Abstract: Salt scaling frequently occurred in the hydrocracking unit in PetroChina Jinzhou Petrochemical Company. The scaling was faster especially after coker gas oil was added into the feed. The contents of heteroatoms in crude oil, vacuum gas oil, coker gas oil, and reformate hydrogen were determined. It is verified that the main component of the scale is ammonium chloride and the scaling is caused by the excess chlorine and nitrogen content in the hydrocracking feedstocks, and high nitrogen content in feed from coker gas oil accelerates the trend of scaling formation.

Key words: heat exchanger, salting, hydrocracking, ammonium chloride