A Study into the Potential Use of Photocatalysis for Atmosphere Treatment in Submarines 2004-01-2334
Nuclear submarines may remain at sea submerged for weeks or months at a time and a range of equipment is provided aboard to purify and re-vitalise the air in order to maintain a viable atmosphere for the crew to breathe over extended periods. Activated carbon beds are used to remove ppm-level organic contaminants that build up in the atmosphere from, for example, lubricants and the outgassing of materials of construction. These carbon beds require frequent replacement and present a substantial logistic demand. The beds also constitute an increased fire hazard as the amount of adsorbed material builds up.
Photocatalysis is a process whereby a semiconductor catalyst material, typically titanium dioxide (TiO2), is irradiated in air with ultraviolet (UV) light. This produces high-energy hydroxyl radicals that are capable of completely oxidising a range of molecules to simple, relatively non-toxic, species. For instance, hydrocarbons are generally oxidised to water and carbon dioxide. Quantitative oxidation of contaminants by such a process would obviate the need for the current carbon absorption beds .
The bench scale work described in this paper looked at a number of aspects of system design. These aspects included catalyst density, UV wavelength and reactor geometry. The effects of these parameter variations on the observed performance of the process for oxidation of the target compounds are presented.