Question

A wastewater stream is introduced to the top of a mass-transfer tower where it flows countercurrent to an air stream. At one point in the tower, the wastewater stream contains 1× 10-3 g mol A/m3 and the air is essentially free of any A. At the operating conditions within the tower, the film mass-transfer

At the operating conditions within the tower, the film mass-transfer coefficients are kL =5×10 kg/mol/m s.(kgmol/m) and kG =0.01kgmol/m .s.atm.The

concentrations are in the Henry’s law region where pA,i = HcA,i with H = 10 atm/(kg mol/m3). Determine

a) The overall mass flux of A.

b) The overall mass-transfer coefficients, KL and KG.

Answer #1

A gas stream contains 4.0 mol % NH3 and its ammonia content is
reduced to 0.5 mol % in a packed absorption tower at 293 K and
101300 Pa. The inlet pure water flow is 68.0 kgmol/h and total
inlet gas flow is 57.8 kgmol/h. The tower diameter is 0.747 m. The
film mass-transfer coefficients are k’ya=0.0739 kgmol/s.m3 .molfrac
and k’xa= 0.169 kgmol/s.m3 .molfrac. Using the design methods for
dilute gas mixtures,
(a) Calculate the tower height using k’ya.
(b)...

In the absorption of component A (molecular weight = 60 g/mol)
from an airstream into an aqueous solution, the bulk compositions
of the two adjacent streams at a point in the apparatus were
analyzed to be PA,G = 0.1 atm and CA,L = 1
kmol of A/m3 . The Henry’s Law constant was 0.85
ATM/mole fraction. The overall gas coefficient was KG =
0.27 kmol/m2/h/ATM. If 60% of the total resistance to mass transfer
resides in the gas film, determine:...

1) A nozzle is a device for increasing the velocity of a
steadily flowing stream of fluid. At the inlet to a certain nozzle
the enthalpy of the fluid is 3025 kJ/kg and the velocity is 60 m/s.
At the exit from the nozzle the enthalpy is 2790 kJ/kg. The nozzle
is horizontal and there is negligible heat loss from
it.
(i) Find the velocity at the nozzle exit.
(ii) If the inlet area is 0.1 m2 and specific volume...

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