One question this raises is what a continuous process really is! So let's look at a couple of real processes.
The first example is from the biotech world, the second from petrochemicals
Fermentation - there are some very large processes with fermentation at their core. Some use entirely batch whereby the fermentation is done and then the fermentation product is transferred downstream as a single batch. But there are others that run the fermenter continuously for as long as they can (many weeks) whilst periodically taking fermentation product out. Is this batch or continuous? They most certainly have recipes. And either way they spend a lot of time in a single controlled state that is essentially governed by control loops. I know of many such processes and both types use S88 oriented implementations.
The Unipol process. (A nice animation, note the batches appearing in step 6)
Much like the continuous version of the fermentation process this runs with a continuous feed but product is taken from the reactor in batches. Different grades of product can be made by changing the set points (recipe formula!) without shutting down. Is this batch or continuous? This process too spends much of it's time in a single controlled state that is essentially governed by control loops.
It is not really important. but ff the two, the fermentation processes I have seen are more complex, but in part this is due to CIP complexities. On the other hand the Unipol process has more complex control loops and higher level optimisation systems.
I suspect the petrochemical industry is right up 106's street and the biotech industry is not
So what will distinguish the sort of process (or is it industries?) that 106 is to be aimed at?
This is a key point that must be resolved at the meeting
Finally a note - there used to be a link to the Official ISA Part 5 Blog
But this is presently unavailable as controlengineering.com has closed. Supposedly it will return.
1 comment:
A great blog. It would be great if you could fix the link to the fermentation process.
One possible reason for use of batch and fed-batch processes over continuous processes for this unit operation is evolution. When culture are grown continuously mutants are selected which can reduce culture productivity or alter product quality. In saying that there are some possible models to guide and ISA106 model. Mammalian cell perfusion culture can operate for extended period (100s of days)
Regards
Ronan
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