Energy efficiency with condenser technology

The flue-gas condenser installed at the Joensuu power plant has reduced the fuel demand. Sulphur and particle emissions also decrease as the flue gas passes through the wet scrubber.

Fortum’s combined heat and power (CHP) plant in Joensuu, in eastern Finland,  produces district heating for about 42,000 people in Joensuu and electricity for the national grid. The heat produced by the CHP plant covers 95% of the heating demand in Joensuu. Currently, more than 70% of the energy is produced with renewable wood fuel. The plant also uses peat as well as biogas generated at the nearby landfill; the biogas is piped directly from the landfill to the plant’s boiler. The energy-efficient flue-gas condenser taken into use in October 2015 further decreased the plant’s already low emissions.

Flue-gas condensing is a technology used to increase the total efficiency of solid fuel by recovering the heat contained in the process’s moist flue gases and transferring it to the water used for district heating. The condenser’s operation is based on lowering the temperature of the flue gas by spraying it with scrubbing water; the resulting steam condenses into liquid and releases thermal energy into the scrubbing water. This condensing heat can be used as district heat. So a flue-gas condenser produces a significant amount of thermal energy, reducing the production volumes of the power plant and other boilers and thus the fuel demand. This, in turn, reduces carbon dioxide emissions.

In addition to CO2 emissions, a flue-gas condenser also reduces the power plant’s  sulphur and particle emissions when the flue gas passes through a wet scrubber. It separates solid matter (particle emissions) and lowers the amount of the acidic gases, particularly sulphur emissions, in the flue gases. Sulphur oxides are significantly decreased also when they react with lye (NaOH) that is fed into the flue-gas condenser.

The new flue-gas condenser increases the Joensuu power plant’s heat capacity by about 30  megawatts (MW) and saves about 140 gigawatt-hours (GWh) of fuel annually.

The Joensuu CHP plant’s district heat production capacity is now 130 MW and electricity production capacity is 50 MW. A bio-oil production plant was integrated with the CHP plant in 2013.