Understanding impacts of introducing CO2 in N2 and operation conditions on physicochemical property and fusion behaviour of solid products during thermal decomposition of corn stalks

The total annual production of corn stalk (CS), a byproduct of corn processing, in China was as high as 3.1 × 108 tons, the utilization of which had great potential. The objective of this study was to investigate the characterization of the resulting solids during thermal conversion of CS under different atmospheres and to deepen the understanding of the effects of introducing CO2 in N2. The impacts of temperature, atmosphere, and particle residence time on the solid yield, ash characteristics were elucidated. It was found that the solid yields decreased with increasing temperature. For a given temperature below 600 °C, the solid yields in 20% CO2/80% N2 were higher than those in N2. But when the temperature was above 600 °C, the opposite trend was observed. Increasing residence time substantially improved carbon conversion. Compared with the solids formed below 600 °C, the 800 °C solids contained more agglomerates, which were composed of K-bearing and Ca-bearing minerals. The ash fusion temperature (AFT) increased with rising pyrolysis/gasification temperature. After substituting N2 with CO2 in the pyrolysis agent, the AFT became higher. Under the current conditions, ash deposition could occur even if the operating temperature was lower than the softening temperature (ST) due to the formation of low melting eutectics.