IN RESPONSE to requests from managers in overseas factories, a number of
technical benchmarks have been developed and applied to a number of factories,
including those involved in the manufacture of refined and sulphited white
sugars, as well as of raw sugar. These benchmarks are presented and discussed
in this paper. An expression for the overall pol recovery in sugar, modified from
the Australian CCS formula, has been used as a useful benchmark value
applicable to all factories. A related formula for expected losses can be used as a
benchmark for the pol losses % pol in cane. Benchmarks for the individual
losses of pol in bagasse and in filter cake are described. These are based on
available regression expressions for ‘good practice’ performance, and, in
addition to the composition of the cane, these take into account the availability
of imbibition and wash water to the process as well as the number of crushing
mill stages and the rotary filter area. The benchmark loss in final molasses
requires that benchmark values for these upstream losses be known before the
flow to final molasses can be calculated. For this calculation, the apparent
disappearance of impurities during processing has to be allowed for,
interconversions made between true and apparent purity analyses, and
benchmark purity values for final molasses need to be obtained from selected
exhaustion formulae. The benchmark calculations could be packaged into a
spreadsheet program which can process laboratory information data and produce
appropriate plots of actual and benchmark data for each operating period. The
techniques are presented in the hope that they might enable factory performance
to be more critically analysed and better understood by management and
technical staff.