Within a European collaborative research project aimed at reduction of fine iron containing particles (0.5-m - 10-m) in steelmaking process water circuits, a new magnetic separation system using permanent magnets has been designed and tested. Hot rolling mill process water for descaling and cooling can accumulate large amounts of suspended solids that can cause spray nozzle wear (influencing product quality), erosion of equipment, clogging, lower performance and hence higher maintenance costs. Low quality water can also cause environmental issues by exceeding the regulatory limits, and higher water consumption from increased blowdown. Removal of these water solids is essential. This paper describes research undertaken at a Tata Steel site (UK) in collaboration with BFI (Germany) to develop a new magnetic separation system to efficiently remove the solids and produce sludge with low water content. Results of CFD simulations and site trials have been used to determine the exact positions and number of magnets. Performance of the system was assessed by treating the mill process water. Flow rates of higher than 50m3/h, efficiencies greater than 98% and reduction of chemical dosing by 50% have been achieved. In comparison with a typical sandfilter, the tested magnetic separator is more compact, produces sludge with 20 times more solids content with water content of only 0.06% of the treated flow compared to 1% -10% of conventional sandfilters. The research leading to these results has received funding from the European Union Research Programme of the Research Fund for Coal and Steel (Grant Agreement number: RFSR-CT-2012-00042).
Mansour Saiepour, Tata Steel Group Environment, UK
Martin Hubrich, VDEh-Betriebsforschungsinstitut GmbH (BFI), Germany
Stream: Environmental Sustainability & Human Consumption: Waste
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