• Clean Technology
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• v.19 no.3
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• pp.333-341
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• 2013

This paper presents results on $CO_2$ gasification of 17 raw coals containing a wide range of volatile matter (21-57 wt%). The gasification is performed using a TGA under $CO_2$ and also under $N_2$ atmosphere. An amount of weight loss with increasing temperature is proportional to that of volatile matter in a coal under $N_2$ atmosphere. Reactivity of $CO_2$ gasification also increases with a content of volatile matter. However, the correlation is a little scattered. Oxygenated functional groups in a coal are generally reactive and therefore, an increase in O/C ratio leads to enhanced reactivity. However, $CO_2$ reactivity is affected by neither H/C ratio nor a content of ashes that possibly activate the gasification reaction. These findings are also applicable to steam coal gasification and the reactivity series are confirmed in the test at a fixed bed reactor.

• Carbon letters
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• v.28
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• pp.31-37
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• 2018

This paper examines a simple one-step and catalyst-free method for synthesizing carbon nanoparticles from aliphatic alcohols and n-hexane with linear molecule formations by using a stable solution plasma process with a bipolar pulse and an external resistor. When the external resistor is adopted, it is observed that the current spikes are dramatically decreased, which induced production of a more stable discharge. Six aliphatic linear alcohols (methanol-hexanol) containing carbon with oxygen sources are studied as possible precursors for the massive production of carbon nanoparticles. Additional study is also carried out with the use of n-hexane containing many carbons without an oxygen source in order to enhance the formation of carbon nanoparticles and to eliminate unwanted oxygen effects. The obtained carbon nanoparticles are characterized with field emission-scanning electron microscopy, energy dispersive X-ray spectroscopy, and Raman spectroscopy. The results show that with increasing carbon ratios in alcohol content, the synthesis rate of carbon nanoparticles is increased, whereas the size of the carbon nanoparticles is decreased. Moreover, the degree of graphitization of the carbon nanoparticles synthesized from 1-hexanol and n-hexane with a high carbon (C)/oxygen (O) ratio and low or no oxygen is observed to be greater than that of the carbon nanoparticles synthesized from the corresponding materials with a low C/O ratio.

• Applied Science and Convergence Technology
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• v.26 no.5
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• pp.118-128
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• 2017

The scope of this work is to determine and compare the effect of electron temperature ($T_e$) and number density ($N_e$) on the yield rate and concentration of reactive chemical species ($^{\bullet}OH$, $H_2O_2$ and $O_3$) in an argon, air and oxygen injected negative DC (0-4 kV) capillary discharge with water flow(0.1 L/min). The discharge was created between tungsten pin-to pin electrodes (${\Phi}=0.5mm$) separated by a variable distance (1-2 mm) in a quartz capillary tube (2 mm inner diameter, 4 mm outer diameter), with various gas injection rates (100-800 sccm). Optical emission spectroscopy (OES) of the hydrogen Balmer lines was carried out to investigate the line shapes and intensities as functions of the discharge parameters such as the type of gas, gas injection rate and inter electrode gap distances. The intensity ratio method was used to calculate $T_e$ and Stark broadening of Balmer ${\beta}$ lines was adopted to determine $N_e$. The effects of $T_e$ and $N_e$ on the reactive chemical species formation were evaluated and presented. The enhancement in yield rate of reactive chemical species was revealed at the higher electron temperature, higher gas injection rates, higher discharge power and larger inter-electrode gap. The discharge with oxygen injection was the most effective one for increasing the reactive chemical species concentration. The formation of reactive chemical species was shown more directly related to $T_e$ than $N_e$ in a flowing water gas injected negative DC capillary discharge.

• Resources Recycling
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• v.30 no.5
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• pp.57-66
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• 2021

In this study, we attempted to separate and recover Cu from low-grade copper ore by a hydrometallurgical process. The leaching sample obtained after crushing and sieving by 0.355 mm of low-grade copper ore contained 1.5% Cu, 4.7% Fe, 1.0% Mn, and 0.3% Zn. The Cu in the oxide ore was very well leached into sulfuric acid and 97% Cu leaching efficiency was achieved at 80℃ and 3 M sulfuric acid (H₂SO₄). From the leaching solution, Cu was separated by solvent extraction from Fe, Mn, and Zn using LIX984N. The separation tendency between Cu and other metals was confirmed through the distribution ratio and separation factor. By plotting the McCabe-Thiele Diagram, the optimum condition for recovering Cu is 5 vol.% LIX984N, 2-stage counter-current solvent extraction, and an O/A ratio of 0.5. Using this method, 99% of the Cu was extracted and a CuSO₄ solution was finally obtained that contained 1.6 g/L Cu after the stripping process using 2 M H₂SO₄.

• Journal of Korean Society for Atmospheric Environment
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• v.23 no.3
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• pp.277-285
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• 2007

Porous cordierite beads, of which the average pore size was $130{\mu}m$ and porosity was about 80%, were prepared by the foaming method and then their application as support of the $Pt/{\gamma}-alumina$ catalyst for $NO_x$, reduction with propene was investigated. The pressure drop of a 2 mm porous beads filter was less than that of a 1 mm porous beads filter and the difference in pressure drop between these two increased as the flow rate increased. The catalytic activity of $Pt/{\gamma}-alumina$ washcoated on the porous bead was tested with varying Pt loading $(0.005{\sim}0.1g/cm^3),\;C_3H_6/NO$ mole ratio $(0.5{\sim}8)$, space velocity $(20,000{\sim}30,000h^{-1})$ and oxygen contents (1 and 8). Pt loading of $0.04g/cm^3$ showed the highest activity for $NO_x$ conversion. The $De-NO_x$, test was operated in the temperature range of $200{\sim}400^{\circ}C$ and the best operation temperature of the catalytic filter is about $250^{\circ}C$. As the C/N ratio increased, increase of the $NO_x$, conversion might result from the increase in exhaustion of the amount of oxygen by the reduction of hydrocarbon. $NO_x$ conversion at $20,000h^{-1}$ of space velocity shows a maximum 34% higher conversion than that at $30,000h^{-1}$. On condition that $O_2$ was 5%, space velocity was $20,000h^{-1}$ and the C/N ratio was 8, the $NO_x$ conversion exhibited a maximum of 40% at $250^{\circ}C$.

• Journal of Microbiology and Biotechnology
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• v.10 no.1
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• pp.69-74
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• 2000

The medium for erythritol production by Torula sp. in a 500-ml baffled flask was optimized to be 300 g/I sucrose, 10 g/I yeast extract, 3 g/I $KH_2PO_4$, and 10 mg/I $CuSO_4{\cdot}5H_2O{\;}at{\;}34^{\circ}C$ with initial pH of 5.5. Using this optimal medium, erythritol of 166 g/I was obtained after 140 h of cultivation, corresponding to 55.3% of the erythritol yield from sucrose with a productivity of 1.11 g/I/h. Optimal concentrations of carbbon and nitrogen sources in a fermentor were higher than that in a flask due to the higher oxygen supply of the fermentor. Employing the medium containing 300 g/I or 400 g/I sucrose for the determination of optimal C/N ratio, the C/N ratio was found to be more important than the nitrogen concentration for effective erythritol production, The optimal ratio of yeast extract to sucrose (g/g) was 20. The yield and productivity of erythritol were maximal in the medium containing 400 g/I sucrose and 20 g/I yeast extract. when dissolved oxygen in the culture was increased, the cell mass increased but the erythritol production was manimal in the range of 5 to 10% of dissolved oxygen. Under the optimal the rane of 5 to 10% of dissolved oxygen. Under the optimal culture condition of the fermentor, a final erythritol concentration of 200 gI was obtained after 120 h with a yield of 50% and the productivity was 1.67 g/I/h. The yield was the highest among erythritol-producting microorganisms

• Journal of the Korean Society for Marine Environment & Energy
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• v.9 no.1
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• pp.1-13
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• 2006

A field survey on the spatio-temporal distribution characteristics and origins of organic matter in surface sediments was carried out monthly at six stations in Gamak Bay, South Korea from April 2000 to March 2002. The range of ignition loss(IL) was $4.6{\sim}11.6%(7.1{\pm}1.6%)$, while chemical oxygen demand(CODs) ranged from $12.25{\sim}99.26mgO_2/g-dry(30.98{\pm}19.09mgO_2/g-dry)$, acid volatile sulfide(AVS) went from no detection(ND)${\sim}10.29mgS/g-dry(1.02{\pm}0.58mgS/g-dry)$, and phaeopigment was $6.84{\sim}116.18{\mu}g/g-dry(23.72{\pm}21.16{\mu}g/g-dry)$. The ranges of particulate organic carbon(POC) and particulate organic nitrogen(PON) were $5.45{\sim}23.24 mgC/g-dty(10.34{\pm}4.40C\;mgC/g-dry)$ and $0.71{\sim}2.99mgN/g-dry(1.37{\pm}0.58mgN/g-dry)$, respectively. Water content was in the range of $43.1{\sim}77.6%(55.8{\pm}5.6%)$, and mud content(silt+clay) was higher than 95% at all stations. The spatial distribution of organic matter in surface sediments was greatly divided between the northwestern, central and eastern areas, southern entrance area from the distribution characteristic of their organic matters. The concentrations of almost all items were greater at the northwestern and southern entrance area than at the other areas in Gamak Bay. In particular, sedimentary pollution was very serious at the northwestern area, because the area had an excessive supply of organic matter due to aquaculture activity and the inflow of sewage from the land. These materials stayed longer because of the topographical characteristics of such as basin and the anoxic conditions in the bottom seawater environment caused by thermocline in the summer. The tendency of temporal change was most prominently in the period of high-water temperatures than low-water ones at the northwestern and southern entrance areas. On the other hand, the central and eastern areas did not show a regular trend for changing the concentrations of each item but mainly showed a higher tendency during the low-water temperatures. This was observed for all but AVS concentrations which were higher during the period of high-water temperature at all stations. Especially, the central and eastern areas showed a large temporal increase of AVS concentration during those periods of high-water temperature where the concentration of CODs was in excess of $20mgO_2/g-dry$. The results show that the organic matters in surface sediments in Gamak Bay actually originated from autochthonous organic matters with eight or less in average C/N ratio including the organic matters generated by the use of ocean, rather than terrigenous organic matters. However, the formation of autochthonous organic matter was mainly derived from detritus than living phytoplankton, indicated the results of the POC/phaeopigment ratio. In addition, the CODs/IL ratio results demonstrate that the detritus was the product of artificial activities such as dregs feeding and fecal pellets of farm organisms caused by aquaculture activities rather than the dynamic of natural ocean activities.

• Water for future
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• v.15 no.2
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• pp.23-32
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• 1982

This study is to clarify the relation between the maximum 24 hour rainfall and the daily rainfall of a designated time 10 A.M., using the 506 rainfall datum from 32 rain-guage stations on the Han river basin covering a period of 7 years and trying to estimate the ratio of two data in accordance with the amount of rainfall respectively. The Mononobe's formula, which is widely used in this country, has the value of 2/3 power in it. The "n" was considered instead of 2/3 and derivated for each guaging station. The results make it possible to establish the Ison-n value map, and show that the n value is affected mainly by the topographical conditions. The daily rainfall of a designated time can be modified by the results of this study and expressed as Y(%)=218.25/R$$. But in the case of exceeding 200mm/day, it is recommended to use the 110% for safety. On the problems of intensity-duration concerned with the planning of public works, the formula can be expressed as r$$=fRday/24.(24/t)$$, where "f" is Y(%) divided by 100. As this study was done with the datum within shor period, it is necessary to study more about the "n" and "f" value so as to get previse value in the future.o as to get previse value in the future.

• Journal of the Korean institute of surface engineering
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• v.34 no.5
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• pp.414-420
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• 2001

A 30-kV plasma immersion ion implantation setup (P $I^3$) has been equipped with a self-developed 6'-magnetron to perform hard coatings with enhanced adhesion by P $I^3$D(P $I^3$ assisted deposition) process. Using ICP source with immersed Ti antenna and reactive magnetron sputtering of Ti target in $N_2$/Ar ambient gas mixture, the TiN films were prepared on Si substrates at different pulse bias and ion-to-atom arrival ratio ( $J_{i}$ $J_{Me}$ ). Prior to TiN film formation the nitrogen implantation was performed followed by deposition of Ti buffer layer under A $r^{+}$ irradiation. Films grown at $J_{i}$ $J_{Me}$ =0.003 and $V_{pulse}$=-20kV showed columnar grain morphology and (200) preferred orientation while those prepared at $J_{i}$ $J_{Me}$ =0.08 and $V_{pulse}$=-5 kV had dense and eqiaxed structure with (111) and (220) main peaks. X-ray diffraction patterns revealed some amount of $Ti_{x}$ $N_{y}$ in the films. The maximum microhardness of $H_{v}$ =35 GN/ $M^2$ was at the pulse bias of -5 kV. The P $I^3$D technique was applied to enhance wear properties of commercial tools of HSS (SKH51) and WC-Co alloy (P30). The specimens were 25-kV PII nitrogen implanted to the dose 4.10$^{17}$ c $m^{-2}$ and then coated with 4-$\mu\textrm{m}$ TiN film on $Ti_{x}$ $N_{y}$ buffer layer. Wear resistance was compared by measuring weight loss under sliding test (6-mm $Al_2$ $O_3$ counter ball, 500-gf applied load). After 30000 cycles at 500 rpm the untreated P30 specimen lost 3.10$^{-4}$ g, and HSS specimens lost 9.10$^{-4}$ g after 40000 cycles while quite zero losses were demonstrated by TiN coated specimens.s.

• Journal of the Korean Chemical Society
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• v.31 no.3
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• pp.250-257
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• 1987

The electrical conductances for the thorium (IV) complexes with crown ethers have been measured in DMSO, and water solvents, and the oxidation-reduction reaction mechanisms, electron number and diffusion coefficients in the reversible reduction process have been examined by polarography and cyclic voltammography. The dissociation mole ratio of $Th^{4+}$ and nitrate ion are 1:1 and in aprotic solvent, and 1:4 in protic solvent like as water. The limiting molar conductances of all complexes in aprotic solvent have been found to be in the range of $92.2{\times}159$ $ohm^{-1}cm^2mol^{-1}$. In aprotic solvent, DMSO, the reduction of each complex is reversible by one electron reduction of one step, and the range of diffusion coefficients is obserbed to be $5.83\;10^{-6}{\sim}6.90{\times}10^{-6}$. The complexes which have reduction step were hydrolyzed above at 1.8volt with reference saturated calomel electrode, generating the hydrogen gas. The reaction mechanisms of thorium (IV)-crown ether complexes appear as follows. ${Th_m(IV)L_n(H_2O)_x(NO_3)_{4y}}_=^{DMSO} {\overline{{Th_m(IV)L_n(H_2O)_x(NO_3)_{4y-1}}}^+ + NO_3-$