• Resources Recycling
• /
• v.23 no.1
• /
• pp.40-47
• /
• 2014

Feasibility of utilizing unburned carbon residue in coal ash as a potential precursor for the production of activated carbon was assessed to seek for solution to recycle unburned carbon residue. The unburned carbon concentrate generated from the 4 stages of cleaner flotation has a grade of 87% carbon. The crystalline impurities in the concentrate included quartz and mullite. Unburned carbon had a low specific surface area of $10m^2/g$, which might be related to a high degree of coalification of domestic anthracite coal. Carbon particles were mostly porous and have a turbostratic structure. When 1g of carbon was activated with 6g of KOH powder, the highest specific surface area value of $670m^2/g$ was achieved. Low wettability of unburned carbon particles, which was resulted from high temperature combustion in a boiler, might cause poor pore formation when they were activated by KOH solution. The activated carbon produced in this study developed micropores, with an equivalent quality of general-purpose activated carbon made from coal. Hence, it is concluded that chemically treated unburned carbon can be used for water purification or an alternative to carbon black as it is.

• Journal of the Korea Convergence Society
• /
• v.13 no.2
• /
• pp.123-129
• /
• 2022

This study investigated a differences in grade (G), academic performance (AP), and household income (HI) on adolescents' stress (S), peer relationship (PR), and depression (D) in the coal mine area. The study method was to measure S, PR and D according to different of G, AP, HI for 87 middle school students located in Taebaek and Samcheok Dogye area. As a result, there were significant differences in PR in the 2^nd G, and significant differences were shown in PR and D according to HI and AP. Based on these results, it is necessary to expand the support program for PR of middle school students in the coal mine area, and to develop and support active health promotion programs in the community for stress relief and academic activities, especially for low HI.

• Economic and Environmental Geology
• /
• v.30 no.3
• /
• pp.209-222
• /
• 1997

The Hoenam area, up the Taecheong lake, composed mainly of low grade coal-bearing metapelites within the Ogcheon Supergroup. These coal formations are developed discontinuously several hundred meters and swelling from 10 to 300 cm along the host metapelites. Although the formations have been mined for coal, but already mined out, and the formations were higher content (mean value of 42 samples) of environmental toxic elements as As (13 ppm). Ba (1.81 wt. %), Cd (2 ppm), Cr (188 ppm), Cu (87 ppm), Mo (214 ppm), Pb (25 ppm), Sb (3 ppm), Se (12 ppm), U (55 ppm), V (2124 ppm) and Zn (234 ppm) than the host metapelites and the NASC. The Al, Ti, Mg, K and Na contents in stream sediments derived from the Hando and Bugook mine area were highly concentrations than the samples from the Samseongjeil mine area. The mean value (wt. %) of Fe (10.07), Mn (0.15), Ca (0.84), P (0.18) and Ba (0.77) influenced by the Samseongjeil mine were higher than the other mine drainage sediments. The mean content (ppm) of environmental toxic elements in drainage sediments from the Samseongjeil mine were taken As (2083), Cu (447), Mo (202), Ni (720), Pb (42), U (250), V (1070) and Zn (2632), which are extremely high concentrations against NASC and EPA. Characteristics of elemental behavior and dispersion of the all toxic elements are the same as increased with increasing U, V, and Cu. Rare earth elements in the sediments are enriched with LREE (La, Ce and Nd) from the drainage on strong concentration of toxic elements. The pH of stream water is neutral, but pH of the sediments ranged from 4.92 to 6.93 (mean 6.22), those are slightly acid in the Hando mine area. Major elements in the host rocks at the Hoenam area are mostly depleted especially Ca, excepting Ti and Ba, normalized with NASC. The sediments were highly enriched of Ti, Fe, Mg, Mn and Ba, but depleted of Al, K, Ca, Na and P on the basis of host rocks and NASC. Minor and environmental toxic elements in the host rocks were strongly enriched all elements (As, Cd, Mo, Se, D, V and Zn), excepting Co, Ni and Sr. Enrichment index (mean value) about toxic elements (As, Cr, Cu, Fe, Ni, Pb and Zn) of the sediments in this area have taken 41.35 (Hando mine drainage; 2.73, Samseongjeil mine drainage; 113.14 and Bugook mine drainage; 8.19), those are seriously contaminated by environmental toxic elements.

• Journal of Energy Engineering
• /
• v.23 no.3
• /
• pp.235-240
• /
• 2014

In this study, the torrefaction of food waste was conducted to characterize its product, to find out effect of the operating temperature and to assess the feasibility of being used as fuel. The operating temperature was varid from $180^{\circ}C{\sim}270^{\circ}C$ and heat was provided by using nitrogen gas or waste oil heat carrier. The solid yield and moisture content were reduced were reduced as temperature increased. The moisture content reduction and thermochemical conversion were observed at higher than $240^{\circ}C$. At low operating temperature, heat transfer efficiency was higher with wast oil heat carrier. As temperature increases, there was not difference in heat transfer efficiency of two different heating methods. The lower heating value product was increased from 660 to 6,400 Kcal/kg with nitrogen gas and 6,890 Kcal/kg with waste oil heat carrier. The elemental analysis indicates that, as temperature increases, the carbon content of product increases and oxygen content decreases. From the analysis of O/C and H/C, the torrefaction product was close to low grade coal. The characteristics of fuel converted from the food subsequent thermochemical treatment.

• Economic and Environmental Geology
• /
• v.17 no.4
• /
• pp.289-298
• /
• 1984

Uraniferous black slates of the Okchon sequence occur in Koesan (northeast) through Miwon-Boun (middle) to the southwest off Taejon (southwest) within the Okchon fold belt. The Uraniferous balck slates in the southwest off Taejon are particularly well developed in Chubu (northeast) and Moksso-ri (middle) areas whereas they are less developed in Jinsan (southwest) area. The uraniferous beds range from less than a meter to 40 meters in thickness and range from less than 0.02% $U_3O_8$ (cut-off-grade) to 0.05% $U_3O_8$ in the southwestern district off Taejon. Electron microprobe analysis of uranium-minerals found in graphitic slate samples enables to estimate their major compositions semi-quantitatively so that uraninite, ferro-uranophane and chlopinite are tentatively identified. Uranium-minerals are closely associated with carbon and metal sulfides. Correlation analysis of trace element concentrations revealed that U and F.C., and U and Mo are lineary correlative respectively and their correlation coefficients are positively high whereas those of U and V, U and Mn, and U and Zr are negatively low, implying that uranium mineralization has been closely related with concentrations of carbon and molybdenum. Stable isotope analyses of pyrite sulfur range widely from +11.5% to -23.3% in ${\delta}^{34}S$ values whereas those of graphite carbon fall within a narrow range between -23.3% and -28.9% in ${\delta}^{13}C$ values. The wide range of ${\delta}^{34}S$ values suggests that the sulfur could be of meteoric origin rather than of igneous source. The narrow range of ${\delta}^{13}C$ values, which are close to those of coal, indicates that the graphite is organic carbon in origin. Therefore, it is concluded that the uranium mineralization in the Okchon sequence took place primarily in sedimentary environment rich in organic matter and sulfide ion, both of which served as the reducing agents to convert soluble uranyl complex to insoluble uranium dioxide.

• Applied Chemistry for Engineering
• /
• v.3 no.1
• /
• pp.1-6
• /
• 1992

In this energy and environment conscious age, methanol has come to attention increasingly since the well established process is commercially available to produce methanol from abundant low grade carbonaceous resources ; methane, carbon dioxide, coal and biomass etc. Methanol is a Clean energy source which is a readily storable and transportable liquid. It is elaborated to correlate power generation, city gas and chemical feed stocks including transportation fuel, enhancing the national efficiency of resource utilization as well as reducing the environmental problems for the future via C1 technology. It is emphasized that $CO_2$ could be used to produce methanol as a mean of hydrogen storage as in the nature, which will alleviate the environmental problem such as green house effect.

• Korean Chemical Engineering Research
• /
• v.51 no.4
• /
• pp.506-512
• /
• 2013

Biomass and low-grade coals are known to be better potential sources of energy compared to crude oil and natural gas since these materials are readily available and found to have large reserves, respectively. Gasification of these carbonaceous materials produced syngas for chemical synthesis and power generation. Woodchip, sawdust and lignite were gasified with steam in a thermobalance reactor under atmospheric pressure in order to evaluate their kinetic rate information. The effects of gasification temperature ($600{\sim}900^{\circ}C$) and partial pressure of steam (20~90 kPa) on the gasification rate were investigated. The three different types of gas-solid reaction models were applied to the experimental data to predict the behavior of the gasification reactions. The modified volumetric model predicted the conversion data well, thus the model was used to evaluate kinetic parameters in this study. The observed activation energy of biomass, sawdust and lignite gasification reactions were found to be in reasonable range and their rank was found to be sawdust > woodchip > lignite. The expression of apparent reaction rates for steam gasification of the three solids was proposed to provide basic information on the design of coal gasification processes.