• Clean Technology
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• v.27 no.3
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• pp.207-216
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• 2021

Major anthropogenic emissions of elemental mercury (Hg⁰) occur from coal-fired power plants, and the emissions can be controlled successfully using NH₃-SCR (selective catalytic reduction) systems with catalysts. Although the catalysts can easily convert the gaseous mercury into Hg²⁺ species, the reactions are greatly dependent on the flue gas constituents and SCR conditions. Numerous deNO_xing catalysts have been proposed for considerable reduction in power plant mercury emissions; however, there are few studies to date of elemental mercury oxidation using SCR processes with MW- and full-scale coal-fired boilers. In these flue gas streams, the chemistry of the mercury oxidation is very complicated. Coal types, deNO_xing catalytic systems, and operating conditions are critical in determining the extent of the oxidation. Of these parameters, halogen element levels in coals may become a key vehicle for obtaining better Hg⁰ oxidation efficiency. Such halogens are Cl, Br, and F and the former one is predominant in coals. The chlorine exists in the form of salts and is transformed to gaseous HCl with a trace amount of Cl₂ during the course of coal combustion. The HCl acts as a very powerful promoter for high catalytic Hg⁰ oxidation; however, this can be strongly dependent on the type of coal because of a wide variation in the chlorine contents of coal.

• Journal of the Korean Recycled Construction Resources Institute
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• v.8 no.4
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• pp.506-513
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• 2020

In this study, the mechanical properties, absorption, and reduction performance of NOx in the mortar containing mineral admixture like zeolite and active hwangtoh were evaluated. Zeolite and active hwangtoh were used as binder, and zeolite and active hwangtoh were substituted for cement. The substitution ratio of two types of mineral admixtures was considered as 20 and 30% respectively. As a result of evaluating the compressive strength and flexural strength of each mortar specimen, the highest strength in the plain mixture was evaluated. As the substitution ratio of zeolite and active hwangtoh increased, the compressive and flexural strength decreased. In addition, the difference of compressive and flexural strength between active hwangtoh and zeolite mixing was evaluated to be insignificant. To evaluate the absorption rate, the mixture was designed to lower the W/B ratio of the existing mixture and set the substitution ratio of active hwangtoh and zeolite at 25%. The highest absorption ratio in the mortar with zeolite was evaluated, and the difference in absorption ratio between the remaining two mortar mixtures was small. The assessment of reduction performance of NOx considering the application of photocatalyst showed a clearly decreasing reduction behavior, even if they were the same mortar mixture. Zeolite and active hwangtoh also showed a higher NOx reduction than the Plain mixture, because of their porosity properties. In the case of active hwangtoh, the absorption ratio was lower than that of zeolite mixture, but the reduction of NOx performance was better than the result of zeolite mixture.

• Clean Technology
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• v.27 no.1
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• pp.61-68
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• 2021

Selective catalytic reduction (SCR) is widely used as a method of removing nitrogen oxide in large-capacity thermal power generation systems. Uniform mixing of the injected ammonia and the inlet flue gas is very important to the performance of the denitrification reduction process in the catalyst bed. In the present study, a computational analysis technique was applied to the ammonia injection system design process of a denitrification facility. The applied model is the denitrification facility of an 800 MW class coal-fired power plant currently in operation. The flow field to be solved ranges from the inlet of the ammonia injection system to the end of the catalyst bed. The flow was analyzed in the two-dimensional domain assuming incompressible. The steady-state turbulent flow was solved with the commercial software named ANSYS-Fluent. The nozzle arrangement gap and injection flow rate in the ammonia injection system were chosen as the design parameters. A total of four (4) cases were simulated and compared. The root mean square of the NH3/NO molar ratio at the inlet of the catalyst layer was chosen as the optimization parameter and the design of the experiment was used as the base of the optimization algorithm. The case where the nozzle pitch and flow rate were adjusted at the same time was the best in terms of flow uniformity.

• Applied Chemistry for Engineering
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• v.32 no.1
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• pp.35-41
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• 2021

VWTi, which is used as a commercial catalyst in NH3-SCR, exhibits excellent denitrification performance at 300 to 400 ℃, but there is a problem that efficiency decreases at low temperatures below 300 ℃. Research on catalysts containing promoter to increase low-temperature denitrification efficiency is steadily progressing. However, research on the cause of the improvement in low-temperature denitrification efficiency of the catalyst and the catalyst properties is insufficient. In this study, it was confirmed that by adding Sb to VWTi, denitrification performance was improved by more than 10% in NH3-SCR reaction below 300 ℃. At this time, the space velocity and the size of the catalyst particles were controlled to exclude the influence of external/internal diffusion. In addition, the catalytic properties according to the presence or absence of Sb were investigated by performing BET, TEM/EDS, O2-TPD, H2-TPR and DRIFTs analysis. It was judged that the addition of Sb increased the adsorbed oxygen species on the surface of the catalyst, thereby enhancing the redox properties of the catalyst at low temperature and exhibiting excellent denitrification performance.

• 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.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.20 no.6
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• pp.177-191
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• 2021

One of the major causes of serious air pollution worldwide is emissions from road transportation. A number of countries are working to reduce vehicle emissions, and the Seoul Metropolitan Government is also implementing active policies to reduce emissions by setting a target of 40% by 2030. Implementing these policies requires the introduction of practical indicators. Most of the domestic emissions are calculated by the emission coefficient, a function of speed at the National Institute of Environmental Research under the Ministry of Environment, but the dynamic variable speed is limited to being used as an indicator of the number of eco-friendly vehicles. Therefore, this study calculated the emission rates in Seoul using the vehicle registration data of Seoul and the vehicle inspection data from the Korea Transportation Safety Authority. The tendency of emissions was determined according to key variables such as vehicle type, fuel and mileage. Emissions were based on carbon monoxide, hydrocarbons, nitrogen oxides and particulate matter measured by vehicle inspection from the Korea Transportation Safety Authority. As a result, the emission rates showed a significant trend according to the model year and mileage. This can be used as a policy indicator to preferentially switch commercial vehicles with old model years and long mileage when switching eco-friendly vehicles in Seoul.

• Journal of the Korean Society of Marine Environment & Safety
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• v.27 no.7
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• pp.1098-1105
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• 2021

The International Maritime Organization has steadily strengthened environmental regulations on nitrogen oxides and carbon dioxide emitted from marine vessels. Consequently, the demand for electric propulsion vessels based on eco-friendly elements has increased. To this end, research and development has been steadily conducted for various vessels. In electric propulsion systems, a redundancy configuration is typically adopted to increase reliability and facilitate the onboard arrangement. Furthermore, studies have been actively conducted to ensure the safety of electric propulsion systems through the combination with digital twin technology. A digital twin can be used to predict outcomes in advance by implementing real-world equipment or space in a virtual world like twins, integrating real-world information and data with the virtual world, and performing computer simulations of situations that can occur in a real environment. In this study, we perform failure modes and effects analysis (FMEA) to validate the electric power management system (PMS) redundancy scheme for the digital twin technology development of electric propulsion vessels. Then, we propose the role and algorithm of PMS as a compensation function for preventing primary and secondary damages caused by a single equipment failure of the PMS and preventing additional damages by analyzing the impact on the entire system under real vessel operating conditions based on the redundancy FMEA suggested for the ship classification and certification. We verified the improvement in propulsion conservation through tests.

• Journal of the Korean Institute of Gas
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• v.26 no.2
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• pp.49-55
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• 2022

According to reinforce environmental regulations, coal power plants have used selective catalytic reduction using ammonia as a reducing agent to reduce the amount of nitrogen oxide generation. The purpose of the present study was to derive a mixing device for effectively mixing dilute air and ammonia in the ammonia mixing pipe by performing computational fluid dynamic analysis. The mixing effect was compared by analysing the %RMS of ammonia concentration at the down stream cross section in the mixing pipe and the 16 outlets based on the case 1-1 shape, which is an existing mixing pipe without a mixing device. The mixing device was performed by changing the positions of a square plate on the downstream side of the ammonia supply pipe and an arc-shaped plate on the wall of the mixing pipe. In the case of the existing geometry(Case 1-1), the %RMS of ammonia concentration at the 16 outlets was 29.50%. The shape of the mixing device for Case 3-2 had a square plate on the downstream side of the ammonia supply pipe and an arc plate was installed adjacent to it. The %RMS of ammonia concentration for Case 3-2 was 2.08% at 16 outlets and it could be seen that the shape of Case 3-2 was the most effective mixing shape for ammonia mixing.

• Applied Chemistry for Engineering
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• v.34 no.4
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• pp.357-364
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• 2023

Selective catalytic reduction (SCR) is the most effective method for reducing nitrogen oxide emissions, but the operating temperature range of V₂O₅-WO₃/TiO₂ catalysts is narrow (300~400℃). In this study, a new catalyst with an operating temperature range of 200~450℃ was developed. The catalyst poison, ammonium bisulfate, generated during the SCR process can be removed by heating above 350℃. To increase the number of active sites and promote the dispersion of active materials, titanium isopropoxide (TTIP) treatment was performed on the TiO₂ support with various TTIP/TiO₂ mass ratios. Among them, the 5 wt% TTIP loaded catalyst showed improved performance due to higher thermal stability caused by high W dispersion and the formation of V⁵⁺. In addition, the 5 wt% TTIP-loaded catalyst prepared by a one-step co-precipitation method showed greater V-OH and W-OH dispersion and enhanced interactions in contrast to conventional methods, resulting in higher catalytic activity at lower temperatures. This review article aims to provide an accessible explanation for researchers investigating how to improve the surface properties of TiO2 catalysts using TTIP.

• Clean Technology
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• v.16 no.4
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• pp.284-291
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• 2010

Nitrous oxide ($N_2O$) is a greenhouse material which is hard to remove. Even with a catalytic process it requires a reaction temperature, at least, higher than 670 K. This study has been performed to see the effects of Ce addition to the mixed oxide catalyst which shows the highest activity in decomposing $N_2O$ completely at temperature as low as 473 K when CO is used as a reducing agent. Mixed metal oxide(MMO) catalyst was made through co-precipitation process with small amount of Ce added to the base components of Co, Al and Rh or Pd. Consequently, the surface area of the catalyst decreased with the contents of Ce, and the catalytic activity of direct decomposition of $N_2O$ also decreased. However, in the presence of CO, the activity was found high enough to compensate the portion of activity decrease by Ce addition, so that it can be ascertained that the catalytic activity and stability can be maintained in the CO involved $N_2O$ reduction system when Ce is added for the physical stability of the catalyst.