High Content Of H₂O Inhibiting Oxidation Mechanism Of Mercury Under Oxy-fuel Combustion （O₂/CO₂）

Mercury has long been identified as a hazard to human health and the environment. Since coal-fired power plants represent a significant fraction of the anthropogenic emissions of mercury into the atmosphere, the speciation and control of mercury in coal-fired power plants is currently an active topic of research. The physical and chemical properties, the distribution and occurrence characteristics of Chinese coal were presented in the paper. The information of mercury measurement and control in coal-fired power plants was introduced systematically.The key point in the research of mercury emission control from new coal combustion type, such as coal oxy-combustion(O2/CO2), is full knowing of mercury speciation emission from coal combustion in O2/CO2 atmosphere, especially definite understanding of the influence of high H2 O concentration on inhibiting oxidization of mercury in O2/CO2 atmosphere. This paper mainly studies the influence of high H2 O concentration of tail flue gas to the generation of Cl/Cl2 and the Hg oxidation process when the conditions about fly ash existence.Based on the principle of methyl orange spectrophotometry, established the measurement of Cl/Cl2 under oxy-combustion atmosphere, and measured the generation of Cl/Cl2 in different temperature, different concentration of HCl and H2O(g)conditions. Studied the influence of HCl concentration, reaction temperature, content of H2O(g), and fly ash to Hg0 oxidation efficiency under oxy-combustion atmosphere. The preliminary experimental results show that high temperature and high concentration of HCl promote the generation of Cl/Cl2, and promote a rise to Hg0 oxidation efficiency, however, the H2O(g) had the opposite effect. When change the working condition of fly ash only, the Hg0 oxidation efficiency value is higher when the fly ash existence, and this phenomenon is more obvious in high temperature area.Through the experiment and the analysis of experimental data, The aim of this research is to master the basic mechanism of interaction among the H2O-Cl-Hg and promotion methods on oxidizing mercury in coal O2/CO2-combustion flue gas, The results of this research will improve theory of O2/CO2-combustion and accelerate the development of new mercury control method for coal O2/CO2-combustion.