Co-Combustion Characteristics And Ash Melting Behavior Of Sludge/High-Alkali Coal Blends

Liquid slagging is an important solution for the problem of high-alkali coal slagging. The blending of low-melting-point fuel for combustion can effectively reduce the ash melting point of mixed fuel, improving the efficiency of liquid slagging. In this study, highly active sludge is mixed with Zhundong (ZD) coal. Then, co-combustion characteristics and ash melting behavior are studied by combining thermogravimetric analysis, thermodynamic analysis, ash melting analysis and ash composition analysis. The following results are observed. Ignition temperature is significantly reduced with an increase in sludge blending ratio, and combustion performance deteriorates rapidly when sludge proportion exceeds 20 wt.%. The burn out temperature initially decreases and then increases, reaching its minimum value when the sludge blending ratio is 10 wt.%. The blending of sludge causes the apparent activation of the sample to decrease, enhancing the combustion activity of the mixed fuel. The mixed fuel has lower ash melting point. A eutectic system with low melting point is produced due to the reaction of a large amount of sludge Fe2O3 with SiO2 in coal. The ash melting point is only 1080 degrees C when 10 wt.% sludge is mixed. On the basis of the two considerations for improving combustion performance and reducing the melting point of ash, the recommended optimal blending ratio of sludge is 10 wt.%.