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Coal and solvent properties and their correlation with extraction yield under mild conditions
Heechan Cho,Kihong Kim,Si Hyun Lee,Myoungwook Mun,Deayang Lee 한국화학공학회 2016 Korean Journal of Chemical Engineering Vol.33 No.7
Coal solvent extraction is a clean coal technology that involves the extraction of organic matter from coal using solvents. In this study, the effects of various coal and solvent properties on extraction yield were studied and their correlations were observed. Solvent extraction was performed for fifteen coal samples of different ranks with eight solvents under mild conditions. Statistical analyses were then conducted to find correlations between the extraction yields and the coal and solvent characteristics. The extraction yield was strongly correlated with the atomic H/C ratio or volatile matter content. Among the solvent properties, the correlation between the electron donor, acceptor number (DNAN) and yield was confirmed to be high. The results of multiple regression showed that positive correlations were found with the content of volatile matter of coal and polar force, DN-AN of solvent. Whereas negative correlations were found with the Ca/Mg content of coal and dispersion force, hydrogen bonding force of solvent. The regressionequation- calculated value was similar to the experimental value.
권지회,Heechan Cho 한국화학공학회 2016 Korean Journal of Chemical Engineering Vol.33 No.10
We introduce a coupled smoothed particle hydrodynamics-discrete element method (SPH-DEM) to describe the two-way interaction between the two phases of a solid-liquid flow. To validate the model, we simulated two test problems: a solid-liquid counter-flow in a periodic box and particle settlement. The simulations correctly predicted the dynamics, and the results showed good agreement with the theory. The developed model was then applied to simulate the slurry coagulation process to examine the coagulation efficiency. When the rotational speed exceeded the normal range, the coagulation rate decreased with time, even though the rate was high during the early stage due to the size separation effect of the particles. Given this result, overly fast stirring appears to have an adverse effect on the coagulation efficiency. The model is applicable to the design of various types of solid-liquid flows.
( Jeongho Kim ),( Heechan Cho ) 한국폐기물자원순환학회(구 한국폐기물학회) 2019 ISSE 초록집 Vol.2019 No.-
Along with the global growth of solar power, there is growing concern about generation of waste including photovoltaic (PV) modules. Since PV module contains valuable resources such as silver, silicon and glass, various recycling attempts are being made, and mechanical, thermal and chemical methods are typical. However, the thermal method consumes enormous energy and generates a considerable amount of harmful gas, and the chemical method takes a long time and generates a large amount of wastewater. To overcome these disadvantages, a combination of microwave heating and mechanical separation was tested. Microwave was chosen to selectively heat the silicon cell layer so that only the portion bonded to the EVA layer was expected to be heated. At a temperature of 100-120 °C, the EVA layer was partially melted and the silicon cell was isolated. As a result, the EVA layer is not completely burned and therefore a lower amount of emission gas is generated. Also, this process is conducted at a relatively low temperature, which can reduce the silicon cell damage as a result of the incineration process. And it has a faster processing time than chemical method, due to its effective heating mechanism. After separating and grinding the silicon cells, the included silicon and silver were separated by density separation process. As a result, the silver concentration increased significantly from 1.4 % to 41.78 %. The increased silver concentration will economically improve the subsequent chemical extraction process.
김곤섭,Gyuhyen Cho,Heechan Won,Daeoh Kwark,원청길 충북대학교 동물의학연구소 2012 Journal of Biomedical and Translational Research Vol.13 No.3
The aim of this study was to investigate the morphological development of fungiform papillae in Korean native goats by scanning electron microscopy (SEM). Tongues were removed from fetuses on days 120 and 150 of gestation and from juveniles on days 30, 60, 90, 120, 150 and 180 after birth. The sizes of fungiform papillae in the newborn were 225.0-250.0 μm, the weaning period of 60-day-old goats were 271-294 μm and the maturing period of 180-day-old goats were 385-398 μm, respectively. The primordia of fungiform papillae had the typical feature of mushroom shape in 120-day-old fetus. In 150-day-old fetus (neonate), fungiform papillae had similar feature as adult form and were gradually increased in size with slight morphological changes until 150-day-old goat. The microridges, microplicae and micropits were well developed on the epithelial surface of lingual papillae from 60 to 150-day-old goat. The results obtained in this study might provide some basic data of the mechanisms that control the morphogenesis and development of the lingual papillae in the ruminants.
Study on characteristics of various extractants for mineral carbonation of industrial wastes
Mun, Myoungwook,Cho, Heechan,Kwon, Jihoe Elsevier 2017 Journal of environmental chemical engineering Vol.5 No.4
<P><B>Abstract</B></P> <P>In this research, blast furnace slag and waste cement were reacted with various acids at the same concentration (0.1M) under atmospheric conditions, in order to determine their efficiency for mineral carbonation. Based on maximum calcium concentration (2400mg/L) and selectivity (99%), waste cement was selected as a suitable material for mineral carbonation, and further experiments were conducted with HCl, CH<SUB>3</SUB>COOH), and NH<SUB>4</SUB>Cl as effective extractants. At low acid concentrations, the concentration of calcium was similar regardless of acid type used. Increasing acid concentration revealed a linear relationship with the maximum ratio of calcium extraction, but the ratio of increment depended on the type of acid. Although the yield of calcium extracted when using NH<SUB>4</SUB>Cl was lower than that extracted when using HCl and CH<SUB>3</SUB>COOH, vaterite was precipitated in carbonation without a basic reagent. Moreover, the NH<SUB>4</SUB>Cl regenerated during carbonation can be reused for calcium extraction. The reaction of waste cement and acids was analyzed using PHREEQC. Even though the initial pH of CH<SUB>3</SUB>COOH was higher than that of HCl for dissociation constants, the equilibrium pH and calcium concentration of extraction solution were similar for the two acids. NH<SUB>4</SUB>Cl showed a lower extraction rate, except at 0.1M. These results were similar to those obtained experimentally. In a periodic fashion, the amount of calcium in the NH<SUB>4</SUB>Cl solution fluctuated within specific values, unlike experimental results. There are two possible reasons for these deviations: (1) kinetics, and (2) lack of thermo-dynamic data of different types for the calcium carbonate polymorphs, with the latter requiring further study.</P>