Levels

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Posted by Graeme Taylor on April 02, 2001 at 16:41:21:

Can anyone give me their thoughts/experiences on the following?

I am currently working on a crude unit DMC where we have the atmospheric level as a dependent variable. The data shows a clear model for the lowest pump back reflux to the atmos level, as would be expected (lowest sidestream is total draw). Also the data shows good relationships to dependent variables in the vacuum overheads for moves in this reflux. Should all these relationships be included in the final model?

I think that including all these relationships will lead to the controller over predicting the impact of moving this pump back reflux, as the controller will see a requirement to move the vacuum feed as well to balance the level. The controller will predict the move in the vacuum feed to have impacts throughout the entire tower (due to the model being developed for the average feed quality in the test), where as in reality the increase in vacuum feed will be solely vacuum overheads material.

What is the “accepted” solution here, include all the models or not?

Follow Ups:

Re: Levels Don Snowden 00:27:01 4/11/01 (0)
Re: Levels Dan O'Connor 19:25:46 4/10/01 (1)

Re: Levels Graeme Taylor 16:28:29 4/22/01 (0)

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: Can anyone give me their thoughts/experiences on the following?

: I am currently working on a crude unit DMC where we have the atmospheric level as a dependent variable.  The data shows a clear model for the lowest pump back reflux to the atmos level, as would be expected (lowest sidestream is total draw).  Also the data shows good relationships to dependent variables in the vacuum overheads for moves in this reflux.  Should all these relationships be included in the final model?	

: I think that including all these relationships will lead to the controller over predicting the impact of moving this pump back reflux, as the controller will see a requirement to move the vacuum feed as well to balance the level.  The controller will predict the move in the vacuum feed to have impacts throughout the entire tower (due to the model being developed for the average feed quality in the test), where as in reality the increase in vacuum feed will be solely vacuum overheads material.  

: What is the “accepted” solution here, include all the models or not?

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