Raschig rings
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Raschig rings are referred to as random packing and are used in commercial fractional distillation columns to reduce pressure loss (versus using trays), while maintaining good efficiency and economy. Typically the delta p is lower than in case of trays but slightly higher than for structured packing.
Raschig rings are small tube cuttings providing a surface for (re)evaporation of the most volatile part in the refluxing distillate, typically 10 mm in diameter and 12 mm long. These can be made from metal, glass, or can be ceramic.
There are many other forms and shapes a random packing may assume. Raschig is a German company that invented the Raschig Ring but also offering numerous variants.
Raschig rings made of copper tube cuttings are superior at fractionating volatile hydrocarbons (or ethanol) mixed with water.
Due to recent advancements in structured packing the technical window where application of random packing is optimum is reduced significantly. Use typically limited to columns of very small diameter where structured packing is more difficult to fit in and the disadvantages of a lower efficiency and hence taller column have less economic impact.