The Reactive Difference Point Equation

FIGURE 8.13 A magnified view of an RCS with stream definitions. 

Since there may be a change in the number of moles due to reaction, we cannot simply apply the constant molar overflow assumption as with nonreactive CSs. An overall molar material balance over the RCS thus yields 

Superscripts T and B signify the top and bottom of the RCS, respectively. In accordance with the conventional DPE, it is useful to define parameters X r and At, where the subscript T also denotes the top of the RCS  

Although it will become apparent in discussions that follow, it is useful to mention here that Xas where the subscript B denotes the bottom of the RCS. This is because vapor and liquid flowrates at the top and bottom of the RCS may not be constant as was the case with constant molar overflow CSs. This may be deduced from Equation 8.21. 

Using the definition of X t in Equation 8.23 and eliminating from Equation 8.21 through substitution of Equation 8.22 gives 

---