Ural Federal University named after the first President of Russia B. N. Eltsin, Ekaterinburg, Russia:

B. P. Yuryev, Associate Professor, Candidate of Engineering Sciences
V. A. Goltsev, Associate Professor, Candidate of Engineering Sciences, v.a.goltsev@urfu.ru

Industrial tests on asbestos ore drying are carried out in shaft furnaces having different modes (counterflow and combined parallel flow-and-counterflow) of flows of coolant and treated material at Uralasbest Mining and Processing Works. In the combined mode furnace, some quantity of gases is fed from the furnace extension to bypass to upper part of the shaft. During the tests, the temperature and humidity of ore along the height and in the cross-sections of the shaft, as well as the gasdynamic characteristics of coolant were measured both in case of the counterflow and the combined parallel flow-and-counterflow modes of furnaces. For the combination mode, the tests were performed at varied opening of the bypass. It is found that when the bypass is closed, which agrees with the counterflow mode of furnace operation, efficiency of drying remains the same at the halved height of layer despite the increased humidity of the ore feedstock. When the furnace operates in the parallel flow-and-counterflow mode, nearly 30% of the top of the layer has no humidity gradient. With a view to reducing cold air inleakage at the top of the combination parallel flow-and-counterflow furnace, it is expedient to equip the top of the shaft with a chance cone with a parallel middlebody. At the charge point, it is necessary to install several layers of curtains made of tough rubber. In the section between the feed drum and discharge hopper, an air curtain can be placed to return entrained ore fines to the shaft furnace. The balance sheets on fl ow rates of air and air-gas mixture enable comparing the operating modes of shaft furnaces and evaluating their thermal performance.

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