• Journal of the Korean Society of Marine Environment & Safety
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• v.27 no.2
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• pp.355-362
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• 2021

To facilitate low-pressure selective catalyst reduction (L.P SCR), a high exhaust-gas temperature of a four-stroke diesel engine for a ship's generator is required. This study aimed at reducing the exhaust-gas temperature by adjusting the valve open-close timing and fuel injection timing to satisfy the operating conditions of L.P SCR and prevent accidents associated with the generator engine due to high temperature. To lower exhaust-gas temperature, the angle of the camshaft was adjusted and the shim of the fuel injection pump was added. As a result, the maximum explosion pressure increased and the average of the turbocharger outlet temperature dropped. Considering the heat loss from the turbocharger outlet to the SCR inlet, the operation condition for L.P SCR was satisfied with 290 ℃. The study demonstrates that safe operation of a diesel generator can be achieved by lowering the exhaust-gas temperature.

• Proceedings of the KIEE Conference
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• summer
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• pp.1199-1201
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• 2004

When The temperature of the joining of SCR rises major changes of characteristics are increase of leakage current, decrease of break-down voltage, and increase of turn off time. Because these changes promote the inferiority of SCR it(SCR) will get out of control and its life time will be shortened and finally it will be destroyed. In this paper, we will measure the changes of the characteristics in accordance with a rise in temperature. On the basis of the result we will find out the appropriate time to change SCR and we will use the result for the maintenance of SCR and increase of reliability of SCR.

• Journal of the Korean Society of Visualization
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• v.19 no.1
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• pp.62-67
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• 2021

Selective catalytic reduction(SCR) is an exhaust gas reduction device to remove nitro oxides (NOx). SCR operation of ship can be controlled through valves for minimizing economic loss from SCR. Valve in SCR-high pressure (HP) system is directly connected to engine exhaust and operates in high temperature and high pressure. Long-term thermal deformation induced by engine heat weakens the sealing of the valve, which can lead to unexpected failures during ship sailing. In order to prevent the unexpected failures due to long-term valve thermal deformation, a failure prediction system using autoregressive integrated moving average (ARIMA) was proposed. Based on the heating experiment, virtual data mimicking temperature range around the SCR-HP valve were produced. By detecting abnormal temperature rise and fall based on the short-term ARIMA prediction, an algorithm determines whether present temperature data is required for failure prediction. The signal processed by the data collection algorithm was interpolated for the failure prediction. By comparing mean average error (MAE) and root mean square error (RMSE), ARIMA model and suitable prediction instant were determined.

• Applied Chemistry for Engineering
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• v.22 no.6
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• pp.658-663
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• 2011

The SNCR-SCR (selective non-catalytic reduction-selective catalytic reduction) hybrid system is an economical NOx removal system. In this study, the effect of the operating parameters of the SNCR-SCR hybrid system on NOx removal efficiency was investigated. When the SNCR reactor was operated at a temperature lower than the optimum temperature ($900{\sim}950^{\circ}C$), an additional NO removal is obtained basesd on the utilization of $NH_3$ slip. On the other hand, the SNCR reactor operated above the temperature resulted in no additional NO removal of SCR due to decomposition of $NH_3$. Therefore, the SNCR process should be operated at optimum temperature to obtain high NO removal efficiency and low $NH_3$ slip. Thus, it is important to adjust NSR (normalized stoichiometric ratio) so that $SR_{RES}$ can be maintained at an appropriate level.

• Journal of Power System Engineering
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• v.19 no.4
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• pp.30-35
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• 2015

The purpose of this study is to identify the low temperature performance and strength characteristics of V-based extruded homogeneous SCR. The extruded catalyst and the coated catalyst showed 50% and 27% of NOx conversion performance respectively at about $210^{\circ}C$ of catalyst temperature, so the extruded SCR was higher in de-NOx performance than the coated SCR especially at a low temperature zone. The compressive strength of the Enhanced Extrusion #1, in which the content of promoters such as silica, clay, glass fiber and binder was optimized, was a 120% improvement compared to the Extrusion#1 catalyst, higher than the coated SCR.

• Journal of Environmental Science International
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• v.12 no.1
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• pp.47-54
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• 2003

This paper have examined the optimum combination of SNCR and SCR by varying SNCR injection temperature and NSR ratio along with SCR space velocity. NOx reduction experiments using a SNCR/SCR combined process have been conducted in simple NO/NH$_3$/O$_2$ gas mixtures. Total gas flow rate was kept constant 4 liter/min throughout the SNCR and SCR reactors, where initial NOx concentration was 500 ppm in the presence of 5% O$_2$. Commercial catalyst, sulfated V$_2$O$\_$5/-WO$_3$/TiO$_2$, was used for SCR NOx reduction. The residence time and space velocity were around 1.67 sec, 2,400 h$\^$-1/ and 6,000 h$\^$-1/ in the SNCR and SCR reactors, respectively. SNCR NOx reduction effectively occurred in a temperature window of 900-950$^{\circ}C$. About 88% NOx reduction was achieved with an optimum temperature of 950$^{\circ}C$ and NSR=1.5. SCR NOx reduction using commercial V$_2$O$\_$5/-WO$_3$-SO$_4$/TiO$_2$ catalyst occurred in a temperature window of 200-450$^{\circ}C$ 80-98% NOxreduction was possible with SV=2400 h$\^$-1/ and a molar ratio of 1.0-2.0. A SNCR/SCR(SV=6000 h$\^$-1/) combined process has shown same NOx reduction compared with a stand-alone SCR(SV=2400 h$\^$-1/) unit process of 98% NOx reduction. The NH$_3$-based chemical could routinely achieve SNCR/SCR combined process total NOx reductions of 98% with less than 5 ppm NH$_3$ slip at NSR ranging from about 1.5 to 2.0, SNCR temperature of 900$^{\circ}C$-950$^{\circ}C$, and SCR space velocity of 6000 h$\^$-1/. Particularly, more than 98% NOx reduction was possible using the combined process under the conditions of T$\_$SNCR/=950$^{\circ}C$, T$\_$SCR/=350$^{\circ}C$, 5% O$_2$, SV=6000 h$\^$-1/ and NH$_3$/NOx=1.5. A catalyst volume was about three times reduced by SNCR/SCR combined process compared with SCR process under the same controlled conditions.

• Journal of Energy Engineering
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• v.29 no.2
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• pp.10-22
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• 2020

As the national demand for solving the fine dust problem has increased, the government has announced intensive measures to deal with fine dust. So recently, selective catalytic reduction(SCR) has attracted attention as a technology for removing nitrogen oxides from precursors of fine dust. In this study, the government's policies related to fine dust and the current status of market and R&D were investigated, and economic analysis by scenarios was conducted by dividing cases where SCR technology was applied to industries. The results of economic analysis for each scenario were calculated using NPV, and companies with no denitrification facilities(Case 1) introduced general SCR technologies(Scenario 1-1) and low-temperature SCR technologies(Scenario 1-2). In addition, companies that have already installed denitrification facilities(Case 2) analyzed the two categories, using the general SCR technology as it is(Scenario 2-1) and replacing it with low-temperature SCR technology(Scenario 2-2). Comparative analysis was performed based on the results of each NPV.

• Applied Chemistry for Engineering
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• v.17 no.4
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• pp.409-413
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• 2006

An experimental study on a combined $De-NO_x$ process of non-thermal plasma and $NH_{3}$ SCR, which can be operated under low temperature conditions, i.e. $150{\sim}200^{\circ}C$, has been conducted. The test results confirmed feasibility of fast SCR reaction, which shows faster reactivity compared with typical SCR reaction under the low temperature conditions. The test showed that pre-oxidation step to convert NO to $NO_2$ is necessary for the fast SCR reaction, and the appropriate ratio of $NO_{2}/NO_{x}$ ranges from 0.3 to 0.5. Ammonium salts produced under low temperature conditions, effects of hydrocarbons on the combined process, the operation power of the process are discussed in the present study.

• Clean Technology
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• v.26 no.4
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• pp.321-328
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• 2020

This experiment compared V/W/TiO2 and V/Mo/TiO2 catalysts that were used for commercial catalysts. The effects of SCR reactions on low-temperature activity were studied. NH3-TPD, DRIFT, and H2-TPR analysis, alongside O2-on/off experiments, were conducted to identify the effects of NH3 acid sites and oxygen participating in the SCR reaction, which had a significant impact on the NH3-SCR reaction. The effect on activity was analyzed at 250 ℃, a high temperature of reaction activity, and 180 ℃, which showed significant activity degradation. In NH3 involved in the SCR reaction at 250 ℃, B and L acid sites contributed to the reaction. In particular, the B acid site was found to have significantly participated in the reaction and affected the NH3-SCR activity, which was reduced at 180 ℃ to affect the activity degradation. Also, atmospheric oxygen contributed to the SCR reaction, causing the active property to facilitate reaction activity at 250 ℃. However, oxygen did not comprise the reaction at 180 ℃, indicating a drop inactivity. Therefore, the B acid site was reduced, and the activity was judged to be degraded due to failure to share in the reaction and low effects by atmospheric oxygen.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.32 no.11
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• pp.897-905
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• 2008

Selective catalytic reduction(SCR) is known as one of promising methods for reducing $NO_x$ emissions in diesel exhaust gases. $NO_x$ emissions react with ammonia in the catalyst surface of SCR system at working temperature of catalyst. In this study, to raise the reacting temperature when the exhaust gas temperature is too low, a heater is located at the bottom of SCR reactor. At an ambient temperature, ammonia is radially injected perpendicular to the exhaust gas flow at inlet pipe and uniformly mixed in the mixing area after being impinged against the wall. To predict the turbulent model inside the mixing area of SCR system, the standard ${\kappa}\;-\;{\varepsilon}$ model is applied. This work investigates numerically the effects of induced heat on the gaseous flow. The results show that the Taylor-$G{\ddot{o}}rtler$ type vortex is generated after the gaseous flow impinges the wall in which these vortices influence the temperature distribution. The addition of heat disturbs the flow structure in bottom area and then stretching flow occurs. Vorticity strand is also formed when heat is continuously increased. Constriction process takes place, however, when a further heat input over a critical temperature is increased and finally forms shed vortex which is disconnected from the vorticity strand. The strong vortex restricts the heat transport in the gaseous flow.