SCALE-UP OF MIXING EQUIPMENT FOR SUSPENSIONS

Fundamental parameters for designing of mixing apparatuses for suspensions are the just-suspended impeller speed and power consumption necessary for off-bottom suspension of solid particles, usually determined experimentally in laboratory mixing equipment. These experimental results are necessary transfer from laboratory scale to designing mixing equipment. Scale-up rules for just-suspended impeller speed were reported by many authors, however published results have a large variety of scale-up criterions. The aim of this paper is to describe and objectify scale-up rules for just-suspended impeller speed by electrochemical measurement of its values in a wide range of mixing equipment sizes. Theoretical analysis was validated by electrochemical measurements of just-suspended impeller speeds for geometrically similar mixing equipments of various sizes (from a laboratory scale to a pilot plant). From experimental results it follows that dimensionless suspension characteristics Fr' = f(d(p)/D, c(v)) can be applied for calculation of just-suspended impeller speed in geometrically similar mixing equipment of various scale.