Geldartklassificeringen

The Geldart classification is a system used in powder technology to categorize solid particles based on their behavior when dispersed in a gas or liquid. It was developed by D. Geldart in the 1970s and is widely used in fields such as fluidization, pneumatic transport, and powder handling. The classification is based on two key parameters: the particle's size and its density, and how these relate to the properties of the fluidizing medium.

There are four main Geldart groups, denoted by the letters A, B, C, and D. Group A particles are typically small and have a density close to that of the fluidizing gas. They exhibit smooth fluidization and expand significantly upon aeration. Group B particles are larger than Group A and have a similar density. They tend to form bubbles that rise through the bed, leading to less uniform fluidization. Group C particles are very fine and light, often exhibiting electrostatic effects and forming channels rather than bubbling. Group D particles are large and dense, requiring high fluid velocities for any significant movement.

The Geldart classification helps engineers predict how a particular powder will behave in a fluidized bed or other fluid-particle systems. This prediction is crucial for designing and operating equipment efficiently and safely, as different particle groups require different operating conditions and equipment designs. For example, Group A powders are easier to fluidize than Group D powders. Understanding these characteristics allows for optimization of processes like drying, combustion, and chemical reactions involving powders.