ENHANCEMENT OF ADSORPTION CAPACITY BY USE OF PHASE CHANGE MATERIAL (PCM) AS ADDITIVE IN AN ACTIVATED CARBON (AC) FIXED BED ADSORBER

To avoid emission of volatile hydrocarbons from automotive tank systems, canisters filled with activated carbon (AC) are placed as a buffer to the environment. During the loading of the filter the heat of adsorption released leads to a temperature rise of the AC and hence to an unwanted decrease of storage capacity. By mixing an optimized amount of phase change material (PCM) to the AC the heat effect can be diminished and thus the adsorption capacity of the filter compared with a fixed bed consisting of pure AC increased by more than 15%. Also, the desorption process is enhanced by the PCM, as part of the desorption energy is provided by the latent heat stored in it. The differential and integral heats for n-butane adsorption on activated carbon have been determined by use of a novel sensor gas calorimeter.

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In knowledge of the data, an optimized amount of PCM to be added to the carbon could be specified. Both, effectiveness of PCM addition as well as the most appropriate melting, i. e. phase changing temperature of the PCM have been investigated in a special testing equipment by systematic experimental work.