Ozone is the criteria pollutant with respect to oxidizing gases to be tested in ASHRAE Standard 145.2-2011. In non-industrial buildings, ozone is normally removed by activated carbon (AC). In practice, how often the filters should be replaced is a key question. The Wheeler-Jonas equation (WJE) is widely used for describing breakthrough curves of organic vapours removal by AC. Some studies reported the WJE is also applicable of some inorganic gases including the acid gas - chlorine and the basic gas - ammonia.This paper firstly investigated applicability of the WJE of an oxidizing gas - ozone. The experiments were conducted on a well-designed bench-scale test rig. The results indicated that the WJE does not work for ozone.There are two assumptions associating with the WJE, constant adsorption kinetics and neglecting axial diffusion. Multiple ozone-AC reaction mechanisms combined with different reactivities were confirmed from the literature review, which indicate the assumed constant adsorption kinetics is improper for ozone-AC reacitons.Finally, a new mass balance model described by a partial differential equation (PDE) which introduces the axial diffusion term and first order kinetics accompanied by exponential deactivation was proposed. The PDE solution is in good agreement with the experimental data. The Péclet number was calculated with the estimated axial diffusion coefficient from the PDE model. The large value indicates the axial diffusion is not significant. Therefore, the constant adsorption kinetics assumed in the WJE is considered to be the major reason of its inapplicability of ozone.
Citation: 2016 Winter Conference, Orlando, FL, Conference Papers