Three-Dimensional Hydrodynamics and Reaction Kinetics Analysis in FCC Riser Reactors

Abstract

Fluid catalytic cracking (FCC) is the refinery process for the conversion of high molecular-weight hydrocarbons to produce higher valuable products such as gasoline. The optimization of FCC process is challenging due to the complex interactions between a large number of dependent and independent parameters. One of the most uncertain aspects of a fluid catalytic cracking (FCC) unit is the description of fluid-solid mixing at the riser entrance. Most of the existing models assume an instant mixing of solids and gaseous reactants. However, a finite mixing length at the bottom of the riser may have a pronounced effect on the FCC operation, particularly, when very short residence times are allowed in the current commercial FCC risers. A good solid-fluid mixing is essential to ensure a complete feed vaporization which is important for several reasons including assuring a thorough catalyst to oil contact and minimizing coke deposition. In this study, the Eulerian-Eulerian multiphase flow and the 3-lump kinetic models were used to simulate the hydrodynamics and cracking reactions occurring in the FCC riser reactors. The model demonstrated the capability of commercial CFD code FLUENT 6.2 to describe the flow field in the riser reactor. The model also takes into account the temperature, the heat of reactions and gasoline distribution along the riser height.

Efficient Total Synthesis of Marine Alkaloid (−)‐Nakadomarin A

“…From Figure 10a, it can be decided that the solids volume fraction rises near the wall and annular flow is observed as in Das et al 3 As seen in Figure 10b, the solids velocity is found to increase over the riser height. This is a consequence of, (i) the cracking of the heavy gas oil into low molecular weight components such as gasoline, LPG, and dry gas, 29, 30, 31 (ii) a higher annular region thickness (see Figure 10b) in the top section of the riser decreasing the effective flow area significantly, and (iii) the gas‐phase pressure in the top section of the riser being lower than the bottom value due to the hydrostatic head of the solid. A low‐pressure in the top section of the riser increases the velocity of the gas phase when compared with the velocity of the gas phase in the bottom section of the riser.…”

Modelling and simulation of an industrial riser in fluid catalytic cracking process

“…Table 4 summarizes the parameters used in this simulation and were obtained from industry and literature. (Han and Chung, 2001b, Nuhu et al, 2012, Ahari et al, 2008 Variable…”

“…The riser unit has many sections; feed preheater, the vaporization section and the riser, which are sometimes modelled differently. Although an attempt to simulate the riser unit with varied diameter (between 1 m at the bottom to 1.4 m at the top) was made (Novia et al, 2007), only a quarter of the riser was considered because they modelled the riser unit in two sections; the vaporization section (found to have no chemical reactions) as 1 m diameter and the riser section as 1.4 m, a uniform cross section. They also included the vaporization section in the riser unit model.…”

A Computational fluid dynamics (CFD) comparison of 3-Lump and 4-Lump kinetic models for predicting gasoline, light gases and coke yield in fluid catalytic cracking (FCC) riser

“…Kinetic data for cracking reactions are shown in Table 1. The reaction kinetics is merged into the mathematical model by solving the species equations of the components in the form of chemical reaction rates [18]. Equations ( 21)-( 23) are used to describe the reaction kinetics of 3-lump kinetic model:…”