Batch process control can seem like another world compared to continuous process control. In batch operations, process conditions are constantly changing and control loops are going in and out of service. PID control may take a back seat to sequential scheduling of manipulated flows.
What if you could use at-line analyzers and even off-line analyzers for control of batch and continuous processes without the need to retune the PID despite long and variable cycle times? What if the lab analyzers could be used for closed loop control without having to be concerned about the...
Batch processes pose particular challenges for closed-loop control and optimization due to inherent process nonlinearity and non-self-regulation. At the same time there is a greater potential for increasing capacity in batch than in continuous processes. Solutions need to address the interrelationship between yield, capacity, quality, and repeatability.
The highest value added products use batch operations. Batches can take days to complete and be worth millions of dollars. In many cases bad batches cannot be fixed downstream. Bad batches must be avoided. There are many techniques for making batches more repeatable and faster by better monitoring and control.
If there were no unmeasured disturbances, feedback control would not be necessary. Process engineers and operators could home in on the best PID output and just leave it at this value. In fact many process engineers are much more comfortable with setting a stream flow per a process flow diagram...
What configuration changes to control strategies can readily take advantage of improvements in measurements and final control elements? Control strategies can inherently improve production rate by maximizing feed and efficiency by enforcing material and energy balances.
When we saw an increase in production rate needed during opportunity assessments at Monsanto and Solutia, we would salivate. Impressive results could be obtained in a matter of a few days by a simple change in setpoint, tuning, and/or configuration.