Influenct factors of variation of boron elution from coal bottom ash

Abstract

Coal bottom ash (CA) generated from the bottom of coal boilers contains soluble boron and the level of the concentration often exceeds the Soil Environmental Standard value for Boron. The relationship between boiler combustion conditions and soluble ions in CA were investigated to estimate the factors that cause fluctuations of boron contained in CA. The results showed that there was no significant relationship between the soluble boron and the combustion conditions of the boiler. It was found that the soluble boron in CA has a relationship with concentrations of calcium and sulfate measured by the leaching test. It was found that the saturation index values of gypsum in CA obtained by PHREEQC software with higher soluble boron was larger than that with lower soluble boron. This result indicates that the soluble boron in CA was embedded or adsorbed in gypsum and the variation of soluble boron would be influenced by the amount of gypsum in CA.