scholarly journals Rapid Ammonia Carriers for SCR Systems Using MOFs [M2(adc)2(dabco)] (M = Co, Ni, Cu, Zn)

Catalysts ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 1444
Author(s):  
Zhejian Cao ◽  
Kritika Narang Landström ◽  
Farid Akhtar
Keyword(s):  
Catalytic Reduction ◽  
Uptake Capacity ◽  
Ammonia Adsorption ◽  
Ammonia Uptake ◽  
Ammonia Desorption ◽  
No2 Reduction ◽  
Rapid Kinetics ◽  
Cyclic Adsorption ◽  
Scr System ◽  
Adsorption Desorption

Ammonia is one of the most common reductants for the automotive selective catalytic reduction (SCR) system owing to its high NO2 reduction (deNOx) efficiency. However, ammonia carriers for the SCR system have sluggishly evolved to achieve rapid ammonia dosing. In this study, the MOFs [M2(adc)2(dabco)] (M = Co, Ni, Cu, Zn) were synthesized and characterized as ammonia carriers. Among the four obtained MOFs, Ni2(adc)2(dabco) possessed the highest surface area, 772 m2/g, highest ammonia uptake capacity, 12.1 mmol/g, and stable cyclic adsorption-desorption performance. All the obtained MOFs demonstrated physisorption of ammonia and rapid kinetics of ammonia adsorption and desorption. Compared with halide ammonia carrier MgCl2, the obtained MOFs showed four times faster adsorption kinetics to reach 90% of the ammonia uptake capacity. For the ammonia desorption, the Ni2(adc)2(dabco) provided 6 mmol/g ammonia dosing when temperature reached 125 °C in the first 10 min, which was six times of the ammonia dosing from Mg(NH3)6Cl2. The results offer a solution to shorten the buffering time for ammonia dosing in the SCR system.

Investigation on the Simulation of Control Strategy for a SCR System

2013 ◽  
Vol 860-863 ◽  
pp. 770-773
Author(s):  
You Hong Xiao ◽  
Wei Zheng ◽  
Yu Shan Jin ◽  
Xin Na Tian
Keyword(s):  
Control Strategy ◽  
Catalytic Reduction ◽  
Control Strategies ◽  
Catalytic Converter ◽  
Ammonia Desorption ◽  
Adsorbed Ammonia ◽  
Major Chemical ◽  
Feedback Control Strategy ◽  
Feed Forward Controller ◽  
Scr System

In this paper, the model of SCR after-treatment system is established by the software MATLAB and the control strategy for the system is studied also. Based on Eley-rideal mechanism, four major chemical reactions including the adsorption of ammonia, desorption of ammonia, selective catalytic reduction and oxidation of adsorbed ammonia are selected to study the SCR control strategy. Based on the energy conservation law, the equation calculating the temperature of the layered model is derived. Combined with the equations of chemical reaction process, a mathematical model of SCR catalytic converter is established. To achieve a high NOXreduction efficiency of SCR system, the reasonable and efficacious control strategies for the micro-element models of SCR catalytic is simulated, which including the feedback control strategy based on the feed-forward controller and the PID control strategy.

A Computational Investigation of Industrial Selective Catalytic Reduction Systems for NOx Control

2018 ◽  
Vol 140 (8) ◽  
Author(s):  
Oghare Victor Ogidiama ◽  
Tariq Shamim
Keyword(s):  
Selective Catalytic Reduction ◽  
Catalytic Reduction ◽  
Inlet Temperature ◽  
Complex Processes ◽  
Fast Scr ◽  
Conversion Performance ◽  
Nox Control ◽  
No2 Reduction ◽  
Scr System ◽  
Reaction Processes

The selective catalytic reduction (SCR) is a promising NOx (a mixture of NO and NO2) reduction technology for various applications. The SCR process entails the conversion of NOx by the use of a reducing agent such as ammonia and a suitable catalyst. Due to increasingly stricter NOx emission regulations, the SCR technology for NOx control needs continuous improvement. The improvement requires better understanding of complex processes occurring in the SCR system. The current study employs a mathematical model to elucidate the effect of key operating and geometric parameters on the performance of SCR systems. The model considers both standard and fast SCR reaction processes. The model was used to investigate the effects of NH3/NOx and NO2/NOx ratios in the exhaust on the SCR performance and the effect of using a dual layer SCR system. Furthermore, the effect of different operating parameters and the interdependence of parameters is analyzed by using a factorial approach. The results show that the SCR performance is very sensitive to NH3/NOx ratio. The SCR performance is also affected by the NO2/NOx ratio particularly at low temperatures. The optimal NOx conversion performance requires a combination of NH3/NOx ratio of 1.0, NO2/NOx ratio of 0.5, low space velocities, and high inlet temperature. The results depict that adding a second catalyzed layer results in increased reaction activity especially when the concentration is still high after the first layer.

Simultaneous Optimization of Configuration and Control for a Passive SCR System

2018 ◽  
Author(s):  
Pingen Chen ◽  
Qinghua Lin
Keyword(s):  
Catalytic Reduction ◽  
Simultaneous Optimization ◽  
Computationally Efficient ◽  
System Architectures ◽  
Aftertreatment System ◽  
In Series ◽  
System Configurations ◽  
Scr System ◽  
And Control ◽  
Passive Scr

The configuration and control of aftertreatment systems have a significant impact on their functionalities and emission control performance. The traditional aftertreatment system configurations, i.e., connections from one aftertreatment subsystem to another subsystem in series, are simple but generally do not yield the optimal aftertreatment system performance. New aftertreatment configurations, in conjunction with new engine and aftertreatment control, can significantly improve engine efficiency and emission reduction performance. However, new configuration design requires human intuition and in-depth knowledge of engine and aftertreatment system design and control. The purpose of this study is to develop a general systematic and computationally-efficient method which enables automated and simultaneous optimization of passive selective catalytic reduction (SCR) system architectures and the associated non-uniform cylinder-to-cylinder combustion (NUCCC) controls based on a newly proposed highly reconfigurable passive SCR model structure and integer partition theory. The proposed method is general enough to account for passive SCR systems with two or more TWC stages. We demonstrate through this case study that the optimized passive SCR configuration, in conjunction with the optimized NUCCC control, can reduce the NH3 specific fuel consumption by up to 21.90%.

Experimental and kinetic analysis of hydrothermal aging effects on ammonia adsorption capacity over a commercial Cu-zeolite selective catalytic reduction catalyst

2018 ◽  
Vol 233 (12) ◽  
pp. 3030-3042
Author(s):  
Tae Joong Wang ◽  
In Hyuk Im
Keyword(s):  
Adsorption Capacity ◽  
Selective Catalytic Reduction ◽  
Catalytic Reduction ◽  
Adsorption Site ◽  
Selective Catalytic Reduction Catalyst ◽  
Aging Effects ◽  
Hydrothermal Aging ◽  
Ammonia Adsorption ◽  
Fresh Catalyst ◽  
Reduction Catalysts

Ammonia/urea selective catalytic reduction is an efficient technology to control NOx emission from diesel engines. One of its critical challenges is the performance degradation of selective catalytic reduction catalysts due to the hydrothermal aging experienced in real-world operations during the lifetime. In this study, hydrothermal aging effects on the reduction of ammonia adsorption capacity over a commercial Cu-zeolite selective catalytic reduction catalyst were investigated under actual engine exhaust conditions. Ammonia adsorption site densities of the selective catalytic reduction catalysts aged at two different temperatures of 750°C and 850°C for 25 h with 10% H2O were experimentally measured and compared to that of fresh catalyst on a dynamometer test bench with a heavy-duty diesel engine. The test results revealed that hydrothermal aging significantly decreased the ammonia adsorption capacity of the current commercial Cu-zeolite selective catalytic reduction catalyst. Hydrothermal treatment at 750°C reduced the ammonia adsorption site to 62.5% level of that of fresh catalyst, while hydrothermal treatment at 850°C lowered the adsorption site to 37.0% level of that of fresh catalyst. Also, in this study, numerical simulation and kinetic analysis were carried out to quantify the impact of hydrothermal aging on the reduction of ammonia adsorption capacity by introducing an aging coefficient. The kinetic parameter calibrations based on actual diesel engine tests with a commercial monolith Cu-zeolite selective catalytic reduction catalyst provided a highly realistic kinetic parameter set of ammonia adsorption/desorption and enabled a mathematical description of hydrothermal aging effect.

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

2018 ◽  
Vol 62 (1-4) ◽  
pp. 40-48 ◽  
Author(s):  
Yuanqing Zhu ◽  
Rongpei Zhang ◽  
Song Zhou ◽  
Chunan Huang ◽  
Yongming Feng ◽  
...  
Keyword(s):  
High Pressure ◽  
Performance Optimization ◽  
Catalytic Reduction ◽  
Marine Diesel ◽  
Scr System

An Experimental Study for NOx - Emission Reduction with Urea-SCR Technology in Vehicular Diesel Engines

2011 ◽  
Vol 71-78 ◽  
pp. 2089-2093 ◽  
Author(s):  
Qian Wang ◽  
Ming Xing Zhou ◽  
Bao Yi Wang
Keyword(s):  
Fuel Consumption ◽  
Control Strategy ◽  
Catalytic Reduction ◽  
Water Solution ◽  
Open Loop ◽  
Loop Control ◽  
Consumption Ratio ◽  
Future Emission ◽  
System Configurations ◽  
Scr System

In order to fulfill future emission standards for middle and heavy-duty vehicles like state Ⅳ and Ⅴ, advanced measures on exhaust gas and engine functionality are required. Selective Catalytic Reduction (SCR) technology is the unique technology currently which can improve the emission and reduce fuel consumption simultaneously. Firstly the reductants and its chemical reactions, SCR system configurations and its working principle and urea dosing control strategy are introduced. Then tests are conducted on a diesel engine with SCR system at bench. The results of ESC cycle show that NOx emission is decreased by more than 67% with the open-loop control strategy. Additionally, the urea and fuel consumption and ammonia leakage have been compared and analyzed respectively, the experiment data indicates that the urea water solution consumption ratio is only 5.7% of fuel for this SCR system, while its average ammonia slip is below 5 ppm.

scholarly journals Investigation of Urea Uniformity with Different Types of Urea Injectors in an SCR System

Catalysts ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 1269
Author(s):  
Muhammad Khristamto Aditya Wardana ◽  
Kwangchul Oh ◽  
Ocktaeck Lim
Keyword(s):  
Diesel Engine ◽  
Catalytic Reduction ◽  
Nox Reduction ◽  
Heavy Duty ◽  
Ammonia Gas ◽  
Experimental Parameters ◽  
Heavy Duty Diesel Engine ◽  
Heavy Duty Diesel ◽  
Scr System

Heavy-duty diesel engines in highway use account for more than 40% of total particulate and nitrogen oxide (NOx) emissions around the world. Selective catalytic reduction (SCR) is a method with effective results to reduce this problem. This research deals with problems in the urea evaporation process and ammonia gas distribution in an SCR system. The studied system used two types of urea injectors to elucidate the quality of ammonia uniformity in the SCR system, and a 12,000-cc heavy-duty diesel engine was used for experimentation to reduce NOx in the system. The uniformity of the generated quantities of ammonia was sampled at the catalyst inlet using a gas sensor. The ammonia samples from the two types of urea injectors were compared in experimental and simulation results, where the simulation conditions were based on experimental parameters and were performed using the commercial CFD (computational fluid dynamics) code of STAR-CCM+. This study produces temperatures of 371 to 374 °C to assist the vaporization phenomena of two injectors, the gas pattern informs the distributions of ammonia in the system, and the high ammonia quantity from the I-type urea injector and high quality of ammonia uniformity from the L-type urea injector can produce different results for NOx reduction efficiency quality after the catalyst process. The investigations showed the performance of two types of injectors and catalysts in the SCR system in a heavy-duty diesel engine.

Perspective on SCR NOx control for diesel vehicles

2019 ◽  
Vol 4 (6) ◽  
pp. 969-974 ◽  
Author(s):  
Christine K. Lambert
Keyword(s):  
Steady State ◽  
Selective Catalytic Reduction ◽  
Research Design ◽  
Catalytic Reduction ◽  
System Research ◽  
Reduction Of No ◽  
Diesel Vehicles ◽  
Aqueous Urea ◽  
Nox Control ◽  
Scr System

The selective catalytic reduction of NOx with aqueous urea (“urea SCR”) is originally a steady-state technology that has been successfully applied to diesel vehicles worldwide. This Perspective summarizes 20+ years of SCR system research, design, and future improvements.

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