• The Transactions of the Korean Institute of Electrical Engineers C
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• v.49 no.1
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• pp.37-43
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• 2000

In this experimental study we proposed the double dielectric barrier discharge (DDBD) reactor to produce as high an electric field as possible. The experiment are conducted for applied voltage from 15 to 20[kV], $1~4[\ell/min]$ of gas flow rate and 120[Hz] and 240[Hz] of pulse rate. Superposition discharge(SPD) generated in DDBD which combined the surface discharge with the silence discharge was the most effective to reduce the $NO_x$. In the decomposition efficiency per watt, the low pulse rate gave better efficiency than the high pulse rate. However in DeNOx rate, the high pulse rate gave better performance than the low pulse rate. $NO_x$ removal rate and efficiency increased with increasing the applied voltage in all reactors.

• Journal of ILASS-Korea
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• v.20 no.1
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• pp.20-27
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• 2015

Urea-SCR which is one of the aftertreatment technologies for reducing the NOx emission is widely used. An experimental study was performed to investigate urea decomposition under various thermo-fluid conditions, with different temperatures and velocities of inflow gas, and urea solution quantities. 40 wt. % aqueous urea solutions were used in this study. The inflow gas conditions were similar to the exhaust conditions of a large marine engine. The spray performance of urea solution injector was identical under all experimental conditions. The conversion efficiency of $NH_3$ was larger than that of HNCO under all experimental conditions, unlike for the theoretical thermolysis reaction.

• Journal of the Korean Society of Marine Environment & Safety
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• v.27 no.1
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• pp.153-160
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• 2021

Nitrous oxide is a global warming substance and is known as the main cause of the destruction of the ozone layer because its global warming effect is 310 times stronger than carbon dioxide, and it takes 120 years to decompose. Therefore, in this study, we investigated the characteristics of NOx emission from N2O reduction by thermal decomposition of N2O. Bunsen premixed flames were adopted as a heat source to form a high-temperature flow field, and the experimental variables were nozzle exit velocity, co-axial velocity, and N2O dilution rate. NO production rates increased with increasing N2O dilution rates, regardless of nozzle exit velocities and co-axial flow rates. For N2O, large quantities were emitted from a stable premixed flame with suppressed combustion instability (Kelvin Helmholtz instability) because the thermal decomposition time is not sufficient with the relatively short residence time of N2O near the flame surface. Thus, to improve the reduction efficiency of N2O, it is considered effective to increase the residence time of N2O by selecting the nozzle exit velocities, where K-H instability is generated and formed a flow structure of toroidal vortex near the flame surface.

• Applied Chemistry for Engineering
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• v.26 no.6
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• pp.686-691
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• 2015

A basic research for utilizing solid refuse fuel (SRF) based on changing SRF properties (RDF, RPF) and types (pellet, fluff) is demonstrated. Physicochemical characteristics of SRF and also changes in thermal decomposition depending on combustion time and emission gas (NOx, CO, HCl, etc) concentration were investigated for applications to waste energy sources. In conclusion, RPF is easy to pelletize, and has better combustion efficiency, higher LHV, higher thermal reduction, and short combustion time because it is composed of plastic wastes homogeneously. Also, fluff type samples have better combustion efficiency, and short combustion time because it has wider exposed surface area for combustion. It can also save energy consumption for pelletizing.

• Transactions of the Korean Society of Automotive Engineers
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• v.14 no.1
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• pp.68-78
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• 2006

In the past few years, considerable efforts have been directed towards the further development of Urea-SCR(selective catalytic reduction) technique for diesel-driven vehicle. Although urea possesses considerable advantages over Ammonia$(NH_3)$ in terms of toxicity and handling, its necessary decomposition into Ammonia and carbon dioxide complicates the DeNOx process. Moreover, a mobile SCR system has only a short distance between engine exhaust and the catalyst entrance. Hence, this leads to not enough residence times of urea, and therefore evaporation and thermolysis cannot be completed at the catalyst entrance. This may cause high secondary emissions of Ammonia and isocyanic acid from the reducing agent and also leads to the fact that a considerable section of the catalyst may be misused for the purely thermal steps of water evaporation and thermolysis of urea. Hence the key factor to implementation of SCR technology on automobile is fast thermolysis, good mixing of Ammonia and gas, and reducing Ammonia slip. In this context, this study performs three-dimensional numerical simulation of urea injection of heavy-duty diesel engine under various injection pressure, injector locations and number of injector hole. This study employs Eulerian-Lagrangian approach to consider break-up, evaporation and heat and mass-transfer between droplet and exhaust gas with considering thermolysis and the turbulence dispersion effect of droplet. The SCR-monolith brick has been treated as porous medium. The effect of location and number of hole of urea injector on the uniformity of Ammonia concentration distribution and the amount of water at the entrance of SCR-monolith has been examined in detail under various injection pressures. The present results show useful guidelines for the optimum design of urea injector for reducing Ammonia slip and improving DeNOx performance.

• Journal of the Korean Chemical Society
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• v.30 no.2
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• pp.207-215
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• 1986

A new method was proposed to improve removal of nitrogen oxides $(NO_x)$ in exhaust gas by the reduction method using ammonia. At the relative humidity of 60%, 50 ppm of $NO_x$ was decomposed at the rate of 1% per hour in the reaction chamber. On the other hand, by adding $NH_3$ which was 5 times more concentrated than NOx, the decomposition rate increased to 6% per hour for 50 ppm $NO_x$ and 10% per hour for 20ppm $NO_x$. Within the actual exhausted gases, the decomposition rate of $NO_x$ reached the maximum 15% per hour because of coexisted reducing gases, such as hydrocarbon and carbon monoxide, and excess humidity containing trace metal ions. In the presence of acidic $SO_2$ gas, the decomposition rate of $NO_x$ decreased. The decomposition of $NO_x$ seems to be caused by the mist which is added to the system, and $NH_3$ in the mist which reduces $NO_x$.

• Transactions of the Korean Society of Automotive Engineers
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• v.23 no.2
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• pp.199-207
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• 2015

Solid materials of ammonia sources with SCR have been considered for the application of lean NOx reduction in automobile industry, to overcome complex problems of liquid urea based SCR. These solid materials produce ammonia gas directly with proper heating and can be packaged by compact size, because of high volumetric ammonia density. Among ammonium salts and metal ammine chlorides, calcium ammine chloride was focused on this paper due to low decomposition temperature. In order to make calcium ammine chloride in lab-scale, simple reactor and glove box was designed and built with ammonium gas tank, regulator, and sensors. Basic test conditions of charging ammonia gas to anhydrous calcium chloride are chosen from equilibrium vapor pressure by Van't Hoff plot based on thermodynamic properties of materials. Synthetic method of calcium ammine chloride were studied for different durations, temperatures, and pressures with proper ammonia gas charged, as a respect of ammonia gas adsorption rate(%) from simple weight calculations which were confirmed by IC. Also, lab-made calcium ammine chloride were analyzed by TGA and DSC to clarify decomposition step in the equations of chemical reaction. To understand material characteristics for lab-made calcium ammine chloride, DA, XRD and FT-IR analysis were performed with published data of literature. From analytical results, water content in lab-made calcium ammine chloride can be discovered and new test procedures of water removal were proposed.

• Journal of the Korean Society of Marine Environment & Safety
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• v.26 no.6
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• pp.751-758
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• 2020

SCR technology, which uses urea-water as a NO_x reducing agent, has been widely used to reduce NO_x in marine diesel engines. However, as an alternative NO_x reducing agent, solid-phase ammonium carbamate has several advantages, such as low-temperature NO_x reduction performance and NH₃ storage capacity. This study presents a method for evaluating the purity of ammonium carbamate using EA, FTIR, and XRD to investigate the change in the material characteristics of ammonium carbamate when it is exposed to various temperature and pressure conditions. In this study, it was found that the purity of ammonium carbamate can be effectively evaluated via EA analysis. The FTIR analysis results confirmed that the properties of ammonium carbamate did not change even after repeated heating and cooling under thermal decomposition temperature conditions, which may be applied to the SCR system of marine diesel engines. Additionally, it was found that when ammonium carbamate was exposed to the atmosphere for a long time, it transformed into ammonium carbonate.

• Journal of Power System Engineering
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• v.19 no.3
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• pp.22-28
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• 2015

A compression ignition type of diesel engine makes fuel efficiency better and $CO_2$ in the exhaust gas lower. Also it is suitable to apply alternative fuels(blended fuel) to the engine. The objective of this study is the emissions reduction of diesel engine with EF(Emulsified fuel). The emulsified fuel consists of diesel and peroxide($H_2O_2$) and Soot reduction without worsening of NOx emissions can be achieved by using thermal decomposition of the peroxide, i.e. the chemical effect of the OH radical in actual engine. For manufacturing emulsified fuel, a surfactant which is comprised of span 80 and tween 80 mixed as 9:1, was mixed with a fixed with 3% of the total volume in the emulsion fuel. In addition, considering the mixing ratio of the surfactant, the mixing ratio of $H_2O_2$ in the emulsified fuel was set as EF0, EF2, EF12, EF22, EF32, and EF42, respectively. Consequently, this study aims to obtain the optimization of fuel design(mixing) for the emulsified fuel applying to the diesel engine.

• Transactions of the Korean Society of Automotive Engineers
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• v.20 no.6
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• pp.73-82
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• 2012

The main and side reactions of the three selective catalytic reduction (SCR) reactions with ammonia over a vanadium-based catalyst have been investigated using synthetic gas mixtures in the temperature range of $170{\sim}590^{\circ}C$. The three SCR reactions are standard SCR with pure NO, fast SCR with an equimolar mixture of NO and $NO_2$, and $NO_2$ SCR with pure $NO_2$. Vanadium based catalyst has no significant activity in NO oxidation to $NO_2$, while it has high activity for $NO_2$ decomposition at high temperatures. The selective catalytic oxidation of ammonia and the formation of nitrous oxide compete with the SCR reactions at the high temperatures. Water strongly inhibits the selective catalytic oxidation of ammonia and the formation of nitrous oxide, thus increasing the selectivity of the SCR reactions. However, the presence of water inhibits the SCR activity, most pronounced at low temperatures. In this study, the experimental results are analyzed by means of a dynamic one-dimensional isothermal heterogeneous plug-flow reactor (PFR) model according to the Eley-Rideal mechanism.