• Resources Recycling
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• v.29 no.6
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• pp.104-113
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• 2020

Bubble size in froth flotation has long been recognized as a key factor which affects the bubble residence time, the bubble surface area flux (Sb) and the carrying rate (Cr). This paper presents method of bubble size measurement, relationship between operating variables and gas dispersion properties in flotation column. Using high speed camera and image analysis system, bubble size has been directly measured as a function of operating parameters (e.g., superficial gas rate (Jg), superficial wash water rate (Jw), frother concentration) in flotation column. Relationship compared to measured and estimated bubble size was obtained within error ranges of ±15~20% and mean bubble size was 0.718mm. From this system the empirical relationship to control the bubble size and distribution has been developed under operating conditions such as Jg of 0.65~1.3cm/s, Jw of 0.13~0.52cm/s and frother concentration of 60~200ppm. Surface tension and bubble size decreased as frother concentration increased. It seemed that critical coalescence concentration (CCC) of bubbles was 200ppm so that surface tension was the lowest (49.24mN/m) at frother concentration of 200ppm. Bubble size tend to increase when superficial gas rate (Jg) decreases and superficial wash water rate Jw and frother concentration increase. Gas holdup is proportional to superficial gas rate as well as frother concentration and superficial wash water rate (at the fixed superficial gas rate).

• Journal of Korean Society for Atmospheric Environment
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• v.26 no.3
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• pp.245-252
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• 2010

For the purpose of evaluating to remove elemental mercury using SCR (Selective Catalytic Reduction) catalysts, the result of the concentration variation of elemental mercury in lab experiment and field measurement was compared. The effect of the elemental mercury oxidation on commercial catalysts was studied in simulated gas. Three species of SCR catalyst, $V_2O_5-TiO_2$ type, were selected. The elemental mercury reduced 30% without HCl gas in SCR operating condition. But the width of reduction increased 60% at 20 ppm HCl gas. According to the result of field measurement, reduction rate of elemental mercury at SCR outlet showed 60%. The total mercury concentration decreased about 20%. The results were similar to the lab test. The results of chemical analysis of test sample showed increase of mercury concentration but surface change was not observed.

• Journal of Korean Society for Atmospheric Environment
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• v.15 no.5
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• pp.649-655
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• 1999

Biofiltration of polluted gas streams contained $H_2S$ was studied. The experiments were performed in a laboratory-scale reactor with a porous ceramic media inoculated with sulfur oxidizing bacterium, TAS which was isolated from activiated sludge. The concentration of $H_2S$ in the inlet gas varied from 109 to 3,841 ppm, at the various space velocities(SV) of 50 $h^{-1}$ to 250 $h^{-1}$. Various tests have been conducted to evaluate the effects of such parameters as pH, concentration of sulfate ion and retention time on the pressure drop and maximum elimination capacity. The removal efficiency of $H_2S$ decreased as the $H_2S$ concentration or gas velocity increased in the inlet gas. Pressure drop was insignificant in this system. The maximum elimination capacity could reach up to 16.35g-S/kg-dry packing material/day.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.5
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• pp.677-686
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• 2000

The characteristics of combustion and of emissions in pressurized fluidized bed combustor are investigated. The pressure of the combustor is fixed at 6 atm, and the combustion temperatures are set to 850, 900, and $950^{\circ}C$. The gas velocities are 0.9, 1.1, and 1.3 m/s. The excess air ratio is varied from 5 to 35%. The coal used in the experiment is Shenhwa coal in China. All experiments are executed at 2m bed height. Consequently, NOx & $N_2O$ concentration in the flue gas is increased with incresing excess air ratio but $SO_2$ concentration is decreased with incresing excess air ratio. CO concentration is maintained below 100ppm at over 15% of excess air ratio.

• Journal of Environmental Science International
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• v.6 no.5
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• pp.489-496
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• 1997

The arm of this study is to determine harmful radioactive gas($Rn^{222}$)-concentrations in soils and to suggest the anormalous regions of $Rn^{222}$-concentration in Taejeon area. The range of $Rn^{222}$-concentration in the soils (45 samples) of the survey area is 100 to 2, 475 (pCi/L) and mean$\pm$$\sigma$ of those values is 489$\pm$ 505 (pCi/L). The 2% (4 samples) of soil-gas samples (45 ones) collected In the survey area is corresponded to high rusk level, 53% (24 samples) to medium one and 43% (19 samples) to low one. Especially. The $Rn^{222}$-concentration is relatively higher in schistose granite region than in other rock Mts (two-mica granite and biotite ganite) in the survey area. The $Rn^{222}$-concentration is propotional to the uranium contents in the soils. The soil hardness among the various factors is correlative with $Rn^{222}$-concentrations. To prevent the damage from $Rn^{222}$-concentrations, It is necessary to close the cracks of underground structure and to consider methods reducing $Rn^{222}$-concentration for the anormalous regions.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.23 no.4
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• pp.243-250
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• 2011

In order to investigate the effects of PAG oil concentration on heat transfer performance and pressure drop during gas cooling process of $CO_2$, the experiments on fin-tube heat exchanger of $CO_2$ heat pump were performed. The experimental apparatus consists of a gas cooler, a heater, a chiller, a mass flow meter, a pump and measurement system. Experiments were conducted in various experimental conditions, which were inlet temperature($110^{\circ}C$), mass flow rates (50, 55, 60, 65, 70 g/s) and PAG oil concentration(0 to 2.6 wt%). Heat transfer rate decreased with the increase of the oil concentration and the decrease of inlet pressure. And pressure drop increased with the increase of the oil concentration and mass flow rate of refrigerant. The COP reduction by deterioration of gas cooler performance with oil concentration was analyzed. When inlet pressure of gas cooler is 100 bar, the COP reduction was estimated by 6% under 1 wt% of oil concentration.

• Journal of Mechanical Science and Technology
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• v.17 no.4
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• pp.581-589
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• 2003

Film absorption involves simultaneous heat and mass transfer in the gas-liquid system. While the non-absorbable gas does not participate directly In the absorption process. its pretence does affect the overall heat and mass transfer. An experimental study was performed to investigate the heat and mass transfer characteristics of LiBr-H$_2$O solution flow ing over 6-row horizontal tubes with the water vapor absorption in the pretence of non-absorbable gases. The volumetric concentration of non-absorbable gas, air, was varied from 0.17 to 10.0%. The combined effects of the solution flow rate and its concentration on the heat and mass transfer coefficients were also examined. The presence of 2％ volumetric concentration of air resulted in a 25% reduction in the Nusselt number and 41% reduction in the Sherwood number Optimum film Reynolds number was found to exist at which the heat and mass transfer reach their maximum value independent of air contents. Reduced Nusselt and Sherwood numbers. defined as the ratio of Nusselt and Sherwood numbers at given non-absorbable gas content to that with pure water vapor, were correlated to account for the reduction in the heat and mass transfer due to non-absorbable gases in a falling film absorption process.

• Food Science and Biotechnology
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• v.15 no.2
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• pp.298-302
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• 2006

Kochujang was fermented using hot red pepper, meju prepared with soybean and rice, and malt-digested syrup. To reduce salt content, mustard powder (1.2%, w/w) was added to Korean traditional kochujang with 4-10% salt, and microbial characteristics, enzyme activities, and gas formation in kochujang were evaluated during fermentation for 120 days at $25^{\circ}C$. Yeast numbers of all treatments maintained 2.43-2.86 log CFU/g up to 60 days fermentation, indicating salt concentration had no effect on yeast count. Activities of ${\alpha}$- and ${\beta}$-amylases, and neutral and acidic proteases of kochujang added with mustard powder were slightly higher than those of control group. Total accumulative volume of gas produced during fermentation of kochujang without mustard powder (control group) was 5,892 mL/pack, but decreased to 34-99 mL/pack in low-salted kochujang (4 and 6% salt) added with mustard powder. Major gas produced was carbon dioxide (79-80%) with oxygen content less than 1.25%(v/v). Results indicate salt concentration of kochujang could be lowered up to 6-8% by addition of mustard powder without gas formation and quality alteration during distribution.

• Environmental Engineering Research
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• v.17 no.2
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• pp.89-94
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• 2012

Pyrolysis/gasification technology utilizes an energy conversion technique from various waste resources, such as biomass, solid waste, sewage sludge, and etc. to generating a syngas (synthesis gas). However, one of the major problems for the pyrolysis gasification is the presence of tar in the product gas. The tar produced might cause damages and operating problems on the facility. In this study, a gliding arc plasma reformer was developed to solve the previously acknowledged issues. An experiment was conducted using surrogate benzene and naphthalene, which are generated during the pyrolysis and/or gasification, as the representative tar substance. To identify the characteristics of the influential parameters of tar decomposition, tests were performed on the steam feed amount (steam/carbon ratio), input discharge power (specific energy input, SEI), total feed gas amount and the input tar concentration. In benzene, the optimal operating conditions of the gliding arc plasma 2 in steam to carbon (S/C) ratio, 0.98 $kWh/m^3$ in SEI, 14 L/min in total gas feed rate and 3.6% in benzene concentration. In naphthalene, 2.5 in S/C ratio, 1 $kWh/m^3$ in SEI, 18.4 L/min in total gas feed rate and 1% in naphthalene concentration. The benzene decomposition efficiency was 95%, and the energy efficiency was 120 g/kWh. The naphthalene decomposition efficiency was 79%, and the energy yield was 68 g/kWh.

• KSBB Journal
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• v.10 no.2
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• pp.126-130
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• 1995

A membrane gas sensor was developed for the measurement of ethanol concentration during acetic acid fermentation. The fermentation broth including ethanol was permeated through the silicone membrane by synthetic air as a carrier gas and was detected by a semiconductor gas sensor. The optimum conditions of membrane gas sensor were 20m1/min of flow rate and 0.5mm of membrane thickness. In acetic acid fermentation, an on-line measurement of ethanol concentration was conducted by the proposed membrane gas sensor and then the on-line sensor signal, was compared with the result of off-line analysis by gas chromatography. As a result, a correlated response over the range of $0∼70g/\ell$ was shown between membrane gas sensor and gas chromatography and this use of membrane gas sensor was experimentally ascertained for the monitoring and control of bioprocess like acetic acid fermentation.