Re: Mixed process dynamics in DMC

Posted by Adrian Meaburn on August 30, 19101 at 12:29:22:

In Reply to: Re: Mixed process dynamics in DMC posted by Mike McCarty on August 10, 19101 at 11:06:21:

I inherited some RMPCT models for a reactive distillation column which
appeared to exhibit mixed dynamics. I am now retesting the plant as I am not
sure about them. The root of the problem is that the process is very slow
and is very difficult to test effectively using standard steps (i.e. 24hr
testing). Preliminary data from the prbs suggests that the original models
were flawed and the process does not contain these mixed dynamics.

The impression I get is that mixed dynamics are not a common occurrence on
process equipment. However, I have seen this mixed behaviour once before on
another of our process process but have not had to deal with it directly as
the DMC controls work well when separated (a legacy of RMPCT). This is a
process consisting of a stripping column attached to a reactive system with
large recycles. I am confident of the models as the controls work very well
but unfortunately cannot go into too much detail as this process is
proprietary.

Adrian

Follow Ups:

• Re: Mixed process dynamics in DMC Dan O'Connor 17:52:53 11/09/101 (1)
  • Re: Mixed process dynamics in DMC Sean Goodhart 18:24:51 11/14/101 (0)

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Comments:
: I inherited some RMPCT models for a reactive distillation column which
: appeared to exhibit mixed dynamics. I am now retesting the plant as I am not
: sure about them. The root of the problem is that the process is very slow
: and is very difficult to test effectively using standard steps (i.e. 24hr
: testing). Preliminary data from the prbs suggests that the original models
: were flawed and the process does not contain these mixed dynamics.

: The impression I get is that mixed dynamics are not a common occurrence on
: process equipment. However, I have seen this mixed behaviour once before on
: another of our process process but have not had to deal with it directly as
: the DMC controls work well when separated (a legacy of RMPCT). This is a
: process consisting of a stripping column attached to a reactive system with
: large recycles. I am confident of the models as the controls work very well
: but unfortunately cannot go into too much detail as this process is
: proprietary.

: 
: Adrian


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