This case study is to investigate the performance of HHA column when the C2H4 concentration varies in gas feed. For the case setting up, the C2H4 concentration varies from 10 mol%, 20.54 mol% (same as the ABT378 case) and 30 mol%. The N2 concentration in the gas feed will reduce correspondingly and other components stay the same as in the base case to maintain the same mole flow rate of the gas feed. C2H4/CH4 mole ratio was used to be an indicator for discovering the separation of CH4 and C2H4 inside HHA column. Fig. 5 displays the results of C2H4/CH4 mole ratio in different phase and total hydrate formation on the plates. C2H4/CH4 mole ratios in hydrate keep about four times of its value in the vapour phase even when C2H4 concentration in gas feed is low, which indicates the separation performance of CH4 and C2H4 of HHA column remains good even at low C2H4 concentration. It is noticed that the changes of total hydrate formation per stage is not in proportion with C2H4/CH4 mole ratio because N2 hydrate formation rate is much lower than C2H4.