Dixon rings

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

Packed columns

Packed columns are used in a range of industries to allow intimate contact between two immiscible fluids which can be liquid/liquid or liquid/gas. The fluids are passed through in a counter current flow through a column.[1][2]

Random column packing

Random column packing used to characterize the maximum volume fraction of a solid object obtained when they are packed randomly. This method of packing has been used since the early 1820s; the types of packing used were originally made out of glass spheres. However, in 1850 they were replaced by a more porous pumice stone and pieces of coke.[3][4]

In the early 20th century Friedrich Raschig realized the importance of a high void fraction and having the internal surface of the packing media take part in the mass transfer. He designed the Raschig ring, which was more effective than previous forms of random packing and became very popular. Raschig rings are usually built from ceramic or metal and provided a large surface area within the column for interaction between liquid and gas vapors.[4][5]

The development of the Dixon ring

In 1946 Dr Olaf Dixon developed a new product for column distillation. Based on the design of the Lessing ring, Dixon developed the Dixon ring, employing a stainless steel mesh to improve the pressure drop of the packed column.[6]

Application

Dixon rings

Dixon rings are used for many applications, including:

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 .[10][8][6][11][12]

Table showing the Physical Properties of Dixon rings
PropertyRing Size
1/16"1/8"1/4"
Surface area 35502378900
Void space%94.6390.9890.73
Number per litre102,00024,4002,965

See also

Random column packing

References

  1. ↑ Alford, Robert; Burns, Mark; Burns, Neil (2011). "Dixon Rings - A Revolutionary Random Column Packing" (PDF). Filtration. 11 (4).
  2. ↑ Striegel, André M. (2011-09-07). "Hydrodynamic chromatography: packed columns, multiple detectors, and microcapillaries". Analytical and Bioanalytical Chemistry. 402 (1): 77–81. doi:10.1007/s00216-011-5334-3. ISSN 1618-2642.
  3. ↑ "Random Packing". www.amacs.com. Amacs Process Towers Internals. Retrieved 2018-07-20.
  4. 1 2 Carl,, Schaschke,. A dictionary of chemical engineering (First ed.). Oxford. ISBN 0191002690. OCLC 870517909.
  5. ↑ "Ceramic Raschig Ring Packings". Lian Chuang. Retrieved 19 July 2018.
  6. 1 2 "Dixon Ring". www.laiko.net. Retrieved 2018-07-20.
  7. ↑ Kolaczkowski, Stan; Awdry, S.; Le, C.D.; Nuckols, M.L.; Smith, T.; Thomas, D. (11 May 2015). "Removal of CO2 from a submersible atmosphere by scrubbing with water: Experiments in a single column". Chemical Engineering Research & Design. 100: 157–169. doi:10.1016/j.cherd.2015.04.035.
  8. 1 2 "1948 technology could help today's submariners breathe easier". newatlas.com. Retrieved 2018-07-20.
  9. ↑ Wilson, J.A.; Smith, W. (1979). "Dynamic modelling of countercurrent mass transfer processes". Transactions of the Institute of Measurement and Control. 1 (37). doi:10.1177/014233127900100105.
  10. 1 2 Kaba, Akira; Akai, Reijiro; Yamamoto, Ichiro; Kanagawa, Akira (October 1988). "Measurement of HETP of SUS Dixon Ring and Porcelain Packing in Small-Scale Water Distillation Column for H20-HTO Isotope Separation". Nuclear Science and Technology. 25 (10): 69–74.
  11. ↑ Sheng, Miaopeng; Liu, Chenguang; Ge, Chunyuan; Arowo, Moses; Xiang, Yang; Sun, Baochang; Chu, Guangwen; Zou, Haikui (2016). "Mass-Transfer Performance of CO2 Absorption with Aqueous Diethylenetriamine-Based Solutions in a Packed Column with Dixon Rings". Industrial & Engineering Chemistry Research. 55 (40): 10788–10793. doi:10.1021/acs.iecr.6b02280.
  12. ↑ Jin, Yanchao; Hu, Runzhi; Wang, Yiping; Cui, Yong; Liu, Yun; Huang, Qunwu (2017). "The effect of Dixon rings on direct contact heat transfer performance: Comparison of counter and co-current evaporation". Applied Thermal Engineering. 117: 762–772. doi:10.1016/j.applthermaleng.2017.02.054. ISSN 1359-4311.
This article is issued from Wikipedia. The text is licensed under Creative Commons - Attribution - Sharealike. Additional terms may apply for the media files.