Investigation on the gas particle separation efficiency of the gas particle partitioner

A gas particle partitioner (GPP, US patent 6,761,752 B2) that allows highly efficient separation of gas and particles with no effect on the thermodynamic conditions and substantially no change of the composition of the gas has been developed. The GPP is a coaxial arrangement with inner and outer electrode. It utilizes a corona discharge to electrically charge the particles and a strong electric field in a separate unit to take them out of the sample flow. Several measures were taken to minimize an effect of the corona discharge on the gas composition. The GPP is designed such that when switched on, the sample flow is particle free, whereas when switched off, the sample flow contains a representative sample of the aerosol. The GPP as described in this manuscript was designed to meet the requirements for precise artifact correction with particle mass concentration monitors, such as the TEOM. This paper focuses on the gas particle separation efficiency of the instrument. The separation efficiency was determined for both, (ultra-) fine and coarse particles. The (ultra-) fine particles were generated with diameters ranging from 18 to 255 nm of polystyrene latex particles and their size distributions measured with a scanning mobility particle sizer (SMPS). Coarse particles with diameters between 4.5 and 10.7 μm were generated from a sodium chloride solution and characterized with an aerodynamic particle sizer (APS) and a tapered element oscillating microbalance (TEOM). The investigations showed that the separation efficiency was very near 100% for all particles with diameters larger than 25 nm, whereas it decreased for smaller diameters. Particles of size 18 nm were separated from the gas flow with an efficiency of approximately 97%. Along with near 100% separation efficiency, the additional gas concentrations were 42 ppbV for O 3 and 15 ppbV for NO 2.