Fluidized Bed System
Evaluating the role of air flow influencing fluidization within a packed bed system. An analysis of particle characteristics, pressure drops, and minimum fluidization velocities.
Interactive Slide Deck
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Introduction & Objectives
Our primary goal was to understand how variations in air flow impact the behavior of particles within a fluidized bed system. We utilized a vertical column packed with walnut and glass particles, equipped with a distributor plate at the base.
By gradually introducing air at increasing rates, we observed the transition from a tightly packed bed to a fluidized bed.
Key Properties & Measurements Evaluated:
- • Pressure drop
- • Airflow rate
- • Bed expansion (dx)
- • Fluid velocity (min)
- • Porosity
- • Sphericity
- • Density
- • Average particle size
Vertical column with walnut/glass particles]
Methodology
Our setup utilized standard protocols without major deviations. We employed Python programming (provided by the Chemical Engineering department) to calculate eccentricity, establishing that Sphericity = Eccentricity.
Governing Equations
Bernoulli's Equation
Simplified for flow through porous media:
ΔP = −𝜌ℑ
Blake-Kozeny (Kozeny-Carman)
This approximation of the friction term helped us relate pressure drop and friction.
Minimum Fluidization Velocity & Forces
Calculated based on bed properties and fluid dynamics.
Python script screenshot OR Force diagram]
Results & Analysis
We began by calculating density, sphericity, porosity, and average size. Using these relationships, we calculated the theoretical pressure drop and minimum fluidization velocity.
Experimental data was collected by running 3 trials for each bed and averaging the results. We varied the flow rate until we reached the fluidization point. Using the minimum fluidization velocity points, we measured the experimental pressure drop.
Observation: The theoretical and experimental data for the glass bead bed is fairly comparable. However, large discrepancies exist for the walnut bed. Given the limited data collected, the experimental data is considered more accurate in this case.
Glass Beads - Bed Displacement vs Fluid Velocity
Mark fluidization point with red arrow]
Walnut Bed - Bed Displacement vs Fluid Velocity
Mark fluidization point with red arrow]
Conclusions & Applications
Particle Characteristics Impact
The solid particle characteristics which most greatly affect minimum fluid velocity are:
- Sphericity: High in glass beads, lower in walnuts.
- Porosity: Higher in walnuts, lower in glass beads.
- Density: Higher in glass beads, lower in walnuts.
- Average particle size: More consistent in glass beads.
Industrial Applications
Fluidized beds are essential in numerous industrial processes, including fluidized bed reactors, solids separation, fluid catalytic cracking, fluidized bed combustion, and heat/mass transfer.
Example: Fluid catalytic cracking in the oil industry utilizes this technology to break down larger carbon chains into smaller hydrocarbons, such as the Fluid Bed Reactor at ExxonMobil’s Baton Rouge Refinery.
Fluid Bed Reactor (e.g., ExxonMobil)]