Microwave Pyrolysis for Efficient Treatment of Radioactive Oil Sludge Waste: Experimental and Machine Learning Approaches

Oil sludge waste (OSW) represents a substantial liability for the oil industry, given its composition of water, crude oil (heavier fractions), and sediments, as well as the presence of naturally occurring radioactive materials (NORM). This study presents a novel approach focused on the microwave-based drying of OSW containing NORM, a topic that has received little to no attention in the literature. While microwave pyrolysis has been explored for sludge treatment in general, previous studies have not addressed the specific challenges associated with the safe drying and volume reduction of radioactive OSW. Moreover, to the best of our knowledge, no prior work has applied machine learning algorithms to model and interpret the relationship between OSW composition and process performance during microwave drying of such complex waste. In this study, a dedicated system was developed to selectively remove water and oil from OSW while concentrating the radioactive content in the solid fraction, enabling safer and more compact disposal. The system was designed to take advantage of rapid and selective volumetric heating promoted by microwave irradiation, and to facilitate the capture of volatile compounds and radionuclides at the gas outlet. The process resulted in an average condensate recovery of 71% under microwave power of 993 W and a total treatment time of 15 min. The findings demonstrated that microwave treatment was an effective approach for treating OSW and obtaining dry sediment from samples with higher water and oil content.