Modeling of Hydrogen Consumption and Process Optimization for Hydrotreating of Light Gas Oils

Abstract

The main objective of this work was to develop a regression model for hydrogen consumption during hydrotreating of several gas oils such as virgin light gas oil (VLGO), hydrocracker light gas oil (HLGO), coker light gas oil (KLGO), and a partially hydrotreated heavy gas oil (PHTHGO) stream over commercial NiMo/ɣ-Al2O3 in a micro-trickle bed reactor. The experiments covered a temperature range of 353-387 °C, pressure range of 8.27-10.12MPa, LHSV range of 0.7-2.3 h-1, and H2/oil ratio = 600 N m3/m3. H2 consumption can be determined by different approaches; therefore, the best approach was selected by comparing the following: analysis of H2 content in gas streams, analysis of H2 content in liquid streams, and an approach reported in literature that is based on the decrease of the aromatics content. The comparison showed better agreement between the analysis of H2 content in gas streams and the method reported in the literature. For this reason, the analysis of gas streams was selected to build a regression model by performing statistical analysis of the effects of process conditions on H2 consumption data at the conditions mentioned above. H2 consumption based on gas analysis decreased in the following order: KLGO>VLGO>HLGO>PHTHGO. The H2 consumption regression model developed in this work was then tested with a new batch of experimental data, and the model performed better than similar correlations available in the literature. The secondary objective of this work was to study the effects of process conditions indicated above on hydrodesulfurization (HDS), hydrodenitrogenation (HDN), and hydrodearomatization (HDA) conversions by statistical analysis. The experimental data of hydrotreating conversions were then used to build regression models and carry out the optimization of process conditions for each feedstock. The optimum sets of conditions for the hydrotreating of each feedstock are the following: VLGO (T = 353 °C, P = 9.37 MPa, LHSV = 0.9 h-1), HLGO (T = 383 °C, P = 10.12 MPa, LHSV = 0.9 h-1), KLGO (T = 372 °C, P = 7.79 MPa, LHSV = 0.7 h-1), PHTHGO (T = 379 °C, P = 9.44 MPa, LHSV = 0.7 h-1). In summary, the optimum hydrogen consumption as well as hydroprocessing conditions for all the four different feedstocks are substantially different. This information is critical in operating a commercial hydrotreater efficiently.