The detachment of particle structures from single fibres in gas flow has been investigated only for inert particle structures yet. This study investigates the detachment of particle structures containing reactive components. These reactive components disappear during the reaction and enhance detachment at low flow velocities. Soot was used as the reactive component and glass spheres as the inert component of the particle structure. The soot disappears due to combustion with oxygen leaving only the glass spheres on the fibre. Without reaction, the detachment phenomenon was observed at superficial flow velocities above 1.9 m/s and with reaction at 0.5 m/s. This shows that reacting and disappearing components of the particle structure can enhance detachment.

Current air monitoring networks consist of many measuring stations equipped with sampling systems for the measurement of PM2.5 and PM10 particulate matter. To measure the quantity of particulate matter, the sample air flow is fed to the measuring device through a sampling system. In Baden Württemberg, but also across a wide area in Germany, these sampling systems consist of a Sigma-2-Sampling Head (manufacturer Palas GmbH) and an Intelligent Aerosol Drying System (IADS, manufacturer Palas GmbH). To investigate the suitability of these two common components for sampling of ultrafine particles (< 100 nm), the particle loss inside a sampling system consisting of a Sigma-2-Sampling Head, an IADS, and an additional nafion-dryer (MD-700-24S-1, manufacturer Perma Pure LLC) is measured in this study. A low sampling flow rate of only 0.9 l/min was employed to reduce energy consumption, complexity, and the cost of additional instrumentation. This sample flow rate is typical for scanning mobility particle sizers which are commonly used to measure ultrafine particles. The investigations show a 37% loss of spherical 10 nm copper particles in the used sampling system, which is higher than the allowed losses specified in DIN CEN/TS 16976 for 7 nm particles. The root cause of these losses was investigated and correlations were derived to describe the particle penetration in the sampling system.

A novel apparatus was developed, to investigate the detachment of particle structures consisting of soot and ash from a single fibre or a fibre array in hot gas flow. Key features of the novel apparatus are operation at high temperatures while two different measurement techniques are applied simultaneously in the same measurement chamber to observe particle structure detachment from a loaded fibre array. A heated inlet can heat the air stream at the position of the fibre array up to 470 °C, allowing detachment investigations at temperatures relevant for the operation of, e.g., soot particle filters. The first measurement technique integrated in the setup is video recording of the fibre array, which gives qualitative information on the rearrangement or detachment of particulate matter on the fibre. Because it is often difficult to distinguish rearrangement and detachment from pure visual observations, a second measurement technique is applied. This technique is a laser-light-sheet optical particle counter, which can detect detached particle structures and determine their size. The measurable size range is 257 to 1523 µm for glass spheres. This paper presents and discusses the novel apparatus, its calibration and first detachment measurement results.