- Raschig ring
Raschig rings are pieces of tube (approximately equal in length and diameter) used in large numbers as a
packed bed within columns for distillations and otherchemical engineering processes. They are usually ceramic or metal and provide a large surface area within the volume of the column for interaction between liquid and gas or vapour. Raschig rings are named after their inventor, the German chemistFriedrich Raschig .A. Sella (2008) Chemistry World vol 5 no 9 page 83 "Raschig's Rings"]They form what is now known as random packing, and enabled Raschig to perform distillations of much greater efficiency than his competitors using
fractional distillation columns with trays.In a distillation column, the
reflux or condensed vapour runs down the column, covering the surfaces of the rings, while vapour from thereboiler goes up the column. As the vapour and liquid pass each other countercurrently in a small space, they tend towards equilibrium. Thus less volatile material tends to go downwards, more volatile material upwards.They are also used for devices where gas and liquid are put in contact for purposes of gas absorption, stripping or chemical reaction, and as a support for
biofilm s in biological reactors.Raschig rings made from
borosilicate glass are sometimes employed in the handling of nuclear materials, where they are used inside vessels and tanks containing solutions of fissile material, for example solutions of enricheduranyl nitrate , acting as neutron absorbers and preventing a potentialcriticality accident . [ [http://www.orau.org/ptp/collection/Miscellaneous/raschigrings.htm Oak Ridge Associated Universities] Raschig Rings for Criticality Control (1980s)]ee also
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Fractionating column References
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