Conceptual Model Of Tapping Mechanisms In FeSi/Si Furnaces

Tapping has mainly been an experience based sub-process in the silicon and ferrosilicon production process. To get this part of the process into a more scientific area, represented by e.g. CFD modelling, a conceptual model on the process is needed. This paper will hence start the work on describing some of the operational parameters that may link the furnace operation to the tapping process. The tapping process of a Si/FeSi furnace, that is the tapping rate, will be dependent on the zones and material in the furnace. The drainage of the furnace can be divided into 3 steps; Step 1 that describes the drainage from the back-electrodes to the tap-electrode, Step 2 that is the drainage in the near tap-hole region, and Step 3, the flow through the tap-hole. Each of these steps will be dependent on the zones and materials in the furnace. The flow from the back-electrodes (Step 1) will be determined by furnace gas pressure as well as high viscosity materials, as e.g. a slag layer, or SiC crusts, hindering the flow. Affecting the flow from the tap-electrode to the tap-hole (Step2), it is seen that the metal must drain through a slag zone filled with small SiC particles. Step 3 is dependent on the material in the entrance of the tap hole, in addition to the geometrical measures of the tap-hole as well as the density and to a lesser extent the viscosity.