Relative Volatility Of Ammonia In Water

NHa balance,

0.209(100) « 0.98D -f 0.001(100 - D) D « 21.25 and W « 78.75

An enthalpy balance on the exchanger between the bottoms and the feed is

Feed 20 wgf. 7oNHs

Feed 20 wgf. 7oNHs

Fig. 7-20. Flowsheet for ammonia-water example.
Fig. 7-20a. Enthalpy-composition diagram for ammonia-water example.

where ts ** temperature in reboiler = 211.2°C. hp — enthalpy of feed entering tower

Cv - heat capacity of bottoms « 19.0 cal. per g. mol/°C. (used same as

Cp of H20 at 20 atm.) hA0 - enthalpy of feed at 40°C. « -3,180 78.75(19.0) (211.2 - 45) - 100(^+3,180) hF as —690 cal. per g. mol This point is located on the enthalpy-composition diagram (Fig. 7-20a). Utilizing the y,x diagram it is found that the equilibrium tie line that passes through this point corresponds to x - 0.193 and y » 0.70. The extrapolation of this tie line to zd - 0.98 gives Md - 10,230 and at xw - 0.001, Mw - -3,630. Also

Assuming that h= enthalpy of saturated liquid, and using Vt by a derivation similar to that for Eq. (7-16),

Or D

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