• Bulletin of the Korean Chemical Society
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• v.17 no.10
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• pp.885-892
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• 1996

The effects of NOx reduction by advanced fuel staging in a small scale combustor (6.6 kWT) have been investigated using propane gas flames laden with ammonia as fuel-nitrogen. The variables which had the greatest influence on NOx reduction were temperature, reducing stoichiometry (relate to main combustion zone stoichiometry, air fraction and reburning fuel fraction) and residence time of reducing zone. NOx reduction was best at the reburning zone temperature of above 1,000 ℃ and reburning zone stoichiometry was 0.85. In terms of residence time of the reburning zone, NOx reduction was effective when burnout air was injected at the point where the reburning zone had been already established. In the advanced fuel staging NOx reduction was relatively large at the burning of higher Fuel-N concentration in the fuel. Under optimum reburning conditions, fuel nitrogen content had a relatively minor impact on reburning efficiency.

• Transactions of the Korean Society of Mechanical Engineers
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• v.11 no.1
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• pp.145-153
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• 1987

Stability limits of a double concentric jets flame and the structure of recirculation zone formed behind a thick burner rim were investigated. To control the flame stability, swirled secondary air flow ranging 0.13-0.71 of swirl number, and air, fuel, and mixture gas injection from an injection coaxial slit set on burner rim were examined. Flame stability limits, flame shapes, lengths of recirculation zone, temperature distributions, residence times, air ratios in the recirculation zone were measured. The following results were obtained. (1) Lean limits were considerably widened by a strong swirl because the recirculation zone was enlarged. (2) At fuel injection as well as mixture injection, lean limits were also extended. But, air injection had no effect on stability limits. (3) Injected gas seems to diffuse into the recirculation zone through its outer boundary surrounded the secondary air. Therefore, chemical structure in the recirculation zone with air injection coincides with that without injection. (4) Injection position had no effect on flame stability limits.

• Environmental Engineering Research
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• v.25 no.3
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• pp.400-408
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• 2020

Hydrodynamic study of Activated Sludge Process (ASP) is important to optimize the reactor performance and detect anomalies in the system. Residence time distribution (RTD) study has been performed using LiCl as tracer on a pilot scale aeration tank (AT) and ASP, treating the pulp and paper mill effluent. The hydraulic performance and treatment efficiency of the AT and ASP at different operating parameters like residence time, recycle rate was investigated. Flow anomalies were identified and based on the experimental data empirical models was suggested to interpret the hydrodynamics of the reactors using compartment modelling technique. The analysis of the RTD curves and the compartment models indicated increase in back-mixing ratio as the mean hydraulic retention time (MHRT) of the tank was increased. Bypassing stream was observed at lower MHRT. The fraction of dead zone in the tank increased by approximate 20-25% with increase in recycle rate. The fraction of the stagnant zone was found well below 5% for all performed experiments, which was under experimental error. The substrate removal of 91% for Chemical oxygen demand and 96% for Biochemical oxygen demand were observed for the ASP working at a hydraulic mean residence time 39 h MRT with a 20% recycling of activated sludge.

• Journal of Korean Society for Atmospheric Environment
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• v.10 no.E
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• pp.303-310
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• 1994

The effects of NOx reduction by new staged fuelling system in a small scale combustor (6.6 ㎾$_{T}$) have been investigated using propane gas flames laden with ammonia as fuel-nitrogen. The variables which had the greatest influence on NOx reduction were temperature, reducing stoichiometry( related to main combustion zone stoichiometry, air fraction and returning fuel fraction ) and residence time. The best NOx reduction was observed at the reburning zone stoichiometry of 0.85. In terms of residence time of the reburning zone, NOx reduction was effective when burnout air was injected at the Point where the reburning zone has been already established.d.

• Journal of the Korean Society of Combustion
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• v.5 no.1
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• pp.19-30
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• 2000

The characteristics of NOx emissions in pure hydrogen nonpremixed flames with coaxial air are analyzed numerically for the three model cases of coaxial air flames classified by varying coaxial air velocity and/or fuel velocity. In coaxial air flames, the flame length is reduced by coaxial air and can be represented as a function of the ratio of coaxial air to fuel velocity. Coaxial air decreases flame reaction zone, resulting in reducing flame residence time significantly. Finally, the large reduction of EINOx is achieved by the decrease of the flame residence time. It is found that because coaxial air can break down the flame self-similarity law, appropriate scaling parameters, which are different from those in the simple jet flames, are recommended. In coaxial air flames, the flame residence time based on the flame volume produces better results than that based on a cube of the flame length. And some portion of deviations from the 1/2 scaling law by coaxial air may be due to the violation of the linear relationship between the flame volume and the flame reaction zone.

• Journal of the Korean Geophysical Society
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• v.8 no.3
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• pp.145-152
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• 2005

216 groundwater samples for inorganic constituents and 168 samples for VOCs in the Ulsan urban ares and analyzed to relate groundwater chemistry to four land use zones, residence․commercial, industrial, agricultural, and forestry. In general, Na and Cl concentrations in groundwater were high in residence․commercial zone near Taehwa river due to residual saline. Although NO3 contents is high in agricultural zone and VOCs content is high in industrial zone, it seems difficult to relate groundwater pollution to land use zone. Even though groundwater pollution of the area is still low, continuous monitoring is necessary because the city is expanding.

• Journal of the Korean GEO-environmental Society
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• v.15 no.8
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• pp.39-44
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• 2014

Effects of operating parameters on the breakthrough properties of Pb(II) by $Mn_3O_4$ coated activated carbon prepared by supercritical technique were investigated through fixed-bed column experiments. The mass transfer zone and equilibrium adsorption capacity were enhanced about 2.8 times for Pb(II) by $Mn_3O_4$ coating onto activated carbon. Increase of bed height enhanced the residence time of Pb(II) in adsorption zone, giving the higher breakthrough time, mass transfer zone and equilibrium adsorption capacity. Increase of flow rate reduced the residence time and diffusion of Pb(II) in adsorption zone, therefore decreased the equilibrium adsorption capacity. The higher inlet concentration of Pb(II) decreased the breakthrough time and mass transfer zone through the promotion of Pb(II) transfer onto adsorbent.

• 한국연소학회:학술대회논문집
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• 2003.12a
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• pp.115-123
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• 2003

Simultaneous measurements of velocity and OH distribution were made using particle image velocimetry(PIV) and planar laser-induced fluorescence(PLIF) of OH radical in turbulent hydrogen nonpremixed flames with coaxial air. The OH radical was used as an approximate indicator of chemical reaction zone. The OH layer was correlated well with the stoichiometric velocity, $U_s$, instantaneously and on average. In addition, high strain-rate regions almost coincide with the OH distribution. The residence time in flame surface, calculated from the root-mean-square value of the radial velocity, is proportional to $(x/d_F)^{0.7}$. It is found that the mean value of principal strain rate on the OH layer can be scaled with $(x/d_F)^{-0.7}$ and therefore, the product of the residence time and the mean strain rate remains constant over all axial positions.

• 한국연소학회:학술대회논문집
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• 2014.11a
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• pp.203-205
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• 2014

This paper is suggesting about glass melting technology, using both plasma and combustion heat source. The mixed flame was formed to flow pattern of turning by plasma and combustion in melting zone. The burning time was extremely extended for vitrification of raw materials in melting zone, as a result, meting time was significantly reduced. This system was designed to smaller size than existing glass melting facilities. We had achieved to 30% energy saving, due to reduce residence time of melted materials inside furnace.

• Journal of the Korean Institute of Landscape Architecture International Edition
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• no.1
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• pp.1-12
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• 2001

The biotope network of Susung gu is characterized as dense residence zones forming its core that enable partial biotope in and around the residential zones. First, in district I, it is possible to make these zones connected to the third district. In district II, which is abundant in biotope, it is very important not to continue destoyi9ng the existing biotopes. In the case of district III, old residence zones have fill the severe gap between forests and the Sinchun river, through redevelopment, which covers more than 30% of the biotope area with large scaled linear residence areas. In the case of district IV, limited destruction of biotope and the improvement of nature areas were suggested as the alternative for preservation of biotopes. Consequently, in the construction of the biotope network in Su-sung gu, the maintenance of existing biotopes is required. Int he old residence zones, as redevelopment occurs, by maintaining biotope area of more than 30% and making the scale of residential complexes more than 1ha, it is possible for old residence zones to accomplish the role of providing important green spaces. In the case of newly developed residential zones, by reducing the rate of pavement of traffic conducts, utilizing small sized parks at the junctions and the plantation of trees along the corridors, the entire residence zones are able to accomplish the role of providing important green space. The problem houses and connecting the inner green space of the private houses with the green spaces of the streets in some areas. Futhermore, green spaces of forests must not be used for urban development. Dual planting on sidewalks, planting plots dispersed among streets and median strips must be established on road, too.