Sustainable and Energy Efficient Electrochemical Production and Refining of Metals

The project work should contribute to improve the Norwegian electrolysis industry that produces of aluminium, zinc, nickel and copper more energy efficient and more environmentally friendly. New knowledge useful for the industry is achieved by performing controlled laboratory experiments. Important results were published in international journals. One of the important goals was to develop new electrode materials for oxygen evolution during electrolysis to produce zinc and copper, so that undesired lead anodes may be substituted. Experimental results and computations have given more fundamental knowledge about the mechanisms governing the efficiency and the energy consumption of the aluminium electrolysis process. In a separate project activity we tried to develop a new kind of thermoelectric cell to utilise the waste heat generated in the aluminium production process and other high temperature processes for producing metals. The project has educated two PhD candidates and two other PhD candidates are under way.

The main impact of this project will probably be the increased knowledge of important mechanisms that affect the processes for achieving high efficiency, low energy consumption, good product quality and reduce environmental problems for the processes for primary production of aluminium, nickel and zinc. It will also give a good foundation for developing a new kind of thermoelectric cells based on molten salt electrolytes with CO2|O2 electrodes to be used to harvest industrial waste heat. The project has also given a boost in the competence level for the involved research groups at NTNU and SINTEF. Many publications have been published in good quality international journals with high impact factors. We believe that our research will be acknowledged across the community working to improve the metal producing processes.

The focus in the present project is on the energy consumption in electrochemical manufacture of metals, and we bring together aluminium industry and companies based on electrowinning and electrorefining in aqueous electrolytes. Although the processes are different electrochemistry is a generic discipline, and there are common challenges as well as complementary knowledge within the different industries. Bringing together the aluminium experts (mainly at SINTEF) and the experts in aqueous electrochemistry (mainly at NTNU) provides the opportunity to learn from each other's strong sides, leading to increased competence in both camps. Also, the industry partners should benefit from the collaboration across the normal boundaries between the related processes, and it is believed that the project will lead to increased competence for all the partners. The project is divided into three work packages (WP), each of them addressing themes that are relevant for more than one of the industry partners involved. WP1 "Anode development" focuses on developing and electrochemical testing of dimensionally stable anodes (DSA) for replacement of the lead anode currently used in electrowinning of zinc and copper. WP2 "Ionic and electronic transport" addresses the descript ion of transport processes at the cathode. This is a prerequisite in order to attain a more reliable model for the loss in current efficiency in the aluminium electrolysis, where electronic conduction as well as diffusion should be taken into account. Ach ieving dendrite-free deposition of solid metals (Ni, Cu) and avoiding stress at the cathode during electrowinning of nickel are also themes in this WP. In WP3 "Energy recovery" the main topic is to develop thermoelectric electrochemical cells for electri c power production. By replacing semiconductors with electrochemical cells, it may be possible to increase the power production and conversion efficiency.