Behavior of Alkali Metal Aerosol in a High-Temperature Porous Tube Sampling Probe

• Published in: Aerosol science and technology Vol. 46; no. 10; pp. 1151 - 1162
• Main Authors: Sippula, O., Koponen, T., Jokiniemi, J.
• Format: Journal Article
• Language: English
• Published: Colchester Taylor & Francis Group 01-10-2012; Taylor & Francis
• Subjects: Aerosols; Chemistry; Colloidal state and disperse state; Condensing; Cooling; Dilution; Exact sciences and technology; General and physical chemistry; Mathematical models; Nucleation; Physical and chemical studies. Granulometry. Electrokinetic phenomena; Porous materials; Sampling; Tubes; Vapor; Nucleation; Wall; Samplings; Artefact; Biomass; High temperature; Ultrafine particle; Probe; Condensation; Porous material; Modeling; Design; Dynamics; Fine particle; Sampling; Laboratory study; Cooling; Alkali metal; Furnace; Dilution; Particle size distribution; Aerosols; Models; Surface area; Homogeneous nucleation
• ISSN: 0278-6826; 1521-7388
• DOI: 10.1080/02786826.2012.700741

Two-component model aerosols consisting of KCl vapor and ultrafine K
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particles were generated in the laboratory to study sample behavior in a high-temperature porous tube sampling probe. The conditions were set to represent those typically occurring at biomass-fired furnaces. Particle size distributions were measured from the diluted aerosol via several sampling parameters and the temperature and mixing conditions inside the diluting probe were characterized. The experimental findings were interpreted by one-dimensional aerosol dynamics modeling. Gaseous KCl was found to form very small KCl particles inside the diluter by homogeneous nucleation. In the cases where K
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seed particles were introduced into the sample, part of the KCl vapor condensed on the seeds, while the remainder formed a clearly distinct nucleation mode due to the relatively high cooling rates in the probe. In the studied probe, mixing of sample and dilution gas was relatively fast, which was found to be favorable for KCl nucleation. The condensation behavior of KCl in the probe with simultaneous dilution and cooling was found to be clearly influenced by mixing, cooling, and surface area of the existing particles. The results show that in the porous tube diluter, different sampling parameters can be used either to enhance the appearance of nucleation mode, or to promote condensation of vapors on existing particles to minimize sample losses on walls. Furthermore, these results point to the possibility to design a high-temperature sampling system, which minimizes the artifacts caused by vapor condensation on existing fine particles during sampling.
Copyright 2012 American Association for Aerosol Research