• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.10
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• pp.4679-4688
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• 2011

This study was performed to the municipal waste generation amounts and characteristics for B city in Gangwon province, predicted the methane gas generation rate emitted from landfill, and analyzed the possibility of energy recovery to RDF(Refuse Derived Fuel) using combustible waste. The study results showed that the average bulk density of municipal waste for B city was 144.0 kg/$m^3$, and the average ratios of combustible waste were 36.0 % of paper, 21.6 % of vinyl, and 19.7 % of food waste. respectively. In the experiment for heating value, high and low heating value(moisture) was measured to 3,471 $kca{\ell}$/kg and 2,941 $kca{\ell}$/kg, respectively. After the prohibition of burying of food waste in landfill, the heating value of municipal waste was dramatically increased due to increase of the ratio of paper, vinyl, and plastic waste. The prediction results of methane gas generation rate emitted from landfill showed that the gas generation rate is increasing to 2,505.7 CH4 ton/year in 2021. After then, the rate is decreasing gradually. When the RDF facility is installed, the rate is decreasing after peaking at 1,956.9 CH4 ton/year in 2013. The generation rate of LFG emitted from waste landfill of B city was analyzed to 9.92 $m^3$/min, similar to 10.11 $m^3$/min for other city.

• Nuclear Engineering and Technology
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• v.46 no.3
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• pp.395-406
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• 2014

This study provides a fundamental understanding of a cold finger melt crystallization technique by exploring the heat and mass transfer processes of cold finger separation. A series of experiments were performed using a simplified LiCl-CsCl system by varying initial CsCl concentrations (1, 3, 5, and 7.5 wt%), cold finger cooling rates (7.4, 9.8, 12.3, and 14.9 L/min), and separation times (5, 10, 15, and 30 min). Results showed a potential recycling rate of 0.36 g/min with a purity of 0.33 wt% CsCl in LiCl. A CsCl concentrated drip formation was found to decrease crystal purity especially for smaller crystal formations. Dimensionless heat and mass transfer correlations showed that separation production is primarily influenced by convective transfer controlled by cooling gas flow rate, where correlations are more accurate for slower cooling gas flow rates.

• International Journal of Fluid Machinery and Systems
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• v.2 no.4
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• pp.426-430
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• 2009

In order to investigate the design method for a micro centrifugal compressor, which is the most important component of an ultra micro gas turbine, an impeller having the outer diameter of 20mm was designed, manufactured and tested. The designed rotational speed is 500,000 rpm and the impeller has a fully 3-dimensional shape. The impeller was rotated at 250,000 rpm in the present study. The experimental results of the tested compressor with the vaned and the vaneless diffusers were compared. It was found that the vaned diffuser attained the higher flow rate than the vaneless diffuser at the maximum pressure ratio. In addition the maximum pressure ratio was higher for the diffuser having a larger diffuser divergence angle at the high flow rate. These results were compared with those obtained by the prediction method used at the design stage.

• Journal of Microbiology and Biotechnology
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• v.20 no.3
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• pp.615-621
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• 2010

The viability of low-temperature sulfate reduction with hydrogen as electron donor was studied with a bench-scale gas-lift bioreactor (GLB) operated at $9^{\circ}C$. Prior to the GLB experiment, the temperature range of sulfate reduction of the inoculum was assayed. The results of the temperature gradient assay indicated that the inoculum was a psychrotolerant mesophilic enrichment culture that had an optimal temperature for sulfate reduction of $31^{\circ}C$, and minimum and maximum temperatures of $7^{\circ}C$ and $41^{\circ}C$, respectively. In the GLB experiment at $9^{\circ}C$, a sulfate reduction rate of 500-600 mg $l^{-1}d^{-1}$, corresponding to a specific activity of 173 mg ${SO_4}^{2-}g\;VSS^{-1}d^{-1}$, was obtained. The electron flow from the consumed $H_2$-gas to sulfate reduction varied between 27% and 52%, whereas the electron flow to acetate production decreased steadily from 15% to 5%. No methane was produced. Acetate was produced from $CO_2$ and $H_2$ by homoacetogenic bacteria. Acetate supported the growth of some heterotrophic sulfate-reducing bacteria. The sulfate reduction rate in the GLB was limited by the slow biomass growth rate at $9^{\circ}C$ and low biomass retention in the reactor. Nevertheless, this study demonstrated the potential sulfate reduction rate of psychrotolerant sulfate-reducing mesophiles at suboptimal temperature.

• Journal of the Korean Applied Science and Technology
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• v.21 no.3
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• pp.225-230
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• 2004

Synthesis gas is a high valued compound as a basic chemicals at various chemical processes. Synthesis gas is mainly produced commercially by a steam reforming process. However, the process is highly endothermic so that the process is very energy-consuming process. Thus, this study was carried out to produce synthesis gas by the partial oxidation of methane to decrease the energy cost. The effects of reaction temperature and flow rate of reactants on the methane conversion, product selectivity, product ratio, and carbon deposition were investigated with 13wt% Ni/MgO catalyst in a fluidized bed reactor. With the fluidized bed reactor, $CH_4$ conversion was 91%, and Hz and CO selectivities were both 98% at 850$^{\circ}C$ and total flow rate of 100 mL/min. These values were higher than those of fixed bed reactor. From this result, we found that with the use of the fluidized bed reactor it was possible to avoid the disadvantage of fixed bed reactor (explosion) and increase the productivity of synthesis gas.

• Nuclear Engineering and Technology
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• v.33 no.4
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• pp.355-364
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• 2001

In order to evaluate and finally optimize the vitrification condition for combustible dry active waste (DAW), dust and gas generation characteristics were investigated for PE, cellulose, and mixed waste Tests were conducted by varying the operation variables such as melter configuration, excess oxygen amount, and waste feeding rate. Results showed that dust generation characteristics were affected by the operation parameters and the melter＇s configuration is the dominant one. For all tested DAWs, dust generation was reduced by increasing the waste feeding rate and the excessive oxygen amount in the melter. Among waste types, dust amount was decreased by the order of mixed wastes, PE, and cellulose. Other parameters such as temperature variation and operation time have also affected the dust generation. The optimum condition for the DAW vitrification was determined as the melter＇s configuration equipped for minimizing the waste dispersion with 20 kg/h of waste feeding rate and 100% of excessive oxygen supply. CO gas concentration in the off-gas was immediately influenced by the combustion state in the melter, but showed similar trend as the dust generation. For the NOx production during the vitrification process, thermal NOx, which is generated from the Post Combustion Chamber (PCC), rather than fuel NOx was assumed to be dominant. The gas cleaning of efficiencies of the PCC, wet scrubber, and Selective Catalytic Reduction system (SCR) were found to be high enough to keep the concentration of pollutants (CO, NOx, SOx, HCI) in the stack below their relevant emission limits.

• Transactions of the Korean hydrogen and new energy society
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• v.34 no.4
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• pp.327-333
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• 2023

The water gas shift reaction was carried out using the commercial catalyst pellet and the simulated gases expected to occur from waste plastic gasification. In the water gas shift reaction, the high temperature shift reaction and the low temperature shift reaction were continuously performed with CO:H₂O ratio of 1:2, 1:2.5, and 1:3, and the CO conversion and H₂ increase rate were evaluated. The H₂ increase rate increased in order to CO:H₂O ratio of 1:3 > CO:H₂O ratio of 1:2.5 > CO:H₂O ratio of 1:2. The CO conversion showed a high value of more than 97% at each CO:H₂O ratio. The water gas shift reaction at a CO:H₂O ratio of 1:3 showed the highest H2 increase rate and CO conversion.

• KSBB Journal
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• v.20 no.6
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• pp.458-463
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• 2005

[ $H_2$ ] from CO and water was continuously produced in a trickle bed reactor(TBR) using Citrobacter amalonaticus Y19. When the strain C. was cultivated in a stirred-tank reactor under a chemoheterotrophic and aerobic condition, the high final cell concentration of 13 g/L was obtained at 10 hr. When the culture was switched to an anaerobic condition with the continuous supply of gaseous CO, CO-dependent hydrogenase was fully induced and its hydrogen production activity approached 16 mmol/g cell/hr in 60 hr. The fully induced C. amalonaticus Y19 cells were circulated through a TBR packed with polyurethane foam, and the TBR was operated for more than 20 days for $H_2$ production. As gas retention time decreased or inlet CO partial pressure increased, $H_2$ production rate increased but the conversion from CO to $H_2$ decreased. The maximum $H_2$ production rate obtained was 16 mmol/L/hr at the gas retention time of 25 min and the CO inlet partial pressure of 0.4 atm. The high $H_2$ production rate was attributed to the high cell density in the liquid phase circulating the TBR as well as the high surface area of polyurethane foam used as packing material of the TBR.

• Journal of Life Science
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• v.17 no.12
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• pp.1660-1668
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• 2007

The non-ionic surfactant (NIS) Tween 80 was evaluated for its ability to influence invitro cumulative gas production, dry matter digestibility, cellulolytic enzyme activities, anaerobic microbial growth rates, and adhesion to substrates by mixed rumen microorganisms on rice straw, alfalfa hay, cellulose filter paper and tall fescue hay. The addition of NIS Tween 80 at a level of 0.05% increased significantly (P<0.05) in vitro DM digestibility, cumulative gas production, microbial growth rate and cellulolytic enzyme activity from all of substrates used in this study. In vitro cumulative gas production from the NIS-treated substrates; rice straw, alfalfa hay, filter paper and tall fescue hay was significantly (P<0.05) improved by 274.8, 235.2, 231.1 and 719.5% compared with the control, when substrates were incubated for 48 hr in vitro. The addition of 0.05% NIS Tween 80 to cultures growing on alfalfa hay resulted in a significant increase in CMCase (38.1%), xylanase (121.4%), Avicelase (not changed) and amylase (38.2%) activities after 36 h incubation. These results indicated that the addition of 0.05% Tween 80 could greatly stimulate the release of some kinds of cellulolytic enzymes without decreasing cell growth rate in contrast to trends reported with aerobic microorganism. Our SEM observation showed that NIS Tween. 80 did not influence the microbial adhesion to substrates used in the study. Present data clearly show that improved gas production, DM digestibility and cellulolytic enzyme activity by Tween 80 is not due to increased bacterial adhesion on the substrates.

• Journal of The Korean Society of Agricultural Engineers
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• v.64 no.5
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• pp.9-16
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• 2022

Syngas, also known as synthesis gas, synthetic gas, or producer gas, is a combustible gas mixture generated when organic material (biomass) is heated in a gasifier with a limited airflow at a high temperature and elevated pressure. The present research was aimed at modifying the existing LPG engine generator for fully operated syngas. During this study, the designed gasifier-powered woodchip biomass was used for syngas production to generate power. A 6.0 kW LPG engine generator was modified and tested for operation on syngas. In the experiments, syngas and LPG fuels were tested as test fuels. For syngas production, 3 kg of dry woodchips were fed and burnt into the designed downdraft gasifier. The gasifier was connected to a blower coupled with a slider to help the air supply and control the ignition. The convection cooling system was connected to the syngas flow pipe for cooling the hot produce gas and filtering the impurities. For engine modification, a customized T-shaped flexible air/fuel mixture control device was designed for adjusting the correct stoichiometric air-fuel ratio ranging between 1:1.1 and 1.3 to match the combustion needs of the engine. The composition of produced syngas was analyzed using a gas analyzer and its composition was; 13~15 %, 10.2~13 %, 4.1~4.5 %, and 11.9~14.6 % for CO, H₂, CH₄, and CO₂ respectively with a heating value range of 4.12~5.01 MJ/Nm³. The maximum peak power output generated from syngas and LPG was recorded using a clamp-on power meter and found to be 3,689 watts and 5,001 watts, respectively. The results found from the experiment show that the LPG engine generator operated on syngas can be adopted with a de-ration rate of 73.78 % compared to its regular operating fuel.