The release of the hazardous elements from coal in the initial stage of combustion process

The studies on the behavior of the accessory elements during coal combustion are helpful to control the emission of the hazardous air pollutant (HAP) emissions. In this paper, the release of the hazardous accessory elements, As, Cd, Co, Cr, Mn, Ni, P, Pb, Sb, Se, and V in the initial stage of coal combustion was studied. Three sequential extraction agents, including the water, the ammonium acetate solution (AAS) and the hydrochloric acid solution (HAS) as indicated order, were employed to determine the occurrence of each element. The results showed that there were obvious differences in the volatility performance among the elements in this stage, almost nonvolatile capacity for elements Mn, Ni and P; low volatile capacity for elements As, Co and V; volatile capacity for elements Cd, Cr and Pb; and high volatile capacity for elements Sb and Se. The experimental results also showed that the volatility of the element is depended on the occurrence modes of element, the type of the coals, and the operating conditions. During the initial stage of coal combustion, there was also some transformation among the different occurrence modes of element defined as the water soluble (WS), the ammonium acetate soluble, the acid soluble and the acid insoluble (AI).