Experimental Platform Electric Furnace with Heating Elements Placed Under a Hearth Plate

In this study, a comparative analysis of the energy efficiency of platform electric furnaces with a movable hearth plate and various heating systems was performed. The upper heating unit was located above the hearth, and the lower one was located under the hearth. In experimental studies, a vermiculite concentrate (made in China) with a low degree of natural hydration was used in a pilot plant of an electric furnace with a heating system located under the platform hearth plate. The resulting indicator of the specific energy consumption of annealing, equal to 168 mJ/m 3 , can be improved by bringing the heaters close to the bottom surface of the hearth plate by 4 – 5 mm, a significant reduction of the working space under the hearth and a decrease in heat losses. In addition, due to the small ratio of surface area to cross-sectional area, the use of wire heaters instead of strip heaters enables to reduce power consumption and energy intensity of annealing by 44% and increases the specific energy intensity to 95 mJ/m 3 . The placement of wire heaters under the hearth plate enables to eliminate the sticking of large grains of expanded vermiculite in the annealing space and completely eliminate the burnout of heaters, which is the most important factor in increasing the reliability of such furnace units.