Quantification and application of skew of breakthrough curves for gases and vapors eluting from activated carbon beds

Vapor and gas breakthrough curves for packed activated carbon beds are often assumed to be symmetrical, when they are actually more often skewed. This skew explains why adsorption rate coefficients calculated at differing breakthrough fractions may not agree. Three extensive databases of breakthrough curves were analyzed to quantify this skew and the effects of relative humidity (preconditioning and use) on it. Skew results for varieties of chemicals and carbons agreed well and were combined to get a quadratic expression for a defined skew parameter. This expression was combined with a previous observation of the effect of breakthrough fraction on calculated rate coefficient. The combination allows estimation of an adsorption rate coefficient at a desired breakthrough fraction from a rate coefficient known (experimentally or by calculation) at another breakthrough fraction. A sample calculation is given.