Ultra-low Emission Research Articles

Study on Combustion and NOx Emission Characteristics of Low-Quality Coal with Wide Load Based on Fuel Modification

Enhancing the operational flexibility and environmental performance of coal-fired boilers under wide-load conditions presents a critical challenge in China’s low-carbon transition, particularly for low-quality coals (LQCs) with abundant reserves, poor combustibility, and high NOx emissions. To overcome the intrinsically low reactivity of LQC, peak-shaving performance and combustion behavior were systematically investigated on an MW-grade pilot-scale test platform employing the fuel modification strategy in this study. Stable fuel modification was achieved without any auxiliary energy for LQCs and Shenmu bituminous coal (SBC) across a load range of 20~83% and 26~88%, respectively, demonstrating the excellent fuel reactivity and strengthened release control of volatile and nitrogenous species. The modified LQC exhibited ignition, combustion, and burnout characteristics comparable to Shouyang lean coal (SLC), enabling a “dimensionality-reduction utilization” strategy. The double-side fuel modification device (FMD) operation maintained axially symmetric temperatures (<1250 °C) in horizontal combustion chambers, while single-side operation caused thermal asymmetry, with peak temperatures skewed toward the FMD side (<1200 °C). Original NOx emissions were effectively suppressed, remaining below 106.89 mg/m3 (@6%O2) for LQC and 122.76 mg/m3 (@6%O2) for SBC over broad load ranges, and even achieved ultra-low original NOx emissions (<50 mg/m3). Distinct load-dependent advantages were observed for each coal type: SBC favored high-load thermal uniformity and low-load NOx abatement, whereas LQC exhibited the inverse trend. These findings underscore the importance of a load-adaptive coal selection and FMD operation mode. This study provides both theoretical insights and engineering guidance for retrofitting coal-fired power units toward flexible, low-emission operation under deep peak-shaving scenarios.

Research Progress on Flue Gas Desulfurization and Denitrification by Activated Carbon Method

SO2 and NOx emissions from iron and steel production pollute the atmosphere. With the implementation of ultra-low emission standards, the requirements for flue gas purification have become more stringent. Activated carbon, due to its rich surface chemistry, stable physical structure, and excellent adsorption and renewability, has a significant effect on the synergistic removal of multiple pollutants from industrial flue gas, and its industrial application has achieved a SO2 removal rate of ≥98% and a NOx removal rate of ≥83%. Firstly, we analyze the structure of activated carbon and the adsorption principle, discuss the mechanism of desulfurization and denitrification, and explore the shortcomings of the technology; then, we summarize the modification methods of activated carbon, determine the impregnation method of loading non-precious metal oxides as the optimal solution, and elucidate the loading conditions, process, and reaction mechanism; finally, we discuss the current status of the research, analyze the process deficiencies and the direction of optimization, and look forward to the prospect of development.

Urban Collaborations: Bridging the Gap Between Research and Action on Climate Change and Health

In the face of escalating climate change and its profound implications for public health, integrating research and actionable policy in urban environments is increasingly critical. Cities, as epicentres of both climate impacts and innovative research initiatives, exemplify the complex interplay between academic insights and practical implementation. Despite the abundance of scientific data on climate hazards, such as extreme heat and its health impacts, a significant gap remains in translating this evidence into effective local policies. This gap underscores the necessity for robust partnerships between academic researchers and city policymakers to foster interdisciplinary collaboration and evidence-based decision-making. Successful examples from cities such as London, with its Ultra Low Emission Zone, and Phoenix’s heat mitigation strategies highlight the benefits of such partnerships in connecting environmental and public health concerns. Effective communication of scientific findings, particularly distinguishing between known facts and uncertainties, and transparently discussing policy trade-offs, is crucial for building public trust and facilitating informed decisions. Embedding researchers in city governments and involving policymakers in academic environments can enhance mutual understanding and ensure research is timely and relevant. Funders play a pivotal role by prioritizing interdisciplinary research that addresses urgent urban challenges and promotes actionable solutions. Furthermore, fostering continuous dialogue and collaboration between researchers and city officials is essential for adapting policies to evolving scientific insights and local contexts. By aligning academic research agendas with urban stakeholders’ needs and emphasizing actionable, localized solutions, academia and policymakers can collaboratively address climate and health challenges, leading to more resilient and sustainable cities.

Bimetallic synergy in non-precious metal Mn/Ba-SSZ-13 zeolite for improving NOx storage capacity at low temperatures.

Bimetallic synergy in non-precious metal Mn/Ba-SSZ-13 zeolite for improving NOx storage capacity at low temperatures.

Unlocking the Potential of Thermal Post-Treatments: A Study on Odor Emission Control in Eucalyptus Wood Particleboard.

Eucalyptus wood particleboard (EPB), commonly used in indoor decoration, releases volatile organic compounds (VOCs) that can adversely affect indoor air quality and human health. This study systematically examined the VOC emission characteristics of EPB using headspace solid-phase microextraction (HS-SPME) coupled with gas chromatography mass spectrometry (GC-MS). A total of 65 VOCs were identified, with medium-volatility organic compounds (MVOCs) accounting for 28 compounds, low-volatility organic compounds (LVOCs) for 26, and high-volatility organic compounds (HVOCs) for 11. Terpenoids dominated the VOCs, comprising 78.46%, followed by aldehydes (10.77%) and alkanes (7.69%). Key odorant compounds (KOCs) were identified using the relative odor activity value (ROAV), with hexanal (ROAV = 100) and o-cymene (ROAV = 76.90) emerging as the most significant contributors to the overall odor profile. Thermal post-treatment at temperatures of 50-60 °C for durations of 6-12 h was found to be an effective method for reducing the residual VOCs and KOCs in the EPB, leading to a marked decrease in the peak areas of key odorants. The findings suggest several strategies for minimizing VOC emissions and eliminating residual odor, including reducing the use of miscellaneous wood materials, controlling the production of o-cymene, and employing thermal post-treatment at moderate temperatures. These measures provide a promising approach to reducing VOC and odor emissions from EPB and similar composite wood products, thereby enhancing their suitability for indoor applications. This study innovatively establishes an evaluation system for VOC emission characteristics in wood-based panels based on the ROAV. It elucidates the contribution mechanisms of key odor-active substances (e.g., hexanal and pentanal) and presents a thermal post-treatment process for source control, achieving simultaneous VOCs and odor elimination. A ROAV-guided hierarchical management strategy is proposed, providing scientific guidelines for the industrial production of high-quality particleboards with ultralow emissions (TVOC < 50 μg/m3) and minimal odor intensity (OI < Grade 3).

Synergistic Enhancement of Hydrolysis-Oxidation Drives Efficient Catalytic Elimination of Chlorinated Aromatics over VOx/TiO2 Catalysts at Low Temperature.

The efficient catalytic elimination of toxic chlorinated aromatics (i.e., dioxins, chlorobenzenes, etc.) at low temperature is still a great challenge. Based on the VOx/TiO2 catalyst, a hydrolysis-oxidation strategy (CeOx and WOx doping) was built for desirable low-temperature catalytic activity, product selectivity, H2O tolerance, and chlorine desorption. The in situ and ex situ experimental characterizations and density functional theory calculations revealed that hydrolysis sites favored molecular adsorption, C-Cl cleavage, and HCl formation; meanwhile, oxidation sites enhanced the activation of reactive oxygen species and improved oxygen mobility and redox properties. The enhanced oxygen storage/release capacity (33-53 fold) and extended redox cycle (e.g., from V5+↔V4+ to V5+↔V4+↔V3+) favored the deep oxidation. The introduction of H2O triggered the hydrolysis-oxidation process that promoted the catalytic activity and chlorine desorption due to the elevated generation of ·O2- and higher-activity ·OH. Furthermore, the water resistance of the VOx/TiO2-based catalyst was enhanced after the application of the hydrolysis-oxidation strategy. The V-Ce-W/Ti catalyst exhibited remarkable removal efficiency of dioxins (96.7-98.2%), which was reduced from 0.34-0.48 ng I-TEQ Nm-3 to 0.006-0.016 ng I-TEQ Nm-3 during pilot tests at 160-180 °C, achieving ultralow emissions. This work provides practical guidance for industry development for efficiently eliminating chlorinated organics in flue gas.

The political effects of London’s Ultra Low Emission Zone

The unexpected defeat of the Labour Party in a recent by-election has been attributed to the expansion of London’s Ultra Low Emission Zone (ULEZ). Employing a difference-in-difference methodology across two phases of ULEZ expansion and examining three sets of elections, we find inconsistent political effects. In all three election scenarios, we observe relatively minor effects for the incumbent Labour Party. Support for both the Green Party and the Conservative Party fluctuated. Complementary individual-level analysis using UKHLS data reveals no discernible political party support effects stemming from the ULEZ expansion announcement in 2017 on those with non-compliant cars relative to the rest of the population. Our study suggests caution in generalising the political effects of green policies from mixed evidence in a single case, while contributing to the growing body of research on the complexities of public response to environmentally focused legislation.

Research on Carbon Emission Characteristics of a Typical Ultra-Low Emission Coal-Fired Power Plant

ObjectiveThis study aims to improve carbon emission accounting accuracy and provide optimized emission factors for ultra-low emission coal-fired power plants by detailed carbon emission accounting and carbon balance analysis based on the Life Cycle Assessment (LCA) method.MethodsEmissions were calculated via coal combustion activity and LCA respectively, with carbon balance tracking and correlation analysis of influencing factors (coal consumption, efficiency).ResultsWeekly emissions peaked midweek, LCA reduced estimates by 0.19 MtCO2, coal contributed 95.4% of carbon inputs, and strong correlations (r = 0.98–0.99) supported emission factors (1.52 tCO2/t coal, 0.75 tCO2/MWh generation).ConclusionOptimized emission factors enable efficient accounting, while prioritizing high-calorific coal and unit efficiency upgrades reduces emissions, with LCA offering a more holistic assessment for sustainable management.Graphical

A method for delineating traffic low emission control zone based on deep learning and multi-objective optimization.

Current methods for defining traffic low emission control zones (TLEZ) often face limitations that hinder their widespread implementation and effectiveness. This study addresses these challenges by employing a comprehensive approach to analyze PM2.5 concentration levels within TLEZ. This study utilizes PM2.5 data collected by taxi fleets, integrating static road network features and dynamic time series features to gain a detailed understanding of pollution distribution patterns across different urban areas. To capture these complex distribution patterns of PM2.5, a sophisticated deep learning model that combines Convolutional Neural Networks (CNN), Long Short-Term Memory (LSTM) networks, and Attention Mechanism (AM) is deployed. This model adeptly identifies spatial and temporal variations in PM2.5 concentrations, allowing for a more accurate and responsive analysis of pollution levels. A multi-objective optimization model is developed to minimize the overall impact on residents' daily lives, which considers both environmental and social factors in the delineation of TLEZ. The optimization model is solved using the Non-dominated Sorting Genetic Algorithm II (NSGA-II), which is a robust evolutionary algorithm that facilitates the identification of Pareto-optimal solutions. These solutions can help define the optimal boundaries for Low, Ultra-Low, and Zero Emission Zones. By establishing a framework for assessing and optimizing these zones, this study provides valuable insights and actionable guidance for policymakers and urban planners.

Enhancing SO3 and Fine Particle Co-Removal in Low-Low Temperature Electrostatic Precipitation via Turbulent Agglomeration

Fine particulate matter (PM) and sulfur trioxide (SO3) from coal-fired flue gas pose significant environmental and health risks. While low-low temperature electrostatic precipitators (LLT-ESPs) enhance PM and SO3 removal by cooling flue gas below the acid dew point, their efficiency is limited by incomplete agglomeration. This study proposes integrating turbulent agglomeration technology into LLT-ESP systems to improve collision and adhesion between droplets and particles. Experiments were conducted under three conditions: flue gas containing SO3 alone, fly ash alone, and their mixture. Particle size distributions, mass concentrations, and removal efficiencies were analyzed using ELPI+ and PM samplers. Results showed that turbulent agglomeration reduced the number concentration of sulfuric acid droplets by 21.4% from 1.59 × 107 cm−3 to 1.25 × 107 cm−3 (SO3-only case) and fine fly ash particles by 19.5% from 5.79 × 106 cm−3 to 4.66 × 106 cm−3 (fly-ash-only case). Although LLT-ESP combined with turbulent agglomeration has a certain removal effect in the case of individual pollutants, the overall effect is not unsatisfactory, especially for SO3, whose mass-based removal efficiency was merely 16.2%. The value of the fly-ash-only case was 92.1%. Synergistic effects in the coexistence scenario (fly ash and SO3) significantly enhanced agglomeration, increasing SO3 and PM removal efficiencies to 82.9% and 97.6%, respectively, compared to 69.7% and 90.1% without turbulent agglomeration. The mechanism behind the efficiency improvement involved droplet–particle collisions, sulfate deposition, and improved particle charging. This work demonstrates that turbulent agglomeration optimizes multi-pollutant control in LLT-ESP systems, offering a feasible strategy for achieving ultra-low emissions in coal-fired power plants.

Organic Fingerprints of Condensable Particulate Matter from Ultralow Emission Stationary Sources in China

Organic Fingerprints of Condensable Particulate Matter from Ultralow Emission Stationary Sources in China

Distributed Regime and Swirler Effects on Methane and Coke Oven Gas Combustion Characteristics

The present study deals with combustion characteristics of methane and coke oven gas for various swirl numbers in a highly internal recirculative combustor under colorless distributed combustion conditions. In order to achieve that, the fuels have been consumed numerically in the combustor at various oxygen concentrations by using a N2 diluent to reduce oxygen concentration in the air. During the modelings, swirl number has been changed from s=0 to s=1 in an interval of 0.2. In this way, swirler effects on its combustion characteristics have been studied. In order to perform all modelings, the k-ε realizable turbulence model, the PDF/Mixture Fraction combustion model, and P-1 radiation model have been used. The results showed that decrease in oxygen concentration caused a more uniform temperature field in the combustor along with ultra-low NOx emissions. When the oxygen rate was reduced from 21% to 15%, a 9% decrease in the highest temperature reached in the combustion chamber was observed. In addition, a 99% decrease in nitrogen oxide formation was observed. This has been achieved with internal and external (colorless distributed regime) entrainments. In addition to these, it is concluded that the swirler has affected that combustion took place faster mostly because of better air-fuel mixture in the combustor. It has been observed that the air and fuel mixture occurs faster in the swirler effect, which has effects on the flow characteristics in the combustion chamber and has positive effects on recirculation, which can help to obtain conditions close to distributed combustion conditions in general. For 21% oxygen ratio, nitrogen oxide formation could be reduced by approximately 50% by increasing the swirl number from 0 to 1.

Research Progress and Hotspots of Steel Slag Application in Road Construction: A Bibliometric Perspective

The accumulation of steel slag has become a significant obstacle for the steel industry in achieving ultra-low emission targets. Given its composition is similar to that of road construction materials, steel slag holds substantial potential for application in sustainable road construction. This study investigated the current status and future trends of steel slag applications in road construction through a bibliometric analysis. The findings reveal that steel slag applications primarily focus on steel slag concrete, asphalt, steel slag aggregates, and steel slag processing technologies. The activation of its reactivity and stability emerged as a key research direction, with carbonated steel slag demonstrating exceptional performance in road construction. This study provides a scientific foundation for the high-value utilization of steel slag. It suggests optimizing its reactivity, stability, and carbonation, which will be crucial for expanding its use in road construction.

London’s Ultra Low Emission Zone and active travel to school: a qualitative study exploring the experiences of children, families and teachers

ObjectiveTaking a qualitative approach, we aimed to understand how London’s Ultra Low Emission Zone (ULEZ) might work to change behaviour and improve health in the context of the school journey.DesignPrimary...

Formulated absorbent for fine desulfurization and carbon capture of blast furnace gas based on alcohol amine solution

The development of deep desulfurization of blast furnace gas combined with carbon capture is the key implementation point of pollution reduction and carbon reduction in the steel industry. Combined with the current situation of immature deep desulfurization technology and urgent demand for carbon capture, a CO2/COS（carbon oxysulfide）/H2S integrated high-efficiency removal formula absorbent was designed and developed. The main conclusions of this paper are as follows: The absorbent system for simultaneous deep removal of CO2, H2S and COS from blast furnace gas was constructed, and the formula absorbent composed of 1.5 mol/L MDEA + 0.5 mol/L MEA + 6% MOR + 4% DBU + 3% DDBAC was obtained. The total sulfur in the purified gas is less than 20 mg/Nm³, with a CO2 capture efficiency greater than 90%, and the regeneration rate of the formulated absorbent is above 80%, exhibiting excellent anti-corrosion and thermal stability performance. This research lays the foundation for the practical implementation of collaborative pollution reduction and carbon reduction in the steel industry. It integrates the achievement of ultra-low emissions and carbon reduction, providing significant environmental and economic benefits, and demonstrates important practical value and research significance.

Novel thermodynamic model for simulation of hydrogen/diesel fueled PCCI engine.

Novel thermodynamic model for simulation of hydrogen/diesel fueled PCCI engine.

Development of the NO2 ratio model for heavy-duty diesel engine two-stage SCR aftertreatment system

A diesel oxidation catalyst (DOC) outlet nitrogen dioxide (NO2) ratio model based on the model-based calibration (MBC) method was proposed, which is an important part of the two-stage selective catalytic reduction (SCR) control strategy for heavy-duty diesel engines. Emissions regulations for heavy-duty diesel engines around the world have become more stringent in limiting nitrogen oxide (NOx), especially when the engine is cold starting, which brings serious challenges to the aftertreatment system. The two-stage SCR system with the close coupled selective catalytic reduction-diesel oxidation catalyst-diesel particulate filter-selective catalytic reduction (ccSCR-DOC-DPF-SCR) layout has the potential to achieve ultra-low NOx emissions due to its high technology maturity, but the two-stage SCR urea injection control strategy based on the chemical reaction kinetics model presents a new functional requirement for the prediction of NO2 ratio at the DOC outlet. However, experiments show that the Euro VI method based on calibration to obtain DOC outlet NO2 ratio was not suitable for the two-stage SCR system, because of the temperature delay effect of ccSCR in transient conditions. Therefore, a quadratic polynomial model using the MBC method was constructed to predict the DOC outlet NO2 ratio in the two-stage SCR system. The proposed MBC model can predict the NO2 ratio by using exhaust mass flow rate, DOC inlet temperature, and DOC inlet NOx concentration. Experiments show that the proposed MBC model has wide applicability, for the two-stage SCR system under transient conditions, whether ccSCR urea injection is enabled will not affect the accuracy of the model’s prediction of the NO2 ratio for the DOC outlet or SCR inlet.

Infrared Ultralow‐Emissivity Polymeric Metafabric Conductors Enabling Remarkable Electromagnetic and Thermal Management

AbstractInfrared ultralow‐emissivity fabric has garnered significant interest for applications in infrared stealth and personal thermal management. However, reconciling the competing demands of low emissivity, breathability, and mechanical strength poses a formidable challenge. Here, an air‐permeable polymeric metafabric distinguished by a unique non‐through‐hole structure is presented. This design is achieved through the electroless plating of silver nanoparticles onto commercially available nylon fabric, supplemented by an intermediate layer of hot‐processed nylon porous mesh. This metafabric demonstrates an ultralow emissivity of 0.044, an exceptional electrical conductivity of 51 315 S m−1, an impressive electromagnetic interference shielding efficiency of 78 dB, and a high tensile strength of 110 MPa. The emissivity, conductivity, and strength of the metafabric are among the highest values reported for infrared low‐emissivity fabrics. The metafabric also exhibits an air permeability that conforms to Grade 2 of international standards. The metafabric facilitates personal precision heating across diverse environments through its integrated capabilities of passive radiative and active solar/Joule heating. Additionally, the metafabric displays antibacterial properties, flame retardancy, sweat absorption, quick‐drying, and washability performance, thereby significantly enhancing its wearability. This high‐performance, multifunctional, infrared ultralow‐emissivity polymeric metafabric holds great promise for applications in infrared camouflage, electromagnetic protection, and personal thermal management.

Experimental investigation on N2O emission characteristics of ammonia-diesel dual-fuel engines

Blending ammonia in combustion is an effective approach to reducing carbon emission for diesel engines, but the combustion of ammonia may result in the generation of elevated concentrations of nitrous oxide (N2O), potentially contributing to a new source of greenhouse gas emissions. This study investigates the impact of engine load, diesel double injection strategy, and the ammonia energy ratio (AER) on N2O emission in ammonia-diesel dual-fuel combustion mode. The results show that N2O emission is increased with blending ammonia compared to pure diesel combustion, while as the load increases, the higher in-cylinder combustion temperature leads to a decrease in N2O emission. In the ammonia-diesel dual-fuel combustion mode, diesel double injection strategy is conducive to the reduction in N2O emission compared to single injection strategy. As the pre-injection timing is delayed, N2O emission first decreases and then increases, reaching a minimum near −40 °CA ATDC. The postponed main-injection timing leads to the decreased in-cylinder combustion temperature, deteriorating N2O emission. In the engine with a compression ratio (CR) of 18, when AER is in the range of 20% to 65%, the volume fraction of N2O emission remains around 20 × 10−6. However, under the condition of AER = 80%, low chemical reactivity of ammonia causes the substantially increased N2O emission. By increasing CR to 21 and adopting optimal injection strategy, combustion in activated thermal atmosphere is achieved, resulting in a substantial reduction in the N2O original emission concentration. Ultra-low N2O emission (exhaust N2O volume fraction less than 10 × 10−6) is achieved at AER = 80%.

Historical inventories and future scenarios of multiple hazardous air pollutants (HAPs) emissions from the iron and steel production industry in China.

Historical inventories and future scenarios of multiple hazardous air pollutants (HAPs) emissions from the iron and steel production industry in China.