Improving the Gas-Exhaust System at Foundry Electrofurnaces

Abstract

Inspection of the gas-exhaust system at arc furnaces of capacity 3–10 t in the casting shops of man-ufacturing enterprises reveals problems responsible for copious gas and dust emissions in the production buildings, with degradation of the air quality. This is mainly associated with structural shortcomings of the systems for gas and dust evacuation from the furnace chamber through the exhaust channel, working window, and gaps between the housing and roof and also between the edges of the holes in the upper section and the electrodes within the holes. In particular, the moving joints between the rotary hoods and the gas-exhaust lines in such systems do not ensure reliable sealing. Accordingly, an improved design of the hood-rotation mechanisms has been proposed, with two sand barriers preventing the atmospheric emission of harmful emissions between the moving components. In the design of an industrial prototype, a method is developed for calculating the energy parameters of the drive in the improved system. A 1:10 scale model of the system is built to check the design and the theoretical equations. By means of a measuring system consisting of a ten-soresistive converter, an ac amplifier, an analog–digital converter, and a computer, the load on the model’s drive on switching from the working position to the rest position and back is determined, for two cases: with and without sand barriers to seal the mobile components. The drag in the two sand barriers on rotation of the moving element amounts to 20–26% of the total load on the drive, depending on the angular velocity of the cantilever with the hood. According to the theoretical formulas, this figure is 17–23% for hood-rotation mechanisms in arc furnaces of capacity 3–10 t. Video recordings of the smoke fluxes from the model through the gaps between its housing and the roof during simulations of steel production confirm the reliability of the sand barriers, which ensure complete sealing of joints in the hood-rotation mechanism. Practical use of the proposed design improves gas–dust evacuation from the working zone of smelting furnaces used in the foundry.