Submicronic Particle Abatement using Electrified Water Droplets - an Experimental Investigation

During the recent past the direct and indirect impacts of particulate emissions on human health, ecosystems and climate has been unequivocally demonstrated. In spite of this situation, large scientific and technological efforts are still needed to reduce the emissions of submicronic particles from industrial processes or diesel engines below safety levels. The wet electrostatic scrubbing (WES) uses electrostatic interactions between particles and charged droplets to significantly enhance the particle capture efficiency of wet (uncharged) scrubbers. The WES was studied in the past for micron sized particles. The models developed and the few experimental investigations have shown how such a system is far more effective in the capture of submicronic particles. In this work a new experimental approach to the study of WES process is proposed. Experimental set up consists of a cylindrical chamber where a model particle laden gas (obtained from the dilution of an ethylene-air flame) comes into contact with a train of identically charged droplets that are produced by a specifically designed electrospray nozzle operating in dripping mode. The system is instrumented to measure and control reactor temperature and humidity, droplet size charge, and water and gas flow rates. The chamber is operated batchwise with reference to the gas phase and the concentration and size distribution of particles in the chamber is measured over time by means of a laser spectrometer. The design of the laboratory scale equipment and preliminary experimental results are presented in this paper. The main advantage of this new experimental approach is that the use of a train of droplets should overcome some complexities inherent in the use of spray (i.e. the knowledge of the actual value of droplet size and charge distribution and the jet dynamics) that are currently limiting the definition of specific design and scale up rules for WES unit.