Fluidized Bed Simulator
Interactive simulation of particle fluidization showing fixed bed, minimum fluidization, bubbling, and turbulent regimes
About this Simulator
A fluidized bed suspends solid particles using an upward flow of gas or liquid. As gas velocity increases, particles transition from a fixed packed bed to a fluidized state where they behave like a fluid. This simulator demonstrates the key regimes: fixed bed, minimum fluidization, bubbling, and turbulent fluidization.
Physics & Formulas
Minimum Fluidization Velocity (Ergun):
$$U_{mf} = \frac{d_p^2 (\rho_p - \rho_g) g}{150 \mu} \cdot \frac{\varepsilon_{mf}^3}{1 - \varepsilon_{mf}}$$
Pressure Drop (Fluidized):
$$\Delta P = (1 - \varepsilon) (\rho_p - \rho_g) g H$$
Geldart Classification (1973):
| Type | Name | Size | Behavior |
|---|---|---|---|
| C | Cohesive | <30 μm | Difficult to fluidize, particles stick together, channels form |
| A | Aeratable | 30-150 μm | Best fluidization, smooth expansion before bubbling (FCC catalysts) |
| B | Sand-like | 150-500 μm | Bubbles form immediately at Umf, most common (sand, glass beads) |
| D | Spoutable | >500 μm | Large bubbles, slugging, better for spouted beds (grains, coal) |
How to Use
- Start with gas velocity at zero - particles are in a fixed (packed) bed
- Slowly increase gas velocity using the slider
- Watch for minimum fluidization - particles just begin to suspend
- Continue increasing to see bubbles form and rise through the bed
- Try different Geldart types to see how particle properties affect behavior
- Observe the pressure drop curve - it plateaus after minimum fluidization
Frequently Asked Questions
What is minimum fluidization velocity?
The minimum gas velocity needed to suspend particles. Below this, the bed is fixed. Above it, particles float and the bed expands. The pressure drop equals the weight of particles per unit area.
What are Geldart particle types?
A classification based on particle size and density: Type A (20-100μm, aeratable, smooth fluidization), Type B (40-500μm, sand-like, immediate bubbling), Type C (<20μm, cohesive, difficult to fluidize), Type D (>600μm, spoutable, large bubbles).
Why do bubbles form?
When gas velocity exceeds Umf, excess gas forms voids (bubbles) that rise through the bed. This is called the bubbling fluidization regime. Bubbles promote mixing and heat transfer.
What are fluidized beds used for?
Catalytic cracking in refineries, combustion of coal and biomass, pharmaceutical coating, drying of grains, gasification, and many chemical reactions requiring good gas-solid contact.
