An ammonia production plant operates an absorption column with 15 trays. It processes a gas stream of 15 kmol/s with 25% ammonia in countercurrent flow with water. The flow of water is 20 kmol/s. The column operates at 10 atm and 25C to recover 98% of the ammonia.

Calculate the tray efficiency and the excess of liquid flow with respect to the minimum. Assume that Raoult’s Law holds.