Abstract: The designed processing capacity of a diesel hydrogenation unit was 0.8 Mt/a, and the actual maximum processing capacity was 0.9 Mt/a. When the processing capacity was over 95 t/h, the pressure at the inlet and outlet of the heating furnace fluctuated in a sinusoidal manner, and the pipeline at the outlet of the heating furnace vibrated regularly. The pressure fluctuation of the reaction system had not been eliminated by adjusting control valve, water injection pump, and crossing line of the heat exchanger. With the help of thermal imaging, it was found that there was rotating flow in the outlet pipeline of the heating furnace. After the outlet pipeline of the heating furnace was optimized during the maintenance, not only the pressure fluctuation of the reaction system was eliminated, but also the processing capacity reached the design value, effectively ensuring the economy and safety of the unit.

Key words: diesel, hydrorefining, pressure fluctuation, data calibration, heating furnace