Combustion Air Humidification

Heat recovery is maximized by condensing moisture from the flue gas and by humidifying the combustion air. Increasing the humidity level in the combustion air enhances the latent heat potential, allowing more energy to be absorbed during the combustion process.

How it works in theory:

By distributing water into the humidifier, the moisture content of the combustion air supplied to the boiler is increased. This elevated humidity raises the saturation point of the flue gas, enabling deeper condensation and thereby maximizing heat recovery. The latent heat contained in the flue gas is more effectively recovered and transferred to the district heating network.

The condensation system operates in two stages:

• Primary Stage – A parallel plate heat exchanger directly transfers the recovered heat from the flue gas to the district heating loop.
• Secondary Stage – The flue gas is further cooled using process water sourced from the humidifier, allowing additional condensation and heat recovery beyond the primary stage.

This configuration enhances overall thermal efficiency and supports integration with low-temperature district heating systems.

How it works in practical:

A portion of the condensate recovered from the cooling stage of the condenser is reused to humidify the combustion air. After being pumped from the condenser’s collection tank, the condensate is directed to the top of the humidifier. It is then evenly distributed across the full cross-section of the tower via a dedicated distributor located above the packing bed.

All condensate flows from the condenser are uniformly spread over the packing surface to ensure optimal contact and evaporation. The humidifier collects the remaining condensate in a bottom tank, from which it is recirculated by a pump back to the top of the condenser, maintaining a closed-loop system.

Downstream of the humidifier, the now humidified combustion air is reheated using a steam-to-air heat exchanger before being fed into the boiler’s combustion air system. This process increases the moisture content of the combustion air, enhancing the flue gas condensation potential and overall heat recovery efficiency.