• Title/Summary/Keyword: $H_2$ SCR

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An Experimental and Modeling Study on the Oxidation Kinetics of Nitric Oxide over Platinum-based Catalysts (백금계 촉매상에서 산화질소(NO)의 산화반응속도에 관한 실험 및 모델링 연구)

  • Kim, Young-Deuk;Jeong, Soo-Jin;Kim, Woo-Seung
    • Transactions of the Korean Society of Automotive Engineers
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    • v.20 no.5
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    • pp.71-80
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    • 2012
  • To improve the $NO_X$ conversion over a SCR (selective catalytic reduction) catalyst, the DOC (diesel oxidation catalyst) is usually placed upstream of the SCR catalyst to enhance the fast SCR reaction ($4NH_3+2NO+2NO_2{\rightarrow}4N_2+6H_2O$) using equimolar amounts of NO and $NO_2$. Here, a ratio of $NO_2/NO_X$ above 50% should be avoided, because the reaction with $NO_2$ only ($4NH_3+4NO+O_2{\rightarrow}4N_2+6H_2O$) is slower than the standard SCR reaction ($4NH_3+4NO+O_2{\rightarrow}4N_2+6H_2O$). In order to accurately predict the performance characteristics of SCR catalysts, it is therefore desired to develop a more simple and reliable mathematical and kinetic models on the oxidation kinetics of nitric oxide over a DOC. In the present work, the prediction accuracy and limit of three different chemical reaction kinetics models are presented to describe the chemicophysical characteristics and conversion performance of DOCs. Steady-state experiments with DOCs mounted on a light-duty four-cylinder 2.0-L turbocharged diesel engine then are performed, using an engine-dynamometer system to calibrate the kinetic parameters such as activation energies and preexponential factors of heterogeneous reactions. The reaction kinetics for NO oxidation over Pt-based catalysts is determined in conjunction with a transient one-dimensional (1D) heterogeneous plug flow reactor (PFR) model with diesel exhaust gas temperatures in the range of 115~$525^{\circ}C$ and space velocities in the range of $(0.4{\sim}6.5){\times}10^5\;h^{-1}$.

An Experimental Study on the NH3-SCR of NOx over a Vanadium-based Catlayst (바나듐 계열 촉매를 통한 NOx의 NH3-SCR에 관한 실험적 연구)

  • Jeong, Hee-Chan;Sim, Sung-Min;Kim, Young-Deuk;Jeong, Soo-Jin;Kim, Woo-Seung
    • Transactions of the Korean Society of Automotive Engineers
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    • v.20 no.1
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    • pp.20-27
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    • 2012
  • The $NH_3$-SCR characteristics of $NO_X$ over a V-based catalyst are experimentally examined over a wide range of operating conditions, i.e., $170-590^{\circ}C$ and $30,000-50,000h^{-1}$, with a simulated diesel exhaust containing $NH_3$, NO, $NO_2$, $O_2$, $H_2O$, and $N_2$. The influences of the space velocity and oxygen concentration on the standard-SCR reaction are analyzed, and it is shown that the low space velocity and high oxygen concentration promote the SCR activity by ammonia. The best $deNO_X$ efficiency is obtained with a $NO_2/NO_X$ ratio of 0.5 because of an enhanced chemical activity induced by the fast-SCR reaction, while at the $NO_2/NO_X$ ratios above 0.5 the $deNO_x$ activity decreases due to the slow-SCR reaction. The oxidation of ammonia begins to take place at about $300^{\circ}C$ and the reaction products, such as $N_2$, NO, $NO_2$, $N_2O$, and $H_2O$, are produced by the undesirable oxidation reactions of ammonia, particularly at high temperatures above $450^{\circ}C$. Also, $NO_2$ decomposes to NO and $O_2$ at temperatures above $240^{\circ}C$. Therefore, $NO_2$ decomposition and ammonia oxidation reactions deteriorate significantly the SCR catalytic activity at high temperatures.

Experimental Study on Characteristics of NOX Reduction with Urea-Selective Catalytic Reduction System in Diesel Passenger Vehicle (승용 디젤차량에서 Urea-SCR 시스템의 NOX 저감 특성에 관한 실험적 연구)

  • Park, Seungwon;Lee, Seangwock;Cho, Yongseok;Kang, Yeonsik
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.41 no.4
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    • pp.269-275
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    • 2017
  • $NO_X$ reducing technique such as LNT, LNC, and selective catalytic reduction (SCR) have been developed and applied, especially on heavy-duty vehicles. However, it is expected that $NO_X$ reduction techniques will also be applied to diesel passenger vehicles. The urea-SCR system is receiving attention as the most effective $NO_X$ reduction technology without a fuel penalty. Thus, many advanced countries are developing this technology. The urea-SCR system sprays an aqueous urea solution that separates $NO_X$ into $N_2$ and $H_2O$, which are harmless and emitted into the atmosphere. The urea injected in front of the SCR catalyst should be changed to 100% $NH_3$, which is required for $NO_X$ reduction in the SCR system to maximize the reduction efficiency. The purpose of this study was to determine the basic data for the urea-SCR system to maximize the $NO_X$ reduction efficiency by understanding the $NO_X$ reduction characteristics in a real passenger vehicle to comply with the post EURO-6 emission regulation.

An Experimental Study on $NO_x$ Reduction Efficiency and $NH_3$ Conversion Efficiency under Various Conditions of Reductant Injection on SCR and AOC (SCR 촉매와 AOC 촉매에서 환원제 분사에 따른 $NO_x$ 저감효율과 $NH_3$ 변환효율에 관한 실험적 연구)

  • Dong, Yoon-Hee;Choi, Jung-Hwang;Cho, Yong-Seok;Lee, Seang-Wock;Lee, Seong-Ho;Oh, Sang-Ki;Park, Hyun-Dae
    • Transactions of the Korean Society of Automotive Engineers
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    • v.18 no.5
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    • pp.85-90
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    • 2010
  • As the environmental regulation of vehicle emission is strengthened, investigations for $NO_x$ and PM reduction strategies are popularly conducted. Two current available technologies for continuous $NO_x$ reduction onboard diesel vehicles are Selective Catalytic Reduction (SCR) using aqueous urea and lean $NO_x$ trap (LNT) catalysts. The experiments were conducted to investigate the $NO_x$ reduction performance of SCR system which can control the ratio of $NO/NO_2$, temperature and SV(space velocity), and the model gas was used which is similar to a diesel exhaust gas. The maximum reduction efficiency is indicated when the $NO:NO_2$ ratio is 1:1 and the SV is 30,000 $h^{-1}$ in $300^{\circ}C$. Generally, ammonia slip from SCR reactors are rooted to incomplete conversion of $NH_3$ over the SCR. In this research, slip was occurred in 6cases (except low SV and $NO:NO_2$ ratio is 1:1) after SCR. Among 6 case of slip occurrence, the maximum conversion efficiency is observed when SV is 60,000 $h^{-1}$ in $400^{\circ}C$.

Separation Behavior of Vanadium and Tungsten from the Spent SCR DeNOX Catalyst by Strong Basic Anion Exchange Resin (SCR 탈질 폐촉매로부터 강염기성 음이온교환수지를 이용한 바나듐/텅스텐 분리거동 고찰)

  • Heo, Seo-Jin;Jeon, Jong-Hyuk;Kim, Chul-Joo;Chung, Kueong-Woo;Jeon, Ho-Seok;Yoon, Do-Young;Yoon, Ho-Sung
    • Resources Recycling
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    • v.29 no.5
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    • pp.38-47
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    • 2020
  • In this study, factors affecting the adsorption reaction for the separation/recovery of V and W using Lewatit monoplus MP 600, a strong basic anion exchange resin, from the leachate obtained through the soda roasting-water leaching process from the spent SCR DeNOX catalyst investigated and the adsorption mechanism was discussed based on the results. In the case of the mixed solution of V and W, both ions showed a high adsorption ratio at pH 2-6, but the adsorption of W was greatly reduced at pH 8. In the adsorption isothermal experiment, both V and W were fitted well at the Langmuir adsorption isotherm, and the reaction kinetics were fitted well at pseudo-second-order. As a result of conducting an adsorption experiment by adjusting the pH with H2SO4 to remove Si, which inhibits the adsorption of V and W from the leachate, the lowest W adsorption ratio was shown at pH 8.5. Desorption of W was hardly achieved in strongly acidic solutions, and desorption of V was well performed in both strongly acidic and strongly basic solutions.

A Study on the Regeneration Effects of Commercial $V_2O_5-WO_3/TiO_2$ SCR Catalyst for the Reduction of NOx (질소산화물 제거용 상용 $V_2O_5-WO_3/TiO_2$ SCR 폐 촉매의 재생 효과 고찰)

  • Park, Hea-Kyung
    • Journal of Korean Society of Environmental Engineers
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    • v.27 no.8
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    • pp.859-869
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    • 2005
  • The commercial $V_2O_5-WO_3/TiO_2$ catalysts which had been exposed to the off gas from incinerator for a long time were regenerated by physical and chemical treatment. The catalytic properties and NOx conversion reactivity of those catalysts were examined by analysis equipment and NOx conversion experiment. The characterization of the catalysts were performed by XRD(x-ray diffractometer), BET, POROSIMETER, EDX(energy dispersive x-ray spectrometer), ICP(inductively coupled plasma), TGA(thermogravimetric analyzer) and SEM (scanning electron microscopy). NOx conversion experiment were performed with simulated off gas of the incinerator and $NH_3$ was used as a reductant of SCR reaction. Among the regeneration treatment methods which were applied to regenerate the aged catalysts in this study, it showed that the heat treatment method had excellent regeneration effect on the catalytic performance for NOx conversion. The catalytic performance of the regenerated catalysts with heat treatment method were recovered over than 95% of that of fresh catalyst. For the regenerated catalysts with the acid solution(pH 5) and the alkali solution(pH 12), the catalytic performance were recovered over than 90% of that of fresh catalyst. From the characterization results of the regenerated catalysts, the specific surface area was recovered in the range of $85{\sim}95%$ of that of fresh catalyst. S and Ca element, which are well known as the deactivation materials for the SCR catalysts, accumulated on the aged catalyst surface were removed up to maximum 99%. Among the P, Cr, Zn and Pb elements accumulated on the aged catalyst surface, P, Cr and Zn element were removed up to 95%. But the Pb element were removed in the range of $10{\sim}30%$ of that of fresh catalyst.

Effect of Change of Hydrogen Rich Reductant on HC-SCR over Co-Pt/ZSM5 Catalyst (수소 풍부 환원제 변화가 Co-Pt/ZSM5 촉매를 사용하는 탈질 HC-SCR 반응에 미치는 영향)

  • Kim, Seong-Soo;Kim, Dae-Young;Oh, Se-Young;Yoo, Seong-Jeon;Sur, Young-Sek;Kim, Jin-Gul
    • Transactions of the Korean hydrogen and new energy society
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    • v.23 no.3
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    • pp.199-206
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    • 2012
  • HC-SCR was conducted over Co-Pt/ZSM5 catalyst coated over 200 cpsi cordierite in the condition of atomspheric pressure and $200^{\circ}C-500^{\circ}C$. Weight ratio of Co/Pt determined from EDX analysis was 8/2, which was almost equal to the weight ratio at preparation step. XPS showed that nitrates within cobalt precursor and chlorine withn Pt precursor were removed. TEM result demonstrated that crystallite size of cobalt and Pt was under 5nm. Among these tested hydrocarbon reductants, isobutane ($i-C_4H_{10}$) showed the highest de-$NO_x$ yield of 80% under the condition of the mole ratio of reductant/NOx=1.0 at $180^{\circ}C$. De-$NO_x$ yield from HC-SCR was increased as the carbon number of hydrocarbon reductant was increased. The decrease of bonding energy between C and H of HC reductant played a role to increase of de-$NO_x$ yield, which indicated that the dissociation step of C-H bond of hydrocarbon molecule might be the rate determining step of HC-SCR. The increase of oxygen concentration in the feed resulted in the decrease of de-$NO_x$ yield but the increase of CO and $N_2O$ yield.

The Study on the Effect of Phosphorous Poisoning of V/W/TiO2 Catalyst According to the Addition of Sb in NH3-SCR (NH3-SCR에서 Sb 첨가에 따른 V/W/TiO2 촉매의 Phosphorous 피독 영향 연구)

  • Jung, Min Gie;Shin, Jung Hun;Lee, Yeon Jin;Hong, Sung Chang
    • Applied Chemistry for Engineering
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    • v.32 no.5
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    • pp.516-523
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    • 2021
  • A study using selective catalytic reduction (SCR) was conducted in conjunction with ammonia as a reducing agent for controlling nitrogen oxides, a typical secondary inducer of fine dust in the atmosphere. For NH3-SCR experiments, a commercial catalyst of V/W/TiO2 only and also V/W-Sb/TiO2 catalyst with Sb were used, and phosphorous durability was confirmed. As a result of NH3-SCR experiments, it was confirmed that the addition of Sb to V/W/TiO2 had durability against phosphorous. In addition, the physical and chemical properties were comparatively analyzed through BET, XPS, H2-TPR, NH3-TPD, and FT-IR analysis. From the anaylsis results, when Sb was added to V/W/TiO2 catalyst, P was also added resulting in the formation of SbPO4 and the generation of VOPO4 was suppressed. The phosphorous durability was confirmed by maintaining the redox characteristics of the catalyst before P was added.

Characteristics of Mercury Oxidation by an SCR Catalyst with Gas Composition (가스조성에 따른 선택적 환원촉매의 수은 산화 특성)

  • Lee, Sang-Sup;Kim, Kwang-Yul;Oh, Kwang-Joong;Jeon, Jun-Min;Kim, Do-Jeung;Kim, Ju-Yeong
    • 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.

A Simulation Study on SCR(Steam Carbon Dioxide Reforming) Process Optimization for Fischer-Tropsch Synthesis (Fischer-Tropsch 합성용 SCR(Steam Carbon Dioxide Reforming) 공정 최적화 연구)

  • Kim, Yong Heon;Koo, Kee Young;Song, In Kyu
    • Korean Chemical Engineering Research
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    • v.47 no.6
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    • pp.700-704
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    • 2009
  • A simulation study on SCR(steam carbon dioxide reforming) in gas-to-liquid(natural gas to Fischer-Tropsch synthetic fuel) process was carried out in order to find optimum reaction conditions for SCR experiment. Optimum operating conditions for SCR process were determined by changing reaction variables such as temperature and $CH_4/steam/CO_2$ feed ratio. Simulation was carried out by Aspen Plus. During the simulation, overall process was assumed to proceed under steady-state conditions. It was also assumed that physical properties of reaction medium were governed by RKS(Redlich-Kwong-Soave) equation. Optimum simulation variables such as temperature and feed ratio were determined by considering $H_2/CO$ ratio for FTS(Fischer-Tropsch synthesis), $CH_4$ conversion, and $CO_2$ conversion. Simulation results showed that optimum reaction temperature and $CH_4/steam/CO_2$ feed ratio in SCR process were $850^{\circ}C$ and 1.0/1.6/0.7, respectively. Under optimum temperature of $850^{\circ}C$, $CH_4$ conversion and $CO_2$ conversion were found to be 99% and 49%, respectively.