Ammonium salt-based steelmaking slag carbonation: Precipitation of CaCO3 and ammonia losses assessment

Abstract

A mineral carbonation method based on steelmaking slags and ammonium salt solutions has been found to have economical and CO2 emission reduction potential. Although the aqueous solution of ammonium salt can be recycled, some of the solvent is likely to escape in a form of ammonia vapor within the outgoing gas fl ow during the carbonation step. In this study, the escape of ammonia vapor was investigated. The loss of NH3 was found to be quite insignifi cant and in addition, the total solution loss per step was very small. The CO2 content of the ingoing gas fl ow affected the rate of the CaCO3 precipitation; the smaller the CO2 content, the longer the duration of the carbonation reaction. However, the CO2 content did not seem to have a signifi cant effect on the degree of CaCO3 precipitation, indicating that CO2 capture in a separate process step should not be needed. CaCO3 precipitated in a form of calcite, although two of the precipitates also contained aragonite. Furthermore, the precipitates were found to be of high quality with bright white color, and fi ne and powdery texture. Nonetheless, in order to obtain high-quality CaCO3, the precipitate resulting from the carbonation step should be washed with an adequate amount of water. © 2011 Society of Chemical Industry and John Wiley & Sons, Ltd.