BITS PilaniPilani Campus

Separation Processes - I (CHE F244)

Subhajit MajumderFaculty

Department of Chemical engineering

BITS PilaniPilani Campus

Mass Transfer and DiffusionOverall & Individual Mass Transfer Coefficients17-02-2016

S Majumder | BITS Pilani, Pilani Campus3

In an experimental study of the absorption of ammonia from an air-ammonia mixture

by water, in a wetted wall tower, the value of the overall gas mass transfer coefficient

Kg was found to be 0.9325 kmol m-2 h-1 atm-1 from an air-ammonia mixture in a wetted

wall tower. The operating pressure and temperature are 2 atm and 288 K respectively.

For dilute solutions of ammonia at 288 K, the equilibrium relation is given by, pA =

4cA , where pA is the partial pressure of ammonia in atm and c A is the concentration

of ammonia in water in kmol m-3 of solution. At the top of the tower, the outlet gas

contained 1% ammonia by volume and the input in contact is pure water. 85% of the

total resistance to mass transfer was contributed by the gas phase. Calculate:

a) the overall coefficient based on liquid concentration

b) interphase composition

c) the mass transfer flux.

Problem