Fate of thallium during precalciner cement production and the atmospheric emissions

Abstract

The cement industry is considered to be an important anthropogenic thallium (Tl) emission source, and yet few reports have been released concerning the fate of Tl during cement production and the emissions of Tl from cement plants (CPs). In this study, three precalciner CPs in the Guizhou province in southwest China were systematically investigated, with all input/output solid materials collected and analyzed. Despite using different raw materials, strong Tl enrichment during the clinker production was observed in all three CPs, with enrichment factors ranging from 85 to 148. Tl concentrations in limestone and most other raw materials were low (0.032–4.163 mg kg−1), but they were 100–700 times higher in the raw meal and kiln tail dust due to circulation and enrichment inside the system. Only a low percentage (3–8 %) of Tl exited the system via the clinker and stack emissions. Atmospheric emission factors of Tl from the three CPs ranged from 0.168 to 0.980 mg Tl tonne−1 clinker, with an average of 0.674 mg Tl tonne−1 clinker. Annual atmospheric Tl emissions from all the CPs were estimated to be 54 kg·yr−1 in Guizhou province and 964 kg·yr−1 over all of China in 2018. Shuttling kiln tail dust may reduce the Tl enrichment during clinker production, and Tl recycled from this material may have commercial value.