Combustion characteristics and ash melting behavior of Zhundong coal/municipal sludge blended combustion

Liquid slag discharge is an important means to solve the problem of slagging and fouling in the combustion process of Zhundong coal. Blending low melting point fuel can effectively reduce the ash melting point of the mixed fuel, thereby improving the efficiency of liquid slag discharge. In this paper, high activated sludge and Zhundong coal were blended. The combustion characteristics and ash fusion behavior of the blends were studied by thermogravimetric analysis, ash melting point analysis, Fourier transform infrared spectroscopy and ash composition analysis. The results showed that the ignition temperature decreased significantly with the increase of sludge blending ratio, and the ignition performance and burnout performance of the mixture deteriorated rapidly when the sludge mass ratio exceeded 20%. The burnout temperature decreased first and then increased with the increase of sludge mixing ratio, and reached the lowest when the sludge mixing mass ratio was 10%. The results of infrared spectroscopy showed that the incorporation of sludge promoted the pyrolysis and combustion of active hydroxyl groups, aliphatic functional groups, oxygen-containing functional groups and aromatic functional groups in pulverized coal. The Fe2O3 in the sludge reacted with SiO2 in the coal to form a low melting point eutectic, which made the mixed fuel be of a relatively low ash melting temperature. When the sludge blending ratio was 10%, the ash melting temperature of the mixture was 1080°C. Considering the stability of fuel combustion and the reduction of ash melting point, it was recommended that the optimal blending ratio of sludge and Zhundong coal is 1∶9. © 2023 Chemical Industry Press. All rights reserved.