![]() New advances in the two-stage Unicracking process design include several innovations in each reaction section of the design. Overall, the two-stage design allows optimization of conversion severity between the two stages, maximizing overall distillate selectivity. Optimum severity can be set for each stage to achieve catalyst life target with minimum catalyst volume. The catalyst system can be optimized to obtain a highly distillate selective overall yield structure. This significantly impacts reaction rates, particularly cracking reaction rates, leading to different product selectivity and catalyst activity between the two-stages. The first-stage reaction environment is rich in both ammonia and hydrogen sulfide generated by hydrodenitrogenation and hydrodesulfurization of the feed. However with advancements in hydrocracking catalyst technology, and the demand for maximizing distillate yields from heavier feedstocks, two-stage design offers a cost-effective option for a larger capacity maximum distillate unit operation.Ī major difference between the first and second stage hydrocracking reactor reaction environments lies in the very low concentrations of ammonia and hydrogen sulfide in the second-stage (see figure 2). The hydrocracking catalyst needs to function within the reaction environment and severity created by the flow scheme that is chosen.ĭuring the early years of hydrocracking, refiners were mainly interested in maximizing production of naphtha for reforming to high octane gasoline. The design of hydrocracking catalyst changes depending upon the type of flow scheme employed. Two-stage flow schemes are economical when the throughput of the unit is relatively high. These flow schemes offer several advantages in processing heavier and highly contaminated feeds. The second-stage provides the remaining conversion of recycled oil so that overall high conversion from the unit is achieved. In the separate hydrotreat flow scheme the first stage provides only hydrotreating while in the two-stage process the first stage provides hydrotreating and partial conversion of the feed. UOP two-stage Unicracking process flow schemes can be a separate hydrotreat or a two-stage process as shown in Figure 1. The basic flow schemes considered by UOP are single-stage or two-stage design. In particular, UOP LLC Company is one of the most active society in this field. There are several processes presently able to meet individual refinery needs and project objectives. Worldwide economic growth continues to drive demand for transportation fuels, and in part ![]() Author: Vincenzo Piemonte, Associate Professor, University UCBM – Rome (Italy) ![]()
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