals and to valorise the residual matrix, while minimising energy consumption and the overall environmental footprint.
The created toolbox consists of a broad range of already existing and newly developed metallurgical unit operations. The unit operations follow a value-chain approach, from pre-treatment, to metal extraction, metal recovery and (residual) matrix valorisation in building materials.
The novelty of METGROW+ was twofold:
(1) The systems approach (toolbox) to couple the individual unit operations to obtain the most cost-effective and environmentally friendly flow sheet for a given low-grade resource.
(2) The development of several new metallurgical unit operations (incl. bio-, solvo- and plasma operations). METGROW+ demonstrated and validated the New Metallurgical Systems Toolbox for a multitude of low-grade resources in the EU-28.
The objective of high leaching yields (>90 %) was achieved for laterites (Ni, Co, Mg: atmospheric acid leaching; Ni: solvometallurgy), jarosite (Zn, Pb, Ag: roasting and two-stage leaching; Ge: autotrophic bioleaching; Zn: DES), Cr-rich sludge (Cr and Ni: heterotrophic bioleaching) and landfilled Zn-rich sludges (Zn: heap leaching, DES and solvometallurgy). Plasma-pyro technology performed well with all studied materials. To develop economically and environmentally viable processes, selectivity and flexibility were studied reaching the METGROW+ beyond the state-of-the-art for majority of the sample materials.
Results from physico-chemical metal recovery experiments showed that the proposed processes were valid for the clean-up of the pregnant leach solution (PLS) and for the recovery of metals. The target selectivity of >85% combined with a recovery yield of >90% was achieved for Ni and Co in Greek laterites PLS, for Zn in Zn-rich sludge PLS and for Zn and Pb in jarosite PLS. Combinations of different metal recovery methods showed promising results.
The reactivity of leach residues for the residue valorisation showed clear potential for the use of certain residues as supplementary cementitious materials (SCM) and the production of alkali activated inorganic polymers (AAIP), which may be used as binders in the construction sector or construction materials with various beneficial properties. In some cases, the reactivity increased by mixing two different residues.
Validations were completed for Greek laterites using acid leaching and chemical precipitation or heap leaching, for Polish laterites using acid leaching and solvent extraction, for Cr-rich sludges using heap leaching, and for goethite and fayalitic slag using plasma-pyro technology. Zn-rich sludges were validated through modelling. All validations showed technically promising results.
Various assessments (e.g. LCA, TEA, sensitivity, risks) were done for complete process flow sheets for all material streams with most promising technologies. Processes Building Information Modelling (BIM) and digital twin methodology were used as METGROW+ visualization tools for atmospheric leaching of Polish saprolitic laterite and for plasma-pyro treatment of Zn-rich sludge. The approach included the physical layout over the terrain and the process equipment layout including mechanical, electrical and piping connections.
The main outcome of the project, the free public version of the METGROW+ toolbox (https://app.metgrowplus.eu) was developed. The toolbox aids in process selection decision making.
The METGROW+ toolbox boosts the European mineral extractive and processing industry, since it triggers the cost-effective exploitation of Europe’s domestic low-grade primary and secondary resources. The toolbox provides a feasible, sustainable, cost-effective set of processes, ranging from upstream activities to downstream activities including wastewater treatment with biosorption and biological sulfate reduction. In addition to the direct impact in metal exploitation and production rates, the use of the METGROW+ toolbox has a cross-sectorial impact in the metal-related European industry, since it produces a set of process steps that cover the value chain. Since the toolbox addresses technological, environmental, economic and social assessment, different levels of the European scenario can benefit from the information provided by the tool: public bodies can retrieve information for policy making and about social impact (policy level), companies can be aware of best approaches for sources exploitation (market/business model level), whereas the community can learn about new trends and technology performance (technological level).