Authors introduce an ultrahigh-temperature (i.e., 2500–3000 °C) continuous fluidized bed furnace, in which the key operating variable is specific electrical resistance of the bed. A correlation has been established to predict the specific electrical resistance for the natural graphite-based precursors. Fluid dynamics models have been validated with the data from a fully functional prototype reactor. Data collected demonstrated that the difference between the calculated and measured values of specific resistance is approximately 25%; due to chaotic nature of electrothermal fluidized bed processes, this discrepancy was deemed acceptable. Optimizations proposed allow producing natural graphite-based end product with the purity level of 99.98 + wt. %C for battery markets.