Regulatory use of pressure compensating temperatures.

Name    : 
E-Mail  : 
Subject : 

Comments:
: I have used pressure compensated temperatures on the regulatory level only one time (other than that mentioned by Dan and Doug.)  The process was a 2-cut splitter, between C6 and C7 raffinate hydrocarbons at the back of a CCR reformer.  The column operated under vacuum and had a pressure controller with a valve on the process side of the ejector.  The ejector pressure was subject to frequent, high-frequency disturbances due to flare-line and steam header pressure changes.  

: Our original plan was manipulate the pressure setpoint and tray temperature in the upper part of the column to minize pressure and keep overhead quality on target.  Partway through the test,  we realized that we could better minimize pressure by just keeping the process valve to the ejector (pressure control valve) wide open all the time. (The client confirmed there was never any time they wanted to throttle the vacuum).  Pressure was not under control now and was just a disturbance.   To  keep the  controller from chasing high-frequency disturbances we pressure compensated the regulatory tray temperature controller.  It worked quite well in this situation.  It also allowed the same regulatory configuration to be more effective if the overall APC was off.

: I have only used regulatory-level pressure compensation twice so far, although technically it seems there is no reason why it couldn't be more widely applied.  I find that some operaters are slightly confused by the general idea of pressure compensation; perhaps this is a negative point for using it consistently on the regulatory level.  If I could generalize on the situation where I would use regulatory-level pressure compensation, it would be where there is some sort of unpredicted pressure disturbances to the process, especially when the disturbances are high-frequency.


Optional Link URL:  
Link Title:         
Optional Image URL: