In a Linde simple column system (see Fig. 3.11), air is fed at 300K. It is compressed up to 200 atm. It is cooled down with the gas products N2 and O2, which exit the column at their boiling points of 77K and 90K, respectively, with the system at 127K. Compute the number of trays assuming that the nitrogen purity is 95% of the one corresponding to the thermodynamic equilibrium, and that the oxygen contains 5% nitrogen.

Assume that the Hauser diagram (Fig. 3.1) holds for all enthalpy computations.