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Keywords = ammonia slip catalyst

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16 pages, 1367 KiB  
Review
Advances and Challenges in Zeolite-Based Catalysts for the Selective Catalytic Oxidation of Ammonia
by Xiaoxin Chen, Jun Huang and Guoju Yang
Catalysts 2025, 15(3), 204; https://doi.org/10.3390/catal15030204 - 21 Feb 2025
Cited by 1 | Viewed by 946
Abstract
Ammonia (NH3) emissions from mobile sources pose significant environmental challenges, contributing to air pollution, ecosystem degradation, and climate change. The selective catalytic oxidation of NH3 (NH3-SCO) offers a sustainable solution by converting NH3 into nitrogen and water, [...] Read more.
Ammonia (NH3) emissions from mobile sources pose significant environmental challenges, contributing to air pollution, ecosystem degradation, and climate change. The selective catalytic oxidation of NH3 (NH3-SCO) offers a sustainable solution by converting NH3 into nitrogen and water, yet designing catalysts that balance high efficiency, selectivity, and stability under operational conditions remains a critical challenge. This review provides a comprehensive overview of zeolite-based catalysts, renowned for their high surface area, tunable pore structures, and exceptional hydrothermal stability, which make them ideal for NH3-SCO applications. The review synthesizes recent advancements in catalyst design, emphasizing innovative architecture, the role of zeolite frameworks in active site dispersion, and strategies for optimizing catalytic architectures. Key insights include an enhanced understanding of NH3-SCO reaction mechanisms, progress in mitigating catalyst deactivation caused by poisoning and sintering, and the development of bimetallic and core-shell catalysts to improve performance and durability. Current limitations, including the sensitivity of catalysts to operational environments and scalability issues, are critically analyzed, and potential strategies for overcoming these barriers are proposed. This review highlights the state-of-the-art in zeolite-based NH3-SCO catalysis, offering valuable insights into the fundamental and applied aspects of catalyst design. The findings presented here provide a roadmap for future innovations in environmental catalysis, paving the way for more efficient and robust solutions to ammonia emission control. Full article
(This article belongs to the Special Issue Synthesis and Catalytic Applications of Advanced Porous Materials)
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32 pages, 10642 KiB  
Review
A Review of Thermal Energy Management of Diesel Exhaust after-Treatment Systems Technology and Efficiency Enhancement Approaches
by Gang Wu, Guoda Feng, Yuelin Li, Tao Ling, Xuejun Peng, Zhilai Su and Xiaohuan Zhao
Energies 2024, 17(3), 584; https://doi.org/10.3390/en17030584 - 25 Jan 2024
Cited by 9 | Viewed by 3755
Abstract
The DOC (diesel oxidation catalyst), DPF (diesel particulate filter), SCR (selective catalytic reduction), and ASC (ammonia slip catalyst) are widely used in diesel exhaust after-treatment systems. The thermal management of after-treatment systems using DOC, DPF, SCR, and ASC were investigated to improve the [...] Read more.
The DOC (diesel oxidation catalyst), DPF (diesel particulate filter), SCR (selective catalytic reduction), and ASC (ammonia slip catalyst) are widely used in diesel exhaust after-treatment systems. The thermal management of after-treatment systems using DOC, DPF, SCR, and ASC were investigated to improve the efficiency of these devices. This paper aims to identify the challenges of this topic and seek novel methods to control the temperature. Insulation methods and catalysts decrease the energy required for thermal management, which improves the efficiency of thermal management. Thermal insulation decreases the heat loss of the exhaust gas, which can reduce the after-treatment light-off time. The DOC light-off time was reduced by 75% under adiabatic conditions. A 400 W microwave can heat the DPF to the soot oxidation temperature of 873 K at a regeneration time of 150 s. An SCR burner can decrease NOx emissions by 93.5%. Electrically heated catalysts can decrease CO, HC, and NOx emissions by 80%, 80%, and 66%, respectively. Phase-change materials can control the SCR temperature with a two-thirds reduction in NOx emissions. Pt-Pd application in the catalyst can decrease the CO light-off temperature to 113 °C. Approaches of catalysts can enhance the efficiency of the after-treatment systems and reduce the energy consumption of thermal management. Full article
(This article belongs to the Special Issue Advanced Thermal Management Technologies and Heat Transfer)
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17 pages, 2895 KiB  
Article
Ammonia as a Marine Fuel towards Decarbonization: Emission Control Challenges
by Georgia Voniati, Athanasios Dimaratos, Grigorios Koltsakis and Leonidas Ntziachristos
Sustainability 2023, 15(21), 15565; https://doi.org/10.3390/su152115565 - 2 Nov 2023
Cited by 9 | Viewed by 2936
Abstract
Decarbonization of the maritime sector to achieve ambitious IMO targets requires the combination of various technologies. Among alternative fuels, ammonia (NH3), a carbon-free fuel, is a good candidate; however, its combustion produces NOx, unburnt NH3 and N2 [...] Read more.
Decarbonization of the maritime sector to achieve ambitious IMO targets requires the combination of various technologies. Among alternative fuels, ammonia (NH3), a carbon-free fuel, is a good candidate; however, its combustion produces NOx, unburnt NH3 and N2O—a strong greenhouse gas (GHG). This work conducts a preliminary assessment of the emission control challenges of NH3 application as fuel in the maritime sector. Commercial catalytic technologies are applied in simulated NH3 engine exhaust to mitigate NH3 and NOx while monitoring N2O production during the reduction processes. Small-scale experiments on a synthetic gas bench (SGB) with a selective-catalytic reduction (SCR) catalyst and an ammonia oxidation catalyst (AOC) provide reaction kinetics information, which are then integrated into physico-chemical models. The latter are used for the examination of two scenarios concerning the relative engine-out concentrations of NOx and NH3 in the exhaust gas: (a) shortage and (b) excess of NH3. The simulation results indicate that NOx conversion can be optimized to meet the IMO limits with minimal NH3 slip in both cases. Excess of NH3 promotes N2O formation, particularly at higher NH3 concentrations. Engine-out N2O emissions are expected to increase the total N2O emissions; hence, both sources need to be considered for their successful control. Full article
(This article belongs to the Special Issue Renewable Fuels Research and Sustainable Energy Transition)
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16 pages, 9071 KiB  
Article
Study on Rates of NH3 Adsorption and Desorption in SCR on Various Engine Operation Conditions
by Hyun Jo, Ahyun Ko, Jinyoung Jang and Ocktaeck Lim
Sustainability 2023, 15(19), 14468; https://doi.org/10.3390/su151914468 - 4 Oct 2023
Cited by 1 | Viewed by 1788
Abstract
Aging diesel engines on the road require the development of an after-treatment system to meet current emission regulations, and a reduction in NOx (Nitrogen Oxide) is significant. The SCR (Selective Catalytic Reduction) system is the after-treatment system for removing NOx from exhaust gas [...] Read more.
Aging diesel engines on the road require the development of an after-treatment system to meet current emission regulations, and a reduction in NOx (Nitrogen Oxide) is significant. The SCR (Selective Catalytic Reduction) system is the after-treatment system for removing NOx from exhaust gas in diesel engines using NH3 (Ammonia) gas. However, the mixing and conversion process between NH3 and NOx in SCR has not been entirely clarified. That process produces NH3 slip in the catalyst surface; the NH3 slip will make the after-treatment performance worse. This study informs how the UWS (Urea Water Solution) injection controlling method can minimize the NH3 slip in the after-treatment system. For this, the NH3 adsorption and desorption rates are important factors for determining the quantity of UWS injection in the system. The NH3 adsorption rate and desorption rate in the SCR are not significantly affected by engine speed, i.e., the exhaust gas flow rate. However, as the exhaust gas temperature increased, the adsorption rate and desorption rate of NH3 in the SCR increased. Through this, the exhaust gas temperature dramatically affects the NH3 adsorption rate and desorption rate in the SCR. Therefore, if the urea water is injected based on this knowledge that the NH3 adsorption amount in the SCR decreases as the exhaust gas flow rate increases, NH3 slip can be suppressed and a high NOx reduction rate can be achieved. Therefore, if the SCR adsorption and desorption mechanisms are analyzed according to the exhaust temperature and the exhaust flow rate in this paper, it can be used as a reference for selecting an appropriate SCR when retrofitting an old diesel engine car. Full article
(This article belongs to the Collection Air Pollution Control and Sustainable Development)
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21 pages, 869 KiB  
Article
Selective Catalytic Reduction Catalyst Modeling for Control Purposes
by Olov Holmer and Lars Eriksson
Energies 2022, 15(21), 8182; https://doi.org/10.3390/en15218182 - 2 Nov 2022
Cited by 5 | Viewed by 2418
Abstract
In markets with strict emission legislations Selective Catalytic Reduction (SCR) has become the industry standard for NOx abatement in heavy-duty vehicles, and therefore modeling and control of these systems are vital. Many SCR catalyst models are available in the literature and in [...] Read more.
In markets with strict emission legislations Selective Catalytic Reduction (SCR) has become the industry standard for NOx abatement in heavy-duty vehicles, and therefore modeling and control of these systems are vital. Many SCR catalyst models are available in the literature and in this paper different models are discussed and classified into groups. Two models, based on the two most popular classes for control-oriented models, are implemented and compared with each other, one based on the continuously stirred-tank reactor approximation, and the other on a quasi-static behavior of the gas phase. The results show that assuming a quasi-static behavior of the gas phase in the catalyst gives better results in terms of accuracy and simulation time, especially when it comes to predictions of ammonia slip. Full article
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15 pages, 3458 KiB  
Article
Assessment of a Euro VI Step E Heavy-Duty Vehicle’s Aftertreatment System
by Barouch Giechaskiel, Tommaso Selleri, Roberto Gioria, Anastasios D. Melas, Jacopo Franzetti, Christian Ferrarese and Ricardo Suarez-Bertoa
Catalysts 2022, 12(10), 1230; https://doi.org/10.3390/catal12101230 - 14 Oct 2022
Cited by 8 | Viewed by 3214
Abstract
The latest generation of heavy-duty vehicles (Euro VI step E) have to respect low emission limits both in the laboratory and on the road. The most challenging pollutants for diesel vehicles are NOx and particles; nevertheless, NH3 and N2O [...] Read more.
The latest generation of heavy-duty vehicles (Euro VI step E) have to respect low emission limits both in the laboratory and on the road. The most challenging pollutants for diesel vehicles are NOx and particles; nevertheless, NH3 and N2O need attention. In this study, we measured regulated and unregulated pollutants of a Euro VI step E Diesel vehicle. Samples were taken downstream of (i) the engine, (ii) the Diesel oxidation catalyst (DOC) and catalyzed Diesel particulate filter (cDPF), and (iii) the selective catalytic reduction (SCR) unit for NOx with an ammonia slip catalyst (ASC). In addition to typical laboratory and real-world cycles, various challenging tests were conducted (urban driving with low payload, high-speed full-load driving, and idling) at 23 °C and 5 °C. The results showed high efficiencies of the DOC, DPF, and SCR under most testing conditions. Cold start cycles resulted in high NOx emissions, while high-temperature cycles resulted in high particle emissions. The main message of this study is that further improvements are necessary, also considering possible reductions in the emission limits in future EU regulations. Full article
(This article belongs to the Special Issue Catalytic Removal and Resource Utilization of NOx)
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15 pages, 3370 KiB  
Article
High-Dispersed V2O5-CuOX Nanoparticles on h-BN in NH3-SCR and NH3-SCO Performance
by Han-Gyu Im, Myeung-Jin Lee, Woon-Gi Kim, Su-Jin Kim, Bora Jeong, Bora Ye, Heesoo Lee and Hong-Dae Kim
Nanomaterials 2022, 12(14), 2329; https://doi.org/10.3390/nano12142329 - 6 Jul 2022
Cited by 18 | Viewed by 2985
Abstract
Typically, to meet emission regulations, the selective catalytic reduction of NOX with NH3 (NH3-SCR) technology cause NH3 emissions owing to high NH3/NOX ratios to meet emission regulations. In this study, V-Cu/BN-Ti was used to remove [...] Read more.
Typically, to meet emission regulations, the selective catalytic reduction of NOX with NH3 (NH3-SCR) technology cause NH3 emissions owing to high NH3/NOX ratios to meet emission regulations. In this study, V-Cu/BN-Ti was used to remove residual NOX and NH3. Catalysts were evaluated for selective catalytic oxidation of NH3 (NH3-SCO) in the NH3-SCR reaction at 200–300 °C. The addition of vanadium and copper increased the number of Brønsted and Lewis acid sites available for the reaction by increasing the ratio of V5+ and forming Cu+ species, respectively. Furthermore, h-BN was dispersed in the catalyst to improve the content of vanadium and copper species on the surface. NH3 and NOX conversion were 98% and 91% at 260 °C, respectively. Consequently, slipped NH3 (NH3-Slip) emitted only 2% of the injected ammonia. Under SO2 conditions, based on the NH3 oxidation reaction, catalytic deactivation was improved by addition of h-BN. This study suggests that h-BN is a potential catalyst that can help remove residual NOX and meet NH3 emission regulations when placed at the bottom of the SCR catalyst layer in coal-fired power plants. Full article
(This article belongs to the Special Issue Boron Nitride-Based Nanomaterials)
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26 pages, 13122 KiB  
Article
Effect of Catalyst Inlet Flow Field Distribution Characteristics on Outlet NO Concentration Distribution in SCR Denitration Reactor Based on Monte Carlo Method
by Wanying Sun, Mengmeng Ye, Yihua Gao, Yi Sun, Fuping Qian, Jinli Lu, Shenghua Wu, Naijing Huang and Bing Xu
Atmosphere 2022, 13(6), 931; https://doi.org/10.3390/atmos13060931 - 8 Jun 2022
Cited by 4 | Viewed by 2342
Abstract
Selective catalytic reduction (SCR) technology plays a crucial role in flue gas denitration. The nonuniform distribution of catalyst inlet parameters causes the nonuniform distribution of NO concentration at the outlet, thus affecting accuracy of ammonia injection. Regarding this issue, this paper describes the [...] Read more.
Selective catalytic reduction (SCR) technology plays a crucial role in flue gas denitration. The nonuniform distribution of catalyst inlet parameters causes the nonuniform distribution of NO concentration at the outlet, thus affecting accuracy of ammonia injection. Regarding this issue, this paper describes the impacts of nonuniform velocity and temperature on both the confidence of NO concentration measured at a single measuring point at the outlet and the denitration efficiency, which can provide a basis for structural optimization of SCR denitration reactor and decrease in ammonia slip. The random distribution form of velocity and temperature above the catalyst layer are derived from the actual gas volume and the actual SCR reactor model, and then the catalyst inlet boundary conditions were generated with different relative standard deviation of velocity and temperature accordingly. The confidence of outlet NO concentration measurement results can be counted by means of Monte Carlo simulation. Finally, the relation model can be obtained to calculate the confidence of outlet NO concentration measurement results at different working conditions. The results show that within the gas volume range of this work, in order to ensure the confidence of the NO concentration measurement results, the relative standard deviation of temperature before the catalyst inlet must be within 0.005 and the relative standard deviation of velocity before the catalyst inlet must be within 0.1. With the increase in relative standard difference in temperature, there is a slight decrease in the efficiency of denitration. With the different mean value of temperature, the variation range of denitration efficiency is similar to that of temperature-relative standard difference. With the different mean value of velocity, the deviation range of corresponding efficiency is similar to that of the temperature-relative standard difference. When the relative standard difference in velocity increases, the denitration efficiency decreases slightly. The greater velocity value, the decreasing range of denitration efficiency is larger than the variation range of relative standard difference in velocity. Full article
(This article belongs to the Special Issue Flue Gases: Measurement and Treatment)
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19 pages, 1804 KiB  
Article
Combined NOx and NH3 Slip Reduction in a Stoker Boiler Equipped with the Hybrid SNCR + SCR System FJBS+
by Robert Wejkowski, Sylwester Kalisz, Przemysław Garbacz and Izabella Maj
Energies 2021, 14(24), 8599; https://doi.org/10.3390/en14248599 - 20 Dec 2021
Cited by 10 | Viewed by 3166
Abstract
The application of secondary NOx control methods in medium to low-capacity furnaces is a relatively new topic on the energy market and thus requires further research. In this paper, the results of full-scale research of SNCR and hybrid SNCR + SCR methods [...] Read more.
The application of secondary NOx control methods in medium to low-capacity furnaces is a relatively new topic on the energy market and thus requires further research. In this paper, the results of full-scale research of SNCR and hybrid SNCR + SCR methods applied into a 29 MWth solid fuel fired stoker boiler is presented. The tests were performed for a full range of boiler loads, from 33% (12 MWth) to 103% (30 MWth) of nominal load. A novel SNCR + SCR hybrid process was demonstrated based on an enhanced in-furnace SNCR installation coupled with TiO2-WO3-V2O5 catalyst, which provides extra NOx reduction and works as an excess NH3 “catcher” as well. The performance of a brand-new catalyst was evaluated in comparison to a recovered one. The emission of NOx was reduced below 180 mg NOx/Nm3 at 6% O2, with ammonia slip in flue gas below 10 mg/Nm3. Special attention was paid to the analysis of ammonia slip in combustion products: flue gas and fly ash. An innovative and cost-effective method of ammonia removal from fly ash was presented and tested. The main idea of this method is fly ash recirculation onto the grate. As a result, ammonia content in fly ash was reduced to a level below 6.1 mg/kg. Full article
(This article belongs to the Special Issue Computational Thermal, Energy, and Environmental Engineering)
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16 pages, 693 KiB  
Article
Deactivation of V2O5−WO3/TiO2 DeNOx Catalyst under Commercial Conditions in Power Production Plant
by Maciej Zyrkowski, Monika Motak, Bogdan Samojeden and Krzysztof Szczepanek
Energies 2020, 13(23), 6200; https://doi.org/10.3390/en13236200 - 25 Nov 2020
Cited by 13 | Viewed by 3416
Abstract
Nitrogen dioxide is one of the most dangerous air pollutants, because its high concentration in air can be directly harmful to human health. It is also responsible for photochemical smog and acid rains. One of the most commonly used techniques to tackle this [...] Read more.
Nitrogen dioxide is one of the most dangerous air pollutants, because its high concentration in air can be directly harmful to human health. It is also responsible for photochemical smog and acid rains. One of the most commonly used techniques to tackle this problem in large combustion plants is selective catalytic reduction (SCR). Commercial SCR installations are often equipped with a V2O5−WO3/TiO2 catalyst. In power plants which utilize a solid fuel boiler, catalysts are exposed to unfavorable conditions. In the paper, factors responsible for deactivation of such a catalyst are comprehensively reviewed where different types of deactivation mechanism, like mechanical, chemical or thermal mechanisms, are separately described. The paper presents the impact of sulfur trioxide and ammonia slip on the catalyst deactivation as well as the problem of ammonium bisulfate formation. The latter is one of the crucial factors influencing the loss of catalytic activity. The majority of issues with fast catalyst deactivation occur when the catalyst work in off-design conditions, in particular in too high or too low temperatures. Full article
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16 pages, 2643 KiB  
Article
Hybrid Technology for DeNOxing by LNT-SCR System for Efficient Diesel Emission Control: Influence of Operation Parameters in H2O + CO2 Atmosphere
by Marina Cortés-Reyes, Concepción Herrera, María Ángeles Larrubia and Luis J. Alemany
Catalysts 2020, 10(2), 228; https://doi.org/10.3390/catal10020228 - 14 Feb 2020
Cited by 10 | Viewed by 3521
Abstract
The behavior and operation parameters were analyzed for the hybrid LNT-SCR (Lean NOx-Trap–Selective Catalytic Reduction) system with advanced catalyst formulations. Pt-Ba-K/Al2O3 was used as an NSR (NOx Storage and Reduction) or LNT catalyst effective in NOx [...] Read more.
The behavior and operation parameters were analyzed for the hybrid LNT-SCR (Lean NOx-Trap–Selective Catalytic Reduction) system with advanced catalyst formulations. Pt-Ba-K/Al2O3 was used as an NSR (NOx Storage and Reduction) or LNT catalyst effective in NOx and soot simultaneous removal whereas Cu-SAPO-34 with 2 wt.% of copper inside the structure was the small pore zeolite employed as the SCR catalyst. Under alternating and cyclic wet conditions, feeding volumetric concentrations of 1000 ppm of NO, 3% of O2, 1.5% of water, 0.3% of CO2, and H2 as a reductant, the NOx-conversion values were above 95% and a complete mineralization to nitrogen was registered using θ ≤ 3 (20 s of regeneration) and a hydrogen content between 10,000 and 2000 ppm in the whole temperature range tested. An excess of hydrogen fed (above 1% v/v) during the rich phase is unnecessary. In addition, in the low temperature range below 250 °C, the effect is more noticeable due to the further ammonia production and its possible slip. These results open the way to the scale up of the coupled catalytic technologies for its use in real conditions while controlling the influence of the operation map. Full article
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18 pages, 2787 KiB  
Article
Regulated and Non-Regulated Emissions from Euro 6 Diesel, Gasoline and CNG Vehicles under Real-World Driving Conditions
by Ricardo Suarez-Bertoa, Martin Pechout, Michal Vojtíšek and Covadonga Astorga
Atmosphere 2020, 11(2), 204; https://doi.org/10.3390/atmos11020204 - 14 Feb 2020
Cited by 83 | Viewed by 10970
Abstract
The transport sector is one of the main sources air pollutants. Different exhaust after-treatment systems have been implemented over the years to control the emissions of criteria pollutants. However, while reducing the emissions of the target compounds these systems can lead to the [...] Read more.
The transport sector is one of the main sources air pollutants. Different exhaust after-treatment systems have been implemented over the years to control the emissions of criteria pollutants. However, while reducing the emissions of the target compounds these systems can lead to the emissions of other pollutants and/or greenhouse gases such as NH3 or N2O. Following the implementation of the Real Driving Emissions (RDE) test procedure in the EU, vehicles have been equipped with more complex after-treatment configurations. The impact that these technologies may have on the emissions of non-regulated pollutants during real-world driving have not been evaluated until now. In the current study we present the on-road emissions of a series of non-regulated pollutants, including NH3, N2O, CH4 and HCHO, measured with a portable FTIR from a series of Euro 6d, Euro 6c and Euro 6d-TEMP, gasoline diesel and compressed natural gas (CNG) vehicles during real-world testing. The obtained results show that it is possible to measure N2O, NH3, CH4 and HCHO during on-road operation. The results also highlight the importance of the measurement of the emissions of these pollutants during real-world driving, as the emissions of NH3 (a particulate matter precursor) and those of N2O and CH4 (green-house gases) can be high from some vehicle technologies. NH3 emissions were up to 49 mg/km for gasoline passenger cars, up to 69 mg/km for the CNG light-commercial vehicle and up to 17 mg/km a diesel passenger car equipped with a selective catalytic reduction system (SCR). On the other hand, N2O and CH4 emissions accounted for up to 9.8 g CO2 eqv/km for a diesel passenger car equipped with a combination of diesel oxidation catalysts (DOC), lean NOx traps (LNT), SCR and possibly an ammonia slip catalyst ASC. Full article
(This article belongs to the Special Issue 10th Anniversary of Atmosphere: Air Quality)
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19 pages, 3522 KiB  
Article
Luenberger-Sliding Mode Observer Based Backstepping Control for the SCR System in a Diesel Engine
by Taixiong Zheng, Bin Yang, Yongfu Li and Ying Ma
Energies 2019, 12(22), 4270; https://doi.org/10.3390/en12224270 - 8 Nov 2019
Cited by 3 | Viewed by 3019
Abstract
In order to keep the ammonia (NH3) slip of the downstream selective catalytic reduction (SCR) system at a low level and simultaneously achieve a high nitrogen oxide (NOX) conversion rate, a Luenberger-sliding mode observer based backstepping control method is [...] Read more.
In order to keep the ammonia (NH3) slip of the downstream selective catalytic reduction (SCR) system at a low level and simultaneously achieve a high nitrogen oxide (NOX) conversion rate, a Luenberger-sliding mode observer based backstepping control method is proposed. Considering that the internal working condition of the catalyst cannot be measured by commercial sensors directly, a Luenberger-sliding mode observer is designed to estimate the ammonia concentration at the middle of the catalyst. In addition, based on the stepped distributed characteristic of the surface ammonia coverage ratio along the SCR axial direction, a backstepping control method is utilized for the SCR system, in which the SCR system is decomposed into two subsystems. Firstly, the Lyapunov function is designed to ensure the convergence of the downstream subsystem, and then the virtual control law is obtained. After that, taking the virtual control law as the tracking target of the upstream subsystem, the Lyapunov function of virtual control law is given. Finally, the actual control law of the whole closed loop system is acquired. Simulations under different conditions are conducted to investigate the effect of the proposed control method. In addition, comparisons with the traditional PID (Proportion Integration Differentiation) control are presented. Results show that the proposed method is much better than the PID control method in overshoot, setting time, and tracking error. Full article
(This article belongs to the Section B: Energy and Environment)
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22 pages, 6750 KiB  
Article
Numerical Investigation of SCR Mixer Design Optimization for Improved Performance
by Ghazanfar Mehdi, Song Zhou, Yuanqing Zhu, Ahmer Hussain Shah and Kishore Chand
Processes 2019, 7(3), 168; https://doi.org/10.3390/pr7030168 - 22 Mar 2019
Cited by 31 | Viewed by 6609
Abstract
The continuous increase in the number of stringent exhaust emission legislations of marine Diesel engines had led to a decrease in NOx emissions at the required level. Selective catalyst reduction (SCR) is the most prominent and mature technology used to reduce NO [...] Read more.
The continuous increase in the number of stringent exhaust emission legislations of marine Diesel engines had led to a decrease in NOx emissions at the required level. Selective catalyst reduction (SCR) is the most prominent and mature technology used to reduce NOx emissions. However, to obtain maximum NOx removal with minimum ammonia slip remains a challenge. Therefore, new mixers are designed in order to obtain the maximum SCR efficiency. This paper reports performance parameters such as uniformity of velocity, ammonia uniformity distribution, and temperature distribution. Also, a numerical model is developed to investigate the interaction of urea droplet with exhaust gas and its effects by using line (LM) and swirl (SM) type mixers alone and in combination (LSM). The urea droplet residence time and its interaction in straight pipe are also investigated. Model calculations proved the improvement in velocity uniformity, distribution of ammonia uniformity, and temperature distribution for LSM. Prominent enhancement in the evaporation rate was also achieved by using LSM, which may be due to the breaking of urea droplets into droplets of smaller diameter. Therefore, the SCR system accomplished higher urea conversion efficiency by using LSM. Lastly, the ISO 8178 standard engine test cycle E3 was used to verify the simulation results. It has been observed that the average weighted value of NOx emission obtained at SCR outlet using LSM was 2.44 g/kWh, which strongly meets International Maritime Organization (IMO) Tier III NOx (3.4 g/kWh) emission regulations. Full article
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17 pages, 7045 KiB  
Article
Model-Based Temperature Sensor Fault Detection and Fault-Tolerant Control of Urea-Selective Catalyst Reduction Control Systems
by Jie Hu, Junliang Wang, Jiawei Zeng and Xianglin Zhong
Energies 2018, 11(7), 1800; https://doi.org/10.3390/en11071800 - 9 Jul 2018
Cited by 4 | Viewed by 4530
Abstract
This paper aims at investigating the fault diagnosis of the selective catalyst reduction (SCR) outlet temperature sensors and fault-tolerant control methods of the SCR system, and three typical faults of downstream temperature sensors were modeled and analyzed to present influences of different faults [...] Read more.
This paper aims at investigating the fault diagnosis of the selective catalyst reduction (SCR) outlet temperature sensors and fault-tolerant control methods of the SCR system, and three typical faults of downstream temperature sensors were modeled and analyzed to present influences of different faults on the SCR system performances (such as nitrogen oxides (NOx) emission and conversion efficiency, NH3 slip, urea dosage and ammonia coverage estimation). A temperature model was established to estimate the SCR outlet temperature, and diagnostics were developed based on the differences between model estimates and sensor measurements. Once a downstream temperature sensor fault was detected, the fault-tolerant control will be enabled, and the output of the sensor may be substituted with the estimates of the model. Thus, SCR performances shall be maintained within the acceptable ranges. Moreover, a 0-D SCR model was also established to validate the capability of diagnostics and fault-tolerant control strategy over the European transient cycle (ETC). Full article
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