• Journal of Korean Society of Environmental Engineers
• /
• v.30 no.8
• /
• pp.768-774
• /
• 2008

To evaluate the effect of the solidified/stabilized sewage sludge on landfill sites, lysimeter tests were conducted. Lysimeters (LR1, LR2, and LR3) were filled with the material(Compost : Fodder : Sand = 10 : 10 : 80) and covered with different types of the cover soils, the G solidified sludge produced from the neutral solidifying chemical agent(LR1), the A solidified sludge produced from the alkali solidifying chemical agent(LR2), and the weathered granite soil(LR3). Those lysimeters were kept at the temperature controlled room with 30 $\pm$ 2$^{\circ}C$ for about 450 days. As the results, it was appeared LR2 > LR1 > LR3 that total gas production rate(L), gas production rate(L/VS(kg)) and cumulative gas(CO$_2$ + CH$_4$) production. There were not significant differences at decrease of the COD$_{Cr}$ in the leachate from LR1 and LR3. Thus, it had been shown that the use of the G solidified sludge as cover soil did not affect the COD$_{Cr}$ in the leachate. The COD$_{Cr}$ from LR2 had been increased since around 250 days because solidified/stabilized sewage sludge became re-slurry. T-N and T-P from LR3 also were higher than LR1 and LR2. Also were, the use of the solidified/stabilized sewage sludge as a cover soil, therefore, did not affect the T-N and T-Pconcentrations in the leachate.

• Asian-Australasian Journal of Animal Sciences
• /
• v.17 no.12
• /
• pp.1663-1668
• /
• 2004

This study was carried out to evaluate the potential nutritive value of commonly found grasses collected at native pasture in West Sumatra, Indonesia during dry and rainy seasons. Variables measured included chemical composition, in vitro digestibility, concentration of Ca, P and Mg, gas production and metabolizable energy (ME) content of the grasses. The results showed that species and season had significant effect on chemical composition and mineral concentration. Crude protein content in the dry season ranged from 6.5% (B. decumbens) to 14.4% (P. maximum) and increased slightly from 7.8% (B. decumbens) to 14. 8% (A. compressus) in the rainy season. Data on fiber fraction showed that grass contained more NDF, ADF and ADL in dry season than in rainy season. Data on mineral concentration showed that C. plectostachyus and P. maximum in dry season had higher Ca than those of other species, while in rainy season P. maximum had highest Ca concentration. In dry season, the DMD varied from 50. 4% (P.purpuphoides) to 59.1% (P. purpureum), while in rainy season ranged from 50.3% (A. gayanus) to 61.8% (P. purpureum). The potential and rate of gas production were significantly (p<0.05) affected by species and season. During dry season, potential of gas production ranged from 21.8 ml/200 mg (A. compressus) to 45.1 ml/200 mg (C. plectostachyus), while in rainy season it varied from 35.6 ml/200 mg (A. gayanus) to 47.5 ml/200 mg (P. purpureum). ME content of grasses varied from 6.0 to 8.3 MJ/kg in dry season and increased slightly from 6.4 to 8.6 MJ/kg in rainy season. Both in dry and rainy seasons, the highest ME content was occurred in P. purpureum and C. plectostachyus. In conclusion, nutritive value of the observed grasses in West Sumatra, Indonesia was relatively higher during rainy season compared with dry season. Pennisetum purpureum and Cynodon plectostachyus had the best nutritive value in both dry and rainy seasons.

• Journal of Powder Materials
• /
• v.12 no.3
• /
• pp.167-173
• /
• 2005

Production of weakly agglomerated nanopowders with the characteristic size of about 10 nm and a narrow particle size distribution is still a topical problem especially if the matter is an acceptable output (>50 g/hour), a high purity of the final product, and a low (energy consumption. The available experience and literature data show that the most promising approach to production of such powders is the evaporation-condensation method, which has a set of means for heating of the target. From this viewpoint the use of pulsed electron accelerators for production of nanopowders is preferable since they allow a relatively simple adjustment of the energy, the pulse length, and the pulse repetition rate. The use of a pulsed electron accelerator provides the following opportunities: a high-purity product; only the target and the working gas will interact and their purity can be controlled; evaporation products will be removed from the irradiation zone between pulses; as a result, the electron energy will be used more efficiently; adjustment of the particle size distribution and the characteristic size of particles by changing the pulse energy and the irradiated area. Considering the obtained results, we developed a design and made an installation for production of nanopowders, which is based on a hollow-cathode pulsed gas-filled diode. The use of a hollow-cathode gas-filled diode allows producing and utilizing an electron beam in a single chamber. The emission modulation in the hollow cathode will allow forming an electron beam 5 to 100 ms long. This will ensure an exact selection of the beam energy. By now we have completed the design work, manufactured units, equipped the installation, and began putting the installation into operation. A small amount of nanopowders has been produced.

• Transactions of the Korean hydrogen and new energy society
• /
• v.11 no.4
• /
• pp.149-159
• /
• 2000

This paper is concerned with the performence of a steam reformer for 25kW class MCFC, which is compared with the theoretically calculated results at various operating conditions. The theoretical $H_2$ production amount and $CH_4$ conversion rate are calculated with variations of temperature and steam/carbon (S/C) ratio using fortran program, and the actual values are measured from flowmeter and gas chromatography. As a result of the comparison of theoretical and actual values, the theoretical $H_2$ production amount is calculated by $24.4m^3/hr$ at the normal operating condition(LNG $9m^3/hr$, S/C ratio 5, absolute pressure $2.77kg/cm^2$, $610^{\circ}C$), but the actual production amount is only $19.4m^3/hr$, which is 79.5% of the theoretical value. Nevertheless, at the normal operating condition, the reformer for 25kW class MCFC performed well for a 2,100 hr long run operation, constantly producing $H_2$.

• Clean Technology
• /
• v.19 no.1
• /
• pp.51-58
• /
• 2013

In this study, kinetics data was obtained for steam reforming reaction of ethane over the nickel catalyst. The variables of steam reforming reaction were reaction temperature, partial pressure of ethane, and mole ratio of steam and ethane. Parameters for the power rate law kinetic model and the Langmuir-Hinshelwood model were obtained from the kinetic data. Also, sizing of steam reforming reactor was performed by using PRO/II simulator. For the steam reforming reaction of ethane, Langmuir-Hinshelwood model determining the reaction rate by the surface reaction was better suited than a simple power rate law kinetic model. On water-gas-shift reaction, power rate law kinetic model was well fitted to the kinetic data. Reactor size can be calculated for production of hydrogen through PRO/II simulation.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.33 no.9
• /
• pp.709-717
• /
• 2009

Heat transfer rate is a very important factor for the performance of a steam reformer because a steam reforming reaction is an endothermic reaction. Coaxial cylindrical reactor is the reactor design which can improve the heat transfer rate. Temperature, fuel conversion and heat flux in the coaxial cylindrical steam reformer are studied in this paper using numerical method under various operating conditions. Langmuir-Hinshelwood model and pseudo-homogeneous model are incorporated for the catalytic surface reaction. Dominant chemical reactions are assumed as a Steam Reforming (SR) reaction, a Water-Gas Shift (WGS) reaction, and a Direct Steam Reforming (DSR) reaction. Although coaxial cylindrical steam reformer uses 33% less amount of catalyst than cylindrical steam reformer, its fuel conversion is increased 10 % more and its temperature is also high as about 30 degree. There is no heat transfer limitation near the inlet area at coaxial-type reactor. However, pressure drop of the coaxial cylindrical reactor is 10 times higher than that of cylindrical reactor. Operating parameters of coaxial cylindrical steam reformer are the wall temperature, the inlet temperature, and the Gas Hourly Space Velocity (GHSV). When the wall temperature is high, the temperature and the fuel conversion are increased due to the high heat transfer rate. The fuel conversion rate is increased with the high inlet temperature. However, temperature drop clearly occurs near the inlet area since an endothermic reaction is active due to the high inlet temperature. When GHSV is increased, the fuel conversion is decreased because of the heat transfer limitation and short residence time.

• Korean Chemical Engineering Research
• /
• v.49 no.4
• /
• pp.485-490
• /
• 2011

Tetrafluoromethane($CF_4$) has been used as etching and chamber cleaning gases for semiconductor manufacturing processes. These gases need to be removed efficiently because of their strong absorption of infrared radiation and long atmospheric lifetime which causes the global warming effect. We have developed a waterjet gliding arc plasma system in which plasma is combined with waterjet and investigated optimum operating conditions for efficient $CF_4$ destruction through enlarging discharge region and producing large amount of OH radicals. The operating conditions are waterjet flow rate, initial $CF_4$ concentration, total gas flow rate, specific energy input. Through the parametric studies, the highest $CF_4$ destruction of 97% was achieved at 2.2% $CF_4$, 7.2 kJ/L SEI, 9 L/min total gas flow rate and 25.5 mL/min waterjet flow rate.

• KSBB Journal
• /
• v.5 no.1
• /
• pp.25-35
• /
• 1990

In the Xanthan gum fermentation by Xanthomonas campestris there are problems of the large energy consumption by long fermentation time, the mass transfer of oxygen and nutrients by high viscous fermentation broth. In this study, the media optimization and the fed batch fermentation were carried out to decrease fermentation time and increase Xanthan gum yield. The $O_2$ uptake rate (OUR) and $CO_2$ evolution rate(CER) which were obtained from the analysis of fermentation exit gas using a gas chromatograph were investigated. As a result, the fermentation time decreased at optimal assimilable nitrogen concentration but increased at poor or rich assimilable nitrogen concentration, the Xanthan gum biosynthesis was stimulated under the limited condition of assimilable nitrogen source and the optimum fermentation medium was obtained as follow; Glucose=30g / l, Peptone=8.0g / l, $K_2HPO_4=2.0g/l$, $MgS0_47H_2O=10g/l$, Sodium acetate=20g/l, Sodium pyruvate=0.5g/1. As the agitation speed and nitrogen concentration increased, the $O_2$ uptake rate and $CO_2$ evolution rate increased. The OUR and CER were 37.3mmol $O_2/\;l$ hr and 20.2 mmol $CO_2/\;L$ hr at peptone 11g / l and agitation speed 990RPM, respectively. In fed batch fermentation, the final concentration of Xanthan gum was enhanced up to 29g / l.

• Applied Chemistry for Engineering
• /
• v.18 no.2
• /
• pp.162-167
• /
• 2007

Hydrogen production and its dynamics were investigated in the continuous anaerobic digestion process using Clostridium beijerinckii Donker 1926. In this work, glucose was used as a substrate and hydraulic retention times (HRT) were 0.5, 0.25 or 0.125 day. The removal efficiency of carbohydrate was over 99% under all of HRT conditions. As HRT was shorter, COD removal efficiency became lower while hydrogen content in the total gas and hydrogen production rate became higher. The cell growth yield and hydrogen production yield were 0.27 g-VSS/g-glucose and 0.26 L/g-glucose, respectively, at the steady state. It is expected that the microorganism is able to produce hydrogen when used in the wastewater treatment containing carbohydrate such as glucose. Also, the results in this study could be applied to the actual hydrogen gas production, a promising alternative energy.

• 한국생물공학회:학술대회논문집
• /
• 2003.04a
• /
• pp.223-227
• /
• 2003

Mevinolic acid (MA), a secondary metabolite produced by a filamentous fungus Aspergillus terreus, is acidic form of lovastatin which has been identified as a powerful cholesterol-lowering agent in humans. When immobilized cell culture was performed, MA production was about 5.3-fold higher than the parallel suspended cell culture. Although the immobilized cells proliferated slowly during exponential in comparison with the suspended cells, oxygen uptake rate and oxygen mass transfer coefficient of the immobilized cell culture were about 1.3- and 2.5- fold higher respectively than those of the parallel suspended cell culture. From these results, it was concluded that MA biosynthesis was closely dependent on the cell growth rate, morphology and oxygen availability.