Column-Base Level Control Via Feed Flow Manipulation

Note that contains K c and is inversely proportional to it. Some idea of the magnitude of Ksc may be obtained by assuming as an example T -Tr = 100°C, X = 100 pcu/lb, and Cp = 0.5 pcu/lb°C. Then Ksc = 1-5-Subcooling therefore can have a significant effect on T . 

5 COLUMN-BASE LEVEL CONTROL VIA BOTTOM-PRODUCT 

This is usually a fairly straightforward system to design since it fits the analysis of Section 16.2. me of the practical details are discussed in Chapter 4. For most applications one should make Th 10 minutes. 

For this case the simple analysis of Section 16.2 must be extended to take into accoimt the lags between the column feed point and the column base. Let us suppose that there are n trays between these two points and that hydraulic lag of each tray is first order with a time constant Ttr (see Chapter 13). Typical values are in the range of 3-8 seconds. It has been shown elsewhere (Chapter 12 of reference 1) that a number of equal lags may be approximated by dead time  

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Column-Base Level Control via Feed Flow Manipulation... 

Signal flow diagram for proportional-oniy column base level control via feed flow manipulation... 

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