Abstract: Taking a 4 Mt/a diesel and gas oil hydrocracking unit as an example, through analyzing the hot and difficult problems such as the pressure drop of the wound tube heat exchanger and vibration of the feed pipeline, the corresponding solving methods and measures were put forward. At the same time, the energy-saving optimization of large-scale hydrocracking unit was carried out. The results indicated that in order to realize the accurate control of the wound tube heat exchanger temperature, the "X" type control mode should be adopted in the design stage of the new unit. After the unit was scaled up, optimization scheme should be adopted to meet the requirements of the pipeline based on the operating characteristics and site layout issues of the unit. For the process flow with naphtha stabilization column and naphtha fractionation column, it was important to consider the medium characteristics to reduce the impact of pipeline liquid hammer and pipeline vibration. In addition, the optimized operation mode of the new hydrogen compressor and ordinary centrifugal pump could provide a certain reference for the smooth operation of large-scale hydrocracking unit.

Key words: hydrocracking, energy saving and consumption reduction, naphtha, air cooled heat exchanger, hydrogen consumption, jet fuel