Refluxes and Difference Points

FIGURE 6.19 Magnified view of CSk-t-i and CS with all stream definitions and a component balance for a generic sidestream wididrawal. 

FIGURE 6 Geometric representation of movement for a sidestream wididrawal column with the side products located (a) above and (b) below die feed stream. 

Assuming that only liquid products are being drawn off, it is also possible to obtain a qualitative understanding of the effect of sidestream withdrawal on the reflux ratio. Each liquid withdrawal increases the net flow from one CS to the next, as the quantity V —L becomes larger. 

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Having determined aU the product compositions and flowrates allows one to also determine all the refluxes and difference points of the entire column, and the design can commence with the same basic procedure as simple columns. We simply have to integrate from the sidestream composition and see whether there is an intersection with the profile of the remaining CS. To summarize this procedure and put it more clearly, a stepwise procedure is shown below ... 

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