Origin of spatio-temporal particle emissions of surface filters due to clogging and release of particles from previously clogged seams of individual filter bags due to jet-pulse cleaning
AFS FILTCON 2021
V. Löschner, P. Bächler, J. Meyer, A. Dittler
Despite the impact of particle emission hotspots (e.g. the seams of the filter bag, leaks, or damaged media surface) on the total particle emission in baghouse filters, filter houses are largely treated as a “black box” where only a total particle emission is monitored. Through the application of scattered light-based low-cost particulate matter sensors, the particle emission contribution of individual filter bags can be measured with high spatial and temporal resolution. The seams of filter bags, on the basis of the manufacturing process of the bag, are a known origin of particle emissions in baghouse filters, as they enable particle penetration from the raw gas to the clean gas side. When applying factory new membrane filter bags with regular seams in a small-scale baghouse filter testing facility, a continuous but decreasing particle emission occurs during the initial filtration cycles, primarily indicating clogging of the seams. After several complete filtration cycles, the continuous emission disappears, and mainly particle penetration through the filter medium after filter regeneration in the form of an emission peak can be detected both locally via low-cost particulate matter sensors and via monitoring of the total particle emission applying a PALAS® optical particle counter as reference. However, individual emission hotspots causing a continuous emission may appear and disappear – seemingly at random - at measurement positions of individual filter bags during operation. Increasing the tank pressure leads to an increase in the frequency and the intensity of this cycle-dependent continuous particle emission. Measurements applying the PALAS® reference at a singular filter bag confirm this Spatio-temporal emission dynamic. This behavior is likely the result of the release of particulate matter from the previously clogged seams of the filter bag due to jet-pulse cleaning. After the release of particles, the seams are no longer clogged, enabling renewed particle penetration and thus, a continuous emission. This reaffirms the importance of choosing the right pressure intensity for pulse-jet cleaned surface filters and demonstrates the potential of local & simultaneous particle emission measurement in order to detect emission hotspots within baghouse filters.