Chapter 5, Problem 5.60P

Two humid gas streams are combined in a heated mixing chamber. The first stream contains 23.5 moIe ethane and 76.5 ethylene on a dry basis and enters the chamber at 25°C and 105 kPa at a rate of 125 L/min. The second stream is humid air, which enters at 75°C and 115 kPa at a rate of 355 L/mm. The product stream emerges at 65°C and 1.00 atm. A hygrometer is used to measure the water contents of the two feed streams and the combined product stream. The calibration curve for the hygrometer is a straight line on a semilog plot of y (mole fraction of water) versus R (hygrometer reading), which passes through the points $\left(y={10}^{-4},R=5\right)$and $\left(y=0.2,R=90\right)$. The following readings are recorded.

Hydrocarbon Feed Stream: R = 86.0

Air Feed Stream:

R = 12.8

(a) Derive an expression for y(R).

(b) Calculate the volumetric flow rate of the product stream and the molar composition of the product gas on a dry basis.

(c) Calculate the partial pressure of water in the product gas and the hygrometer reading for this stream.