The Effect of Environmental Conditions on The Absorption of Carbon Dioxide Using Soda Lime

The removal of Carbon Dioxide (CO₂) from the atmosphere of a Royal Naval submarine should it suffer a distressed submarine (DISSUB) condition would be achieved by the use of canisters containing soda lime. The canisters are fitted to an absorption unit where air is drawn through the canister by the means of an electrically powered fan and is thus an “active” system.

A recent review of laboratory trials data has indicated that when operated at either low temperature or high ambient pressure there is a reduction in the useful CO₂ absorption rate and capacity of the canister. The loss of absorptive capacity reduces the time available for effective atmosphere purification and could lead to the submarine crew being forced to escape earlier than anticipated.

To allow an accurate prediction of the canisters absorption capacity and effective duration in realistic DISSUB scenarios more data was required. To gain this information the Deep Trials Unit (DTU) operated by QinetiQ at Alverstoke was used as a scale model to simulate the escape compartment of a submarine. The use of this facility allowed the canister performance to be determined at the extremes of temperature and pressure likely to be encountered in a DISSUB.

This paper discusses:

• (a)
  The current methods of CO₂ removal used in various navies.
• (b)
  The data obtained from previous and the DTU scale model trials.
• (c)
  A comparison of the use of Lithium Hydroxide as a CO₂ absorbent under the same environmental conditions.
• (d)
  Alternative methods of CO₂ absorption for DISSUB conditions.