An Experimental and Modeling Analysis of Heterogeneous Condensation for Ultrafine Particle Abatement

Ultrafine particles are among the most toxic pollutants produced by industrial processes and diesel engines. Nevertheless, the lack of suitable process for their abatement in large scale units is limiting the introduction of new regulations to contain their emissions. Heterogeneous condensation, already used in analytical instrumentations, can be used to enlarge ultrafine particles allowing to use the existing cleaning systems within their actual operational limits. In this paper, experimental and modeling results on the heterogeneous condensation of water vapor on ultrafine particles produced by an ethylene-air flame are reported. The tests have been carried out in a lab-scale facility based on the use of a evaporating liquid film growth tube. Different experimental protocols have been proven and experimental tests have been carried out to estimate the effect of several process parameters, as liquid film temperature and contact time, on the efficiency of heterogeneous condensation. In addition, this paper reports a semi-empirical model that has been used to interpret the experimental data by means of considerations on mass and energy balances in the growth tube and on water nucleation and growing of condensing water on the ultrafine particles.