Dielectric Properties and Electrical Conductivity as a Characteristic of Degradation of Coal Tar Wash Oil

Coal tar wash oil plays a crucial role in the absorption of benzene hydrocarbons from coke oven gas. During the operation of a benzene plant, the oil gradually loses its operational properties, necessitating the application of diverse physico-chemical analysis methods to identify causes and select suitable absorbents from different manufacturers. The use of additional methods of analysis allows to find out the causes of oil deterioration and make informed decisions on its recovery or replacement, thus ensuring constant efficiency of the benzene unit. It was found that the wash oil is subjected to temperature cycling stresses that are, in principle, characteristic of engine oils. This was the basis for the application of similar degradation testing methods, among which the most attractive are the determination of dielectric properties and electrical conductivity. Fresh oil consistently shows lower breakdown current densities than operating oils at all test voltages. Lean oil, particularly at higher voltages, has a notable increase in current density, suggesting worse breakdown performance. Fresh oil maintains the most stable breakdown behavior across voltages, while lean oil is the least stable. In addition, the electrical resistivity of coal tar flushing oil samples serves as a comprehensive indicator of changes in oil composition, molecular weight and contaminant accumulation, which provides valuable insights for quality assessment and further studies on oil degradation mechanisms.