Diesel Emission Control Research Articles

Fine-particulate Air Pollution from Diesel Emission Control and Mortality Rates in Tokyo

Evidence linking air pollution with adverse health outcomes is accumulating. However, few studies have adopted a quasi-experimental design to evaluate whether decline in air pollution from regulatory action improves public health. We evaluated the effect of a diesel emission control ordinance introduced in 2003 on mortality rates in 23 wards of the Tokyo metropolitan area, Japan, from October 2000 to September 2012, taking into account change in mortality rates in a reference population (Osaka) with a introduction of such a regulation in 2009. We obtained daily counts of all-cause and cause-specific mortality and concentrations of nitrogen dioxide (NO2) and particulate matter less than 2.5 μm in diameter (PM2.5) during the study period. We employed interrupted time-series analysis to analyze the data. Decline in NO2 during the study period was similar in the two areas, while decline in PM2.5 and the improvement in age-standardized mortality rates were greater in Tokyo's 23 wards compared with Osaka. Even after adjusting for age-standardized mortality rates in Osaka, percent changes in mortality between the first 3-year interval (October 2000 to September 2003) and the last 3-year interval (October 2009 to September 2012) were -6.0% for all causes, -11% for cardiovascular disease, -10% for ischemic heart disease, -6.2% for cerebrovascular disease, -22% for pulmonary disease, and -4.9% for lung cancer. We did not observe a decline in mortality from other causes. This quasi-experimental study in Tokyo suggests that emission control was associated with improvements in both air quality and health outcomes.

Comparing multi-objective non-evolutionary NLPQL and evolutionary genetic algorithm optimization of a DI diesel engine: DoE estimation and creating surrogate model

This study is concerned with the application of two major kinds of optimization algorithms on the baseline diesel engine in the class of evolutionary and non-evolutionary algorithms. The multi-objective genetic algorithm and non-linear programming by quadratic Lagrangian (NLPQL) method have completely different functions in optimizing and finding the global optimal design. The design variables are injection angle, half spray cone angle, inner distance of the bowl wall, and the bowl radius, while the objectives include NOx emission, spray droplet diameter, indicated mean effective pressure (IMEP), and indicated specific fuel consumption (ISFC). The restrictions were set on the objectives to distinguish between feasible designs and infeasible designs to sort those cases that cannot fulfill the demands of diesel engine designers and emission control measures. It is found that a design with deeper bowl and more encircled shape (higher swirl motion) is more suitable for NOx emission control, whereas designs with a bigger bowl radius, and closer inner wall distance of the bowl (Di) may lead to higher engine efficiency indices. Moreover, it was revealed that the NLPQL could rapidly search for the best design at Run ID 41 compared to genetic algorithm, which is able to find the global optima at last runs (ID 84). Both techniques introduce almost the same geometrical shape of the combustion chamber with a negligible contrast in the injection system.

Synergetic effect of Pd addition on catalytic behavior of monolithic platinum–manganese–alumina catalysts for diesel vehicle emission control

The advanced diesel emission control catalyst Pt–Pd–MnOx–Al2O3 has been developed on the basis of the synergetic effect of Pt with Pd and manganese oxides observed in hydrocarbon and carbon monoxide oxidation reactions. This effect allows a decrease in the total loadings of Pt and Pd down to 0.52g/L in the monolithic catalyst, providing high activity in low temperature oxidation of light hydrocarbons and high thermal stability.The catalytic activity of Pt–Pd–MnOx–Al2O3 monolithic catalysts in butane oxidation and DIESEL tests depends on the Pt and Pd precursors, their individual loadings and their ratio (Pt/Pd). For a selected Pt precursor at its content 0.17g/L, the catalytic performance of Pt–Pd–MnOx–Al2O3 catalyst improves with an increase in Pd loading from 0 to 0.35g/L and is nearly constant at a higher Pd loading (0.70g/L). The most active monolithic Pt–Pd–MnOx–Al2O3 catalyst is prepared by using platinum-dinitrodiamine and palladium nitrate solutions as noble metal precursors.The catalytic activity in light hydrocarbon oxidation is shown to correlate with the RedOx properties of PdPt–MnOx–Al2O3 catalysts and the Pt–Pd particle size. The non-additive increase in the catalytic activity of bimetallic catalyst is suggested to connect with a formation of nanoscale PdO–PtOx particles on the surface of Mn3O4 and a modification of alumina structure by Mn3+ and PtPd clusters.

Chemical deactivation of commercial vanadium SCR catalysts in diesel emission control application

Irreversible chemical deactivation of state-of-the-art vanadium selective catalytic reduction (SCR) catalysts was investigated using an aftertreatment system from a heavy-duty diesel vehicle for general haulage application. Elemental analysis revealed that Field returned vanadium SCR catalysts had higher phosphorous and zinc concentrations than those from a fresh catalyst. Phosphorous concentration dropped significantly from catalyst inlet to outlet, while zinc concentration remained almost constant. Broadened infrared intensity from V5+O and W6+O bonds were observed from contaminated vanadium SCR samples. Anatase phases and crystallite size remained unchanged in the presence of chemical contaminants.Chemical contamination monotonically reduced NH3 storage capability but non-linearly modified acid site distribution and oxidation activity, causing differences in NOx reduction behaviors. Low chemical contamination on vanadium SCR catalyst reduced NOx conversion below 450°C due to the decrease in NH3 storage capacity and oxidation activity. NOx conversion over a sample with high phosphorus concentration was lowered by the weakened NH3 storage capacity below 350°C and the enhanced parasitic NH3 oxidation above 400°C. High levels of phosphorus increased low-temperature NOx conversion compared to low levels of phosphorus due to increase in oxidation capability.

A Pilot-Scale Experiment for Total Marine Diesel Emission Control Using Ozone Injection and Nonthermal Plasma Reduction

Due to the fact that it is difficult to fulfill the recent stringent regulations governing marine diesel engine emission by means of combustion improvement alone, an effective aftertreatment technology is required to achieve the efficient simultaneous removal of $\hbox{NO}_{\rm x} $ and particulate matter (PM) . In the present study, we designed and investigated an effective aftertreatment system that employs a combination of ozone injection and nonthermal plasma (NTP) reduction for a marine diesel engine. The proposed technology offers the advantage of not requiring precious-metal catalysts and harmful heavy-metal catalysts as well as urea solution. In this aftertreatment system, PM in the exhaust gas is first captured by a ceramic diesel particulate filter. Subsequently, the deposited PM is oxidized and removed by NTP-induced ozone injection. After the PM treatment, $\hbox{NO}_{\rm x} $ in the exhaust gas is treated by adsorption followed by NTP-combined desorption and reduction processes. These processes are repeated periodically, and total emission control is achieved. Since the deposited PM and the desorbed $\hbox{NO}_{\rm x} $ are treated at a high-concentration state by ozone and oxygen-lean NTP, a higher performance for total marine diesel emission control is recorded. The maximum efficiencies of $\hbox{NO}_{\rm x} $ and PM reduction were 94% and 95%, respectively.

NO oxidation on catalyzed soot filters

In addition to its filtration function, a catalyzed soot filter (CSF) also plays a variety of catalytic roles in modern diesel emission control systems. This paper focuses on NO oxidation on CSF for passive filter regeneration and for optimizing the performance of a downstream SCR catalyst. Using a Pt-catalyzed CSF loaded with diesel soot, we conducted a filter regeneration experiment with NO2 and found that soot oxidation started within the filter walls then extended to the soot cake. The NO2 used to oxidize the soot can be continuously regenerated on the filter after it is consumed, i.e. multiple NO turnovers. By inserting a capillary sampling probe into an inlet channel of a soot-free Pt-CSF, we demonstrated that NO2 generated within the filter walls can diffuse back to the inlet channels against the bulk gas flow, which makes the passive regeneration of the soot cake possible. For CSF-catalyzed NO oxidation in a SCR system, we found a large variability in NO conversion on a Pt-CSF resulting from different aging conditions. A Pt/Pd-CSF can reduce the NO conversion variability to a degree. High-temperature calcination of the supported Pt/Pd powder, before the slurry process, can further reduce this variability.

A novel cost-effective robust approach for selective catalytic reduction state estimations using dual nitrogen oxide sensors

Urea-based selective catalytic reduction systems have become a promising technique in controlling nitrogen oxide emissions from diesel engines in the past decade. One of the continuing issues is the cross-sensitivity characteristics of the current nitrogen oxide sensors to ammonia in the exhaust, which makes nitrogen oxide sensor readings inaccurate in the presence of ammonia. Although prototype ammonia sensors for mobile selective catalytic reduction applications have been introduced for diesel emission control in the past few years, ammonia sensors are still too expensive to be available for mass-produced diesel engines and selective catalytic reduction systems. In order to address these issues, in this paper, a novel, cost-effective, and robust approach is proposed for estimating the key selective catalytic reduction states including the nitric oxide concentration, the nitrogen dioxide concentration, the ammonia concentration, and the ammonia surface coverage ratio, by utilizing two post-selective-catalytic-reduction nitrogen oxide sensors with different ammonia cross-sensitivity factors. Experimental verification results show that the proposed approach has the potential for precisely estimating the four selective catalytic reduction states. Such a novel approach can be instrumental in reducing the cost of selective catalytic reduction diagnosis, selective catalytic reduction estimation, and advanced selective catalytic reduction controls.

NOx storage-reduction (NSR) catalysts for diesel emissions control: Toward the understanding of sulfur poisoning mechanism

NOx storage-reduction (NSR) catalysts for diesel emissions control: Toward the understanding of sulfur poisoning mechanism

Integrated Diesel Engine Emission Control Using Plasma-Combined Hybrid System

Innovative diesel particulate (PM) collection and NOx reduction technology were developed using plasma-combined systems over the years. As for PM control, the electrohydrodynamically assisted electrostatic precipitator (EHD ESP) to collect low resistive diesel PM and the plasma ESP to collect and incinerate PM were developed. As for NOx reduction systems, NOx concentration, followed by nitrogen plasma, was developed without using catalysts or ammonia used for selective catalytic reduction. The integrated diesel engine emission component reduction system consists of EHD ESP, plasma ESP, NOx concentration followed by nitrogen plasma, reactive species injection for NOx and PM reduction and regeneration, and a NOx recirculation (EGR) system. Each component technology was evaluated and optimized to establish the state-of-the-art integrated diesel emission control. The integrated plasma-combined hybrid system is extremely economical and practical and leads to zero emission systems.

Experimental study of hexagonal and square diesel particulate filters under controlled and uncontrolled catalyzed regeneration

Although diesel engines have high thermal efficiency, large amounts of PM (particulate matter) including soot are emitted. A wall-flow DPF (diesel particulate filter) is one of the most important technologies for diesel emission control. However, the soot accumulation inside the DPF causes an increase of pressure loss. Then, the accumulated diesel soot needs to be burned, which is called a filer regeneration process. In this study, we have investigated the soot combustion on bare and catalyzed DPFs under controlled and uncontrolled regeneration. Two types of DPFs with conventional square and hexagonal cells were used. Results show that, in comparison with the bare DPF, the regeneration efficiency of the catalyzed DPF is clearly higher, indicating a marked effect of catalysts. Independent of regeneration temperature, a greater increase in the regeneration efficiency of the catalyzed DPF was confirmed under controlled regeneration. On the other hand, under uncontrolled regeneration, the maximum temperature of the catalyzed DPF is higher than that of the bare DPF, and it is reached shorter times. Interestingly, by comparing the conventional square cell DPF, the soot oxidation of the hexagonal cell DPF is promoted under controlled and uncontrolled regeneration.

Simultaneous Reduction of Particulate Matter and NOx Emissions Using 4-Way Catalyzed Filtration Systems

The next generation of diesel emission control devices includes 4-way catalyzed filtration systems (4WCFS) consisting of both NOx and diesel particulate matter (DPM) control. A methodology was developed to simultaneously evaluate the NOx and DPM control performance of miniature 4WCFS made from acicular mullite, an advanced ceramic material (ACM), that were challenged with diesel exhaust. The impact of catalyst loading and substrate porosity on catalytic performance of the NOx trap was evaluated. Simultaneously with NOx measurements, the real-time solid particle filtration performance of catalyst-coated standard and high porosity filters was determined for steady-state and regenerative conditions. The use of high porosity ACM 4-way catalyzed filtration systems reduced NOx by 99% and solid and total particulate matter by 95% when averaged over 10 regeneration cycles. A "regeneration cycle" refers to an oxidizing ("lean") exhaust condition followed by a reducing ("rich") exhaust condition resulting in NOx storage and NOx reduction (i.e., trap "regeneration"), respectively. Standard porosity ACM 4-way catalyzed filtration systems reduced NOx by 60-75% and exhibited 99.9% filtration efficiency. The rich/lean cycling used to regenerate the filter had almost no impact on solid particle filtration efficiency but impacted NOx control. Cycling resulted in the formation of very low concentrations of semivolatile nucleation mode particles for some 4WCFS formulations. Overall, 4WCFS show promise for significantly reducing diesel emissions into the atmosphere in a single control device.

Performance and emission characteristics of a DI diesel engine with a nanofuel additive

The emission norms on internal combustion engine are becoming more and more stringent with a view to improve the ambient air quality. Emissions of Particulate Matter and Oxides of Nitrogen are the focus of today’s diesel emission control technologies. Nanometal oxide additives are reported to be effective in lowering diesel emissions. The diesel fuel formulation along with engine development can achieve clean combustion of the diesel fuel. The study is based on the effect of nanometal oxide additives like manganese oxide and copper oxide to diesel fuel. Sol–gel method was adopted for preparation for nanometal oxide additives. Metal oxide additive are doped with diesel fuel. Scanning Electron Microscope (SEM) images confirmed the presence of nanoparticle in the metal oxide additive. The changes in diesel fuel properties (viscosity, flash point and fire point) due to introduction of nanometal oxide additive were observed. The diesel fuel with nanometal oxide additive presented a marginal increase in performance. Exhaust emissions for the diesel fuel with nanometal oxide additive showed significant decrease in levels of pollutants emission.

LNT + in situ SCR catalyst system for diesel emissions control

An overview is presented of laboratory and vehicle studies conducted at Ford Motor Company on the LNT+in situ SCR catalyst approach to diesel emissions control. Specifically, the paper focuses on results obtained with so-called “2nd-generation” systems developed by Ford's catalyst suppliers since 2007–2008. These systems are characterized by improvements in durability, performance and cost relative to their predecessors. Key features of the 2nd-generation LNT+in situ SCR technology include: (1) lower desulfation temperatures of the LNT, (2) lower LNT platinum group metal (PGM) content than required for LNT-only systems, (3) advanced SCR catalysts of the types used in commercial zeolite-based SCR applications, (4) synergetic coupling of the LNT and SCR catalyst performance to maintain high efficiency after aging, (5) a non-ammonia NOx reduction mechanism over the SCR catalyst in addition to the standard mechanism based on ammonia storage, and (6) improved hydrocarbon oxidation efficiency owing to the SCR catalyst. Taken together, these advances improve the prospect of meeting future emission regulations on light-duty diesel vehicles, but not without considerable challenge to both the aftertreatment system and control strategy for achieving simultaneous low NOx and non-methane hydrocarbon emissions while minimizing fuel consumption.

Diesel vehicle emission and death rates in Tokyo, Japan: A natural experiment

Evidence linking air pollution with adverse cardiopulmonary outcomes is accumulating. However, few studies have been conducted to evaluate whether vehicle emission control improves public health. We thus evaluated the effect of a diesel emission control law on mortality rates in 23 wards of Tokyo metropolitan area, Japan. We obtained daily counts of mortality and concentrations of nitrogen dioxide (NO 2) and particulate matter less than 2.5 μm in diameter (PM 2.5) from April 2003 to December 2008. Time-series and interrupted time-series analysis were employed to analyze the data in two periods: prior to the introduction of tighter restrictions (April 2003 to March 2006) and after the enforcement (April 2006 to December 2008). Concentrations of air pollutants gradually decreased during the study period: from 36.3 ppb (NO 2) and 22.8 μg/m 3 (PM 2.5) to 32.1 ppb and 20.3 μg/m 3, respectively. Air pollutants were positively associated with circulatory and pulmonary disease mortality, especially cerebrovascular disease. Each same-day PM 2.5 increase of 10 μg/m 3 was associated with a 1.3% increase in cerebrovascular mortality rate (95% confidence interval: 0.2–2.4). Rate ratios were attenuated after the enforcement in most of the outcomes, probably due to reduced toxicity of the pollutants. In the crude interrupted time-series analysis, reductions of standardized mortality rates after the enforcement were the greatest in high traffic areas. Even after adjustment of longer-time trend, mortality rate from cerebrovascular disease was reduced by 8.50% (p < .001) with dose–response relationship. However, the declines in other cause-specific mortality became equivocal. This natural experiment in Tokyo suggests that emission controls improved air quality. Although suggestive, further data are needed to conclusively demonstrate an impact on mortality rates.

An Evaluation of Particle Size Distributions and Particle Number-Based Reductions from Various PM Emission Control Technologies

An Evaluation of Particle Size Distributions and Particle Number-Based Reductions from Various PM Emission Control Technologies

Laboratory and Vehicle Demonstration of “2nd-Generation” LNT + in-situ SCR Diesel Emission Control Systems

Laboratory and Vehicle Demonstration of “2nd-Generation” LNT + in-situ SCR Diesel Emission Control Systems

Impact of Biodiesel Impurities on the Performance and Durability of DOC, DPF and SCR Technologies

It is estimated that operating continuously on a B20 fuel containing the current allowable ASTM specification limits for metal impurities in biodiesel could result in a doubling of ash exposure relative to lube-oil derived ash. The purpose of this study was to determine if a fuel containing metals at the ASTM limits could cause adverse impacts on the performance and durability of diesel emission control systems. An accelerated durability test method was developed to determine the potential impact of these biodiesel impurities. The test program included engine testing with multiple DPF substrate types as well as DOC and SCR catalysts. The results showed no significant degradation in the thermo-mechanical properties of cordierite, aluminum titanate, or silicon carbide DPFs after exposure to 150,000 mile equivalent biodiesel ash and thermal aging. However, exposure of a cordierite DPF to 435,000 mile equivalent aging resulted in a 69% decrease in the thermal shock resistance parameter. It is estimated that the additional ash from 150,000 miles of biodiesel use would also result in a moderate increases in exhaust backpressure for a DPF. A decrease in DOC activity was seen after exposure to 150,000 mile equivalent aging, resulting in higher HC slip and a reduction inmore » NO{sub 2} formation. The metal-zeolite SCR catalyst experienced a slight loss in activity after exposure to 435,000 mile equivalent aging. This catalyst, placed downstream of the DPF, showed a 5% reduction in overall NOx conversion activity over the HDDT test cycle.« less

Dynamic Methods in Catalytic Reaction Engineering: Applications to the Investigation of the NH3 Selective Catalytic Reduction Reactions for Diesel Emission Control

For the case of the NH3 selective catalytic reduction (NH3-SCR) reactions over V-based and metal-exchanged zeolite catalysts, we have used step response and temperature-programmed experiments in a fixed-bed flow microreactor in order to accomplish the following. (i) Identify the adspecies and evaluate their storage capacities: it was found that, in addition to ammonia, NO2 as well is adsorbed in comparable amounts onto SCR catalysts in the form of nitrites and nitrates. (ii) Investigate the individual steps of mechanistic schemes: the key role of surface nitrates in the NO2-related SCR chemistry was demonstrated by dedicated transient experiments. (iii) Discriminate rival mechanistic hypotheses: the differences in the temporal evolutions of NO and NO2 during transient runs unambiguously indicated that they participate in different steps of the fast SCR mechanism. (iv) Analyze the red-ox features of the catalytic mechanism: specifically designed transient tests highlighted the superior efficiency of surface nitrates in reoxidizing the V-related redox sites. (v) Evaluate surface kinetics: chemically consistent transient kinetic models were developed from systematic sets of transient runs and applied to design and optimization of commercial SCR converters for vehicles. The results of the overall SCR investigation prove that transient response techniques can yield a superior level of mechanistic and kinetic information under process relevant conditions with a limited experimental effort.

Diesel emission control system using combined process of nonthermal plasma and exhaust gas components' recirculation

A NO x aftertreatment system, using nonthermal plasma (NTP) reduction and exhaust gas components' recirculation, is investigated. A pilot-scale system is applied to a stationary diesel engine. In this system, NO x is first removed by adsorption, and subsequently, the adsorbent is regenerated by thermal desorption. NO x desorbed is reduced by using nitrogen NTP. Moreover, NO x , CO 2, and water vapor recirculated into the engine intake reduce NO x . In this study, approximately 57% of the NO x of the exhaust (NO x : 240–325 ppm, flow rate = 300 NL/min) can be continuously treated for 58 h. A system energy efficiency of 120 g (NO 2)/kWh is obtained.

Diesel Emission Control in Review

Diesel Emission Control in Review