Effects of gas flow rate on zinc recovery rate and particle properties by pyrolysis of alkaline and zinc-carbon battery waste

- Recycling of alkaline and zinc-carbon battery waste by pyrolysis.
- Thermodynamic investigation for pyrolysis of alkaline battery waste.
- Recovery of Zn as submicron particle from alkaline battery waste.
- Controlling the particle size of recovered Zn from spent alkaline batteries.

Zinc (Zn) recovery rate and the properties of Zn particles obtained by pyrolysis of alkaline and Zn-C battery waste were studied at a reaction temperature of 950 °C for 60 min residence time using various N2(g) flow rate (0.5-3.0 L/min) without using any additive. The battery black mass was characterized with respect to the properties of waste battery particles, and chemical content. The thermodynamics of the pyrolysis process was studied using the HSC Chemistry 5.11 software. A carbothermic reduction reaction of the washed battery black mass by Milli-Q water takes place at choosen temperature and makes it possible to produce fine Zn particles by a rapid condensation following the evaporation of zinc from the pyrolysis batch. The amount of Zn that can be separated from the black mass slightly increases at higher N2(g) flow rates than 0.5 L/min and stabilizes by controlling the gas flow. Zn recovery of 80% was achieved at 950 °C and 60 min residence time using 1.0 L/min and higher flow rates by pyrolysis of the washed battery black mass. The pyrolysis residue was shown to be mainly composes of MnO and Mn2O3 with traces of impurities. The particle size of the produced Zn particle decreased from 874 nm to 534 nm with increasing flow rate and those particles are formed by the aggregation of primary condensed particles with nano-range sizes. The morphology of the zinc particles also changes from hexagonal shape to spherical morphology by increasing gas flow rate.