Abstract
It is the goal of this study to identify substances that have critical role in the metallic mercury removal from incineration flue gas by the coexistence with activated carbon and to clarify the metallic mercury removal mechanism by the simulated synthetic fly ash.
This synthetic fly ash, which consisted of calcium chloride with 5% activated carbon, showed very high efficiency of over 99% for mercury removal at the temperature of 120t, the moisture of 20% and air atmosphere. It was found that metallic mercury changed into mercury (II) oxychlorate on the surface of activated carbon and an oxychlorination reaction occurred in the synthetic fly ash at the temperature of air pollution control device. The metallic mercury removal mechanism by the synthetic fly ash is considered to be a chemisorption through the following route; metallic mercury-mercury (II) oxide→mercury (II) chloride→mercury (II) oxychlorate.
In order to evaluate the influence of quantity of activated carbon and calcium chloride on metallic mercury removal, the experiments were performed using the synthetic fly ash which consisted of activated carbon, calcium chloride and silicon dioxide. When the calcium chloride content was more than 0.5% in the synthetic fly ash with 5% activated carbon, mercury vapor was completely removed. Whereas, the highest removal efficiencies were obtained when the activated carbon content was ranged from 5 to 7% in the synthetic fly ash with 1% calcium chloride. The mercury removal ability was affected by temperature, if the activated carbon content was very small. Because these phenomena were also observed in the experiments using calcined fly ash with 5% activated carbon, it was supposed that the complex chemical action with activated carbon and calcium chloride was most significant for metallic mercury removal by actual fly ash.
