• Transactions of the Korean Society of Automotive Engineers
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• v.18 no.6
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• pp.76-83
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• 2010

Recently, as the current and future emission regulations go stringent, the research of NOx reduction has become a subject of increasing interest and attention in diesel engine. Selective Catalytic Reduction (SCR) is one of the effective technology to reduce NOx emission from diesel engine. Especially, Urea-SCR that uses urea as a reductant is becoming increasingly popular as a cost effective way of reducing NOx emissions from heavy duty vehicles. In this research, we designed urea injector and DCU (Dosing Control Unit) specially developed for controlling the Urea-SCR process onboard vehicles. As passenger and commercial diesel engine experiment, we grasped characteristics of NOx emission and SCR catalyst temperature level in advance. As a result, highest NOx emission level was shown in condition of low engine speed and high load. On the other hand, SCR catalyst temperature was highest at high engine speed and load. On the basis of these result, we conducted the NOx reduction test at steady engine operating conditions using the urea injector and DCU. It was shown that 74% NOx conversion efficiency on the average and 97% NOx conversion efficiency was obtained at high SCR catalyst temperature.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.12
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• pp.6575-6580
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• 2013

Various modified SCR catalysts were prepared and tested to improve the strength of catalysts for use under severe conditions. The SCR catalysts were modified with a binder and dispersion agent, and tested at the fixed bed reactor. FT-IR and $H_2$-TPR were used to analyze the degree of hydrogen use and ammonia adsorption by the modified catalysts. In the case of the SCR catalysts coated with 2.3g of the binder, 4.7g of ethanol, and 0.1g of dispersion agent, the strength of catalyst was increased by approximately 12%. On the other hand, despite the enhancement of strength, the activities of the SCR catalysts were decreased by 2-10%. When the mixed solution composed of binder, dispersion agent and $SiO_2$ solution was precipitated on the catalyst, the $NO_x$ conversion of the catalyst was decreased slightly. The Bronsted acid site and Lewis acid site worked as the activators for the SCR reaction, and were decreased by $SiO_2$.

• Journal of IKEEE
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• v.18 no.1
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• pp.25-30
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• 2014

In this paper, SCR(Silicon Controlled Rectifier)-based ESD(Electrostatic Discharge) protection circuit for power clamp is proposed. In order to improve latch-up immunity caused by low holding voltage of the conventional SCR, it is modified by inserting n+ floating region and n-well, and extending p+ cathode region in the p-well. The resulting ESD capability of our proposed ESD protection circuit reveals a high latch-up immunity due to the high holding voltage. It is verified that electrical characteristics of proposed ESD protection circuit by Synopsys TCAD simulation tool. According to the simulation results, the holding voltage is increased from 4.61 V to 8.75 V while trigger voltage is increased form 27.3 V to 32.71 V, respectively. Compared with the conventional SCR, the proposed ESD protection circuit has the high holding voltage with the same triggering voltage characteristic.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.28 no.1
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• pp.35-41
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• 2016

With the assumption that the performance of a catalyst is guaranteed and that the performance of an SCR reactor is influenced by the uniformity of fluid flow into the catalyst, this study carried out a numerical analysis of flow uniformity, which is an important design factor in SCR reactors. CFD was used to grasp flow uniformity and flow characteristics inside the SCR reactor. As for the flow uniformity, analysis was carried out on the velocity and direction of the fluid flowing into the front of the first SCR reactor. Numerical analysis was carried out in terms of the area ratios of the mixing evaporator to the catalyst for 500 PS SCR, 1 : 1.9, 1 : 3.1, 1 : 4.5, and 1 : 7.0. The results showed that the larger the area ratio, the smaller the flow uniformity. On the basis of these results, the flow uniformity of the modified SCR reactor is 77%. A guidevane was installed to improve flow uniformity, and attempts were made to grasp the flow uniformity based on the shape of the guide vane. The shape of the guide vane was cylindrical, and numerical analysis was carried out for cases with two cylinders and three cylinders. As a result of the numerical analysis, it was found that while there was no great difference between 82.7% with two cylinders and 81.7% with three cylinders, the effects of the installation of the guide vane on the improvement of flow uniformity were indisputable.

• Preventive Nutrition and Food Science
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• v.7 no.4
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• pp.397-404
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• 2002

Soybean curd residue (SCR) was fermented by lactic acid bacteria, Lactobacillus rhamnosus LS and Entercoccus faecium LL, isolated from SCR. The pH, titratable acidify and viable cell counts were determined from the fermented SCR to evaluate the lactic acid production and growth of lactic acid bacteria. Optimal amounts of pretense enzyme and glucose, and ideal fermentation time for SCR fermentation were estimated by response surface methodology (RSM). Raw SCR fermented by indigenous microorganisms had 0.78 % titratable acidity, The acid production in SCR fermented by L. rhamnosus LS was greatly enhanced by the addition of glucose and lactose. However only glucose increased acid production by Ent. faecium LL. The proof test of SCR fermentation demonstrated that similar results for titratable acidity, tyrosine content and viable cell counts to that predicted could be obtained by the at optimized fermentation conditions. In the presence of 0.029 % (w/w) pretense enzyme and 0.9% (w/w) glucose, the SCR fermented by Ent. faecium LL showed 1.07% (w/v) of titratable acidity, 1.02 mg% tyrosine content and 2$\times$10$^{9}$ (cfu/g) of viable cell counts. With the SCR fortified with 0.033% pretense enzyme and 1.7% glucose, L. rhamnosus LS showed 1.8% (w/v) of titratable acidity, 0.92 mg% of tyrosine content and 2$\times$10$^{9}$ (cfu/g) of viable cell counts.

• Applied Chemistry for Engineering
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• v.28 no.2
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• pp.158-164
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• 2017

In this study, the reaction activity and XRD, BET, and Raman analysis were performed to verify $NH_3$-SCR reaction characteristics of various commercial SCR catalysts. It can be seen that the reaction rate of each commercial SCR catalyst increased linearly with increasing the vanadium content (1.3-5.4 wt%). In addition, through the above analysis, it was possible to confirm that the addition of WOx in the catalyst increased the Turn over frequency (TOF) within the range where the VOx surface density was more than 8.1 and the crystalloid VOx was not formed through the surface structure analysis. $SO_2$ durability tended to decrease with increasing the vanadium content, and the durability increased the most when W and Si were added.

• Applied Chemistry for Engineering
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• v.23 no.1
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• pp.119-123
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• 2012

This study presents the effect of oxygen on the $NH_3$ selective catalytic reduction (SCR) by Mn/$TiO_2$ catalyst. The lattice oxygen of catalysts is participate in the low temperature SCR, and the gaseous oxygen directly takes part in the rexoidtion of reduced catalyst. These redox properties of oxygen an play important role in SCR activity and the available capability of lattice oxygen depends on the manganese oxidation state of the catalyst surface. $MnO_2$ species has a higher redox property than that of $Mn_2O_3$ species on deposited $TiO_2$ surface and these manganese oxide states strongly depend on the $TiO_2$ surface area.

• Transactions of the Korean Society of Automotive Engineers
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• v.17 no.1
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• pp.154-161
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• 2009

This study is a part of project of urea-SCR system development for an in-use medium duty diesel engine. This study shows the effect of ammonia oxidation catalyst and SCR volume on $NO_X$ reduction performance. When AOC(Ammonia Oxidation Catalyst) is not used, the urea injection should be controlled accurately to prevent $NH_3$ slip. However, it is found that the accurate $NH_3$ slip control is not easy without AOC in real engine operating conditions, because $NH_3$ and $NO_X$ reaction characteristics change with many factors such as exhaust gas temperature and $NH_3$ absorbance on SCR. SCR volume is also one of important design parameters. This study shows that $NO_X$ reduction efficiency increases with increase of SCR volume especially at high space velocity and low exhaust gas temperature conditions. Additionally, this paper shows the emissions of EURO-2 medium duty diesel engine can be improved to the level of EURO-5 with a DPF and urea-SCR system.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.40 no.7
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• pp.429-434
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• 2016

Among various De-NOx technologies, Urea-based Selective Catalytic Reduction (SCR) systems are known to be the most effective in marine diesel applications. The spraying and mixing behavior of the urea-water solution has a decisive effect on the system's net efficiency. Therefore, in this study, the spray behavior and ammonia uniformity with and without a static mixer were analyzed by CFD in order to optimize the SCR system. The results showed that the static mixer significantly affected the uniformity of velocity and ammonia concentration. Static mixers may be especially suited for marine SCR systems with space constraints.

• Journal of IKEEE
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• v.17 no.2
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• pp.208-213
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• 2013

In this paper, we proposed the novel SCR-based ESD protection circuit with high holding voltage for power clamp. In order to increase the holding voltage, the floating p+ and n+ to n-well and p-well, respectively, in the conventional SCR. The resulting increase of the holding voltage of the our proposed ESD circuit enables the high latch-up immunity. The electrical characteristics including ESD robustness of the proposed ESD circuit have been simulated using Synopsys TCAD simulator. According to the simulation result, the proposed device has higher holding voltage of 4.98 V than that of the conventional SCR protection circuit. Moreover, it is confirmed that the device could have the holding voltage of maximum 13.26 V with the size variation of floated diffusion area.