This is a safety device.
First,it can separate the oil and water,cause all we know oil is lighter than water.
Second.it can avoid the tail gas come back to the reactor.If the gas come back to the reactor,it will be very dangerous,it’s the reason of explosion.
When the tail gas come back to the reactor,when you discharge the carbon,the oxygen also will come into,if the temperature is also very high,OK,the accident happened.
But if there is a separator,the tail gas will never come back to the reactor,if you want to know the secret,welcome to China.