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Hydrodynamics Modelling and Catalytic Reactions of Multiphase Reactors at Extreme Conditions

Supervisor & ResearcherPost-docs:
jamal sherif amin
Graduate Students:
el mahdi IMG_9944  

Owing to the shortage of traditional resources and stringent environmental constraints, the feedstocks of several industrial processes are rapidly changing. The intrinsic variability of the feedstocks combined with social needs make many industrial processes much more difficult to design and operate. Scrutinizing the hydrodynamics and catalytic reactions of multiphase processes under conditions applicable to a broad range of technologies would lead at providing valuable insights into how the variation of operating condition can modify the reactor’s hydrodynamics and, in turn, its performance. The knowledge achieved from these studies, consequently, will help in the development of new processes and/or in the improvement of the existing ones to be aligned with the current and future needs.

In this regard, a research project includes three integrated research themes (turbulent fluidized beds reactor, slurry bubble column reactor, and catalytic reactions of multiphase reactors) have been tailored to the industrial needs. The industrial partner of this research project is TOTAL American Services, Inc. Two pilot-scale reactors have been built to carry out the experimental work (1) a gas-solid fluidized bed (I.D.=15 cm, H=4 m, P=0.1 to 3 MPa, T=20 °C to 1190 °C), and (2) a slurry bubble column (I.D.=15 cm, H=4 m, P=0.1 to 3 M Pa, T=20°C to 250°C).

Total Graphical abstract 1_ Pilot scale fluidized bed reactor







Hydrodynamics of a Gas-Solid Fluidized Bed at Elevated Pressures and Temperatures

Jaber Shabanian
Gas-solid fluidized beds are widely adapted in chemical processes operated at moderate to high pressure and temperature. The hydrodynamics of fluidized beds at elevated pressures and temperatures directly affects the transfer phenomena and reaction rates in the bed and, hence, is a critical factor for their design and operation. Nevertheless, the present understanding is far from satisfactory due to the lack of insight about the relative importance of interparticle forces and hydrodynamic forces. Attention to the fluidization characteristics of high pressure and temperature gas-solid fluidized bed reactors is essential since they will find many additional applications in the near future that will coincide with the rarefaction of conventional resources. The objective of the present study is to explore the fluidization behavior of different particles, covering Geldart groups A, B, and D powders, referred to the fluidization behavior at ambient conditions, at different operating conditions. The operating pressure and temperature will vary in the range of 1–20 bar and 25–900oC, respectively. The fluidization study will be attempted at different superficial gas velocities covering the fixed bed state, bubbling, and turbulent fluidization regimes. Different reliable and accurate measurement techniques/approaches, i.e., pressure transducers, an optical fiber probe, and the gas residence time distribution measurement, will be employed for the purpose of a comprehensive hydrodynamic study from both global and local points of view.
Measurement of Simple Hydrodynamic Parameters in a Gas-Solid Fluidized-Bed at Elevated Pressures and Temperatures
Navid Elahipanah

Gas-Solid fluidized beds are widely applied in chemical processing industry due to high contact surface, good mixing quality and high heat transfer capabilities.

It is found that operating the fluidized beds at elevated pressures improves the quality of fluidization. Also, high temperature is needed in fluidization units, such as combustors and cracking units. Change in the fluidizing gas properties, namely gas density and viscosity, is mostly responsible for the change in the bed behavior at extreme conditions, i.e., high pressure and temperature, which is defined by the effect of hydrodynamic forces (HDFs). At high temperature, interparticle forces (IPFs) also play an important role in determination of fluidization characteristics.

Available hydrodynamic based models and/or correlations are not adequately predicting the bed hydrodynamics at extreme conditions. So, the level of IPFs at different temperatures should be measured and a new correlations to predict simple hydrodynamic parameters, namely Umf and Uc, should be developed.

A pilot scale fluidized bed, 15 cm ID and 4.75 m height, capable of operating at pressures up to 30 atm and temperatures as high as 900 ˚C is being used in this study and the hydrodynamic parameters is being measured through analyzing the absolute and differential pressure signals in both time (mean value and standard deviation) and frequency domains (power spectral density analysis (PSD)).

This study will highlight the effect of extreme operating conditions, i.e., high temperature, on the fluidization transition velocities at different fluidization states, which is essential for a reliable design and scale up of such a gas-solid fluidized bed.


Hydrodynamics of Bubble Column Reactors Operating with Non-Newtonian Liquids at High-Pressure (HP) and High-Temperature (HT) Conditions

Amin Esmaeili
Although different types of reactors are used as multiphase contactors, the bubble column reactors received much attention from both academic and industrial interests during the past decade. The bubble column reactors offer high rates of heat and mass transfer, less maintenance cost, and feasibility for large production capacity. 

The design and scale-up of a bubble column reactor needs a complete understanding of its complex hydrodynamic behaviour, which is influenced by the physical properties of the phases, the operating variables and the design parameters. In recent years, viscous liquids (Newtonian and non-Newtonian) are being used for carrying out chemical reaction in bubble column reactors in many processes at HP and HT conditions. 

Although there has been an increasing interest in using non-Newtonian liquids in bubble column reactors, knowledge of the effects of the non-Newtonian flow behaviour on the hydrodynamics of bubble columns is limited and extensive studies are still needed to elucidate the influence of these liquids on the performance of bubble columns. 

To fulfill this essential need, the effects of different non-Newtonian liquids on the hydrodynamics of bubble columns is being investigated in two pilot-scale bubble column reactors with different geometries operating in both ambient and HP-HT conditions under the framework of the TOTAL research chair on multiphase reactors operating at extreme conditions.

Amin - A schematic diagram of the pilot-scale bubble column reactor operating at high pressure and high temperature conditions

Hydrodynamics and mass transfer of slurry bubble column reactors at high pressure and high temperature
El Mahdi Lakhdissi

Slurry  bubble  columns  reactors  have  many applications  in  chemical,  biochemical  and petrochemical  industries.  They are known by their advantages during operation and maintenance such as high heat and mass transfer and low operating costs which make them more efficient comparing to the other multiphase reactors.

However,  a  better  understanding  of  the  hydrodynamics  aspects  and  mass  transfer coefficients  that  affect  significantly  the  performance  of  those  reactors  are  not  well understood especially in the presence of solid particles.

Also,  almost  all  the  previous  work  were  carried  out  in  ambient  conditions  regarding pressure and temperature or just treated high pressure or high temperature separately.

The presence of solid is also poorly understood because various authors tried to understand the impact of solids in terms of macroscopic quantities such as the apparent viscosity of the liquid phase.  However,  only  few  studies  were  concerned  about  the  effect  of  the hydrophilicity/ hydrophobicity of the catalyst on bubble coalescence and breakage within the  column.  In  addition,  there  are  many  discrepancies  in  term  of  the  mechanisms  that explain the solid particles impact.

This work will be mainly concerned about the investigation of the hydrodynamics such as gas holdup, bubble rise velocity, bubble chord length and bubble size distribution and also mass transfer aspects such as the volumetric liquid-side mass transfer coefficient of slurry bubble columns at high pressure (up to 30 bars), high temperature (up to 220C) and low solid concentrations (up to 10%).

Development of a multiscale model for the simulation of mass transfer in gas/liquid bubble columns
Remi Demol
Bubble columns reactors (BCRs) are widely used in chemical, petrochemical, pharmaceutical and biochemical industries. These multiphase reactors are found in many processes using chemical or biochemical reactions between a gas phase, as bubbles, and a liquid phase located in the column. A third solid phase, suspended in the liquid phase, can be added to catalyze the reaction. Bubble columns have very good mass and heat transfer properties. Nevertheless, the scale up step is a difficult task. Maintain mixing conditions and similar hydrodynamic properties is not easy. Many studies have been made to estimate hydrodynamics parameters and get correlations.I am investigating the ways to create a multiscale model that describes as well as possible the mass transfer. Then, this work could give access to local values instead of average values on the whole column. For example, the volumetric mass transfer coefficient (kLa) which is, in fact, the product of two parameters: the liquid side mass transfer kL and the specific gas-liquid interfacial area a. I am working with OpenFOAM to run these simulations. This work could be useful to find news scale-up rules.