FILTECH 2022, The Filtration Event

Cologne, Germany

08.-10.03.2022

P. Bächler, J. Meyer, A. Dittler

Baghouse filters are used in a variety of gas cleaning applications in order to lower dust emissions and protect the environment. State of the art filter media generally enable low particle emission levels, where a particle emission peak occurs for a short duration after filter regeneration due to penetration of particles through the filter medium. After sufficient cake formation, the emission drops to a zero level in the case of ideal, leak free operation. Leaks of the filter bag, damaged media surfaces or other defects can significantly increase the overall particle emission of the baghouse. The emission contribution of these “hotspots” may easily exceed the emission contribution of all other filter elements. A potential cost effective technology for spatially resolved online measurement of particle emissions are low-cost PM-sensors due to their compact size and low investment cost. In this study, each of a total of nine filter bags of a small scale baghouse filter has been equipped with a low-cost PM-sensor of the model OPC-N3 from the manufacturer Alphasense. The filter bags were made from a conventional needle felt and have been aged prior to the investigation. Several experiments have been performed in order to determine the capability of identifying particle emission hotspots via low-cost PM-sensors. In a first experiment, three of the filter bags have been exchanged with factory-new bags. A continuous dust emission can be detected via the low-cost PM-sensors installed at the factory new bags due to continuous particle penetration (especially through the seams of the filter medium). After several cleaning cycles and clogging of the seams, the continuous emission disappears and the factory-new bags cannot be distinguished from the aged bags regarding their particle emission of both, the measurement of local emissions directly at the filter bag and the total emission on the clean gas side. In another experiment, one of the filter bags has been pierced by a hot cannula of 3 mm diameter in order to create a strong particle emission hotspot. The low-cost PM-sensor could reliably detect the increase in particle emission due to the leak for varying leak areas at the corresponding bag only. Coincidence effects on the measurement result of the sensor could be observed at higher leak areas (decrease of PM2.5 and increase of PM10). All other sensors showed ideal emission behavior (emission peak after filter regeneration and zero emission during the filtration phase). Differences in the particle size distribution of the emission with increasing leak area mainly consist of a shift to larger particle sizes and an increase in the overall concentration level.