Structured packing

The term structured packing refers to a range of specially designed materials for use in absorption and distillation columns. Structured packings typically consist of thin corrugated metal plates or gauzes arranged in a way that force fluids to take complicated paths through the column, thereby creating a large surface area for contact between different phases.

Structured packing is formed from corrugated sheets of perforated embossed metal, plastic, or wire gauze. The result is a very open honeycomb structure with inclined corrugations or flow channels, giving a relatively high surface area but with very low resistance to gas flow. The surface enhancements have been chosen to maximize liquid spreading. These characteristics tend to show significant performance benefits in low pressure and low irrigation rate applications. Steeper or larger corrugation angles lower the pressure drop at the cost of lower separation efficiencies. The sheets are packaged into elements that are piled up in alternating layers, forming a packed bed that fills the complete cross-sectional area of the fractionation tower. To fully utilize the separation efficiency, structured packings require a careful distribution of the liquid on top of the bed. For the packings to reach their highest efficiency the variation in the liquid distribution should be less than 1–2%. In high purity applications with many equilibrium stages, the packing needs to be installed in multiple packed beds, in between the liquid is collected and re-distributed anew.