A novel way of using pyrolytic gas derived from waste rubber: Pyrometallurgical reduction of NiO

In the present study, a novel way of using pyrolytic gas generated by the pyrolysis of waste rubber was introduced. The method involves reduction of metal oxides by pyrolytic gas. The pyrometallurgical reduction behavior of NiO was studied to demonstrate the feasibility of the process. The rubber pyrolysis and the NiO reduction experiments were carried out in a horizontal tube at 1000 K using Ar as carrier gas. It was determined that the waste rubber was completely pyrolyzed in Ar flow. The extent of NiO reduction was investigated as a function of mass ratio of rubber to NiO (0-7.345). X-ray diffraction and mass measurements revealed that single-phase Ni was obtained at the ratio of 0.734. Complete reduction of NiO to Ni was predicted at the lower mass ratios by thermodynamics. The quantitative discrepancy between the thermodynamics and the experiments was discussed. Thermodynamic analysis of the Ni-O-C-H-Ar system indicated that NiO was reduced to Ni by the gaseous species (essentially H₂, CH₄, C₆H₆) at 1000 K. The novel route presented here may be extended to the reduction of other materials using waste rubber.