Catalytic effects of inorganic compounds on the development of surface areas of fly ash carbon during steam activation

This study was to investigate the catalytic effect of inorganic compositions present in fly ash carbons, high-unburned-carbon content fly ashes from coal-fired power plants, on the development of surface area during steam activation. Through this work, the relationships between the concentrations of alkali metals (Na and K) and a mixture of metals, Na-K-Ca and Na-K-Fe, in fly ash carbon and the surface areas of the produced activated carbon were studied.

Six fly ash carbons were selected as feedstocks for activated carbon. SEM/EDS studies showed that there are two groups of inorganic particles present in fly ash carbons, in terms of the way they are associated with carbon particles: inorganic particles that exist as free single particles, and inorganic particles that are combined with the carbon particles. A series of froth flotation tests was conducted to separate the individual inorganic particles from the fly ash carbons. The concentration of the inorganic particles was analyzed using ICP-AES before and after froth flotation separation. Studies showed that the Na-K, Na-K-Ca, and Na-K-Fe which are combined with carbon particles had catalytic effects on the development of the surface areas of activated carbons. The higher the concentration of these catalytic particles, the more significant effects they had on the development of the surface areas with increasing carbon burn-off levels. (C) 2010 Elsevier Ltd. All rights reserved.