11 June 2001

Finland-based Dekati Ltd. announced a new instrument for the conditioning of exhaust emission samples for ultrafine particle measurements, which, through the removal of volatile hydrocarbons, minimizes measurement variation due to uncontrolled semivolatile condensation and nucleation.

Dekati Thermodenuder is designed to remove volatile and semivolatile compounds from exhaust samples. Volatile/semivolatile compounds are known to cause variation in measurements due to condensation and supersaturation. In the Thermodenuder, these unwanted compounds are vaporized by heating the sample aerosol with an aerosol heater to 250°C. Since the particles in the sample have much slower diffusion speeds (for 10 nm particles < 1/100) than the vaporized compounds, the vaporized volatiles are collected efficiently in the thermodenuder’s annular charcoal adsorber while the sample aerosol particles follow the gas streamlines unaffected. Water or pressurized air driven through the Thermodenuder cools the sample aerosol in the adsorber.

Particle losses are minimized by optimized flow fields and thermal protection. The heater control keeps the heating temperature stable, which helps to prevent unexpected sample transformations. The adsorptive bulk granulate material is replaced by an activated carbon cartridge, which offers easier maintenance, more adsorption capacity and extended lifetime. In addition, inlet of the adsorber section has been redesigned to avoid impaction of particles, thereby decreasing particle losses.

The Thermodenuder is suitable for use with very sensitive ultrafine particle measurement instruments like SMPS (Scanning Mobility Particle Sizer) and ELPI (Electrical Low Pressure Impactor), also manufactured by Dekati.

For more information contact Dekati Ltd., +358-3-3578-10, sales@dekati.fi.

Source: Dekati Ltd.