Heat conduction during pyrolysis of rice hulls in a cylindrical furnace

Abstract

The pyrolysis of rice hulls is investigated with a simple device, which allows for measurement of the bulk density change and the change of surface and inside temperature of the rice hull bed. The pyrolysis process can be described by a mathematical model which includes the kinetics of the reaction, the heat transfer by conduction and the heat generation during pyrolysis. The fitting of this model on temperature profile curves has permitted the estimation of the transient thermal conductivity of rice hulls which varied with bulk density and temperature. The obtained experimental results indicate that the significant parameters of pyrolysis are temperature moisture content and bulk density. Under the experimental conditions of the study (moisture content = 0.11-24.04%, temperature = 350-500˚C and bulk density = 113.5-141.4 kg/m³), the thermal conductivity value during pyrolysis was found to follow the following relationship k=3.1x10⁻³ + 4.5x10⁻³ (ρ – 0.15) + 1.9x10⁻⁶ (T-20) J/sec K cm.