Flue gas condensing
Flue gases issued from combustion of different fuel (basically waste or biomass) may contain significant amount of steam (normally in the range 10 - 25%). The condensation of steam releases latent energy which may be transferred in a condenser to an heating circuit or to the combustion air, in this way the efficiency of the heating system can increase up to 20%.
Flue gas condensing is done either in a condensing scrubber or in a tube condenser (or alternatively in a variation of these two). Different chemicals additives may be used in the scrubbers to further reduce the emissions:
Generally in a condensing scrubber flue gas feed is a bottom section of the equipment. There it is pushed through a washing stage and then through a heat recovery stage. Most of the emission are transferred to circulation stream via absorption. A packing bed generally enhace contact area of the flue gas and circulating stream, making heat recovery and absorption more efficient. Generally we used a typical two stage scrubber with the packing bed used for heat recovery purposes.
When the heat recovery is main purpose of the system generally the preferred equipment is a tube condenser. In this case generally the feed is at the top and the flue gas runs through sprayed circulating water and through condensing tubes that are typically cooled with return water from district heating network.