본 연구는 반탄화 처리한 낙엽송 및 백합나무 칩을 이용하여 제조한 펠릿의 내구성에 대한 영향 인자를 조사하기 위하여 펠릿 제조 및 내구성 측정, 그리고 제조된 펠릿의 현미경 관찰을 수행하였다. 또한 반탄화 펠릿의 내구성 향상을 위하여 수분 및 바인더를 첨가하여 펠릿을 제조하고, 이에 대한 내구성을 측정하여 수분 및 바인더가 펠릿의 내구성에 미치는 영향을 분석하였다. 반탄화 낙엽송 및 백합나무 목분으로 제조한 펠릿의 내구성은 무반탄화 펠릿과 비교하여 낮았으며, 반탄화 펠릿의 내구성은 230 oC/30분의 조건에서 가장 높았다. SEM-EDX를 이용한 펠릿의 관찰에서 무반탄화 펠릿의 표면에는 리그닌이 광범위하게 분포하고 있었으며, 반탄화 펠릿에서는 리그닌이 국부적으로 응집하여 존재하는 것을 확인할 수 있었다. 펠릿 제조시 목분에 수분 첨가는 반탄화 낙엽송 펠릿의 내구성 향상에 기여하였으나, 반탄화 백합나무 펠릿의 내구성은 수분 첨가와 함께 감소하였다. 한편 반탄화 펠릿의 내구성은 바인더의 첨가와 함께 향상되었으며, 리그닌과 단백질이 전분보다 내구성 향상에 효과적인 것으로 조사되었다. 결과를 종합하면, 반탄화 낙엽송 및 백합나무를 이용한 펠릿 제조시 230 oC 이하의 온도와 30분 이하의 조건에서 반탄화 처리하는 것이 펠릿의 내구성 유지를 위한 적절한 반탄화 조건이라 판단된다. 또한 반탄화 처리한 고비중의 목재를 펠릿의 원료로 이용할 경우 내구성 향상을 위하여 원료에 대한 적절한 함수율 조절이, 그리고 저비중 목재는 함수율 조절보다 반탄화 처리 조건의 조절을 통하여 펠릿 제조용 원료로 이용하는 방안이 효과적일 것으로 생각한다.

This study was conducted to investigate the effects of several variables on the durability of wood pellets fabricated with torrefied larch (LAR) and tulip tree (TUT) chips. Microscopic observation by scanning electron microscope-energy dispersive X-ray spectrometer was also performed to identify the surface of the wood pellets visually. In addition, torrefied-LAR and TUT pellets were fabricated with the addition of moisture, lignin, starch and protein as binders, and durabilities of the pellets were analyzed statistically. Durabilities of torrefied-LAR and TUT pellets were_x000D_ lower than one of non-torrefied-LAR and TUT pellets. Durabilities of both pellets fabricated with the wood chips, which were torrefied with 230 oC and 30 min, were the highest among all torrefaction conditions used in this study. From the microscopic observations, lignin was distributed broadly on the surface of non-torrefied wood pellets, whereas congregated_x000D_ partially on the surface of torrefied wood pellets. Durability of LAR pellets increased with the addition of moisture, but that of TUT pellets was reduced. Addition of binders contributed to increase the durability of LAR and TUT pellets. As a binder, lignin and protein were more effective than starch for improving the durability. In conclusion, mild torrefaction treatment, such as 230 oC and 30 min, might be an optimal condition to minimize the durability reduction of the LAR and_x000D_ TUT pellets. In addition, when torrefied woody materials with high and low specific gravities are used as a raw material for the production of durable wood pellets, it might be required to adjust moisture content and torrefaction conditions of woody materials, respectively.

Wood Pellets Durability Scanning Electron Microscopy Energy Dispersive X-ray Spectrometer Binder

Li YD, Liu H, Biomass Bioenerg., 19(3), 177 (2000)
Peng JH, “A Study of Softwood Torrefaction and Densification,” Lambert Academic Publishing, 1-10 (2013)
Kiel J, “Energy research Centre of the Netherlands,” European Pellet Conference (2011)
Chauvin H, “Torrefaction-Fast Continuous Biomass Depolymerisation System,” Thermya (2009)
Chen WH, Kuo PC, Energy, 35(6), 2580 (2010)
Stelte W, Jonas D, Niels PKN, Hans OH, “Densification Concepts for Torrefied Biomass,” International Energy Agency Bioenergy (2012)
Bae SH, Korean J. Chem. Eng., 28(4), 1023 (2011)
Kim KS, Choi EA, Ryu JS, Lee YP, Park JY, Choi SH, Park SJ, Appl. Chem. Eng., 23(5), 440 (2012)
Na BI, Ahn BJ, Cho ST, Lee JW, Korean Chem. Eng. Res., 51(6), 739 (2013)
Lee JW, Kim YH, Lee SM, Lee HW, Korean Chem. Eng. Res., 50(2), 385 (2012)
Park SJ, Korea Forest Service, 15 (2011)
Ahn BJ, Chang HS, Cho ST, Han GS, Yang I, J. Mokchae Konghak, 41(6), 475 (2013)
Kim ST, Park DH, Yang I, Han GS, Ahn BJ, J. Mokchae Konghak, 43(1), 122 (2015)
Korea Forest Research Institute, “Standard of Wood Pellet,” KFRI No. 2013-5, Seoul, Republic of Korea (2013)
Lehtikangas P, Biomass Bioenerg., 20, 351 (2014)
Obernberger I, Thek G, Biomass Bioenerg., 27(6), 653 (2004)
Stahl M, Granstrom K, Berghel J, Renstrom R, Biomass Bioenerg., 27(6), 621 (2004)
Mani S, Tabil LG, Sokhansanj S, Biomass Bioenerg., 20, 648 (2006)
Bergstrom D, Israelsson S, Ohman M, Dahlqvist SA, Gref R, Boman C, Wasterlund I, Fuel Process. Technol., 89(12), 1324 (2008)
Kim H, Lu G, Li T, Sadakata M, Environ. Sci. Technol., 36, 1607 (2002)
Briggs JL, Maier DE, Watkins BA, Behnke KC, Poultry Science, 78, 1464 (1999)
Kaliyan N, Morey RV, Biomass Bioenerg., 33(3), 337 (2009)
Lee SM, Ahn BJ, Choi DH, Han GS, Jeong HS, Ahn SH, Yang I, Biomass Bioenerg., 48, 1 (2013)
Ahn BJ, Yang I, Kim ST, Park DH, J. of The Korean Society for New and Renewable Energy, 9(4), 40 (2013)
Stevens CA, “Starch Gelatinization and the Influence of Particle Size, Steam Pressure and Die Speed on the Pelleting Process,” Ph. D. dissertation, KS: Kansas State University, Manhattan (1987)