Batch Processing

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Published on Friday, 20 May 2011 13:03

Batch processes have always been difficult to keep under control due to the number of quite different operations performed in sequence in the same equipment and using the same measurement transducers. But the temperatures that are normal when charging the vessel with reactant initially are very different to those that are normal in a reaction phase and different again from those that are normal in a crystallisation or distillation phase. Engineers have struggled to understand these processes largely because they have been limited to time-trend graphs of perhaps a dozen individual variables such as reactor temperature or pressure displayed on an overlaid set of scales and with so much visual clutter that only one batch can be seen at a time.

C Visual Explorer (CVE) graphs allow many batches to be superimposed so that their operating envelopes can be compared and a normal operating envelope can be defined from the best batches. There is no practical limitation on the number of variables so it is easy to introduce the phase number or step number as a variable and CVE will then calculate times from the start of each phase as well as from the start of a batch. Now it is easy to compare the operating envelopes of batches and of individual phases for insight and understanding of your batch process as never before.

The solution is using a unique, patented technology known as Geometric Process Control (GPC). It is unique in its ability to enable analysis and understanding of complex multi-phase and multi-stage batch processes. This is because it allows many batches to be compared at the stage, batch, phase, step and variable level. This arises from its ability to handle many variables and to focus on particular subsets such as a single phase across many batches as well as from its ability to show and compare the operating envelopes for achievement of end-of-stage and end-of-batch objectives.

It does this by extracting the best operating experience of the past to define 'Best Operating Envelopes' (also called ‘Best Operating Zones’). These are turned into real-time models by 'shrink-wrapping' the cloud of points from the past where the objectives were previously achieved to create a model of the envelope of the cloud. The system then guides the process operator to stay inside the envelope and can optimise further by steering towards sub-spaces within the envelope where secondary objectives can also be achieved. For multi-phase batch processes, the technology can automatically find individual envelopes for each phase from the phase number variable provided by the system. It is a truly unique offering to the batch process industry and is a breakthrough in truly understanding these complex processes.

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