(148c) Modelling and Integration of Diesel Hydrotreater Kinetics with Refinery Hydrogen Networks

The current global trends to refine heavier crude oils and the stricter environmental regulations have enhanced the importance of hydroprocessing. Hydrogen, the essential feed of hydroprocesses, has a direct impact on the process performance and the final economic profits. Therefore, kinetic modelling of hydroprocessing units would provide detailed insights into the process as well as would enable opportunities to perform process optimisation and better hydrogen network management.

Based on an industrial configuration, a diesel hydrotreater model has been developed using industrial operating data. Bulk properties of feedstock measured through laboratory analysis are transformed into 18 molecular lumps based on the database that contains both bulk properties and molecular information of pre-collected samples. A kinetic model with molecular lumps is used for the reaction considering the operating conditions, including LHSV, makeup H2, recycle H2, reactor inlet temperature, H2 quench, and catalyst life. The model also predicts the light hydrocarbon generation that is critical for accurately modeling H2 recycle composition (on process level) and H2 network optimisation (on site level). The difference in properties between product and feed, such as distillation profile, cetane number and flash point, is predicted from the change in molecular lumps. A multi-period process optimisation model has also been developed. The proposed methodology changes the optimisation objective from the traditional methodology of reducing operating cost to improving the overall economic performance.

The developed kinetic hydroprocessing model is then applied to overall H2 network optimisation. This integration enables accurate evaluation of several changes to the diesel hydrotreating unit, such as: increased throughput to make full use of hydrogen surplus, increased proportion of cheaper feedstocks, variable H2 purity in the makeup for maximum H2 cascade utilization, etc. A case study is carried out to show the benefits of the developed methodology.