HOT|COOL NO. 3/2018 - "Digitization"


ADVANCED PLANT The plant consists of a gasifier, a gas burner, a thermo-oil boiler, a flue gas condenser and an ORC-turbine plant. When the flue gas is passed through the heat exchangers of the thermal oil plant, the temperature is about 950 degrees celsius. After yielding its energy to the thermal oil plant, the temperature is about 185 degrees Celsius. From the thermal oil plant, the heat can be directed to district heat exchangers or to the ORC plants turbine that produces electricity and heat. In the quench, the flue gas is cooled to 60 degrees Celsius, and in the flue gas condenser, the flue gas is cooled further, and the final energy is extracted. When the flue gas is led to the chimney, the temperature is as low as 40 degrees Celsius.

LOW GRADE FUEL AND LOW PRICES The district heating company had some high demands for the plants, including low content of dust, CO and Nox from the flue gas during the gasification process; fuel flexibility; lower prices; as well as being a plant that looks nice and fits well with the surroundings. With the new plant by Dall Energy, they got all that. The plant has a very wide operation range. It will operate fully efficient from full load all the way down to 15% load, i.e. the plant can handle both daily and seasonal demand fluctuations. One of the benefits of the gasification solution is that it is possible to use low grade fuel. The gasification technology can handle fuel with up to 60% moisture content, as well as dry fuel. The plant can use a combination of local and cheap fuels in the form of e.g. garden waste and other residues that cannot normally be used elsewhere. Instead of a relatively fast combustion of solid material, the reaction to gas occurs in a slow gasification process, after which the gasification gas is burned. Due to the low speed of gas and a good mix of gas and air the level of dust, CO and Nox are very low after the gas combustion. Therefore, no flue gas filters are needed, which are often required for other types of biomass plants. The plant does not have cyclones or electric filters. The flue gas condensation unit increases the thermal efficiency by 25% and it also removes the particles of the flue gas without extra cleaning. The very low emissions means that the plant can settle with a short chimney, which can therefore be integrated into the building in a way that appear less dominant.

Marc Centner, Anders Emus and Jesper Skrubbeltrang on the top of the thermal oil heater

The fuel will be wood chips from Danish forests combined with local garden waste. The plant thus becomes truly CO2 neutral - while resolving a "waste problem" in the form of garden waste (where a significant part is combusted with household waste in waste facilities).


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