![]() ![]() ![]() 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.A nuclear, biological, chemical (NBC) canister was indigenously developed using active carbon impregnated with ammoniacal salts of copper (II), chromium (VI) and silver (I),and high efficiency particulate aerosol filter media. 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. The procedure is based on two well-known empirical models: Wheeler-Jonas and Yoon-Nelson equations. 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. 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. However, the pollutants’ concentrations that typically encounter in indoor environment are very low thus increasing the influence of humidity on the filter performance. Predicting the breakthrough time of filters is necessary for scheduling their maintenance and/or regeneration. Adsorption-based granular activated carbon (GAC) filters are commonly being used to purify indoor air by removing indoor air pollutants. Indoor air quality (IAQ) is a major concern in non-industrial buildings since it influences occupants’ health, comfort and productivity. The considerable advantage of the model is that using a single-fitting parameter allows experimental data to be approximated with a satisfactory accuracy The complete mixed-diffusion model adequately reflects the influence of the contributions of axial dispersion and external and internal mass transfer in the smearing of the sorption front, but diversions from the assumptions of the model that manifest themselves in the concentration dependence of an apparent internal-diffusion coefficient are also observed in this case. It is shown that a simplified version of the mixed-diffusion model in which the influence of axial dispersion is neglected and the establishment of equilibrium on the external boundary of a grain is assumed gives distorted knowledge of the real dynamics of the process. ![]() The V2O5/Al2O3 system is used as an example. The use of the mixed-diffusion model for calculating the dynamics of adsorption of the vapors of volatile organic compounds in a fixed bed of a porous adsorbent is considered. The influencing parameters were either adapted from the literature or derived from mass balances to be the slope of adsorption isotherm and surface diffusion. Considering the big discrepancies of predicted and measured breakthrough curves at low concentrations using pore diffusion model and homogeneous-solid diffusion model, this suggests that the lifetime estimation of the filter is still questionable. A sensitivity analysis of models’ parameters showed that the effective diffusivity has strong dependence on the concentration which is more noticeable for pore surface diffusion model. This paper gives an overview of the existing models of sorbent-based gas filters and compares their capability to predict the filter performance over its life time. To guide the selection, design and maintenance of adsorptive filters for residential and office buildings, it is necessary to validate the available mass transfer-based models for the indoor air concentrations. Adsorption based air cleaning technologies have long been employed in various industrial applications. ![]()
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