• Korean Chemical Engineering Research
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• v.50 no.2
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• pp.385-389
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• 2012

In this study, torrefaction of mixed softwood chips under anoxic condition was performed to improve energy density and maintain consistent quality of biomass. Characteristics of torrefied biomass depending on reaction time (30 min) and temperature (240, 260,$280^{\circ}C$) were investigated. Torrefaction of mixed softwood chips significantly improved the heating value compared to that of untreated biomass. As the torrefaction temperature was increased, the carbon content of torrefied biomass increased from 46.55 to 55.73%, while its hydrogen and oxygen contents decreased from 6.00 to 5.87% and from 30.55 to 27.21%, respectively. Most of hemicelluloses and volatile compounds were removed during torrefaction. The highest heating value was 5132 kcal/kg when torrefaction was performed at$280^{\circ}C$ for 30 min. It implied that the heating value increased by 13% compared to that of original biomass. However, the condition of effective torrefaction was at $240^{\circ}C$ for 30 min when weight loss and energy yield was considered.

• Korean Chemical Engineering Research
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• v.51 no.4
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• pp.465-469
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• 2013

In this study, we investigated the feasibility of torrefied OPF (oil palm fronds) as the fuel. The torrefaction was performed at 200, 250, 300 and $350^{\circ}C$ during 1 and 2 hours, respectively. As raising the torrefaction temperature and increasing the processing time, the GHV (gross heating value) of torrefied OPFs was increased. Moreover, we found that the torrefaction temperature is more important factor than the processing time. However, the proper torrefaction temperature was asked because the higher torrefaction temperature leaded to the lower torrefied OPF yield. TGA (thermo-gravimetric analysis) data released that the torrefaction at $250^{\circ}C$ could significantly decompose the hemicellulose and the almost cellulose was decomposed at $300^{\circ}C$. In addition, the grindability of biomass was improved after torrefaction, so that it can reduce energy consumption in comminution.

• New & Renewable Energy
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• v.9 no.3
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• pp.29-35
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• 2013

This research analyzed the fuel characteristic change of spent coffee bean by torrefaction. The calorific value was increased from 4,974 kcal/kg to 6,075 kcal/kg ($260^{\circ}C$, 30min), 6,452 kcal/kg ($270^{\circ}C$, 30min), 6,823 kcal/kg ($280^{\circ}C$, 30min), 6,970 kcal/kg ($260^{\circ}C$, 30min). The highest energy yield was obtained when the spent coffee bean were torrefied on the condition of $280^{\circ}C$, 30min. The moisture absorption rate was decreased from 5.12% to 2.76% when the spent coffee bean were torrefied on the condition of $290^{\circ}C$, 30min. Lignin was increased from 11.33% to 14.39% on the condition of $260^{\circ}C$ 30min. But it did not preferability to torrefy spent coffee bean at temperature of more than $270^{\circ}C$ because lignin decreases to the level that is hard to make pellet.

• Journal of the Korean Wood Science and Technology
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• v.51 no.5
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• pp.381-391
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• 2023

Densification is a technique used to improve biomass quality in wood pellet manufacturing and torrefaction treatment. In this study, the effects of torrefaction on the quality of Calliandra wood pellets were investigated, and pellets of Calliandra wood (Calliandra calothyrsus) and bark were evaluated. The study was conducted using a completely randomized design with two treatment factors, namely torrefaction temperature (250℃ and 300℃) and torrefaction duration (30, 45, and 60 min). The results showed that the interaction between temperature and torrefaction duration significantly affected the compressive strength, proximate value, and calorific value of the torrefied Calliandra wood pellets. An increase in the temperature and torrefaction duration decreased the compressive strength, moisture content, volatile matter content, and ash content of the torrefied Calliandra wood pellets. Conversely, the calorific value of Calliandra wood pellets increased with increasing temperature and torrefaction duration. The best-quality Calliandra wood pellets were produced at a torrefaction temperature and duration of 300℃ and 60 min, respectively. In terms of important quality parameters, ash content of 0.90% and calorific value of 6,303.80 cal/g were observed, which complied with the quality standards of Indonesian National Standard 8675:2018 and Deutsche Industrie Norm 51731.

• Resources Recycling
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• v.30 no.4
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• pp.46-53
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• 2021

Biomass can be considered as chemical energy obtained from nature, and includes all living organisms such as plants, animals, and microorganisms. Biomass is eco-friendly, is easily obtainable from the environment, and can be recycled without special treatment processes. Biomass can also be converted into bioenergy fuel through pyrolysis and fermentation. Therefore, it has been considered as a renewable energy source, which prevents the depletion of natural resources such as fossil fuels. In this study, torrefaction to increase the carbon content in various types of biomass sources (sawdust, rice straw, rice bristles, coffee ground, and waste wood) was conducted under an inert atmosphere and at a temperature of 523~573K. The possibility of using torrefied biomass as an alternative to solid fuel for industrial purposes was analyzed by examining the carbon concentration and combustion behaviors.

• KEPCO Journal on Electric Power and Energy
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• v.2 no.4
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• pp.525-529
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• 2016

Biomass co-firing to existing thermal power plants is one of the most economical and efficient way to reduce $CO_2$ emission from the plant. There are several methods of co-firing and it can be categorized into (1) Parallel co-firing, (2) Indirect co-firing, and (3) Direct co-firing. Parallel co-firing is the most expensive way to high-ratio co-firing because it requires biomass dedicated boiler. Direct co-firing is widely used because it does not need high capital cost compared with the other two methods. Regarding the direct co-firing, it can be classified into three methods- Method 1 does not need retrofit of the facilities because it uses existing coal mills for pulverizing biomass fuels. In this case high-ratio co-firing cannot be achieved because of poor grindability of biomass fuels. Method 2 needs biomass-dedicated mills and revision of fuel streams for the combustion system, and Method 3 needs additional retrofit of the boiler as well as biomass mills. It can achieve highest share of the biomass co-firing compared with other two methods. In Korea, many coal power plants have been adopting Method 1 for coping with RPS(Renewable portfolio standards). Higher co-firing ratio (> 5% thermal share) has not been considered in Korean power plants due to policy of limitation in biomass co-firing for securing REC(Renewable Energy Certificate). On the other hand, higher-share co-firing of biomass is widely used in Europe and US using biomass dedicated mills, following their policy to enhance utilization of renewable energy in those countries. Technical problems which can be caused by increasing share of the biomass in coal power plants are summarized and discussed in this report. $CO_2$ abatement will become more and more critical issues for coal power plants since Paris agreement(2015) and demand of higher share of biomass in the coal power plants will be rapidly increased in Korea as well. Torrefaction of the biomass can be one of the best options because torrefied biomass has higher heating value and grindability than other biomass fuels. Perspective of the biomass torrefaction for co-firing is discussed, and economic feasibility of biomass torrefaction will be crucial for implementation of this technology.

• Journal of The Korean Society of Agricultural Engineers
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• v.59 no.5
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• pp.17-23
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• 2017

In South Korea, 25 % of annual agricultural residues (11.64 million tons) are unused. The hydrophilicity, low lower heating value (LHV), and low energy density of agricultural residues can be obstacles for efficient usage. Torrefaction, a low temperature pyrolysis process, can be a solution to overcome these disadvantage of agricultural residues. In this study, agricultural residues such as bean stem, pepper stem, perilla stem, sorghum stem, acorn shell, and ginkgo shell are torrefied at 200, 230, and $250^{\circ}C$ and evaluated energy properties, respectively. The torrefaction can increase the LHV and energy density rate of agricultural residues from 3,331~4,444 kcal/kg to 4,166~5,830 kcal/kg and 20~30 %, respectively.

• Korean Chemical Engineering Research
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• v.57 no.3
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• pp.372-377
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• 2019

Leaching ($60^{\circ}C$, 5 min) and wet torrefaction ($200^{\circ}C$, 5 min) of empty fruit bunch (EFB) were carried out to improve the fuel properties; each liquid fraction was reused for leaching and wet torrefaction, respectively. In the leaching process, potassium was effectively removed because the leaching solution contained 707.5 ppm potassium. Inorganic compounds were accumulated in the leaching solution by increasing the reuse cycle of leaching solution. The major component of the leached biomass did not differ significantly from the raw material (p-value < 0.05). Inorganic compounds in the biomass were more effectively removed by sequential leaching and wet torrefaction (61.1%) than by only the leaching process (50.1%) at the beginning of the liquid fraction reuse. In the sequential leaching and wet torrefaction, the main hydrolysate component was xylose (2.36~4.17 g/L). This implied that hemicellulose was degraded during wet torrefaction. As in the leaching process, potassium was effectively removed and the concentration was accumulated by increasing the reuse cycle of wet torrefaction hydrolysates. There was no significant change in the chemical composition of wet torrefied biomass, which implied that fuel properties of biomass were constantly maintained by the reuse (four times) of the liquid fraction generated from leaching and wet torrefaction.

• Journal of The Korean Society of Agricultural Engineers
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• v.56 no.6
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• pp.55-62
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• 2014

Torrefaction is considered as a promising pre-treatment for thermochemical utilization of biomass. Torrefaction temperature and time are the critical operation parameters. In this study, investigated were the effects of reaction temperature and time on product composition of torrefaction. scanning electron microscope (SEM) images and thermo gravimetric analyzer (TGA) results were also compared for the effects of the operating parameters. SEM images showed that the pores were observed at the temperature of $250^{\circ}C$ for 30 minutes. Rapid decreases in weight were observed the temperature between 200 and$400^{\circ}C$. Higher heating value of the torrefied biomass was over 5,000 kcal/kg at the temperature of $250^{\circ}C$ for 45 minutes. Energy density, which is defined as the ratio of the energy yield over the mass yield was 1.36 at the temperature of $250^{\circ}C$ for 45 minutes. The energy density was higher up to 1.6 at the temperature of $280^{\circ}C$, which indicates greater loss in mass. The major components of the gas produced in the torrefaction were $CO_2$ and CO, with traces of methane. The total amount of gas was 31.54 l/kg and the calorific value of the gas was $1,164.4Kcal/Nm^3$ at the temperature of $250^{\circ}C$ for 30 minute reaction time. Based on the results of this study, the temperature of effective torrefaction is about $250^{\circ}C$ for 30 to 45 minutes of reaction time. Considering the heating value, it is desirable to utilize the gas for efficient process of torrefaction.

• Resources Recycling
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• v.30 no.1
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• pp.77-82
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• 2021

Reduction of CO2 emissions is an important issue in the steel industry, and the research on carbon materials that can partially replace cokes is necessary to reduce CO2 emissions. Meanwhile, the biomass fuel contains some fixed carbon, and the carbon content in the biomass can be increased by torrefaction. As one of the biomass fuels, coffee grounds contains about 55 mass% of carbon, and its about 270,000 tons are landfilled and incinerated annually in Korea. In addition, research on the recycling process due to the increase in annual coffee consumption is required. In this study, the effect of temperature on the concentration of fixed carbon in coffee grounds was investigated during torrefaction. Moreover, the effects of mixing ratio of torrefied coffee grounds with cokes on the carbon concentration and dissolution efficiency in the metal sample were investigated.