Transfer Aspects of Electric Through-Type Furnaces for Heat Treatment of Stone-Cast Ware to Gas Heating

The final formation of the quality indicators of stone-cast samples occurs under heat treatment in heating furnaces comprising two tunnel kilns: a drying-calcining kiln for casting equipment preparation for pouring with liquid melt and a crystallization-tempering kiln for internal stress relief in the structure of castings. Six high-speed burners of the Vikhr 25 SV-5 type, inlet and outlet vestibules, gas extraction from the furnace, a heat exchanger for heating air for combustion, and an air duct system should be installed to facilitate the transition of an electric drying-calcining kiln to gas heating. In the crystallization zone, the arch height to 100 mm from the poured products with a uniform placement of electric heaters along the entire length of the zone should be reduced, and additional thermal insulation from fibrous tile materials with a thickness of at least 50 mm should be installed on the outer surface of the crystallization zone. In the annealing zone, cold air is supplied from a separate fan at a flow rate of up to 1400 m³/h at a pressure of at least 421.49 Pa through a transverse collector and eight distributed tuyeres with cutoff gates. While maintaining the quality of the products obtained, such a change in the complex design of tunnel kilns is accompanied by efficient heat utilization with the possibility of increasing thermal efficiency by 3.28 times, raising total energy consumption by 22.58%, and forming an additional volume of discharged gases of no more than 4000 m³/h with a temperature not exceeding 150°C.