• Resources Recycling
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• v.33 no.3
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• pp.30-37
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• 2024

In this study, we investigated the separability of vanadium and tungsten from spent SCR (Selective Catalytic Reduction) catalyst leach solution by reduction of vanadium and solvent extraction using Alamine 336 and conducted experiments to optimize process conditions. It is difficult to separate vanadium and tungsten due to their similar chemical behavior, but tungsten can be selectively extracted from acidic solution when vanadium extraction is prevented by reducing anionic pentavalent vanadium to cationic tetravalent vanadium. The results showed that NaHSO₃ was most suitable as a reducing agent, and the extraction efficiency of vanadium decreased and the separation efficiency increased as the amount of reducing agent added, reaction time, and temperature increased. When reducing NaHSO₃ 1.5 eq, 60 min, and 60℃, which are optimal conditions of reduction, vanadium and tungsten were effectively separated with vanadium extraction efficiency of 5.8%, tungsten extraction efficiency of 99%, and separation factor of vanadium and tungsten of 7,564.

• Korean Journal of Materials Research
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• v.12 no.2
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• pp.129-134
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• 2002

The optimum condition for fabricating cordierite disc type filter element was deduced. Cordierite monolith was used as starting material for filter element because it has many advantages such as high thermal shock resistance and good catalytic activity compared with $TiO_2$and SiC. The contents of organic additives and foaming agent were optimized to control the porosity and mechanical strength of cordierite filter. Among the required properties to be adopted as filter elements, the pressure drop and NOx removal efficiency were investigated depending on processing variables. It was found that pressure drop depends on particle size distribution of cordierite monolith and organic additives added as forming agent. The pressure drop at 5cm/sec of face velocity was in the range of 15~655mm$H_2O$ at room temperature. The NOx removal efficiency of catalytic filter with $V_2O_5$ as catalyst was over 85% at $450^{\circ}C$.

• Clean Technology
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• v.24 no.4
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• pp.307-314
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• 2018

In this study, NMO (Natural Manganese Ore), $MnO_2$, and $Mn_2O_3$ catalysts were used in the selective catalytic reduction process to remove nitrogen oxides (NOx) using $NH_3$ as a reducing agent at low temperatures in the presence of oxygen. In the case of the NMO (Natural Manganese Ore), it was confirmed that the conversion of nitrogen oxides in the stability test did not change even after 100 hours at 423 K. The Kinetics experiments were carried out within the range where heat and mass transfer were not factors. From a steady-state Kinetics study, it was found that the low-temperature SCR reaction was zero order with the respect to $NH_3$ and 0.41 ~ 0.57 order with the respect to NO and 0.13 ~ 0.26 order with the respect to $O_2$. As temperature increases, the reaction order decreases as a result of $NH_3$ and oxygen concentration. It was confirmed that the reaction between the $NH_3$ dissociated and adsorbedon the catalyst surface and the gaseous nitrogen monoxide (E-R model) and the reaction with the adsorbed nitrogen monoxide (L-H model) occur.

• Journal of the Korean Applied Science and Technology
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• v.36 no.2
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• pp.668-675
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• 2019

Fine dust in air pollutants is recognized as one of the most serious social environmental problems. Most of the NOx is generated in a combustion process such as that of a coal-fired power plant, and therefore efficient elimination of the NOx from the coal-fired power plants is needed. This study investigates the removal efficiency of using $TiO_2$, a photocatalyst, to remove NOx by Selective Catalytic Reduction (SCR). To evaluate the NOx removal efficiency, $TiO_2$ catalyst and phosphate binder were mixed on the surface of the $Al_2O_3$ substrate with the exothermic agent, and the substrate was heat-treated. The NOx removal efficiency of the catalysts was evaluated according to the temperature, and XRD, SEM, TG-DTA and BET analyzes were performed to investigate the physicochemical properties of the catalysts. NOx removal efficiency was 58.7%~65.9% at 20min, 63.7~66.0% at 30min with temperature change according to time($250^{\circ}C{\sim}500^{\circ}C$). The $TiO_2$ used in the SCR for NOx removal is judged to have the most efficient removal efficiency at $300^{\circ}C$.

• Transactions of the Korean Society of Automotive Engineers
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• v.20 no.4
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• pp.150-155
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• 2012

Lean NOx Trap (LNT) catalysts are capable of reducing exhaust NOx emissions from diesel engines. LNT stores NOx in lean condition and exhausts N2 by reducing NOx in rich condition. NOx reduction characteristic of LNT catalysts using throttle position sensor and fuel injection timing control for light-duty diesel engine was investigated. In contrast to SCR system, LNT catalyst uses diesel fuel in resuctant. Also if the concentration of reductant is exceeded, excessive amount of reductant will slip throughout LNT and cause another emission problem. Thus LNT regeneration with precise engine control established that can make higher NOx conversion efficiency and lower fuel penalty, prevent another emission problem. NOx and reductant concentration were measured by the NOx sensor and Mexa7100D equipped inlet and outlet of catalyst. As a result of engine test, regeneration strategy has reached high of 77.8% NOx conversion efficiency according to engine operation condition. Moreover, we have proved that it is possible to use regeneration strategy of LNT within 5% fuel penalty.

• Journal of Environmental Health Sciences
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• v.31 no.4 s.85
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• pp.332-339
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• 2005

The environmental regulations in the world has been reinforced and many nations has devoted themselves to the development of cost-effective technology. Selective catalyst reduction(SCR) and selective non-catalyst reduction (SNCR) processes are mainly used to treat nitrogen oxidants generated from fossil-fuel combustion. One of these typical technologies for reduction of do-NOx is SNCR process has increased continuously because of the low cost for building and maintenance. Nevertheless the researches on the application to real scale plant by the reductant like Urea are rarely studied. In this paper, an experimental investigations were performed on the SNCR process in the industrial waste incineration plant. With no reducing agent, the concentration of NOx stayed in around 180 ppm $(O_2\;12\%)$ with the exhausting temperature of $950^{\circ}C$ and changed within the range of 20 ppm to remain relatively consistent. When $10\;wt\%)$ of a solution was added, the efficiency of denitrification reached above $61.4\%$ with the NSR of 2.0 and the exhausting temperature of $950^{\circ}C.$ When the concentration of the urea solution was set to $10\;wt\%$ and the sprinkling to four nozzles, the reaction temperature was reduced to about $50~100^{\circ}C$ with a mixture of $10\;wt\%\;CH_3OH\;and\;5wt\%\;Na_2CO_3$ in $40\;wt\%$ of the solution. The NOx removal efficiency increased to $78.4\%,$ achieving a broader and expansive range of reaction temperatures than the addition of an unmixed pure solution.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.11
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• pp.7433-7438
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• 2015

Deactivation characteristics of $V_2O_5/TiO_2$ catalysts were studied for selective catalytic reduction(SCR) of NOx with ammonia in the presence of $SO_2$. Performance of catalyst was investigated for $deNO_x$ activity while changing temperature, $SO_2$ concentration. The activity of catalyst was decreased with the increase of $SO_2$ concentration and reaction time. Also, degree of activity drop was largely decreased with the increase of reaction temperature in the range of $250{\sim}300^{\circ}C$. Physicochemical properties of deactivated catalysts were characterized by BET, XRD, SEM, TPD analysis. According to the analysis results, deactivation phenomena occur due to the relatively high formation of ammonium sulfate salts, which created by unreacted ammonia and water in the presence of $SO_2$. It was revealed that ammonium sulfate cause the pore plogging of support and deposition of active matter.

• 한국연소학회:학술대회논문집
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• 2007.05a
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• pp.98-103
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• 2007

The number of vehicles employing diesel engines is rapidly rising. Accompanying this trend, application of an after-treatment system is strictly required as a result of reinforced exhaust regulations. The Diesel Particulate Filter (DPF) system is considered as the most efficient method to reduce particulate matter (PM), but the improvement of a regeneration performance at any engine operation point presents a considerable challenge by itself. Temperature, gas compostion and flow rate of exhaust gas are important parameters in DPF evaluation, especially regeneration process. Engine dynamometer and degment tester are generally used in DPF evaluation so far. But these test method couldn't reveal the effect of various parameters on real DPF, such as O2 concentration, amount of soot and exhaust gas temperature. This research has studied the possibility using dump combustor that used to take an approach lean premixed combustion in gas turbine for a DPF power and optimized. It is possible that utilize the system as DOC (Diesel Oxidation Catalyst) and SCR(Selective Catalytic Reduction) assessments test as well as DPF evaluation

• Proceedings of the KAIS Fall Conference
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• 2011.05a
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• pp.320-322
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• 2011

저온에서의 탈질능력이 우수한 망간계 촉매를 바탕으로 수소-TPR 장치를 사용하여 저온에서의 활성을 파악하였다. 상기 결과를 바탕으로 주요 공정조건인 반응온도, 유속, 수분함량, 주입물 농도, 주입가스 중 수분함량 등에 대한 탈질능의 변화를 조사하였다. 실험결과 망간계 촉매의 경우 반응온도가 증가할수록 탈질능력은 감소하였으며 수분함량에 대해서도 탈질효율이 크게 영향을 받음을 알 수 있었다.

• Korean Journal of Metals and Materials
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• v.50 no.3
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• pp.201-205
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• 2012

The effects of various manganese precursors for the low-temperature selective catalytic reduction (SCR) of $NO_x$ were investigated in terms of structural, morphological, and physico-chemical analyses. $MnO_x/TiO_2$ catalysts were prepared from three different precursors, manganese nitrate, manganese acetate(II), and manganese acetate(III), by the sol-gel method. The manganese acetate(III)-$MnO_x/TiO_2$ catalyst tended to suppress the phase transition from the anatase structure to the rutile or the brookite after calcination at $500^{\circ}C$ for 2 h. It also had a high specific surface area, which was caused by a smaller particle size and more uniform distribution than the others. The change of catalytic acid sites was confirmed by Raman and FT-IR spectroscopy and the manganese acetate(III)-$MnO_x/TiO_2$ had the strongest Lewis acid sites among them. The highest de-NOx efficiency and structural stability were achieved by using the manganese cetate(III) as a precursor, because of its high specific surface area, a large amount of anatase $TiO_2$, and the strong catalytic acidity.