Experimental Study on Evaporation Characteristics of Ammonium Formate-Urea-Water Solution Droplet for Selective Catalytic Reduction Applications

Abstract

The evaporation behavior of ammonium formate-urea-water solution (AFUWS) droplet was studied for applications to selective catalytic reduction (SCR) systems. A number of experiments were performed with single AFUWS droplet suspended on the tip of a fine quartz fiber. To cover the temperature range of real diesel exhausts, droplet ambient temperature was regulated from 373 to 873 K using an electrical furnace. As a result of this investigation, AFUWS droplet revealed different evaporation characteristics depending on its ambient temperature. As ambient temperature increases, in addition to evaporation of water content, thermal decompositions of ammonium formate and urea were additionally observed. At hi h temperatures, it showed quite complicated behaviors such as bubble formation, distortion, and partial rupture after a linear D(2)-law period. However, as temperature decreases, these phenomena became weak and finally disappeared. Also, droplet evaporation coefficients were retrieved from transient evaporation histories for various ambient temperatures, which yield a quantitative evaluation on evaporation characteristics of AFUWS droplet as well as provide valuable empirical data required for modeling or simulation works on SCR systems.