Regeneration of dust filters challenged with metallic nanoparticles: Influence of atmospheric aging

Abstract

The aim of this study was to evaluate the regeneration efficiency of fibrous filters clogged with metallic ultrafine particles, as several complaints have been made by industrials in the metallurgical field about difficulties linked to the cleaning of filters. Aging of the dust deposits on the filters surface was also reported to be problematic. In this work, the metallic nanoparticles were generated by a pilot thermal spraying process using electric arc. Experiments were conducted on flat filters and the cleaning was performed using reverse pulse-jet. The regeneration efficiency was evaluated according to the residual pressure drop, the removed mass and the cleaned surface. Experiments revealed, under different conditions, a patchy inefficient cleaning of the clogged filters. The cleaning efficiency did not exceed 30% according to the removed mass. Clogging/unclogging cycles showed that the filtration process is highly instable as the residual pressure drop kept increasing very rapidly. The influence of atmospheric aging, i.e. exposure to different humidity conditions over time, on the filter cakes was investigated. Results showed that in presence of humidity a chemical reaction was responsible for making the deposit more adherent. The regeneration efficiency was reduced to 10% according to the removed mass after aging for 15 days under 80% humidity rate.

Precoating for improving the cleaning of filter media clogged with metallic nanoparticles

“…The removed mass is evaluated by weighing the filter before and after cleaning. The cleaning efficiency according to the residual pressure drop is not considered in this study as it was found to be insufficient to describe the regeneration of the filter surface in a previous work (Khirouni et al, 2020). Indeed, in the case of a patchy cleaning the formed holes in the filter cake will constitute preferential paths for the airflow causing by that a considerable decrease of the residual pressure drop.…”

“…In the particular case of metallic ultrafine particles emitted from metallurgical processes such as thermal spraying, the clogging of the filter media seems to be irreversible (continuous increase of the residual pressure drop after cleaning). In a previous work (Khirouni et al, 2020), the cleaning efficiency of filters clogged with these metallic nanoparticles was evaluated. Results have revealed a patchy inefficient cleaning that does not exceed 30% according to the removed mass.…”

Operating Behavior of Pulse Jet‐Cleaned Filters Regarding Energy Demand and Particle Emissions – Part 1: Experimental Parameter Study

“…While the research foundations for pulse jet-cleaned filters have been laid in the past by, e.g., Lo ¨ffler [11] or Leith and Ellenbecker [12], present filter operation under demanding conditions still poses its individual challenges [13]. To list some examples, (nano-)particles can cause clogging of the filter material with particulate matter so that the differential pressure increases drastically and the filtration of a protective pre-coat prior to the nanoparticle aerosol might be necessary [7,14,15]. High temperatures and toxic gases push the limits of conventional (e.g., polyester needle-felt) filter media and rigid ceramic filter elements have to be used [16][17][18].…”

“…In this first article, the operation of a small-scale baghouse filter is discussed under energy-related and particle emission-related criteria. The power consumption of the baghouse filter is calculated according to equations proposed by Ho ¨flinger and Laminger [2,14] (compare Sect. 2.3).…”

Spatially Resolved Online Leak Detection in a Baghouse Filter Applying Low‐Cost PM‐Sensors

“…These effects can be caused by an increase of residual pressure drop over the course of long-term filter operation. Especially nanoparticles can lead to clogging and significant aging of the filter medium, so that e.g., filtration of a pre-coat consisting of coarser particles may be necessary [10][11][12].…”