Question

A vacuum purging technique is to be used to reduce the oxygen concentration within a cylindrical process vessel with a diameter of 1.5 m and a height of 2.5 m.

The oxygen concentration is to be reduced to 0.05 % by volume using nitrogen as the inert gas. The temperature is 20°C and the vessel is initially filled with air. A vacuum pump is used to reduce the pressure in the vessel 75 mm Hg absolute and the vacuum is then relieved with pure nitrogen until the pressure returns to 1 atmosphere.

Assume atmospheric air contains 21% by volume oxygen.

Determine: (i) The number of purge cycles required. (8)

(ii) The mass of nitrogen required in kg. (3)

(iii) The ratio of nitrogen required for vacuum purging to the nitrogen required for siphon purging. (3)

Ideal Gas Law Constant R = 8.314 kJ kmol-1 K-1

1 atm ≡ 760 mm Hg ≡ 1.013 bar

Answer 1

I have described the equations to be used logically and how they are used in obtaining the final formula.See the detailed solution and you will find more about them in any standard textbook.I am extremely sorry about not doing the third part because i was not having any knowledge about that.