Mercury Speciation Under Laboratory Scale Direct Iron Smelting Conditions

  • Mr Pushan Shah, Graduate School of the Environment, Department of Environment and Geography, Macquarie University, Sydney NSW 2109, Australia, Australia
  • Dr Vladimir Strezov, Graduate School of the Environment, Department of Environment and Geography, Macquarie University, Sydney NSW 2109, Australia, Australia
  • Dr Tim Evans, Hamersley Iron Pty Ltd, GPO Box A42, Perth WA 6837, Australia, Australia
  • John Takos, Rio Tinto Technology and Innovation, 1 Research Avenue, Bundoora 3083 Australia., Australia
  • Prof Peter Nelson, Graduate School of the Environment, Department of Environment and Geography, Macquarie University, Sydney NSW 2109, Australia, Australia

    • Mercury is among the most toxic trace metals, a potential neurotoxin which bioaccumulates in the aquatic biota and subsequently enters the food chain. While mercury emissions from coal fired power stations have been extensively studied, much less effort has been devoted to characterise emissions of mercury from iron making process, where contributions of mercury present in the ore and in the coal used as a reducing agent may be significant. Understanding of the detailed chemistry of mercury in ironmaking systems and release of different forms of mercury to the atmosphere is important given that the distribution, mobility and bioavailability of mercury depends on its various chemical forms and oxidation states (or speciation). Moreover, speciation of mercury determines the extent of its capture in existing pollution control technologies.

    This study describes measurements of speciation of mercury in off gas from laboratory scale direct iron smelting process involving the use of circulating fluidised bed (CFB) reactor. Speciation of mercury in off gas was determined using the Ontario Hydro sampling train method. Samples of feed coal, iron ore and waste products were also collected during the experiments and were analysed for total mercury content to calculate the mass balance of mercury. The measurements were performed under several different operating conditions in an attempt to derive possible mechanistic understanding of the chemical reactions leading to mercury transformation under the reducing conditions of iron making processes.