• 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.

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.2874-2879
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• 2008

The Selective catalytic reduction(SCR) system is a highly-effective device of $NO_x$ reduction for diesel engines. Generally, the ammonia($NH_3$) generated from a liquid urea-water solution is used for the reductant. The ideal ratio of $NH_3$ molecules to $NO_x$ molecules is 1:1 based on $NH_3$ consumption and having $NH_3$ available for reaction of all of the exhaust $NO_x$. However, under the too low and too high temperature condition, the $NO_x$ reduction efficiency becomes lower, due to temperature window. And space velocity also affects to $NO_x$ conversion efficiency. This paper reviews a laboratory study to evaluate the effects of $NO_x$ and $NH_3$ concentrations, gas temperature and space velocity on the $NO_x$ conversion efficiency of the SCR system. The maximum conversion efficiency of $NO_x$ was indicated when the $NH_3$ to $NO_x$ ratio was 1.2 and the space velocity was $60,000\;h^{-1}$. The results of this paper contribute to improve overall $NO_x$ reduction efficiency and $NH_3$ slip.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.1
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• pp.900-905
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• 2015

DeNOx catalysts composed of Mn, Cu and $TiO_2$ were prepared and tested for $NH_3$-SCR. The performance of each catalyst was studied for the NOx removal efficiency while changing the calcination temperature, reaction time, and oxygen concentration. The hydrogen conversion efficiency of a calcined catalyst was measured at the $H_2$-TPR system. The change in the specific surface area of catalyst according to the calcination temperature was analyzed. As a result, the proper calcination temperature was approximately $300^{\circ}C$. If the calcination temperature is increased to $500^{\circ}C$, the NOx removal efficiency of Mn and Cu constituents is largely decreased at the low temperature range. Oxygen in flue gas is an important parameter in the SCR reaction and optimal oxygen concentration is approximately 8 vol.%.

• Journal of the Korean Institute of Intelligent Systems
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• v.23 no.2
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• pp.107-112
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• 2013

In the paper, velocity controller of switching module and temperature controller for the high-voltage static var compensator are proposed. Because of the continuous increase in demand for electric power, transmission and distribution facilities of power plant are required. There is a bottleneck problem of transportation routes according to new construction and expansion of power transmission facilities. Therefore there are researches to maximize the utilization of existing facilities and to increase transmission capacity without new construction. The previous static var compensator detects voltage of input circuit of power, switches the SCR directly and generates switching noise. The proposed method increases switching velocity and decreases noise using switching control based on the voltage between both sides of SCR. Also the proposed method enhance the stability using realtime temperature control for heating of the system from increase of switching velocity. We experiment the velocity and temperature control of the proposed high-voltage static var compensator in the real environment and verify the performance of the proposed system by applying in the real field.

• Journal of Korean Society of Environmental Engineers
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• v.29 no.12
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• pp.1329-1336
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• 2007

This study was carried out to develop an efficient process abating high NO concentration. A hybrid process of selective catalytic reduction(SCR) and activated carbon fiber(ACF) adsorption was newly designed and tested. Used ACF in NO adsorption was regenerated by simultaneously applying heat and vacuum. The result of ACF regeneration was for superior in the desorption condition at $140^{\circ}C$ and vacuum 600 mmHg. A commercial catalyst was used at the conditions of reaction temperature at $300^{\circ}C$, $NH_3/NO$ mole ratio = 1.0 for SCR process. NO evolved from ACF regeneration reactor could be removed by SCR reactor up to 98%. But high concentration of NO was exhausted from SCR reactor for one minute when the flue gas of NO 300 ppm and deserted NO from ACF regeneration were simultaneously treated by the same SCR reactor. Therefore, it is necessary to use additional small sized SCR reactor or to increase $NH_3$ concentration for a short time along with NO concentration rather than to mix flue gas with the gas evolving from ACF regeneration at fixed $NH_3$ inlet concentration. The hybrid process of SCR and ACF showed high NO removal efficiency over 80% at any time courses. Through the repeated cycles, stable DeNOx efficiency was maintained, indicating that the hybrid process would be a good countermeasure to the spotaneously high NO concentration instead of increasing the SCR capacity.

• Transactions of the Korean Society of Automotive Engineers
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• v.21 no.6
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• pp.183-194
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• 2013

Liquid urea based SCR has been used in the market to reduce NOx in the exhaust emission of the diesel engine vehicle. This system has several problems at low temperature, which are freezing below $-12^{\circ}C$, solid deposit formation in the exhaust, and difficulties in dosing system at exhaust temperature below $200^{\circ}C$. Also, it is required complicated exhaust packaging equipment and mixer due to supply uniform ammonia concentration. In order to solve these issues, solid urea, ammonium carbonate, and ammonium carbamate are selected as ammonia sources for the application of solid SCR. In this paper, basic research on reaction rate of three ammonia-transporting materials was performed. TGA (Thermogravimetric Analysis) and DTA (Differential Thermal Analysis) tests for these materials are carried out for various heating conditions. From the results, chemical kinetic parameters such as activation energy and frequency factor are obtained from the Arrhenius plot. Additionally, from test results of DSC (Differential Scanning Calorimeter) for these materials, chemical kinetic parameters using the Kissinger method are calculated. Activation energies of solid SCR from this experiment are compared with proper data of literature study, then obtained data of this experiment are used for the design of reactor and dosing system for candidate vehicle.

• Clean Technology
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• v.23 no.1
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• pp.64-72
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• 2017

In this study, the selective catalytic reduction (SCR) for NOx removal was investigated in the temperature range of $150{\sim}400^{\circ}C$. XRD, BET and XPS analyses to determine the structural properties and valence state characteristics of the catalyst were performed. Various ball mill method were shown to a difference in activity at a low temperature below $250^{\circ}C$. Based on the catalyst with the highest denitrification efficiency, the ball mill time was the best result at 3 h. As a result of XPS analysis, the presence of the non-stoichiometric vanadium species and the increase of the number of atoms were attributed to a positive effect in the SCR reaction. it was confirmed that the correlation between the amount of lattice oxygen and the denitrification efficiency through the $O_2$ on-off experiment, and it was in a proportional relationship to each other.

• Applied Chemistry for Engineering
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• v.17 no.5
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• pp.490-497
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• 2006

$V_{2}O_{5}$/$TiO_{2}$ catalyst can be deactivated by ammonium salts formed by $SO_{2}$ oxidation and unreacted ammonium in presence of $SO_{2}$ in flue gas. The deactivation of catalyst by $SO_{2}$ depends on the $SO_{2}$ oxidation to $SO_{3}$. The oxidation of $SO_{2}$ is weakly affected by oxygen concentration, and strongly by the amount of vanadium loaded onto titania supports. Because unreacted ammonia is one of elements to form the ammonium salts, it is important to control the mole ratio of $NH_{3}/NOx$ in SCR. Thus the experiments about $NH_{3}/NOx$ were carried out. The reason of low activity of catalyst deactivated by ammonium salts is the change of pore volume. And TPD (Temperature Programmed Decomposition) was performed to find the decomposition of ammonium bisulfate on deactivated catalyst.

• Applied Chemistry for Engineering
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• v.27 no.2
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• pp.165-170
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• 2016

In this study, we investigated the cause of the decrease in activities of $VO_x/TiO_2$ SCR catalyst used for the burner reactor at a scale of $150000Nm^3/hr$ using X-ray diffraction (XRD), brunauer-emmett-teller (BET), atomic emission spectroscopy inductively coupled plasma (AES ICP), $H_2$ temperature programmed reduction ($H_2$-TPR), and $NH_3$ temperature programmed desorption ($NH_3$-TPD) analysis. Since the crystallization of the $VO_x$ and phase transition of $TiO_2$ did not occur, it was concluded that the catalyst was not deactivated by the thermal effect. In addition, from the elemental analysis showing that a large quantity of calcium was detected but not sulfur, the deactivation process of the $VO_x/TiO_2$ SCR catalyst was mainly caused by Ca but not by $SO_2$. The calcium was also found to decrease the catalytic activity by means of reducing $NH_3$ adsorption.

• Particle and aerosol research
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• v.8 no.4
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• pp.125-132
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• 2012

Mercury oxidation in an SCR(selective catalytic reduction) catalyst was tested in this study with the conditions simulating the SCR system in full-scale coal-fired flue gas. A commercially available SCR catalyst was located in a temperature-controlled reactor system, and simulated gas was injected into the reactor. Mercury oxidation efficiency was determined from the difference between inlet and outlet elemental mercury concentrations. A control experiment was carried out with the gas composition of 12% $CO_{2}$, 5% $H_{2}O$, 5% $O_{2}$, 500 ppm $SO_{2}$, 400 ppm NO, 400 ppm $NH_{3}$, 5 ppm HCl, and 20 ${\mu}g/m^{3}$ Hg. Additional tests were conducted with different gas composition from the control condition to investigate the effect of gas composition on mercury oxidation in the SCR catalyst.