Model predictive control for production of ultra-low sulfur diesel in a hydrotreating process

Abstract

There is a continual desire around the world to reduce the sulphur content of diesel fuel to ultra-low levels (below 10 ppm) due to environmental concerns and the intention of improving air quality and lowering harmful exhaust emissions of diesel engines. In this work, a hydrodesulfurization unit fed with multiple diesel streams was addressed using a phenomenological mathematical model aiming to produce Ultra-Low Sulfur Diesel (ULSD). A three-phase model of a trickle-bed reactor was considered. A model-based predictive control strategy (MPC) was implemented with the objective of controlling the sulfur concentration at the exit of the reactor, manipulating the flow rates of the oils entering the system, the superfcial velocity of the gas and the temperature of the load in the presence of disturbances in the concentration of organic sulfur compounds in the fed oils. It was observed that the control strategy reduced the contaminant content to the specifcation range of diesel S10.