(20a) Mapping Hydroprocessing Reactor Operating Regimes

During hydroprocessing (hydrotreating and hydrocracking), petroleum distillates and hydrogen pass through trickle-bed catalytic reactors at high temperatures and pressures with relatively large hydrogen flow. These conditions result in partial vaporization of oil and partial dissolving of hydrogen in liquid to form a vapor-liquid equilibrium (VLE) system with both vapor and liquid phase containing oil and hydrogen. Our previous related studies with middle distillates have shown that as the temperature and hydrogen flow rate increase and pressure decreases, the VLE results in significant decrease in liquid phase flow rates as well as significant changes in liquid phase properties. This could significantly affect the flow dynamics in the reactors and therefore the catalyst performance. For pilot plant studies, this becomes especially important since any discrepancies from the desired ideal operation regime (plug flow, fully catalyst wetting, free of reactor wall effect, etc) could result in unreliable and unrepresentative data for commercial scale-up. Therefore, it is necessary to correctly predict the VLE in hydroprocessing reactors and furthermore predict the operation regimes under which pilot plant studies can generate reliable and representative results.

In this study, VLE in middle distillates pilot plant hydrotreaters are predicted using an in-house calibrated flash calculation program under various operating conditions. The calculated VLE results are further used to predict the flow dynamics in the hydrotreaters to investigate if the hydrotreaters are operated under the desired operation regime (plug flow, fully catalyst wetting, free of reactor wall effect, etc.). Detailed mapping of hydrotreater operating regimes are discussed based on various operating conditions.