Carbonization temperature and charcoal properties at different positions in rectangular kiln

Abstract

To increase production and decrease the heterogeneity of charcoal produced in rectangular kilns, the control of carbonization must be carried out based on the kiln internal temperature. The objective of this work was to analyze the maximum carbonization temperature and the time of thermal degradation at temperatures above 290 °C based on the internal kiln wall temperatures, in addition to evaluating charcoal properties in different positions of a rectangular kiln. Wood from the hybrid Eucalyptus urophylla x E. grandis at seven years of age was used for carbonization in rectangular kiln where temperature was monitored and controlled. Process parameters and charcoal quality were evaluated in seven positions in the rectangular kiln. Positions 1 and 7 had higher maximum temperature values and thermal degradation time at temperatures above 290 °C in comparison with the other positions, which presented similar values. There was no significant effect of kiln position on the characteristics of charcoal, which presented average values of 234.61 kg m-3 of bulk density; 55.87% of pieces with size greater than 30 mm; 19.77% of fines (granulometry < 9.5 mm); and 20.80% of friability, 75.39% of fixed carbon, 24.37% of volatile materials, and 0.24% of ash. It was concluded that the kiln position affects the temperature and time of thermal degradation; however, the control of temperature guarantees the production of homogeneous charcoal throughout the kiln, presenting satisfactory quality for steel industry usage.