Effect of applicati̇on of microwave drying pretreatment on pyrolysis characteristics and kineticsof industrial peach stone wastes

In the present study, the effect of microwave pretreatment on the pyrolysis characteristics and kinetics of industrial peach stones was investigated by thermogravimetric analysis. Samples of peach stones with a particle size range of 180-425 µm were reserved for use in both microwave and oven drying experiments. Three different heating powers (100, 180 and 300 W) and three different operating duration (150, 350 and 600 s) were used in the microwave drying process. Thermogravimetric analysis was carried out at 10, 20, and 40 ºC/min heating rates under a nitrogen atmosphere for the samples that were dried using microwave or oven. Thermal characterization revealed that the pyrolysis of peach stone consists of four stages, two of which are active. After the characteristic temperatures were determined in the active stages for each sample, activation energies were calculated via these temperatures using various differential and integral kinetic methods. Activation energy values calculated by Flynn-Wall-Ozawa, Starink and Friedman methods were compatible with each other and were in the range of approximately 115-135 kJ/mol for the second stage and 135-165 kJ/mol for the third stage under all applied operating conditions. By application of microwave pre-treatment, the effect of the studied microwave power on the average activation energy ranged from 1% to 16.7%, while the effect of the studied operating duration on the average activation energy varied between 0.07 and 17.2%.