Explain the dilution and displacement method for gas freeing ?

Displacement method – The inert gas enters from the top of the tank at at a low velocity , the interface of the incoming and outgoing gas must be stable without any turbulance , the hydrocarbon gas escapes through suitable piping leading out from the bottom of the tank.

Dilution method –  The inert gas is introduced at a high velocity into the tanks to penetrate to the bottom as hydrocarbon gas is heavier than inert gas or air to maintain this velocity , mainy tanks should not be diluted at the same time.