The effect of temperature and mesh size on the dielectric properties of low grade nickel ore at 915 MHz and 2450 MHz

Abstract

The present study aims to provide a preliminary guide for microwave processing of low grade nickel ores in wrapped form by investigating the dielectric characteristics based on the permittivity determination from 25 to 1300 °C at different apparent densities, mesh sizes, and two industrial microwave frequencies (915 and 2450 MHz). Dielectric constant () variation with the increase of temperature has three distinct stages: decreasing stage in the range 25–200 °C, fluctuating stage in the range 200–1000 °C, and increasing stage in the range 1000–1300 °C. Also, dielectric loss () of the nickel ore varies in the similar way. Both and increase with decreasing mesh size in the investigated 3 stages. Microwave penetration depth () of the nickel ore increases initially due to dewatering and then decreases due to thermal enhanced microwave absorption ability, with increasing temperature. Reflection loss (RL) exhibits dependence on the imaginary thickness. Microwave heating behavior established the critical temperature effect and mesh size dependence on the microwave absorption ability.