Nitrogen Oxides Control Research Articles

Design of Bifunctional Cu-SSZ-13@Mn2Cu1Al1Ox Core-Shell Catalyst with Superior Activity for the Simultaneous Removal of VOCs and NOx.

Synchronous control of volatile organic compounds (VOCs) and nitrogen oxides (NOx) is of great importance for ozone and PM2.5 pollution control. Balancing VOC oxidation and the NH3-SCR reaction is the key to achieving the simultaneous removal of these two pollutants. In this work, a vertically oriented Mn2Cu1Al1Ox nanosheet is grown in situ on the surface of Cu-SSZ-13 to synthesize a core-shell bifunctional catalyst (Cu-SSZ-13@Mn2Cu1Al1Ox) with multiple active sites. The optimized Cu-SSZ-13@Mn2Cu1Al1Ox catalyst delivered excellent performance for the simultaneous removal of VOCs and NOx with both 100% conversion at 300 °C in the presence of 5% water vapor. Physicochemical characterization and density functional theory (DFT) calculations revealed that Cu-SSZ-13@Mn2Cu1Al1Ox possesses more surface acidity and oxygen vacancies. The charge transfer between the core and shell is the intrinsic reason for the improved activity for both VOC and NOx removal. The molecular orbital theory is used to explain the different adsorption energies due to the different bonding modes between the core-shell and mixed individual catalysts. This work provides a novel strategy for designing efficient catalysts for the simultaneous removal of VOCs and NOx or other multiple pollutants.

Nonlinear effect of NOx concentration decrease on secondary aerosol formation in the Beijing-Tianjin-Hebei region: Evidence from smog chamber experiments and field observations

During the COVID-19 lockdown in the Beijing-Tianjin-Hebei (BTH) region in China, large decrease in nitrogen oxides (NOx) emissions, especially in the transportation sector, could not avoid the occurrence of heavy PM2.5 pollution where nitrate dominated the PM2.5 mass increase. To experimentally reveal the effect of NOx control on the formation of PM2.5 secondary components (nitrate in particular), photochemical simulation experiments of mixed volatile organic compounds (VOCs) under various NOx concentrations with smog chamber were performed. The proportions of gaseous precursors in the control experiment were comparable to ambient conditions typically observed in the BTH region. Under relatively constant VOCs concentrations, when the initial NOx concentration was reduced to 40% of that in the control experiment (labelled as NOx,0), the particle mass concentration was not significantly reduced, but when the initial NOx concentration decreased to 20 % of NOx,0, the mass concentration of particles as well as nitrate and organics showed a sudden decrease. A “critical point” where the mass concentration of secondary aerosol started to decline as the initial NOx concentration decreased, located at 0.2–0.4 NOx,0 (or 0.18–0.44 NO2,0) in smog chamber experiments. The oxidation capacity and solar radiation intensity played key roles in the mass concentration and compositions of the formed particles. In field observations in the BTH region in the autumn and winter seasons, the “critical point” exist at 0.15–0.34 NO2,0, which coincided mostly with the laboratory simulation results. Our results suggest that a reduction of NOx emission by >60% could lead to significant reductions of secondary aerosol formation, which can be an effective way to further alleviate PM2.5 pollution in the BTH region.

Impact of spatial scales of control measures on the effectiveness of ozone pollution mitigation in eastern China

Ozone (O3) pollution is becoming the primary air pollution issue with the large decrease in fine particulate concentrations in eastern China. The development of widely recognized policies for controlling O3 pollution episodes is urgent. This study aims to provide actionable and comprehensive suggestions for O3 control policy development, with an emphasis on the precursor emission reductions.Here, we compared the impacts of different spatial scale reductions on a widespread O3 pollution episode in eastern China by a state-of-the-art regional air quality model. We find that region-scale joint control (in >30 cities) is much more effective than city-scale sporadic reduction in reducing O3 concentration. Sporadic controls only reduce the maximum daily 8-h average (MDA8) O3 by ∼1 μg/m3 in the controlled city, whereas regional controls lead to a MDA8 O3 decrease of ∼8 μg/m3 in the controlled region. In addition, the emission reduction effectiveness increased by 2.6 times from <5 cities to >30 cities. Continuous reductions have a cumulative effect on the decrease of MDA8 O3, showing the strongest effects within 24 h and diminishing after 48 h, which underscores the importance of reducing emissions 24 h prior to an episode. Moreover, the effect of control measures on MDA8 O3 varies spatially depending on the ratio of volatile organic compounds (VOCs) to nitrogen oxides (NOx) (VOCs/NOx). Both the reductions of VOC and NOx emissions have a positive effect on the decrease of MDA8 O3 in summer, but the effects of VOC reductions are 1.2 to 1.7 times higher than those of NOx reductions. The residential sector, due to its high VOCs/NOx emission ratio, exhibits the highest efficiency in the reduction of O3 concentrations. Our results highlight the importance of regional joint control and synergistic reduction of VOCs and NOx in eastern China.

Hydrothermally stable metal oxide-zeolite composite catalysts for low-temperature NOx reduction with improved N2 selectivity

Development of hydrothermally stable, low-temperature catalysts for controlling nitrogen oxides emissions from mobile sources remains an urgent challenge. We have prepared a metal oxide-zeolite composite catalyst by depositing Mn active species on a mixture support of CeO2/Al2O3 and ZSM-5. This composite catalyst is hydrothermally stable and shows improved low-temperature SCR activity and significantly reduced N2O formation than the corresponding metal oxide catalyst. Comparing with a Cu-CHA catalyst, the composite catalyst has a faster response to NH3 injection and less NH3 slip. Our characterization results reveal that such an oxide-zeolite composite catalyst contains more acidic sites and Mn3+ species as a result of oxide-zeolite interaction, and this interaction leads to the generation of more NH4+ species bound to the Brønsted acid sites and more reactive NOx species absorbed on the Mn sites. Herein, we report our mechanistic understanding of the oxide-zeolite composite catalyst and its molecular pathway for improving the low-temperature activity and N2 selectivity for NH3-SCR reaction. Practically, this work may provide an alternative methodology for low-temperature NOx control from diesel vehicles.

Highly Selective Nitrite Hydrogenation to Ammonia over Iridium Nanoclusters: Competitive Adsorption Mechanism.

Wet denitrification is a promising approach to control nitrogen oxides (NOx) produced in fossil fuel combustion. Yet, the highly concentrated nitrite (NO2-) wastewater generated poses a major threat to the aqueous environment. Here, iridium nanoclusters (d = 1.63 nm) deposited on TiO2 were applied for NO2- reduction to ammonia (NRA), showing an exceptional NH4+ selectivity of 95% and a production rate of 20.51 mgN·L-1·h-1, which held significant potential for NO2- wastewater purification and ammonia resource recovery. Notably, an interesting non-first-order NO2- hydrogenation kinetics was observed, which was further confirmed to result from the competitive adsorption mechanism between H2 and NO2- over iridium. The NRA pathways on the Ir(111) surface were explored via density functional theory calculations with the NO2-* → NO* → HNO* → HNOH* → H2NOH* → NH2* → NH3* identified as the most energetically favorable pathway and the NO* → HNO* confirmed as the rate-determining step. In situ DRIFTS further experimentally verified the generation of HNO* intermediate during NO* hydrogenation on Ir(111). To verify NRA kinetics at varied NO2- concentrations or H2 pressures, a kinetic model was derived based on the Langmuir-Hinshelwood competitive adsorption mechanism. These findings provide mechanistic insights into the NRA pathways on Ir nanocatalysts, which will be beneficial for wet denitrification waste stream decontamination and valorization.

Emission Reduction from a Light-Duty Diesel Vehicle over Two Driving Cycles through Dynamic Correction Calibration.

The potential of a method of transient control of model-based engine charge control (MCCT) is investigated to minimize nitrogen oxide (NOx) emissions of a light-duty diesel vehicle over two driving cycles, the worldwide harmonized light-duty test cycle (WLTC) and real driving emission (RDE) cycle. The MCCT function was switched on by calibrating factor maps corrected for several parameters. In addition, the relationship between electronic control unit signals and nitrogen oxide (NOx) emissions was analyzed under the WLTC and RDE. The engine-out and tail-pipe NOx emissions in the WLTC and RDE could achieve varying degrees of reduction with MCCT.

Research and Development of an Industrial Denitration-Used Burner with Multiple Ejectors via Computational Fluid Dynamics Analysis

Nowadays, since the air pollution problem is becoming global and denitrification is efficient to control nitrogen oxides, research and development of burners with low pollutant emissions in industries are urgent and necessary due to the increasingly severe environmental requirements. Based on the advanced CFD (computational fluid dynamics) numerical analysis technique, this work focuses on developing an industrial denitration-used burner, aiming to decrease the emission of nitrogen oxides. A burner with multiple ejectors is proposed, and the gas premixing and combustion process in the burner are systematically studied. Firstly, for the ejector, the well-known orthogonal experiment method is adopted to reveal the premixing performance under different structural parameters. Results show that the angle and number of swirl blades have significant effects on the CO mixing uniformity. The CO mixing uniformity first decreases and then increases with thr rising swirl blade angle, and it enhances with more swirl blades. Through comparison, a preferred ejector is determined with optimal structure parameters including the nozzle diameter of 75 mm, the ejector suction chamber diameter of 290 mm, the blade swirl angle of 45∘, and the swirl blade number 16. And then, the burners installed with the confirmed ejector and two types of flues, i.e., a cylindrical and a rectangular one, are simulated and compared. The effects of ejector arrangements on the temperature distributions at the burner outlet are analyzed qualitatively and quantitatively. It is found that the temperature variances at the outlets of R2 and C1 are the smallest, respectively, 13.12 and 23.69, representing the optimal temperature uniformity under each type. Finally, the burner of the R2 arrangement is verified with a satisfied premixing performance and combustion temperature uniformity, meeting the denitration demands in the industry.

Ozone mitigations beyond the control of nitrogen oxides and volatile organic compounds

Ozone mitigations beyond the control of nitrogen oxides and volatile organic compounds

Biogenic volatile organic compounds enhance ozone production and complicate control efforts: Insights from long-term observations in Hong Kong

Ground-level ozone (O3) pollution is a major air-quality issue in China. With decreasing emissions of anthropogenic precursors, natural precursors may become increasingly important in O3 pollution. However, understanding of the change in biogenic volatile organic compounds (BVOCs) and its environmental impact in China has been hindered by the lack of long-term measurements of VOCs. In this study, we analyze the continuous measurements of O3 and its precursors obtained in Hong Kong during 2013–2019 and demonstrate the increasingly important role of BVOCs in O3 production. Driven by the warming temperature, Biogenic isoprene at a suburban site (Tung Chung) increased by 0.05 ± 0.02 ppbv/yr (18%/yr), which is in sharp contrast to the decreases in anthropogenic precursors during the study period. Detailed chemical modeling shows that increased BVOCs enhanced local O3 production by 0.31 ppbv/h/yr (23%) annually, and the effect was the most obvious in summer (by 0.44 ppbv/h/yr or 27%). Increased BVOCs also affected the O3-precursor (anthropogenic) relationships by increasing the O3 sensitivity to nitrogen oxides (NOx) and decreasing the O3 sensitivity to anthropogenic VOCs (AVOCs). Despite changes in precursors (decreasing NOx, increasing BVOCs, and decreasing some AVOCs), the O3 formation remains in VOC-limited regimes at Tung Chung. Joint control of AVOCs and NOx (at a ratio greater than 1.2) would help avoid exacerbation of O3 pollution and reduce NO2 pollution. In the short term, an AVOCs-focused strategy would help reduce O3 to a moderate level; but because of the presence of the natural BVOCs, a drastic cut in NOx emissions would be needed to meet a more stringent O3 standard. Our findings also suggest the BVOCs increase likely occurred in the larger Pearl River Delta (PRD) region, and thus the results from our study in Hong Kong may have implications for developing AVOCs/NOx reduction measures in the PRD region and beyond.

Drivers of Increasing Ozone during the Two Phases of Clean Air Actions in China 2013-2020.

In response to the severe air pollution issue, the Chinese government implemented two phases (Phase I, 2013-2017; Phase II, 2018-2020) of clean air actions since 2013, resulting in a significant decline in fine particles (PM2.5) during 2013-2020, while the warm-season (April-September) mean maximum daily 8 h average ozone (MDA8 O3) increased by 2.6 μg m-3 yr-1 in China during the same period. Here, we derived the drivers behind the rising O3 concentrations during the two phases of clean air actions by using a bottom-up emission inventory, a regional chemical transport model, and a multiple linear regression model. We found that both meteorological variations (3.6 μg m-3) and anthropogenic emissions (6.7 μg m-3) contributed to the growth of MDA8 O3 from 2013 to 2020, with the changes in anthropogenic emissions playing a more important role. The anthropogenic contributions to the O3 rise during 2017-2020 (1.2 μg m-3) were much lower than that in 2013-2017 (5.2 μg m-3). The lack of volatile organic compound (VOC) control and the decline in nitrogen oxides (NOx) emissions were responsible for the O3 increase in 2013-2017 due to VOC-limited regimes in most urban areas, while the synergistic control of VOC and NOx in Phase II initially worked to mitigate O3 pollution during 2018-2020, although its effectiveness was offset by the penalty of PM2.5 decline. Future mitigation efforts should pay more attention to the simultaneous control of VOC and NOx to improve O3 air quality.

Health impacts under different ozone mitigation pathways in Beijing-Tianjin-Hebei and its surroundings

To evaluate the effects of the various ozone (O3) control approaches on environmental health and health inequalities, 121 reduction scenarios for nitrogen oxides (NOx) and volatile organic compounds (VOCs) were developed, and their environmental health impacts were calculated. With the target of achieving the 90th percentile of the daily maximum 8 h mean O3 concentration (MDA8-90th) of 160 μg/m3 in Beijing-Tianjin-Hebei and its surroundings (“2 + 26” cities), three typical scenarios namely, High-NOx reduction ratio (HN, NOx/VOCs = 6:1), High-VOCs reduction ratio (HV, NOx/VOCs = 3:7), and Balanced reduction ratio (Balanced, NOx/VOCs = 1:1) were investigated. The results show that O3 formation is currently NOx-limited at the regional scale, while some developed cities are VOC-limited, indicating that NOx mitigation should be the core for achieving the targeted concentration (160 μg/m3) at the regional scale, whereas cities such as Beijing in the short term should focus on VOCs mitigation. The population-weighted O3 concentrations in the HN, Balanced, and HV scenarios were 159.19, 159.19, and 158.44 μg/m3, respectively. In addition, the O3-related premature mortality was 41,320 in “2 + 26” cities; control measures under HN, Balanced, and HV could potentially decrease O3-related premature deaths by 59.94 %, 60.25 %, and 71.48 %, respectively. The HV scenario has been found to be more advantageous in lowering the O3-related environmental health impacts than the HN and Balanced scenarios. It was further found that premature deaths avoided by the HN scenario were mainly concentrated in economically unadvanced regions, whereas those prevented by the HV scenario were mainly concentrated in developed cities. This may lead to geographical inequities in environmental health. As ozone pollution in large cities with high population density is primarily VOC-limited, decrease in VOCs should be focused on in the short term to avoid more O3-related premature deaths, whereas NOx control may be more important in decreasing ozone concentrations and ozone-related mortality in the future.

Mechanistic insights into collaborative removal of NOx and chromium from flue gas in denitrifying biotrickling filter

Nitrogen oxides (NOx) and chromium can cause harm to human health and ecological environment. An aerobic denitrifying biotrickling filter (DBTF) for simultaneous removal of NOx and chromium from flue gas was investigated. NOx and chromium removal efficiency could reach up to 98 % and 88 %, respectively. Halomonas, Stappia, Pseudomonas and UG_Peptococcaceae were the core chromium-resistance- denitrifying genus. Anti-oxidative stress proteins (RpoS, SOD, OxyR and catalase) and anti-heavy metal proteins (MntA, FbpA, TorB and ChrE etc.) and the denitrifying enzymes (NarH, NarI, NapA, NapB, NirK, NirS and NorB) involved in the regulation of chromium stress and the reduction of NOx, as shown by 16 S rDNA, metagenomic and metaproteomic sequencing. The biofilm was characterized by FTIR, XPS, EEM, and SEM-EDS. XPS spectra indicated the formation of a chromium carbonate by microbial induced carbonate precipitation. Chromium speciation in biofilm mainly consisted of 52.8 % organic matter bound state, 35.1 % carbonate bound state and 10.7 % exchangeable state. Flue gas chromium could be removed in the form of chromium carbonate bioprecipitate and HA-Cr via complexation of humic acids in extracellular polymeric substances (EPS), biosorption and biodeposition. DBTF was capable of NOx reduction and chromium removal by denitrification. The results provide a new potential for the collaborative control of NOx and heavy metals from flue gas by the DBTF.

Changes in O3-VOCs-NOx Sensitivity and VOCs Sources at an Urban Site of Nanjing Between 2020 and 2021

The synergistic control of PM2.5 and ozone (O3) are the focus of air quality improvement during the 14th Five-Year Plan in China. The production of O3 shows a highly nonlinear relationship with its precursors volatile organic compounds (VOCs) and nitrogen oxides (NOx). In this study, we conducted online observations of O3, VOCs, and NOx at an urban site in downtown Nanjing from April to September of 2020 and 2021. The average concentrations of O3 and its precursors between these two years were compared, and then the O3-VOCs-NOx sensitivity and the VOCs sources were analyzed using the observation-based box model (OBM) and positive matrix factorization (PMF), respectively. The results showed that the mean daily maximum O3 concentrations, VOCs, and NOx concentrations decreased by 7% (P=0.031), 17.6% (P<0.001), and 14.0% (P=0.004) from April to September of 2021 compared with those from the same period in 2020, respectively. The average relative incremental reactivity (RIR) values of NOx and anthropogenic VOCs during the O3 non-attainment days in 2020 and 2021 were 0.17 and 0.14 and 0.21 and 0.14, respectively. The positive RIR values of NOx and VOCs indicated that O3 production was controlled by both VOCs and NOx. The O3 production potential contours (EKMA curves) based on the 50×50 scenario simulations also supported this conclusion. The PMF results showed that industrial and traffic-related emissions were the main sources of VOCs. The five PMF-resolved factors were identified as industrial emissions, including industrial liquefied petroleum gas (LPG) use, the benzene-related industry, petrochemistry, toluene-related industry, and solvent and paint use, which contributed 55%-57% of the average mass concentration of total VOCs. The summed relative contributions of vehicular exhaust and gasoline evaporation were 43%-45%. Petrochemistry and solvent and paint use showed the two highest RIR values, suggesting that VOCs from these two sources should be reduced with priority to control O3. With the implementation of VOCs and NOx control measures, the O3-VOCs-NOx sensitivity and VOCs sources have changed, and therefore we still need to follow their variations in the future to timely adjust O3 control strategies during the 14th Five-Year Plan.

Atom-pair catalytic sites for high-efficiency emission control of nitrogen oxides at low temperature

Atom-pair catalytic sites for high-efficiency emission control of nitrogen oxides at low temperature

Experimental Analysis for Nitrogen Oxide Reduction in a Diesel Engine by the Hydrogen-Assisted Selective Catalytic Reduction Technique

Diesel engine emissions pose a serious threat to the environment and cause inevitable hazards to the atmosphere. The technique that is used to control and combat nitrogen oxide (NOX) emissions is selective catalytic reduction. However, the various experimental conditions in the SCR technique will reduce NOX emissions. Former studies experimentally discovered the decrease of NOx discharges at a higher temperature. In this study, a two-cylinder diesel engine with a 34 kW rated power at 3750 rpm under low-temperature operating conditions underwent hydrogen-assisted selective catalytic reduction of NOx. The experiment was performed by differing the hydrogen injection duration (0–40°CA) and NOX emissions were studied. Variation in emissions with H2 injection was investigated. On varying the hydrogen injection duration, NOX, HC, CO2, CO, and smoke emissions are reduced (mention the % of reduction) and it can be applied in real time to reduce global warming.

Ex Ante Costs Versus Ex Post Costs of the Large Municipal Waste Combustor Rule

AbstractThis article compares the U.S. Environmental Protection Agency’s (EPA) ex ante cost analysis of its 1995 Large Municipal Waste Combustor (MWC): New Source Performance Standards and Emissions Guidelines rule to an ex post assessment of its cost. Unlike many retrospective cost analyses, where ex post assessments are limited due to lack of data on compliance costs, this case study is unique because we located and used plant-level survey data from the U.S. Department of Energy and Governmental Advisory Associates in a comparison of ex ante and ex post costs of individual MWCs. We find the ex post capital expenditures for nitrogen oxide control systems are typically lower than the EPA ex ante estimates, while the ex post capital expenditures for mercury control systems tend to be higher than the EPA ex ante estimates. Finally, while we find a few outliers, the average ratio of ex post to ex ante capital expenditures for particulate matter and sulfur dioxide emissions control is near unity.

Meteorological and chemical controls on surface ozone diurnal variability in Beijing: A clustering-based perspective

This study aimed to reveal the dominant, recurring patterns of surface ozone diurnal cycles in Beijing, their quantitative characteristics, namely, occurrence frequency and transition probability, and their potential linkages to meteorological and chemical processes based on multi-source observations (surface ozone, satellite-based ozone precursors, ground-based and sonde-based meteorological measurements) and reanalyses (ERA5 meteorological and TCR2 chemical reanalyses). By applying K-means clustering, four distinct ozone diurnal patterns (Cluster 1: all-day low anomaly; Cluster 2: nighttime high-daytime low anomaly; Cluster 3: nighttime low-daytime high anomaly; Cluster 4: extreme pollution pattern with all-day high anomaly) are objectively identified from 2013 to 2020 warm-season (May–September) surface ozone measurements. Despite a relatively low total occurrence, the extreme pollution pattern tended to persist over an extended period (average persistence of 2.3 days). Composite analyses of multi-source meteorology indicate that the elevated nocturnal ozone in Cluster 2 is associated with the compensating downdraft flow of nocturnal convective storms. By contrast, elevated nocturnal ozone in Cluster 4 was associated with the prevailing low-level jet (LLJ) over the whole North China Plain (NCP) region. The LLJ-related dynamical processes trigger regional transport in the residual layer and downward mixing from the residual layer, elevating the background ozone level in downstream Beijing. Moreover, Cluster 4 is under the control of 500-hPa anomalous high pressure, which leads to daytime hot-dry weather favoring the occurrence of extreme afternoon pollution via photochemical ozone production. From Cluster 1 to Cluster 4, satellite-based formaldehyde (CH2O) increased by 71% accompanied by less change in nitrogen dioxide (NO2), causing a shift in ozone production sensitivity. Because extreme pollution pattern typically occurs in the transition regime, synergetic emission control of volatile organic compounds (VOCs) and nitrogen oxides (NOx) would be effective in alleviating severe ozone pollution in Beijing.

Elucidation of exhaust gas recirculation deposit formation mechanism based on chemical analysis of components

To comply with strict emission regulations, vehicles are equipped with exhaust gas recirculation (EGR) systems that control nitrogen oxide emissions by returning part of the exhaust gas to the intake air. However, since deposits form in the EGR piping and valves, leading to pipe clogging, valve sticking, and in the worst case, failure of these components, there is a need to clarify the mechanism of deposit formation to predict and reduce deposit accumulation. While most of the previous studies have focused on the powdery deposits that clog the EGR cooler, this study aims to elucidate the formation mechanism of both the lacquer-like hard deposits and wet soft deposits that cause EGR valve sticking by quantitative and molecular-level analyses. In these experiments, a portion of the exhaust gas from an actual diesel engine without soot removed by diesel particulate filter (DPF) was used. Deposits were continuously generated on a simulated EGR line with a downstream temperature gradient from the engine outlet, while measuring the inner wall temperature. The collected deposits were subjected to comprehensive chemical analysis. The analysis showed that 75 % of the solvent-soluble deposit components were polycyclic aromatic hydrocarbons (PAHs), which were the main component of the hard and soft deposits. Most of the PAHs in the hard deposits that formed at a high inner wall temperature were C17 or higher. The hard deposit with an inner wall temperature of 137 °C contained 0.016 mg/cm2 of 6-ring benzo[ghi]perylene and 0.26 × 10-3 mg/cm2 of 4-ring pyrene. On the other hand, the soft deposit is formed at an inner wall temperature of 80 °C, contained 0.022 mg/cm2 of pyrene, which is significantly more than in the hard deposit. This shows that PAHs in the exhaust gas condense when the gas temperature reaches their dew points, and that the deposits formed at higher inner wall temperatures contain more PAHs with higher boiling points. High-molecular weight aromatic compounds with oxygen and nitrogen functional groups were detected in the solvent-insoluble deposit components. These compounds were found to be derived from the polymerization of oxygenated and nitrogenated PAHs through dehydration condensation and cross-linking reactions.

Review of Combustion Performance Improvement and Nitrogen-Containing Pollutant Control in the Pure Hydrogen Internal Combustion Engine

Review Review of Combustion Performance Improvement and Nitrogen-Containing Pollutant Control in the Pure Hydrogen Internal Combustion Engine Chun Lu 1, Wei Chen 1,2, Qingsong Zuo 1, Guohui Zhu 1, Yi Zhang 3, and Zhengbai Liu 4,* 1 School of Mechanical Engineering and Mechanics, Xiangtan University, Xiangtan 411105, China 2 Foshan Green Intelligent Manufacturing Research Institute of Xiangtan University, Foshan 528311, China 3 School of Energy and Power Engineering, Jiangsu University, Zhenjiang 212013, China 4 School of Innovation and Entrepreneurship, Southern University of Science and Technology, Shenzhen 518055, China * Correspondence: liuzb3@sustc.edu.cn Received: 24 September 2022 Accepted: 21 November 2022 Published: 25 December 2022 Abstract: Hydrogen energy is regarded as the best form to achieve the dual-carbon strategic goal of “carbon peaking and carbon neutrality”. It is well-known that hydrogen energy has the characteristics of zero carbon, green, high energy, and renewable. Recently, the pure hydrogen internal combustion engine (PH-ICE) has become one of the essential directions of hydrogen energy application due to its outstanding advantages, such as no carbon emission, high efficiency, high reliability, and low pollution. So far, the PH-ICE has aroused great attention from both domestic and foreign auto companies and research institutions. This paper first introduces the latest development status of PH-ICE. Secondly, from the in-engine and out-engine technologies aspects of the PH-ICE, a comprehensive summary of its combustion performance improvement and nitrogen oxide control technology is given. Finally, the future challenges and development trends of the hydrogen ICE are discussed.

Investigating the spatio-temporal influences of urbanization and other socioeconomic factors on city-level industrial NOx emissions: A case study in China

Cities play an essential role in industrial nitrogen oxides (NOx) control actions. Few studies have considered the spatiotemporal heterogeneity of the key influence factors that affect industrial NOx emissions at the city level. This work evaluates the impacts of urbanization level on industrial NOx emissions during 2017–2019 at the prefecture-city in China. We construct an extended Stochastic Impacts by Regression on Population, Affluence and Technology (STIRPAT) framework based on the Geographically Weighted Regression (GWR), and Geographically and Temporally Weighted Regression (GTWR) model. The urbanization level was measured based on nighttime light (NTL) data. The results suggest that, first, the GTWR model has a better goodness of fit. Urbanization has a significant spatiotemporal heterogeneous effect on industrial NOx emissions. The median coefficient estimations of urbanization are −0.34 (95%CI: −1.38, 1.47), demonstrating a positive correlation in eastern China, yet negative in the western region. Other socioeconomic factors such as industrial electricity consumption, the share of secondary industry, population density, and research and development (R&D) expenditures have a significantly positive influence on industrial NOx emissions, while gross domestic production (GDP) has a negative impact. Our findings reveal that, due to the variances in urbanization levels and socio-economic factors, NOx control policies and regional emission reduction strategies in China implemented in a tailor-made form (such as “One-City-One-Policy”) will be more effective.