Self-Ignition Temperature in High-Moisture Rubber Woodchip: A Numerical Study Using COMSOL Multiphysics

This study investigates the self-ignition temperatures of rubber woodchip with high moisture content (46 wt%) using COMSOL Multiphysics simulation. Rubber woodchip is a major renewable energy source in Thailand's biomass power plants, especially in the southern region with heavy rainfall. The research solves this important safety issue. The simulation model incorporates heat transfer mechanisms, including conduction and diffusion, along with chemical reactions. Experiments were conducted using wire mesh baskets of 8, 10, and 12 cm sizes, with temperature measurements taken at the center, outer surface, and oven. Results showed that self-ignition occurred at ambient temperatures of 199 °C, 192 °C, and 184 °C for the respective basket sizes. The simulated center temperatures during self-ignition (214-218 °C) demonstrated good agreement with experimental values (215-222 °C), with deviations of approximately 6 °C. Smaller basket sizes exhibited faster self-ignition times due to more efficient heat transfer. The validated model provides a reliable tool for predicting self-ignition risks in industrial applications, contributing to safer storage and handling practices in Thailand's biomass power sector.