Increasing of energy efficiency of electric arc furnaces in the contest of decarburization of steel production in Ukraine.
Authors: S. TIMOSHENKO ,   State Institution of Higher Education Donetsk National Technical University, O. SMIRNOV , Oleksandr KOLLAROV , Eduard NIEMTSEV ,   Physical Technical Institute of Metals and Alloys of National Academy of Science of Ukraine,   State Institution of Higher Education Donetsk National Technical University,   State Institution of Higher Education Donetsk National Technical University
Published: July 2024

The EU green deal policy envisages the gradual decarbonization of metallurgy through the priority development of hydrogen technologies for iron recovery and electrical steelmaking. Increasing the energy efficiency of electric arc furnaces (EAF), as a powerful (up to 100-150 MW) consumer of electricity, against the background of an average thermal efficiency of 75%, is an urgent task. The method of numerical modeling provides an assessment of energy-efficient EAF solutions based on the improvement of the workspace geometric parameters. The solutions consist in reducing the form factor of the steel melting bath from the traditional 5.0-5.5 to 2.5-1.8 at a given capacity of the arc furnace and increasing the relative electrodes pitch diameter from the traditional 0.2 of inside frame diameter by approximately two times. The greatest effect of the "deep" bath is achieved in the "flat bath" process due to the features of charging and in DC EAF due to one electrode scheme and consists in reducing radiation heat losses by 49 and 20%, respectively. In the conditions of forced mixing, a "deep" bath makes it possible to reduce the time of steel heating to tapping temperature by 12-16% with corresponding energy savings. In the "deep" bath of DC EAF, the mixing power increases by 1.3-8.4 times compared to the basic bath, which will reduce the heat time by 9- 10% and save up to 70-80 kWh/ton. Optimizing the electrodes pitch diameter increases the relative time of the most energy-efficient stage of melting the charge in the wells. Because of the change in the melting regime, electricity savings of 2.5-7.5% within the energy period are expected, more pronounced in large-tonnage (120-250 ton) AC EAF. The assessment of the energy efficiency of modernizing the geometry of the workspace of the EAF as a whole, taking into account the specifics of the influence of bath parameters (technology period) and electrode decay (energy period) is expected to be at least 10-12% for 100-120 ton AC EAF. The concept of modernization of foundry class EAF with a capacity of 6-12 tons is substantiated, which consists in increasing the specific electrical power by approximately two times due to a corresponding reduction in capacity while maintaining productivity. A special solutions for given EAF are mainly aimed at reducing energy losses due to the accumulation of heat by the refractory lining due to its local replacement with water-cooled elements with increased thermal resistance. With the available power transformer, the specific power of the furnace increases to 1 MW/ton, which, thanks to the intensification of heat exchange processes in the "deep" bath, ensures quantitative and qualitative production indicators with lower heat losses compared to basic units, and reduces electricity consumption within 75 kWh/ton.