(553d) Service Time of Activated Carbon Cartridges: Comparison of Wheeler-Jonas and Linear Driving Force at Constant Pattern Models

Estimation of service life of activated carbon cartridges used as air purifying respirators remains a problem due to several factors: enormous number of organic vapour molecules, diversity of activated carbons, difficulty of handling the relative humidity, diversity of norms varying from country to country? Large number of experiments as been performed by several teams around the world, especially the G.E. Wood's team at Los Alamos Laboratory, as measurements of breakthrough curves with special attention to the breakthrough point. To correlate the results of the breakthrough times and have a prediction of service live an equation based on a cartridge model is needed.

On the one hand the most popular and almost exclusive equation used is the Wheeler-Jonas equation which results from a model of breakthrough curve based on chemical reaction kinetics. The kinetic constant has been shown to depend on several parameters as flow rate, temperature, particle size, adsorption capacity, molecular weight of the adsorbate and an affinity coefficient.

On the other hand the linear driving force (LDF) model, a model of mass transfer inside the particle, is very used in the design of adsorbers. It is usually a part of system equations which is solved with numerical methods. A special case of application is to adsorption fronts having constant pattern behaviour that is the front shape remains as it propagates through the bed. The LDF model at constant pattern (LDFCP) leads to analytic equations for the breakthrough front.

In this presentation we compare the properties of the two models in view of prediction of service live cartridges.