Development of a new metallurgical process for closed-loop recycling of discarded Nickel-Metalhydride-Batteries

摘要

The demand on Nickel-Metalhydride-Batteries (Ni-MH) is increasing rapidly since their market launch in the early nineties. The market share of these batteries is expected to significantly expand in the near future due to their possible application as board batteries in cars respectively as substitute for Ni-Cd-batteries in power tools. Nowadays there is no suitable recycling process existing. Several hydrometallurgical research projects were actually investigated, but none of them has been transferred into industrial application. Today the discarded batteries are used in the steel industry for alloying because of their Nickel content. Cobalt and Rare Earth (RE) are slagged and lost for recycling. The entire value of the metals in discarded Ni-MH is estimated at4.0-4.8 ?/kg. In a governmental funded research project IME cooperates with two industrial partners for the processdesign and a feasibility study. The goal of the project is the development of a pyrometallur-gical closed-loop recycling process for metal recovery from Ni-MH. After comminution the steel shell is separated. The resulting Ni-MH-fraction is smelted in an electric arc furnace. The products are a Nickel-Cobalt alloy and a slag phase highly enriched with RE-oxides. Different fluxes are investigated in order to reach best separation of the two phases and to optimize metal yields. Extensive laboratory scale experiments have been successfully implemented. The most suitable slag systems were then tested in a 480 kW pilot-plant electric arc furnace. The results of tests with battery scrap from used batteries as well as production waste will be reported. The slag will be processed hydrometallurgically to obtain RE.clorides from which by means of molten salt electrolysis a 'Mischmetal' is produced. Both the Nickel-Cobalt alloy and the 'Mischmetal' are suitable for direct reuse in Ni-MH-battery production.