Abstract: The gas content changes in each stage of hydrodeacidification, furfural refining, liquid phase denitrification, and clay refining of naphthenic transformer oil were investigated with the atmospheric cut 2 of naphthenic base crude oil produced by CNOOC as raw material. The results showed that the gas contents of H2, CO2, CH4, C2H4, and C2H6 in transformer oil increased significantly in the electro-refining stage of liquid phase denitrification. By adjusting the process conditions of electro-refining and adding vacuum filtration device, the gas content could be reduced, and the product could met the technical requirements of the electric power industry standard.

Key words: transformer oil, atmospheric cut 2, combined process, gas, electric refining