Design and analysis of fluid catalytic cracking unit for gasoline production

Abstract

This study concentrated on the design and analysis of a fluid catalytic cracking process consisting of a reactor and a regenerator and can be divided into three main parts. Firstly, the performance improvement of a catalytic regenerator in the fluid catalytic cracking (FCC) process for gasoline production to achieve a higher burning efficiency was focused. This study performed a systematic model-based analysis of a downer-type regenerator to recover the activity of FCC catalyst by using a one-dimensional model of the regenerator coupled with its hydrodynamic characteristics and the kinetics of catalyst regeneration. The results of a sensitivity analysis showed that higher carbon content on spent catalyst causes a higher regeneration temperature. Ratio of the recycled-to-spent catalyst flow rate in range of 1.0-3.5 and temperatures of the spent catalyst in range of 703.15-803.15 K have insignificant effects on the overall performance of the regenerator. The suitable superficial gas velocity and the spent catalyst flow rate are in range of 4-7 m s⁻¹ and 20-40 kg m⁻²s⁻¹, respectively. Next, the performance of the regeneration of the FCC catalyst by considering the steam gasification reaction with burning reaction was studied. The simulation results show that the steam gasification reaction which is an endothermic reaction can help reduce the regeneration temperature and gives hydrogen as a valuable byproduct. Finally, an integrated downer reactor and riser regenerator system was studied based on the one-dimensional model of the downer reactor and riser regenerator. The simulation results on the effect of the catalyst-to-oil (CTO) ratio which is the key parameter in designing the FCC reactor reveal that at the CTO ratio of 20, the integrated system can operate efficiently with the conversion of gasoil of 0.85 and the yield of gasoline of 0.55. Moreover, the heat balance of the system can be maintained under this operating condition.