Factors Influencing the Lead Content Of Brunswick Blast-Furnace Slag

CIM Bulletin, Vol. 70, No. 786, 1977

A. G. Matyas, Senior Engineer, Hatch Associates Limited, Toronto, Ontario, M. D. Street, Production Superintendent, Brunswick Mining and Smelting Corporation Limited, Smelting Division, Belledune, New Brunswick, Previously with Noranda Research Centre, Pointe Claire, Quebec.

Process improvements which have reduced the lead content of staff from the Brunswick lead blast furnace are described. Microscope examination and electron micro-probe analyses, supported by the results of slag settling and viscosity tests, showed that typically about 70% of the lead in the lead blast-furnace slag was present in the form of entrained prills of metallic lead. The total lead content was found to increase with the magnetic susceptibility of the slag. Measurements in the furnace settler indicated the presence of a magnetite-rich layer between bullion and slag, arising from high magnetite levels in the slag. This layer was believed to inhibit the settling of entrained lead from the slag. Tracer tests showed that the average slag residence time in the settler was less than 2 minutes. Improvements in coke quality and sizing, which led to a reduction in the slag magnetite content, and the installation of a larger settler and a continuous Roy tapper, have all contributed to a significant decrease in the slag lead content.
Keywords: Brunswick Mining and Smelting, Slag, Blastfurnace slag, Lead smelting, Sinter, Settlers, Coke sizing, Roy tappers.