Fuels, Volume 4, Issue 2 (June 2023) – 8 articles

Diethyl carbonate (DEC) is a common component of the liquid electrolyte in lithium ion batteries (LIBs). As such, understanding DEC combustion chemistry is imperative to improving chemical kinetic modeling of LIB fires. To this end, a comprehensive experimental study was conducted to collect ignition delay times, CO time histories, and laminar flame speeds during DEC combustion. Ignition delay times were collected using a heated shock tube at real fuel–air conditions for three equivalence ratios (ϕ = 0.5, 1.0, and 2.0) near atmospheric pressure and for temperatures between 1182 and 1406 K. Another shock tube was used to collect CO time histories using a laser absorption diagnostic. These experiments were conducted for the same equivalence ratios, but highly diluted in argon and helium (79.25% Ar + 20% He) at an average pressure of 1.27 atm and a temperature range of 1236–1669 K. Finally, a heated constant-volume vessel was used to collect laminar flame speeds of DEC at an initial temperature and pressure of 403 K and 1 atm, respectively, for equivalence ratios between 0.79 and 1.38. The results are compared with different mechanisms from the literature. Good agreement is seen for the ignition delay time and flame speed measurements. However, significant deviations are observed for the CO time histories. A detailed discussion of the chemical kinetics is presented to elucidate the important reactions and direct future modeling efforts. Full article

The current energy and climate crisis calls for immediate action in replacing fossil fuels with those derived from renewable sources. The Energreen process performs the direct liquefaction of biomass to produce a liquid biofuel for the cement industry and an aqueous solution of added-value compounds for further processing. The present work details the development of an Aspen Plus^® model to simulate this biomass liquefaction process. The proposed model describes the Energreen liquefaction process using simplified reaction kinetics and thermodynamic models. The model was validated using data from a real liquefaction pilot plant with a deviation of 6.4%. The simulation, conducted with several biomass samples of variable compositions, showed that the process is robust enough to deal with different compositions and, due to the substitution of the fossil fuels presently used in the cement plant, it will allow savings of up to USD 102,000 per year to be achieved. Several analyses of the sensitivity of the results to the process variables were performed and it was possible to identify the reactor temperature and the reaction activation energy as the most impactful parameters on the process output. Overall, the results allow us to conclude that the proposed model is a solid framework for the optimization of industrial liquefaction processes. Full article

The production of CO₂-neutral fuels is a key technology to achieve the European Union’s targets of greenhouse gas reduction in the transport sector. For a straightforward application such as drop-in fuel, regenerative gasoline must meet emission requirements without causing significant changes in engine parameters. The objective of this work was to demonstrate the emission reduction potential of fuel from the bioliq^® plant by reducing the content of heavy aromatics in the product refinement. For three blends with varying contents of bioliq^® fuel, the spray behavior was studied in a pressurized chamber and the particulate and hydrocarbon emissions were investigated using a single-cylinder research engine. With increasing bioliq^® fuel content, atomization was degraded by lower flash boiling at low pressure. This effect vanished at higher chamber pressures. Measurements of particulate and hydrocarbon emissions showed significant improvements of 50% to 100% and 10%, respectively, compared to previously investigated bioliq^® fuel fractions from 2017. The formation of particulate emissions is virtually unaffected by the blending of bioliq^® fuel, due to the absence of heavy aromatics in the refined bioliq^® product. Hydrocarbon emissions increased by 20% with higher bioliq^® fuel content and late injection timings due to inferior mixture formation as a result of slightly reduced atomization. However, near the optimum injection timing, the hydrocarbon emissions are independent of the bioliq^® fuel admixture. Full article

A bio-oil-based epoxy (BOE) resin was synthesized using phenolic compounds from beechwood pyrolysis oil. These compounds were separated from crude pyrolysis oil by coupling two methods: fractional condensation and water extraction. The chemical structure of the BOE resin was characterized by NMR and FTIR analyses. BOE resin was used as a curing agent of bio-oil glyoxal novolac (BOG) resin to gradually replace bisphenol A diglycidyl ether (DGEBA). The thermal properties of cured resins and kinetic parameters of the curing reaction using differential scanning calorimetry (DSC) were discussed. Incorporating the BOE resin resulted in a lower curing temperature and activation energy compared to using DGEBA. These results indicate that the water-insoluble fraction of pyrolysis oil condensate can potentially be used to synthesize high-thermal performance and sustainable epoxidized pyrolysis bio-oil resins and also demonstrate its application as a curing agent of bio-oil glyoxal novolac (BOG) resin. Full article

Flame-generated soot particles from two different fuels, benzene (B) and ethylene (E), at different ageing conditions, were analysed to assess their morphological and structural features. Samples were collected at 6, 10 and 14 mm from the nozzle location. Traditional 2D transmission electron microscopy (TEM) and a novel 3D TEM were used to investigate morphology variations. High-resolution TEM (HRTEM) was used to capture structural characteristics. Samples were then placed on lacey carbon microgrids. A field emission gun TEM was used to capture images of the agglomerates. Tilt series of ±60 degrees were acquired at 1-degree steps to perform the 3D reconstruction. IMOD software and backwards projection were used to reconstruct the tomogram from the tilt series. The 2D analysis revealed that soot particles’ agglomerations for both fuels change from a bundle to a chain-like structure as they “age”, i.e., extracted at a higher “flame height”. In B, the primary particle diameter increases as they get “older,” whereas in E, the opposite happens, and overall, E particles are bigger than B ones. The nanostructure presents ordered regions with parallel-stacked layers of carbon lamellae. This is more evident in the aged soot samples, with the difference that in E a thick amorphous layer is present at the edge of the particles, which is not observable for B. A nanostructure analysis suggests a trend of increasing fringes length as the soot ages, going from 1.04 nm of B6 to 1.22 nm of B10 to 1.05 nm of B14 and from 1.139 nm of E6 to 1.20 nm of E14 (±0.02 nm). The tortuosity does not vary greatly across all the samples, ranging between 1.132 and 1.149 (±0.004). Separation is also quite similar everywhere, with 0.404 nm of B6, 0.392 nm of B10, 0.399 nm of B14, 0.397 nm of E6 and 0.396 nm of E14 (±0.002 nm). Ring structures and particle overlaps, two examples of geometrical characteristics concealed in 2D, can be seen in the 3D reconstructions. Furthermore, the comparison between 3D and 2D volume and surface area raises questions about the reliability of those parameters as derived from 2D measurements. This study advances knowledge of how soot structure can be affected by the fuel type and emphasises the significance of how soot is investigated. Full article

Methanol-to-gasoline (MTG) and dimethyl ether-to-gasoline (DTG) fuels are rich in heavy aromatics such as 1,2,4,5-tetramethylbenzene, resulting in low volatilities due to a lack of light ends, increased emission tendencies and drivability problems due to crystallization. Approaches addressing these issues mainly focus on single aspects or are optimized for petroleum-based feedstocks. This research article introduces an upgrading strategy for MTG and DTG fuels through hydroprocessing (HP) heavy-ends and applying a sophisticated blending concept. Different product qualities were prepared by HP heavy gasoline (HG) and Fischer-Tropsch wax using commercially available Pt/HZSM-5 and Pt/SAPO-11 catalysts in a fixed-bed reactor. The products were used for blending experiments, focusing on gasoline volatility characteristics. Accordingly, methanol, ethanol, methyl tert-butyl ether (MTBE), and ethyl tert-butyl ether (ETBE) were evaluated in a second blending experiment. The results were finally considered for preparing blends meeting EN 228. HP of HG was found to improve the amount of light-ends and the vapor pressure of the DTG fuel with increasing reaction temperature without, however, satisfying EN 228. The front-end volatility was further improved by blending methanol due to the formation of near-azeotropic mixtures, while ethyl tert-butyl ether (ETBE) considerably supported the mid-range volatility. A final blend with an alcohol content of less than 3 vol.%, mostly meeting EN 228, could be provided, making it suitable even for older vehicles. Full article

Biodiesel is being considered a possible alternative fuel due to its similarity with diesel and environmental benefits. This current work involves a numerical investigation of CI engine characteristics operating on D100 (diesel) and Dunaliella tertiolecta (DMB20), Scenedesmus obliquus (SOMB20), Scenedesmus dimorphu (SDMB20), and Chlorella protothecoides (CMB20) microalgae biodiesel blend. A diesel engine of 3.7 kW was used with variable compression ratios (CRs) (15.5, 16.5, 17.5, and 18.5) and constant speed (1500 rpm). Comparative analysis was performed for engine characteristics, including emission, combustion, and performance. Cylinder pressure, heat release rate, brake thermal efficiency, specific fuel consumption, particulate matter, oxide of nitrogen, carbon dioxide, etc., were evaluated using the blended fuel. The results show that the maximum cylinder pressure falls, SFC increases, and EGT and BTE were reduced for all blends at full load. In terms of emission characteristics, PM and smoke were lowered when compared to diesel, but a slight increment in NOx and CO₂ was observed. Among all the blends, SOMB20 shows the most decrement in PM and smoke emissions by 14.16% and 11.6%, respectively, at CR 16.5. CMB20 shows a maximum increment in SFC by 3.22% at CR 17.5. A minimum reduction in CP and HRR was shown by DMB20 irrespective of CRs. Full article