• Journal of the Korea Organic Resources Recycling Association
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• v.18 no.3
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• pp.50-59
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• 2010

A pilot-scale test for production of biogas was conducted in an specially designed anaerobic digester (KH-ABC) in which the highly concentrated organic waste (food-waste and piggery-manure) was treated. The effect of inhibitive material to the reaction on anaerobic digestion and the feasibility of digested fluid for the liquefied fertilizer were investigated. The production rate of biogas, the concentration of methane($CH_4$) in biogas, and the digesting rate of volatile solid(VS) were analyzed in the variance of the operating conditions ; the influent rate, the mixture ratio of food waste and piggery manure, and the hydraulic retention time(HRT), etc. The production rate of biogas increased from 1.2 to $2.0kg-VS/m^3{\cdot}d$ with the organic loading rate(OLR). The most suitable operating conditions were recorded at $6m^3/day$ of an influent rate, 2:3 of the raw material mixture ratio(food waste : piggery manure) and 25 days of HRT, respectively. Under those conditions, the production rate of biogas, the concentration of methane($CH_4$) in biogas and the digesting rate of volatile solid(VS) were $220m^3/day$, 64%, and 70%, respectively. The concentration of inhibitive materials was below toxic standard and the anaerobic digested fluid(raw material mixture ratio of 3:7) could meet the condition of the liquefied fertilizer.

• Applied Chemistry for Engineering
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• v.19 no.5
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• pp.519-525
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• 2008

Biodegradation of toluene, styrene and hydrogen sulfide as model compounds of volatile organic compounds and odor from waste gas was investigated experimentally in a biotrickling filter. This study focussed on the description of experimental results with regard to operating conditions. The effect of varying $H_2S$ load rate and inlet concentration was investigated under autotropic and mixotropic environmental conditions. The $H_2S$ removal efficiencies of greater than 99% were achieved at $H_2S$ loads below $10g/m^3{\cdot}hr$ for each environment. It was observed that the maximum elimination capacity of mixotrophic filter was achieved a little greater than the one of autotrophic filter. The biofiltration of toluene and styrene in trickling bed was examined under different gas flow rates, load rates, and inlet concentrations. Below $40g/m^3{\cdot}hr$ of toluene loading, the elimination capacity and loading were identical and it was completely destroyed. In high loading of toluene, the biotrickling filter was operated at its maximum elimination capacity. In the inlet concentration of 0.2, 0.5, and $1.0g/m^3$, the maximum elimination capacity of toluene showed 40, 45, and $60g/m^3{\cdot}hr$, respectively. After a short adaptation period, it was demonstrated that the results of styrene in originally toluene adapted bioreactor was similar with the ones of toluene. However, the performance of filer for styrene is generally a little lower than for toluene. The operating conditions (including liquid flow rate etc.) allowing the highest removal efficiency should be determined experimentally for each specific case.

• Korean Journal of Labor Studies
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• v.23 no.2
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• pp.109-139
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• 2017

In light that solidarity movements become significant under the situation of 'labor and labor movement' crisis, our study pays attention to the fact that the Hope Bus campaigns made remarkable achievements, and aims to figure out how those campaigns were successful, by focusing on their solidarity networking. The successful operating conditions of solidarity networking in the Hope Bus campaigns are examined in three aspects - the conditions of triggering, forming, and activating. The solidarity networking of Hope Bus campaigns were mainly triggered by the injustice of layoffs by Hanjin Heavy Industry, aerial protest by Jin-sook Kim, and the tragic symbol of the protest site (Crane no. 85). The solidarity movement of Hope Bus could be formed by the mutual trust and cohesive team-building of key network brokers, their utilization and expansion of social movement networks, and massive ripple effect of SNS-mediated communication. The solidarity networking of Hope Bus was effectively activated by open and de-hierarchical operations of the central planning group, active solidarity activities of participant groups, and the provision of 'heuristic experience' for developing the sensibility to labor solidarity. The virtuous combination of those three operating conditions leads to the building of unified forces among social movements, massive civil participation, and meaningful movement outcomes, through the solidarity networking of Hope Bus campaigns.

• Journal of the Korean Institute of Gas
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• v.22 no.4
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• pp.13-26
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• 2018

Currently, local regulations, such as KS Code, do not clearly specify how to calculate the range of hazardous area, so the dispersion modeling program should be used to select dispersion. The purpose of this study is to present a methodology of determining the range of hazardous area which is simpler and more reasonable than modelling by using representative materials and process conditions. Based on domestic and overseas regulations that are currently in effect, variables affecting distance to LFL(Lower Flammable Limit) were selected. A total of 16 flammable substances were modelled for substance variables, process conditions variables, and weather conditions variables, and the statistical analysis selected the variables that affect them. Using the selected variables, a three-step classification method was prepared to select the range of locations subject to explosion hazard.

• Journal of ILASS-Korea
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• v.21 no.2
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• pp.95-103
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• 2016

The effect of pilot injection quantity on the combustion and emissions characteristics of a compression ignition engine with a biodiesel-compressed natural gas (CNG) dual fuel combustion (DFC) system is studied in this work. Biodiesel is used as a pilot injection fuel to ignite the main fuel, CNG of DFC. The pilot injection quantity is controlled to investigate the characteristics of combustion and exhaust emissions in a single cylinder diesel engine. The injection pressure and injection timing of pilot fuel are maintained at approximately 120 MPa and BTDC 17 crank angle, respectively. Results show that the indicated mean effective pressure (IMEP) of biodiesel-CNG DFC mode is similar to that of diesel-CNG DFC mode at all load conditions. Combustion stability of biodiesel-CNG DFC mode decreased with increase of engine load, but no notable trend of cycle-to-cycle variations with increase of pilot injection quantity is discovered. The combustion of biodiesel-CNG begins at a retarded crank angle compared to that of diesel-CNG at low load, but it is advanced at high loads. Smoke and NOx of biodiesel-CNG are simultaneously increased with the increase of pilot fuel quantity. Compared to the diesel-CNG DFC, however, smoke and NOx emissions are slightly reduced over all operating conditions. Biodiesel-CNG DFC yields higher $CO_2$ emissions compared to diesel-CNG DFC over all engine conditions. CO and HC emissions for biodiesel-CNG DFC is decreased with the increase of pilot injection quantity.

• Journal of Korean Society for Atmospheric Environment
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• v.16 no.2
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• pp.141-150
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• 2000

In order to genralize the vertical dispersion of plume at long distances on mesoscale over complex terrain dispersion coefficients data have been obtained systematically according to lapsed time after release by using a composite turbulence water tank that simulates convective boundary layer. Dispersion experiments have been carried out for various combined conditions of thermal turbulence intensity mechanical turbulence intensity and plume release height at slightly to moderately unstable conditions. Results of tracer dispersion experiments conducted using water tank camera and image processing system have been converted into atmospheric dispersion data through the application of similarity law. The equation $\sigma$z/Zi=aX/(b+c X2)0.5 where $\sigma$2; vertical dispersion coefficient zi : mixing height X : dimen-sionaless downwind distance was confirmed to be an appropriate and general equation for expressing $\sigma$2 variation with turbulence intensity and plume release height, The value of "a" was found to be principally affected by mechanical turbulence intensity and that of "b" by mechanical turbulence intensity and release height. It was confirmed that the magnitude of "c" varies with release height. Results of water tank experiments on the relationship of $\sigma$2 vs downwind distance x have been compared with actual atmospheric dispersion data such as CONDORS data and Bowne's nomogram Operating conditions of a composite turbulence water tank for simulating the field turbulence situations of CONDORS experiments and Bowne's $\sigma$2(x) nomogram for suburban area have also been investigated in terms of water temperature difference between convection water tank and bottom plate heating tank grid plate stroke mixing water depth length scale and velocity scale. Moreover the effect of mechanical turbulence intensity on vertical dispersion has been discussed in the light of release height and downwind distance. height and downwind distance.

• Journal of ILASS-Korea
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• v.14 no.4
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• pp.147-152
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• 2009

Since a liquid-phase LPG injection system allows accurate control of fuel injection and increase in volumetric efficiency, it has advantages in achieving higher engine power and lower emissions compared to the mixer type LPG supplying system. However, this system also leads to an unexpected event called icing phenomenon which occurs when moisture in the air near the injector freezes and becomes frost around the nozzle hole due to extraction of heat from surrounding caused by instant fuel vaporization. As a result, it becomes difficult to control air/fuel ratio in engine operation, inducing exacerbation of engine performance and HC emission. One effort to mitigate icing phenomenon is to attach anti-icing injection tip in the end of nozzle. Therefore, in this study, the effect of engine operation parameters as well as surrounding conditions on icing phenomenon was investigated in a bench test rig with commercially-used anti-icing injection tips. The test results show that considerable ice was deposited on the surface near the nozzle hole of the anti-icing tip in low rpm and low load operating conditions in ambient air condition. This is because acceleration of detachment of deposited ice from the tip surface was induced in high load, high rpm conditions, resulting in decrease in frost accumulation. The results of the bench testing also demonstrate that little or no ice was formed at surrounding temperature below a freezing point since the absolute amount of moisture contained in the intake air is too small in such a low temperature.

• Transactions of the Korean hydrogen and new energy society
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• v.27 no.3
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• pp.290-297
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• 2016

The absorbent loss due to degradation in $CO_2$ capture process using aqueous alkanol amine solution has adverse effect on the economics of overall process. The degradation causes absorbent loss, equipment corrosion, foaming, adhesive material producing and viscosity increase in operation. In this study, the degradation characteristics of $CO_2$ capture process using MEA (monoehtanolamine) under various conditions such as $O_2$ partial pressure, $CO_2$ loading and absorbent temperature. The effects of iron, which generated from the equipment corrosion, on absorbent degradation were studied using $Fe_2SO_4$ containing MEA solution. The produced gases were analyzed by FT-IR(Fourier Transform Infrared Spectrophotometer) and the specifically measured $NH_3$ concentration was used as a degradation degree of aqueous MEA solution. The experiments showed that the higher $CO_2$ loadings (${\alpha}$), $O_2$ fraction ($y_{O2}$) and reaction temperature enhanced the more degradation of aqueous MEA solution. Comparing other operation parameters, the reaction temperature most affected on the degradation. Therefore, it could be concluded that the above parameters affects on degradation should be considered for the selections of $CO_2$ absorbent and operating conditions.

• Journal of the Korean Electrochemical Society
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• v.18 no.4
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• pp.172-181
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• 2015

Solid Oxide Fuel Cells (SOFC) continue to be among the most promising alternative energy devices. This paper addresses i-V characteristics of SOFC with a focus on air flow rate along the planar anode electrodes. To address this, detailed Butler-Volmer kinetics are implemented in a general-purpose CFD code FLUENT. The numerical results were validated against experimental data from the literature showing excellent match with i-V polarization data ranging 1V-0.4V. Numerical calculations of fuel cell operation under different flow rare conditions were performed in three-dimensional geometries. Results are presented in terms of concentration distribution of hydrogen, oxygen, and water. The simulations and results indicate that advanced CFD with UDF(User-Defined Function) of Butler-Volmer kinetics can be used to identify the conditions leading to air flow rate and specific surface area and guide development of operating conditions and improve the fuel cell system performance.

• Journal of Biosystems Engineering
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• v.17 no.3
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• pp.229-236
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• 1992

In an effort to localize the spray-dryer which is markedly used for drying food materials, a experiment was carried out with a wheel type atomizer locally designed and manufactured to evaluate the effect of rotational speed, feed rate and physical properties of liquid food material on the droplet size, and to develop a model to predict the droplet size sprayed at various operational conditions. The result are summarized as follows. 1. The frequency of droplet size sprayed from the atomizer at every treatment were similar to normal distributions. 2. Under the test conditions adopted in this study, that is, rotational speed of the atomizer ranging from 15,000 to 20,000 rpm (55.0 m/sec - 73.3 m/sec), feed rate from 14 to 37 kg/hr and viscosity of the material from 1.14 to 350 cP, the mean volume-surface dia. of droplets was decreased as increase in rotational speed and was not affected significantly by the feed rate and viscosity. 3. Through the dimensional analysis, a prediction model was developed as follows : $$\frac{Dvs}{r}=K[\frac{Q}{{\mu}r}]^a[\frac{rN^2}{g}]^b[\frac{{\rho}^2r^3g}{{\mu}^2}]^c[\frac{L}{r}]^d$$ and it was proved that the above model was better in degree of fitness than other models reported. 4. A prediction equation for the droplet size sprayed from the atomizer under the test was expressed as follows : $$\frac{Dvs}{r}=0.0215[\frac{Q}{{\mu}r}]^{0.06}[\frac{rN^2}{g}]^{0.3314}[\frac{{\mu}^2}{{\rho}^2r^3g}]^{0.0158}$$.