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Show The Frbling unit (Figure 10a) is generally mounted directly to the existing boiler stack and contains an internal heat exchanger in the hot water bath at the bottom of the tower. The Aerophysics unit (Figure 10b), which is licensed by the French company, L'Industrial de Chauffage, is also normally mounted directly to the boiler stack. The hot water is collected in a separate filter tank that removes dust, etc., collected in the tower and then pumped through the secondary heat exchanger and recycled to the top of the tower. As expected from the variations in the design approach, each unit has its own characteristics of heat transfer efficiency, hot water temperature level, pressure drop, floor space requirements, etc., and they must all be considered in a potential installation. OTHER TYPES OF EQUIPMENT The retrofit of DCCHR equipment is most attractive when the low level load requirement constitutes at least 15 percent of the total boiler load and can be satisfied by a temperature level of 130°F. There are two additional equipment systems that should be considered for heat recovery if either the low level load constitutes a greater percentage of the total load or the required temperature level is greater than 130°F. These are: . Direct Contact Combustion (also referred to as submerged combustion) - This equipment provides for direct contact between the hot combustion gases (1500-2000°F) with a cold water stream resulting in a hot water stream (140-180°F) and a cold flue gas (100-110°F). This type of equipment is most suitable for installations where 100 percent of the heat requirement can be satisfied with 180°F water. The combustion efficiency of these systems is 95 percent to 97 percent based on the higher heating value due to the low flue gas exit temperature. These systems have costs per MBtu/hr similar to the DCCHR units. • Indirect Contact Condensation Heat Recovery - These are standard tubular exchanger units that allow for cold flue gas exit temperatures and condensation by either using glass or teflon tubes, which are corrosion resistant, or by using replaceable modules on the cold end which are allowed to corrode and then replaced. These systems allow for higher outlet water temperatures (190°F) and also are suitable for 9-31 KVB1O-P-281 |