Substance-flow analysis and emission-reduction strategies for thallium in the steel industry process

Abstract

Thallium, which is a highly toxic and sparsely distributed element, is often found in various mineral compounds. Its release into the environment primarily occurs through the mining of metals, metallurgical processes, and the combustion of fossil fuels. These activities release thallium from minerals, concentrating it in ash, wastewater, and exhaust gases, thus contributing to thallium pollution. With over 600 active steelworks in China continuously producing steel, the risk of thallium pollution is significant and thus presents a major challenge. This research focuses on understanding the mechanisms of the physical phase evolution, migration pathways, and emission characteristics of thallium in steelworks. For the first time, a thallium flow network in steelworks is developed using substance flow analysis. This involves examining the input, output, waste discharge characteristics, and potential for reduction of thallium. The findings reveal that iron concentrate is the primary source of thallium in steelworks, with dust being the main form of thallium output. The quantities of thallium input, output, and circulation are found to be 425.44, 365.49, and 49.66 mg/t-CS, respectively. Implementing source control, endpoint governance, or a combination of both can reduce pollutant emissions in steelworks by 41.47%, 43.35%, and 65.63%, respectively. This study enhances our understanding of thallium pollution in steelworks.