Search Results (644)

Heavy-duty vehicles dominate global freight movement and primarily rely on fossil-derived diesel fuel. However, fluctuations in crude oil prices and evolving emissions regulations have prompted interest in alternative powertrains to enhance fleet energy resiliency. This study paired real-world operational data from a large commercial fleet with high-fidelity vehicle models to evaluate the potential for replacing diesel internal combustion engine (ICE) trucks with alternative powertrain architectures. The baseline vehicle for this analysis is a diesel-powered ICE truck. Alternatives include ICE trucks fueled by bio- and renewable diesel, compressed natural gas (CNG) or hydrogen (H₂), as well as plug-in hybrid (PHEV), fuel cell electric (FCEV), and battery electric vehicles (BEV). While most alternative powertrains resulted in some payload capacity loss, the overall fleetwide impact was negligible due to underutilized payload capacity for the specific fleet considered in this study. For sleeper cab trucks, CNG-powered trucks achieved the highest replacement potential, covering 85% of the fleet. In contrast, H₂ and BEV architectures could replace fewer than 10% and 1% of trucks, respectively. Day cab trucks, with shorter daily routes, showed higher replacement potential: 98% for CNG, 78% for H₂, and 34% for BEVs. However, achieving full fleet replacement would still require significant operational changes such as route reassignment and enroute refueling, along with considerable improvements to onboard energy storage capacity. Additionally, the higher total cost of ownership (TCO) for alternative powertrains remains a key challenge. This study also evaluated lifecycle impacts across various fuel sources, both fossil and bio-derived. Bio-derived synthetic diesel fuels emerged as a practical option for diesel displacement without disrupting operations. Conversely, H₂ and electrified powertrains provide limited lifecycle impacts under the current energy scenario. This analysis highlights the complexity of replacing diesel ICE trucks with admissible alternatives while balancing fleet resiliency, operational demands, and emissions goals. These results reflect a US-based fleet’s duty cycles, payloads, GVWR allowances, and an assumption of depot-only refueling/recharging. Applicability to other fleets and regions may differ based on differing routing practices or technical features such as battery swapping. Full article

This review examines the combustion characteristics of hydrogen-enriched natural gas with a specific focus on residential appliances, where safety, efficiency, and emission performance are critical. Drawing on experimental studies, numerical simulations, and regulatory considerations, the paper synthesizes current knowledge on how hydrogen addition influences flame stability, flashback phenomenon, thermal efficiency, pollutant formation, and flame geometry. Results across cooktop burners, boilers, and other domestic systems show that moderate hydrogen blending not only can reduce CO and CO₂ emissions and enhance combustion efficiency but also can increase burning velocity, diffusivity, and flame temperature, thereby elevating flashback and NOx risks. The review highlights the blending limits, design adaptations, and operational strategies required to ensure safe and effective integration of hydrogen into residential gas infrastructures, supporting its role as a transitional low-carbon fuel. Full article

The article presents an extensive review of modern technological solutions for pulverized coal combustion, with emphasis on combustion modifiers and biomass co-firing. It highlights the role of coal in the national energy system and the need for its sustainable use in the context of energy transition. The pulverized coal combustion process is described, along with factors influencing its efficiency, and a classification of modifiers that improve combustion parameters. Both natural and synthetic modifiers are analyzed, including their mechanisms of action, application examples, and catalytic effects. Special attention is given to the synergy between transition metal compounds (Fe, Cu, Mn, Ce) and alkaline earth oxides (Ca, Mg), which enhances energy efficiency, flame stability, and reduces emissions of CO, SO₂, and NO_x. The article also examines biomass-coal co-firing as a technology supporting energy sector decarbonization. Co-firing reduces greenhouse gas emissions and increases the reactivity of fuel blends. The influence of biomass type, its share in the mixture, and processing methods on combustion parameters is discussed. Finally, the paper identifies directions for further technological development, including nanocomposite combustion modifiers and intelligent catalysts integrating sorption and redox functions. These innovations offer promising potential for improving energy efficiency and reducing the environmental impact of coal-fired power generation. Full article

Sulfur dioxide (SO₂) is a colorless, pungent gas that is a significant contributor to air pollution, with well-documented environmental and health impacts. It is emitted both naturally (e.g., in volcanic activities) and anthropogenically (e.g., fossil fuel combustion, sulfuric acid production, papermaking, and wine preservation). Inhalation represents the primary route of human exposure, particularly in urban and industrial settings. Acute SO₂ exposure can lead to airway irritation, laryngospasm, bronchoconstriction, pulmonary edema, and death in severe cases. Chronic exposure, even at low concentrations, can contribute to the development of pulmonary and extrapulmonary diseases. Despite its classification as a hazardous air pollutant, a comprehensive understanding of dose-response relationships, exposure thresholds, and mechanisms of toxicity for SO₂ remains limited. This review synthesizes current knowledge on environmental sources, exposure routes, mechanisms of toxicity, and health impacts of SO₂, highlighting findings from epidemiological, toxicological, and mechanistic studies. We also discuss gaps in knowledge regarding SO₂, approaches to monitor and assess SO₂ exposure in ambient environments, the emerging role of SO₂ as a gasotransmitter, and areas where further research is needed to better understand health risks and support evidence-based public health decision-making. Full article

Background. Determining the cause and manner of death in scenes involving multiple and putrified bodies found in the same environment is a real challenge for forensic pathologists. While common scenarios include fires, vehicle crashes, and natural disasters, one of the most common causes is drug intoxication or poisoning, and the scene must be carefully evaluated based on circumstantial evidence. Carbon monoxide (CO) (also called “the silent killer”) remains one of the leading agents capable of producing simultaneous fatalities. In multi-body scenes, distinguishing between homicide–suicide, double suicide, and accidental deaths adds further complexity. The aim of this study is to highlight the limitations of toxicological and pathological investigations in advanced putrefaction and to emphasize the role of scene investigation in the interpretation of suspected CO-related deaths. Methods. The authors report a case of suspected CO intoxication involving two bodies in an advanced stage of decomposition recovered from the same room. The scene investigation, coupled with the presence of a malfunctioning combustion source, raised suspicion of CO exposure; however, analytical interpretation was severely constrained by the altered condition of biological samples. Results. Advanced decomposition magnifies these challenges. Putrefactive changes can mimic traumatic injuries, hide hypostasis, and compromise both macroscopic and microscopic evaluations due to autolysis and gas formation. Toxicological investigations are frequently hindered by the degradation or absence of key biological matrices such as blood, cavity fluids, or vitreous humor, rendering carboxyhaemoglobin quantification unreliable or impossible. These limitations may lead to incorrect medico-legal conclusions. Conclusions. Determining the cause and manner of death in complex multi-body scenes requires careful evaluation of circumstantial evidence and scene investigation, particularly when advanced decomposition compromises biological analyses and toxicological interpretation. Full article

The passage of a premixed stoichiometric methane-air flame through a hole in an internal barrier in a Hele-Shaw channel with one end closed was studied experimentally. It was found that for the same initial conditions, a flame propagating from the closed channel end can either pass through the hole in the barrier or be extinguished. The passage probability dependence on the hole width was found to be non-monotonic, with a sharp maximum at small hole sizes, followed by a minimum at intermediate sizes and a gradual increase as the blockage ratio tends to zero. The nature of this non-monotonic behavior of flame passage probability was analyzed by analyzing the flame front histories leading to flame passage or extinction at the same experimental parameters. A likely cause of this behavior is the development of an alternating-direction gas jet blowing from the hole due to the pressure difference between the channel compartments. Cooling of hot combustion products with cold channel walls can cause a pressure drop in the closed channel part and development of a reverse (open-to-closed compartment) gas jet affecting the approaching flame. Therefore, flame passage or extinguishment is a feature of the whole two-chamber system, rather than an intrinsic flame property. Full article

To improve traditional cement manufacturing, which generates a large amount of greenhouse gases, blending calcareous green algae and fly ash as cement replacement materials is expected to achieve nearly zero carbon emissions. As a calcareous green alga, Halimeda macroloba is a significant producer of biogenic calcium carbonate (CaCO₃), sequestering approximately 440 kg of carbon dioxide (CO₂) per 1000 kg of CaCO₃, with CaCO₃ production reported in relation to algal biomass. To assess the new low-carbon/low-waste cement production process, the proposed scenarios (2 and 3) are validated via Python-based modeling (Python 3.12) and Aspen Plus^® simulation (Aspen V14). The core technology is the pre-calcination of algae-derived CaCO₃ and fly ash from coal combustion, which are added to a rotary kiln to enhance the proportions of tricalcium silicate (C₃S) and dicalcium silicate (C₂S) for forming the desired silicate phases in clinker. Through the lifecycle assessment (LCA) of all scenarios using SimaPro^® (SimaPro 10.2.0.3), the proposed Scenario 2 achieves the GWP at approximately 0.906 kg CO₂-eq/kg clinker, lower than the conventional cement production process (Scenario 1) by 47%. If coal combustion is replaced by natural gas combustion, the fly ash additive is reduced by 74.5% in the cement replacement materials, but the proposed Scenario 3 achieves the GWP at approximately 0.753 kg CO₂-eq/kg clinker, lower than Scenario 2 by 16.9%. Moreover, the LCA indicators show that Scenario 3 has lower environmental impacts on human health, ecosystem, and resources than Scenario 1 by 24.5%, 60.0% and 68.6%, respectively. Full article

Ammonia is considered as a promising hydrogen carrier and a carbon-free fuel. Methods for improving ammonia combustion characteristics often involve its co-firing with more reactive fuels (natural gas, biofuels, etc.). Among the natural gas components, ethane is second most abundant. Therefore, the development of detailed chemical–kinetic mechanisms that accurately consider the interactions between ammonia and each component of natural gas is very important. Such mechanisms must be based on experimental data obtained under a wide range of conditions. In this work, NH₃/C₂H₆/O₂/Ar blends were studied in JSR (φ = 0.5–2.0, p = 1 atm, τ = 1 s, T = 800–1300 K) and in a shock tube (p = 7.3–8.6 atm, T = 1260–1590 K). Additionally, the structure of premixed flames was investigated (φ = 0.8–1.2, p = 1–5 atm). Eleven recently published detailed chemical–kinetic mechanisms were tested. The model Shrestha-2025 was updated to achieve better agreement with the entire set of experimental data. The effect of p and φ on intermediate species concentration was analyzed. Ammonia and ethane consumption pathways were also examined. Full article

In the steel industry, reheating furnaces are a significant source of carbon emissions. Co-firing natural gas and ammonia in reheating furnaces reduces carbon emissions and mitigates ignition difficulties and the limited flammability range of ammonia. This research develops a three-dimensional model for combustion, fluid dynamics, and heat transfer in a reheating furnace to investigate slab heating and emission with a natural gas/ammonia blended fuel. Numerical results demonstrate that, under constant calorific value conditions, the average temperature of the discharged slab decreases following ammonia blending, with the greatest temperature differential of 110 K achieved at a 10% ammonia blending ratio. Moreover, as the ammonia blending ratio increases from 0 to 40%, the mass fraction of CO first rises and subsequently declines, ultimately decreasing by 18%. Meanwhile, the CO₂ emissions at the outlet decrease by 17.6% to 40.7%. The mass fraction of unburned NH₃ rises to 0.0271, whilst NO_x emissions diminish from 49.47 ppm to 14.23 ppm. These changes are attributed to the low combustion efficiency and burning rate of ammonia, coupled with the reduced furnace temperature during ammonia-blended combustion, which weakens radiative heat transfer. Thus, optimizing the equivalence ratio along with applying hydrogen can improve the thermal efficiency of the reheating furnace. This study provides insight into the operational characteristics of a full-scale walking-beam reheating furnace operating under natural gas-ammonia co-firing conditions, providing theoretical guidance for enhancing the thermal efficiency of furnaces. Full article

Thermally driven heat pumps primarily use thermal energy to drive a compression cycle. The thermal energy can be waste heat, natural-gas combustion, or solar, helping increase efficiency and reduce greenhouse-gas emissions. We study a thermal compressor heat pump (TCHP) in which Stirling-type thermal compressors (TCs) are heat-driven rather than electrically driven, delivering a nominal heat capacity of 8 kW with CO₂ as the refrigerant. Unlike most existing dynamic models of CO₂ cycles, which focus on electrically driven or single-stage systems, this work targets a heat-driven multi-stage configuration and includes transient validation. Like any vapor compression cycle (VCC), a TCHP requires a dynamic model for control and optimization; its predictive reliability must be validated on experimental data. We therefore describe the test bench and performance expressions, collect steady-state and transient datasets, and derive a hybrid dynamic model: finite-volume (FV) differential equations for slow components and quasi-static submodels (linear regressions and correlations) for fast elements. The contribution of this work is the development and experimental validation of a hybrid FV model for a multi-stage heat-driven CO₂ TCHP. Validation against both steady-state and transient datasets shows good agreement. On 15 steady-state operating points, the model reproduces pressures within ∼1 bar mean absolute error (MAE) and system-level performance (total recovered heat, $CO{P}_{\mathrm{th}}$) within ∼6% mean absolute percentage error (MAPE), with $R^2\gtrsim 0.8$; component heat-rate predictions are within ∼20% MAPE. Under transient step tests on expansion valve openings and burner fan speed, the thermal COP and total recovered heat track within $4\%$ MAPE (up to $R^2=0.96$), pressures within $1.5$ bar MAE, and the evaporator heat rate within 14–$22\%$ MAPE. Full article

Global carbon emissions are driving the maritime industry toward cleaner fuels, with LNG already established as a transitional option that reduces SOx, NOx, and particulate emissions relative to conventional marine fuels and in line with decarbonisation strategies. This research aimed to explore the transition of offshore and marine platforms from conventional marine fuels to cleaner alternatives, with liquefied natural gas (LNG) emerging as the principal transitional fuel. Subsequently, floating liquefied natural gas (FLNG) platforms are increasingly being deployed to harness offshore gas resources, yet they face critical challenges related to weight, space, and energy efficiency. The study proposes pathways for transitioning FLNG energy systems from LNG to zero-carbon fuels, such as hydrogen derived directly from LNG resources, to optimise fuel supply under the unique operational constraints of FLNG units. The work unifies the independent domains of pure-fuel and blending-fuel processes for LNG and hydrogen, viewed in the context of thermodynamic processes, to optimise hydrogen–LNG co-firing gas turbine performance and meet the base power line of 50 MW. Furthermore, the research article will contribute to the development of other floating production platforms, such as FPSOs and FSRUs. It will be committed to clean energy policies that mandate support for green alternatives to hydrocarbon fuels. Full article

Biofuels represent a viable alternative to fossil fuels due to their lower greenhouse gas emissions, potential for large-scale production, and renewable nature. Orange oil, turpentine, and their hydrogenated derivatives have emerged as promising candidates for biofuel components. Efficient design and operation of internal combustion engines require knowledge of biofuel density and viscosity as functions of temperature; however, experimental data on these properties remain limited. In this work, the densities and viscosities of turpentine, orange oil, hydrogenated turpentine, and hydrogenated orange oil were measured at atmospheric pressure over the temperature range (293.15–373.15) K. The measurements were performed with uncertainties below 0.05 kg·m⁻³ for density and 0.3 mPa·s for viscosity. The experimental data were correlated as a function of temperature using a quadratic function for density and the Andrade equation for viscosity, with absolute average relative deviations of 0.01% for density and 0.5% for viscosity. For all substances, both viscosity and density decrease with increasing temperature, and they are lower than the values for biodiesel. Orange oil and turpentine exhibited higher densities but lower viscosities than their hydrogenated counterparts, which can be attributed to differences in molecular size and packing efficiency. Finally, the measured density and viscosity values are compared with the limit values specified in the European and American biodiesel standards. The analysis shows that blending these essential oils with conventional biodiesel could result in biofuel mixtures that meet both standards. Full article

In the context of the zero-carbon transition, this article provides a comprehensive review of Organic Rankine Cycle (ORC) technologies for low-grade heat recovery and conversion to power. It surveys a wide range of renewable and waste heat sources—including geothermal, solar thermal, biomass, internal combustion engine exhaust, and industrial process heat—and discusses the integration of ORC systems to enhance energy recovery and thermal efficiency. The analysis examines various configurations, from basic and regenerative cycles to advanced transcritical and supercritical designs, cascaded systems, and multi-source integration, evaluating their thermodynamic performance for different heat source profiles. A critical focus is placed on working fluid selection, where the landscape is being reshaped by stringent regulatory frameworks such as the EU F-Gas regulation, driving a shift towards low-GWP hydrofluoroolefins, natural refrigerants, and tailored zeotropic mixtures. The review benchmarks ORC against competing technologies such as the Kalina cycle, Stirling engines, and thermoelectric generators, highlighting relative performance characteristics. Furthermore, it identifies key trends, including the move beyond single-source applications toward integrated hybrid systems and the use of multi-objective optimization to balance thermodynamic, economic, and environmental criteria, despite persistent challenges related to computational cost and real-time control. Key findings confirm that ORC systems significantly improve low-grade heat utilization and overall thermal efficiency, positioning them as vital components for integrated zero-carbon power plants. The study concludes that synergistically optimizing ORC design, refrigerant choice in line with regulations, and system integration strategies is crucial for maximizing energy recovery and supporting the broader zero-carbon energy transition. Full article

The cost of “carbon net zero by year 2050” for the UK will be high, and this target date can only be achieved if the project is undertaken in a progressive and timely manner; otherwise, costs will escalate. The base power source behind the UK approach to “net zero” is nuclear fission electricity power stations, and the ones currently on order are running significantly late. Renewables will provide some supply together with interconnectors, but only approx. twenty percent of the planned wind turbines are in place. The electricity distribution grid must change to satisfy the UK’s planned “electricity-based” future. Energy use for transport is also a significant fraction of total UK energy consumption and we include predictions for their associated emissions. These must be reduced in a progressive and timely fashion. Intermittent support for unreliable renewables is necessary and methods employing both liquid as well as gaseous fuels are suggested. Means to use and upgrade the existing infrastructure are considered, and a few of the basic building blocks of the future are examined regarding their installation without significant interruption to the basic UK economy. ANR/AMR and SMR are included as potential renewables support as well as base load generators, and the approx. quantity of CO₂e emissions avoided is estimated. Even though methane is a powerful greenhouse gas, the main support for renewables will be UK natural gas (methane content ~95%), with Avtur/diesel as a recommended reserve. It is suggested that methane has a significant short- to medium-term future as a transition fuel. Full article

Pressurized chemical looping combustion (PCLC) provides the benefit of simplifying the carbon capture process by generating a flue gas stream with high CO₂ concentration. However, flue gas polishing is required to remove the residual impurities for pipeline transport. The intensified heat exchanger reactor (IHXR) is a promising method for flue gas polishing while maximizing useful heat recovery that incorporates alternating catalytic packed beds with interstage cooling via printed circuit heat exchangers (PCHE). This work offers a design process for an IHXR capable of polishing a flue gas stream from a 100 MWth natural gas-fired PCLC unit while recovering 1.6 MW of useful heat in the form of saturated steam at 180 °C. Simulation work performed in Aspen HYSYS was used to determine the polished flue gas outlet species concentrations as well as the required number and size of the packed bed sections. The PCHEs for interstage cooling were sized via a thermal circuit approach. The final IHXR consists of six packed beds at 0.06 m in length and five PCHEs at 0.265 m in length, combining to a total IHXR length of 1.685 m. The height and width of the IHXR is shared between the packed beds and PCHEs at 0.91 m and 0.45 m, respectively. The resulting IHXR is capable of recovering heat at a rate of approximately 2.3 MW/m³. Full article