Transport phenomena in electric smelting of nickel matte: Part I. Electric potential distribution

An electric potential probe was constructed so that simultaneous, multiple measurements of electric potential could be made in a six-in-line electric furnace for smelting nickel calcine having a maximum transformer capacity of 36 MVA. When the electric potential distributions were compared with those calculated from the solution of the Laplace equation, it was evident that there was significant electric potential drop at the electrode surface, 100 to 120 V for an applied potential of 180 to 230 V and currents of 20 to 30 kA. The Soderberg electrodes were continuously oxidized in the slag, likely creating carbon monoxide. The electric potential drop at the surface was attributed to arcing through the carbon monoxide. Thus, heat was released in the immediate vicinity of the electrode due to arcing, as well as in the bulk of the slag by Joule heating. The proper distribution of heat dissipation is required for the transport model, developed in Part II of this series.