Combustion Air Humidification

Flue Gas Condensation combined with combustion air humidification

Heat recovery is maximized by condensing the flue gas and humidifying the combustion air. The higher the humidity in the combustion air, the more heat will be absorbed.

How it works in theory: 

Thanks to the water distributed into the humidifier, the moisture level of the combustion air feeding the boiler is higher, and therefore the flue gas saturation point is consequently increased. 

So, the humidity contained in the flue gas allows to recover more heat to be transferred to district heating. 

A condenser in 2 stages : 

• A 1st stage carrying out the heat transfer to the district heating loop with a parallel plate heat exchanger
• A 2nd stage cooling down further the flue gas, with process water coming from humidifier

How it works in practical:

The condensate water is partly used to humidify the combustion air. The condensate from the cooling step of condenser is directed after pumping from the condenser collecting tank to the top of the humidifier.

The condensate is distributed through the distributor across the complete tower cross section above a packing bed. All flows from the condenser are distributed on the whole surface of the packing by the main distributor.

The condensate is collected in the collecting tank at the bottom part of the humidifier. The condensate is pumped by a recirculation pump and sent back to the top of the condenser.

The humidified combustion air is reheated by a steam / air heat exchanger downstream of the humidifier before being connected to the boiler’s combustion air system.