اسم المؤلف:
هالة حسين حسن ابو نايلة
اسم المشرف:
محمد فاضل عبد | شاكر محمود احمد
المستخلص:
ان النمو المضطرد في انتاج النفوط الثقيلة والطلب المتزايد على المقطرات الوسطيه اعطى اهمية قصوى لعمليات التكسير في المصافي النفطية، وتعتبر طريقة (H - Oil) باستخدام مفاعلات الطبقة الفوارة واحدة من اهم عمليات التكسير المحفز والتي تهدف الى تكسير النفوط الثقيل | The present work was devoted to study the hydrodynamic characteristics of a lab - scale cold - flow ebullated bed three phase column. It was also to investigate the kinetic behavior of an industrial - scale ebullated bed reactor, licensed by Axens Co., installed and operated in Lukoil refinery at Bourgas - Bulgaria.For the design of experiments in the lab - scale cold - flow column, factorial method was introduced to study the influence of the operating variables (i.e., gas and liquid superficial velocities and the liquid internal reflux ratio) on the objective functions (i.e., individual holdups and bubble characteristics).Pressure gradient method was used to estimate the individual holdups and bed porosity along the column, while photographic method was utilized to obtain images of the moving gas bubble which analyzed using Ai Adobe Illustrator CC (64 Bit) software to determine the geometric characteristics of bubbles.The results showed that liquid internal reflux ratio, which characterized the ebullated bed three phase bubble column, has a predominant effect on the individual holdups and bubble sizes.The operating and geometric variables of the lab - scale cold - flow ebullated bed were carefully selected to simulate the hydrodynamic characteristic of the industrial unit through matching five dimensionless groups (M - group, E?tv?s number, Reynolds number, density ratio and velocity ratio) of the cold - flowlab - scale and industrial systems.The percentage average deviations between each two particular groups of the two systems were (14.7%, 25%, 13.14%, 15.2%, and 20%), respectively. Although this did not result in a perfect match, considering the uncertainty in the industrial units exact operating properties, the match was considered to be sufficiently close.A five - lump kinetic model was selected, to describe the catalytic hydrocracking of heavy oil, to formulate the reaction rate equations of vacuum residue, vacuum gas oil, middle distillate, naphtha, and gases. These equations were inserted into the individual mass balance equation of each lump and then utilized in a program of MATLAB based on the nonlinear least square method to estimate the kinetic parameters (rate constants and activation energies of the proposed reaction pathways), to investigate the effect of the operating variables (e.g., operating temperature, WHSV, and reaction time ) on the kinetic parameters and performance of the industrial ebullated bed reactor. It was found that, - The intra - pellet (internal) diffusion was the rate - limiting step in the H - Oil reaction system. - The effectiveness factor decreases with increasing reaction temperature and WHSV. - The outcomes of the mathematical model confirmed the reaction orders of hydrocracking of vacuum residue and catalyst deactivation to be 2.1 and 0.18, respectively. - Activation and deactivation energies resulted to be quite similar of 48.87 and 50.68 kcal/mole, respectively, meaning that there is no strong effect of the deactivation process over the global hydrocracking reaction. - The hydrocracking of vacuum residue has a higher selectivity toward VGO production than toward other lumps in the following order : VGO < Middle Distillate < Naphtha <Gases. - WHSV has a negative impact on yield fractions of the industrial ebullated bed reactor while the images were different with the operating temperature. The formulated model was validated by comparing its outcomes with the findings of other related model (e.g Sa´nchez and Ancheyta, 2007) from literature. The results of comparison confirmed the reliability of the present model.Key words : Hydrodynamic, Kinetic Parameters, Heavy Oil, Ebullated Bed, Reactor.
