Combined heat and power (CHP) production is one way to utilize the fuel energy most optimized way. There are additional procedures and concepts how CHP plant efficiency and energy economics can be further improved. Heat recovery from flue gases by using flue gas condensing (FGC) technology, with or without combustion air humidifier or heat pump (feasibility of such depends on process parameters), is a practical solution to increase district heating (DH) capacity. Technology can be installed in existing power plant or to green field plant in order to further optimize the whole CHP plant solution. Naturally flue gas condensers decrease emissions, and different design aspects and targets can be taken into account in design.
This paper will introduce the main technological variations of flue gas condensers and also practical experiences of two selected cases. First case is a power plant (boiler size 69 MWth) in southern Finland and it has been in operation since early 2012. A tube type flue gas condenser and a combustion air humidifier were built together with the power plant. Last year optimization for flue gas condensing operating principles were done, and that has yielded promising results.
Second case is a power plant (boiler size 50 MWth) also in Finland and it has been in operation since autumn 2014. A scrubber type flue gas condenser and a combustion air humidifier were retrofitted to an existing plant. Installation was built within 9 month-project schedule and it required no extra downtime for boiler.