•The production methods and physical properties of liquid alternative fuels are reviewed.•Biodiesel can be utilised for land-based power generation gas turbines.•SVO and bio-oil usage in gas turbine ...requires preheating and atomisation technologies.•Bioethanol can be used as solvent/supplemental fuel for viscous fuel.•Extensive use of FT fuel and HVO is currently constrained by high production cost.
The increasing demand for clean and sustainable energy sources provides the impetus for the development of alternative fuels. Recent development of fuel-flexible gas turbine technologies enables the use of alternative non-fossil fuels that could play key roles in contributing to the global efforts in meeting emissions targets. This review highlights the current state-of-the-art production and properties of alternative fuels such as straight vegetable oil (SVO), biodiesel, bioethanol, bio-oil, hydrogenated vegetable oil (HVO) and Fischer-Tropsch (FT) fuel. This is followed by the evaluation of combustion performances in gas turbines. All of the alternative liquid biofuels have shown their potentials in reducing regulated emissions such as NOx, CO and soot under favourable operating conditions. Both HVO and FT fuels show comparable performance as that of jet fuel and can be used in aviation gas turbines, although the present day high production cost restricts the large-scale adoption, limiting its utility. They also have considerably higher cetane number than the rest, making it easier for the fuel to ignite. As for stationary power generation gas turbines that need not carry payloads, the other four alternative biofuels of biodiesel, bioethanol, bio-oil and SVO are possible candidates despite the physics-chemical properties variations when compared to fossil fuels. Amongst them, the use of SVO and bio-oil in gas turbines would require the parallel development of fuel supply systems and atomisation technologies to improve the combustion of the fuels. In all, the alternative liquid fuels reviewed provides realistic opportunities for cleaner and more sustainable operation of aviation and power generation gas turbines. Profound understanding on the fundamental combustion characteristics of the fuels are essential to expedite their mass adoption in gas turbine applications.
Alternative fuels are essential to enable the transition to a sustainable and environmentally friendly energy supply. Synthetic fuels derived from renewable energies can act as energy storage media, ...thus mitigating the effects of fossil fuels on environment and health. Their economic viability, environmental impact, and compatibility with current infrastructure and technologies are fuel and power source specific. Nitrogen-based fuels pose one possible synthetic fuel pathway. In this review, we discuss the progress and current research on utilization of nitrogen-based fuels in power applications, covering the complete fuel cycle. We cover the production, distribution, and storage of nitrogen-based fuels. We assess much of the existing literature on the reactions involved in the ammonia to nitrogen atom pathway in nitrogen-based fuel combustion. Furthermore, we discuss nitrogen-based fuel applications ranging from combustion engines to gas turbines, as well as their exploitation by suggested end-uses. Thereby, we evaluate the potential opportunities and challenges of expanding the role of nitrogen-based molecules in the energy sector, outlining their use as energy carriers in relevant fields.
•Pre-treatment methods of MSS are analyzed and the effect of different solvents on the extraction of lipids was discussed.•State-of-art of biofuel production from sewage sludge is critically ...presented.•Parametric optimization efforts for efficient biodiesel production were summarized.•Attempts on kinetics of transesterification reaction and intensification of biodiesel production were analyzed.•Quality of biodiesel and process economics were discussed.
Bio-fuels are gaining worldwide attention as an alternative fuel option replacing the usage of the mineral diesel derived from conventional fossil sources. However, the high cost attributed by the feedstock made it less competitive with the commercial diesel. A widespread research is going on worldwide for the production of fuels from renewable biomass replacing the currently used traditional sources. The high lipid-containing municipal sewage sludge (MSS) can be considered as a potential feedstock owing to its low cost and abundant availability. The lipids are transformed to biodiesel via transesterification or to bio-oil by pyrolysis. In this review paper, a comprehensive discussion on the various aspects of bio-fuel production from sludge derived lipids along with the key parameters affecting the process and its economics are presented. This review also emphasizes that future studies should focus on the usage of modern process intensification techniques for more efficient production of bio-fuel from renewable biomass.
Artificial fuels have been researched for more than a decade now in an attempt to find alternative sources of energy. With global climatic conditions rapidly approaching the end of their safe line, ...an emphasis on escalating the change has been seen in recent times. Synthetic fuels are a diverse group of compounds that can be used as replacements for traditional fuels, such as gasoline and diesel. This paper provides a comprehensive review of synthetic fuels, with a focus on their classification and production processes. The article begins with an in-depth introduction, followed by virtually classifying the major synthetic fuels that are currently produced on an industrial scale. The article further discusses their feedstocks and production processes, along with detailed equations and diagrams to help readers understand the basic science behind synthetic fuels. The environmental impact of these fuels is also explored, along with their respective key players in the industry. By highlighting the benefits and drawbacks of synthetic fuels, this study also aims to facilitate an informed discussion about the future of energy and the role that synthetic fuels may play in reducing our reliance on fossil fuels.
•Regulations on marine diesel engine emissions are listed and compared.•The contribution of marine diesel engine emissions to regional emissions is given.•The emission levels of marine diesel engines ...are reviewed.•Integrated multi-pollutant aftertreatment technologies are reviewed.
Marine diesel engines, which provide main power source for ships, mainly contribute to air pollution in ports and coastal areas. Thus there is an increasing demand on tightening the emission standards for marine diesel engines, which necessitates the research on various emission reduction strategies. This review covers emission regulations and emission factors (EFs), environmental effects and available emission reduction solutions for marine diesel engines. Not only the establishment of the emission control areas (ECAs) in the regulations but also many experiments show high concerns about the sulfur limits in fuels, sulfur oxides (SOx) and nitrogen oxides (NOx) emissions. Research results reveal that NOx emissions from marine diesel engines account for 50% of total NOx in harbors and coastal regions. Sulfur content in fuel oil is an important parameter index that determines the development direction of emission control technologies. Despites some issues, biodiesel, methanol and liquefied nature gas (LNG) play their important roles in reducing emissions as well as in replacing fossil energy, being promising fuels for marine diesel engines. Fuel-water emulsion (FWE) and exhaust gas recirculation (EGR) are effective treatment option for NOx emissions control. Common rail fuel injection is an effective fuel injection strategy to achieve simultaneous reductions in particulate matter (PM) and NOx. Selective catalytic reduction (SCR) and wet scrubbing are the most mature and effective exhaust aftertreatment methods for marine diesel engines, which show 90% De-NOx efficiency and 95% De-SOx efficiency. It can be concluded that the integrated multi-pollutant treatment for ship emissions holds great promise.
Display omitted
•Waste cooking oil (WCO) recycling models and practices are reviewed.•The processing pathways of converting WCO into biofuels are examined.•Energy balance for biodiesel conversion ...using different techniques is analysed.•Conversion of WCO into biojet fuel is feasible using hydrogenation method.•Biofuel production using WCO is sustainable and reduces GHG emissions.
The increase in human consumption of plant and animal oils has led to the rise in waste cooking oil (WCO) production. Instead of disposing the used cooking oil as waste, recent technological advance has enabled the use of WCO as a sustainable feedstock for biofuels production, thereby maximising the value of biowastes via energy recovery while concomitantly solving the disposal issue. The current regulatory frameworks for WCO collection and recycling practices imposed by major WCO producing countries are reviewed, followed by the overview of the progress in biodiesel conversion techniques, along with novel methods to improve the feasibility for upscaling. The factors which influence the efficiency of the reactions such as properties of feedstock, heterogenous catalytic processes, cost effectiveness and selectivity of reaction product are discussed. Ultrasonic-assisted transesterification is found to be the least energy intensive method for producing biodiesel. The production of bio-jet fuels from WCO, while scarce, provide diversity in waste utilisation if problems such as carbon chain length, requirements of bio-jet fuel properties, extreme reaction conditions and effectiveness of selected catalyst-support system can be solved. Technoeconomic studies revealed that WCO biofuels is financially viable with benefit of mitigating carbon emissions, provided that the price gap between the produced fuel and commercial fuels, sufficient supply of WCO and variation in the oil properties are addressed. This review shows that WCO is a biowaste with high potential for advanced transportation fuel production for ground and aviation industries. The advancement in fuel production technology and relevant policies would accelerate the application of sustainable WCO biofuels.
The automotive industry remains one of the most significant contributors to total global emissions worldwide. This growing challenge is primarily attributed to the high dependency on fossil fuel as ...its primary source of energy. This review highlights the current state of the application of fuel cells in the automotive industry, as well as the technological advances made in comparison to the early years of the automotive sector. Future prospects of these technologies are also thoroughly reviewed. Factors impeding the advancement of these technologies while also impeding their commercialization are presented, with possible solutions to this problem also suggested. In summary, this investigation seeks to explore pragamatic approach that can be adopted to reduce the overall cost of fuel cells and their possible integration in the automotive industry.
•Adding primary alcohol fuels increased the ignition delay and reduced the combustion duration.•BTE was decreased, CO and PM emissions were reduced, and THC and NOX emissions were increased by adding ...primary alcohol fuel.•For a fixed ASP, methanol has the lowest COVIMEP and ringing intensity, and the highest BTE among the three alcohol fuels.•Adding methanol produces the highest THC emission and the lowest CO, NOX and soot emissions among the three alcohol fuels.
Primary alcohol fuels are the most promising fuels for diesel engines, thanks to their low emissions and easy adaptability to engine technologies. In this paper, the effects of the addition of methanol, ethanol, and n-butanol on the combustion characteristics and performance of a common rail dual fuel engine with diesel direct injection and alcohol fuel port injection are examined, followed by a comparative analysis of the test results.The test engine was operated at the maximum torque speed of 2500 rpm, and with a mean effective pressure (IMEP) of 0.75 MPa. The engine performance was analyzed for different alcohol/diesel fuel mixtures by using five alcohol substitute percentages (ASPs): 0% (pure diesel), 10%, 20%, 30%, and 40%. The experimental results demonstrate that slower flame development and faster flame propagation can be obtained by mixing any of the three alcohol fuels with diesel, compared with the pure diesel. With an increased ASP, the coefficient of variation of IMEP (COVIMEP) and the brake thermal efficiency (BTE) decreased, and the ringing intensity (RI) first increased and then dropped. The addition of primary alcohol fuels in the dual-fuel mode can also increase the total hydrocarbon (THC) and nitrogen oxide (NOX) emissions, but the carbon monoxide (CO) and soot emissions decrease. The comparative analysis indicated that the addition of methanol has the lowest COVIMEP and RI and the highest BTE among the three alcohol fuels. Adding methanol produces the lowest CO, NOX, and soot emissions and the highest THC emissions among the three alcohol fuels.
Bio-based aviation fuels are considered as a promising alternative for conventional aviation fuels due to their sustainability and environmental friendliness. This review evaluated bio-jet fuels’ ...performance based on their physicochemical properties, including low-temperature fluidity, thermal oxidation stability, combustion property, fuel compatibility and volatility, and energy density. The objective is to understand the effects of the chemical compositions of bio-jet fuels on their performance characteristics. This is of particular importance in that bio-jet fuels are generally derived from a broad spectrum of feedstock and thus have very different composition. In general, bio-jet fuels exhibit satisfactory characteristics in compliance with the American Society for Testing and Materials D7566-18 standard. The aromatic content has a critical influence on the performance of bio-jet fuels. Research efforts are needed to study the characteristics of recently certified bio-based blending components such as synthesized iso-paraffins and alcohol-to-jet. Storage stability, a rarely reported property also deserves further investigation.
•Gasoline/diesel/hydrogenated catalytic biodiesel blends are used.•String cavitation which is incepted by vortex is researched with a real-size optical nozzle.•The addition of gasoline into diesel ...and HCB enhanced cavitation and make the weaker vortex in the sac visible.•Increasing temperature enhanced cavitation and enlarged sprayangle but affects gasoline/HCB blends a few.
Renewable clean fuel such as biodiesel, alcohol-based fuel blended with fossil fuel has been widely studied for applications in engines aiming at partial solution of fuel consumption and environment emission issues. These blending fuels have also shown advantages in new combustion modes like GCI and LTC. However, the fuel injector nozzle internal flow and spray behaviors of these blending fuels are still not well understood, which may largely influence the subsequent fuel–air mixture, combustion, and emission characteristics. The investigation of cavitation flow in the high-pressure common-rail injector nozzle and spray characteristics with blending fuels of gasoline, diesel, and hydrogenated catalytic biodiesel (HCB) was conducted in the present work. The real-size optical nozzle was used to visualize the nozzle internal cavitating flow and spray. It was found that, by adding gasoline into diesel and HCB, the string cavitation increased significantly, and the spray cone angle expanded, especially under low needle lift. This behavior can be interpreted as the lower viscosity and higher saturation vapor pressure of gasoline enhanced vortex and cavitation. It can be concluded that increasing fuel temperature significantly impacted the cavitation and affected the vortex lightly, suggesting that with higher temperatures, blended fuels show better performance. As the fraction of HCB of gasoline/HCB blends increased, the cavitation inside nozzles was restrained due to its high viscosity. String cavitation can be interrupted by the needle tip, and the spray cone angle fluctuated enormously under this situation, which may cause uneven mixing of fuels and air.
PDF
