Homogenization of Metastable Chlorine By-pass Dust through Mineral Carbonization

Chlorine bypass dust (CBPD) from cement kilns shows significant heterogeneity due to variations in kiln operation and alternative fuels, hindering its reuse in construction materials. This study characterizes nine CBPD samples and applies water washing and mineral carbonation to evaluate their homogenization efficiency. The novelty of this study is that it (i) compares differently supplied CBPDs, (ii) quantifies the homogeneity of their physical, mineralogical, thermal and chemical properties, and (iii) identifies that mineral carbonation effectively stabilizes the metastable Ca-containing phase into CaCO3. While washing removed up to 89.6% of chloride, it increased heterogeneity in Ca-bearing phase content. In contrast, carbonation removed up to 96.1% of chloride and produced a uniform CaCO3-rich phase (> 96%), improving homogenization efficiency. Although lead (Pb) leachability remained inconsistent, other heavy metal leachabilities were lowered than the environmental limit. Thus, mineral carbonation effectively homogenized the metastability of CBPD.