Spray scrubber for nanoparticle removal from incineration fumes from the incineration of waste containing nanomaterials: Theoretical and experimental investigations

Abstract

Nanomaterials (NMs) are currently treated via recycling, incineration and/or landfilling at their end-of-life. Little is known about the fate of NMs in incineration systems and the efficiency of the available flue-gas cleaning technologies (FGCT) in these systems on the removal of NMs before stack release. In combination with other FGCT such as cyclones, electrostatic precipitator or bag filters, scrubbers participate to limit the release of particulate matter (PM) into the atmosphere. No study has been carried out to investigate wet scrubber collection efficiency regarding nanoparticles under conditions found in a waste incineration plant. In the present study, experimental campaigns were carried out to quantify the performance of a pilot-scale spray scrubber regarding the removal of nanoparticles. The pilot was designed with respect to geometrical, hydrodynamic and residence time scale similitude and operated in gas temperature and humidity conditions representative of full-scale scrubbers in hazardous waste incineration plants. A collection efficiency of 45–62% for a particle size range of 12–90 nm was reported. To evaluate the experimental results, an existing PM collection model based on the 3 main particle collection mechanisms of diffusion, interception and impaction, was adapted for extreme humidity and gas temperature conditions typical of a waste incineration plant. A comparison of the experimental and theoretical results was made indicating that the model results were in good agreement with the experimental results. Contrary to prior studies, the impaction-dominant region occurred at smaller particle sizes (0.1–0.2 µm) corresponding to Stokes number 9 × 10−3 to 4 × 10−2. Numerically, the contribution of the interception mechanism in the collection of nanoparticles (particle sizes 1–100 nm) was found to be negligible (i.e., Interception number 2 × 10−5 to 2 × 10−3).