THREE-PHASE RECTIFIER, DIRECT CURRENT, PROCESSING OF FERRO-ALLOY WASTE, FURNACES OF DIRECT CURRENT

Abstract

An analysis of the current state and structural features of modern domestic ferroalloy furnaces was performed. Prospective directions for the reconstruction of ferroalloy furnaces used for the processing of ferroalloy production waste are considered. Currently, for these purposes, direct current furnaces have become the most common. However, this technology in the reconstruction of existing electric furnaces requires a complete replacement of the alternating current electric furnace and the furnace transformer and large capital costs for reconstruction. Various technologies for processing screenings from fractionation of ferroalloys were considered and tested. For the processing of secondary raw materials, direct current furnaces were developed for the remelting of ferroalloy production waste. The purpose of the reconstruction was to install a reversible 3-phase rectifier (thyristor converter) in the power circuit between the existing transformer and the existing ore-thermal AC electric furnace. At the same time, the power and design of the electric furnace remained unchanged. As a result of transferring the electric furnace to power supply from a reversible 3-phase rectifier, this electric furnace in terms of its technological indicators came close to the direct current electric furnace, the advantages of which were described above, due to the use of ultra-low frequency. Stabilization of the current in each phase of low frequency allows, with the same currents of the electrodes, to keep different voltages under them, as well as without disturbing the symmetry of the currents of the power network.In addition, the stabilization of the current provides a "soft" mode of the arc, which reduces the evaporation of the metal, and also creates favorable conditions for sintering electrodes, which increase their stability and reduce consumption. The results of the study showed that the technical retooling of ferroalloy furnaces from switching to direct current use and the use of a reversible thyristor 3-phase converter operating at an ultra-low reverse frequency made it possible to: reduce the specific consumption of electricity compared to alternating current furnaces;to significantly reduce losses during melting due to evaporation and carbon dioxide.