Comparative Study of Different Two-Phase Models for the Propane Oxidative Dehydrogenation in a Bubbling Fluidized Bed Containing the VO_x/γ-Al₂O₃ Catalyst

Abstract

The modeling of oxidative dehydrogenation of propane over the VO x /γ-Al2O3 catalyst in a bubbling fluidized bed was studied. The performance of the fluidized bed reactor was studied by using three different fluidization models with different hydrodynamic assumptions: simple two-phase (STP) model, dynamic two-phase (DTP) model, and El-Halwagi and El-Rifai [simplified Halwagi (SH)] model. The models were validated using previously published experimental data. The effects of temperature, gas velocity, propane and oxygen concentration and bed height on propane conversion, product selectivity, and propylene yield were investigated and discussed. The obtained results indicated that the SH model under-predicted the propane conversion. The STP model with simplified hydrodynamic assumptions was only suitable when reaction temperature was low. The DTP model considering dynamically distribution of gas and solid could predict propane conversion and propylene selectivity with average relative errors of 16 and 2.5%, respectively, over a wide range of experimental data, which were more accurate than those of the STP and SH models.

Kinetics, Mass Transfer, and Reactor Scaling Up in Production of Direct Dimethyl Ether

“…The two-phase model is widely used for modeling a bubbling fluidized bed. , A bubbling fluidized bed reactor contains a bubble phase of solid-free region and an emulsion phase of solid and gas. , Mass transfer occurs between the bubble and emulsion phases. The mass transfer parameter is essential for the two-phase model of fluidized bed reactors and is rarely available.…”

“…The two-phase model has been modified to become a dynamic two-phase model. 28,29 The dynamic twophase model requires more complex hydrodynamic parameters, such as the velocity of the emulsion phase and nonuniform catalyst volume fraction in the emulsion phase. 28,29 The basic two-phase model is still useful for simplifying the calculations of multiple reaction systems with complex reaction rate forms.…”

“…According to the two-phase model widely applied for modeling a bubbling fluidized bed, the bubble phase gas is assumed to be in plug flow, while the emulsion phase gas is in mixed flow. The two-phase model has been applied to predict the performance of bubbling fluidized bed reactors for various types of gas–solid catalyzed reactions, such as methanol synthesis and oxidative dehydrogenation of propane . Khraibet et al proposed a model similar to the two-phase model.…”

“…In the bubble phase, they used a compartment model instead of a plug flow model to predict axial variation of species concentration. The two-phase model has been modified to become a dynamic two-phase model. , The dynamic two-phase model requires more complex hydrodynamic parameters, such as the velocity of the emulsion phase and nonuniform catalyst volume fraction in the emulsion phase. , The basic two-phase model is still useful for simplifying the calculations of multiple reaction systems with complex reaction rate forms. In modeling a bubbling fluidized bed reactor for DME production using the two-phase model reactor, plug flow behavior of gas enhances the three consecutive reactions involved in DME synthesis from syngas, while a mixed flow in the emulsion phase enhances heat transfer of the exothermic reactions.…”

Modeling Fischer–Tropsch to Olefins in Pilot Slurry Process with a Method of Multiscale Bubbles Hybrid Injection

“…The direct production of olefins from syngas by the Fischer–Tropsch (F–T) synthesis effectively converts coal, natural gas, and biomass resources into olefins. , The development of commercial industrialization has allowed the use of the various multiphase reactors, − in particular with the slurry bubble column reactors (SBCRs) for strong exothermic Fischer–Tropsch to olefin (FTO) processes owing to the simple construction and operation, as well as efficient mixing, heat, mass transfer, and reaction ability. , Despite the simple system design, bubble columns are characterized by complex fluid dynamic interactions, especially for bubble dynamics. The bubble-induced agitation from the microscopic bubble scale to the macroscopic reactor scale strengthens turbulence, promotes mixing, and enhances heat, mass transfer, and multiphase reactions. − Mass transfer performance can be characterized by the volumetric mass transfer coefficient ( k l a ), where contributions of both mass transfer coefficient ( k l ) and interfacial area ( a ) can be considered.…”