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The Aalborg Energie Technik a/s (AET) boiler concept is based on 25 years of experience with steam generation and biomass combustion.
This experience has been gathered from a large number of plants with the following characteristics:
- Very high availability
- Steam data and steam quality suitable for turbine operation
- High boiler efficiency
- Fulfilment of strict emission requirements
- Flexibility
- Continuous operation at full load
- Low maintenance costs
- Long operating time (>8000 hours) between shutdown for manual cleaning of heating surfaces - also applies for demolition wood.
These characteristics are based on the following:
- Gas tight and fully welded water tube boiler
- Very limited refractory in furnace
- Tall furnace with long residence time
- Empty radiation pass for cooling the flue gas before superheater
- Vertical flue gas pass for collection of ash
- Unheated downcomers
- Good natural circulation even under extreme operating conditions
- Effective steam separation in the drum
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The boiler pressure parts are designed in accordance with accepted European norms and standards. This applies for the choice of materials, calculations of wall thicknesses, production, certification of welders as well as quality assurance of the finished product.
The furnace is tall and slim in order to obtain a long residence time and good turbulence resulting in good mixing of unburnt gases and combustion air. This ensures good combustion with low emissions.
A tall furnace also ensures good circulation of water and steam in the panel walls.
Minimal refractory is used in the furnace to prevent ash deposits and slag formation.
From the furnace, the flue gas flows into the upper part of the radiation pass and continues towards the super heater passes passing a bottom hopper, allowing coarse ash particles to be separated from the flue gas. The collected particles are reinjected into the furnace.
From the furnace, the flue gas flows into the upper part of the radiation pass and continues towards the superheaters passes passing by a bottom hopper, allowing coarse ash particles to be separated from the flue gas. The collected particles are reinjected into the furnace.
The superheaters are arranged to allow flue gas and ash particles enough time to be cooled below the ash melting point before inlet to the superheaters and to allow ash particles to fall freely down through the heating surface.
The economiser is placed as a separate unit and is provided with heating surfaces consisting of plain tubes.
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