These equations are similar to Eqs. (7-16) and (7-17), and the same considerations relative to the constancy of molal rates of vapor and overflow apply in this case.
3. General Case. The derivations given in the two previous sections were for the case with no side streams, but the general case is similar.
In the system shown in Fig. 7-15, the over-all and component material balances above plate a are
Oa+1 - overflow rate from plate a + 1 N = net mols leaving section — Va — Oa+l Va, xa+i = mol fractions
Nxn = total mols of component leaving section other than with Va and Oa+i The enthalpy balances are
where Ha = molal enthalpy of vapor entering plate a + 1
ha+i = molal enthalpy of liquid leaving plate a 4- 1
NM = net enthalpy removed from the column above plate a + 1 For Fig. 7-15,
N=Lx+L2 + D- F NKn = Li(hL)i + L2(hL)2 + DhD — FhF + Qc + losses
These equations can be combined to give
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