Effect of the Operating Pressure on Residual Oil Hydroprocessing

The atmospheric residue desulfurization (ARDS) process is one of the main processing units in Kuwaiti refineries. In the ARDS process, a graded catalyst system consists of different types of catalysts. The performance of the catalyst system is mainly influenced by feedstock quality and reaction conditions, such as temperature and pressure. In this study, the effect of operating hydrogen pressure on the life cycle of the catalyst is investigated using two feedstocks, Kuwait heavy crude atmospheric residue (KHC-AR) and Eocene-AR, using an analogous process condition that is generally used in refinery. The pilot-plant hydrotreatment results demonstrated an effect of hydrogen pressure on the catalyst performance for the hydrodesulfurization (HDS) activity and sustaining a target sulfur level of 0.6 wt % in the product. The required sulfur level in the product was adjusted by raising the temperature gradually to compensate for the catalyst deactivation. The activity test for two different feeds were studied up to 4000 h time-on-stream (TOS) at 120 and 150 bar hydrogen pressure. The results showed that the performance of the catalyst system under an operating pressure of 150 bar was better than that at 120 bar. The reaction rate is accelerated by high pressure because it reduces the effect of the coke deposition on the catalyst.