Flue gas will form and condense on a heat exchanger and in the boiler stack when it falls below its dew point, and this occurs when the return water temps of the system are around 135°F. The vapor of the flue gas undergoes a phase change into a liquid which is now acidic with a pH typically between 25.
thanks to this flue gas condenser, or heat exchanger, more than 50% of the energy of this stack gases can be recovered depending on the working conditions. The condensed water is collected in the bottom of the heat exchanger with all the particles that it has collected because of the contact with the gas.
Flue Gas Condensers CleanBoiler
Recovery of Water from Boiler Flue Gas Using Condensing Mar 31, 2011 · The results showed flue gas water vapor condensed in the low temperature region of the heat exchanger system, with water capture efficiencies depending stronglymore » Sulfuric acid vapor condensed in both the high temperature and low temperature regions of the heat transfer apparatus, while hydrochloric and nitric acid vapors condensed with the water vapor in the low temperature region.
The integrated flue gas heat exchanger is installed in the exhaust chamber ex works as part of the boiler, is connected on the water side and is ready for immediate use. Also available as a stand-alone version which can be easily retrofitted. Bosch also provides the stainless steel condensing heat exchanger as a separate, ready-to-connect module.
Low Cost Polymer Heat Exchangers for Condensing BoilersFor metallic condensing economizer heat exchangers 316L alloy is commonly used. The bulk price of this alloy is estimated at $130/lb. Some condensing boilers designed for oil-firing use 904L alloy and here the price can be significantly higher, ~ $3.00 per pound. Prices of course depend on quantity purchased, shape, and finish options.
The residual heat contained in the flue gas downstream of the condenser is used to heat and evaporate water. This moisture is transferred to ambient air and directed to the boiler as hu-midified, pre-heated combustion air. This increases the mois-ture in the flue gas and the heat recovery in the upstream condenser.
Flue gas and condensing heat exchangers from BoschThe flue gas flows at the boiler outlet inherently have heat potential at a high temperature level. A flue gas heat exchanger is great to use in order to prevent unnecessary flue gas losses. This efficiency component extracts heat from the hot flue gas and, in return, preheats return water. Maximum efficiency gain when using condensing technology
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