Helsinki, Finland

Recovering flue gas heat from a biomass heating plant

In Helsinki, the heating season lasts about 8 months. A new district heating plant there runs on biomass, a renewable energy that is more stable than wind or solar power. It is set to replace about a quarter of the coal used by an old power plant that is closing.

Three BROAD absorption heat pumps recover the heat contained in the boiler flue gas. Driven by steam from the biomass boiler, they cool the flue gas scrubber water from 31.2 °C to 10.7 °C and transfer this heat to the district heating water, which rises from 44 °C to 69 °C. The plant becomes more efficient without any additional electrical equipment.

• Unit type: single-effect steam absorption heat pump × 3 units
• Heating capacity: 44.9 MW in total (about 15 MW per unit)
• Heat source: 5 bar(g) steam from the biomass boiler
• Heat recovered from flue gas: 6.1 MW per unit
• Scrubber water: inlet 31.2 °C, outlet 10.7 °C
• Heating water: district heating network (inlet 44 °C, outlet 69 °C)
• Heating COP: 1.7
• Use: district heating
• Equipment: 316L stainless steel tubes (the scrubber water enters the unit directly, without an extra heat exchanger), titanium tubes on the heating side, double-section technology