The prediction of the outermost trajectory of media in a grinding mill for lifter bars with rounded or worn profiles

This thesis presents the analysis of the path of a ball on the inside of a ball mill for lifter bars with rounded or worn profiles. The model predicts the response of a single ball with particular reference to the balls trajectory after departure from the lifter bar and incorporates the effect of friction, mill rotational speed, lifter height as well as different lifter bar profiles. The out of plane travel of the particles are ignored and hence the system is reduced to a two dimensional problem. A set of experiments were performed on a model perspex mill in order to obtain data by which the theory could be compared. The lifter bar is analysed using a parabolic expression which allows the shape to be changed to model various stages oflifter wear. Two possible formulations are investigated in determining the motion of the particle on the lifter bar. The first formulation assumes the ball to roll on the lifter bar until a limiting friction is reached after which the ball will slide along the lifter. The second formulation considers the ball to have a pure sliding motion on the lifter.

Grantor dc:publisher.institution

Department of Mechanical Engineering

Year dc:date.issued

1997

Author dc:creator

• Milner, Andrew Leigh

Advisor dc:contributor.advisor

• Nurick, Gerald N

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/11427/21702

OAI identifier oai:identifier

oai:open.uct.ac.za:11427/21702