Emission characteristics of heavy metals from a typical copper smelting plant.

Heavy metal emissions from non-ferrous smelting plants have been a rising concern. However, their emission characteristics were still unclear. In this study, the concentrations and gas-particle partition of five major heavy metals (Cu, Pb, As, Cr and Cd) in the flue gas from a typical copper smelting plant were measured. The bi-modal distribution of both particulate matter and heavy metals indicated that the particles in super-micron mode was caused by the mechanical crushing and escaping of raw materials, whereas the formation of submicron mode was due to the evaporation and subsequent condensation of volatile substances. The excellent performance of existing air pollution control devices in the studied smelter could substantially reduce the particulate matter and heavy metal concentrations in the extraction and smelting stages by 99.2%-99.9%. The emission factors of PM2.5, Cu, Pb, As, Cr, and Cd were only 283, 2.49, 0.97, 5.92, 0.28, and 0.06 g/t, mostly as the fugitive emission (84.2% on average). In addition, the 'unfilterable' phase of the heavy metals, including the gaseous species and solutes in the filter-penetrated droplet, accounted for averagely 45.8% of the total emissions at the outlet, which indicates the huge underestimation by particle collection only.