Search

Gaseous air pollutants emitted primarily by anthropogenic sources form secondary products through photochemical reactions, complicating the regulatory analysis of anthropogenic emissions in the atmosphere. We used an environmental chassis dynamometer and a photochemical smog chamber to conduct a parameter sensitivity experiment to investigate the formation of secondary products from a gasoline passenger car. To simulate the mitigation of ammonia emissions from gasoline vehicle exhausts assuming future emission controls and to allow photochemical oxidation and aging of the vehicle exhaust, ammonia was selectively removed by a series of five denuders installed between the vehicle and photochemical smog chamber. Overall, there were no differences in the formation of secondary organic aerosols and ozone with or without ammonia mitigation. However, the potential for ammonium nitrate particle formation was significantly reduced with ammonia mitigation. In addition, ammonia mitigation resulted in increased aerosol acidity due to nitric acid in the gas phase not being neutralized by ammonia and condensing onto the liquid particle phase, indicating a potentially important secondary effect associated with ammonia mitigation. Thus, we provide new insights into the effects of ammonia mitigation on secondary emissions from gasoline vehicle exhaust and into a potentially useful experimental approach for determining primary and secondary emissions. [ABSTRACT FROM AUTHOR]

The project aims to address the critical issue of urban air pollution caused by vehicular emissions. By integrating Machine Learning (ML) and Internet of Things (IoT) technologies, this project seeks to develop a real-time monitoring and control system to mitigate vehicular pollution. IoT sensors will be deployed on vehicles and in strategic urban locations to collect real-time data on pollutants such as nitrogen oxides (NOx), carbon monoxide (CO), and particulate matter (PM). This data will be analyzed using advanced ML algorithms to identify patterns, predict pollution levels, and recommend actionable measures to reduce emissions. The project will also incorporate engine model and fuel quality data to provide a comprehensive analysis of emission and traffic-related pollution. The expected outcome is an intelligent, data-driven system capable of providing timely insights and interventions, thereby contributing to cleaner air and healthier urban environments. This approach not only enhances pollution monitoring and control but also supports sustainable urban planning and public health initiatives. [ABSTRACT FROM AUTHOR]

This study investigated the effects of exhaust gas recirculation (EGR) on emission and efficiency in a hydrogen direct injection spark ignition engine. EGR was supplied as the low-pressure (LP)-EGR system by controlling EGR valve from zero to 18.7% in terms of mass fraction. The result showed that EGR effect on nitrogen oxides (NOx) reduction became enlarged as higher engine speed due to increasing residual gas fraction. Also, under the same excessive air ratio (λ:2.2), EGR addition made NOx reduction from 89.9 to 98.7 % as varying engine speed. As NOx limit was low, the maximum brake torque was also reduced. However, by using appropriate EGR, NOx margin could be converted to increasing brake torque under the same NOx concentration level from 1.9% to 18.2% as varying engine speeds. From this result, to achieve the maximum output when reaching the turbocharger's limit in a hydrogen engine and effectively reduce nitrogen oxide emissions, it is not only dependent on lean combustion but also effective to incorporate approximately 20% EGR into the operating strategy. [ABSTRACT FROM AUTHOR]

Based on the principle of the rich-burn/quench/lean-burn (RQL) technology, a low emission combustion chamber for gas turbine was designed. The effects of different heights of quenching structure and distribution ratios of the air flow on the flow field, temperature field, and pollutant formation characteristics of combustion chamber were studied under the premise of keeping the inlet parameters of combustion chamber unchanged. The results show that the height of quenching structure and the proportion of air distribution are important parameters affecting the combustion performance of the combustion chamber. With the decrease of the height of quenching structure, the NOx emission increases at the exit of the combustion chamber. The NOx emission from combustion chamber outlet first decreases and then increases with the decrease of the proportion of air mass flow from the main combustion hole to the fired air mass flow in oil-rich areas, and an optimal proportion of air mass flow makes the NOx minimum. The production of thermal NOx is directly related to the size of the region with a temperature higher than 1 900 K and the maximum gas temperature. The designed combustion chamber has a minimum NOx emission of less than 35 mg/m3 under the studied working conditions, which achieves the emission standard of a low pollution combustion chamber.

Urban areas, characterized by dense anthropogenic activities, are among the primary sources of nitrogen oxides (NOx), impacting global atmospheric conditions and human health. Satellite observations, renowned for their continuity and global coverage, have emerged as an effective means to quantify pollutant emissions. Previous bottom-up emission inventories exhibit considerable discrepancies and lack a comprehensive and reliable database. To develop a high-precision emission inventory for individual cities, this study utilizes high-resolution single-pass observations from the TROPOspheric Monitoring Instrument (TROPOMI) on the Sentinel-5 Precursor satellite to quantify the emission rates of NOx. The Exponentially Modified Gaussian (EMG) model is validated for estimating NOx emission strength using real plumes observed in satellite single-pass observations, demonstrating good consistency with existing inventories. Further analysis based on the results reveals the existence of a weekend effect and seasonal variations in NOx emissions for the majority of the studied cities. [ABSTRACT FROM AUTHOR]

The motivation for conducting this research stems from the increasingly applied manipulations of emission control systems (ECSs), especially those in diesel passenger cars (PCs). The study aimed to investigate the influence of manipulations of exhaust gas recirculation (EGR) valves and a diesel exhaust fluid (DEF)-dosing system on the nitrogen oxide (NOX) emissions of a Euro 6 diesel vehicle and, through the quantification of vehicles with manipulated ECSs, estimate the emissions of Euro 6 diesel PCs. Portable emissions measurement system (PEMS) measurements were performed on a Euro 6 diesel vehicle at a constant speed and on real driving emission (RDE) routes. The speed-dependent functions of the NOX hot emission factor (EF) were calculated for seven different scenarios. The results showed that the NOX EFs for the worst-case scenarios were more than two orders of magnitude higher than those where all ECSs were active. Applying the calculated EFs and the survey answers on the percentage of manipulated PCs to the Croatian Euro 6 diesel PC fleet, the results showed that the emission levels were up to 46.3% higher than the emissions calculated by the official computer program COPERT v5.6.5, with a tendency towards significantly higher values. The main conclusion is that vehicle manufacturers, policymakers, and the general public need to be informed about the enormous damage that in-use vehicles with manipulated ECSs cause to the environment and human health, in order to prevent such actions. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Shanghai Jiao Tong University (1006-2467) is the property of Journal of Shanghai Jiao Tong University Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Gaseous air pollutants emitted primarily by anthropogenic sources form secondary products through photochemical reactions, complicating the regulatory analysis of anthropogenic emissions in the atmosphere. We used an environmental chassis dynamometer and a photochemical smog chamber to conduct a parameter sensitivity experiment to investigate the formation of secondary products from a gasoline passenger car. To simulate the mitigation of ammonia emissions from gasoline vehicle exhausts assuming future emission controls and to allow photochemical oxidation and aging of the vehicle exhaust, ammonia was selectively removed by a series of five denuders installed between the vehicle and photochemical smog chamber. Overall, there were no differences in the formation of secondary organic aerosols and ozone with or without ammonia mitigation. However, the potential for ammonium nitrate particle formation was significantly reduced with ammonia mitigation. In addition, ammonia mitigation resulted in increased aerosol acidity due to nitric acid in the gas phase not being neutralized by ammonia and condensing onto the liquid particle phase, indicating a potentially important secondary effect associated with ammonia mitigation. Thus, we provide new insights into the effects of ammonia mitigation on secondary emissions from gasoline vehicle exhaust and into a potentially useful experimental approach for determining primary and secondary emissions.

Ag/γ‐Al2O3 is an effective catalyst for the selective reduction of NOx (SCR) using propylene as a reducing agent. The catalyst performance is greatly influenced by the synthesis procedure. Various methods for synthesis of Ag/γ‐Al2O3 are analyzed, and their performance is examined via packed bed reactor experiments in this work. An optimal one‐pot synthesis method, single‐step sol–gel (SSG) synthesis, is explored systematically. The SSG‐synthesized catalyst shows better performance than those prepared via wet impregnation. The influence of synthesis conditions, specifically pH, on the textural and morphological properties of the SSG‐synthesized Ag/γ‐Al2O3, and therefore the activity for hydrocarbon‐based SCR in a packed‐bed reactor, are analyzed using experiments and simulations. The optimized catalyst demonstrates excellent performance (90% NOx conversion) for NOx reduction under nominal operating conditions with a wide activity temperature window (300–600°C). The catalyst shows good time‐on‐stream performance and is effective at higher inlet oxygen concentrations and space velocities. A global kinetic model, which uses synthesis‐pH‐dependent parameters, is proposed, and its ability to predict the activities of these catalysts is validated. [ABSTRACT FROM AUTHOR]

This paper provides an overview of the various sources of air pollution and their impact on the environment and human health, distinguishing between natural and anthropogenic (man-made) sources. The study assessed the environmental impact of these sources – the overall level of air pollution, taking into account the predominant anthropo-genic source, such as emissions from vehicles and industrial activities. The important role of geographic information systems (GIS) in monitoring air pollution, performing spatial data analysis, and identifying pollution hotspots is emphasized. This method proposes to analyze the impact of the air quality result on public health and the environment. The main focus of the study is on the predominant pollutants in the atmosphere such as particulate matter (PM), nitrogen oxides (NOx), and sulfur dioxide (SO2). The object of the study was the Old Town of the city of Vilnius. A calculation model was created in the MatLab environment to determine the pollution. The results reveal trends in environmental indicators. In the Old Town, decreasing pollution levels of PM10 and CO are observed, and NO2 remained relatively constant from 2020 the month of January until 2022 December. The primary importance of environmental monitoring depends on government regulation, technological advancements, and public participation to effectively reduce air pollution and protect the environment. Article in English. Oro taršos šaltiniai ir jų poveikis aplinkai Santrauka Šiame darbe pateikiama įvairių oro taršos šaltinių ir jų poveikio aplinkai ir žmonių sveikatai apžvalga, išskiriant natūralius ir antropogeninius (žmogaus sukurtus) šaltinius. Tyrime įvertinta šių šaltinių įtaka aplinkai – bendras oro taršos lygis, atsižvelgiant į vyraujantį antropogeninį šaltinį, pvz., transporto priemonių išmetamus teršalus ir pramoninės veiklos atliekas. Pabrėžtas svarbus geografinės informacijos sistemų (GIS) vaidmuo stebint oro taršą, atliekant duomenų erdvinę analizę ir nustatant taršos židinius. Šiuo metodu siūloma analizuoti oro kokybės rezultato poveikį visuomenės sveikatai ir aplinkai. Atliekant tyrimą pagrindinis dėmesys skirtas vyraujantiems atmosferoje teršalams, tokiems kaip kietosios dalelės (PM), azoto oksidai (NOx) ir sieros dioksidas (SO2). Tyrimo objektu pasirinktas Vilniaus miesto senamiestis, taršai nustatyti sudarytas skaičiavimo modelis MatLab programos aplinkoje. Rezultatai atskleidžia aplinkosaugos rodiklių tendencijas. Senamiestyje pastebimas mažėjantis PM10 ir CO taršos lygis, o NO2 kiekis nuo 2020 m. sausio mėn. iki 2022 m. gruodžio mėn. išliko gana pastovus. Aplinkos stebėsenos svarba labiausiai priklauso nuo vyriausybės reguliavimo, technologijų pažangos ir visuomenės dalyvavimo siekiant veiksmingai sumažinti oro taršą ir apsaugoti aplinką. Reikšminiai žodžiai: oro tarša, antropogeniniai šaltiniai, kietosios dalelės (PM), azoto oksidas (NOx), sieros dioksidas (SO2), ozonas (O₃), geografinės informacinės sistemos (GIS).

The Michigan–Ontario Ozone Source Experiment (MOOSE) is an international air quality field study that took place at the US–Canada Border region in the ozone seasons of 2021 and 2022. MOOSE addressed binational air quality issues stemming from lake breeze phenomena and transboundary transport, as well as local emissions in southeast Michigan and southern Ontario. State-of-the-art scientific techniques applied during MOOSE included the use of multiple advanced mobile laboratories equipped with real-time instrumentation; high-resolution meteorological and air quality models at regional, urban, and neighborhood scales; daily real-time meteorological and air quality forecasts; ground-based and airborne remote sensing; instrumented Unmanned Aerial Vehicles (UAVs); isotopic measurements of reactive nitrogen species; chemical fingerprinting; and fine-scale inverse modeling of emission sources. Major results include characterization of southeast Michigan as VOC-limited for local ozone formation; discovery of significant and unaccounted formaldehyde emissions from industrial sources; quantification of methane emissions from landfills and leaking natural gas pipelines; evaluation of solvent emission impacts on local and regional ozone; characterization of the sources of reactive nitrogen and PM2.5; and improvements to modeling practices for meteorological, receptor, and chemical transport models. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Urban areas, characterized by dense anthropogenic activities, are among the primary sources of nitrogen oxides (NOx), impacting global atmospheric conditions and human health. Satellite observations, renowned for their continuity and global coverage, have emerged as an effective means to quantify pollutant emissions. Previous bottom-up emission inventories exhibit considerable discrepancies and lack a comprehensive and reliable database. To develop a high-precision emission inventory for individual cities, this study utilizes high-resolution single-pass observations from the TROPOspheric Monitoring Instrument (TROPOMI) on the Sentinel-5 Precursor satellite to quantify the emission rates of NOx. The Exponentially Modified Gaussian (EMG) model is validated for estimating NOx emission strength using real plumes observed in satellite single-pass observations, demonstrating good consistency with existing inventories. Further analysis based on the results reveals the existence of a weekend effect and seasonal variations in NOx emissions for the majority of the studied cities.

The waste-heat-recovery boiler with water injection (HR-B/W) applies the heat exchange between the intake air and exhaust gas with the water injection into the intake air. Previous theoretical studies have discussed that the HR-B/W would increase the thermal efficiency of the boiler by the active heat exchange between the intake air and exhaust gas. It has also been discussed that the increased fraction of water vapor in the air would reduce the flame temperature which in turn decreases the NOx emission. However, the potential performance of the HR-B/W has not been validated through practical boiler tests by considering the evaporation characteristics of the injected water, which plays a critical role in the performance of the HR-B/W. In this study the effects of water injection into the intake air on the thermal efficiency and pollutant emissions of the waste-heat-recovery boiler are investigated using a commercial 24 kW condensing boiler in full load condition. Thermodynamic analysis is performed to evaluate the adequate amount of water injection and trace the physical properties in the boiler upon the water injection amount and evaporation characteristics. The boiler test results showed water injection can increase thermal efficiency to 4.4% point and reduce NOx and CO emissions by 69% and 33% respectively compared to those without water injection. These advantages can be further enhanced if the atomization and evaporation performance of injected water is improved.

A portable emission measurement system (PEMS) is expensive and involves complex experimental processes for performing real driving emission (RDE) tests. An appropriate sensor-based emission measurement system (SEMS) must be developed to conduct the RDE test because SEMS has inexpensive and simple. To analyze the correlation between PEMS and SEMS, they are installed on six diesel vehicles, and a RDE test is performed on them. The applicability of the SEMS to the RDE test is estimated by comparing and analyzing real driving NOx emissions obtained from both the PEMS and SEMS. The results of laboratory and RDE tests confirm that the SEMS is applicable to RDE tests. Various correlation tests between the PEMS and SEMS show that the latter can be effectively applied to RDE tests; however, the NOx sensing limit must be improved. [ABSTRACT FROM AUTHOR]

A series of the CeO2–WO3/TiO2 catalysts doping polyethylene oxide (PEO) were synthesized by coprecipitation method and applied to selective catalytic reduction of NOx with NH3. The PEO doping catalysts showed better low-temperature activity, which demonstrated a prominent wide operation window ranging from 220 to 526 °C. A series of characterization methods were performed to demonstrate the influence of PEO addition on the internal structure, physical and chemical properties and catalytic reaction mechanism for the CeO2–WO3/TiO2 catalysts. More importantly, the addition of PEO could significantly modify and optimize the pore structure of catalysts, meanwhile, it was verified that the addition of PEO can enhance the content of Ce3+, adsorbed oxygen and the Brönsted and Lewis acid sites on the catalyst surface, thereby affecting the redox abilities, nitrogen oxides and ammonia adsorption capacity of catalysts. [ABSTRACT FROM AUTHOR]

A series of the CeO2–WO3/TiO2 catalysts doping polyethylene oxide (PEO) were synthesized by coprecipitation method and applied to selective catalytic reduction of NOx with NH3. The PEO doping catalysts showed better low-temperature activity, which demonstrated a prominent wide operation window ranging from 220 to 526 °C. A series of characterization methods were performed to demonstrate the influence of PEO addition on the internal structure, physical and chemical properties and catalytic reaction mechanism for the CeO2–WO3/TiO2 catalysts. More importantly, the addition of PEO could significantly modify and optimize the pore structure of catalysts, meanwhile, it was verified that the addition of PEO can enhance the content of Ce3+, adsorbed oxygen and the Brönsted and Lewis acid sites on the catalyst surface, thereby affecting the redox abilities, nitrogen oxides and ammonia adsorption capacity of catalysts. [ABSTRACT FROM AUTHOR]

Increasingly stringent regulation towards nitrogen oxides (NOx) emission is foreseen across the world to mitigate their detrimental effects on environment and human health. Selective catalytic reduction (SCR) of NOx with NH3 is regarded as the most efficient technology for NOx abatement in both mobile and stationary sources. As the state-of-art SCR catalyst, transition metals supported on small-pore zeolites, especially Cu on chabazite SSZ-13 (Cu-SSZ-13), have been successfully applied to NOx abatement in road transport. Their application can be expanded to stationary sources due to the gradual phase-out of petrol/diesel vehicles worldwide between 2030 and 2035. Accordingly, the stability and activity of such catalysts need to be revisited and tuned to accommodate the complex operating conditions in various industries such as wider temperature windows and the more complex compositions of the exhausts. This review focuses on the poisoning and deactivation of zeolite-based SCR catalysts, especially Cu-SSZ-13. State-of-the-art of different mechanisms of deactivation (including hydrothermal ageing, sulphur poisoning, hydrocarbon poisoning and chemical poisoning) are discussed critically, attempting to establish the link between current zeolite-based SCR catalysts and the possible application demands in industries.

Road traffic has become the leading source of air pollution in fast-growing sub-Saharan African cities. Yet, there is a dearth of robust city-wide data for understanding space-time variations and inequalities in combustion related emissions and exposures. We combined nitrogen dioxide (NO _2 ) and nitric oxide (NO) measurement data from 134 locations in the Greater Accra Metropolitan Area (GAMA), with geographical, meteorological, and population factors in spatio-temporal mixed effects models to predict NO _2 and NO concentrations at fine spatial (50 m) and temporal (weekly) resolution over the entire GAMA. Model performance was evaluated with 10-fold cross-validation (CV), and predictions were summarized as annual and seasonal (dusty [Harmattan] and rainy [non-Harmattan]) mean concentrations. The predictions were used to examine population distributions of, and socioeconomic inequalities in, exposure at the census enumeration area (EA) level. The models explained 88% and 79% of the spatiotemporal variability in NO _2 and NO concentrations, respectively. The mean predicted annual, non-Harmattan and Harmattan NO _2 levels were 37 (range: 1–189), 28 (range: 1–170) and 50 (range: 1–195) µ g m ^−3 , respectively. Unlike NO _2 , NO concentrations were highest in the non-Harmattan season (41 [range: 31–521] µ g m ^−3 ). Road traffic was the dominant factor for both pollutants, but NO _2 had higher spatial heterogeneity than NO. For both pollutants, the levels were substantially higher in the city core, where the entire population (100%) was exposed to annual NO _2 levels exceeding the World Health Organization (WHO) guideline of 10 µ g m ^−3 . Significant disparities in NO _2 concentrations existed across socioeconomic gradients, with residents in the poorest communities exposed to levels about 15 µ g m ^−3 higher compared with the wealthiest ( p < 0.001). The results showed the important role of road traffic emissions in air pollution concentrations in the GAMA, which has major implications for the health of the city’s poorest residents. These data could support climate and health impact assessments as well as policy evaluations in the city.

Hydrogen is advantageous for use in internal combustion engines (ICEs) because of its high laminar flame speed and carbon-neutral characteristics. However, because of its low minimum ignition energy, abnormal combustions such as back-fire, pre-ignition, and knocking hinder its efficient supply as a fuel to ICEs under near stoichiometric conditions. Hence, in this study, the effect of various excessive air ratios (λ) on the performance of a hydrogen-fueled spark ignition engine using port fuel injection (PFI) was evaluated under wide-open throttle conditions. After determining the highest limit for the maximum brake torque, a hydrogen direct injection (DI) system was applied under the same λ and abnormal combustion limits to improve the brake power (BP). Results show that at 1,500 rpm, a maximum BP of 14.7 kW was achieved under a λ value of 1.4 with PFI; however, it can be increased up to 21.1 kW using DI with the same brake thermal efficiency under a compression ratio of 14. [ABSTRACT FROM AUTHOR]

The diesel engine is utilized in most commercial vehicles to carry items from various firms; nevertheless, diesel engines emit massive amounts of nitrogen oxides (NOx) which are harmful to human health. A typical approach for reducing NOx emissions from diesel engines is the selective catalytic reduction (SCR) system; however, several reasons make reducing NOx emissions a challenge: urea particles frequently become solid in the injector and difficult to disseminate across the system; the injector frequently struggles to spray the smaller particles of urea; the larger urea particles from the injector readily cling to the system; it is also difficult to evaporate urea droplets because of the exhaust and wall temperatures (Tw), resulting in an increase in solid deposits in the system, uncontrolled ammonia water solution injection, and NOx emissions problems. The light-duty diesel engine (LDD), medium-duty diesel engine (MDD), heavy-duty diesel engine (HDD), and marine diesel engine use different treatments to optimize NOx conversion efficiency in the SCR system. This review analyzes several studies in the literature which aim to increase NOx conversion in different diesel engine types. The approach and methods demonstrated in this study provide a suitable starting point for future research into reducing NOx emissions from diesel engines, particularly for engines with comparable specifications. [ABSTRACT FROM AUTHOR]

Dual-fueled combustion, using high and low reactivity fuels simultaneously, is a promising combustion method that enables reduction of nitrogen oxides (NOx) emission. However, the total amount of NOx emissions in the exhaust gas is strongly influenced by the overall excessive air ratio (lambda) of air—fuel mixture. Thus, lean mixture condition is important for NOx emissions although RCCI operating condition is applied. In addition, not only reduction of emissions, but improvement in BTE requires the boost pressure to be increased. Thus, variations in boost pressure via a controlling turbocharger system was evaluated under general dual-fueled combustion and RCCI conditions using diesel and natural gas fuels while tracing emissions and BTE. The results indicated that higher boost pressure was more effective on RCCI condition in reducing NOx emissions and enhancing BTE and turbocharging system efficiency with lower carbon dioxides, compared to those of general dual-fueled combustion condition. Especially, turbocharger efficiency of dual-fueled combustion was higher than that of diesel single-fueled combustion related with composition of exhaust gas and exhaust gas temperatures. [ABSTRACT FROM AUTHOR]

Copyright of Refractories / Naihuo Cailiao is the property of Naihuo Cailia (Refractories) Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Sorption selective catalytic reduction of nitrogen oxides (NOx) (sorption-SCR) has ever been proposed for replacing commercial urea selective catalytic reduction of NOx (urea-SCR), while only the single-stage sorption cycle is hitherto adopted for sorption-SCR. Herein, various multi-stage ammonia production cycles is built to solve the problem of relative high starting temperature with ammonia transfer (AT) unit and help detect the remaining ammonia in ammonia storage and delivery system (ASDS) with ammonia warning (AW) unit. Except for the singlestage ammonia production cycle with MnCl2, other sorption-SCR strategies all present overwhelming advantages over urea-SCR considering the much higher NOx conversion driven by the heat source lower than 100°C and better matching characteristics with low-temperature catalysts. Furthermore, the required mass of sorbent for each type of sorption-SCR is less than half of the mass of AdBlue for urea-SCR. Therefore, the multifunctional multi-stage sorption-SCR can realize compact and renewable ammonia storage and delivery with low thermal energy consumption and high NOx conversion, which brings a bright potential for efficient commercial de-NOx technology. [ABSTRACT FROM AUTHOR]

In this paper the effect of incremental rise of tyre pyrolysis oil in the blend is analyzed to explore the performance and emission parameters of a single cylinder VCR diesel engine. During experimentation proportion of TPO were 10, 25, 35, 50, 60, 75 and 90 % with diesel fuel. Tests were conducted using four different loading conditions. The experiments were performed using an analytical tool known as Design of Experiments on the basis of Response Surface Methodology. The conclusive models of the RSM prepared to predict the response criterion such as BSFC, BTE, CO, nitrogen oxides, smoke and Mechanical efficiency. The results depicted that with rise in the load, BSFC decrease while it increases with rise in TPO proportion and found lower at 50% TPO and increases again above 50% TPO. BTE increased with increase in the load and found to be highest at higher TPO. For all blends, an increase in Nitrogen oxides found with increase in load and TPO proportion. Parameter optimization executed using the desirability approach method of the RSM for improved conduct and reduced emissions. A load of 4.57 kg (61.7567%) and 40.94% TPO in the blend are suggested as the optimal criterion for the test engine. [ABSTRACT FROM AUTHOR]

Summary: This study investigated the reduction of nitrogen oxides (NOx) and N2O emissions by selective catalytic oxidation (SCO) of an ammonia oxidation catalyst (AOC). This was conducted using a diesel engine with various oxidation catalysts, such as a diesel oxidation catalyst and a diesel particulate filter. The after‐treatment system was equipped with urea‐selective catalytic reduction (SCR) using a commercially available V2O5/TiO2 catalyst and an AOC to prevent ammonia slip. The performance of the system, after treatment, was tested under various engine loads and urea injection conditions. The operating conditions that were applied included abnormal operation of urea‐SCR in the presence of abundant NH3 due to excessive spraying of urea. At 400°C to 450°C, and a high load, the diesel engine produced undesirable reactions at V2O5/TiO2 based urea‐SCR, causing emission of excess N2O. Additionally, under identical operating conditions, the AOC with Pt metal increased the emissions of NO, NO2, and N2O via oxidation of NH3. Excess emission of NO increases the total amount of NOx, including NO2. However, undesirable oxidation of NH3 at the AOC was significantly decreased at 460°C. [ABSTRACT FROM AUTHOR]

The purpose of this study is to evaluate the pressurized titanium dioxide (TiO2) fixation method and its application to hardened vertical structures nearby the road. The usefulness of pressurized TiO2 fixation method for the application of vertical concrete road structures such as side ditches, barriers, and retaining walls was evaluated based on conditions of experiment taking cognizance of pressurization time and pressure. To confirm the TiO2 distribution characteristics, penetration depth and mass ratio of TiO2 particles in the concrerte specimens were measured after pressurezed fixation. Additionally, the removal efficiencies of nitrogen oxides (NOx) were evaluated using the NOx analyzing system. The penetration depth and surface mass ratio of TiO2 increased as increasing pressure and pressurization time. To achieve the efficiency of NOx removal more than 40%, a pressure 0.2 MPa and higher than 0.3 MPa with a pressurization time at least 10 seconds and 5 seconds were required, respectively. The finding demonstrated that the pressured TiO2 fixing method was effective, indicating that the suggested NOx removal technology is adequately appropriate to existing vertical concrete road constructions. [ABSTRACT FROM AUTHOR]

This study investigated the combustion characteristics by changing the operating parameters and piston bowl geometries in diesel/gasoline dual-fuel combustion. The experiment was conducted in a light-duty single cylinder diesel engine satisfying the EURO-6 regulation adapted for dual-fuel operation. The engine was operated under a low load condition, which was 1,500 rpm and gross IMEP 5.2 bar, with compression ratio of 14. The effects of the operating parameters, namely, the fuel ratio, diesel injection timing, and pilot duration, were analyzed for three different piston bowl geometries. Based on each result, the optimization experiments were conducted to satisfy the various constraints. The gross indicated specific NOx (gISNOx) was restricted below 0.21 g/kWh, the soot emission was limited to below 0.2 FSN, and the maximum pressure rise rate (mPRR) was confined to below 5 bar/deg. Simultaneously, the gross indicated efficiency (GIE) was controlled over 40 %. As a result, these constraints were completely satisfied in all pistons. [ABSTRACT FROM AUTHOR]

The emission of nitrogen oxides (NOx) imposes a serious threat to ecological environment and human health. Selective catalytic reduction (SCR) technology is considered as an efficient method to remove NOx. It has been widely used to remove NOx which emit from stationary source and mobile source. MnCeTiOx catalyst is a kind of SCR catalyst with high de-NOx performance. A series of W doped MnCeTiOx catalysts were prepared by coprecipitation method. The effects of W doping on de-NOx performance and sulfur resistance of catalysts were investigated. The crystal structure, chemical states of surface elements and surface active species of MnCeTiOx and W0. 15MnCeTiOx catalysts were characterized by X-ray diffraction, X-ray photoelectron spectroscopy and insitu diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) methods. The reaction mechanism of improving de-NOx performance and sulfur resistance of MnCeTiOx catalyst through W doping was discussed. The results show that W doping can increase the relative content of Ce3+ and Mn3+ species on catalyst surface, and enrich the active species which can participate in SCR reaction on catalyst surface, thus improve the de-NOx performance and N2 selectivity of catalyst. W doping can also inhibit the formation and deposition of NH4HSO4 species on catalyst surface, thus improve the sulfur resistance of catalyst. [ABSTRACT FROM AUTHOR]

Air pollution is a ubiquitous problem plaguing global citizens with decreased quality of life. Pollutants are created both indoors and out and contribute to poor indoor and ambient air quality. Indoor air purification technologies have been created and are successful in removing particulate matter, though there are severe limitations and environmental repercussions with existing technologies used to eliminate gaseous pollutants. To address this need, research and development led to the creation of a gaseous pollution control device which uses a patented photocatalyst capable of simultaneously destroying both volatile organic compounds and nitrogen oxides over extended time durations. A laboratory-scale prototype was built and a rigorously tested to evaluate the removal of nitric oxide and select volatile organic compounds (formaldehyde, ethanol and limonene). The test campaign used various velocities, surface conditions, length scales, light power outputs and pollutant compositions to generate a statistically relevant data set for evaluating performance. Performance evaluation of the two prototype units produced reduction efficiency between 550–60% for formaldehyde, 60–85% for nitric oxide, 80–99% for limonene, and 100% for ethanol, over the air velocity range of 0.5 to 2.0 m s−1. Removal efficiency of the unit appears to be most dependent on the molecular structure (i.e., bond strength) of the pollutant and the pollutant residence time within the unit (i.e., velocity or having multiple units in series). Additionally, there are opportunities for optimizing performance of the units through controlling power output of the illumination source or periodically performing a simple water rinse. [ABSTRACT FROM AUTHOR]

In this study, a high-load expansion strategy was investigated by varying the effective compression ratio (CR) using the variable valve duration (VVD) method during combustion in a gasoline/diesel dual-fuel premixed compression ignition engine. The effective CR was varied from 15.0 to 10.6 via the retardation of the intake valve closing timing (IVC) at 1,500 rpm. With respect to optimization, the diesel injection timing, fuel ratio, and exhaust gas recirculation (EGR) rate were adjusted for each optimized condition. The limitations were the maximum pressure rise rate (below 10 bar/deg) and in-cylinder pressure (below 150 bar) with NOx < 40 ppm and soot < 0.2 FSN. The results emphasized that when the effective CR was 12.7, the maximum load increased by 10.5 % (gIMEP from 13.3 to 14.7 bar) compared with that at a CR of 15.0. Although the decrease in CR resulted in a gross thermal efficiency loss, the difference was negligible (from 45.9 to 45.5 %). The main reason for high-load expansion was the increase in intake air volume under the same intake pressure upon lowering the CR and the margin for the maximum in-cylinder pressure. From this result, it can be concluded that the Miller cycle is useful for the expansion of high load ranges in premixed combustion systems. [ABSTRACT FROM AUTHOR]

• Three-way catalysts (TWC) are used in spark-ignition engines to meet exhaust regulations. • NH 3 emissions are generated in TWCs during the NO x reduction. • In Euro 7, NH 3 has been designated as a new regulated substance. • NH 3 formation is greatly influenced by catalyst activation. Emission regulations have been made more strengthened both regulated (NO x) and unregulated emissions (NH 3 , N 2 O, and CH 4) from internal combustion engines. Delays in supply of batteries and semiconductors has slowed the commercialization of electric and hydrogen electric vehicles, necessitating further research on internal combustion engines for the time being. Gasoline and liquefied petroleum gas (LPG) vehicles equipped with spark-ignition (SI) engines use three-way catalysts (TWC) to meet exhaust regulations; however, recent studies have shown that TWC can cause NH 3 emissions. This study analyzed the NOx and NH3 emission characteristics of LPG engines owing to catalyst activation, aging and capacity. A basic study of TWC was conducted using engine experiments, and real vehicle characteristics were analyzed using a worldwide harmonized light vehicle test procedure (WLTP) and real driving emissions (RDE). As a result, it was confirmed that there is a trade-off relationship between NOx reduction and the generation of NH 3 in the three-way catalyst system. a decrease in ambient temperature delays catalyst activation, resulting in reduced NH 3 emissions. Aged catalysts exhibit an increase in NH 3 due to accumulated ammonia within the catalyst. Moreover, higher catalyst capacity is associated with a more substantial reduction in NOx, contributing to an increase in NH 3 generation. [ABSTRACT FROM AUTHOR]

The paper presents results of the measurements of the sulfur dioxide (SO2) and nitrogen dioxide (NO2) concentration and meteorological parameters: temperature, air pressure, relative humidity and wind speed. The data were collected from January 2019 to December 2020 at two stations, namely Center and Heating plant, in the City of Bijeljina, Republic of Srpska, Bosnia and Herzegovina. SO2 and NO2 are one of the major air pollutants that could negatively affect the human health. Levels of SO2 and NO2 in air samples and meteorological variables from urban zone of Bijeljina were determined at both localities, which represent a highly-populated area with intensive traffic. This topic has not been studied up to now in Bijeljina, although the recent research data indicates that there is a correlation between meteorological parameters and air pollutants. Statistical analysis confirms direct corelation between SO2 and NO2 and meteorological parameters, specially temperature in locality Center (r = -0.639), the wind speed in locality Heating plant (r = 0.399) and relative humidity (r = 0.162). Correlation of NO2 with temperature is not confirmed in both localities. The wind speed increase is followed by rises of the NO2 concentration values and vice versa. Correlation of NO2 with pressure is confirmed in locality Center (r = 0.128) but it is not confirmed in locality Heating plant. Correlation between NO2 and relative humidity found to be negative in locality Center (r = -0.062). These parameters are the most important meteorological factors influencing the variation in SO2 and NO2 concentration in the air during the research. Depending on the obtained correlation, meteorological parameters had a positive or negative impact on air pollution. [ABSTRACT FROM AUTHOR]

Recent studies have reached mixed conclusions regarding the association between exposure to air pollutants and attention-deficit hyperactivity disorder (ADHD). We performed systematic review and meta-analysis to determine whether air pollutants were risk factors for the development of ADHD in children. We systematically searched databases for all relevant studies up to 2 July 2019. Together, the studies indicated that exposure to PAHs (risk ratio (RR): 0.98, 95% confidence interval (CI): 0.82–1.17), NOx (RR: 1.04, 95% CI: 0.94–1.15), and PM (RR: 1.11, 95% CI: 0.93–1.33) did not have any material relationship with an increased risk of ADHD. Heterogeneity of study data was low (I2: 2.7%, P = 0.409) for studies examining PAHs, but was substantial for NOx and PM (I2: 68.4%, P = 0.007 and I2: 60.1%, P = 0.014, respectively). However, these results should be interpreted with caution since the number of epidemiological studies investigating this issue were limited. [ABSTRACT FROM AUTHOR]

The plasma-chemical hybrid process (PCHP) has been effectively employed for the simultaneous removal of NOx and SOx in combustion gases. In this study, a PCHP-based semi-dry-type desulfurization reactor was developed for high-temperature exhaust gas from a glass melting furnace with a 10-MW-class thermal input. The NO in the exhaust gas is oxidized to NO2 by ozone generated from scale-up dielectric barrier discharge-based plasma ozonizers with a total input power of 77 kW and total ozone generation of 10 kg/h. SO2 reacts with NaOH solution in the semi-dry reactor to produce Na2SO3, which further reacts with NO2 to reduce NOx to N2. The produced Na2SO4 is in the form of dry particles and can be collected and reused in glass manufacturing. The exhaust gas at the outlet of the semi-dry reactor is maintained between 200 and 250 °C to protect the dry-type electrostatic precipitator. A localized cooling area is created by spraying cooling water, which is necessary to prevent the thermal decomposition of ozone and to spray an efficient aqueous solution for achieving dry conditions at the reactor outlet. Simultaneous desulfurization and denitrification were tested at low glass-production rates by injecting adequate flow rates of ozone for NO removal. Optimal removal efficiencies of 45 and 39% were obtained for NO and NOx, respectively. More than 90% of the byproducts were recovered in the form of Na2SO4. The designed facility with the semi-dry-type PCHP was confirmed to be highly effective and promising for exhaust gas treatment in glass manufacturing. [ABSTRACT FROM AUTHOR]

Background: The carcinogenicity of air pollution and its impact on the risk of lung cancer is well known; however, there are still knowledge gaps and mixed results for other sites of cancer., Methods: The current study aimed to evaluate the associations between ambient air pollution [fine particulate matter (PM2.5) and nitrogen oxides (NOx)] and cancer incidence. Exposure assessment was based on historical addresses of >900 000 participants. Cancer incidence included primary cancer cases diagnosed from 2007 to 2015 (n = 30 979). Cox regression was used to evaluate the associations between ambient air pollution and cancer incidence [hazard ratio (HR), 95% CI]., Results: In the single-pollutant models, an increase of one interquartile range (IQR) (2.11 µg/m3) of PM2.5 was associated with an increased risk of all cancer sites (HR = 1.51, 95% CI: 1.47-1.54), lung cancer (HR = 1.73, 95% CI: 1.60-1.87), bladder cancer (HR = 1.50, 95% CI: 1.37-1.65), breast cancer (HR = 1.50, 95% CI: 1.42-1.58) and prostate cancer (HR = 1.41, 95% CI: 1.31-1.52). In the single-pollutant and the co-pollutant models, the estimates for PM2.5 were stronger compared with NOx for all the investigated cancer sites., Conclusions: Our findings confirm the carcinogenicity of ambient air pollution on lung cancer and provide additional evidence for bladder, breast and prostate cancers. Further studies are needed to confirm our observation regarding prostate cancer. However, the need for more research should not be a barrier to implementing policies to limit the population's exposure to air pollution., (© The Author(s) 2024; all rights reserved. Published by Oxford University Press on behalf of the International Epidemiological Association.)

Ammonia (NH3) and nitrogen oxides (NOx: nitrogen dioxide [NO2] + nitric oxide [NO]) play important roles in atmospheric chemistry. Throughout most of Africa, emissions of these gases are predominantly from soils and biomass burning. Here we use observations of tropospheric NO2 vertical column densities (VCDs) from the Ozone Monitoring Instrument from 2005 through 2017 and atmospheric NH3 VCDs from the Infrared Atmospheric Sounding Interferometer from 2008 through 2017 to evaluate seasonal variation of NO2 and NH3 VCDs across Africa and in seven African ecoregions. In regions where mean annual precipitation (MAP) is under 500 mm yr−1, we find that NO2 and NH3 VCDs are positively related to monthly precipitation, and where MAP is between 500 and 1,750 mm yr−1 or higher, NO2 VCDs are negatively related to monthly precipitation. In dry ecoregions, temperature and precipitation were important predictors of NH3 and NO2 VCDs, likely related to variation in soil emissions. In mesic ecoregions, monthly NO2 VCDs were strongly related to burned area, suggesting that biomass burning drives seasonality. NH3 VCDs in mesic ecoregions were positively related to both monthly temperature and monthly carbon monoxide (CO) VCDs, suggesting that a mixture of soil and biomass burning emissions influenced NH3 seasonality. In northern mesic ecoregions, monthly temperature explained most of the variance in monthly NH3 VCDs, suggesting that soil sources, including animal excreta, determined NH3 seasonality. In southern mesic ecoregions, monthly CO VCDs explained more variation in NH3 VCDs than temperature, suggesting that biomass burning may have greater influence over NH3 seasonality. Plain Language Summary: Ammonia (NH3) and nitrogen oxides (NOx: nitrogen dioxide [NO2] + nitric oxide [NO]) are gases that are emitted naturally as well as through human activity and contribute to air pollution. Throughout most of Africa, emissions of these gases are primarily from vegetation fires and from microbial activity and chemical transformations in soils. Most ecoregions in Africa experience a distinct dry season and rainy season, with fires occurring during the dry season, and more microbial activity occurring in soils during the rainy season. We used satellite observations of NH3 and NO2 concentrations in the atmosphere to understand how and why concentrations of these gases vary seasonally across seven distinct African ecoregions. Overall, we find that in dry ecoregions, NO2 and NH3 concentrations increase during the rainy season, when increases in precipitation and temperature stimulate greater soil microbial activity and increase emissions of both gases from soils. In contrast, in wetter ecoregions, NO2 and NH3 concentrations increase during the dry season. The increase in NO2 concentrations is a result of the increase in vegetation fires during this time of the year, but NH3 concentrations increase due to seasonal changes in both soil and fire emissions. Key Points: For mean annual precipitation (MAP) below 500 mm yr−1, monthly gas concentrations were positively related to monthly precipitationFor MAP between 500 and 1,750 mm yr−1, monthly nitrogen dioxide (NO2) was negatively and monthly ammonia (NH3) was unrelated to monthly precipitationThe importance of soil and biomass burning for NO2 and NH3 seasonality varied across biomes depending on rainfall and other characteristics [ABSTRACT FROM AUTHOR]

The crystallization of Al-rich CHA zeolites with an ultra-low organic structure directing agent (OSDA) content and without using pre-crystallized FAU zeolites as Si and/or Al sources has been accomplished by controlling the nucleation step. Indeed, the use of "gel-type" seeds containing discrete nanosized CHA nanoparticles (i.e. below 100 nm) combined with the understanding of the seed-assisted crystallization mechanism has allowed the efficient preparation of Al-rich CHA materials using ultra-low methyltriethylammonium (MTEA) contents (MTEA/Si molar ratios ∼ 0.03–0.04), making this synthetic route very cost-competitive compared to recent synthesis improvements for CHA using substoichiometric contents of expensive OSDAs (i.e. N,N,N -trimethyladamantammonium, TMAda). The optimized Al-rich CHA materials, after incorporating the catalytically active copper cations, perform as ideal catalysts for the selective catalytic reduction (SCR) of NOx with ammonia relevant for heavy-duty applications. [Display omitted] • Al-rich CHA zeolites with ultra-low OSDA by controlling the nucleation step. • Active CHA seeds as gel-type precursors to enable Al-rich CHA crystallization. • Optimized Cu-CHA as SCR-NOx catalysts relevant for heavy-duty applications. [ABSTRACT FROM AUTHOR]

[Display omitted] • It analyzed methods of application of naphtha and ethanol to diesel engines. • Naphtha is suitable for blending with diesel and then supply. • Ethanol is suitable for injection into the intake air independently of diesel fuel. • Ethanol convergence combustion is superior in reducing NOx emissions. • The application of naphtha or ethanol needs to improve THC and CO emissions. Since electrification is difficult in the sector where heavy-duty diesel engines are used, research is still needed to improve air pollutants. In addition, it is necessary to search for fuel to solve the depletion of fossil fuels and to study appropriate combustion methods according to fuel characteristics. In this study, naphtha or ethanol was selected as a fuel that could replace a certain fraction of diesel fuel. This study aims to compare both methods of supplying and burning naphtha or ethanol with diesel. The method of supplying naphtha or ethanol blended directly with diesel and burning it is suitable for naphtha. Since ethanol has a lower heating value, blended-fuel combustion mode with ethanol reduces IMEP net. However, this method of separate injection and burning is only suitable for ethanol. When naphtha is utilized in convergence combustion, a wetting phenomenon arises due to its limited evaporation characteristics, leading to a reduction in fuel delivery. The NOx reduction rate was higher in the convergence combustion mode than that in the blended-fuel combustion mode. However, both the combustion methods led to an increase in the THC and CO emissions. [ABSTRACT FROM AUTHOR]

In order to remove nitric oxide (NO) from flue gas, from small coal-fired boilers, it is necessary to exploit the cost-effective wet denitration technology. The absorption of NO with sodium chlorate solution was studied. The effects of experimental conditions, such as temperature, NaClO3 concentration, type of acid, mole ratio of NaClO3 to hydrogen ions, on NO removal rate were investigated, and the optimal conditions were established. As the effect of temperature on denitration was related to the type of acid used, the temperature required for sulfuric acid was high, and the temperature required for nitric acid was low. The optimal mole ratio between NaClO3 and the two types of acids was the same. The reaction products were analyzed by ion chromatography. The reacted solution could be recycled after the removal of sodium chloride. The reaction mechanism and the total chemical reaction equation of NaClO3 denitration were deduced. The thermodynamic derivations showed that this oxidation reaction could proceed spontaneously and the reaction was very thorough. NaClO3 exhibited high NO removal efficiency and its denitration cost was much lower than sodium chlorite.