Comparative study of olive pomace pyrolysis with/without ultrasonic preprocessing

Abstract

Although ultrasonic preprocessing has been mainly used before olive pomace anaerobic process, there has not been any study of the effect of ultrasonic preprocessing on olive pomace pyrolysis. Therefore, in this study, ultrasonic was applied to the biomass as a preliminary process before the pyrolysis to examine its effects on both quality and quantity of the end products. Within this scope, pyrolysis gas, liquid, solid product yields, char inorganic contents and pyrolysis liquid organic fractions with or without preprocessing were investigated. Although the preprocessing resulted in a 5-10% decrease in bio-oil quantity, it enabled obtaining pyrolysis liquids with higher quality by increasing the percentage of the aliphatic compounds. Among the ultrasonic preprocessing conditions studied, it turned out that the one which applied 30 W power for 10 min was the best condition which provided the highest decrease in the percentage of the oxygenated compounds by 24% within the pyrolysis liquid. Under all ultrasonic preprocessing conditions, when compared to the bio-oils obtained without preprocessing, the biggest increase occurred in the organic compounds with carbon numbers between 9 and 15. Moreover, when the preprocessing was applied, the total number of compounds in the pyrolysis liquid increased by at least 8 and at most 49. While the ultrasonic preprocessing caused a decrease in the char quantity by less than 1%, the inorganic content of the chars altered based on the preprocess condition. The highest total inorganic quantity in chars was obtained at the pyrolysis after preprocessing at the lowest power and the shortest duration.