Treatment and residues
The plant is environmentally-friendly and safe
Flue gases are cleaned in several stages in the plant, and the emissions are continuously analysed and measured as is obligated by the environmental permit. The residues formed in the plant are also further treated accordingly.
A controlled incineration process ensures that the waste is combusted in a clean wayThe temperature on the grate is over 1 000 °C, a temperature at which also lower-quality fuel is incinerated efficiently. The plant is supervised 24 hours a day, and the process is adjusted in order to keep it clean and safe. The technology used in the plant represents BAT (Best Available Technology). Modern WtE plants all over Europe use similar equipment which means that the technology used in the plant has already been thoroughly tested in practice.
The flue gases are carefully cleaned in a multi-phase processAfter the combustion, the temperature of the flue gases is held at a minimum of 850 degrees to prevent the formation of toxic gases. Nitrogen oxides (NOx) are neutralised by adding ammonia. Ammonia infusion is controlled by a sophisticated computer-operated system. Based on temperature and computer models, the chemical is added only when and where necessary, minimising the amount of ammonia used as well as the ammonia residue in the flue gases. The remaining hazardous compounds are absorbed into fabric filters using lime and activated carbon. The advantage of this system is that no effluents requiring further treatment are formed in the plant. The composition of the flue gases is constantly monitored and controlled in order to ensure that no hazardous substances will get into the air. Information obtained from continuous monitoring of the flue gases is used to adjust the operations of the boiler.
Did you know that the emissions of a Waste-to-Energy plant are only a fraction of the emissions of a traditional power plant utilising coal or fuel oil?
The ashes from the process are treated so that they are not harmful to the environment
There are different kinds of ashes formed in the plant.
Bottom ash is discharged from the grate just like ash from a fireplace at home. The composition of the bottom ash is thoroughly analysed, and potential alternatives for utilisation are evaluated. Until the way of utilisation has been confirmed, the bottom ash will be placed at a landfill.
Boiler ash is formed as the hot flue gases are led up through the boiler. There are ash flakes in the hot flue gases and as the flue gases cool down, the ash gets stuck to the heat-exchange surfaces of the boiler. The surfaces are cleaned regularly and, just as the bottom ash, the contents of the ash will be analysed for utilisation purposes. Before utilisation, the ash will be stabilised and placed at a landfill suitable for hazardous waste.
Flue gas treatment residue is the residue of the flue gas treatment process. Lime and activated carbon are added into the flue gases. The hazardous compounds of the flue gases, such as heavy metals, adhere to the lime and activated carbon particles. These particles in turn are absorbed by fabric filters, somewhat similarly to a vacuum cleaner bags. The flue gas treatment residue is temporarily stored in its own silo. It is stabilised using cement and safely disposed at a landfill especially built for this purpose.