Metal & Plastic Pall Ring Packing

Friedrich Raschig, a German chemist, first invented Raschig ring packing as a way to perform efficient distillation. Raschig rings are cylindrical tubes that have equal height and diameter. They’re typically made of metal or ceramic, though glass is also used in some applications. When used for distillation, vapor will condense on the ring’s surfaces. While the vapor and liquid pass each other in the small space, they try to achieve equilibrium. As a result, the material that is harder to evaporate goes downward in the tube, and the easily evaporable material goes upward.

The Raschig ring is considered the first generation of ring packing, and since its invention, the ring design has been altered to be more efficient and handle higher capacities. The pall ring was a significant advancement for random packing. Pall rings are similar to Raschig rings in that they have equal height and diameter. The significant difference between the two is that pall rings have windows and tabs punched in the walls. Most commonly pall rings are made of metal, ceramic or plastic, depending on the conditions of the application.

Adding the windows and tabs increased the capacity and efficiency of the ring significantly, as the gas and liquid distribution is improved. The tabs being folded into the center of the tube creates drop points, allowing more internal surface area to be used. This improved packing design is flexible, has low resistance and high separation capabilities.