Direct Heating of Fine Magnetic Particles in a Bubbling Fluidized Bed by Electromagnetic Induction

The electrification of the chemical industry, powered by green electricity, offers an effective pathway toward decarbonization. Although induction heating is a promising approach for electrifying fluidized bed reactors, current applications of direct induction heating in such systems are limited by the relatively low achievable temperatures and reliance on large metal balls. Inspired by magnetized fluidized beds, this study explores the use of fine and cost-effective magnetic particles as heating elements for direct induction heating in a bubbling fluidized bed. The effects of operating methods, particle properties, and the addition of sand particles were systematically investigated. Using an intermittent heating method, the maximum temperature of the gas phase reached approximately 670 °C, which is sufficient for most pyrolysis or cracking processes. As the degree of oxidation increased, both magnetic permeability and electrical conductivity decreased, leading to a substantial reduction in bed temperature. Sand addition improved fluidization performance but decreased the gas temperature. Furthermore, the advantages of direct induction heating were demonstrated by comparing its gas-phase thermal response capability with that of indirect induction heating using a metal rod of equivalent weight. The bubbling fluidized bed using Fe powder as the heating element achieved a gas temperature 150–200 °C higher than that of the Fe rod system, owing to the much larger specific surface area of the Fe powder. Building on these findings, the concept of electro-magneto-fluidization (EMF) is proposed to describe the unique behavior of fluidized beds employing direct induction heating with magnetic particles, based on the principles of magneto-fluidization (MF) and electro-magneto-hydrodynamics (EMHD).