Abstract: The research and industrial practice of producing high-pressure canned-motor pump sealing oil with heavy vacuum gas oil and hydrogenation stable high temperature solvent as base oil in direct coal liquefaction process were introduced. The feasibility of using light and heavy oil products from coal liquefaction, and high and medium temperature solvents from hydrogenation stabilization devices as sealing oil base oil was compared respectively. The second line oil and high-temperature solvent at the side of coal liquefaction vacuum column were used as base oil. By optimizing the coal liquefaction process, high-pressure canned-motor pump sealing oil products that meet quality requirements could be produced by blending depressurized heavy gas oil and high-temperature solvent oil in a mass ratio of 1:1.93 and 1:1.50, respectively. Based on the use of 2 600 tons of sealing oil per production cycle in the coal direct liquefaction unit, using self-produced sealing oil instead of purchased sealing oil can save about 24.44 million yuan per year, indicating significant economic benefits of using self-produced sealing oil for the high-pressure canned-motor pump in the coal liquefaction unit.

Key words: direct coal liquefaction process, high-pressure canned-motor pump, sealing oil