Concern for the environment and rational management of resources requires the development of recoverable methods of obtaining metallic materials. This also applies to the production of aluminium and its alloys. The quality requirements of the market drive aluminium producers to use effective refining methods, and one of the most commonly used is blowing an inert gas into liquid aluminium via a rotating impeller. The efficiency and cost of this treatment depends largely on the application of the correct ratios between the basic parameters of the process, which are the flow rate of the inert gas, the speed of the rotor and the duration of the process. Determining these ratios in production conditions is expensive and difficult. This article presents the results of research aimed at determining the optimal ratio of the inert gas flow rate to the rotary impeller speed, using physical modeling techniques for the rotor as used in industrial conditions. The tests were carried out for rotary impeller speeds from 150 to 550 rpm and gas flow rates of 12, 17 and 22 dm3/min. The research was carried out on a 1:1 scale physical model, and the results, in the form of visualization of the degree of gas-bubble dispersion, were assessed on the basis of the five typical dispersion patterns. The removal of oxygen from water was carried out analogously to the process of removing hydrogen from aluminium. The curves of the rate of oxygen removal from the model liquid were determined, showing the course of oxygen reduction during refining with the same inert gas flows and rotor speeds mentioned above.

Environmental Research Department Institute of Technology and Business in České Budějovice Okružní 517 10 370 01 České Budějovice Czech Republic

Faculty of Materials Engineering Silesian University of Technology Krasinskiego 8 40 019 Katowice Poland

Faculty of Mechanical Engineering University of West Bohemia Univerzitní 2732 301 00 Plzeň Czech Republic

MOTOR JIKOV Slévárna a s Kněžskodvorská 2277 370 04 České Budějovice Czech Republic

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Assessment of refining efficiency during the refining cycle in a foundry degassing unit in industrial conditions