Estimation of the breakage function of a roller mill crushing quartzite
Loading...
Authors
Tshinguz, Grace Mulolwa
Issue Date
2020
Type
Dissertation
Language
en
Keywords
Roller mill , Quartzite , Breakage matrix , Breakage function , Assumption of non-normalization , Milling-ratio
Alternative Title
Abstract
Studies on the breakage function of roller mills are limited. The approach of using breakage
functions adapted from other milling systems has been previously used to model the breakage
of laboratory roller mills.
However, in most cases this approach has been found to be inadequate because the assumption
of normalization used for modelling other milling systems may not apply to roller mills.
This study assumes the non-normalization of the model for roller milling. It aims to define the
breakage function of roller milling of quartzite and to develop a predictive model for first
breakage for a laboratory roller mill.
Six size fractions of quartzite were prepared using a Jaw Crusher for primary breakage of a
quartzite feed material. The product from the crusher was split into narrow size ranges using a
sieve shaker. Each size fraction was in turn split into three samples, which were then fed
separately to the roller mill, using a different roll gap for each sample. A breakage matrix for each
roll gap size was then generated from the product size analysis of the sample. Using the
cumulative passing and the milling ratio, the analysis of the three breakage matrices led to the
definition of the breakage function. The coefficients of the breakage function were curve-fitted,
in order to develop a predictive model.
The results indicate that the assumption of non-normalization is appropriate for roller milling of
quartzite rock. The breakage function follows a log-normal trend for all the feed size fractions
used, and the coefficients of the breakage function can be fitted by polynomial functions of
second degree of the feed size. Further research is needed to investigate the correlation of the
breakage function and the product size.