Investigation of transformation characteristics from wood to charcoal at elevated temperature

1. IUFRO conference 2007 in Taiwan Investigation of transformation characteristics from wood to charcoal at elevated temperature Sung-Min Kwon · Nam-Hun Kim (Department of Wood Science & Engineering, College of Forest and Environmental Sciences, Kangwon National University, Korea)

2. Charcoal ? IUFRO conference 2007 in Taiwan Charcoal is the solid residue from the pyrolysis of wood. The best materials for making charcoal in Korea are the oak woods such as Quercus variabilis, Quercus mongolica and Quercus dentata. * Characteristics of charcoal Carbon content : ca. 80 - 90% pH : ca. 8 - 9 Heating value : ca. 7000cal/g Specific surface: ca. 200-400m2/g Production of charcoalwith a Korean traditional kiln

3. Utilization of charcoal IUFRO conference 2007 in Taiwan Charcoal is used in variety ways. • Agriculturaluses • Industrial uses • Improvement of environmental pollution Soil improvement Gases livestock feed additive Activated carbon Pores Activated carbon adsorption Air purification

4. Early studies IUFRO conference 2007 in Taiwan Many studies were focused on the charcoal: • Anatomical and physical characteristics; Beall et al. (1974), Cutter et al. (1980), Prior and Alvin (1983) Angeles (2001), Kim and Hanna (2006) … • Chemical characteristics; Sadakata et al. (1987), Kumar et al. (1992), Nishimiya et al. (1998), Marshall et al. (2005), Trompowsky et al. (2005) … • Carbon absorption; Ehrburger and Lahaye (1982), Pastor-Villegas et al. (2007), Sakurovs et al. (2007), Bornemann et al. (2007) …

5. Major Questions IUFRO conference 2007 in Taiwan What happen? Wood Charcoal

6. IUFRO conference 2007 in Taiwan Carbonization process Carbonization 1600 3000 600 1800 Thermal decomposition Graphitization 260 800 Charcoalization 160 450 0 500 1000 1500 2000 2500 3000 Charring temperature (°C) [Ishihara S. Journal of Japan Wood Research Society. 42(8):717-723 (1996)]

7. Hemicellulose decomposition Lignin decomposition Generating gases (CO, H, CH4) 250 500 Water evaporation Cellulose decomposition 225 325 305 375 0 100 200 300 400 500 Decomposition of wood components IUFRO conference 2007 in Taiwan Charring temperature (°C) [Prins M.J., Krzysztof K.J. and Janssen F.J.J.G., J. Anal. Appl. Pyrolysis. 77:28-34 (2006).]

8. IUFRO conference 2007 in Taiwan Objective of this study • Up to now, the transition characteristic from wood to charcoal has not been clearly understood. • Clarifying the transition characteristics from wood to charcoal during carbonization process.

9. IUFRO conference 2007 in Taiwan Experimental • We focused on : • Changes of - volumetric shrinkage - weight loss - vessel diameter - pH - cell wall morphology - crystal structure

10. Material and Methods • Sample tree Table 1. Characteristics of sample tree Species DBH* (cm) Age Green Moisture Content(%) Green density (Wg/Vg) (g/cm3) Locality Latitude Longitude Sapwood Heartwood Sapwood Heartwood Quercus variabilis 20.3 41 63.5 59.5 1.07 1.11 Chunchon Korea 37°88’N 127°72’E *Diameter at Breast Height IUFRO conference 2007 in Taiwan

11. Materials and Methods IUFRO conference 2007 in Taiwan 10mm(T) 10mm(R) Chamber 20mm(L) N2 gas Sapwood The electric furnace used for carbonization. (HT 16/16; Supertherm, Germany) Heartwood Specimens for carbonization

12. Materials and Methods IUFRO conference 2007 in Taiwan • Carbonization using an electric furnace Chamber Heating N2 gas (1kg/cm2) Chamber • Target temperature: 310, 320, 330, 340 • and 350°C • Heating time to target temperature: 30 minutes N2 gas (1kg/cm2) Samples Control condition Heating Chamber • Residence time : 10 minutes Chamber N2 gas (1kg/cm2) Cooling Sand Electric furnace

13. V1 - V2 V1 W1 - W2 W1 - VS (%) = - WL (%) = X 100 X 100 Material and Methods IUFRO conference 2007 in Taiwan • Volumetric shrinkage and weight loss V1 :the volume of original wood V2 :the volume of carbonized wood W1 :the weight of original wood W2 :the weight of carbonized wood • Diameter of vessel - Measuring microscope (Nicon, MM-40). - Image analyzer (IMT, i-Solution) • pH - pH meter (inoLab, pH Level 2)

14. Material and Methods IUFRO conference 2007 in Taiwan • Scanning electron microscopy (SEM) - Smooth surfaces in three-plane were obtained by cutting with a sliding microtome. - Coating : gold, about 100Å thick, Ion sputtering coater (Cressington, 108). - Scanning electron microscope (JEOL JSM-5510, 15~20kV). • X-ray diffraction method - Sample dimensions : 1mm (R) × 10mm (T) × 10mm (L). - X-ray diffractometer (RIGAGU, DMAX 2100V) : Nickel-filtered CuKα radiation (tube voltage: 40 kV, filament current: 40 mA)

15. Results and Discussion IUFRO conference 2007 in Taiwan • Visual observation Control Control Sapwood Heartwood Fig. 1 Carbonized woods of Quercus variabilis at different temperatures.

16. IUFRO conference 2007 in Taiwan Results and Discussion Wood 310°C 200㎛ 200㎛ Wood 320°C 200㎛ 200㎛ Fig. 2 Quercus variabilis wood (left) and the carbonized wood (right) at different temperatures.

17. Wood 330°C 200㎛ 200㎛ 340°C Wood 200㎛ 200㎛ Wood 350°C 200㎛ 200㎛ Results and Discussion IUFRO conference 2007 in Taiwan Fig. 2-1 Quercus variabilis wood(left) and the carbonized wood(right) at different temperatures.

18. IUFRO conference 2007 in Taiwan Results and Discussion • Volumetric shrinkage Fig. 3 Changes of volumetric shrinkage during carbonization at different temperatures. 

19. IUFRO conference 2007 in Taiwan Results and Discussion • Weight loss Fig. 4 Changes of weight loss during carbonization at different temperatures.

20. IUFRO conference 2007 in Taiwan Results and Discussion • Vessel diameter Sapwood Heartwood Tangential direction Radial direction Fig. 5 Changes of vessel diameter during carbonization at different temperatures.

21. IUFRO conference 2007 in Taiwan Results and Discussion • pH 0 Fig. 6 Changes of pH during carbonization at different temperatures.

22. IUFRO conference 2007 in Taiwan Results and Discussion • SEM observation Wood 310°C 320°C Fig. 7 Transverse surfaces of parenchyma cells of Quercus variabilis charred at different temperatures.

23. IUFRO conference 2007 in Taiwan Results and Discussion • SEM observation 330°C 340°C 350°C Fig. 7-1 Transverse surfaces of parenchyma cells ofQuercus variabilis charred at different temperatures.

24. IUFRO conference 2007 in Taiwan Results and Discussion • SEM observation Wood 310°C 320°C Fig. 8 Transverse surfaces of wood fibers of Quercus variabilis charred at different temperatures.

25. IUFRO conference 2007 in Taiwan Results and Discussion • SEM observation 330°C 340°C 350°C Fig. 8-1 Transverse surfaces of wood fibers of Quercus variabilis charred at different temperatures.

26. X-ray diffraction (200) (110) (110) IUFRO conference 2007 in Taiwan Results and Discussion Fig. 9 Equatorial X-ray diffractograms of tangential surfaces of Quercus variabilis charred at different temperatures.

27. Summary IUFRO conference 2007 in Taiwan • Volume of wood samples : • - decreased with increasing the carbonization temperature • - checks were developed along with radial direction • Vessel diameter shrinkage : • - tangential direction > radial direction • Weight loss : • - increased with increasing carbonization temperature • - weight loss rapidly increased at the temperature ranging • from 330 to 340°C

28. Summary Carbonization temperature (°C) 310 320 330 340 350 Cell wall morphology A glazed and amorphous appearance Discernible layers Crystalline cellulose Not detected Detected IUFRO conference 2007 in Taiwan

29. IUFRO conference 2007 in Taiwan Thank you for your attention ! More information : kimnh@kangwon.ac.kr