Condensing Economiser

Flue gas heat recovery (Natural gas)

Opportunity 
Stack temp- 240 deg c
Efficiency – 88 %
Losses  – Dry flue gas loss- 8.8 %  ( 8%)
Moisture loss – 2.2 %  (10.7%)
Unburnt loss – 0.5 %  (0.5%)
Radiation loss – 0.5 % (0.5%)
Challenges 
Reduction in heat transfer Performance
Low end corrosion

Flue gas heat recovery (Fuel Oil)

Conventional heat recovery system 
Air preheater – 4%
Economiser/Water preheater – 4%
Limitations of conventional system 
It targets only sensible heat loss.
Low end corrosion limits heat recovery  opportunity
Heat recovery opportunity (Extra) 
Sensible heat loss- 6.5 %
Latent heat loss – 8 %

Condensing economiser
(Prospects for gaseous fuel)

Gaseous fuel
Higher hydrogen contents- Higher latent heat  recovery (Efficiency can approach 105%)
Less flue-gas volume-  Less heat transfer area  requirement & higher pay back
Less sulphur-  Less severity of corrosion &  higher freedom for material selection