Patent ID: 7718049

Claim:
A method for treating gaseous effluent from a hydrocarbon pyrolysis process unit, the method comprising: (a) cooling said gaseous effluent consisting essentially of gas from steam cracking, in at least one primary heat exchanger, and further, in at least one secondary heat exchanger or by direct quench with a liquid selected from liquid quench oil, pyrolysis fuel oil, and water, at least to a temperature at which tar formed by the pyrolysis process condenses from the effluent to provide a partially condensed effluent; (b) passing said partially condensed effluent to a separation vessel; (c) removing condensed tar from the separation vessel; (d) cooling said condensed tar; and (e) recycling at least a portion of said cooled tar to said separation vessel at or below the level at which said partially condensed effluent enters said separation vessel; wherein said cooled tar is introduced to said separation vessel at a temperature below the temperature of the effluent entering said separation vessel.