Abstract: In view of the problem that the oil yield of the first industrial direct coal liquefaction unit is lower than the design value during commercial operation, according to the operation data of the coal liquefaction unit under the best working condition, the appropriate thermodynamic physical property model is selected through comparison, and using HYSYS application in Aspen One software, the operation effects of high-pressure and medium-pressure flash separation processes are simulated to explore the methods to improve the yield of liquefied oil in coal liquefaction unit. The existing high-pressure separation and medium pressure separation are highly sensitive, which makes the hot high-pressure separator and hot medium pressure separator liable to cause entrainment, leading to the reduction of the oil extraction rate and the yield of liquefied oil. In view of this problem, the optimization suggestions on the process and equipment design of hot high-pressure separator and hot medium pressure separator are put forward. At the same time, it is suggested to add hydraulic turbine between the two flash tanks to recover power, reduce the friction and thinning of pipeline and improve the operation stability.

Key words: coal direct liquefaction, high pressure separation, process simulation, oil yield