Drying methods and testing for residues : Boliden Kokkola
Kananoja, Roope (2021)
Kananoja, Roope
2021
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Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi:amk-2021052611387
https://urn.fi/URN:NBN:fi:amk-2021052611387
Tiivistelmä
The purpose of this thesis was to determine if it is feasible to dry sludge in outdoor conditions using floor heating, and what problems have to be overcome to make it possible. The work was commissioned by Boliden Kokkola Oy. The theory part focuses mainly on drying as a physical phenomenon and on industrial drying. The experiments for this work were done in two ways, outdoors with a floor heating provided by a thermal power station and in a laboratory using heating plates. The objective for these experiments was to see how fast the compound residue and zinc ferrite would dry in outdoor conditions compared to indoor conditions. The results are presented in more detail in the experimental part.
The tests showed that drying outdoors is very inefficient with very little drying occurring, due to the low temperature and high humidity of the surroundings during October and November, when these experiments were conducted. Drying was much more efficient in the laboratory, wherethe desired humidity of 10-14 % was achieved in 10 to 20 hours, depending on which of the used residue was being dried. What made drying possible in the laboratory was that the temperature was constantly around normal room temperature at 20°C and there was sufficient air ventilation.
Results of the tests showed that an arrangement, which ensures constant temperature of at least 20°C for the surroundings, is needed for drying to occur. The required energy could be obtained from the exit gases of various parts of the zinc production process, using an exit gas washer, or from the surplus energy of returning water from district heating.
The tests showed that drying outdoors is very inefficient with very little drying occurring, due to the low temperature and high humidity of the surroundings during October and November, when these experiments were conducted. Drying was much more efficient in the laboratory, wherethe desired humidity of 10-14 % was achieved in 10 to 20 hours, depending on which of the used residue was being dried. What made drying possible in the laboratory was that the temperature was constantly around normal room temperature at 20°C and there was sufficient air ventilation.
Results of the tests showed that an arrangement, which ensures constant temperature of at least 20°C for the surroundings, is needed for drying to occur. The required energy could be obtained from the exit gases of various parts of the zinc production process, using an exit gas washer, or from the surplus energy of returning water from district heating.