Implement an energy conservation method, which can recover a majority of the energy wasted up the boiler exhaust stack. A Direct Contact Heat Recovery System can be used to transfer the exhaust gas heat directly to process hot water. A typical gas fired boiler in an industrial process operates at an efficiency of 70 to 80%, with exhaust stack temperature in excess of 350 Deg. F. Consequently, 20% or more of the fuel consumed is exiting the boiler stack. The Ludell Stack Gas Heat Absorber (Economizer) is a direct contact heat recovery technology, which involves passing the hot flue gas through a stream of water. The resulting flue gas exiting temperature is within 10 Deg. F. of the incoming water; that is, if the inlet water temperature is 60 Deg. F. the stack temperature will be 70 Deg. F. Since the flue gas is cooled below its dew point, both the latent heat of the water vapor in the flue gas and the sensible heat is recovered. The Ludell Stack Gas Heat Absorber eliminates the problems inherent in older style stack economizers. The system is supplied in stainless steel construction, designed for low-pressure drop and maximum heat recovery