Optimizing Energy Characteristics of Palm Kernel Shells via Microwave Preheating Torrefaction

Torrefaction is a thermal process used to enhance the properties of biomass for better energy efficiency in various energy applications. This study aims to optimize the characteristics of torrefied solid Palm Kernel Shell (PKS) using a preheating microwave to achieve comparability with coal for combustion purposes. It investigates the effects of microwave preheating power levels and torrefaction temperatures and duration on the properties of the solid products. The experimental studies were conducted in a modified torrefaction reactor equipped for both microwave and electric heating. Before torrefaction began, nitrogen gas was introduced into the reactor at a flow rate of 25 L/min for 10 minutes, serving as an inert atmosphere. In this torrefaction process, microwave preheating at power levels of 360, 540, and 720 Watts was applied to each sample for 5 minutes before proceeding with electric heating. Torrefaction temperatures were set at 200 °C, 250 °C, and 300 °C, with durations of 20 and 30 minutes. The study has examined the mass of the sample remaining after torrefaction. Following this process, the physical and chemical properties of the solid products were analyzed through Proximate and Ultimate Analyses, Fourier Transform Infrared Spectroscopy (FTIR), Thermogravimetric analysis (TG-DTG), and Scanning Electron Microscopy (SEM). The results have shown significant improvements in the physical and chemical properties of the torrefied products, with maximum calorific value increasing by about 34.7% compared to the raw material. Torrefied PKS yielded solid products with properties comparable to bituminous coal.