Saint Petersburg State Institute of Technology, Saint Petersburg, Russia:

I. V. Domanskiy, Professor

LLC “RUSAL Engineering-Technical Center”, Saint Petersburg, Russia:
I. V. Davydov, Department Director, e-mail: ioan.davydov@rusal.com
M. N. Malofeev, Senior Researcher

Concentrating of various slurries is an integral part of alumina production process. It is carried out in thickeners, equipped with the devices comprising the drive connected to vertical shaft. Handling beams are radially attached to the shaft. Paddles (plates) are fastened to the shaft at specified pitch and incidence angle designed for gentle mixing of thickened slurry while transferring it to the discharge sleeves. By physical properties, these slurries are Bingham fluids (i. e. they possess effective viscosity) and the paddles are streamed around in laminar mode. One of the crucial indicators of the equipment efficiency is power consumption for agitation and transfer of thickened slurry. Very little information on calculation of resistance for the stream around the paddles in laminar mode is available even for Newtonian fluids. The paper introduces the calculation method for power consumed by the drive of the thickener during the agitation and transfer of Bingham fluids. Normally power required for the specified processes is N = M(π·n)/30. М = М_n + M_t is total power rotation torque applying to paddles (plates) in Nm. For Newtonian fluids, (М_n) is a resultant rotation torque of perpendicular force (N_m).

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