Removal of Fine Particles in Ores for Blast Furnace by Pneumatic Classifier of Horizontal Type

Abstract

A pneumatic classifier of horizontal type is used instead of the wire sieve in order to eliminate fines in ores charged into blast furnace. The former is very convenient because it is free from troubles such as choking of the meshes and the breakdown in the case of the wire sieve. The removal of fines in sintered ores with increasing the mixing ratio (feed quantity to air quantity) was experimentally and theoretically examined in consideration of the scattering of the apparent specific weight and drag coefficient for the particles.
The results obtained are as follows:
(1) The classification is effectively carried out in when a distinct difference in horizontal travelling distance according to particle size can be made, even if the apparent specific weight and drag coefficient scatter in some extent.
(2) With increasing the mixing ratio, the classification accuracy is lowered due to increasing of the collision frequency among the particles within the classification region. It is possible to avoid to some extent by thinning the thickness of feed particle bed.
(3) The removal of fines is considerably successful by decreasing the cross section area of duct and increasing the air velocity in the case of classifing under condition of the same feed quantity and the same air quantity.
(4) For the increase of the mixing ratio, it is practically economical to shorten the height of the duct and to make a calm zone within the classifing region without lowering the classification accuracy remarkably.