Cereals processing technology

48 Cereals processing technology
to examine scientifically the phenomena at work in roller mills and to optimise
this operation subsequently.
Campbell and Webb (2000) have taken the breakage matrix approach to
modelling comminution operations and applied it to the roller milling of wheat
in the flour milling process. This work demonstrates conclusively that flour
milling operations can be modelled using discrete mathematical methods.
Owens (2000) built on the work mentioned above in an effort to develop an
integrated optimisation technique for flour mill processes.
3.8.5 Conclusion
Process optimisation is a large and complex area, with many possible options
from which to choose the best solution to a particular problem. The findings of
this review are as follows:
• Optimisation of milling operations to date has been simplistic and focused on
macro models of the process. No attempt has been made to optimise the
process in a calculated fashion.
• The basic framework for optimisation already exists in many mills, namely
DCS and/or SCADA systems.
• There are many advantages to be gained from the successful application of
process optimisation, all of which are profitability enhancing.
• PID feedback control is the accepted control method in milling at present, but
this form of control is not suitable for whole process optimisation.
• Simulated Annealing, Genetic Algorithms and Rule-based control would
appear to be the systems of choice for an advanced control system in mills.
This is because the former two are combinatorial optimisation methods that
can operate with many different data set types and even discontinuous
functions. The latter system could be employed to incorporate the
considerable experience base present in operating mills.
• Reyman’s (1992) summary lists the steps that need to be taken to enact an
advanced control system. There are currently some gaps in the milling
knowledge base that need filling. These gaps include the lack of a global
performance strategy for mills, the almost complete absence of process
models and dynamic modelling simulations and very little formal understanding
of the behaviour of the process. Reyman (1992) also stated the
importance of process instrumentation for reliable operation of advanced
control systems.
3.9 The future
The aspects of milling discussed highlight the way in which this sector of the
cereals processing industry has developed to date and may develop in the future.
Developments in machine capacity have been dramatic, but progress in this area