• Journal of the Korean Ceramic Society
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• v.40 no.5
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• pp.481-487
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• 2003

A technique for determination of proportions of char, coal ana coke is needed in order to monitor pulverized coal injection performance in operating blast furnace. Quantitative X-ray powder diffraction analysis can be applied to the problem providing that structural information on carbonaceous materials, coal, char, coke and their mixture are known. Chars were prepared from a coal at different temperatures (1000∼1400$^{\circ}C$) and were characterised by X-Ray powder Diffraction (XRD). The XRD result gave crystallite size (height Lc and diameter, La), aromaticity, number of (002) plane in carbon, and d-spacing. As a result, with increasing heat treat temperature of char, Lc$_{(002)}$, La$_{(10)}$ and number of (002) plane in carbon were increased, and d-spacing and FWHM(Full With Half Maximum) were decreased. Result of prediction of amount of char from the mixtures (char, coke and ore) based on the Lc$_{(002)}$ information of two mixtures (coke and char) showed very close values expected.

• Journal of Energy Engineering
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• v.12 no.3
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• pp.231-240
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• 2003

Reactivity of Char-CO$_2$ gasification of five coals for power generation was investigated with PTGA in the temperature range 850∼1000$^{\circ}C$ and the pressure range 0.5∼2.0 MPa. The effect of coal rank, initial char characteristics and pressure on the reaction rate was evaluated for five chars. The reactivity of low lank coal char was better than that of high rank coal char, and this could be explained with the initial pore structure and surface area of char. Meso/macro-pores of char seems to markedly affect char reactivity by way of providing channels for diffusion of reactant gas into the reactive surface area. For the range of tested pressure, the reaction rate is proportional to CO$_2$ partial pressure and the reaction order ranges from 0.4 to 0.7 for five chars. The effect of total pressure on the reaction rate was small, and kinetic parameters, based on the unreacted core model, were obtained for five chars.

• Journal of the Korea institute for structural maintenance and inspection
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• v.16 no.3
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• pp.67-74
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• 2012

Bio-char, obtained from biomass as a by-product of the pyrolysis process, is used successfully as a soil amendment and carbon sequester in this limited study. Recent and active research from literatures has extended the application of bio-char in the industry to promote sustainability and help mitigate the negative environmental impacts caused by carbon emissions. This study aims to investigate the feasibility of high-carbon bio-char as a carbon sequester and/or admixture in mortar and concrete to improve the sustainability of concrete. This paper presents the experimental results of an initial attempt to develop a cement admixture using bio-char. In particular, the effects of the water retention capacity of bio-char in concrete are investigated. The chemical and mechanical properties (e.g., the chemical components, microstructure, concrete weight loss, compressive strength and mortar flow) are examined using sample mortar mixes with varying replacement rates of cement that contains hardwood bio-char. The experimental results also are compared with mortar mixes that contain fly ash as the cement substitute.

• Journal of Hydrogen and New Energy
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• v.22 no.6
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• pp.884-894
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• 2011

Effects of temperature, volatile content, particle diameter and solid input weight were investigated in the batch fluidized bed reactor using OCN703-1100 particle as oxygen carrier and Roto coal and char as fuels. Two solid fuels represented the best reactivity at different temperature, $900^{\circ}C$ for Roto coal and $950^{\circ}C$ for char, respectively. However, we selected $900^{\circ}C$ as the best operating temperature because the improvement of reactivity of char at $950^{\circ}C$ was negligible. Char represented better reactivity than Roto coal because char contains low volatile than Roto coal. For both solid fuels, reactivities were improved with increasing of the particle diameter. These results were explained by solid mixing tests in a transparent fluidized bed using two char particles having different particle size ranges and OCN703-1100 particle. The bigger particle showed better solid mixing with OCN703-1100 particle, and therefore, represented better reactivity. For both solid fuels, reactivities were improved with increasing of the solid input weight within the experimental conditions of this study because the weight of coarse particles increased with the solid input weight increased, and therefore, these coarse particles can mix well with the oxygen carrier.

• 한국연소학회:학술대회논문집
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• 2012.11a
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• pp.67-70
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• 2012

Many computational fluid dynamic (CFD) simulations have treated the coal kinetics poorly due to large physical domain sizes and high computational complexity, particularly for the recent oxy-coal boilers. Furthermore, some modelers' lack of understanding of the kinetic rate model seems to worsen the simulation accuracy. This study is to suggest the importance of proper use of single-film global kinetic model generally used in CFD code to describe the oxy-fuel combustion of coal char through simple char burnout calculation.

• Journal of Hydrogen and New Energy
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• v.31 no.1
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• pp.122-131
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• 2020

To reduce emissions from coal-fired power plants, researchers focusing on coal and biomass co-firing technology. Biomass, with its carbon-neutral nature and lower quantities of nitrogen and sulfur compared with coals, has a positive impact on coal-fired power generation. Many studies on the combustion of biomass have been conducted, but the study on the combustion characteristics of biomass char is limited. FERPM predicts char combustion characteristics with high accuracy by introducing experimental data-based parameters of biomass char and has not yet been applied in numerical simulation. In this study, FERPM is numerically applied to char combustion of wood pellets representing wood-based biomass and the combustion characteristics are compared with the kinetic/diffusion limited model, intrinsic model, and diffusion limited model.

• Carbon letters
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• v.14 no.1
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• pp.34-39
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• 2013

Acrylonitrile (AN)-acrylamide (AM) copolymers were prepared by nitric acidic hydrolysis of homopolyacrylonitrile. The acrylamino group increased as a function of hydrolysis time, while crystallinity decreased. Differential scanning calorimetry and a thermal gravimetric analysis indicated that the acylamino introduced by acidic hydrolysis effectively enhanced the cyclization reaction at low temperature due to the change of the cyclization reaction mechanism. Char-yield of AN-AM copolymers also gradually increased with increasing hydrolysis time. The maximum char-yield was 49.48% when hydrolized at $23^{\circ}C$ in 65% nitric acid solution for 18 h, which was 30% higher than that of non-acidic hydrolysis of homopolyacrylonitrile. Simulation of the practical process also showed an increase of char yields, where the char yields were 55.43% and 62.60% for homopolyacrylonitrile and copolyacrylonitrile, respectively, with a hydrolysis time of 13 h.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.33 no.11
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• pp.876-885
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• 2009

Char oxidation experiments were performed with a sub-bituminous roto-middle coal in the Drop Tube Furnace (DTF) at atmospheric pressure condition. While temperatures varied between 900, 1100, 1400 $^{\circ}C$, particle size, mass, particle temperature, and CO/$CO_2$ concentration were obtained to be used for kinetic analysis of the char oxidation. This study addresses several different methods to analyze the char consumption rate, which are classified as energy balance method, ash-traced mass method, flue-gas based method, and particle size based method. The char consumption rate obtained with such methods was compared with the results of Monson et al.$^{(24)}$ While there are some differences between them because of differences in experimental apparatus and parameters to be measured, the kinetic results seems to be reasonable enough to be incorporated in a numerical modeling of coal combustion.

• Journal of Korean Society of Water and Wastewater
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• v.34 no.1
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• pp.1-8
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• 2020

In this study, the physicochemical characteristics and fluoride adsorption capacity of the bone char pyrolyzed at different temperatures; 200℃, 300℃, 350℃, 400℃, 500℃, 600℃, and 700℃ were investigated. Analytical studies of the synthesized bone char including; SEM-EDS, XRD, BET and FT-IR, showed the presence of hydroxyapatite(HAP), which is the main substance that adsorbs fluoride from aqueous solutions containing high fluoride concentrations. Bone char pyrolyzed from 350~700℃ specifically revealed that, the lower the temperature, the higher the fluoride adsorption capacity and vice versa. The loss of the fluoride adsorption function of HAP (OH^- band in the FTIR analysis) was interpreted as the main reason behind this inverse correlation between temperature and fluoride adsorption. Bone char produced at 350℃ hence exhibited a fluoride adsorption capacity of 10.56 mgF/g, resulting in significantly higher adsorption compared to previous studies.

• Journal of Climate Change Research
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• v.5 no.4
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• pp.277-284
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• 2014

Biochar application to soil is widely known to have effects of climate change mitigation and soil quality improvement. However, effects of biochar on soil ecosystem are not always positive and some biochars are reported to contain toxic materials which might influence soil ecosystem. In this context, this study aims to investigate behavioral changes of earthworms(Eisenia fetida, Eisenia andrei) in response to different application rates of biochar to artificial soil. Treatment included two types of biochars made from rice husk (RH_Char) and wastewater sludge (SL_Char) with 1% and 10% application rates, respectively. Avoidance test revealed that earthworms did not avoid SL_Char treatments at 1% and 10%, while they rather moved to the RH_Char treatments probably due to higher labile carbon content(Hot water extractable carbon) of the RH_Char. The HWC content of RH_Char was 4 times higher than that of the SL_Char. Results of reproduction test showed that the survival rates, number of juveniles and number of cocoons were not influenced by biochar application except for the treatment of SL_Char at 10% rate. In the SL_Char 10% treatment, fatality was approximately 3.3 times as high as the control and the number of cocoons was 1.3 times higher in the same treatment than the control, indicating that earthworms were under environmental stress. The possible explanation for the stress condition was related to higher Cd, Ni, Cr, and As contents in the SL_Char. Overall results imply that biochar application at low rate might not change earthworms' behavior for the short term, while the reproduction behavior might be negatively influenced under the high application rate.