Abstract: The diesel hydrotreating unit encountered constraints in capacity enhancement and stable operation under high-load conditions. Through detailed analysis of process conditions and equipment operations, key bottlenecks were identified: insufficient hydrogen supply, catalyst activity decline, ammonium salt crystallization corrosion in high-pressure heat exchangers, overloading of heating furnaces, and inadequate cooling capacity of air coolers. To address these limitations, targeted optimization measures were implemented including hydrogen purity improvement, feedstock property control, boundary condition operation optimization, periodic professional flushing of heat exchangers, enhanced air cooler efficiency, and refined heating furnace operation parameters. After implementing these measures, the purity of mixed fresh and recycled hydrogen in the hydroprocessing unit increased from 88.9% and 83.5% to above 90% and above 85%, respectively. The new hydrogen consumption decreased by 5% to 10%, the process parameter edge control rate approached 90%, the reactor temperature was stably controlled at around 315℃, andthe decline trend of catalyst activity was significantly slowed down. Simultaneously, the heat exchange efficiency of the high-pressure heat exchanger, the cooling effect of the air cooler, and the thermal efficiency of the furnace were significantly improved. These improvements jointly ensured the stable operation of the unit under high load and brought about significant economic benefits.

Key words: diesel hydrotreating unit, processing load, ammonium salt crystallization, heater load, hydrogen consumption