(474g) Multi-Approach Simulation of Hydrodynamics, Heat Transfer and Cracking Reactions in an Industrial FCC Unit

Multi-approach simulation of hydrodynamics, heat transfer and cracking reactions in an industrial FCC unit

Abdallah S. Berrouk

Chemical Engineering department, Petroleum Institute, Abu Dhabi, UAE

*PO Box 2533 Abu Dhabi, UAE, aberrouk@pi.ac.ae

Abstract

The global demand for propylene is growing faster than the anticipated supply from ethylene plants. Fluid catalytic cracking (FCC) units, as the second largest source of propylene (about 30%), are expected to bridge much of the propylene supply/demand gap. Fluid catalytic cracking is a quite complex process that takes place in an equally complicated hardware consisting of many components such as riser, stripper-disengager, and regenerator to name only the most important ones. Its design and operating envelopes have constantly been improved to ensure its flexibility and economic efficiency so it can positively adapt to changes in the refining markets. Developing FCC processes is not a trivial task due to the complexity of the fluid and chemistry systems taking place in FCC units.

A large body of work has been done in order to optimize the existing FCC processes and to design new ones that should effectively answer the changes in the market needs. Among the tools used to carry on such a research on FCC units, Computational Fluid Dynamics (CFD) has seen its use growing over the years as a state-of-the-art technology capable of improving current FCC units’ designs and operations at a low cost and in a reasonable amount of time. In this regard, three-dimension reactive gas-particle CFD models were built to simulate the interplay between hydrodynamics, heat transfer and cracking reaction behaviors inside a large-scale Fluid Catalytic Cracking (FCC) unit. Two different CFD approaches namely two-fluid model (TFM) and multiphase particle-in-cell model (MP-PIC) were used to simulate the operations of FCC riser, regenerator and stripper-disengager. To describe the cracking chemical reactions taking places in FCC riser, 4-lump and 11-lump kinetic models were tested. Simulation results from the different CFD approaches will be presented and the potential of these approaches to be used for troubleshooting, debottlenecking, and optimization of FCC units’ operations will be discussed. The numerical results of this investigation should serve as guidelines for possible FCC process redesign and optimization.