Investigation on the sintering behaviors of low-temperature lignite ashes

To investigate the sintering behaviors of lignite ashes, the 450 °C Xiaolongtan (XLT) and Huolinhe (HLH) lignite ash samples were analyzed by press-drop sintering technique, scanning electron microscope, and X-ray diffraction. The result shows the sintering temperature of XLT ash is lower than that of HLH, as a result of that base/acid (B/A) ratio of XLT is higher than that of HLH. The sintering temperatures of two lignite ashes under reducing atmospheres (H₂ and CO) are lower than those under oxidizing atmospheres (CO₂ and O₂), which result from the effects of different iron states under different atmospheres. The sintering temperatures of two lignite ashes decrease with the increase in pressure. It decreases slightly in the range of low pressure, changes clearly in the range of 0.7–1.0 MPa, and changes slightly again with further increase in pressure. The sintering process of lignite ashes is proposed by the presentation of partial-melting phases, the generations of aggregates, and the densification of aggregates.