• Journal of Energy Engineering
• /
• v.12 no.1
• /
• pp.49-57
• /
• 2003

Approx. 200.000 bpd vacuum residue oil is produced from oil refineries in Korea, and is supplied to use asphalt, high sulfur fuel oil and for upgrading at the residue hydro-desulfurization unit. Vacuum residue oil has high energy content, however its high sulfur content and high concentration of heavy metals represent improper low grade fuel. To meet growing demand for effective utilization of vacuum residue oil from refineries, recently some of the oil refinery industries in Korea, such as SK oil refinery and LG Caltex refinery, have already proceeded feasibility study to construct 435~500 MWe IGCC power plant and hydrogen production facilities. Recently, KIER (Korea Institute of Energy Research) are studying on the Vacuum Residue gasification process using an oxygen-blown entrained-flow gasifier. The experiment runs were evaluated under the reaction temperature: 1.100~l,25$0^{\circ}C$, reaction pressure: 1~6 kg/$\textrm{cm}^2$G, oxygen/V.R ratio: 0.8~0.9 and steam/V.R ratio: 0.4~0.5. Experimental results show the syngas composition (CO+H$_2$): 85~93%, syngas flow rate: 50~l10 Nm$^3$/hr, heating value: 2,300~3,000 k㎈/Nm$^3$, carbon conversion: 65~92, cold gas efficiency: 60~70%. Also equilibrium modeling was used to predict the vacuum residue gasification process and the predicted values were compared reasonably well with experimental data.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2016.02a
• /
• pp.341-341
• /
• 2016

The discovery of light emission in nanostructured silicon has opened up new avenues of research in nano-silicon based devices. One such pathway is the application of silicon quantum dots in advanced photovoltaic and light emitting devices. Recently, there is increasing interest on the silicon quantum dots (c-Si QDs) films embedded in amorphous hydrogenated silicon-nitride dielectric matrix (a-SiNx: H), which are familiar as c-Si/a-SiNx:H QDs thin films. However, due to the limitation of the requirement of a very high deposition temperature along with post annealing and a low growth rate, extensive research are being undertaken to elevate these issues, for the point of view of applications, using plasma assisted deposition methods by using different plasma concepts. This work addresses about rapid growth and single step development of c-Si/a-SiNx:H QDs thin films deposited by RF (13.56 MHz) and ultra-high frequency (UHF ~ 320 MHz) low-pressure plasma processing of a mixture of silane (SiH4) and ammonia (NH3) gases diluted in hydrogen (H2) at a low growth temperature ($230^{\circ}C$). In the films the c-Si QDs of varying size, with an overall crystallinity of 60-80 %, are embedded in an a-SiNx: H matrix. The important result includes the formation of the tunable QD size of ~ 5-20 nm, having a thermodynamically favorable <220> crystallographic orientation, along with distinct signatures of the growth of ${\alpha}$-Si3N4 and ${\beta}$-Si3N4 components. Also, the roles of different plasma characteristics on the film properties are investigated using various plasma diagnostics and film analysis tools.

• Proceedings of the Korean Fiber Society Conference
• /
• 1990.06b
• /
• pp.36-37
• /
• 1990

In the past, facile dissolution of cellulose has been hampered by the lack of suitable nondegrading solvents. Recently, this problem has been solved in our laboratory by the discovery of an inexpensive, convenient solvent system, that is the mixture of $NH_3\;and\;NH_4SCN$, for cellulose. Also, the $cellulose/NH_3/NH_4SCN$ solution system has been found to form the anisotropic, i.e., liquid crystalline phase. It is believed that both the cholesterio and the nematic phase occur. This finding has prompted extensive on-going researoh on the formation of the liquid crystalline phase from an inexpensive natural source such as cellulose since the nematic phase is envisioned as an excellent precursor sources for products with desirable properties, for example, high modulus and high strength. This interest naturally leads to a desire to understand the theological properties of the nematic phase so that the transformation of the nematic phase to the solid state with desirable properties can be efficiently accomplished, ;From this point of view, the theological behavior of the $cellulose/NH3_/NH_4SCN$ system has been studied as a function of shear rate and shear stress over a wide range of solvent compositions, cellulose concentration, centrifugation and urea contents, Results indicate that the viscosity decreases with increasing shear rate. A marked shear thinning behavior and a quasi-Newtonian behavior were observed in the low shear rate region and in the high shear rate region, respectively for all solvent compositions. The $cellulose/NH_3/NH_4SCN$ solution system only exhibited the viscosity increase with increasing cellulose concentration and failed to show the viscosity drop generally observed at the point of incipience of liquid crystal formation, This may be due to the gel-like nature of the solution by the association of the rodlike molecules into bundles which may serve as crosslinking points giving the cellulose solution a network structure. Also, simply hydrogen bonding may be so restrictive of molecular mobility that a viscosity drop is blocked. In addition to the above results, yield stress and thixotropy were also observed in the $cellulose/NH_3/NB_4SCN$ solution system which are characteristics of liquid crystal and gel, The results of the effect of centrifugation on viscosity show that viscosity decreases by the application of centrifugation. This may be explained by the change of the piled polydomain structure to the dispersed polydomain structure due to the pressure gradient generated during centrifugation.ation.

• Korean Chemical Engineering Research
• /
• v.50 no.4
• /
• pp.666-671
• /
• 2012

Gas hydrates are inclusion compounds formed when small-sized guest molecules are incorporated into the well defined cages made up of hydrogen bonded water molecules. Since large masses of natural gas hydrates exist in permafrost regions or beneath deep oceans, these naturally occurring gas hydrates in the earth containing mostly $CH_4$ are regarded as future energy resources. The heat of dissociation is one of the most important thermal properties in exploiting natural gas hydrates. The accurate and direct method to measure the dissociation enthalpies of gas hydrates is to use a calorimeter. In this study, the high pressure micro DSC (Differential Scanning Calorimeter) was used to measure the dissociation enthalpies of methane, ethane, and propane hydrates. The accuracy and repeatability of the data obtained from the DSC was confirmed by measuring the dissociation enthalpy of ice. The dissociation enthalpies of methane, ethane, and propane hydrates were found to be 54.2, 73.8, and 127.7 kJ/mol-gas, respectively. For each gas hydrate, at given pressures the dissociation temperatures which were obtained in the process of enthalpy measurement were compared with three-phase (hydrate (H) - liquid water (Lw) - vapor (V)) equilibrium data in the literature and found to be in good agreement with literature values.

• Korean Chemical Engineering Research
• /
• v.60 no.1
• /
• pp.116-124
• /
• 2022

In this study, waste air containing ethanol and hydrogen sulfide, was treated by an integrated hybrid system composed of two alternatively-operating UV/photocatalytic reactor-process and biofilter processes of a biofilter system having two units with an improved design (R reactor) and a conventional biofilter (L reactor). Both a pressure drop (△p) per unit process of the integrated hybrid system and a microbe-population-distribution of each biofilter process were observed. The △p of the UV/photocatalytic reactor process turned out very negligible. The △p of the L reactor was observed to increase continuously to 4.0~5.0 mmH₂O (i.e., 5.0~6.25 mmH₂O/m). In case of R reactor, its △p showed the one below ca. 16~20% of the △p of the L reactor. Adopting such microbes-carrying biofilter media with high porosity as waste-tire crumb media, and the improved biofilter design, contributed to △p of this study, reduced by ca. 37~50% and 40~53%, respectively, from the reported △p of conventional biofilter packed with biofilter media of the mixture (50:50) of wood chip and wood bark. In addition, the △p of R reactor in this study, reduced by ca. 80% from the reported △p of conventional biofilter packed with biofilter media of the mixture (75:25) of scoria with high porosity and compost, was mainly attributed to adopting the improved biofilter design. On the other hand, in case of L reactor, the CFU counts in its lowest column was analyzed double as much as those in any other columns. However, in case of R reactor, its CFU counts were bigger by 50% than the one of L reactor and its microbes were evenly distributed at its higher and lower columns of R_dn reactor and R_up reactor. This phenomena was attributed to an even moisture distribution of 50~55% of R reactor at its higher and lower columns. Therefore, R reactor showed superb characteristics in terms of both △p and microbe-population-distribution, compared to L reactor.

• Journal of Korean Society of Environmental Engineers
• /
• v.22 no.2
• /
• pp.241-249
• /
• 2000

In this study, UV-catalyzed $H_2O_2$ oxidation and $H_2O_2$ oxidation to remove contaminants from photo processing chemicals were investigated at various conditions. Photo processing chemicals contains high concentrations of organic compounds and has very low biodegradability. Hydrogen peroxide is subjected to gradual decomposition as metastable substance. In the process, short-lived and highly reactive hydroxyl radicals are formed. The decomposition can be significantly accelerated by use of appropriate catalyst, such as ultraviolet radiation. The experiments were conducted in a UV-free reflecting reactor in batch and a high-pressure mercury lamp was used as UV source. Mixing, cooling and ventilation of the reactor were operated during experiments. In $UV/H_2O_2$ oxidation and $H_2O_2$ oxidation, the removal efficiencies of $COD_{Cr}$, TOC and chromaticity increased with the increase of $H_2O_2$ dosage and were higher in the controlled pH condition of 3 than in original pH condition of 8. In $UV/H_2O_2$ oxidation under the optimum condition of pH 8 and 1.3 stoichiometric $H_2O_2$ dosage, the removal efficiencies of $COD_{Cr}$, TOC and chromaticity were 47.5%, 75.0% and 91.5% respectively and $BOD/COD_{Cr}$ ratio was significantly increased from 0.04 to 0.21.

• Journal of Korean Society of Environmental Engineers
• /
• v.22 no.2
• /
• pp.291-302
• /
• 2000

This experiments have been made to develop of manganese-based sorbent for the removal of hydrogen sulfide from hot coal gases. Manganese-based sorbent were tested in an ambient-pressure fixed-bed reactor to determine steady state $H_2S$ concentrations, breakthrough times and feasibility of the sorbent when subjected to cycle sulfidation and regeneration testing. Effects of particle size of sorbent, temperature of sulfidation, regeneration temperature and regeneration characteristics on the $H_2S$ removal efficiency were investigated. Experimental results showed that the $H_2S$ removal efficiency was optimal when the temperature was about $800^{\circ}C$ and the smaller particle size, the better $H_2S$ removal efficiency but in the range of 0.214~0.631mm didn't influence it much. The equilibrium constant(K) is represented as a log(K)=3.396/T-1.1105 and the utilization efficiency of sorbents was about 92% at $800^{\circ}C$. Regeneration in air produced $SO_2$ concentration as high as 8.5% at $800^{\circ}C$, 8.4% at $850^{\circ}C$, and 8.8% at $900^{\circ}C$ and may be used in sulfuric acid production.

• Proceedings of the Korean Powder Metallurgy Institute Conference
• /
• 2001.11a
• /
• pp.7-7
• /
• 2001

The increasing interest in light weight materials coupled to the need for cost -effective processing have combined to create a significant opportunity for aluminum P/M. particularly in the automotive industry in order to reduce fuel emissions and improve fuel economy at affordable prices. Additional potential markets for Al PIM parts include hand tools. Where moving parts against gravity represents a challenge; and office machinery, where reciprocating forces are important. Aluminum PIM adds light weight, high compressibility. low sintering temperatures. easy machinability and good corrosion resistance to all advantages of conventional iron bm;ed P/rv1. Current commercial alloys are pre-mixed of either the AI-Si-Mg or AL-Cu-Mg-Si type and contain 1.5% ethylene bis-stearamide as an internal lubricant. The powder is compacted in closed dies at pressure of 200-500Mpa and sintered in nitrogen at temperatures between $580~630^{\circ}C$ in continuous muffle furnace. For some applications no further processing is required. although most applications require one or more secondary operations such as sizing and finishing. These sccondary operations improve the dimension. properties or appearance of the finished part. Aluminum is often considered difficult to sinter because of the presence of a stable surface oxide film. Removal of the oxide in iron and copper based is usually achieved through the use of reducing atmospheres. such as hydrogen or dissociated ammonia. In aluminum. this occurs in the solid st,lte through the partial reduction of the aluminum by magncsium to form spinel. This exposcs the underlying metal and facilitates sintering. It has recently been shown that < 0.2% Mg is all that is required. It is noteworthy that most aluminum pre-mixes contain at least 0.5% Mg. The sintering of aluminum alloys can be further enhanced by selective microalloying. Just 100ppm pf tin chnnges the liquid phase sintering kinetics of the 2xxx alloys to produce a tensile strength of 375Mpa. an increilse of nearly 20% over the unmodified alloy. The ductility is unnffected. A similar but different effect occurs by the addition of 100 ppm of Pb to 7xxx alloys. The lend changes the wetting characteristics of the sintering liquid which serves to increase the tensile strength to 440 Mpa. a 40% increase over unmodified aIloys. Current research is predominantly aimed at the development of metal matrix composites. which have a high specific modulus. good wear resistance and a tailorable coefficient of thermal expnnsion. By controlling particle clustering and by engineering the ceramic/matrix interface in order to enhance sintering. very attractive properties can be achicved in the ns-sintered state. I\t an ils-sintered density ilpproaching 99%. these new experimental alloys hnve a modulus of 130 Gpa and an ultimate tensile strength of 212 Mpa in the T4 temper. In contest. unreinforcecl aluminum has a modulus of just 70 Gpa.

• Korean Chemical Engineering Research
• /
• v.50 no.6
• /
• pp.1015-1020
• /
• 2012

Lignite of low rank coal and petroleum coke of high sulfur content can be high potential energy sources for coal gasification process because of their plentiful supply. The steam gasification of lignite, anthracite, and pet coke has been carried out in both an atmospheric thermobalance reactor and a lab-scale fludized bed reactor (0.02 m i.d. ${\times}$ 0.6 m height). The effects of gasification temperature ($600{\sim}900^{\circ}C$) and partial pressure of steam (0.15~0.95 atm) on the gasification rate and on the heating value of product gas have been investigated. The modified volumetric reaction model was applied to the experimental data to describe the behavior of carbon conversion, and to evaluate kinetic parameters of char gasification. The results shows that higher temperature bring more hydrogen in the product syngas, and thus increased gas heating value. The feed rate of steam is needed to be optimized because an excess steam input would lower the gasification temperature which results in a degradation of fuel quality. The rank of calorific value of the product gas was anthracite > lignite > pet coke. Their obtained calorific value at $900^{\circ}C$ with 95% steam feed were 10.0 > 6.9 > 5.7 $MJ/m^3$. This study indicates that lignite and pet coke has a potential in fuel gas production.

• Journal of Oral Medicine and Pain
• /
• v.34 no.1
• /
• pp.11-21
• /
• 2009

This study was conducted to investigate the relationship between systemic diseases and oral malodor. The author measured the volatile sulfur compound(VSC) of the patients who visited Pusan National University Health Promote Center for a comprehensive medical testing. The patients were examined gingival bleeding on probing, CPI index, tongue coating. Their systemic diseases were diagnosed by the specialist. 182 patients consisted of 112 males and 70 females. In this study, Oral $Chroma^{(R)}$ was used to measure oral malodor. This equipment could measure the concentration of intraoral VSC (hydrogen sulfide, methyl mercaptan, dimethyl disulfide). All data were analylized using Statistical Package for the Social Science $12.0^{(R)}$. The result of this study was the followings. 1. There was significant difference of numbers of patient who visited health care center according to the VSC concentration level and the Community Periodontal Index, bleeding on probing, tongue coating. 2. The subjects with hyperlipidemia showed the high level of $CH_3SH$ concentration (p=0.036). The concentration of $H_2S$ tends to be high in the group with abnormal findings on pulmonary fuction test(p=0.086). The concentration of $CH_3SH$ in the groups with abnormal findings on lipid profile test(p=0.130) and bone mineral density test(p=0.099) and abdominal ultrasonograpy(p=0.088) tends to be higher than the other group. 3. The concentration of $(CH_3)_2S$ in the group with abnormal findings on blood pressure test(p=0.113), hepatitis B virus serology(p=0.069), Abdominal ultrasonograpy(p=0.091) tend to be higher than the other group.