Catalyst Reduction System Research Articles

Pollutant emission characteristics of the close-coupled selective catalytic reduction system for diesel engines under low exhaust temperature conditions

The selective catalyst reduction system is an effective method for reducing pollutant emissions from diesel engines. To meet the increasingly strict requirements of pollutant emission regulations and further reduce the pollutant emissions of heavy diesel engines at low exhaust gas temperatures, a close-coupled selective catalyst reduction (ccSCR) system based on a corrugated substrate was proposed. Based on the corrugated substrate with V2O5-WO3/TiO2 catalysts, the pollutant emission characteristics of the ccSCR system were compared with those of a conventional selective catalyst reduction (SCR) system under the World Harmonized Transient Cycle at the exhaust gas temperature of 165 °C. Additionally, the effects of the volume ratio of ammonia to nitrogen (α) and the catalyst volume to engine gas capacity ratio (γ) on pollutant emissions of the ccSCR system were investigated. Results showed that pollutant emissions exhausted from the ccSCR system were significantly lower than those from the conventional SCR system. With the increase of α from 0.3 to 0.7 and γ from 0.33 to 0.76 in the ccSCR module, the NOx emission and NH3 slip of the ccSCR system decreased, and α had a larger effect on reducing pollutant emissions from the ccSCR system. The minimum values of NOx emission and NH3 slip were 0.22 g/kW·h and 2.33 ppm, respectively, at α = 0.7 and γ = 0.76 of the ccSCR module. The proposed ccSCR system was conducive to reducing the pollutant emission of diesel engines and its pollutant emission characteristics outperformed the conventional SCR system.

Development of Machine Learning Algorithms for Application in Major Performance Enhancement in the Selective Catalytic Reduction (SCR) System

Machine learning is used in this study to deal with the reduction in the design period and major performance improvement of the selective catalyst reduction system. The selective catalyst reduction system helps in the reduction in NOx emission in the diesel engine. The existing methods for the design and performance improvement of selective catalyst reduction systems tend to be inefficient, due to layout changes that require modification when mounting a vehicle based on previously designed models. There are some factors that can affect the design of the diesel engine selective catalyst reduction system that can be identified by applying an optimized design. The Taguchi orthogonal array design is used with the eight factors and three levels of the main design factors. The distance of the urea injector, the distance of the mixer, the inflow angle of the exhaust gas, the angle of the urea injector, the angle of the mixer, the mounting angle in the direction of rotation of the mixer inside the selective catalyst reduction pipe, the number of mixer blades, the and bending angle of the mixer blade are identified as the eight major factors involved. These factors can also be considered manufacturing factors and can be established through machine learning. Machine learning has the advantage of being more efficient compared to other methods in determining the relationship between the data for each mutual factor. Machine learning can help in reducing processing time, which can further decrease the cost of the design analysis and improve the performance of the selective catalyst reduction system. This study shows that the results are statistically significant as the p values of the mixer blade number and cone length are lower than 0.05.

Experimental Investigation of Urea Deposit Formation in Selective Catalyst Reduction System to Guide Product Development

Experimental Investigation of Urea Deposit Formation in Selective Catalyst Reduction System to Guide Product Development

Investigation on the effects of non-uniform porosity catalyst on SCR characteristic based on the field synergy analysis

Selective catalytic reduction catalyst was commonly used in the denitrification of exhaust from the internal combustion engine. In the paper, a three-dimensional mathematical model was developed and employed to study the flow and heat transfer in the non-uniform selective catalytic reduction catalyst system. The denitrification reaction of selective catalytic reduction catalyst was employed to predict the NOx conversion efficiency. In addition, the field synergy principle is employed to analyze the effects of velocity and temperature fields on the heat transfer process. The results show that the non-uniform porosity catalyst can effectively reduce the catalyst back pressure. At 100 g/s, the pressure drop in the non-uniform porosity catalyst was 0.91 kPa lower than the high porosity catalyst. The total heat transfer rate of the non-uniform porosity catalyst was on average 1.1% lower than the uniform porosity catalyst. The low heat transfer rate ensures that the temperature drop is reduced. Thus, the denitrification reaction is improved by the high temperature. In addition, the field synergy number of non-uniform porosity catalysts is on average 0.53% lower than uniform porosity catalysts, which indicates energy transfer from the diameter change region to the outside is reduced. This proves the non-uniform porosity structure is more favorable for the denitrification reaction.

Study on the Inlet Shape of a Selective Catalyst Reduction System with an Integrated Bypass Unit for Ships

Study on the Inlet Shape of a Selective Catalyst Reduction System with an Integrated Bypass Unit for Ships

Total Performance Evaluation of a Diesel Selective Catalytic Reduction Catalyst System through Laboratory-Scale Experiments

Some diesel engines have been found to emit excessive amounts of NOx according to the recently established emission standards in Japan, primarily due to the poor performance of on-board catalysts. ...

Investigation of the Emission Characteristics of Light-Duty Diesel Vehicles in Korea Based on EURO-VI Standards According to Type of After-Treatment System

This study analyzed the characteristics and distribution of emissions from diesel vehicles that are sold in Korea and satisfy the Euro-6 standards, according to after-treatment systems. To identify the emission distribution of diesel vehicles according to after-treatment systems, results of the certification tests conducted on 266 vehicle models were examined. Results of the certification tests on 86 vehicle models that were manufactured based on the standards for RDE after 2017 were examined according to the engine displacement and power. The emission characteristics of six vehicle models equipped with different types of after-treatment systems were verified through certification tests in the New European Driving Cycle and Worldwide Harmonized Light Vehicle Test Procedure modes and RDE tests, according to the after-treatment systems. Specifically, a chassis dynamometer and an emission analyzer were used in the certification test modes; a portable emissions measurement system was used in the RDE test. The results indicated that the amount of NOx emissions from diesel vehicles has been constantly decreasing since 2017 due to the implementation of standards for RDE and advancements in after-treatment systems. Furthermore, it was found that selective catalyst reduction systems must be installed in vehicles to satisfy Euro-6 standards for permissible emissions on real-roads.

Sulfur trioxide emissions from coal-fired power plants in China and implications on future control

SO3 is a significant gaseous precursor of secondary particulate matter and is also a key for the overall improvement of ambient air quality. In this study, SO3 emission characteristics for coal-fired power plants (CFPPs) from field experiments and existing studies are collected to study the SO3 transformation and removal characteristics and to determine the temporal and spatial distribution of SO3 emissions from CFPPs. The formation ratio of SO3 in boilers and selective catalyst reduction system is 0.9 ± 0.5% and 40.52 ± 19.23%, respectively. The formed SO3 is then removed by dust collectors and desulfurization systems in sequence, approximately 26.52–82.96% and 56.48–96.32%, respectively. Due to the development of air pollution control devices, SO3 emission in 2015 (71.0 kt) is almost equal to the emission in 2000 (70.9 kt) although coal consumption kept increasing. Some areas of the North China Plain have the highest distribution density of CFPPs, which implies more stringent SO3 emission limit may need to be considered in these regions for future control. Also, the monitoring method and control technologies should be developed simultaneously for better application of the emission limit.

Reduction of 4-nitrophenol by a disused adsorbent: EDA-functionalized magnetic cellulose nanocomposite after the removal of Cu2+

In this paper, the fabrication of magnetically separable organic-inorganic hybrid nanoadsorbent via the functionalization of Fe3O4@SiO2@Cellulose with glycidyl methacrylate (GMA) and then ethylenediamine (EDA) was studied. The obtained nanocomposite system was characterized using FT-IR, XRD, SEM, EDX and VSM analyses. The EDA-functionalized magnetic cellulose exhibited a perfect capability towards removal of Cu2+ as well as Pb2+, Cd2+, Zn2+ and Ni2+ ions from the aqueous solutions. In addition, the influence of pH, contact time and initial concentration of Cu2+ were also investigated on capacity of the new designed cellulose absorbent. The examinations resulted that the adsorption process of Cu2+ is obeyed from the pseudo-second order kinetic model and the Langmuir isotherm. The maximum adsorption capacity of Cu2+ ions on the nanomagnetic cellulose was 81.67 mg/g. The magnetic cellulose after removal of Cu2+ ions was successfully applied as an efficient catalyst system for reduction of 4-nitrophenol to 4-aminophenol with excess amounts of NaBH4 in water.

Optimal design of selective catalyst reduction denitrification system using numerical simulation

The performance of selective catalyst reduction systems highly depends on the degree of mixing between NH3 and NOx and the flow uniformity of velocity and concentration, which are sensitive to several parameters such as the installment of gate leafs, a hybrid grid, a straightener, and the ammonia injection method. In this work, computational fluid dynamics was applied to investigate these parameters in heat recovery steam generators. Performance of gate leafs and a new type of hybrid grid was considered. Analyses showed that gate leafs significantly improved the uniformity of velocity distribution and that the new type of hybrid grid improved the uniformity of concentration distribution. The velocity relative standard deviation decreased from 19.6% to 5.4%, and the concentration relative standard deviation decreased from 70% to 12.7%. Experiments also qualitatively confirmed the reliability of simulation results. Moreover, the hybrid grid was optimized with different structures. Results indicated that a 30° crossed angle could obtain a better mixing between NH3 and NOx with a slight decrease in pressure. In addition, an optimal injection method of the ammonia injection grid was designed, and it was helpful in conducting the field operation. The relationship between the thickness of the straightener and the incident angle at the entrance of catalyst layer was discussed.

High efficiency ethanol-diesel dual-fuel combustion: A comparison against conventional diesel combustion from low to full engine load

Comparisons between dual-fuel combustion and conventional diesel combustion (CDC) are often performed using different engine hardware setups, exhaust gas recirculation rates, as well as intake and exhaust manifold pressures. These modifications are usually made in order to curb in-cylinder pressure rise rates and meet exhaust emissions targets during the dual-fuel operation. To ensure a fair comparison, an experimental investigation into dual-fuel combustion has been carried out from low to full engine load with the same engine hardware and identical operating conditions to those of the CDC baseline. The experiments were executed on a single cylinder heavy-duty diesel engine at a constant speed of 1200 rpm and various steady-state loads between 0.3 and 2.4 MPa net indicated mean effective pressure (IMEP). Ethanol was port fuel injected while diesel was direct injected using a high pressure common rail injection system. The start of diesel injection was optimised for the maximum net indicated efficiency in both combustion modes. Varied ethanol energy fractions and different diesel injection strategies were required to control the in-cylinder pressure rise rate and achieve highly efficient and clean dual-fuel operation. In terms of performance, dual-fuel combustion attained higher net indicated efficiency than the CDC mode from 0.6 to 2.4 MPa IMEP, with a maximum value of 47.2% at 1.2 MPa IMEP. The comparison also shows the use of ethanol resulted in 26% to 90% lower nitrogen oxides (NOx) emissions than the CDC operation. At the lowest engine load of 0.3 MPa IMEP, the dual-fuel operation led to simultaneous low NOx and soot emissions at the expense of a relatively low net indicated efficiency of 38.9%. In particular, the reduction in NOx emissions introduced by the utilisation of ethanol has the potential to decrease the engine running costs via lower consumption of aqueous urea solution in the selective catalyst reduction system. Moreover, the dual-fuel combustion with a low carbon fuel such as ethanol is an effective means of decreasing the use of fossil fuel and associated greenhouse gas emissions.

A PGM-free NOx adsorber + selective catalytic reduction catalyst system (AdSCR) for trapping and reducing NOx in lean exhaust streams at low temperature

Novel AdSCR systems are able to trap and reduce NOx in lean exhausts at low temperature.

Diesel and Spark Ignition Engines Emissions and After-Treatment Control: Research and Advancements

One of the major risks mankind has encountered during recent years is, without a doubt, the anthropogenic contribution to environmental pollution [...]

An Efficient Method for Reduction of Nitroaromatic Compounds to the Corresponding Aromatic Amines with NH2NH2·H2O Catalysed by H2O2-Treated Activated Carbon

An efficient and green protocol for the reduction of nitroaromatic compounds to the corresponding amines has been developed. The reduction catalyst system includes NH2NH2·H2O and H2O2-treated activated carbon. Without adding additional metals, the H2O2-treated activated carbon could be reused for many cycles without decreasing catalytic efficiency. The aromatic amines could be obtained in good to excellent yields.

Optimization of ammonia injection grid in hybrid selective non-catalyst reduction and selective catalyst reduction system to achieve ultra-low NOx emissions

The uniformity of NH3 in the flue gas is the main factor improving the efficiency during the hybrid selective non-catalytic reduction (SNCR)-selective catalytic reduction (SCR) denitrification process. This work presents the optimized ammonia injection grid (AIG) to enhance the mixing performance and optimize concentration uniformity. A testing ammonia injected facility with a scale of 1:1 is established to experimentally simulate the NH3 mixing behavior in the tail flue gas duct employing the tracer gas. A novel injection grid with multiple inclined nozzles is proposed to replace the conventional direct-injection type. The flow field and tracer gas concentration field are studied under the three conditions with various inclined jet angles including 0°, 30° and 45°. From results, mixing enhancement between jet and crossflow for the inclined injection grid is achieved. It is also indicated that the inclined angle plays an important effect on jet rigidity and tracer gas dilution. The flow field and tracer gas mixing performances are quantitatively analyzed by using the root mean square deviation coefficient. Multiple jets with an inclined angle of 30° achieved the best mixing performance. Consequently, optimized AIG design has shown effective NOx control performance in industrial utility furnace.

A New Dynamic Injection System of Urea-Water Solution for a Vehicular Select Catalyst Reduction System

Since the Euro-ІІІ standard was adopted, the main methods to inhibit NOx production in diesel engines are exhaust gas recirculation (EGR) and select catalyst reduction (SCR). On these methods SCR offers great fuel economy, so it has received wide attention. However, there also exists a trade-off law between NOx conversion efficiency and NH3 slip under dynamic conditions. To inhibit NH3 slip with high NOx conversion efficiency, a dynamic control method for a urea water solution (UWS) injection was investigated. The variation phenomena of SCR conversion efficiency with respect to the cross-sensitivity characteristics of the NOx sensor to NH3 have been thoroughly analyzed. The methodology of “uncertain conversion efficiency curve tangent analysis” has been applied to estimate the concentration of the slipped NH3. The correction factor “φ” of UWS injection is obtained by a comparative calculation of the NOx conversion ability and subsequent NH3 slip. It also includes methods of flow compensation and flow reduction. The proposed control method has been authenticated under dynamic conditions. In low frequency dynamic experiments, this control method has accurately justified the NH3 slip process and inhibits the NH3 emission to a lower level thereby improving the conversion efficiency to a value closer to the target value. The results of European transient cycle (ETC) experiments indicate that NH3 emissions are reduced by 90.8% and the emission level of NOx is close to the Euro-Ѵ standard.

Performance evaluation of a urea-selective catalytic reduction system in a marine diesel engine

A numerical simulation of the droplet distribution at the exhaust duct for a static mixer and injection location was performed for marine selective catalyst reduction. Through experiments with this auxiliary marine urea-selective catalyst reduction system, the ammonia slip, selective catalyst reduction system pressure drop, and NOx reduction rate in accordance with the space velocity (i.e. engine load) were investigated. Under incremental and random experimental conditions, the ammonia slip of this urea-selective catalyst reduction system is below 3 ppm, which satisfies International Maritime Organization Tier III regulations.

Selective catalytic reduction catalyst system

Selective catalytic reduction catalyst system

Identification of Cross-Sensitivity of Smart NOx Sensors to Ammonia in Urea-Selective Catalyst Reduction Systems via Fast Fourier Transform

Identification of Cross-Sensitivity of Smart NOx Sensors to Ammonia in Urea-Selective Catalyst Reduction Systems via Fast Fourier Transform

Plasma Synthesis of Polymer‐Capped Dye‐Sensitised Anatase Nanopowders for Visible‐Light‐Driven Hydrogen Evolution

Visible-light-driven photocatalysis is currently attracting a great deal of attention because of its potential application in solar water splitting. However, the development of efficient and durable catalyst systems is still a challenging problem. In Ru dye-sensitised TiO(2) nanopowders, catalyst performances are found to decline as a result of poor bonding of the dye molecule to the TiO(2) surface and subsequent detachment and self-aggregation of the dye. Our strategy to improve the stability of the dye-TiO(2) interface is the encapsulation of the dye/TiO(2) assembly in an amino-group-containing polyallylamine layer anchored to TiO(2). A low-pressure pulsed microwave discharge plasma polymerization process was employed to coat a commercial anatase nanopowder with a thin polyallylamine layer to nanoconfine the adsorbed dye molecules. Electron microscopy and UV/Vis spectroscopy was carried out to characterise the resulting encapsulated nanostructures. The long-term stability of the new nanomaterial as the photoactive component of a water reduction catalyst system for H(2) evolution investigated in a slurry reactor under visible-light irradiation showed stable evolution rates over a period of several days.