(81c) Modeling and Simulation of Diesel Hydrotreaters for ULSD Production: Selection of an Optimal Catalyst Composition
AIChE Spring Meeting and Global Congress on Process Safety
2018
2018 Spring Meeting and 14th Global Congress on Process Safety
Process Development Division
Advances in Product/Process Design & Development II
Tuesday, April 24, 2018 - 10:59am to 11:21am
This work focuses on the development of a flexible model for commercial ULSD hydrotreating units that predicts product properties, yields and hydrogen consumption for different catalyst compositions. The model uses a species set that contains the necessary structural information required to characterize different types of sulfur species as well as to distinguish among mono-/poly-aromatics, naphthenes and naphtheno-aromatics to model relevant reactions. The proposed reaction set accounts for desulfurization pathways by hydrogenolysis and hydrogenation, saturation of poly-aromatic, mono-aromatic and olefin species, cracking, and inhibition effects by nitrogen impurities in the feed.
Experimental data from the literature for CoMo and NiMo catalysts at different levels of desulfurization and aromatic saturation with temperature, pressure, and LHSV were used to determine two sets of kinetic parameters that represent each type of catalyst. Case studies were developed to assess the performance of each individual catalyst and combinations of catalysts in commercial ULSD hydrotreaters under different scenarios covering HDS and cetane improvement with limited hydrogen consumption, increasing amounts of light cycle oil in a straight-run gas oil feedstock blend, and low to high pressure operation from start of run to end of run conditions. For each scenario, an optimal catalyst composition was found, constrained to a final product sulfur specification of 15 ppm.