Internal Mass Balance Column Section Interaction

2 Internal Mass Balance Column Section Interaction 

By assuming that the vapor portion of the feed mixes only with the vapor streams in the column, and likewise for the liquid, a mass balance for the vapor streams around this section gives (subscripts S and R indicate stripping and 

FIGURE 5.10 The feed stage of a simple distillation column. 

Using all the definitions given in Equations 5.15 5.18 and rewriting them in terms of a reflux ratio in the stripping section, yields Equation 5.19 

It is also useful to note that the generalized reflux in the rectifying section, R r, reduces to exactly the classical reflux ratio of r = IJD. However, the reflux ratio in the stripping section, is almost always expressed as a reboil ratio in classical column design as 5 = V B. In this case, the relationship between the classical parameter and our generalized one is given as R/ s = — 5 — 1. 

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