Comparative Characterization of a Torrefied Wood Pellet under Steam and Nitrogen Atmospheres

Lee, Yongwoon; Yang, Won Seok; Chae, Taeyoung; Kang, Bruce S.; Park, Jinje; Ryu, Changkook

doi:10.1021/acs.energyfuels.7b03067

Cited by 14 publications

(7 citation statements)

References 23 publications

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“…The pressurized steam is, thus, likely to modify the chemical or physical structure of biomass for releasing metals as volatile compounds. Furthermore, as reported in a study on steam torrefaction at atmospheric pressure, 32 the improvement in grindability by PST was also confirmed (Figure S8). 3.1.2.…”

Section: Resultssupporting

confidence: 81%

“…Furthermore, the pressurized steam has a potential of effectively penetrating into biomass particles and participating in reactions occurring in torrefaction. Nevertheless, studies on torrefaction using pressurized steam have been quite limited, even including torrefaction under ambient-pressure steam or pressurized nitrogen. − Those studies indicated positive effects on the fuel quality such as heating value and grindability. However, the pelletability of biomass torrefied under pressurized steam has been unknown.…”

Section: Introductionmentioning

confidence: 99%

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Improvement of Pelletability of Woody Biomass by Torrefaction under Pressurized Steam

et al. 2019

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The combination of torrefaction and pelletization offers the potential to produce fuels with high energy densities on both mass and volume bases as well as excellent storage and transportation characteristics from biomass. Conventional dry torrefaction, performed in inert atmosphere, inevitably decreases the pelletability of biomass because of the occurrence of a dehydrative reaction and resulting formation of char that inhibits densification in the pelletization. The present study revealed beneficial effects of pressurized steam on the production of torrefied woody biomass with high pelletability. Torrefaction of hardwoods was carried out at 180–250 °C in the presence of saturated steam (pressurized steam torrefaction, PST), and the tensile strength of pellets prepared from torrefied biomass was investigated. PST considerably improved the pelletability of biomass, producing pellets with tensile strength higher by 5.2 times than those from the original biomass. Such improvement in the pelletability was comparable to that by wet torrefaction (torrefaction in compressed water). Meanwhile, PST showed higher energy densification factors on both mass and volume bases than wet torrefaction at mass yields around 70%. The biomass after PST contained a 10–28 wt % acetone-soluble component, which contributed to a limited part of the improved pelletability. The improvement mainly arose from the acetone-insoluble component, which had undergone hydrolytic degradation under pressurized steam rather than charring.

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Section: Resultssupporting

confidence: 81%

Section: Introductionmentioning

confidence: 99%

Improvement of Pelletability of Woody Biomass by Torrefaction under Pressurized Steam

et al. 2019

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“…17,18 The stationary reactor is widely used for biomass torrefaction because of its simple construction and being nonpolluting to raw materials, but it causes uneven heating of torrefied materials. 19,20 Although the fluidized-bed reactor can avoid undesirable uneven heating, it may introduce problems of elutriation and segregation between biomass and inert particles, and it cannot achieve continuous processing of biomass. 21 The conveying screw, transporting or elevating granular materials, provides a possibility of achieving uniform heating and continuous production of materials.…”

Section: Introductionmentioning

confidence: 99%

“…The effects of operating conditions on torrefaction have been studied in many research, , but most studies were performed on laboratory-scale reactors. Thermogravimetric analysis (TGA) and gas chromatography/mass spectrometry (MS) are commonly used methods to investigate the torrefaction mechanism and its influencing factors (such as temperature, heating time, and atmosphere). , The stationary reactor is widely used for biomass torrefaction because of its simple construction and being nonpolluting to raw materials, but it causes uneven heating of torrefied materials. , Although the fluidized-bed reactor can avoid undesirable uneven heating, it may introduce problems of elutriation and segregation between biomass and inert particles, and it cannot achieve continuous processing of biomass . The conveying screw, transporting or elevating granular materials, provides a possibility of achieving uniform heating and continuous production of materials.…”

Section: Introductionmentioning

confidence: 99%

Torrefaction of Sorghum Straw Pellets in a Stationary Reactor with a Feeding Screw

et al. 2020

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The effects of temperature and rotating speed of a feeding screw on the key performance parameters (mass yield, energy yield, and energy densification index) of torrefaction in a stationary reactor with a feeding screw were studied. A comparative experiment of sorghum straw pellet torrefaction was performed on a fixed tube furnace. The results obtained from torrefaction in two reactors indicated that the increase in temperature resulted in a decrease in mass yield and energy yield. As the temperature increased, the volatile content in the solid products decreased and the fixed carbon content increased, indicating that the increase in temperature leads to a deeper degree of biomass thermal degradation. The thermal degradation characteristics of sorghum straw were supplemented by thermogravimetric experimental results measured at 2.5, 5, 10, 20, 40, and 60 °C/min. Compared with the fixed tube furnace, the pellets torrefied in the stationary reactor with a feeding screw were heated more uniformly due to the mechanical rotation of the feeding screw. The effect of the feeding screw on the heat transfer mechanism in the stationary reactor was analyzed based on the results of the torrefaction tests in the two reactors. The temperature distribution in the stationary reactor with a feeding screw was measured by five thermocouple measuring rods, which were evenly installed at 0.05 m to the inner pipe wall along the screw axis. It can be seen from the measured temperature profiles that the heating rate of the pellets heated in the stationary reactor with the feeding screw was variable. For the stationary reactor with the feeding screw loaded with biomass pellets, the optimal rotating speed of the feeding screw for torrefaction in the stationary reactor can be estimated by temperature and the theoretical average heating rate (HRestimation). Comparing the results obtained from the torrefaction tests and thermogravimetric experiments, it can be concluded that the optimal theoretical average heating rate is 4–4.5 °C/min.

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“…The hydrogen content is higher (5.1%) and the oxygen content is lower (19.2%). The energy yield is also slightly higher (69.6%) [ 39 ].…”

Section: Resultsmentioning

confidence: 99%

The Evaluation of Torrefied Wood Using a Cone Calorimeter

2021

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This study focuses on the energy potential and combustion process of torrefied wood. Samples were prepared through the torrefaction of five types of wood: Ash, beech, oak, pine and spruce. These were heated for 2 h at a temperature of 300 °C under a nitrogen atmosphere. Torrefied wood was prepared from wood samples with dimensions of 100 × 100 × 20 mm3. These dimensions have enabled investigation of torrefied wood combustion in compact form. The effect of the external heat flux on the combustion of the samples was measured using a cone calorimeter. The observed parameters, include initiation times, heat release rate and combustion efficiency. The results show that increasing the external heat flux decreases the evenness of combustion of torrefied wood. At the same time, it increases the combustion efficiency, which reached an average value of approximately 72% at 20 kW m−2, 81% at 30 kW m−2 and 90% at 40 kW m−2. The calculated values of critical heat flux of the individual samples ranged from 4.67 kW m−2 to 15.2 kW m−2, the thermal response parameter ranged from 134 kW s0.5 m−2 to 297 kW s0.5 m−2 and calculated ignition temperature ranged from 277 °C to 452 °C. Obtained results are useful both for energy production field and for fire safety risk assessment of stored torrefied wood.

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Comparative Characterization of a Torrefied Wood Pellet under Steam and Nitrogen Atmospheres

Cited by 14 publications

References 23 publications

Improvement of Pelletability of Woody Biomass by Torrefaction under Pressurized Steam

Improvement of Pelletability of Woody Biomass by Torrefaction under Pressurized Steam

Torrefaction of Sorghum Straw Pellets in a Stationary Reactor with a Feeding Screw

The Evaluation of Torrefied Wood Using a Cone Calorimeter

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