Candle composition is expected to influence the air pollutants emissions, possibly leading to important differences in the emissions of volatile organic compounds and polycyclic aromatic hydrocarbons. In this regard, the purity of the raw materials and additives used can play a key role. Consequently, in this work emission factors for some polycyclic aromatic hydrocarbons, aromatic species, short-chain aldehydes and particulate matter have been determined for container candles constituted by different paraffin waxes burning in a test chamber. It has been found that wax quality strongly influences the air pollutant emissions. These results could be used, at least at a first glance, to foresee the expected pollutant concentration in a given indoor environment with respect to health safety standards, while the test chamber used for performing the reported results could be useful to estimate the emission factors of any other candle in an easy-to-build standardised environment.

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A laboratory-scale dual-reflux pressure swing adsorption process unit comprised of two beds with intermediate feed position was built and tested for concentrating dilute gaseous feed of methane in nitrogen using Norit RB1 activated carbon. Experimental investigations revealed that the change in blowdown or pressurization step time, feed or purge step time, and heavy product flow rate did not have a significant effect on process performance (in terms of methane purity). However, the process performance was found to be quite sensitive to changes in light reflux flow rate. These experimental results were used to validate the predictions of a mathematical model developed in the frame of the commercial software Aspen Adsim, thus providing an effective tool to elucidate process behavior.

The classical gas chromatographic technique is applied to measure the solubility and diffusivity of ethylene and propylene in polypropylene. The polymer particles were used as supplied by the producers to pack the chromatographic columns. This allows a direct measurement of the interested properties in a particle with the same morphology obtained at the reactor outlet. Moreover, the apparatus was adapted to carry out measurements at pressures and temperatures close to those typical of the reaction conditions. The measured values of solubility and diffusivity compare favorably with those predicted by literature relationships for semicrystalline polymeric matrices. Moreover, the estimated diffusivities indicate the diffusion in the polymer microparticles as the rate determining step and a diffusive characteristic length comparable with the particle diameter, i.e., larger than expected in the frame of a multigrain particle schematization. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 464–473, 2000

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