Global trends stipulate the need to optimize existing assets while
reducing environmental impacts. This paper illustrates the
procedure that was followed to achieve such goals at one of the coal
burning flash dryer units at an Anglo American smelter. An indepth
study of the process and related literature led to the
development and installation of a revised control philosophy. This
system includes modifications to the existing regulatory control
structure as well as a hybrid rule-based and model-predictive
advanced process control (APC) layer.
Since commissioning of the APC, this flash dryer’s average
throughput has increased by more than 6%, despite higher feed
moistures. Furthermore, even though coal consumption has
increased slightly, operating efficiency has improved by close to 5%.
This was made possible by improving stability of the drying column
outlet temperature by approximately 40%, which in turn enabled
selection of a more optimal setpoint. Recent data has shown that
APC utilization now exceeds 95%. This is indicative of a successful
controller installation with good site acceptance. The same
philosophy has therefore since been rolled out to most of the other
flash dryers in the group.