Prediction of Lignite Ash Melting Behavior from Northwest Greece Based on Its Mineralogical Composition

The aim of this study is to predict the ash fusion temperatures of the lignite ash produced in Western Macedonia, Greece, by their composition. The lignite mined in northwest Greece feeds the power plants of Agios Dimitrios, Kardia, Ptolemais, Amyntaio, and Meliti. An extensive number of samples, which were collected by the feeders of power plants during a 10-year period, were investigated. All lignite ashes were mineralogical and chemically quantitatively analyzed by XRD and XRF, respectively. Using a heating microscope, the ash fusion temperatures of the ashes were identified. According to their chemical composition, ashes can be characterized as calcareous. Indices based on the chemical composition showed that, qualitatively, the tendencies of slagging and/or fouling were found to vary mainly between medium to high. For a quantitative estimation, correlations were identified between the quantitative mineralogical composition and the ash fusion temperatures using regression analysis. The whole study focused on creating a model for the prediction of lignite behavior during combustion in power plants. The finest models achieved a mean adjusted regression coefficient of around 0.87, while the accuracy, according to root mean square errors, was less than 40 °C.