Cereals processing technology

Wheat, corn and coarse grains milling 37
Technology exists today that can measure most process control properties online
and in real time. This technology centres on the use of NIR techniques, but
X-ray fluorescence and gravimetric methods are also emerging. However,
confidence levels in these technologies are not yet sufficient to allow an increase
in plant operators’ dependence on on-line control for functions other than
protein addition and open loop control of other parameters. The main difficulty
is the concept of establishing sufficient calibrations that are verified regularly.
However, the work documented by Graf (1994), Fearn and Maris (1991) 14 and
others are examples of the developments that are beginning to bring process
plants closer to the goal of producing a mill that can be controlled intelligently.
3.6 Automation and its role within the milling industry
Liveslay and Maris (1992) performed a survey on the use of Computer
Integrated Manufacturing (CIM) and Programmable Automation (PA) in the
milling and baking industries. The conclusions were that:
• the milling and baking industries have a small number of examples of mature
CIM developments, namely automation and manning reduction
• the number of such developments is likely to increase, although slowly
• much of the industry remains unconvinced about the benefits of CIM and PA
• it is possible to demonstrate some specific benefits that CIM and PA will
bring to the industry.
The benefits of CIM include quality improvement and enhanced production
control. Many CIM processes also have features that enhance hygiene aspects of
the process. In addition, data collection and analysis as well as product
traceability are built-in features of CIM that are readily exploited by processors
to ensure optimum quality for customers and as tools to enhance profitability.
Improving control saves energy and improves product consistency by
ensuring key process variables are more stable, thus allowing comfort margins to
be reduced. Processes may also be operated closer to optimum values or
constraints (Hart et al. 1996). In many cases a simple control system will
achieve the desired effect but others require a more sophisticated approach.
Advanced techniques are required in a number of situations. Highly
integrated processes, with many interacting elements, for example, mill
processes, cannot be controlled satisfactorily by basic control systems. In
addition simple controllers find it difficult to cope with significant time delays
between controller actions and system responses and non-linear responses from
the process. Finally, advanced controllers are required where the process is
expected to be flexible; for example the process plant may produce different
products, requiring operation at different throughputs.
14 The applications examined were the automatic control of gluten addition to flour and a miniature
gravimetric sensor designed to measure the release of material from a milling passage.