A mixed hydrocarbon stream must be distilled in a continuous distillation column. The flow rate of the feed is 1000 kmol/h. The feed enters as a liquid at its boiling point. The feed mixture containing six components (CH4 = 0.032, C2H4 = 0.068, C2H6 = 0.17, C3H6= 0.30, C3H8 = 0. 32, n-C4H10 = 0.11) is to be separated by distillation. It is desired to recover 98.5% mole fraction of the light key in the distillate and 98% of the heavy keyin the bottom product. The average relative volatility (a) values are given in Table 1.The a can be assumed to remain constant with any temperature variation.

1.Determine the light key (LK) and heavy key (HK). 2.Use Underwood's method to determine the minimum reflux ratio (the 0 valuesto try are 1.1.1.17 and 1.2).(15) Use the Fenske equation to determine the minimum number of trays.