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The direct utilization of heavy and extra-heavy crude oils presents a formidable challenge due to their inherent physical and chemical properties such as high C/H ratio, extremely high viscosity and density, low APIo, super low mobility, high asphaltene and impurity (Fe, Ni, Co, S, N, etc.) contents. To tackle these problems cost-effectively, we have proposed and established a novel technique, distinct from conventional hydrotreating, for catalytic partial upgrading of extra heavy crudes with co-fed methane and a multi-functional catalyst. This technique has been further optimized using lab-scale batch reactors (100 mL, 300 mL), bench-scale and pilot-scale fixed bed reactors with their processing capacity of 250 mL/day and 20 L/day, respectively. The feasibility, stability, and profitability of this technique have been successfully verified using all these facilities and a wide variety of feedstock. Yet, further scale-up is necessary to advance this technique towards commercialization in industry. In this study, a pilot-scale prototype unit (processing capacity of 1 barrel/day) was designed and manufactured based upon the previous achievements, and a bitumen sample recovered from the Steam Assisted Gravity Drainage (SAGD) process was chosen as a typical extra heavy crude for the upgrading. A 30-day upgrading has been conducted smoothly without clogging and a liquid yield of 96.7 % was observed with remarkable enhancements in product quality. The notable decreases in density, viscosity, TAN, asphaltene content, and sulfur content were confirmed and consistent with previous results. A low olefin content implies excellent stability and compatibility of the liquid product. Additionally, a preliminary TEA (Techno-Economic Assessment) and LCA (Life-Cycle Analysis) have been conducted and the beneficial features of this novel technique have been confirmed with higher profitability, lower cost, and lower carbon footprint. This study further consolidates the advantages of this promising technique as a cost-effective and environmentally friendly alternative to hydrotreating for processing extra heavy crudes.

Pd nanocatalyst supported on amine-functionalized mesoporous graphitic carbon nitride (Pd/NH2-mpg-C3N4) was investigated for dehydrogenation of formic acid. The catalyst was analyzed and tested to investigate the effect of amine functionalization on hydrogen generation from formic acid. Pd nanocatalyst was dispersed uniformly on NH2-mpg-C3N4 without agglomeration. The turnover frequency value of Pd/NH2-mpg-C3N4 was 1870 h−1, which was higher than that of Pd/mpg-C3N4 because of the amine functionalization. The Pd/NH2-mpg-C3N4 was also tested to investigate the effect of various reaction conditions (formic acid concentration, sodium formate concentration, and reaction temperature) on hydrogen generation from formic acid. Formic acid concentration negatively affected the catalytic activity, whereas sodium formate concentration positively affected it. Reaction temperature significantly affected the catalytic activity. The apparent activation energy of the Pd/NH2-mpg-C3N4 catalyst was 60.7 kJ mol−1, and a hydrogen generator with the catalyst exhibited high conversion efficiency at an elevated temperature. Consequently, a hydrogen generator with Pd/NH2-mpg-C3N4 is suitable for polymer electrolyte membrane fuel cell systems.

Mordenite-ZSM-22 composite zeolite is prepared by the physical mixing. The structure, pore properties, acid properties and diffusion properties of samples are characterized by the means of XRD, N2 physical adsorption-desorption, SEM, TEM, NH3-TPD, Py-IR, and ZLC. The pore properties and acid properties of mordenite-ZSM-22 composite zeolite can be efficiently modulated by changing mass ratio of mordenite and ZSM-22. In n-C12 hydroisomerization reaction, Pt/HMZ-x displays great capacity in modulate n-dodecane isomers distribution (mono-branched i-C12, multi-branched i-C12, terminal branched i-C12 and central branched i-C12), these results are ascribed to that these composite zeolite catalysts combined the topology structure advantage of mordenite and ZSM-22. When reaction temperature is 280 °C, the ratio of mono-branched i-C12 selectivity to multi-branched i-C12 selectivity (SMB/SMTB) of Pt/HZSM-22, Pt/HMZ-1, Pt/HMZ-3, Pt/HMZ-5 and Pt/HMOR were 37.64, 15.04, 5.48, 5.20 and 1.47, respectively. The ZLC diffusion experiment results indicate that low isomer selectivity of Pt/HMOR is due to its poor diffusivity. On the contrary, Pt/HZSM-22 favors the diffusion of reactants and has better catalytic performance.

To obtain the ignition performance of an integrated inclined combustor, we perform an experimental study on the ignition performance of an inclined combustor under various ignition positions, inlet flow rates, and fuel air ratios (FARs). The experimental results reveal the following. 1) During ignition at I1, the inclined combustor presents the best ignition performance. 2) The forward propagation process of flame along the swirler's inclined direction easily realizes flame propagation, whereas the backward flame propagation process in the swirler's inclined direction is difficult to achieve; forward and backward flame propagations exhibit evident differences. 3) The diffusion propagation of swirl flames at the ignition head is the main means swirl flames are generated at the nonignition head. 4) During the ignition process, the combustion intensity increases with the increase in FAR and decreases with the increase in inlet flow rate. 5) The successful ignition time decreases with the increase in inlet flow rate and FAR.

In diesel engines, nitrogen monoxide (NO) is the predominant component of nitrogen oxides (NOx) emissions. However, when transitioning to methanol/diesel dual-fuel operation, even with a small percentage of methanol replacing diesel energy (e.g. 10 %), the concentration of nitrogen dioxide (NO2) increases significantly, becoming comparable to that of NO. This study employs multi-dimensional computational fluid dynamics (CFD) modeling to reproduce this NO2/NOx surge ratio phenomenon and investigates the underlying mechanism driving the surge in NO2 emissions, an area insufficiently explored in existing literature. By comparing CFD simulations with and without the NO+HO2↔NO2 + OH reaction in the chemical mechanism, the results reveal that the surge in NO2 concentration disappears when this reaction is invalidated, while engine efficiency, combustion phasing, and overall NOx emissions remain largely unchanged. This indicates that the NO+HO2↔NO2 + OH reaction is the primary contributor to the sudden increase in the NO2/NOx ratio. Further analysis during the main combustion stage shows that the diesel spray splits into two distinct regions after impinging on the bowl boundary, with one region deep within the bowl and the other near the squish region. During the late oxidation stage, the diffusion flame directed towards the deep bowl area remains a high-temperature zone with a high concentration of NO, whereas the flame near the squish region evolves into a low-temperature zone due to effective mixing with the low-temperature methanol/air mixture. In these low-temperature regions, almost all NO formed during the main combustion stage is converted to NO2 during the late oxidation stage, leading to the observed NO2/NOx ratio surge. Methanol oxidation contributes HO2 radicals, which facilitate the NO-to-NO2 conversion. Consequently, the low-temperature oxidation of methanol outside the high-temperature region does not lead to thermal ignition but is instead responsible for the rare occurrence of the NO2 surge.

Investigating the impact of ethanol and TiO2 on the performance and emission characteristics of diesel engines running on a blend of ethanol and castor biodiesel is the primary goal of this study. The nanoparticles of ethanol, biodiesel, and TiO2 diesel fuel were combined at several concentrations. Diesel, B10, B20, B30, B10E10T, B20E10T, B30E10T, B10E20T, B20E20T, and B30E20T were among the various fuels that were investigated. The physiochemical properties of all the sample fuels were assessed, including density, pour point, cloud point, fire point, flash point, and kinematic viscosity. Following this, other engine performance indicators, such as torque, power, and fuel-consumption, were examined. Studies were also carried out on the properties of emissions, including CO, CO2, HC, and NO. Peak braking power and engine torque were found for each fuel under investigation at around 2750 and 2500 rpm, respectively. The addition reduced the brake-specific fuel consumption for B10E20T by 7.41 % while increasing the braking engine's torque and power by 8.64 and 3.86 %, respectively, in compared to blends without the TiO2 additions. When compared to diesel, the exhaust emission data without the addition of TiO2 revealed a decrease in CO and HC emissions but an increase in CO2 and NO emissions. On the other hand, using ethanol blend reduced NO emissions. According to the overall findings, diesel engine performance, combustion characteristics, and exhaust gas emissions were enhanced averagely by 7.43 % when a certain ratio of ethanol, biodiesel, and TiO2 additives (B10E20 + 50 ppm) was used.

Traditional denitrification methods for coal-fired power boilers face challenges like reduced flue gas temperature at low loads, decreased efficiency of existing denitrification devices, and increased ammonia consumption. Biomass, a renewable energy source, has proven effective for denitrification in medium to high-temperature ranges. To improve denitrification efficiency at low loads, this study focuses on optimizing re-burning denitrification of biomass by nitrogen-impregnated of corncob at room temperature. Investigating the effects of nitrogen impregnation and washing on biomass re-burning denitrification reactivity within 550–950 °C, the study finds that denitrification efficiency improvement is not caused only by surface-covered urea or washing. Nitrogen impregnation enhances biomass pyrolysis, releasing more CO, HCN, and NH3 products, thereby enhancing NO reduction during denitrification. Additionally, nitrogen impregnation boosts nitrogen-containing functional groups such N-6 on biomass char surfaces during the re-burning process, improving denitrification efficiency. The maximum denitrification efficiency of the nitrogen impregnated sample reached 97.52 % at 950 °C, while it reached 76.51 % at 650 °C when the coated urea was washed. Furthermore, chlorine and alkali metal contents in biomass notably decrease after nitrogen-impregnation and washing, optimizing biomass combustion conditions for furnace protection. This study offers theoretical insights for promoting and applying biomass denitrification techniques.

Solar-thermal biomass conversion using both direct and indirect concentrated solar thermal energy is an emerging approach that combines two renewable energy sources to enhance energy efficiency and enable sustainable processing. This review paper provides a comprehensive examination of various types of solar concentrators and reactors, showcasing the diversity of available technologies and their roles in enhancing conversion efficiency. The paper focuses on the reported studies on biomass solar-thermal conversion through gasification and pyrolysis processes, critically discussing the integrated process operating conditions and the quality of the products (biofuels). These analyses affirm the technical viability, emphasizing the relatively low energy investment required for pyrolysis compared to the total energy output from biomass feedstock. This points to the substantial promise of solar thermal biomass conversion as a sustainable and efficient renewable energy solution. The conclusion highlights the importance of ongoing research, technological advancements, and policy support to fully realize the potential of solar-thermal conversion of biomass.

A major challenge for upgrading hydrothermal liquefaction biocrude into sustainable aviation fuel is the presence of inorganic material. Unlike commercial crude oil or biofuel from energy crops, excessive amounts of contaminants such as salt, water, and ash in biocrude oil from hydrothermal liquefaction can cause catalyst deactivation during hydroprocessing, decreased distillation efficiency, and equipment fouling from alkali deposits. Therefore, efficient removal of these impurities in HTL biocrude oil is essential. This work investigated a novel 3-stage pretreatment process, removing water, salt, and ash without chemicals, to produce a HTL biocrude oil precursor suitable for hydroprocessing. The influence of water to oil (W:O) ratio, temperature, and time on desalting efficiency was determined. After pretreatment, 81% of salt was removed, reducing total salt content to

This work aims to investigate the structural behaviour of asphaltene under mechanical stress using ball milling. Asphaltene samples were collected and separated from Kuwait export crude using n-heptane and subsequently ball milled for up to 24 h. X-ray diffraction was used to provide an insight into asphaltene macrostructure properties, which subsequently utilised to determine crystallite parameters. The results showed that the mechanical stress has a great influence on these structural parameters, with an increase of the aromatic sheet's inter-layer distance from 3.6 Å to 3.9 Å. While the height of stacked aromatic sheets per cluster and the number of stacked aromatic sheets per cluster decreased from 24.6 Å to 9.3 Å and 8 to 3.2, respectively. A significant increment in the aromaticity value was also observed after the ball milling experimentations, indicating mechanical stress induces cyclisation and aromatisation. The XRD profiles of the higher milling time samples reveals a high background intensity. This suggests a formation and/or increasing the proportion of highly disordered materials. In addition, the effects magnitude on asphaltene crystal parameters between the mechanical stress against heat stress was compared. The results showed core structural parameters are more sensitive to mechanical stress over heat stress.

The catalytic decomposition of methane (CDM) is a hydrogen and nanostructured carbon production process with minimal CO2 emission. Among the transition metal-based catalysts (e.g. Ni, Fe, Co, etc.), Ni-based catalysts are most widely studied due to the higher catalytic activity in decomposing methane. However, the limited lifespan of the catalyst makes it unsuitable for practical applications. Effective methane decomposition catalysts should be designed to optimize both reaction efficiency and catalyst lifetime. A Ni/CeO2 catalyst, developed in previous studies, Co was added to promote low-temperature (< 700 °C) activity manipulating the redox property of Co. Among the prepared catalysts with varying Ni:Co ratio, the methane conversion rate of the Ni8Co2/CeO2 catalyst was approximately twice that of the Ni10/CeO2 catalyst, confirming its excellent low-temperature activity. The reaction rate of Ni8Co2/CeO2 catalyst was 4.38 mmol/min∙gcat at 600 °C with WHSV of 36 L/gcat∙h. In terms of characteristics of carbon products, Raman spectroscopy analysis revealed that the carbon grown on the catalyst surface exhibited high crystallinity, with D-G band ratio (ID/IG) of 1.01. The fresh and used catalyst samples were characterized by TEM, XPS, XAS, and other methods to analyze the parameters affecting catalytic activity.

Economical production of lignin-based jet fuel (LJF) can improve the sustainability of sustainable aviation fuels (SAFs) as well as can reduce the overall greenhouse gas emissions. However, the challenge lies in converting technical lignin polymer from biorefinery directly to jet fuel in a continuous operation. In this work, we demonstrate a simultaneous depolymerization and hydrodeoxygenation (SDHDO) process to produce lignin-based jet fuel from the alkali corn stover lignin (ACSL) using engineered Ru-HY-60-MI catalyst in a continuous flow reactor, for the first time. The maximum carbon yield of LJF of 17.9 wt% was obtained, and it comprised of 60.2 wt% monocycloalkanes, and 21.6 wt% polycycloalkanes. Catalyst characterization of Ru-HY-60-MI suggested there was no significant change in HY zeolite structure and its crystallinity after catalyst engineering. Catalyst characterizations performed post the SDHDO experiments indicate presence of carbon and K content in the catalyst. K content presence in the spent catalyst was due to K+ ion was exchanged between lignin solution and HY-60 while carbon presence validated the SDHDO chemistry on the catalyst surface. Tier α fuel property testing indicates that LJF production using SDHDO chemistry can produce SAF with high compatibility, good sealing properties, low emissions, and high energy density for aircraft.

Coal gasification slag (CGS) presents significant challenge to the green and low-carbon development of the coal gasification industry due to its limited utilization restriction. In this study, cationic surfactant DTAB was used with kerosene to formulate an emulsion collector. The flotation results showed that, the increase in collector dosage could significantly improve the combustible recovery. At an optimal collector dosage of 10 kg/t, an increased DTAB ratio could significantly diminish the ash content of flotation concentrates and improve flotation precision. Through flotation dynamics experiments and fitting of the Fuerstenau upgrading curve, it confirmed that the entrainment of fine-grained particles with high ash content is the primary contributor to high ash content in flotation concentrates. Combined with FTIR spectroscopy, XPS and other analysis method, it validated that the surfactant effectively reduced the dispersed particle size of the agent, the increased contact angle of RC surface also improved hydrophobicity and improved particles hydrophobic agglomeration strength. Molecular dynamics simulation further illuminated that the surfactant covered part of the hydrophilic sites on the residue carbon (RC) surface and influenced the electrostatic interaction. The research results have important theoretical significance for perfecting the flotation theory of CGFS.

This study introduces Cold-processed Lignin in (M)ethanol Oil (CLEO/CLiMO), a novel biofuel technology derived from the alcohol-fractionation of lignin at ambient temperatures, offering a sustainable alternative to conventional marine fuels. The production process achieved solid loadings of up to 60 wt% lignin and a volumetric energy density 39 % higher than pure alcohols. Lignin concentrations above 30 wt% promoted colloidal stability through the proposed formation of a spanning network of lignin aggregates, associated with a 100-fold increase of viscosity. Additionally, we observed a decrease in the radius of gyration of lignin particles from 2.5 to 2.7 nm at 30 wt% to 1.1–1.3 nm at 60 wt% following a transition from globular to elongated random coil shaped particles. This was accompanied by a twofold increase in the partial specific volume of lignin, suggesting a reduction in packing efficiency. The study highlights CLEO's potential as a sustainable shipping fuel alternative, combining favorable fuel properties with a simple and scalable production method.

The development of highly effective bifunctional catalysts for n-hexadecane hydroisomerization is still essential to produce second-generation biodiesel. Herein, a Pt-Pd/ZSM-22-G (abbreviated as Pt-Pd/Z22-G) bimetallic catalyst was prepared by employing a room temperature electron reduction (RTER) method with glow discharge as the electron source. As a contrast, a series of Pt/Z22-H, Pd/Z22-H and Pt-Pd/Z22-H catalysts were prepared by the conventional hydrogen reduction method. The Pt-Pd/Z22-G catalyst reveals more exposed metal sites, larger CMe/CH+ values and an enhanced distribution of Pt-Pd(111) facets compared with the Pt/Z22-H, Pd/Z22-H and Pt-Pd/Z22-H catalysts. These modifications are originated from the stronger electron interactions and the smaller metal nanoparticles because of the effects of highly energetic reducing electrons. The n-hexadecane hydroisomerization results show that the iso-hexadecane yield over the Pt-Pd/Z22-G catalyst is 82.9%, which is the highest among four investigated catalysts in this work. This phenomenon occurs because more exposed Pt-Pd(111) facets and larger CMe/CH+ ratios are beneficial for the adsorption and hydrogenation of iso-alkene intermediates at metal sites to increase the iso-alkanes yield based on density functional theory (DFT) calculations. Furthermore, the iso-alkanes yield over the Pt-Pd/Z22-G catalyst also keeps steady after long-term tests for 120 h because of the limited metal aggregation and carbon deposition.

This paper proposes a new method of pulverized coal gasification using high-temperature tertiary air in a cement precalciner, in which an external hanging gasifier is added nearby. A full-scale model is established and simulated for the entrained flow gasifier. During the gasification process, the global reaction mechanism is used to model the release and reactions of volatiles from pulverized coal, and a particle surface reaction model is employed to calculate the fixed carbon content. The mechanism by which reducing gas reacts with NO is also considered. The results of the velocity, temperature, gas composition, NOx emissions, calorific value, volatile conversion ratio and char burnout ratio, are achieved in the simulation. The results show that the volatile conversion ratios were close to 100%, and the carbon conversion ratios ranged from 27.97% to 62.76% among all the tested conditions. The concentrations of NO at the outlet of the gasifier were 109, 98, 75, 91, 87, 76, and 90 mg/m3 separately in 7 conditions. These values are significantly lower than those of complete combustion. However, the addition of raw meal had the best temperature control effect, leading to a significant decrease in thermal NOx production and no side effects on the stability of the production line.

This paper investigates the impact of ammonia (NH3) kinetics on the ignition mechanism of dimethyl ether (DME), a topic minimally addressed in existing literature, by utilizing a hypothetical NH3 representative species with identical thermodynamic properties and atomic mass to actual NH3, yet remaining inert during reactions, thereby distinguishing the kinetic effects from thermal and dilution influences. Kinetic analysis via zero-dimensional (0D) idealized reactor calculations shows that DME ignition in the ammonia-air atmosphere is still primarily governed by peroxy kinetics, yet ammonia kinetics significantly modify the ignition reaction pathways of DME. Specifically, during the low-temperature oxidation preparation stage, ammonia oxidation yields nitrogen-containing species that (e.g., NO2, NO, NH2), through CN reactions, reduce the flux in the keto-hydroperoxides (KET) formation pathway in DME. The NH3 oxidation pathway also competes for OH radicals, which disfavors DME ignition. The rapid decomposition of KET during the low-temperature heat release (LTHR) stage emits a substantial amount of OH radicals, increasing temperature and causing the shift from chain branching to chain propagation pathways in DME oxidation, leading to significant CH2O production and decreased reaction reactivity. This shift also promotes the hydrogen‑oxygen reaction mechanism, transitioning the controlling mechanism from the KET mechanism to the hydrogen peroxide (H2O2)-loop mechanism. The LTHR stage further enhances CN reactions in the CH3 pathway, favoring NO production and increasing the flux of NO and HO2 reactions releasing OH radicals. Moreover, the ammonia oxidation pathway, characterized by HO2 radical consumption and concurrent OH radical and H2O2 generation, significantly influences the H2O2-loop system, resulting in a diminished reaction flux in the H → HO2 → H2O2 mechanism during the thermal ignition preparation stage. In summary, these findings underscore the significance of CN interactions in the NH3/DME ignition process and highlight the necessity of considering CN interactions in mixed fuels between ammonia and other high-reactivity fuels (e.g., diesel with higher carbon atoms), for accurate ignition prediction.

The world's energy requirement is rising continuously due to an increase in the global population and demand for better quality of life. Fossil fuels are non-renewable, and their consumption poses global warming. Biomass-derived fuels are sustainable alternatives to fossil fuels as they are originated from renewable feedstocks. The present study investigates the production of biocrude from hydrothermal liquefaction of Canadian agricultural straws at identical conditions. Further, barley straw is found to be promising; therefore, hydrothermal liquefaction process parameters are varied for barley straw to maximize the biocrude yield with lower oxygen content. At optimum reaction conditions, the existence of carboxylic acids, phenols, aldehydes, and ketones is identified in the produced biocrude. Further, the recyclability study of the aqueous phase is attempted to explore the possibility of reusing this phase. The physicochemical characteristics of the biocrude (main product) and by-products (hydrochar, non-condensable gases, and aqueous phase) are also studied to identify the suitable areas of applications. The present experimental study demonstrates a detailed understanding of the liquefaction behavior of Canadian barley straw for biocrude production with an immense potential to co-refine in the existing petroleum refineries.

Developing highly efficient single-atom catalysts (SACs) for electrocatalytic carbon dioxide reduction reaction (CO2RR) is a promising approach to promoting carbon neutrality. However, challenges such as low activity, selectivity and high costs hinder industrial scaling, attributed to the lack of innate activity or insufficient transition metal (TM) active site density in current catalysts. Therefore, the focus of CO2RR research remains on developing SACs with intrinsic catalytic activity, high TM coverage and cost-effectiveness. This study presents the design of carbon-based materials with ultra-high TM coverage (TM2C12) (TM = Mo, Ru, Rh, W, Re, Os and Ir) as electrocatalyst SACs for CO2RR using density functional theory calculations. Among these materials, W2C12 (W represents tungsten) demonstrates superior selectivity and catalytic activity for CO2RR to carbon monoxide (CO) products with overpotentials of 0.45 V and a W coverage of up to 71.84 wt%. To further enhance its catalytic activity, non-metallic (NM) coordination modification (NM = B, N, O, P doping and C vacancy) was explored on W2C12. The results indicate that N-doped W2C12 (N-W2C12) can significantly improve selectivity and catalytic activity, achieving an extremely low overpotential of 0.34 V. This research offers valuable insights into designing SACs with high activity, selectivity and stability for CO2RR and other catalytic reactions.

The limited solubility of lignin in commonly used solvents poses a challenge for its depolymerization into high-value monomers. This paper investigates the solubility of alkali lignin in water, methanol, ethanol, acetone, 1,4-dioxane, and their binary solution, and examines their impact on lignin depolymerization. The distribution of depolymerization products was correlated with the chemical structure changes in various solvent. Among the solvents tested, water-acetone mixtures demonstrated exceptional solubility for alkali lignin (95.24%) and provide the highest yield of bio-oil and phenolic monomers. The enhanced solubility of guaiacol units in acetone, combined with the addition of water in the co-solvent system dramatically improved the solubility of alkali lignin. Moreover, formic acid donated hydrogen protons to facilitate lignin depolymerization and prevented the repolymerization of unstable intermediates. Optimal reaction conditions were achieved at 300 °C for 120 mins using a mixed solvent composed of water, acetone, and formic acid in a ratio of 5:5:1 (v/v/v), corresponding to the highest yield of bio-oil with 81.45 wt%, the lowest yield of residue with 6.20 wt%, and a phenolic monomer content of 57.48%. Furthermore, this co-solvent system revealed satisfactory adaptability for converting various lignin into phenolic monomers.

One-step transesterification between ethylene carbonate (EC) and ethanol (EtOH) can effectively prevent the formation of azeotropes in the synthesis of diethyl carbonate (DEC) / ethyl methyl carbonate (EMC). However, owing to the influence of volume and electronic effects of EtOH molecules, the catalytic activity is insufficient. In this study, we propose an on-line synthesis technique for catalysts and prepare a unique heterogeneous alkali catalyst, PS-(NR3OH)EG. This technique simplifies the catalyst preparation process and protects it from exposure to water and carbon dioxide in the air. The active sites of PS-(NR3OH)EG are derived from the product ethylene glycol (EG). PS-(NR3OH)EG exhibits excellent catalytic performance in promoting EC and EtOH transesterification. The physicochemical properties of PS-(NR3OH)EG are analysed, and the reaction conditions are optimized. The results indicate that PS-(NR3OH)EG has superior catalytic activity and stability compared to the similar previously reported catalysts. Notably, after continuous reaction in a fixed-bed reactor for 500 h, PS-(NR3OH)EG maintain its initial catalytic activity. This study provides theoretical and experimental guidance for catalyst preparation and transesterification reaction process design.

This study examines the effects of laser heating on the ignition and critical combustion characteristics, such as temperature and burn time, of individual iron particles. It provides time-dependent temperature profiles of laser-ignited particles across a broad spectrum of particle size distributions and oxygen concentrations obtained from experiments, which are a useful database for further development and validation of iron particle combustion models. The herein reported datasets significantly complement those existing in the literature. In the current study, the raw data are thoroughly re-evaluated using refined approaches. For the experimental canonical configuration of single iron particle combustion, an ignition system based on laser heating provides several advantages in overcoming temperature field uncertainties and facilitating controlled environments for optical diagnostics. Despite the inherent uncertainties in laser heating, associated with non-uniform intensity profiles and particle size variations, this study addresses the critical question of how these uncertainties affect in situ measurements of particle temperature and time to reach peak temperature. This study, conducted using a numerical model, reveals a dependence of the particle temperature after laser heating on particle size. However, this dependence does not significantly impact the key parameters of iron-particle combustion, such as the maximum temperature and burn time of the laser-ignited iron particle. The study also presents a comparison between the simulated particle temperature histories and those derived from two-color pyrometry measurements for a wide range of particle size distributions and oxygen concentrations. Notably, by implementing a laser-heating sub-model into an iron particle combustion model, assuming external-diffusion-limited oxidation only up to stoichiometric FeO, the temperature evolution up to the maximum temperature is reasonably captured for a wide range of particle sizes (20–53μm) and oxygen volumetric fractions (14–21vol% O2 mixed with N2). However, with increasing oxygen concentration, the external-diffusion limited model significantly overestimates the heating rate and subsequently the maximum particle temperature.

Rotating detonation rocket engines are propulsive devices employing detonation waves moving circumferentially around an annular channel that consume axially fed propellants. Theoretically, this provides benefits with respect to combustion pressure gain and thermodynamic efficiency when compared to deflagration-based combustors. To facilitate size scaling of these devices, the relationships between geometric parameters, performance, and wave dynamics have been investigated with gaseous methane-oxygen propellant. Empirical relations were derived between combustor geometry, fueling conditions, and engine operation, as well as correlation to thermodynamic parameters calculated with chemical kinetics codes. The radius of curvature effects were explored in annular combustors having outer diameters of 25 mm, 51 mm, and 76 mm with a fixed gap width of 5 mm. The injectors were scaled to have same oxidizer-to-fuel injector port area ratio, impingement distance, and injector-to-gap area ratio. Larger combustors had higher wave counts during operation at a given mass flux and equivalence ratio. Combustor axial pressures were found to be more dependent on propellant mass flux and equivalence ratio than geometry. Mass flux and the inner-to-outer radius ratio, the latter of which was related to other geometric ratios, dictated the operating mode transition thresholds and the number of resulting waves, respectively.

Gas-phase hydrogen combustion is ubiquitous in industrial processes, and the associated surface kinetics on heat-resistant alloys plays a crucial role in designing efficient low-carbon technologies. We conducted new temperature programmed reduction experiments to determine the reducibility of materials following an oxidation cycle. These experiments were modeled using a thermoconsistent multi-site microkinetic model for H2 heterogeneous oxidation on Inconels, which was validated against literature experiments. This competitive adsorption model considers iron bulk content, hydrogen spillover and subsurface oxygen migration on hydrogen surface oxidation kinetics. New X-ray diffraction experiments confirmed the postulated crystallographic structures in the Inconel samples, suggesting their presence on the surface scale. The phenomenological model was coupled with several state-of-the-art gas-phase oxidation mechanisms to assess gas/surface reactions interaction as a function of material and temperature. The results reveal a complex interaction in which surface removes H radicals from the gas-phase, while the Bradford (H2+OH) reaction converts OH into H2O, promoting water adsorption on Inconel. This interaction was found to give rise to gas-phase thermokinetic oscillations. The model predicts a non-monotonous effect of reactor area-to-volume ratio on reactivity and emphasizes the impact of Inconel composition on product selectivity. Overall, the multi-site model provides new insight into the contrasting reactivities among active sites, bridging the gap between material science and heterogeneous combustion modeling.

Hydrogen's ability to enhance carbon neutrality in combustion processes puts forward the use of hydrogenated fuels, both in the form of fuel and an energy carrier as a potential decarbonization solution. However, because of the nature of hydrogen, blending it with hydrocarbons causes crucial structural changes in the flame structure, including higher flame propagation velocities and higher flame temperatures, decreased instantaneous flame thickness, and increased risks of flame flashback and an increasing potential of NOx emissions due to higher flame temperatures. These attributes encourage a thorough examination of hydrogenated blends of hydrocarbon fuels. Using lean premixed fuels is another technique to achieve efficient and cleaner combustion. However, due to the problem of flame instability in lean premixed combustion, forecasting the design points in terms of flame attributes is critical for better combustor designs.In this study, conical (Bunsen type) lean premixed turbulent flames of hydrogenated natural gas-air mixtures are experimentally studied. Through chemiluminescence measurements of the OH* and CH* radicals and laser-induced Mie scattering, lean natural gas-air premixed flames are examined with subsequently increasing hydrogen addition rates up to 20% by volume and keeping the premixture velocity constant. The obtained data is utilized for exploring the dynamics of the turbulent flame front. The main turbulent premixed flame parameters we identified relate to the instantaneous and average topology of the flame such as the turbulent flame brush thickness and flame height. We also inferred global combustion parameters like the turbulent flame propagation speed from the experimental findings.

This numerical study is designated to comparatively investigate premixed CH4/air jet flames from bluff-body (BB) and non-BB (NBB) burners in the coflow of hot exhaust gas. Specifically, traditional combustion (TC) from BB burner (BB-TC), MILD combustion (MC) from BB burner (BB-MC), and NBB burner (NBB-MC) under varying coflow temperatures (TC) and oxygen concentrations (YO2, C) are considered. The flow field, combustion reactions, temperature rise, heat release, along with reaction zone, and pollutant emissions are thoroughly investigated. The findings underscore the feasibility of achieving MILD combustion using the BB burner. Remarkably, the small recirculation zone generated by the BB enhances entrainment and mixing, leading to superior combustion stability and reduced CO emission in the BB-MC case compared to the conventional NBB-MC case. Moreover, the BB-MC case exhibits a higher peak temperature, reaction rate, and heat release rate than the NBB-MC case, albeit with slightly higher NO emission. When compared to the BB-TC case, NO emission from both the BB-MC and NBB-MC cases are significantly lower, particularly under relatively low TC and YO2, C conditions.

Compared to traditional hydrocarbon fuels, ammonia presents significant challenges as a fuel, including high ignition energy, low reactivity, slow flame propagation, and high NOx emissions, which hinder its use as a renewable fuel. Blending ammonia with fossil fuels like natural gas improves its combustion reactivity and helps mitigate CO2 emissions. However, there is still much to understand about the complex dynamics of ammonia and its blends with hydrocarbons. Key areas such as reaction kinetics mechanisms, ignition properties, flame propagation behaviors, and methods for controlling combustion performance under various conditions require further elucidation. This paper reviews recent advancements in experiments and numerical simulations aimed at developing stable, and low-emission combustors for ammonia-fired power generation. Recent burner and flame configurations, including non-swirling jets, single-stage swirl burners, two-stage burners, and newly developed double-swirl burners are analyzed for their flame stability and pollutant emission potential when firing ammonia and ammonia blends. Chemical kinetic modeling of ammonia and its blends plays a crucial role in understanding combustion behavior and pollutant emissions, particularly for NOx. However, there are challenges in predicting NOx emissions accurately, with significant disparities among different models. High-fidelity numerical simulations using detailed and skeletal mechanisms, direct numerical simulation, and large eddy simulation, have helped uncover crucial operational conditions affecting combustion and pollutant emissions, such as combustor pressure, air dilution, wall cooling, fuel/air mixing, and fuel blending. Nonetheless, the accuracy of chemical kinetic models and their integration into turbulent flow simulations remain critical limitations for numerical simulations of ammonia combustion.

The aviation sector’s significant contribution to greenhouse gas emissions has spurred interest in sustainable aviation fuels (SAF) as a means to mitigate environmental impact. This study examines user diversity in the public acceptance of power-to-liquid aviation fuels (eSAF), exploring varying attitudes towards the environment, flying, and eSAF adoption. Through a quantitative survey of a representative German sample, three distinct segments emerged: the Environment-Centered Approvers, the Flying-Centered Approvers, and the Skeptical. The Environment-Centered Approvers prioritize environmental concerns and perceive moral obligations to use eSAF for climate protection. In contrast, the Flying-Centered Approvers prioritize the continuation of flying with reduced environmental impact, while the Skeptical exhibit a more cautious and uncertain stance towards eSAF adoption. The study highlights the importance of tailoring communication strategies based on the unique motivations and concerns of each subgroup to effectively promote eSAF adoption.

Turbulent combustion of jet flames in a hot diluted coflow of combustion products has been studied across a range of jet Reynolds numbers for propane, ethylene, and an ethylene-propane blend as fuels. The study revealed a transition from conventional autoignitive combustion to a regime of Moderate or Intense Low-oxygen Dilution (MILD) combustion, which is characterized by a nearly invisible flame. The flames studied are luminous at low jet velocities and become MILD at higher jet velocities. Planar Laser-Induced Fluorescence (PLIF) of formaldehyde (CH2O), a key intermediate species in hydrocarbon combustion, is combined with CH*-chemiluminescence imaging and Rayleigh scattering to investigate the phenomena. The transition to MILD combustion is found to accompany a broadening of the formaldehyde region, indicating a broader low-temperature reaction zone. As the transition is approached, the appearance of holes in the chemiluminescent front is also observed. Correspondence between the location and structure of these holes with regions of formaldehyde in the flame are illustrated. These regions are proposed to be signatures that precede the transition to a fully MILD flame. In other words, the transition to MILD combustion begins at a local level and the MILD region spreads to engulf the entire combusting mixture. Scalar gradients were imaged to further unravel the local turbulence/chemistry interactions that yield the MILD inception. The measured scalar gradients were found to be commensurate with scalar gradients obtained from chemical kinetic simulations at the stoichiometric mixture fractions, while being an order of magnitude larger at other locations; this suggests that the inception of MILD combustion occurs near the stoichiometric region.

The combustion of ammonia requires, for most energy conversion systems, a combustion promoter such as hydrogen to guarantee the start-up, stability and combustion efficiency. Partially cracked ammonia (PCA) can provide sufficient hydrogen concentrations to enhance the burning velocity in comparison with pure ammonia. However, little work exists on the use of PCA blends operating under relevant turbulent conditions. To that end the outwardly propagating spherical flame configuration was employed to determine the laminar and turbulent flame propagation characteristics of PCA (NH3/(H2+N2)) and corresponding binary (NH3/H2) mixtures across various turbulent combustion regimes. First, PCA and ammonia-hydrogen blends exhibit similar flame propagation rates under various turbulent intensities, even for the laminar case. The highest turbulent burning velocity was observed at leanest conditions, as opposed to laminar flames which exhibited highest flame speed at conditions above stoichiometry. Under rich conditions, no substantial flame enhancement due to turbulence was measured irrespective of the hydrogen content. This lack of flame enhancement under turbulent conditions is attributed to the effect of preferential diffusion with good agreement observed with trends in measured Markstein numbers. The normalized turbulent flame speed is dominated by the enhanced molecular diffusivity afforded by the presence of hydrogen up to 15 % enrichment, prior to decreasing upon further hydrogen addition under lean and stoichiometric conditions. This ‘bending’ phenomenon may be the contribution of several factors including; the transitioning between combustion regimes associated with low Damköhler numbers (Da) and flame thickening; merging of flamelets due to the presence of ammonia enhancing wrinkling; and combined changes in laminar burning velocity and preferential diffusional behavior. Furthermore, good agreement for turbulent flame speed is observed with a correlation that includes the influence of turbulent stretch (Ka) and non-equidiffusion (Le), with the agreement reducing with decreasing chemical to turbulent time scale ratios (Da << 1).

In the present study, LESs of a modeled typical combustion zone of a 1000 MW S-CO2 coal-fired boiler using a hybrid flamelet/progress variable model are conducted for the first time. In the hybrid model, both the fuel-N from volatiles and char are considered, and two progress variables are used for major species and NO, respectively. The combustion and NO formation characteristics at different regions are qualitatively and quantitatively investigated. The results indicate that the mixture of primary air and secondary air, the high-temperature wall as well as the adjacent flame can promote the pulverized coal combustion (PCC) and NO formation. In addition, the effects of wall temperature and flue gas recirculation on PCC and NO formation are investigated. The results show that compared with the supercritical H2O boiler, a slight rise of 2.08% and 3.05% for temperature and NO production can be observed in the supercritical CO2 boiler due to a higher wall temperature; flue gas recirculation with a recirculation rate of 27% can effectively reduce the production of NO by 57.6% in the supercritical CO2 boiler.

Cities continue to expand along with the growth of population, while our mobility systems often fail to meet the demands for social, environmental and economic sustainability. The second industrial revolution enabled the extensive use of private vehicles, posing various challenges to the sustainability of such systems. Luckily, several best practices aiming at tackling this issue have been identified in the past, facilitating progress towards sustainability. Nowadays, this progress is strongly supported by the call for cities to develop Sustainable Mobility Plans (SUMPS), which stands as an opportunity for best practices to be implemented in coordination with relevant policies. This research identifies the best practices that promote a modal shift, while it investigates their alignment with the strategy that enhances public transport services, encourages active mobility and disincentivizes private vehicle usage. Therefore, the presentation of these practices, introduces a set of initiatives that under aforementioned strategy promotes a modal shift. Furthermore, through the identification of best practices in various locations, several insights and inferences are drawn, providing useful guidance.

The chemical looping gasification of plastics (CLGP) is a process that offers an innovative solution for transforming post-consumer waste plastics into high-value products. The process utilizes a co-current moving bed reducer reactor with iron-titanium-based oxygen carriers to gasify plastic feed and generate syngas autothermally. Its distinguishing feature is its ability to operate over a wide range of feed loadings and co-injection of mixed plastic species without any performance losses. Isothermal bench-scale experiments reveal a syngas purity of ∼95 %, aligning with the thermodynamic simulations. The moving bed reactor facilitates a deeper reduction of the oxygen carriers to the Fe+FeTiO3 phase, leading to the high syngas purity, which is then verified with additional TGA, XRD, and SEM analysis. For an autothermal operation of CLGP process, an active material content of 20 % is found to be sufficient to satisfy the kinetic and thermodynamic constraints. Further integration with downstream production of H2 is presented and compared to a steam gasification process. The process integration simulations show that the CLGP process outperforms the steam gasification system in terms of Cold Gas Efficiency (CGE), Effective Thermal Efficiency (ETE), and H2 yield. CO2 emissions are impressively reduced by ∼30 % in the CLGP system over that in the steam gasification system due to its ability to autothermally operate the process, unlike the highly endothermic steam gasification process.

The open jet flame in hot co-flow (JHC) has been frequently utilized for fundamental investigations of Moderate or Intense Low-oxygen Dilution (MILD) combustion due to its controllable conditions and relatively easy measurement capabilities. However, practical MILD combustion must take place within a combustor that is enclosed. Therefore, it is necessary to examine the similarity and disparity of combustion characteristics between two flame configurations. This issue is addressed currently. Specifically, we investigate the flow mixing, ignition, and combustion, as well as emission characteristics of non-premixed and premixed JHC and cylindrical furnace (FUR) flames at various values of the environmental temperature (Te) and central jet Reynolds number (Re). For the open non-premixed flames, we employ both previous single-tube JHC (SJHC) combustor and presently modified JHC (MJHC) one that uses the same nozzle configuration as the FUR burner. It is revealed that significant differences occur in flow, combustion and emission characteristics between the SJHC and FUR cases. On the other hand, both non-premixed and premixed MJHC configurations exhibit high similarity to the corresponding FUR cases in terms of upstream flow mixing and combustion features. Moreover, different CO and NOx emissions result from open JHC and close furnace flames due to different post-combustion configuration and residence time. Accordingly, future experiments on non-premixed MJHC and premixed JHC flames are highly recommended for better understanding practical MILD combustion.

We used crowdsourced data in Alaska and the literature to develop a light-duty electric vehicle model to help policymakers, researchers, and consumers understand the trade-offs between internal combustion and electric vehicles. This model forms the engine of a calculator, which was developed in partnership with residents from three partner Alaskan communities. This calculator uses a typical hourly temperature profile for any chosen community in Alaska along with a relationship of energy use vs. temperature while driving or while parked to determine the annual cost and emissions for an electric vehicle. Other user inputs include miles driven per day, electricity rate, and whether the vehicle is parked in a heated space. A database of community power plant emissions per unit of electricity is used to determine emissions based on electricity consumption. This tool was updated according to community input on ease of use, relevance, and usefulness. It could easily be adapted to other regions of the world. The incorporation of climate, social, and economic inputs allow us to holistically capture real world situations and adjust as the physical and social environment changes.

The urgent call for environmentally sustainable methods and bio-based products to meet the 17 global Sustainable Development Goals (SDGs) by 2030 is particularly crucial in Africa, notably Nigeria. The challenge lies in integrating a systemic approach, viewing the world holistically, and prioritizing environmental preservation alongside economic development. Addressing pressing issues like climate change, biodiversity loss, habitat preservation, poverty, hunger, and disease requires concurrent focus on cleaner energy sources, improved air and water quality, efficient resource conservation, fair food distribution, and accessible healthcare. Stringent regulations, vigilant oversight, and effective enforcement are imperative to curb emissions, pollution, and waste. Simultaneously, directing research toward sustainable bio-production, environmental restoration, and turning oil palm resources into value-added bio-products via integrated algal/oil palm biorefineries is crucial. Exploring biochemical applications in pharmacy is part of this pursuit. An evaluation of Nigeria's oil palm mill life cycle, scrutinizing practices and potential, was conducted. Nigeria's pathway to a sustainable oil palm industry, addressing electricity crises, fossil fuel dependency, waste management, and fostering sustainable cities, involves converting waste to wealth via integrated algal/oil palm residue biorefineries. Achieving this could mean building new biorefineries or revamping existing ones through a hybrid system. Despite unrealized policies, Nigeria can address energy and waste issues while harnessing bioenergy, biopharmaceuticals, and biochemicals through an integrated algal/oil palm refinery.

This study proposed an integrated intelligent control system in one municipal solid waste incineration power plant to improve the system's control accuracy, economic performance and environmental impact, including the intelligent combustion, intelligent denitrification, intelligent desulfurization and intelligent soot-blowing control subsystems. The precise detection and adjustment of the key operational parameters was achieved by integrating these modules into the existing distributed control system. A comparative analysis of the operation data between pre-optimization and post-optimization states was conducted to assess the changes in the key operational and economic parameters. The results indicate that the introduction of the intelligent control module can significantly improve the system stability and parameter control accuracy, thereby enhancing the economic efficiency of the waste incineration power plant and reducing the operation workload and the pollutants emissions. Specifically, the standard deviations of main steam flowrate and pressure decreased by 45.1 % and 60.7 %, respectively. Furthermore, the consumptions of the ammonia water and lime slurry were reduced by 38.2 % and 23.2 %, respectively, while the auxiliary power consumption rate declined by two percentage points, and the power generation per ton of waste increased by 4.2 %. These improvements not only strengthen the economic benefits but also effectively reduce the pollutants emissions.

This work introduces a numerical multiphase model for multi-component mixtures, utilizing tabulated data for physical and transport properties across a spectrum of conditions from near-vacuum pressures to supercritical states. The property data are derived using Perturbed Chain Statistical Associating Fluid Theory (PC-SAFT), vapor-liquid equilibrium (VLE) calculations, entropy scaling methodologies, and Group Contribution (GC) methods. These techniques accurately reflect the thermodynamic behaviors of real fluids, avoiding the empirical estimation of Equation of State (EoS) input parameters. Implemented in OpenFOAM, the fluid dynamics solver is designed to address the three-dimensional Navier-Stokes equations for multi-component mixtures. The methodology integrates operator splitting to manage hyperbolic and parabolic steps distinctively. Hyperbolic terms are solved using the HLLC (Harten-Lax-van Leer-Contact) solver with temporal integration performed via a third-order Strong-Stability-Preserving Runge–Kutta (SSP-RK3) method. Viscous stress tensor contributions in the momentum equation are handled through an implicit velocity correction equation, while parabolic terms in the energy equation are explicitly solved. The simulation efficiency is further enhanced by adaptive Local Time Stepping and the Immersed Boundary (IB) method, which addresses interactions between the fluid and solid boundaries. Turbulence is resolved using the Wall Adaptive Large Eddy (WALE) model. Applied to high-pressure diesel fuel spray injections into non-reacting (nitrogen) gas environments, the model has been validated against Engine Combustion Network (ECN) data for the Spray-C configuration, featuring a fully cavitating multi-hole orifice. Results demonstrate that the model achieves accurate predictions across a broad range of tested conditions without the need for tuning or calibration parameters.

High-pressure pipeline storage presents a promising method for widespread and efficient hydrogen transfer. However, challenges arise in mitigating pressurized hydrogen leakage due to hydrogen embrittlement issues associated with conventional pipeline materials. Experimental findings indicate that pressurized hydrogen is prone to spontaneous combustion, even at relief pressures as low as approximately 2 MPa - well below the permissible pipeline pressure in most countries. Despite this, there remains a lack of consensus regarding the mechanism of spontaneous ignition from high-pressure hydrogen leakage, and current research in this area is deemed insufficient. This study aims to analyze and discuss the presumed mechanisms of spontaneous ignition comparatively, review the progress in the study of spontaneous ignition of hydrogen in high-pressure leakage based on diffusion ignition theory, and statistically compare and discuss the influences of significant factors existing in pipelines (e.g., macro size factors and internal structure) and/or pipe failures (e.g., rupture factors) on spontaneous ignition. It is hoped that this article will provide scholars involved in the development of hydrogen energy and the theories of spontaneous combustion with a systematic understanding of these phenomena.

As climate change intensifies, the global push for de-carbonization highlights the urgent need for carbon-free fuels. Ammonia (NH3), with zero carbon emissions and a notable ability as a hydrogen carrier (17.8 % by weight), has emerged as a promising candidate for a net-zero economy. Over the past decade, substantial research has been devoted to the combustion of gaseous ammonia. However, liquid ammonia has several key advantages over gaseous ammonia, including high energy density, cost efficiency, system simplicity, and a high octane number. Despite these benefits, challenges such as high NOx emissions, low combustion stability, significant latent heat, and susceptibility to flash boiling necessitate further exploration. This article comprehensively reviews the current state of research on liquid ammonia as a fuel, covering experimental and numerical efforts regarding fundamental fuel properties, spray characteristics, flame stabilization, combustion performance, and emissions. By systematically summarizing the recent advancements in liquid ammonia spraying and combustion, this review aims to serve as a cornerstone for future experimental and numerical studies and industrial applications, providing a reference for the research and utilization of liquid ammonia combustion.

The jet-in-hot-coflow is a canonical combustion setup, which has been used in several studies to study Flameless/MILD combustion and auto-ignition of fuels. However, the NOx and CO emission measurements from these combustion setups were not possible due to the entrainment of laboratory air and a lack of a well-defined physical system limit. These limitations have been overcome by a new enclosed jet-in-hot-coflow setup. The combustor was operated by injecting a mixture of CH4-Air in the central jet, and the coflow comprised of hot products from CH4-Air combustion in burners upstream. The coflow composition was further controlled by adding diluents such as N2 and CO2. Measurements were done using stereoscopic particle image velocimetry, suction probe gas analysis, thermocouples, and chemiluminescence imaging. Increasing central jet velocity and equivalence ratio led to lower NOx and a reaction zone that enlarged and shifted downstream. The reduction in NOx emission was attributed to the returning mechanism. Adding CO2 and N2 as diluents in the coflow resulted in a longer combustion zone and reduced temperatures in the combustion chamber, leading to decreased NOx production and increased reburning. These experiments provide relevant flowfield and emissions data for modelers and help characterize combustion regimes such as Flameless/MILD.

This paper explores the potential of oxy-fuel direct-fired supercritical carbon dioxide (sCO2) power cycles, proposing them as a promising strategy towards achieving near-total carbon capture while utilizing existing fossil fuels. It offers insights into the future of CO2- and sCO2-diluted combustion science and combustor design, supported by a review of the current state of the art. The paper is divided into four sections: chemical kinetics and the development of chemical mechanisms, numerical simulations tools, combustion and laser ignition experimental efforts, and the current state of the art and perspectives of combustor design efforts. The paper underscores the need for additional experimental measurements to validate chemical mechanisms, numerical simulations, and combustor design to advance understanding of CO2 and sCO2-diluted combustion science. The authors advocate for increased collaboration within the scientific community and the development of standardized lab-scale burners and combustor geometries to facilitate comparison and validation as well as reduce development costs. The paper emphasizes that significant research and development efforts are crucial to ensuring the safety, reliability, and efficiency of CO2 and sCO2-diluted combustion processes and combustor design. The knowledge and strategies applicable to conventional gas turbines may not directly transfer to sCO2 cycles, necessitating dedicated research efforts to advance this promising technology towards widespread adoption.

This work investigates the effects of fuel temperature and injection timing on ammonia direct injection in an optical engine using a multi-hole injector. Flash-boiling may occur over various engine-relevant conditions due to ammonia’s high vapor pressure. This phenomenon impacts spray characteristics and, in severe cases, facilitates cavitation inside the nozzle. Both fuel temperature and injection timing (i.e., ambient conditions during injection) impact the intensity of flash-boiling during fuel injection. Therefore, this work varies fuel temperature (from 320K to 388K) and injection timing (from −60CADaTDC (crank angle degrees after top dead center) to −6CADaTDC) to assess their impact on injection mass flux, discharge coefficients, and macroscopic spray characteristics using an ammonia injection pressure of 200bar. For this purpose, the injection mass is measured by analyzing exhaust gas compositions during engine operation with ammonia injections but without combustion. In addition, diffuse background illumination (DBI) images capture the liquid phase of the fuel spray to characterize spray behavior. The findings reveal that increasing fuel temperature decreases ammonia’s injection mass by up to 12.8% but has little impact on discharge coefficients for late injection timings and high in-cylinder pressures. However, discharge coefficients decrease by up to 17.4% (from 0.58 to 0.48) for early injection timings if fuel temperatures are high. The individual sprays of the 6-hole GDI injector may collapse into a uniform spray at high-density conditions without flash-boiling or under strongly flash-boiling conditions. The findings clarify the impact of ammonia’s high vapor pressure on injection mass and prove the relevance of different spray collapse mechanisms in ammonia direct injection engines.

A macro-thermobalance (macro-TGA) was applied to investigate the steam co-gasification characteristics of the chars produced from Huainan coal (HN), two types of biomasses, sawdust (SD) and wheat straw (WS), and coal-biomass blends at 900–1200 °C under rapid heating conditions. The gasification reaction kinetics were determined by the homogeneous reaction model (VM), shrinking core model (SCM) and random pore model (RPM), and the optimal model was selected by deviation calculation. The results show that the char gasification reactivity increased with the increase of temperature. The promotion effect of biomass semi-coke on coal char mainly occurred in the stage when the carbon conversion rate was greater than 0.5, which is mainly attributed to the migration of active AAEMs to the surface of coal char to catalyze the gasification reaction in the later stage. However, with the increase in temperature, this promoting effect is weakened due to the increasing influence of mass transfer effects over chemical rate control, and increased volatilization of the inorganic species. The RPM model is suitable for describing the coal char gasification process, while the SCM was the model that best fitted the biomass semi-coke and coal/biomass blends, which elucidates the kinetic mechanisms governing the gasification process.

Combining stratified lean-burn techniques with methanol offers a promising path to achieving high efficiency and low emissions in direct-injection spark-ignition (DISI) engines. This work compares the stratified and homogeneous-stratified lean-burn characteristics of methanol/gasoline fuels on a DISI engine. Combustion and emissions characteristics under two stratified lean-burn strategies were investigated. The results indicate that compared to double-injection stratified lean-burn (DISL), single-injection stratified lean-burn (SISL) leads to more timely combustion, which deteriorates more slowly as the excess air ratio increases. Using M20 fuel with SISL achieves a higher tolerance for air dilution. At the same excess air ratio, SISL results in higher maximum in-cylinder pressure and combustion temperature, but lower exhaust temperature. The economic zone for SISL occurs with M40 fuel at λ = 1.3–1.6, whereas DISL's economic zone is within λ = 1.1–1.3. When λ is below 1.5, SISL produces higher hydrocarbon (HC) emissions but lower nitrogen oxides (NOx) emissions. However, as λ exceeds 1.5, HC emissions from DISL increase sharply while NOx emissions decrease significantly. The particle concentration from SISL is at least an order of magnitude higher than that from DISL, with particle size distribution forming a unimodal curve centered around accumulation mode particles. Conversely, DISL exhibits a quasi-bimodal distribution.

The abrupt rise in demand for conventional fuels has become a major cause for concern despite their increasing depletion. That's why the pyrolysis process to make plastic pyrolysis oil (PPO), can be used to prepare fuel as an alternative fuel. The batch pyrolysis reactor was fabricated to produce plastic pyrolysis oil (PPO) from locally sourced grocery bags made of high-density polyethylene (HDPE). The purpose of this study was to thoroughly analyze the performance and emission characteristics of an engine running on up to 15 % PPO-diesel blended fuel. Then, the experimental data obtained from a single-cylinder, four-stroke engine with five distinct speeds ranging from 1000 to 3500 rpm were utilized to undertake energy, exergy, and sustainability assessments. The results showed that DPO5 had a maximum brake power of 1.92 kW at 2500 rpm. At 3500 rpm, the engine achieved a thermal efficiency of 47.44 % for diesel and 51.6 % for DPO5 blended fuel. Furthermore, DPO15 produced the least quantity of CO2 at all engine speeds. DPO5 has the highest sustainability index, 1.52 at 2500 rpm. As a result, our research found that a low-level PPO-diesel fuel blend may be effectively injected into diesel engines without requiring any modifications.