Capture Characteristics of Gaseous Elemental Mercury by Carbonized Waste in Air and Reducing Atmospheres

Abstract

Coal contains harmful trace elements. Especially, mercury has high volatility. Mercury of approximately 27% in coals used in coal fired power plants is released as gaseous elemental mercury in a flue gas to the atmosphere. In an ironmaking system, since large amounts of coal are used as a reducing agent and heat source, there is a possibility that the gaseous elemental mercury emits from some processes. Therefore, an objective in this work is to develop adsorbents that are able to capture the gaseous elemental mercury in an air atmosphere and a reducing atmosphere. In this work, carbonized wastes (sewage sludge, paper sludge, woody biomass and municipal solid waste) were used as experimental samples. As a result, the municipal solid waste char has the highest property to capture the elemental mercury in the air atmosphere at 423 K. From results of X-ray Absorption Near Edge Structure (XANES) analyses, the mercury captured in the municipal solid waste char was mainly captured as mercury sulfide (HgS) on the char. On the other hand, a mercury capture ratio of the municipal solid waste char in the reducing atmosphere was lower than that in the air atmosphere.