Online Deposition Measurement and Char-Slag Transition Model in the Reduction Zone
Char deposition experiment with various fraction of unburnt carbon in the reduction zone of pulverized coal staged combustion is performed by using an electric-heated down-firing furnace(E-DFF)and a deposition probe with online thermogravimetric measurement.Experimental results show that the deposition rate depends on the unburnt carbon content and can be divided into three zones.The unburnt carbon content in zone Ⅰ is lower than the lower critical value(UBCL),and the deposition characteristics can be calculated from the ash properties;the unburnt carbon content in zone Ⅲ is higher than the upper critical value(UBCu),and the deposition is controlled by the carbon skeleton,and the deposition rate is very small.Zone Ⅱ is between UBCL～UBCU,and the deposition properties are controlled by the carbon skeleton and ash properties.A char deposition model is proposed and applied to CFD simulation,and the prediction results are in good agreement with the experimental data.
online deposition thermogravimetric measurementchar deposition rateunburnt car-bondeposition model
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