Application of Magnetic Resonance Imaging (MRI) to Determine the Influence of Fluid Dynamics on Desulfurization in Bench Scale Reactors

Abstract

The influence of fluid dynamics on the hydrodesulfurization (HDS) reactions of a diesel oil in bench-scale reactors was evaluated. The porosities and liquid saturations of catalyst beds were quantified by using the MRI technique. The gasliquid systems used in the experiments were nitrogen diesel and hydrogen diesel. An apparatus was especially constructed, allowing in situ measurements of gas and liquid distributions in packed beds at elevated pressure and temperature up to 20 bar and 200°C, respectively. The reactor itself had a length of 500 mm and an internal diameter of 19 mm. The packed beds used in this MRI study consisted of: (1) 2 mm diameter nonporous spherical glass beads and (2) 1.3 mm diameter porous Al 2 O 3 trilobes having the same size as the original trilobe catalyst used in HDS bench-scale experiments. The superficial gas and liquid velocities were set within the range of trickle flow, e.g., u 0G = 20-500 mm/s and u 0L = 0.1-6 mm/s. In parallel with the MRI experiments, the hydrodesulfurization of a gas oil was investigated in a bench-scale plant. Its reactor had the same dimensions of the trickle-bed column used in the MRI experiments and was filled with original trilobe catalyst. These catalytic experiments were carried out at a wide range of operating conditions (p = 30-80 bar, T = 300-380°C, LHSV = 1-4 h -1 ). The results of both fluid dynamic and catalytic reaction experiments were then combined for developing a simulation model to predict the HDS performance by accounting for fluid dynamic nonidealities.

Modification of Ergun equation for application in trickle bed reactors randomly packed with trilobe particles using computational fluid dynamics technique

“…Lebigue et al [11] investigated empirically the effect of particle shape on wetting efficiency. Nguyen et al [12] used magnetic resonance imaging (MRI) to determine the effect of fluid dynamics on hydrodesulfurization (HDS) reactions of diesel oil in bench scale reactors. They also quantified the porosities and liquid saturations of trilobe particles catalyst beds.…”

Magnetic Resonance Imaging and Velocity Mapping in Chemical Engineering Applications

“…Such measurements give insight to how flow within fixed beds should be modelled, as well as how particle sizes, shape and packing method influence hydrodynamics. More recently, MR has been used to image the gas-liquid distribution in a fixed bed as a function of temperature and suggest how these data may be used to gain greater understanding of the influence of hydrodynamics on desulfurization in bench-scale reactors (105).…”

T1 Relaxation of Methane in Mixtures with Gaseous Water

“…With MRI, in situ and operando measurements of the reacting zone inside the opaque reactor can be performed. Different MRI techniques offer solutions to spatially map process parameters like velocities, , mass transport, temperature, − and species distributions. − All techniques have in common the fact that they make use of nuclear magnetic resonance, a phenomenon that can be utilized by applying radio frequency (RF) pulses to a specimen located in a strong magnetic field. The characteristic longitudinal ( T 1 ) and transverse ( T 2 ) relaxation times play an important role in all MRI applications, as they determine how the measured signal evolves over time and how much of the signal is still available after some time.…”