Reaction mechanism and chemical kinetics of NH3-NO/NO2-SCR system with vanadium-based catalyst under marine diesel exhaust conditions

As one of the most effective NOx emission removing technologies to meet the Tier III limitation by International Maritime Organization, urea-selective catalytic reduction (SCR) technology is starting to be used in two-stroke marine diesel engines. Based on the two-cycle catalytic mechanism proposed by Topsoe, in combination with the exhaust characteristics of the marine diesel, expansion studies on detailed SCR reaction model were carried out in this paper. According to the temperature dependence of reaction pathway, SCR reaction model was divided into three parts: low temperature reaction pathway, standard SCR reaction pathway, and high temperature oxidation pathways, and an expanded NH3-NO/NO2-SCR reaction model for V2O5 catalyst was proposed in the paper. In order to verify the accuracy of the expanded SCR reaction model, simulating and testing studies of SCR reaction under marine diesel conditions were carried out with a commercial extruded V2O5/TiO2 catalyst. The simulation values are agreed well with experimental values at 150–500 ℃, and kinetics characteristics of SCR reaction process under V2O5/TiO2 catalyst can be predicted accurately with the expanded NH3-NO/NO2-SCR reaction model.

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Performance Optimization of High-pressure SCR System in a Marine Diesel. Part II: Catalytic Reduction and Process

Topics in Catalysis ◽

10.1007/s11244-018-1088-x ◽

2018 ◽

Vol 62 (1-4) ◽

pp. 40-48 ◽

Cited By ~ 5

Author(s):

Yuanqing Zhu ◽

Rongpei Zhang ◽

Song Zhou ◽

Chunan Huang ◽

Yongming Feng ◽

...

Keyword(s):

High Pressure ◽

Performance Optimization ◽

Catalytic Reduction ◽

Marine Diesel ◽

Scr System

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The Development and Implementation of Model-Based Control Algorithm of Urea-SCR Dosing System for Improving De-NOx Performance and Reducing NH3-Slip

ASME-JSME-KSME 2011 Joint Fluids Engineering Conference: Volume 1, Symposia – Parts A, B, C, and D ◽

10.1115/ajk2011-23011 ◽

2011 ◽

Author(s):

Soo-Jin Jeong ◽

Woo-Seung Kim ◽

Jung-Kwon Park ◽

Ho-Kil Lee ◽

Se-Doo Oh

Keyword(s):

Control Algorithm ◽

Catalytic Reduction ◽

Fluid Model ◽

Nox Reduction ◽

Reaction Model ◽

Urea Solution ◽

Model Based Control ◽

Model Based ◽

Nh3 Emission ◽

Scr System

The selective catalytic reduction (SCR) system is a highly-effective aftertreatment device for NOx reduction of diesel engines. Generally, the ammonia (NH3) was generated from reaction mechanism of SCR in the SCR system using the liquid urea as the reluctant. Therefore, the precise urea dosing control is a very important key for NOx and NH3 slip reduction in the SCR system. This paper investigated NOx and NH3 emission characteristics of urea-SCR dosing system based on model-based control algorithm in order to reduce NOx. In the map-based control algorithm, target amount of urea solution was determined by mass flow rate of exhaust gas obtained from engine rpm, torque and O2 for feed-back control NOx concentration should be measured by NOx sensor. Moreover, this algorithm cannot estimate NH3 absorbed on the catalyst Hence, the urea injection can be too rich or too lean. In this study, the model-based control algorithm was developed and evaluated based on the analytic model for SCR system. The channel thermo-fluid model coupled with finely tuned chemical reaction model was applied to this control algorithm. The vehicle test was carried out by using map-based and model-based control algorithms in the NEDC mode in order to evaluate the performance of the model based control algorithm.

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Energy Efficiency and Environmental Analysis of the Green-Hydrogen Fueled Slow Speed Marine Diesel Engine

International Journal of Multidisciplinary and Current Research ◽

10.14741/ijmcr/v.6.6.10 ◽

2018 ◽

Vol 6 (6) ◽

Author(s):

Nader R. Ammar

Keyword(s):

Diesel Engine ◽

Alternative Fuels ◽

Catalytic Reduction ◽

Energy Content ◽

Hydrogen Energy ◽

Marine Diesel Engine ◽

Slow Speed ◽

Marine Diesel ◽

Hydrogen Substitution ◽

Scr System

Marine diesel engines are facing challenges to cope with the emission-reduction regulations set by the international maritime organization (IMO). Hydrogen fuel is one of the alternative fuels which can be used to reduce the exhaust gas emissions from ships. The current paper investigates the effect of using diesel-hydrogen dual fuels on the environmental, energetic and exergetic performance parameters of slow speed marine diesel engine. The investigation is performed using Engineering Equation Solver (EES) software package. As a case study, slow speed diesel engine has been investigated. The results obtained revealed that the energetic and exergetic parameters are influenced by engine load and hydrogen substitution percent. The exergy efficiency is increased by 3.65%, 8.20%, 13.99%, and 21.7% for the hydrogen substitution percentages of 10%, 20%, 30%, and 40%, respectively compared with the diesel engine at full load. Environmentally, CO and CO2 emissions are reduced and NOx emissions are increased as the hydrogen energy content increases. Dual fuel engine with input hydrogen energy fractions of 10% and 20% will comply with the required NOx emission regulations set by IMO after using selective catalytic reduction (SCR) system. It will comply with the required regulations with relative percentages of 96.4% and 98.4%, respectively.

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Spatiotemporal organization of branched microtubule networks

10.1101/606889 ◽

2019 ◽

Author(s):

Akanksha Thawani ◽

Howard A Stone ◽

Joshua W Shaevitz ◽

Sabine Petry

Keyword(s):

Single Molecule ◽

Reaction Pathway ◽

Reaction Model ◽

Sequential Reaction ◽

Spatiotemporal Organization ◽

Nucleation Sites ◽

Egg Extracts ◽

Microtubule Networks ◽

Rate Limiting ◽

Kinetics Of

AbstractTo understand how chromosomes are segregated, it is necessary to explain the precise spatiotemporal organization of microtubules (MTs) in the mitotic spindle. We useXenopusegg extracts to study the nucleation and dynamics of MTs in branched networks, a process that is critical for spindle assembly. Surprisingly, new branched MTs preferentially originate near the minus-ends of pre-existing MTs. A sequential reaction model, consisting of deposition of nucleation sites on an existing MT, followed by rate-limiting nucleation of branches, reproduces the measured spatial profile of nucleation, the distribution of MT plus-ends and tubulin intensity. By regulating the availability of the branching effectors TPX2, augmin and γ-TuRC, combined with single-molecule observations, we show that first TPX2 is deposited on pre-existing MTs, followed by binding of augmin/γ-TuRC to result in the nucleation of branched MTs. In sum, regulating the localization and kinetics of nucleation effectors governs the architecture of branched MT networks.Impact StatementA sequential reaction pathway involving TPX2, augmin and γ-TuRC governs the assembly and architecture of branched microtubule networks.

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Spraying and Mixing Characteristics of Urea in a Static Mixer Applied Marine SCR System

Energies ◽

10.3390/en14185788 ◽

2021 ◽

Vol 14 (18) ◽

pp. 5788

Author(s):

Jaehwan Jang ◽

Sangkyung Na ◽

Heehwan Roh ◽

Seongyool Ahn ◽

Gyungmin Choi

Keyword(s):

Degrees Of Freedom ◽

Gas Flow ◽

Catalytic Reduction ◽

Water Solution ◽

Urea Solution ◽

Static Mixer ◽

Manufacturing Companies ◽

Conversion Reaction ◽

Marine Diesel ◽

Scr System

The most effective de-NOx technology in marine diesel applications is the urea-based selective catalytic reduction (SCR) system. The urea-SCR system works by injecting a urea solution into exhaust gas and converting this to NH3 and CO2. The injection, mixing, and NH3 conversion reaction behavior of the urea-water solution all have a decisive effect on the performance of the system. To improve de-NOx efficiency, it is important to provide enough time and distance for NH3 conversion and uniform distribution prior to the solution entering the catalyst. In this study, therefore, the characteristics of gas flow, NH3 conversion, and its distribution are investigated with a static mixer by means of numerical methods, providing a special advantage to ship manufacturing companies through the optimization of the urea-SCR system. The results show that the inclusion of the mixer induces strong turbulence and promotes the NH3 conversion reaction across a wider region compared to the case without the mixer. The mean temperature is 10 °C lower due to the activated endothermic urea-NH3 conversion reaction and the NH3 concentration is 80 PPM higher at 1D than those without the mixer. Moreover, the uniformity of NH3 distribution improved by 25% with the mixer, meaning that the de-NOx reaction can take place across all aspects of the catalyst thus maximizing performance. In other words, ship manufacturing companies have degrees of freedom in designing post-processing solutions for emissions by minimizing the use of the reduction agent or the size of the SCR system.

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Modeling of Urea-Water Solution Injection Spray in SCR System

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.232.583 ◽

2012 ◽

Vol 232 ◽

pp. 583-587

Author(s):

Nayak S. Nagaraj ◽

N. Kapilan ◽

Prabhu S. Sadashiva

Keyword(s):

Catalytic Reduction ◽

Water Solution ◽

Exhaust Gas ◽

Scr Catalyst ◽

Exhaust Gas Aftertreatment ◽

Study Results ◽

Exhaust Stream ◽

Experimental Values ◽

Scr System ◽

Aftertreatment Systems

To control the emissions from the diesel engines of modern automobiles, it requires the development of adequate and advanced exhaust gas aftertreatment devices. Selective Catalytic Reduction (SCR) is a method that can be used in mobile diesel engine aftertreatment systems to reduce harmful NOx emissions. Due to the toxicity and handling problems of ammonia, currently injection of a liquid Urea-Water Solution (UWS) into the exhaust stream approach is used. The water evaporates and the urea undergoes thermal decomposition producing ammonia that reacts with the NOx in the exhaust gas inside a SCR catalyst to produce nitrogen and water vapor. This work presents the study of UWS injection spray using commercial available CFD code, Fire v8.3. The evaporation of water from a single droplet of UWS is investigated theoretically and droplets are treated with Lagrangian particle tracking. Simulation study at different exhaust gas temperatures and injector locations is carried out and compared with experimental values. Thus, the present study results predict the local distribution and the conversion of the reducing agent.

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Kinetics of catalytic reduction of nitrogen oxide by carbon monoxide on CuO/Al2O3 catalyst

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19833202 ◽

1983 ◽

Vol 48 (11) ◽

pp. 3202-3208 ◽

Cited By ~ 5

Author(s):

Zdeněk Musil ◽

Vladimír Pour

Keyword(s):

Carbon Monoxide ◽

Nitrogen Oxide ◽

Rate Equation ◽

Catalytic Reduction ◽

Zero Order ◽

Spectroscopic Measurements ◽

First Order ◽

Ir Spectroscopic ◽

Kinetics Of ◽

Al2o3 Catalyst

The kinetics of the reduction of nitrogen oxide by carbon monoxide on CuO/Al2O3 catalyst (8.36 mass % CuO) were determined at temperatures between 413 and 473 K. The reaction was found to be first order in NO and zero order in CO. The observed kinetics are consistent with a rate equation derived from a mechanism proposed on the basis of IR spectroscopic measurements.

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In-situ stabilization of silver nanoparticles in polymer hydrogels for enhanced catalytic reduction of macro and micro pollutants

Zeitschrift für Physikalische Chemie ◽

10.1515/zpch-2020-1721 ◽

2020 ◽

Vol 0 (0) ◽

Author(s):

Luqman Ali Shah ◽

Rida Javed ◽

Mohammad Siddiq ◽

Iram BiBi ◽

Ishrat Jamil ◽

...

Keyword(s):

Catalytic Reduction ◽

Thermo Gravimetric Analysis ◽

Activation Parameters ◽

Reduction Reaction ◽

Gravimetric Analysis ◽

X Ray Diffraction ◽

In Situ Stabilization ◽

Hybrid Hydrogels ◽

Kinetics Of

AbstractThe in-situ stabilization of Ag nanoparticles is carried out by the use of reducing agent and synthesized three different types of hydrogen (anionic, cationic, and neutral) template. The morphology, constitution and thermal stability of the synthesized pure and Ag-entrapped hybrid hydrogels were efficiently confirmed using scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) and thermo gravimetric analysis (TGA). The prepared hybrid hydrogels were used in the decolorization of methylene blue (MB) and azo dyes congo red (CR), methyl Orange (MO), and reduction of 4-nitrophenol (4-NP) and nitrobenzene (NB) by an electron donor NaBH4. The kinetics of the reduction reaction was also assessed to determine the activation parameters. The hybrid hydrogen catalysts were recovered by filtration and used continuously up to six times with 98% conversion of pollutants without substantial loss in catalytic activity. It was observed that these types of hydrogel systems can be used for the conversion of pollutants from waste water into useful products.

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The Effect of Al on the Formation of a CrTaO4 Layer in Refractory High Entropy Alloys Ta-Mo-Cr-Ti-xAl

Oxidation of Metals ◽

10.1007/s11085-021-10046-7 ◽

2021 ◽

Author(s):

S. Schellert ◽

B. Gorr ◽

H.- J. Christ ◽

C. Pritzel ◽

S. Laube ◽

...

Keyword(s):

Mass Gain ◽

Positive Influence ◽

High Entropy Alloys ◽

Oxide Scales ◽

Temperature Oxidation ◽

Internal Corrosion ◽

High Entropy ◽

Continuous Mass ◽

Oxide Substrate ◽

Kinetics Of

AbstractIn this study, the effect of Al on the high temperature oxidation of Al-containing refractory high entropy alloys (RHEAs) Ta-Mo-Cr-Ti-xAl (x = 5; 10; 15; 20 at%) was examined. Oxidation experiments were performed in air for 24 h at 1200 °C. The oxidation kinetics of the alloy with 5 at% Al is notably affected by the formation of gaseous MoO3 and CrO3, while continuous mass gain was detected for alloys with the higher Al concentrations. The alloys with 15 and 20 at% Al form relatively thin oxide scales and a zone of internal corrosion due to the formation of dense CrTaO4 scales at the interface oxide/substrate. The alloys with 5 and 10 at% Al exhibit, on the contrary, thick and porous oxide scales because of fast growing Ta2O5. The positive influence of Al on the formation of Cr2O3 followed by the growth of CrTaO4 to yield a compact scale is explained by getter and nucleation effects.

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