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Show This paper presents an overview of the "state of the art" of direct contact condensation heat recovery (DCCHR) heat exchangers. The primary application for these units is the recovery of waste heat from the flue gas produced by industrial combustion equipment. The energy conservation potential can be very large for industrial boiler applications where the waste heat is recovered by condensing the water vapor in the flue gas and then used for feedwater preheat or with an auxiliary load. This study was conducted by KVB, Inc. for the Industrial Utilization Research Sub-Division of the Gas Research Institute (GRI)*. Direct Contact Condensation Heat Recovery is the process of passing a hot flue gas through a cold water stream resulting in a cold flue gas exit temperature (~100°F) and producing a hot water stream at approximately 130°F (±10°F). As the exit flue gas is below its dew point temperature, both the latent heat associated with the water vapor in the flue gas and sensible heat from the dry gas are recovered. The efficiency improvement from a DCCHR unit can range from 8 percent (for oil-fired boilers) to 15 percent (for natural gas fired boilers) and therefore represents the highest potential efficiency gain of all retrofit heat recovery devices. The primary limitation to the application of this equipment is the utilization of the low level heat (130°F) produced. It is estimated that over 15 percent of all the energy consumed in the U.S., or more than 8,800 trillion Btu's per year, is required by industrial boilers to generate process steam. Unfortunately, 9 to 13 percent of the fuel heating value remains in the exit flue gas and is dumped into the atmosphere. Therefore, a system that recovers this waste heat for boiler feedwater heating, air preheat, or process use can result in major fuel savings. Flue gas condensation heat recovery systems are commonly available in Europe but only recently have been marketed in the U.S. More than 500 units are in operation in Europe. *GRI Contract 5080-342-0421, February 1981 9-3 KVB10-P-281 |