Combustion Research Articles

The effect of additives on particulate matter and gaseous emissions from combustion and oxy-fuel combustion of a biofuel blend composed of poultry manure and pine wood chips.

In this study, the effect of additives on particulate matter (PM) and flue gas emissions during the co-combustion of poultry waste and pine woodchips in air and oxy-fuel combustion conditions was examined. The appropriate additive for the fuel mixture to reduce PM emissions has been selected by a fast screening method based on thermogravimetric analysis (TGA) in oxygen environment. Among the additives CaHPO4, MgCO3, MnCO3, MgPO4, kaolin, CaO, and Zn, the most suitable ones were determined as Zn and MgCO3. The thermal degradation performance of biofuels containing 2 wt% additives was examined by TGA method under pyrolysis, combustion, and oxy-fuel combustion conditions. Ashes obtained from the additivated biofuel mixture were examined by XRF, XRD, and SEM-EDS analyses, and the effect of additives on the ash structure was investigated. Flue gas emissions of co-firing biofuel were analyzed by TGA-FTIR. It has been observed that the highest emission is CO2, and the oxy-fuel combustion process and addivation have shown reducing effect on CO2 emissions. Under oxy-fuel combustion conditions, higher CO and lower NOx, SO2, and HCl emissions occurred at a lower rate compared to the air environment, and additives also showed a reducing effect. The composition and crystal structure of Zn-additivated biofuel ash support its reducing effect in PM emissions. It was concluded that Zn is a more suitable additive in terms of PM and flue gas emissions than MgCO3.

Imprint of incomplete combustion processes on the water column of the anthropogenic-pressured Baltic Sea.

This study evaluates the distribution and sources of thermogenic organic matter in the Baltic Sea water column, focusing on polycyclic aromatic hydrocarbons (PAH), dissolved black carbon (DBC), and the imprint of thermogenic organic matter on the dissolved organic matter (DOM) pool. The spatial patterns and complex interactions between land-based and atmospheric sources were assessed from Kiel Bay to Pomeranian Bight within the water column with the combined targeted and untargeted approaches. The findings emphasize the significant influence of terrestrial inputs from the Oder River and autochthonous production composing DOM. In the Pomeranian Bight, PAH and DBC concentrations strongly correlate with land-based discharge, while shipping emissions play a more prominent role in the Arkona Sea. The sea surface microlayer shows unique characteristics in DOM composition, with potential combustion products as an important source revealed by PAH and DOM analyses. Ultrahigh-resolution mass spectrometry identified combustion products, in the DOM pool, providing insights into anthropogenic impacts. This research contributes to a better understanding of the complex dynamics of thermogenic organic matter in coastal environments, highlighting the interplay between land-based sources, shipping emissions, and in-situ processes in the Baltic Sea region.

Comprehensive Screening of per- and Polyfluoroalkyl Substances (PFAS) in Food Contact Materials: Utilizing Combustion Ion Chromatography for Total Organic Fluorine (TOF) Analysis.

Per- and polyfluoroalkyl substances (PFAS) comprise thousands of fluorinated chemicals. They are of growing concern because many PFAS compounds are persistent and toxic. Food contact materials (FCM) containing PFAS pose multiple exposure pathways to humans, prompting twelve states to enact laws banning FCM with PFAS levels exceeding 100 ppm of TOF. While LC-MS is often used to measure targeted PFAS compounds, much of the total PFAS content in the sample may be missed. To understand organic fluorine content in samples more comprehensively, we developed a method using combustion ion chromatography (CIC) to measure TOF and extractable organic fluorine (EOF) in FCM. This technology utilizes combustion under an oxygen and argon atmosphere. All gaseous, acidic combustion products are collected in water, with ions separated on an ion exchange column and detected by conductivity. Total fluorine (TF) was measured by combusting 10-50 mg of FCM. Total inorganic fluorine (TIF) was measured by extracting cryo-ground FCM with water followed by direct injection to the IC system. TOF was then calculated by subtracting TIF from TF. EOF was determined by CIC after extracting analytes from the ground FCM using 80% methanol/20% acetonitrile. The Method detection limit (MDL) for TOF is 0.51 ppm, exceeding the sensitivity requirements of current state regulations. A comparison of EOF to TOF revealed that EOF constitutes less than 15% of the TOF in the FCM samples. TOF is a critical metric for assessing PFAS contamination in FCM, as targeted LC-MS approaches may miss much of the PFAS in the samples. We developed a sensitive and automated method to determine TOF and EOF in FCM. The method can be used to screen for PFAS in FCM, ensuring compliance with current regulations on PFAS contamination.

Unlocking landfill biogas potential: a feasibility study on sustainable energy in the UAE

Abstract Landfill biogas (LFB) projects present a promising solution for sustainable energy generation, yet their feasibility in arid climates remains largely unexplored. This study investigates the feasibility of generating biogas from landfill waste in the UAE, focusing on energy generation potential, economic viability, and environmental benefits. The study evaluates landfill biogas production using internal combustion engine and gas turbine technologies across three scenarios with varying methane content (40%, 50%, and 60% by volume). The results indicate that internal combustion engine technology demonstrates greater economic feasibility compared to the gas turbine technology, yielding a net present value of up to $83 million. Additionally, implementing landfill biogas to energy projects has the potential to power between 68,412 and 136,824 households while cutting greenhouse gas emissions by up to 66% compared to existing waste management practices. However, the relatively high levelized cost of energy underscores the need for policy interventions and financial incentives to enhance project viability. By addressing this critical knowledge gap, the study provides a replicable framework for optimizing waste-to-energy (WTE) systems in arid environments and contributes actionable insights to global renewable energy efforts.

On the Effectiveness of Aerosol Extinguishing Agents for Battery Vent Gases and Hydrogen

Abstract It is well known that Lithium-ion batteries in thermal runaway can emit gases with high hydrogen concentrations which, in case of delayed ignition, can cause a gas explosion. Aerosol suppression agents are sometimes used to suppress fires and/or prevent ignition of released gases in such situations. The agent has been studied for suppression of fires (diffusion flames), but less is known about the ability of such aerosols to inert highly reactive gas mixtures. In this paper, a commercially available aerosol suppression agent is mixed with a highly reactive gas mixture representing the gas composition from an NCA battery in thermal runaway as well as with pure hydrogen, and the effect on burning velocity is assessed based on OH-PLIF measurements on a Bunsen-burner type setup. The experiments were complemented by 1D flame simulations using a detailed chemical kinetics scheme including relevant combustible gases and the suppression agent. The results show that, although the agent is highly effective in gaseous form, evaporation of aerosols in the pre-flame-zone is prevented by the lower radiative fraction and results in higher burning velocity of hydrogen-rich mixtures. The local cooling induced by the evaporation of the aerosol in the flame leads to an increased flame area and thereby total burning velocity. This effect is further exaggerated by the preferential diffusion of hydrogen. Therefore, modification of the system is needed before applying for this purpose.

Full-Scale Fire Testing to Assess the Risk of Battery Electric Vehicle Fires in Underground Car Parks

Abstract Battery-only electric vehicle (BEV) fires have recently emerged as a significant safety concern in modern society, particularly when they occur in car parking spaces, where the consequences can be severe. While relatively few fatalities and injuries are reported, the associated economic losses are substantial. Car park structures present several challenges from a fire safety perspective, including high energy content, confined geometry, and difficulties in detecting and accessing to the fire’s origin due to smoke accumulation in spaces with limited ventilation and exits. This study investigates this fire hazard by conducting a full-scale fire test on a modern BEV in an instrumented test rig that simulates a segment of an underground car park. The data obtained were compared with standard fire curves to assess the hazard’s characteristics and with the data from a companion study to identify differences between BEV fires in underground and surface car parks. The primary difference observed was deflagration venting, which occurred shortly after the initial ignition of combustible gases accumulated beneath the ceiling, lasting until 13 min and 5 s. This phenomenon led to a rapid initial growth of the BEV fire, which burned more intensely for a shorter duration in the semi-enclosed configuration comparted to the open configuration. The enclosed fire recorded an average ceiling-jet temperature of approximately 1100°C and a peak incident heat flux exceeding 225 kW/m2. Additionally, thermal runaway within the lithium-ion battery cells was analysed to understand the adverse effects of the enclosed environment on thermal runaway propagation. This fire testing provides critical insights for developing firefighting strategies including the proper preparation of equipment and the design of fire protection systems. The principal findings could inform tactics for mitigating unforeseen fire risks and contribute to revisions of fire safety regulations.

Performance of Granulated Ti-Dopped Manganese Oxide Oxygen Carriers in Chemical Looping Processes

The cornerstone in the development of different applications of the Chemical Looping (CL) technology is the oxygen carrier material that transfers the oxygen. We evaluate the performance of manganese oxide doped with TiO2 to reinforce the release of molecular oxygen and regeneration at high temperatures (850–950 °C). Different manganese-titanium mixed oxides with mass fractions of titanium oxide from 0 to 50 wt.% were considered and prepared by granulation. The sample with 20 wt.%. TiO2 (MnTi_20) showed better oxygen release/regeneration capabilities than pure manganese oxide under similar conditions and was selected for further development. To evaluate the performance of MnTi_20, long tests (200 cycles) were carried out in a TGA to evaluate the chemical and mechanical stability of the sample. Additionally, MnTi_20 was tested in a batch fluidized bed reactor to evaluate its oxygen uncoupling capability and its reactivity with the main combustion gases (H2, CO, and CH4) as well as its fluidization properties. MnTi_20 is capable of regenerating Mn3O4 to Mn2O3 at 950 °C and maintains its reactivity with the redox cycles. No fluidization problems were encountered during almost 60 h of continuous fluidization, and a lifetime of 2500 h was estimated for this oxygen carrier.

Features of Hydrogen-Enriched Methane–Air Flames Propagating in Hele-Shaw Channels

Mixtures of hydrogen with common hydrocarbon fuels are considered viable for reducing carbon footprint in modern industry, power production, and transportation. The addition of hydrogen alters the kinetics and thermophysical properties of the mixtures, as well as the composition and properties of combustion products, requiring detailed research into the features of flame propagation in hydrogen-enriched hydrocarbon–air mixtures. Of particular interest are also the safety aspects of such fuels. In this paper, experimental results are presented on the premixed laminar flame propagation in channels formed by two closely spaced plates (Hele-Shaw cell), with the internal straight walls forming a diverging (diffuser) channel with the opening angles between 5 and 25 degrees. Methane–hydrogen–air mixtures with the hydrogen relative contents of 0%, 25%, and 50% and global equivalence ratio of unity were ignited by a spark near the closed narrow end of the channel. Experiments were performed with the gap width of 3.5 mm; video recordings were processed in order to determine the quantitative features of the flame front propagation (leading and trailing point coordinate, coordinates of the cusps, cell sizes and shapes). The main features of flame propagation (fast initial expansion, development of cellular flame, self-induced longitudinal oscillations) are obtained and compared to clarify the effect of hydrogen contents in the fuel and channel geometry (gap width, opening angle).

Research on the Thermal Runaway Behavior and Flammability Limits of Sodium-Ion and Lithium-Ion Batteries

Batteries are widely used in energy storage systems (ESS), and thermal runaway in different types of batteries presents varying safety risks. Therefore, comparative research on the thermal runaway behaviors of various batteries is essential. This study investigates the thermal runaway characteristics of sodium-ion batteries (NIBs), lithium iron phosphate batteries (LFP), and lithium-ion batteries with NCM523 and NCM622 cathodes. The experiments were conducted in a nitrogen-filled constant-volume sealed chamber. The results show that the critical surface temperatures at the time of thermal runaway are as follows: LFP (346 °C) > NIBs (292 °C) > NCM523 (290 °C) > NCM622 (281 °C), with LFP batteries exhibiting the highest thermal runaway critical temperature. NIBs have the lowest thermal runaway triggering energy (158 kJ), while LFP has the highest (592.8 kJ). During the thermal runaway of all four battery types, the primary gases produced include carbon dioxide, hydrogen, carbon monoxide, methane, ethylene, propylene, and ethane. For NCM622 and NCM523, carbon monoxide is the dominant combustible gas, with volume fractions of 35% and 29%, respectively. In contrast, hydrogen is the main flammable gas for LFP and NIBs, with volume fractions of 44% and 30%, respectively. Among these, NIBs have the lowest lower flammability limit (LFL), indicating the highest explosion risk. The thermal runaway characteristics of 50 Ah batteries provide valuable insights for battery selection and design in energy storage applications.

Combustion Behaviour of ADN-Based Green Solid Propellant with Metal Additives: A Comprehensive Review and Discussion

Solid propellants play a crucial role in various civil, scientific, and defence-related aerospace propulsion applications due to their efficient energy release, high energy density, low fabrication cost, and ease of operation. Ammonium dinitramide (ADN) has gained considerable attention as a potential oxidizer for green solid propellants due to its high oxygen content, significant energy density, non-toxicity, and non-polluting combustion products, leading to lower environmental impact. As ADN is a new desirable oxidizer in the field of solid propellants, understanding the practicality and viability of the use of ADN in composite solid propellants necessitates a thorough understanding of its chemical and thermal decomposition pathways in addition to its combustion characteristics in the presence of other ingredients. ADN is being explored as an alternative to the traditionally used ammonium perchlorate (AP), a toxic oxidizer containing chlorine (Cl). Additionally, AP monopropellants often suffer from moderate burning rates and poor mechanical strength. To address these limitations, researchers have explored the incorporation of metal additives, such as aluminium (Al), magnesium (Mg), and metalloid boron (B), to enhance the combustion performance and burn rate of AP. These metals not only act as energy-rich additives but also influence the combustion process through various mechanisms. The incorporation of metal additives into ADN has shown promising enhancements in the overall energetic performance of green solid propellants. This review aims to provide an in-depth analysis of the thermal decomposition of ADN and its combustion behaviour, along with the combustion of ADN-based solid propellants with metal additives. Finally, based on an extensive review of the existing literature, various research pathways for focused future collaborative efforts are identified to further advance ADN-based “green” solid propellants.

The Impact of Water-Based Fire Suppression Systems on Combustion Products

The Impact of Water-Based Fire Suppression Systems on Combustion Products

Construction and characteristic analysis of in-situ combustion production dynamic evaluation equation based on seepage difference of zones

The combustion-displacement relationship is complex of in-situ combustion (ISC), making it difficult to assess the combustion effect on the ground. In this work, combined with the characteristics of ISC production stage and oil-gas-water relative permeability relationship, the production dynamic evaluation equations are established, such as cumulative gas-liquid, cumulative oil-water and water cut. The determination method is obtained of oil saturation and gas saturation in the oil bank. It is found that the evaluation equation is exponential in the production rising and oil bank breakthrough stage, which is linear in the stable production stage. The obtained evaluation curves can fully reflect the stage characteristics of ISC. According to the evaluation equation, the oil saturation in the oil bank of the ISC test area in Xinjiang, China is calculated to be between 0.6 and 0.72, the temperature is roughly 110 °C, and the gas saturation is 0.09. The diagnosis believes that the test area has entered the oil bank breakthrough stage in the later stage. The established evaluation equations can directly use the actual production data to diagnose the characteristics of ISC production at different stages, and can quickly provide guidance for the adjustment of field measures.

Transformation of NO in Combustion Gases by DC Corona

Transformation of NO in Combustion Gases by DC Corona

Contrasting Summertime Trends in Vehicle Combustion Efficiency in Los Angeles, CA and Salt Lake City, UT.

Policy interventions and technological advances are mitigating emissions of air pollutants from motor vehicles. As a result, vehicle fleets are expected to progressively combust fuel more efficiently, with a declining ratio of carbon monoxide to carbon dioxide (CO/CO2) in their emissions. We assess trends in traffic combustion efficiency in Los Angeles (LA) and Salt Lake City (SLC) by measuring changes in summertime on-road CO/CO2 between 2013 and 2021 using mobile observations. Our data show a reduction in CO/CO2 in LA, indicating an improvement in combustion efficiency that likely resulted from stringent regulation of CO emissions. In contrast, we observed an increase in CO/CO2 values in SLC. While slower progress in SLC compared to LA may be partially due to a later adoption of vehicle emission regulations in Utah compared to California, differing driving conditions and fleet composition may also be playing a role. This is evidenced by increased CO/CO2 in LA during the COVID-19 pandemic, which led to faster driving speeds and changes to the fleet composition. Our results demonstrate the success of California's CO-reducing policy interventions and illustrate the impacts of traffic characteristics on vehicle combustion efficiency and air pollutant emissions.

A comparative evaluation of dark fermentative bioreactor configurations for enhanced hydrogen production.

Energy from renewable resources has been growing in popularity, which ultimately helps reduce emissions of greenhouse gases (GHGs) and contaminants. Since hydrogen (H2) has a higher combustion production of energy than hydrocarbon fuels, it has been identified as a clean, sustainable, and environmentally friendly energy source. There are several benefits to producing biohydrogen (bioH2) from renewable sources, including lower cost and increased sustainability. Among the bioH2 production processes, dark fermentation supports commercialization and scale-up for industrial applications. This paper considers the various bioreactors, such as anaerobic sequencing batch, continuous stirred, up-flow, fixed-bed, and membrane reactors, and their operational approaches for bioH2 production. This review paper also performs the bibliometric analysis method to identify historical and current developments in a particular field of reactor configuration studies. Furthermore, the main variables influencing reactor performance and methods for increasing process efficiency considering economic and environmental aspects are addressed. The results revealed that continuously stirred reactors are widely utilized for bioH2 production as a cost-effective reactor configuration. Moreover, the membrane bioreactors and fixed-bed reactors areyielded higher bioH2 performance than other configurations. Nevertheless, high energy consumption and costs have presented the need for further development of reactors. Consequently, future recommendations to solve the critical problems faced in reactor configurations, the gaps in the literature, and the points that need improvement were comprehensively reported.

Analyzing Antecedent Configurations of Group Emotion Generation in Public Emergencies: A Multi-Factor Coupling Approach.

To enhance emergency management and public opinion governance, improve the accuracy of forecasting group emotional responses, and elucidate the complex pathways of multi-factor coupling in the formation of group emotions, this study constructs a theoretical framework grounded in the social combustion theory. Through web scraping and text sentiment analysis, group emotional tendencies were measured in 40 public emergency cases from the past five years. Using the fuzzy-set qualitative comparative analysis (fsQCA) method, the study explored the coupling, configuration effect, and formation pathways of factors such as "burning substance", "accelerant", and "ignition" in the emergence of group emotions. The results reveal significant differences in the generation pathways of positive versus negative group emotion. Inter-group threat as a "burning substance" is more likely to trigger negative group emotion, while "accelerant" plays a pivotal role in shaping and guiding emotional responses. Notably, the government's response speed is critical for fostering positive emotions, whereas the emergence of rumors significantly contributes to the spread of negative group emotions. Additionally, the occurrence of stimulating events markedly increases the generation of negative group emotions. This study provides an important theoretical foundation and practical insights for the management and regulation of group emotions.

The Distribution of Rare Earth Elements in Coal Fly Ash Determined by LA-ICP-MS and Implications for Its Economic Significance

Coal fly ash represents a potential resource of some critical elements, including rare earth elements (REEs), which are retained and concentrated during coal combustion. Understanding the distribution and modes of occurrence of REEs within fly ash is vital to developing effective recovery methods and enhancing their economic value. Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) was applied to investigate the in situ elemental constituents of coal fly ash phases, including aluminosilicates, Ca-(Fe)-enriched aluminosilicates, Fe-oxides, and SiO2/Quartz, in order to explore the distribution of REEs in combustion products. LA-ICP-MS results show that V, Cr, and Nb are mainly enriched in Ca-Ti-enriched aluminosilicates with trace element concentrations referenced to the original fly ash composition. Lithium is primarily enriched in SiO2 glassy grains, followed by Ca, (Fe)-enriched aluminosilicates. Co, Ni, and Cu present a concomitant distribution in the Fe-enriched phases, such as Fe-oxides and Fe-enriched aluminosilicates. The chondrite normalized REE distribution patterns show characteristics of LREE enrichment and Eu-negative anomalies in most phases, while the REE patterns of SiO2 glassy grains have a distinct positive anomaly in Sm, Gd, and Dy, coupled with a deficiency in LREEs. Compared to feed coal, elements such as Li, V, Cr, Co, Ni, and Nb and REEs are enriched 2~10 times in various phases of fly ash, with REEs notably concentrated six times higher in aluminosilicates and Ca-Ti-enriched aluminosilicates than the original coal. This study further discusses the feasibility, calibration principles, and advantages of using LA-ICP-MS to determine REE distribution, as well as the economic implications of REE extraction from coal fly ash.

A Comprehensive Exploration of Biomass Gasification Technologies Advancing United Nations Sustainable Development Goals: Part I

The pursuit of sustainable energy sources on a worldwide scale is a crucial and pressing matter, with the United Nations Sustainable Development Goals (UNSDGs) offering a comprehensive framework for properly addressing this challenge. This two-part paper provides an overview of the various technologies now available for the process of biomass gasification. Compared to other renewable energy sources, which have undergone significant technological advancements in recent years, the field of biomass conversion is still relatively new. Keeping up with the newest breakthroughs becomes increasingly crucial as new conversion techniques are rapidly being created. In the thermochemical conversion process called ‘biomass gasification’, biomass solid source materials are degraded or incompletely burned in an oxygen-free or oxygen-deficient high-temperature atmosphere, resulting in the production of biomass gas. Part I delves into different biomass gasification techniques, including upstream, gasification and downstream processes, highlighting their importance in transforming biomass into clean and combustible gases.

The feasibility study of transfer arc plasma pyrolysis system for petrochemical wastes: Hydrogen production from Antar, OTD, and Tar.

One of the best and most advanced methods for disposal of urban, hospital, industrial, and other hazardous waste is to convert waste into combustible gases in reactors based on plasma arc technology. Also used for renewable energy generation, this technology involves thermal treatment without a combustion process; therefore, the waste is completely decomposed into simple molecules in a near vacuum environment almost devoid of Oxygen at elevated temperatures. The present research uses a thermal transferred arc plasma reactor to conduct a feasibility study on the pyrolysis of three types of wastes: Antar, Orthotoluenediamine (OTD), and Tar. To this end, three experiments were conducted, and the effective parameters involved in preparing and producing common gaseous raw materials and products, such as hydrogen, and their production amounts were examined. The outcome demonstrates that there are no remnants of spent catalyst waste following the plasma pyrolysis process, confirming the feasibility of complete conversion. The findings of this study revealed that plasma waste reactors could generate recycled energy in the form of renewable fuel free of toxic gases and vapors released from conventional waste incinerators and create negligible amounts of environmental pollutants.

INVESTIGATION OF THE EFFECT OF COMPRESSION RATIO AND DIFFERENT FUELS ON CO2 EMISSIONS

Air pollution caused by the exhaust gases of internal combustion engines threatens the future of these machines. CO<sub>2</sub>, which is normally non-polluting but causes global warming, has necessitated limiting the emission of this gas. Therefore, reducing CO<sub>2</sub> production at its source is the most effective method. In particular, the use of fuels with a high H/C ratio, such as compressed natural gas (CNG), significantly reduces CO<sub>2</sub> emission. In this study, the contribution of different mechanisms to CO<sub>2</sub> reduction was examined by combining both thermal efficiency and fuel types. Experiments were conducted with gasoline and CNG fuels at different compression ratios and mixtures. When CNG was used instead of gasoline in stoichiometric mixture, CO<sub>2</sub> emission was reduced by 23% at a brake mean effective pression (BMEP) of 5 bar. Approximately 8% less CO<sub>2</sub> was produced when operating with a lean mixture (λ = 1.6) instead of a stoichiometric mixture for both fuels. In the experiments conducted with CNG, CO<sub>2</sub> emission decreased by 1.5% when compression ratio was changed from 10.5 to 14. However, as the compression ratio increased, the volumetric efficiency decreased at constant BMEP. Therefore, the efficiency coefficient, which takes into account the effect of volumetric efficiency, was defined and it was observed that thermal efficiency could increase up to 7% by increasing the compression ratio from 10.5 to 14. Finally, when comparing CNG fuel with a high compression ratio (ε = 14) and ultra-lean mixture, and gasoline fuel with a low compression ratio (ε = 10.5) and stoichiometric mixture, it was observed that CO<sub>2</sub> emission decreased by around 33%.