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A Study on the Spontaneous Ignition Characteristics of Wood Pellets related to Change in Flow Rate

공기유량의 변화에 대한 우드펠릿의 자연발화 특성에 관한 연구

  • Kim, Hyeong-Seok (Department of Safety Engineering Graduate Student, Pukyong National University) ;
  • Choi, Yu-Jung (Department of Fire Protection Engineering Graduate Student, Pukyong National University) ;
  • Choi, Jae-Wook (Department of Fire Protection Engineering, Pukyong National University)
  • 김형석 (부경대학교 대학원 안전공학과) ;
  • 최유정 (부경대학교 대학원 소방공학과) ;
  • 최재욱 (부경대학교 소방공학과)
  • Received : 2019.02.21
  • Accepted : 2019.04.05
  • Published : 2019.04.30
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Abstract

Uses of fossil fuels like coal and oil increases with industrial development, and problems like abnormal climate come up as greenhouse gas increases. Accordingly, studies are actively conducted on eco-friendly renewable energy as a replacement for the main resources, and especially, wood pellets with high thermal efficiency are in the limelight as an alternative fuel in thermal power stations and gas boilers. However, despite a constant increase in their usage, few studies are conducted on their risks like fire and spontaneous combustion. Thus, this study found the auto-ignition temperature and critical ignition temperature of wood pellets with a change in flow rate in a thermostatic bath, using a sample vessel with 20 cm in length, 20 cm in height and 14 cm in thickness to predict their ignition characteristics. Consequently, at the flow rate of 0 NL/min, as the core temperature of the sample increased to higher than the ambient temperature, they ignited at $153^{\circ}C$, when the critical ignition temperature was $152.5^{\circ}C$. At the flow rates of 0.5 NL/min and 1.0 NL/min, it was $149.5^{\circ}C$, and at the flow rate of 1.5 NL/min, it was $147.5^{\circ}C$. Consequently, at the same storage, the more the flow rate, the lower the critical ignition temperature became.

산업이 발달함에 따라 석탄, 석유등 화석연료의 사용이 증대되고 있다. 그 결과 온실가스의 증가와 더불어 이상기후 등의 문제가 발생하게 되었다. 이로 인해 주 자원을 대체 할 수 있는 친환경적인 신재생에너지에 관한 연구가 활발히 진행 중이며, 그 중 열효율이 높은 우드펠릿이 화력발전소, 가스보일러 등에서 대체연료로서 각광받고 있다. 그러나, 우드펠릿의 사용량은 꾸준히 증대 되고 있는 반면 우드펠릿의 사용 시 발생할 수 있는 화재 및 자연발화 등의 위험성에 대한 선행연구가 부족한 실정이다. 이에 본 연구에서는 길이 20 cm, 높이 20 cm, 두께 14 cm의 시료용기를 사용하여 항온조 내부 유량변화에 따른 우드펠릿 최소자연발화온도와 발화한계온도를 구하여 발화특성을 예측하였다. 그 결과 유량이 0 NL/min일 때 $153^{\circ}C$에서 주위온도보다 시료의 중심온도가 상승하여 발화하였고 이때의 발화한계온도는 $152.5^{\circ}C$를 구하였으며, 유량이 0.5 NL/min, 1.0 NL/min에서 발화한계온도인 $149.5^{\circ}C$를 구하였다. 또한 유량이 1.5 NL/min일 때 발화한계온도인 $147.5^{\circ}C$를 구하였으며, 동일한 저장량에서 유량이 증가할수록 발화한계온도가 낮아지는 결과를 도출하였다.

Keywords

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Fig. 1. Schematic diagram of experimental apparatus for spontaneous ignition temperature

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Fig. 2. The relationship between the temperature and time of wood pellets with a 14 cm vessel at 152℃ when the flow rate was 0 NL/min

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Fig. 3. The relationship between the temperature and time of wood pellets with a 14 cm vessel at 153℃ when the flow rate was 0 NL/min

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Fig. 4. The relationship between the temperature and time of wood pellets with a 14 cm vessel at 149℃ when the flow rate was 0.5 NL/min

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Fig. 5. The relationship between the temperature and time of wood pellets with a 14 cm vessel at 150℃ when the flow rate was 0.5 NL/min

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Fig. 6. The relationship between the temperature and time of wood pellets with a 14 cm vessel at 149℃ when the flow rate was 1.0 NL/min

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Fig. 7. The relationship between the temperature and time of wood pellets with a 14 cm vessel at 150℃ when the flow rate was 1.0 NL/min

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Fig. 8. The relationship between the temperature and time of wood pellets with a 14 cm vessel at 147℃ when the flow rate was 1.5 NL/min

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Fig. 9. The relationship between the temperature and time of wood pellets with a 14 cm vessel at 148℃ when the flow rate was 1.5 NL/min

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Fig. 10. Relation between flow rate and spontaneous ignition temperature for wood pellet in 14 cm vessel

Table 1. Characteristics of wood pellet[13-15]

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