COMBINED TECHNOLOGIES FOR THE PURIFICATION OF USED MOTOR OILS FOR ENGINEERING HYDRAULIC SYSTEMS

Abstract

The paper presents a comprehensive review and comparative analysis of modern methods for the purification and regeneration of used motor oils from the standpoint of their technical efficiency, practical applicability, and feasibility for engineering systems. The relevance of the study is driven by the growing volumes of used lubricating materials, the increasing cost of primary petroleum resources, and the necessity to reduce the negative environmental and industrial impacts associated with improper disposal of waste oils. It is demonstrated that used motor oils retain a significant potential for reuse provided that effective purification technologies are applied. The study systematizes physical, physicochemical, chemical, and combined methods of motor oil purification. Physical methods considered include sedimentation, filtration, centrifugation, vacuum distillation, magnetic separation, and ultrasonic treatment. Their advantages, limitations, and areas of rational application are analyzed. Particular attention is given to physicochemical methods such as adsorption, solvent extraction, coagulation, flocculation, membrane separation, and thermo-oxidative treatment, which enable deeper removal of aging products and oxidation compounds. Chemical purification methods, including acid-alkali treatment and hydrotreating, are also examined as technologies capable of restoring base oils with properties close to those of virgin lubricants. Based on the analysis of scientific literature, it is established that no single purification method ensures complete restoration of the performance properties of used motor oils, especially under the conditions of small and mediumscale industrial enterprises. The expediency of applying combined purification technologies is substantiated. Such technologies integrate sequential operations of sedimentation, centrifugal separation, coagulation treatment, phase separation, and fine filtration. It is shown that combined methods make it possible to remove mechanical impurities and contaminant particles with sizes up to 1 μm, thereby producing purified oils suitable for reuse as working fluids in hydraulic systems and simplified hydraulic drives. The presented generalizations may be applied in the development and selection of technological schemes for the regeneration of used motor oils in engineering practice.