Effects of Various Carbonization Temperatures for Closing Wood-Charcoal Kiln on Charcoal Properties

Abstract

The effects of various carbonization temperatures for closing wood-charcoal kiln on the properties of the charcoal produced were studied at three carbonization temperatures of 500, 600 and 700 °C, respectively. A Thai-Iwate wood charcoal kiln (Japanese type) using eucalypt (Eucalyptus camaldulensis) wood was used to produce the charcoal. The wood was sourced from trees that were three to five years old with a diameter from 1.5 to 4 inches that had been air dried for approximately four weeks (moisture content < 40%).

The results were based on the charcoal properties of charcoal yield, moisture content, fixed carbon, volatile matter, ash content, heating value and density. The wood vinegar properties were assessed in terms of wood vinegar yield, specific gravity, pH, color, smell and transparency. The results showed that with an inner volume of the kiln of 12 m³, the charcoal-making cycle required 15 days using an average of 5607 kg of wood. The properties of charcoal were divided into two parts, from the top and bottom parts of the kiln. At all temperatures in the closed kiln, charcoal from the top part had more fixed carbon and a higher heating value than from the bottom part. At a temperature of 700 °C, the top charcoal had the highest fixed carbon and heating values of 82.0% and 7480 kcal/kg, respectively. Analysis using a statistical package with analysis of variance and multiple comparison using Duncan’s multiple range test (DMRT), showed that at all temperatures, there were no significant differences among any of the properties of charcoal  produced in the top part of the kiln. In the bottom part of the kiln, there were significant differences among the fixed carbon and heating values of the charcoal produced at all temperatures. The multiple comparisons showed the means of the charcoal properties at temperatures of 500 °C and 700 °C were different. Other properties of charcoal from the bottom of the kiln were not significantly different. Based on this research, a closed temperature of 700°C should be used to produce high quality charcoal that has a higher heating value and fixed carbon content as well as low volatile matter compared to temperatures of either 500 °C or 600 °C.

Keywords: Thai-Iwate kiln, properties of charcoal