Reacting flow field simulation of Hg⁰ oxidation in flue gas by ozone injection

Abstract

Ozone injection is an effective way to oxidate Hg⁰ in flue gas. The reacting flow field for the oxidation of Hg⁰ by O₃ is numerically studied in detail with a reduced chemical mechanism in this paper. Based on sensitivity analysis with detailed chemical mechanism, a 12-steps reduced chemical mechanism is obtained and used in the following three-dimensional simulations of the reacting flow field. Through the reacting flow field simulation, the influence of various factors on Hg⁰ oxidation efficiency is calculated and analyzed, such as O₃/NO molar ratios, jet velocities, moisture, temperatures, NO concentrations and Hg⁰ concentrations. Results show that temperature and O₃/NO molar ratio are the key factors, jet velocity and NO concentration are the important factors, while water content has little effect. It is also found that the oxidation efficiency of Hg⁰ is shown to be highly correlated with the amount of NO₃ generated in the flue gas. Increasing the local generation of NO₃ may be the key to achieve efficient oxidation of Hg⁰. This study is good help of subsequent engineering applications.