Question

1. Ammonia is being absorbed from nitrogen gas using water at 1 atm and 80° F. In the incoming N2, 45 kg/hr of ammonia are flowed into the column, and the gas is 2 mass% ammonia. Henry’s constant is 1.414. 99% of the incoming ammonia is absorbed in the water.

a. Assuming L/V=2Lmin/V, how many trays are required for separation? Assuming L/V=4Lmin/V, how many trays are required for separation?

b. If a tray spacing of 24" is to be used, and the tower is to operate at 75% of flooding, what diameters are required for both L/V ratios from a). ? The surface tension of water is 72 dyne/cm. The density of the gas is 1.25 kg/m3 , and the density of water is 995 kg/m3 . Assume an active area of 90%, and foaming factor of 1.

c. If instead a column packed with 1 inch Pall Rings is used, what diameter column should be used for both flowrates? The viscosity of water is 0.8937 cp. Again assume operation at 75% flooding.

d. For the tray towers described in b). , what is bare module cost of each tower? Include only towers and trays. Use carbon steel for all construction. Use a total efficiency of 0.6 and use sieve trays. Use the data in the provided chapter, and use a cost index of 600 current day vs 400 for the data given in the text.

Answer 1