Question 1: A solvent is to be recovered from a solvent air mixture by scrubbing with water in the packed tower at a pressure of 101.3 kN/m2 and at temperature of 300K. The solvent vapour enters the tower at a rate of 0.1kg/s and consists of a concentration of 2% by volume. It is essential to recover 99.9% of the solvent; for the packing chosen the optimum gas and water flow rates are known to be 1.3 and 2.0 kg/m2s correspondingly. Compute the height and diameter of the tower. The data needed is as shown below:
Overall mass transfer coefficient Kya = 0.0389 kg/s m2(kN/m2)
Equilibrium data: Pe = 0.02 x; where Pe equilibrium pressure of the solvent kN/m2 and x the mole fraction of the solvent in water.
Molecular weight of the solvent and air are 70 and 29 kg/kmol, correspondingly. Find out other data in the book and make suppositions which make sense as it applies to respective problem.
Question 2: A sphere of naphthalene ball containing a radius of 10 mm is suspended in a big volume of still air at 318 K and 1 atm absolute pressure. The vapor pressure of naphthalene is 0.56 mm Hg at 318 K and the DAB of naphthalene in air at 318 K is 6.92×10-6 m2/s. Compute the rate of evaporation of naphthalene from the surface in k.moles/m2.s. Estimate the time needed for the diameter to reduce to 2 mm.
Question 3:
a) Under what conditions are the mass average velocity and molar average velocity of the components of a mixture equivalent?
b) Ammonia is defusing via an inert air film thick at a temperature of 200C and a pressure of 1 atm. The concentration of NH3 is 10 percent by volume on one side of the film and zero on the other side. Estimate the result on the rate of diffusion of raising the total pressure to 10 atm.
Question 4: Larson by using an Arnold cell measured the diffusivity of chloroform in air at 250C and 760 mmHg. The liquid density of chloroform at 250C is 1485 kg/m3 and its vapor pressure at 250C is 200mmHg. At time t = 0, the liquid chloroform surface was 74 cm from top of tube and after 10 hrs the liquid surface had dropped by 0.44cm. If the concentration of chloroform is zero at the top of the tube, what would be the gas diffusion coefficient of chloroform in air?
Question 5: Ammonia gas stream from a reactor comprises of 25% by volume of ammonia and 75% by volume of air. Pure water is utilized to absorb ammonia in an absorption packed tower at 300C and 1 atm. The total gas flow rate is 1000 k moles/hr. This is desired to decrease the concentration of ammonia to 2 % by volume in the outlet. Find out the minimum liquid rate? If 2.0 times the minimum liquid is employed, then what will be the number of transfer unit needed? Equilibrium relation is given as y*= 2.0 x, where y is mole fraction of ammonia in gas and x is mole fraction of ammonia in liquid. Compute the diameter of the tower.
Find out other data in the book and make suppositions that make sense as it applies to particular problem.