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RISS 인기검색어
- 검색키워드
- 저자 : Manovic, V. (검색결과 3 건)
- 무료
- 기관 내 무료
- 유료
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Mock, Chinsung,Lee, Hookyung,Choi, Sangmin,Manovic, Vasilije Elsevier 2017 Fuel Vol.200 No.-
<P><B>Abstract</B></P> <P>Torrefaction is a promising method for improving the quality of pulverised solid fuel, as it increases the flame stability, radiative heat transfer and energy density of the fuel. Raw sewage sludge contains less fixed carbon and more ash compounds than other biomasses; consequently, it has poor energy quality with a long ignition delay and forms a relatively low, sooty flame. In this study, we directly investigate the combustion behaviours of particles with varying degrees of torrefaction by burning them at 1340K. The torrefied particles were prepared at different temperatures (473K or 573K) for different residence times (10min or 30min). The experimental parameters examined were the size range of the particles (150–215μm and 255–300μm) and the O<SUB>2</SUB> percentage (10–40%). The particles were entrained from a cold carrier gas into a hot gas stream, igniting a volatile flame that was extinguished a few milliseconds later. These temporal variations in the burning particles were detected by in-situ high-speed photography (7000frames/s). The torrefaction degree affected the flame structure and varied the ignition delay, due to the mismatched reactivity and soot formation at rapid heating rates. The most torrefied sludge particles exhibited a relatively luminous volatile cloud and a large flame, while preserving the duration of volatile combustion. These observations confirm the improved pulverised combustion of the torrefied sludge particles. We also obtained valuable flame parameters (radius, intensity and combustion time) of the differently torrefied sludge particles.</P>
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Combustion Behavior of Relatively Large Pulverized Biomass Particles at Rapid Heating Rates
Mock, Chinsung,Lee, Hookyung,Choi, Sangmin,Manovic, Vasilije American Chemical Society 2016 ENERGY AND FUELS Vol.30 No.12
<P>A pulverized solid fuel particle in a hot gas stream appears to have different characteristic behaviors at several stages, including heat-up, release of volatile matter, gas phase, and solid combustion. The characteristics of these stages may vary distinctly depending on devolatilization rate, the particle temperature history, and its chemical and physical properties. Biomass particles manifest different combustion behavior from that of burning coal particles under the same combustion conditions because they contain more volatiles (less fixed carbon), and they have a relatively lower particle density due to their fibrous structure. This paper presents an experimental study of burning behavior of different types of biomass particles (torrefied wood, coffee waste, and sewage sludge). The main experimental parameters gas temperatures of 1090 and 1340 K, and O-2 concentrations ranging from 10% to 40% were employed to investigate the burning of biomass through a direct-observation approach using a high-speed photography technique at 7000 frames/s. In the case of firing/cofiring, biomass particles must be larger than the coal particles in order to achieve an equivalent thermal balance due to the higher energy density of coal. Therefore, the selected biomass samples were in the size range from 150-215 mu m to 425-500 mu m. The experimental setup has a cross-flow configuration for particle injection in order to enhance interaction between the particle and the two different streams a cold carrier gas at 298 K, and upward-flowing postcombustion gases. It is believed that the employed experimental conditions are similar to those in a realistic furnace with a rapid heating rate of 10(5) K/s. The experimentally significant results, including the effective radii of the volatile flames, degrees of flame intensity, and the maximum size of a particle, are important for validation of models of single biomass particle combustion.</P>
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Mock, C.,Lee, H.,Choi, S.,Yang, W.,Manovic, V. Elsevier Scientific Pub. Co 2017 Fuel processing technology Vol.163 No.-
This study presents the comparative burning behaviours of single solid particles of coal and biomass mixtures for co-firing. In this experimental investigation, a direct observation approach was used to investigate the ignition, flame characteristics and combustion times by means of high-speed photography at 7000 frames per second. Single particles were entrained into a hot gas stream at 1340K and a rapid heating rate of 10<SUP>4</SUP>-10<SUP>5</SUP>K/s. The apparent volatile flames from the prepared particle size groups were observed within 20-50ms. To assess the effect of oxygen concentration, particles were burned for their flame characteristics in a range of 10%-40% O<SUB>2</SUB>. The test particles were sieved into three size groups (215-255μm, 255-300μm and 300-350μm) to assess the effect of particle size. Special particles for the co-firing effect were collected individually from two types of mixed pellet: 20:80 and 50:50 coal/wood. Pure sub-bituminous coal and wood particles were also prepared in order to compare their combustion behaviours. In the experimental setup with a cross-injection configuration, sequential combustion processes were effectively and clearly described in terms of particle displacement with time. The experimental results showed distinguishable flame characteristics from single particles of coal, 50:50 coal/wood, 20:80 coal/wood and wood, including soot flame size and intensity. The impact of high coal-blending ratio caused an increase in the flame size and intensity and the ignition time was close to that of pure coal particles. Quantitative measurements of combustion events on co-firing particles were also discussed in relation to significant impacts of the particle size and the oxygen concentration.
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