Conductive heating and melt circulation in pyrometallurgy

Melt circulation and conductive heating are introduced in relation to the then new imperial smelting furnace (ISF) for the production of zinc in a blast furnace. The focus then changes to projected development of a recently proposed continuous steelmaking process, in which pools of molten iron/steel are created inside residual solid ferrous material to form a cascade of interconnected melt circulation loops. These pools are maintained at the liquidus temperature by melt circulation with the thermal requirements being provided by conductive heating, during start-up, stand-by or planned shut-downs. During operation, the various ‘swimming pool reactors’ process well-mixed iron bearing materials (virgin ore or secondary material) with granular/pulverised coal and flux, deposited as charge on the moving surface of the iron-making loop. A solid raft of metallised material is first formed and then projected by drag forces onto the surface of the first of the steelmaking loops, in which melting and slag/metal separation occurs along with partial decarburisation and desulphurisation. The continuous overflow by a hot metal siphon is treated in at least one further melt circulation loop to produce refined steel ready for continuous casting. Key features of hot metal siphons, emphasising the requirements for conductive heating, are discussed in detail.