Effect of carboxymethyl cellulose on the drying dynamics and thermal cracking performance of iron ore green pellets

• Drying characteristic curves of pellets were obtained by a self-equipped device.
• Apparent activation energy of second drying stage was calculated.
• Ea increases with dosage, polymerization degree and substitution degree of CMC.
• Ea represents thermal cracking performance of green pellets added with CMC.
• Thermal cracking is attributed to vapor pressure rather than the decomposition of CMC.

Carboxymethyl cellulose (CMC) is an efficient organic binder in iron ore pelletization. However, the addition of CMC will reduce the anti-thermal cracking performance of the green pellets prepared. The objective of this article is to investigate the effect of CMC property on the drying dynamics and thermal cracking performance of green pellets. The results show that as the degree of polymerization (DP) and degree of substitution (DS) of CMC increase, drying rate declines and apparent activation energy of second drying stage goes up. When more CMC or CMC with larger DP and DS is added, the green pellets possess better mechanical strength but worse anti-thermal cracking performance. Although CMC decomposes during drying at 300–350 °C, which may destroy the reticulate structure of organic chains, thermal cracking is attributed to high resistance of water/vapor diffusion caused by compact structure of the pellets rather than CMC decomposition.

Ea of second drying stage represents the thermal cracking performance of green pellets added with CMC, and it is affected by CMC type and CMC dosage.Figure optionsDownload as PowerPoint slide