The joint project "EMELO" further improved the material and energy efficiency of the crude steel production process from steel scrap in electric arc furnaces. The well-aimed control of natural gas and oxygen input resulted in a reduced electrical energy consumption and an increased yield of iron and valuable alloy elements from the scrap. Process optimization on the basis of newly developed sensor technology and the development of new refractory material led to a reduction in thermal losses.
Crude steel production in electric arc furnaces is one of the most important steel production processes worldwide. In Germany this process accounts for roughly 30 percent of the annual crude steel production, which amounts to about 13 million tons. With the help of electrical and chemical energy, steel scrap is molten in a furnace with a refractory lined hearth and water cooled wall panels and roof. The meltdown process causes both substantial energy losses and an unwanted material loss through over-oxidation of the molten steel.
In order to adjust the supply of additional oxygen for post-combustion of not fully combusted chemical energy carriers in the furnace off-gas, a control system based on an already existing continuous off-gas analysis was installed. This resulted in substantial energy savings by reducing energy losses via the off-gas. In addition, a well-aimed control of the oxygen supply for decarburisation was developed through model-based calculations of the current oxidation state of the molten steel. This results in an increase in the metallic yield of iron and alloy elements, and at the same time a decrease in the consumption of deoxidation materials.
Furthermore, a photo-based sensor was developed to detect a freely burning electric arc, to allow an almost immediate reduction of the electric power of the furnace, which significantly reduces thermal losses via the water cooled wall elements. New refractory material was also developed and installed on selected elements of the water cooled furnace wall, which further reduced thermal losses during the melting process.
In Germany the potential of these measures regarding the annual savings of electrical energy are estimated to roughly 650 million kilowatt hours. The increased yield of iron and alloys from scrap metal means a reduced consumption of this raw material of around 160,000 to 200,000 tons per year. Added to this are savings of deoxidation and alloying agents of around 16,000 to 25,000 tons.