Abstract: Method and apparatus are disclosed for cooling a process gas stream having a temperature in the range from about 400.degree. F. and 3000.degree. F. and absorbing gaseous contaminants therefrom wherein contact is effected between said process gas stream and respective quench and absorbent liquids in order to provide said cooling and absorbing functions. The flow rates of the process gas stream, quench liquid, and/or absorbent liquid are subject to substantial variations due to operating conditions related to the process gas source or to the provision for contaminant recovery, requiring absorbent liquid of a desired concentration. In practice, the process gas stream may be that discharged from a waste product incinerator containing not only products of combustion but also the aforesaid gaseous contaminants.