Catalyzed Diesel Particulate Filter Research Articles

Effect analysis on passive and active regeneration performance of catalytic diesel particulate filters at the equilibrium point in the presence of ash layer

AbstractCatalytic diesel particulate filters (CDPF) form the main post‐processing devices for the diesel engines. Particulates trapped by CDPF can be oxidized by nitrogen dioxide (NO2) and oxygen (O2). The CDPF passive and active regeneration model on platinum‐based catalyst in the presence of ash layer, including the mass, momentum, and enthalpy balances of the gas and the solid phase, the gas diffusion, and the kinetic of the soot oxidation reaction is performed and validated by the bench test. The effects of different temperatures on CDPF passive and active regeneration at the equilibrium point are analyzed. Further, the effective analysis of ash loading and ash layer distribution on the equilibrium state is conducted. The research on CDPF passive and active regeneration at the equilibrium point in the presence of ash layer provides a theoretical basis for CDPF application.

Study of soot dynamic behavior and catalytic regeneration in diesel particulate filters

Catalytic diesel particulate filters (CDPFs) are key technologies for controlling particulate matter emissions. Nevertheless, it is challenging to experimentally observe the internal working states of the CDPF, which hinders comprehensive research on the flow, capture, and regeneration characteristics. In this study, we utilized quartet structure generation set to generate two-dimensional porous walls, lattice Boltzmann method to simulate CDPF flow and diffusion, cellular automata to simulate soot motion, and global reaction kinetics to simulate soot oxidation. The accuracy of the model is validated through flow, combustion, and pressure drop experiments. We propose a new concept of local porosity, where the porosity of a partially porous wall is used to represent the filtering parameters of that part. These findings indicate that porosity dominates filtering. A higher local porosity results in increased near-wall velocity and greater deposition of soot particles. Similarly, alterations in local porosity and deposition mutually influence each other. The velocity distribution and pressure difference at the inlet and outlet are directly influenced by the upstream velocity. Compared with velocity and porosity, particle diameter has less effect on deposition location, but more effect on deposition efficiency. Active regeneration (800 K) occurs approximately 31.17 times more quickly than passive regeneration (600 K) in the absence of a catalyst. The platinum-based catalyst significantly enhanced the soot oxidation rate by oxidizing NO to NO2, resulting in a 3.62-fold increase in passive regeneration and an estimated 1.17-fold increase in active regeneration. These findings are crucial for developing efficient CDPF systems and for reducing particulate emissions.

Highly Reactive Peroxide Species Promoted Soot Oxidation over an Ordered Macroporous Ce0.8Zr0.2O2 Integrated Catalyzed Diesel Particulate Filter.

Particulate matter, represented by soot particles, poses a significant global environmental threat, necessitating efficient control technology. Here, we innovatively designed and elaborately fabricated ordered hierarchical macroporous catalysts of Ce0.8Zr0.2O2 (OM CZO) integrated on a catalyzed diesel particulate filter (CDPF) using the self-assembly method. An oxygen-vacancy-enriched ordered macroporous Ce0.8Zr0.2O2 catalyst (VO-OM CZO) integrated CDPF was synthesized by subsequent NaBH4 reduction. The VO-OM CZO integrated CDPF exhibited a markedly enhanced soot oxidation activity compared to OM CZO and powder CZO coated CDPFs (T50: 430 vs 490 and 545 °C, respectively). The well-defined OM structure of the VO-OM CZO catalysts effectively improves the contact efficiency between soot and the catalysts. Meanwhile, oxygen vacancies trigger the formation of a large amount of highly reactive peroxide species (O22-) from molecular oxygen (O2) through electron abstraction from the three adjacent Ce3+ (3Ce3+ + Vö + O2 → 3Ce4+ + O22-), contributing to the efficient soot oxidation. This work demonstrates the fabrication of the ordered macroporous CZO integrated CDPF and reveals the importance of structure and surface engineering in soot oxidation, which sheds light on the design of highly efficient PM capture and removal devices.

Investigation of the effect of different structure parameters and operating factors on the integrated exhaust aftertreatment system for diesel engines and parameter importance analysis

With diesel emission regulations growing more stringent, it is important to study the effect of different structure parameters and operating factors on the integrated aftertreatment system consisting of diesel oxidation catalyst (DOC), catalytic diesel particulate filter (CDPF) and selective catalytic reduction (SCR) during the design and optimization of the aftertreatment system. In this paper, a simulation model capable of exploring the interaction between the aftertreatment components was developed based on some relevant reaction mechanism, and the model accuracy was verified well using the experiment data. Then the effect of different parameters on the overall performance of the aftertreatment system was analyzed qualitatively. Finally, the importance score of each parameter was determined quantitatively based on Latin Hypercubic Sampling method and Random Forests algorithm. The results showed that larger diameter or larger cell density in DOC could improve the aftertreatment performance effectively. The increase in the wall thickness of each component had a negative impact on the aftertreatment system, except for CDPF wall thickness, which improved the filtration efficiency for particular matter (PM). When total aftertreatment length was fixed, high conversion efficiencies for carbon monoxide (CO) and total hydrocarbons (THC) were distributed in the region with large DOC length ratio, and NOx conversion efficiency was affected simultaneously by the length ratio of DOC, CDPF and SCR. An increase in CDPF length ratio and a decrease in DOC and SCR length ratios could contribute to the reduction of total pressure drop. Finally, Random Forests algorithm provided a good identification of the importance score of each parameter. DOC length and diameter played a dominant role in CO and THC conversion. The aftertreatment diameter had higher effect on NOx conversion efficiency than SCR length and PM filtration efficiency was mainly affected by DOC and CDPF length. Based on these qualitative and quantitative results, a design strategy for the integrated aftertreatment system was proposed, which provided some ideas for improving aftertreatment performance.

Study on the differences between non-catalytic and catalytic oxidation of soot based on catalyst CeO2

Exploring the differences between soot non-catalytic and catalytic oxidation process is beneficial to enhance the catalyst performance and soot removal efficiency of catalytic diesel particulate filters. In this paper, the soot samples are pretreated under high temperature conditions at both non-catalytic and catalytic oxidation atmosphere to obtain target pretreated soot samples with different mass loss. Five typical oxidation stages are analyzed with corresponding soot mass loss rate of 15 %, 25 %, 50 %, 70 %, 85 %. The soot physicochemical properties including oxidation activity, porous structure, particle layer, nanostructure, graphitization and functional groups are explored; further, the correlations among these physicochemical properties are analyzed, and three levels of catalytic effect mechanism are proposed based on CeO2 catalyst. This paper helps in understanding the differences of the mechanisms between non-catalytic and catalytic oxidation of soot.

An assessment of the application of catalyst preheating prior to engine cold start to improve the filtration performance of CDPF on particulate emissions

The catalytic diesel particulate filter (CDPF) is an effective technology for reducing particle emissions. However, during engine startup, especially in cold start conditions, notable particle emissions are observed at the CDPF outlet. These emissions are attributed to combustion deterioration during startup and the low temperature of the aftertreatment catalyst. Addressing this challenge, this study investigated the effectiveness of rapidly preheating the diesel oxidation catalyst (DOC) and CDPF substrate temperatures before engine start to enhance particle removal during cold starts. Experimental results indicated that CDPF filtration efficiency during cold start was lower compared to hot start conditions, with a clean CDPF exhibiting very low efficiency due to minimal particle deposition. Substrate temperature preheating of either the DOC or CDPF was found to improve CDPF filtration efficiency for particles during cold start, albeit with a concurrent increase in emissions of particles smaller than 50 nm. Notably, a combination of a 250 °C DOC with a 22 °C CDPF yielded the most significant reduction in particle emissions, particularly for particles under 50 nm. Given that the DOC shares the same material composition as the CDPF but has a smaller volume that requires less energy for heating, preheating the DOC emerges as a more energy-efficient strategy. These findings underscore the need for more comprehensive studies on catalyst preheating to further the commercialization of technologies that effectively reduce cold start particle emissions, aligning with increasingly stringent future emission regulations.

Research on flow and heat transfer at different positions in CDPF channel based on three-dimensional thermal LBM

To explore the flow, heat transfer and oxidative regeneration mechanism of the porous media of the catalytic diesel particulate filter at the pore scale, catalytic diesel particulate filter and particulate layer structure were built using three-dimensional reconstruction technology of Micro-CT and the Quartet Structure Generation Set. A heat source term was added to the mathematical model to simulate the temperature field during the oxidative regeneration of the particulate layer. The effects of different wall structures at five different positions, air inlet velocities and particulate layer parameters on the porous media were analyzed. The results show that in the clean cordierite porous medium structures, the larger the structural porosity, the greater the average velocity at the inlet of the porous medium wall. In the porous medium wall structures loaded with particulate layers, the particulate layer has a weakening effect on the velocity field above the particulate layer porous media. As the porosity of the particulate layer decreases, the temperature rise increases. When the particulate layers are oxidized, a temperature peak is generated at the inlet of the wall porous media. As the porosity of the particulate layer decreases, the temperature peak increases during oxidative regeneration.

Multi-objective optimization study of hydrothermal aging on NOx-assisted soot catalytic combustion and secondary pollution emission in regeneration of CeO2 catalytic diesel particulate filter

The present study aimed to explore the effect of hydrothermal aging on the heterogeneous catalytic combustion process of soot in CeO2 catalytic diesel particular filter and the formation of secondary pollutants (N2O and CO).The present study was based on a fixed-bed experimental bench for NOx-assisted soot catalytic oxidation in CeO2-CDPF with different soot loading and catalyst coating amounts. A non-linear regression surrogate model and a multi-objective optimization decision approach were used to analyze the trade-off relationship between the design variables and the optimization objectives. The results showed that lower levels of soot loading (2.5 g/L), CeO2 catalyst coating amount (2.5 g/L) and higher NOx concentration (1000 ppm) in fresh catalysts were favorable for improving the performance of soot-assisted catalytic combustion and minimizing the formation of N2O and CO. However, it was observed that higher levels of catalyst coating amount (10 g/L) resulted in better soot catalytic combustion performance with lower N2O and CO emissions. Global sensitivity analysis showed a positive correlation between N2O and CO peak concentrations and peak temperatures with soot loading, but a negative correlation with catalyst loading. Over time, hydrothermal aging of CDPF caused the inhibitory effect of CeO2 catalyst on N2O to shift from negative to positive correlation, while also decreasing the synergistic performance of NOx in soot catalytic combustion.

Evolution hydrothermal aging mechanism for Ag/CeO2 catalysts in regeneration of catalytic diesel particulate filter with DFT calculation.

In order to avoid the high cost of existing precious metal catalyst like Pt, Ag/CeO2 was the most promising catalysts for mobile source soot emission control technologies, but there was a clear trade-off between hydrothermal aging resistance and catalytic oxidation performance hindered the application of this catalyst. In order to reveal the hydrothermal aging mechanism of Ag/CeO2 catalysts, the TGA (thermogravimetric analysis) experiments were investigated to reveal the mechanism of Ag modification on catalytic activity of CeO2 catalyst between fresh and hydrothermal aging and were also characterized with the related characterization experiments to in-depth research the lattice morphology and valence changes. The degradation mechanism of Ag/CeO2 catalysts in vapor with high-temperature was also explained and demonstrated based on density functional and molecular thermodynamics theories. The experimental and simulation data showed that the catalytic activity of soot combustion within Ag/CeO2 decreased more significantly after hydrothermal aging than CeO2 due to the less agglomerated, which caused by the decreased in OII/OI and Ce3+/Ce4+ compared with CeO2. As shown in density function theory (DFT) calculation, the decreased surface energy and the increased oxygen vacancy formation energy of the low Mille index surface after Ag modification led to the instability structure and the high catalytic activity. Ag modification also increased the adsorption energy and Gibbs free energy of H2O on the low Miller index surface compared to CeO2, indicating that the desorption temperature of H2O molecules in (1 1 0) and (1 0 0) was higher than (1 1 1) in CeO2 and Ag/CeO2, which led to the migration of (1 1 1) crystal surfaces to (1 1 0) and (1 0 0) in the vapor environment. These conclusions can provide a valuable addition to the regenerative application of Ce-based catalysts in diesel exhaust aftertreatment system the aerial pollution.

An experimental investigation of particulate emission characteristics of catalytic diesel particulate filters during passive regeneration

The catalytic diesel particulate filter (CDPF) can effectively reduce diesel particulate emissions, but its outlet particulate emissions increase significantly during active and passive regeneration. Understanding the particle emission characteristics and oxidation mechanism during CDPF regeneration is a prerequisite for seeking improvement measures and achieving near-zero emissions from diesel engines. This study focused on the particle emission characteristics during passive regeneration not previously detailed in the engine literature dedicated to catalytic diesel particulate filters. The commercial carbon black (Printex-U, PU) was utilized to replace diesel soot and loaded onto the CDPF substrate here. Experimental tests were conducted to investigate the effect of regeneration temperature and soot load on the CDPF response to exhaust particles during passive regeneration. The results showed that the diesel oxidation catalyst (DOC) reduced the particle number (PN) upstream of the CDPF device. In addition, the regeneration temperature and soot load altered the ratio of penetrating particles (PP), secondary particles (SP), and blown-out particles (BP), resulting in a complex particle emission profile in terms of particle concentration and size at the CDPF outlet. Moreover, the higher regeneration temperature enhanced the oxidation of the particulate matter and raised the particle number, while increasing the particle load enhanced the capture effect of incoming particles but also led to enhanced catalytic oxidation and destruction of the microstructure of the particle layer, thus increasing the discharged particle emissions.

Deterioration evaluation of cerium-based catalytic diesel particulate filter based on fuzzy grey correlation analysis

This study simulated the composite regeneration process of a Catalyzed Diesel Particulate Filter (CDPF). The degradation performance was evaluated using the maximum wall temperature as the benchmark. The orthogonal experiment design and fuzzy grey correlation analysis approach were employed to analyze the effect of various factors, including regeneration temperature, NOx mass, catalyst coating amount, SO2 concentration, oxygen concentration, and exhaust flow rate, on the degradation of the CDPF. A comprehensive analysis of the factors was conducted, yielding important insights into the key factors that can be leveraged to optimize the system. The results reveal that these six operating parameters are the primary drivers of the CDPF’s performance degradation, with the NOx mass having the greatest impact on the maximum wall temperature.

Insights into the interface of NiCo2O4 spinel /LaCoO3 perovskite nano-composite for CO and soot oxidation

In the quest for the development of thermally stable, highly active and low-cost catalysts for use in catalyzed diesel particulate filter, nano-composites are new areas of research. Therefore, we reported the easy synthesis of spinel NiCo2O4/perovskite LaCoO3 nano-composite, and its individual oxides NiCo2O4 and LaCoO3 for comparison. The detailed insights into the physio-chemical characteristics of formed NiCo2O4/ LaCoO3 nano-composite were done based on various characterization analysis such as X-ray diffraction (XRD), Fourier transform infrared (FT-IR), N2 physiosorption, scanning electron microscopy-energy dispersive spectroscopy (SEM-EDX), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). The characterization analysis of NiCo2O4/LaCoO3 revealed the successful formation of a chemical interface possessing strong interfacial interaction, resulting in desirable physicochemical characteristics such as small crystallite size, abundant mesoporosity, high specific surface area and activation of surface lattice oxygen. Owing to the desirable characteristics, the activity results over NiCo2O4/LaCoO3 nano-composite showed the excellent CO oxidation performance and high soot oxidation activity, recyclability and thermal stability. This work mainly attempts to emphasize the effectiveness of the facile, inexpensive and conventionally used precipitation method for the successful formation of highly efficient nano-composites.

In situ growth of ZnO nanorods on monolithic diesel particulate filters and supporting potassium for catalytic soot combustion

Soot particulate is one of the most important pollutants emitted from diesel engines. A monolithic wall-flow diesel particulate filter (DPF) is a commercial technology for the removal of soot via filtration and subsequent combustion with/without catalysts. Herein, in situ grown ZnO nanorods on DPFs are applied to improve both soot and potassium (K)-based catalyst dispersion efficiency and thus enhancing the activity of DPF regeneration. The pretreatment and hydrothermal synthesis procedures for the homogenously covered ZnO nanorod arrays were specifically investigated on aluminum titanate (Al2TiO5) and silicon carbide (SiC) and compared with cordierite (Mg2Al4Si5O18). Potassium carbonate (K2CO3) is further supported on these monolithic substrates with in situ grown ZnO nanorods acting as catalytic active components for soot combustion. The coexistence of in situ grown ZnO nanorods and K active species on the three monoliths leads to much better soot combustion activity than those bare monoliths. The ZnO nanorods can not only trap soot to improve the contact efficiency between soot and catalysts, but also disperse the active K species. This demonstrates a promising strategy to develop highly active catalytic DPF for diesel soot removal.

Effects of waste-cooking-oil biodiesel blends on diesel vehicle emissions and their reducing characteristics with exhaust after-treatment system

The waste-cooking-oil biodiesel is proven to be a clean alternative fuel, its effect on the vehicle emissions at different driving conditions needs further quantitative evaluation, especially with the exhaust after-treatment. The objective of this study is to quantify the effect of waste-cooking-oil biodiesel on the gaseous and particulate emissions from an urban bus at different driving conditions, and with a combination of diesel oxidation catalyst (DOC) and a catalyzed diesel particulate filter (CDPF) after-treatment. Results showed that the emissions depended on the driving conditions, vehicle acceleration and high speed increased the emissions. The biodiesel blends produced a reduction in the carbon monoxide (CO), total hydrocarbon (THC), particle number (PN) and particle mass (PM) emissions, but an increase in the carbon dioxide (CO2) and nitrogen oxide (NOx) emission, and this changing trend increased with not only the biodiesel blending ratio but also the vehicle speed and acceleration. The particle size distribution remained bimodal logarithm distribution after using the biodiesel, and more accumulation mode particles reduced compared with nucleation mode ones, increasing the proportion of nucleation mode particles. The after-treatment system composed of DOC and CDPF could reduce 58.0% of the CO and 53.1% of the THC when using B10 (10% biodiesel and 90% diesel by volume), and the reduction effect was enhanced with the increase of the biodiesel blending ratio, also with the increase of speed and acceleration. The after-treatment system reduced more than 99% of the PN and 94% of the PM, achieving excellent reduction effects, independent of fuel type and driving conditions.

Analysis of temperature and pressure characteristics in catalyzed diesel particulate filter operation for heavy-duty diesel engine

• Pressure characteristics of the soot loading process in CDPF is clarified. • Temperature characteristics of active regeneration process in CDPF is proposed. • The effect of the flow parameters on pressure and temperature are studied. • A self-defined transient cycle is used to reflect the actual road conditions. • The soot oxidation process is divided into stages I and II. Catalyzed Diesel Particulate Filter (CDPF) provides an efficient method for removing particulate matter emissions to meet stringent soot emission legislation for diesel engines. In order to clarify the temperature and pressure characteristics of CDPF during the soot loading and regeneration process, in this study, a self-defined transient cycle is used for the soot loading test and combined with 1D simulations to reveal the pressure field. In addition, the effect mechanism of initial soot loading and inlet parameters on temperature and soot characteristics was investigated through the results of regeneration experiments and 3D simulations. The results show that the initial soot loading amount and exhaust flow rate affected the pressure drop of CDPF more than that of the engine. The total pressure drop of the CDPF varied linearly with the increasing exhaust flow rate and soot loading. Among the four pressure drops, the soot layer pressure drop had the highest proportion and the most significant change. During the active regeneration of CDPF, the temperature near the CDPF outlet was the highest (TS3), and TS1 was the lowest, in the axial direction, TS4 and TS5 in the radial direction were the highest. In addition, the soot combustion process can be divided into stages I and II based on the soot oxidation speed. The larger initial soot loading, the higher inlet temperature, the faster exhaust flow rate, and greater O 2 concentration all resulted in the shorter stage I, the larger soot oxidation speed, the faster temperature rise, the larger region of high temperature in CDPF. And the inlet temperature had the greatest impact on the regeneration process, followed by initial soot loading and O 2 concentration, and the exhaust flow rate had the least impact. There is a reversed change in the propagation direction during the oxidation of soot.

Numerical study on effects of hydrothermal aging to composite regeneration in CeO2-based catalyzed diesel particulate filter

The effects of hydrothermal aging on the performance of CeO2-based catalyzed diesel particulate filter (CDPF) was numerically investigated in this study based on a zero-dimensional model using the plug flow reactor in which a chemical reaction kinetic mechanism was established and validated by the simulated gas environment experiment. The effects of regeneration temperature, O2 concentration in the ultimate emission conditions, the ratio of NO2 in NOx (α) and the ratio of NOx to soot (β) on catalyst deactivation temperature and soot oxidation rate were investigated with fresh and hydrothermal aging CeO2-based CDPF. The results show that hydrothermal aging of CeO2-based catalysts raises the regeneration temperature from 613 to 783 K and shifts the soot catalytic combustion reaction path from complete to incomplete oxidation. Soot oxidation rate of fresh catalyst first increases rapidly at 516 K and then starts to slow down gradually at 633 K, but for hydrothermal aging catalysts, are 601 K and 789 K, respectively. With O2 concentration increased from 1.5 mol/m3 to 5.5 mol/m3, the catalyst deactivation of fresh and hydrothermal aging catalyst increased from 609 K to 602 K, 791 K to 818 K, respectively. The increase in α and β leads to an increase in soot oxidation rate and a decrease in regeneration temperature. The deactivation temperature of catalyst is increased in higher α (1.0) and lower β (0.1), which the highest is 821 K. Synergistic mechanisms of NOx, regeneration temperature, and hydrothermal aging effects on soot catalytic combustion in CeO2-based CDPF are revealed deeply with the help of zero-dimensional model.

Effect of catalyst diesel particulate filter aging and catalyst loadings on particulate emission characteristics from a diesel vehicle

In this study, the effect of new and used catalyzed diesel particulate filter (CDPF) with different catalyst loadings on the particulate emissions including the particle mass (PM), particle number (PN), particle size distribution (PSD) and geometric mean diameter (GMD) from a diesel vehicle were investigated based on a heavy chassis dynamometer. Results showed that more than 97.9% of the PN and 95.4% of the PM were reduced by the CDPF, and the reduction efficiency was enhanced by the catalyst loading. After using the CDPF, the PSD transformed from bimodal to trimodal with the peak shifting towards smaller particle size, more nucleation mode particles were reduced compared with accumulation mode ones, but the reduction effect on the accumulation mode particles was more significantly influenced by the catalyst loading. Notably, the CDPF increased the accumulation mode particles proportion, producing a larger GMD. For the used CDPF, its reduction effect on the particulate emissions enhanced, especially for the PM in accumulation mode. The PSD returned to bimodal, but the peak at accumulation mode began to be higher than that at nucleation mode, illustrating that more nucleation mode particles was removed. The aging of the CDPF resulted in greater effect on the PN-based PSD than that of PM-based PSD, but the effect of catalyst loading on the PN and PM emission factors was weakened. The used CDPF further increased the GMD, and the effect of catalyst loading on the GMD was strengthened, a higher catalyst loading led to a reduction in the GMD.

Assessment of a Euro VI Step E Heavy-Duty Vehicle’s Aftertreatment System

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.

Study on Emission Characteristics and Emission Reduction Effect for Construction Machinery under Actual Operating Conditions Using a Portable Emission Measurement System (Pems)

With the acceleration of urban construction, the pollutant emission of non-road mobile machinery such as construction machinery is becoming more and more prominent. In this paper, a portable emissions measurement system (PEMS) tested the emissions of eight different types of construction machinery under actual operating conditions and was used for idling, walking, and working under the different emission reduction techniques. The results showed that the pollutant emission of construction machinery is affected by the pollutant contribution of working conditions. According to different emission reduction techniques, the diesel oxidation catalyst (DOC) can reduce carbon monoxide (CO) by 41.6–94.8% and hydrocarbon (HC) by 92.7–95.1%, catalytic diesel particulate filter (CDPF) can reduce particulate matter (PM) by 87.1–99.5%, and selective catalytic reduction (SCR) using urea as a reducing agent can reduce nitrogen oxides (NOx) by 60.3% to 80.5%. Copper-based SCR is better than vanadium-based SCR in NOx reduction. In addition, the study found that when the enhanced 3DOC + CDPF emission reduction technique is used on forklifts, DOC has a “low-temperature saturation effect”, which will reduce the emission reduction effect of CO and THC. The use of Burner + DOC + CDPF emission reduction techniques and fuel injection heating process will increase CO’s emission factors by 3.2–3.5 and 4.4–6.7 times compared with the actual operating conditions.

An experimental investigation of particle and NOx emissions for a non-road diesel engine equipped with an integrated DOC + CDPF + SCR aftertreatment system during different operations.

An integrated aftertreatment system consisting of diesel oxidation catalyst (DOC), catalytic diesel particulate filter (CDPF), and selective catalytic reduction (SCR) is an effective way of reducing both NOx and particulate matter (PM). In this paper, the effect of DOC + CDPF + SCR on NOX and particle emissions is investigated during different operations to assess applicability of this aftertreatment for meeting more rigorous non-road emissions standard. Meanwhile non-negligible issue about regeneration emission is studied. The results show that the DOC + CDPF have no significant effect on NOx but increase the NO2/NOx ratio which is correlated with load. SCR is the main NOx reduction device with average efficiency of 86.5% for steady-state operations. Meanwhile, NH3 slip is lower than 16ppm. During cold and hot non-road transient cycles (NRTCcycles), average NOx efficiencies are 56.7% and 57.8%, respectively, along with NH3 slip below 10ppm. DOC + CDPF + SCR maintain filtration efficiency over 97% and 99% for PM and particle number (PN) for either steady-state operation or NRTCcycle, but particle size distributions change. Compared with the original emissions, NOx, PM, and PN emission factors are all below non-road China-IV limit after equipping with DOC + CDPF + SCR. However, during regeneration the aftertreatment does not maintain a high filtration performance but becomes particle generator. The penetration of nuclear particles and decomposition of agglomerated particles lead to high CDPF-out PN of 1.5 × 107 #/cm3-3.5 × 107 #/cm3. During regeneration, accumulated NOx is negligible, but the PM is 121.6 and 44.5 times higher than cold and hot NRTCcycles, respectively. In summary, DOC + CDPF + SCR is excellent way to improve non-road emissions but low SCR efficiency at low-temperature and high accumulated PM during regeneration process should be further addressed.