Dixon rings are a form of random packing used in chemical processing. They consist of a stainless steel mesh formed into a ring with a central divider, and are intended to be packed randomly into a packed column. Dixon rings provide a large surface area and low pressure drop while maintaining a high mass transfer rate, making them useful for distillations and many other applications.

Background

The development of the Dixon ring

In 1943 Dr Olaf George Dixon of ICI applied for a patent of a new product for column distillation.^[1] He used stainless steel mesh instead of sheet steel in the Lessing ring in order to improve the pressure drop of the packed column (in fact, they were called "wire gauze Lessing rings" in a 1949 publication^[2]).

High performance was achieved between radioactive and non-radioactive materials,^[3] and despite high cost they are still used in the nuclear industry e. g. for water detritiation.^[4]

Application

Dixon rings

Dixon rings are used for mainly for laboratory distillation applications.

Performance principles

The enhanced performance of the Dixon ring is based on liquid surface tension: when the mesh is wet its surface area increases greatly, with an accompanying increase in the rate of mass transfer. Dixon rings require pre-wetting (flow of liquid over the packed bed prior to starting the reaction flow). While this increases batch processing startup time, the increased performance of the Dixon ring overcomes this.

^{[5] [6] [7]}

Table showing the physical properties of Dixon rings

Property	Ring size
	1⁄16"	1⁄8"	1⁄4"
Surface area ${\displaystyle m^{2}/m^{3}}$	3550	2378	900
Void space %	94.63	90.98	90.73
Number per litre	102,000	24,400	2,965

See also

• Random column packing
• Fenske helices

References