A Review of Modelling of the FCC Unit–Part I: The Riser

Abstract

Heavy petroleum industries, including the fluid catalytic cracking (FCC) unit, are useful for producing fuels but they are among some of the biggest contributors to global greenhouse gas (GHG) emissions. The recent global push for mitigation efforts against climate change has resulted in increased legislation that affects the operations and future of these industries. In terms of the FCC unit, on the riser side, more legislation is pushing towards them switching from petroleum-driven energy sources to more renewable sources such as solar and wind, which threatens the profitability of the unit. On the regenerator side, there is more legislation aimed at reducing emissions of GHGs from such units. As a result, it is more important than ever to develop models that are accurate and reliable, that will help optimise the unit for maximisation of profits under new regulations and changing trends, and that predict emissions of various GHGs to keep up with new reporting guidelines. This article, split over two parts, reviews traditional modelling methodologies used in modelling and simulation of the FCC unit. In Part I, hydrodynamics and kinetics of the riser are discussed in terms of experimental data and modelling approaches. A brief review of the FCC feed is undertaken in terms of characterisations and cracking reaction chemistry, and how these factors have affected modelling approaches. A brief overview of how vaporisation and catalyst deactivation are addressed in the FCC modelling literature is also undertaken. Modelling of constitutive parts that are important to the FCC riser unit such as gas-solid cyclones, disengaging and stripping vessels, is also considered. This review then identifies areas where current models for the riser can be improved for the future. In Part II, a similar review is presented for the FCC regenerator system.

The Effects of Vaporisation Models on the FCC Riser Reactor

“…Therefore, further changes in temperature, coke concentration, and catalyst activity are minimal, as shown in the figures. The exit coke on catalyst concentration is predicted to be 0.55 wt%, which is within the normal range reported in the literature [5,52]. The exit temperature is ∼ 760 K, indicating a catalyst temperature drop of ∼ 200 K. Comparison of the catalyst temperature drop with previous work is not straight forward because of the disparities in the operating conditions, kinetic parameters, and physical properties of the phase mixtures.…”

“…Models have been used for optimisation of the unit, to design controllers for the unit, and in critical hazard analysis [4]. We showed in a recent review [5] that the modelling of the reactive multiphase flow occurring in the FCC riser involves three main features: the modelling of the vaporisation phenomena in the inlet region of the riser, kinetic modelling to describe the reactions and reaction rates, and hydrodynamic modelling to describe the flow field and pressure drop.…”

“…One of the earliest applications of this technique for catalytic cracking was by Weekman Jr and Nace [8], which considered three lumps, where the reaction mixture was characterised into the distillation cuts of gas oil feed, gasoline, and 'coke + gas'. As analytical and computational technology improved in the subsequent years, researchers managed to build upon the work of Weekman Jr and Nace [8] to develop more detailed lumped kinetic models for catalytic cracking [9][10][11][12][13][14][15][16][17] (see also reviews by [5,7,18] for summaries of lumped kinetic models published in the literature). As a result of the simplicity of this approach, it has become the most common kinetic modelling approach in the FCC riser modelling literature.…”

A Review of Catalyst Modification and Process Factors in the Production of Light Olefins from Direct Crude Oil Catalytic Cracking

“…In the kinetic equations, the catalyst deactivation can be accounted for using the deactivation function. The catalyst deactivation function, φ, is defined by Equation (1) [66][67][68][69]. The ratio of deactivation rate to that of a fresh catalyst is shown in Equation ( 2), while the rate of disappearance or formation of any lump is given by Equation (3).…”

Elements of the Manufacture and Properties of Technical Catalysts

“…Therefore, modeling it by the application of the equations of change encompasses trying to numerically solve a system of nonlinear partial differential equations coupling the description of the fluid flow and of the physicochemical transformation of the solid catalyst bodies. Although there have been important advances in modeling reactors such as FCC − and in multiscale modeling of catalytic processes, − this subject still remains to be scrutinized.…”