1.7. Technical questions:
		1. How is Le-chartlier principle used in the process? i) Only reactants and not product (Ammonia) are fed to the reactor. According to Le-chartlier principle, higher yields are obtained at high pressures. Exothermic reaction implies that the temperature cannot be too high. ii) Ammonia removal from vapor phase emanating from the condenser is according to Le-chartlier principle, which indicates that the presence of ammonia in the feed can reduce conversions and hence yield. 2. Why is purge stream taken out after centrifugal pump. If purge stream is taken before centrifugal pump, then pumping cost would reduce ? i) The purge stream consisting of Argon impurity would go to pressure swing adsorption process for Argon recovery. Therefore, it will be advantageous to have as much high pressure as possible for the purge stream and hence it is desired to take the purge stream after the centrifugal pump. 3. How can ammonia whose boiling point is -33°C can get liquefied at a temperature of -15°C using ammonia refrigerant ? i) Ammonia’s boiling point is -33°C at 1 atm pressure. At higher pressures, the boiling point of ammonia will increase. Therefore, at the system pressure (which is close to 200 atm.), the boiling point of ammonia would be much higher and hence liquefaction is possible at -15°C. ii) The ammonia refrigerant is at 1 atm pressure and hence can be a liquid upto a temperature of -33°C. The stream undergoing refrigeration is at 200 atm. And therefore liquefies at about -15°C.

 

References:

Dryden C. E., Outlines of Chemical Technology, East-West Press, 2008