Gas-phase filters breakthrough models at low concentration – Effect of relative humidity

Publication date: May 2014
Source:Building and Environment, Volume 75
Author(s): Ali Khazraei Vizhemehr , Fariborz Haghighat , Chang-Seo Lee
Indoor air quality (IAQ) is a major concern in non-industrial buildings since it influences occupants' health, comfort and productivity. Adsorption-based granular activated carbon (GAC) filters are commonly being used to purify indoor air by removing indoor air pollutants. Predicting the breakthrough time of filters is necessary for scheduling their maintenance and/or regeneration. However, the pollutants' concentrations that typically encounter in indoor environment are very low thus increasing the influence of humidity on the filter performance. Also, the existing standard recommends the test to be carried out at 100 ppm, which is much higher than the actual volatile organic compounds (VOC) concentration in buildings. This paper reports the development of a framework for predicting the breakthrough curve of activated carbon filters at low concentration and different levels of relative humidity applying accelerated test data. The procedure is based on two well-known empirical models: Wheeler–Jonas and Yoon–Nelson equations. The overall mass transfer coefficient in the Wheeler–Jonas equation and the proportionality constant in the Yoon–Nelson equation (both as a function of adsorption capacity) are a function of humidity level. Results show that the proposed framework allows the breakthrough time at humid condition and low contaminant concentration to be estimated using the data obtained from the existing standard test procedure.