Patent ID: 7763162

Claim:
A method for treating gaseous effluent from a hydrocarbon pyrolysis process unit, the method comprising: (a) passing said gaseous effluent derived from pyrolysis of a feed heavier than naphtha through at least one primary heat exchanger, thereby cooling said gaseous effluent to a temperature above its dew point and generating from saturated steam having a temperature of less than about 288° C. (550° F.), superheated steam having a temperature of at least about 399° C. (750° F.) and a pressure of no greater than about 6310 kPa (900 psig); (b) passing said gaseous effluent from step (a) through at least one secondary heat exchanger having a heat exchange surface maintained at a temperature such that part of said gaseous effluent condenses to form a liquid coating on the surface, thereby further cooling the gaseous effluent to a temperature at which at least a portion of the tar, formed by the pyrolysis process, in the gaseous effluent condenses; and (c) removing said condensed tar from said gaseous effluent; said method being carried out in the absence of direct quenching.