Oxy-fuel and air atmosphere combustions of Chinese medicine residues: Performances, mechanisms, flue gas emission, and ash properties

Abstract

This study aims to quantify the combustion performances, mechanisms, and ash characteristics of Chinese medicine residues (CMR) in the air and oxy-fuel atmospheres. The CMR combustion underwent water loss (<150 °C) and the decomposition of the main organic components (150–560 °C). The CMR combustion performed better in the air than 8-2/CO2-O2 atmosphere experimentally, as was also evidenced by the joint optimization based on artificial neural network. The rising oxygen fraction of the three oxy-fuel atmospheres improved the oxy-fuel combustion performance by 76.7%. The air atmosphere led to a higher activation energy at the start (275.15 kJ/mol) and end (520.91 kJ/mol) of the main reaction, while the oxy-fuel atmosphere resulted in a higher activation energy of 400.22 kJ/mol with the conversion degree of 0.7. Its reaction mechanism followed the sequence type (Fn) and changed from F3 to F2 in the 8-2/CO2-O2 atmosphere and from F2.4 to F2.5 in the air atmosphere and flue gas functional groups included CO2, H2O, C=O, and C-(O)H. The oxy-fuel atmosphere was more prone to slagging than the air atmosphere. The ash in the oxy-fuel atmosphere was easily formed calcium carbonate and calcium hydroxyphosphate.