Page 258 - Separation process engineering

(6-29a)

For 2 ≤ j ≤ N − 1

(6-29b)

and for j = N

(6-29c)

The coefficients in Eqs. (6-29) require knowledge of the enthalpies leaving each stage and the Q values.
The enthalpy values can be calculated since all x’s, y’s, and temperatures are known from the component
mass balances and the converged temperature loop. For ideal mixtures, the enthalpies are

(6-30a)

and

(6-30b)

where and are the pure component enthalpies.

(6-30c)

(6-30d)

They can be determined from data (for example, see Maxwell, 1950, or Smith, 1963) or from heat
capacities and latent heats of vaporization.
Usually the column is adiabatic. Thus,

(6-31)

The condenser requirement can be determined from balances around the total condenser:

(6-32)

Since D and L/D are specified and h and H can be calculated from Eqs. (6-30), Q is easily calculated.
D
1
2
For an adiabatic column, the reboiler heat load can be calculated from an overall energy balance.