Raschig Rings

Raschig rings are tube fragments that are almost same in length and diameter, employed in large numbers as a packed bed within the columns for distillations and certain chemical engineering processes. They are made up or ceramic or kind of a metal that offer a large surface inside the volume of the column for interaction between liquid and gas or vapor. Raschig rings have been named after the German chemist Friedrich Raschig who invented these.

The extensive usage

In the modern terms random packing is formed through them. In a distillation column, the reflux or condensed vapor runs down the column, covering the surfaces of the rings, while vapor from the re-boiler goes up the column. When the vapor and liquid cross each other simultaneously in a tiny space there seems a balance. Thus less volatile material is likely to go below and more volatile material upwards. Raschig rings are extensively used in such devices where gas and liquid are put in contact for intentions of gas absorption, stripping or chemical reaction and as a hold up for bio-films in biological factors.

Prevention of potential criticality accident

These rings are made from borosilicate that are sometimes used in the usage of nuclear materials and inside vessels and tanks comprising solutions of fissile material, for instance solutions of enriched uranyl nitrate acting as neutron absorbers and preventing a potential criticality accident. Metal raschig rings are employed in particular applications demanding good corrosion and thermal transfer. They are commonly thicker than other random packing kinds and provide high durability and lower efficiency than other random packing kinds. This durable design withstands crushing strength and long life used often inside the refinery and gas processing industries.

Good corrosion and thermal shock control

These rings are available in different sizes according to the demand such as 25, 38 and 50. Those rings made from special carbon or graphite is employed in applications requiring good corrosion and thermal shock control. And these are highly resistant to most acids, alkalis and solvents at temperatures as high as 150 dec.

But the ones most generally used in regular packing are still used for refilling existing columns and other applications. Its surface ratio is higher than ceramic cylinders and balls by 30% and its ring shape has high mechanical stability. The first generation raschig rings are usually made from the metals like carbon steel or very high alloys like Monel 400 or Hastelloy c276.

Questions:

• What are raschig rings?
• What are the uses of raschig rings in chemical engineering?