Straw-fired CHP plant
Avedøreværket generates electricity for the Sealand electricity grid and heat for one of the largest metropolitan district heating systems in Northern Europe. The plant was commissioned in 1990.

The world’s largest straw-fired supercritical boiler
The new Combined Heat and Power (CHP) block, Avedøre 2, represents a completely new technology and is the world’s largest plant of its kind. It is also the world’s most advanced straw-fired CHP plant.
In 1998 we were awarded the contract for the construction of the steam turbine and in 1999 we signed a contract for the ultra supercritical straw-fired boiler plant, featuring a new advanced straw-feeding system.
Straw-fired CHP plant Avedøre, Denmark
The Avedøre 2 plant, which can fire gas, oil, and biomass, began operation at the end of 2001.
The biomass plant contributes up to 35 MW electricity and 50 MJ/s heat. The plant accounts for about 10% of the annual fuel consumption, or approximately 150,000 tonnes of straw per year.
The boiler is designed for 100 percent straw firing, and is the world’s largest and most effective straw-fired boiler with ultra supercritical steam parameters. The boiler generates steam for the main steam turbine of the CHP block.
The technology
The advanced combustion system consists of two straw feeder systems which include:
- Conveyor system from straw storage to boiler house
- Fire damper for prevention of backfire
- Control system for straw supply
- Newly developed straw shredder which reduces the straw density from 100 kg/m3 to 30 kg/m3
- Double screw feeders built into the water-cooling feeding ducts mounted on the boiler front
- Water-cooled vibrating grate
The straw is fed into the furnace by screw feeders onto a water-cooled vibrating grate where up to 80 percent of the energy content is released by pyrolysis and gasification. The remaining straw/carbon will burn out on the water-cooled vibrating grate.
A bag filter system removes more than 99 percent of the particulates from the flue gas leaving the boiler. Slag and ash is carried to containers by a submerged slag conveyor system.

Pre-treament system and boiler at the Avedøre straw-fired plant.
Plant design data
Process parameters |
Values |
Units |
Steam flow |
144 |
t/h |
Steam pressure |
310 |
bar |
Steam temperature |
583 |
°C |
Energy input |
105 |
MW |
Fuel input |
26.5 |
t/h |
Feedwater temperature |
230 |
°C |
Flue gas temperature after air heater |
115 |
°C |
Thermal efficiency |
93.2 |
% |
Electrical efficiency, total |
49.5 |
% |
Total plant output |
|
|
Maximum electrical output |
535 |
MW |
Maximum thermal output |
620 |
MJ/s |
|
|
|
Local flue gas limits |
|
|
CO, max. |
625 |
mg/Nm3 |
NOx (calculated as NO2) |
240 |
mg/Nm3 |
|
|
|
*Based on 6% O2 in dry flue gas