Thermal decomposition fundamentals in large-diameter wooden logs during slow pyrolysis

Charcoal has several applications on both small and industrial scales. Nevertheless, its parallel production of approximately 70% in coproducts during the slow pyrolysis process is still considered a challenge, especially for producers in emerging countries. However, the Brazilian production model stands out positively compared to the other producing countries, considering that Brazil is the world’s largest charcoal and sole pig iron producer from a renewable natural resource. The aim of this work was to analyze the thermal behavior of wood during the thermochemical process and the macro-thermogravimetry of large wood samples in different moisture and diameter conditions, similar to those found in the production units in Brazil. The slow pyrolysis was performed using 30-cm-long logs. The highest temperature gradient of 280 °C was observed in the 14-cm-diameter and 40 wt% moisture logs. The wood heating rate during carbonization was nonlinear. The presence of water in the wood delays the charcoal production reactions by up to 50% and contributes to the formation of different thermal profiles in the wood. Thus, due to the nonlinear thermal profile of the transformation of wood into charcoal, thermal curves are an important tool to help the control systems of the charcoal production units.