Fluidized beds are a commonly unit operation in the process industries. Their nature makes them particularly suitable venues for gas-solid catalyzed reaction, often in the petroleum industry to produce gasoline and other chenicals. They have also found use in the polymer industry, and bioreactors (in the form of liquid fluidized beds)

In 1952, Sabri Ergun derived the following equation to predict the pressure drop in packed beds.

- ΔP is the pressure drop
- L is the height of the bed
- D
_{p}is the particle diameter - ε is the porosity of the bed
- μ is the gas viscosity
- V
_{0}is the superficial velocity (the volumetric gas flowrate divided by the cross-sectional area of the bed) - ρ
_{g}is the gas density

The pressure drop required for minimum fluidization is given by

- ρ
_{p}is the particle density - ε
_{M}is the porosity of the bed at minimum fluidization

By comparing the pressure drop given by the Ergun equation to the pressure drop for minimum fluidization, you can calculate the superficial velocity necessary for fluidization. At this point, bubbles of gas form and rise through the bed. This increases the effective volume of the bed.

**Download Excel Spreadsheet to Calculate Ergun Equation**

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