1.5b. Material balances around an ammonia gas absorber.
A gas stream flows at the rate of 10.0 m3/s at 300 K and 102 kPa. It consists of an equimolar mixture of ammonia and air. The gas enters through the bottom of a packed bed gas absorber where it flows countercourrent to a stream of pure liquid water that absorbs 90% of all of the ammonia, and virtually no air. The absorber vessel is cylindrical with an internal diameter of 2.5 m.
a) Neglecting the evaporation of water, calculate the ammonia mol fraction in the gas leaving the absorber.

Solution:
Basis: 1 second
A = ammonia B = air
b) Calculate the outlet gas mass velocity (defined as mass flow rate per unit empty tube cross-sectional area).

Solution:
1.6b. Velocities and fluxes in a gas mixture.
A gas mixture at a total pressure of 150 kPa and 295 K contains 20% H2, 40% O2, and 40% H2O by volume. The absolute velocities of each species are -10 m/s, -2 m/s, and 12 m/s, respectively, all in the direction of the z-axis.
a) Determine the mass average velocity, v, and the molar average velocity, V, for the mixture.

Solution
Molar average velocity, V
Mass average velocity, vm

Basis: 1 kmole of gas mixture
b) Evaluate the four fluxes: jO2, nO2, JO2, NO2.

Solution: