| In addition to the traditional role that the FCC process plays in heavy oil cracking, nowadays this process is becoming increasingly important as a potentially flexible means to respond to changes in petrochemical product demand It is expected that the FCC process will play a major role not merely as producer of gasoline but of light olefins as well, thus integrating refining and petrochemical industries. Great interest in this direction has been spurred by the relatively novel FCC process configuration, in which a down-flow cracking reactor (or downer) replaces the conventional riser reactor.; Preliminary theoretical studies in the literature have shown the downers could have advantages over risers. As solids back mixing is significantly reduced in the new configuration, higher temperatures are allowable to optimize production of light olefins and gasoline. In this thesis, mathematical models for downer-type FCC unit have been developed, in which conservation equations for nonisothermal downer and regenerator reactors are linked with applicable hydrodynamic findings, 4-lump cracking kinetics in the downer, and complete combustion kinetics in the regenerator. Furthermore, the mathematical models have been validated against experimental data collected in a pilot plant in which the downer and regenerator are 1 m and 1.037 m in length, respectively; and operating temperatures of around 923K can be achieved. Detailed parametric sensitivity studies including key design, operating, and model parameters, have also been carried out using different catalysts. Optimization findings are reported. |
