Fuels, Volume 5, Issue 1 (March 2024) – 7 articles

The present study evaluated the applicability of ¹H NMR and UV-Vis spectroscopies as analytical techniques for the characterization and determination of biodiesel conversion and for monitoring the oxidative stability of biodiesel samples with antioxidants. For this study, safflower and babassu biodiesels were obtained through transesterification, and physicochemical properties confirmed the success of both reactions. A bench-top accelerated oxidation system was used as an alternative to the Rancimat^® method, with samples of 6.0 g heated at 110 ± 5 °C and collected every 2 h for 12 h. The agreement for biodiesel conversions was good, with divergences between 2% and 0.4% for safflower biodiesel and 1.9% for babassu biodiesel. As for UV-Vis spectroscopy, the technique showed the same trend as the Rancimat^® method, showing efficiency in evaluating the oxidative stability of safflower biodiesel and in the performance of antioxidants BHT and DMP-30. The accuracy of NMR signals integration for mixtures of safflower oil and safflower biodiesel and the use of UV-Vis spectroscopy associated with a bench-top accelerated oxidation system to investigate the performance of phenolic and amine antioxidants in safflower and babassu biodiesel were explored for the first time, showing results close to the standard methods. Therefore, ¹H NMR and UV-Vis spectroscopies could be applied as alternatives to the GC and Rancimat^® methods to determine conversion and monitor the oxidative stability of biodiesel rapidly and practically. Full article

Polyoxymethylene dimethyl ether (PODE_n, n ≥ 1) is a promising alternative fuel to diesel with higher reactivity and low soot formation tendency. In this study, PODE_3-4 is used as a pilot ignition fuel for methane (CH₄) and the combustion characteristics of PODE_3-4/CH₄ mixtures are investigated numerically using an updated PODE_3-4 mechanism. The ignition delay time (IDT) and laminar burning velocity (LBV) of PODE_3-4/CH₄ blends were calculated at high temperature and high pressure relevant to engine conditions. It is discovered that addition of a small amount of PODE_3-4 has a dramatic promotive effect on IDT and LBV of CH₄, whereas such a promoting effect decays at higher PODE_3-4 addition. Kinetic analysis was performed to gain more insight into the reaction process of PODE_3-4/CH₄ mixtures at different conditions. In general, the promoting effect originates from the high reactivity of PODE_3-4 at low temperatures and it is further confirmed in simulations using a perfectly stirred reactor (PSR) model. The addition of PODE_3-4 significantly extends the extinction limit of CH₄ from a residence time of ~0.5 ms to that of ~0.08 ms, indicating that the flame stability is enhanced as well by PODE_3-4 addition. It is also found that NO formation is reduced in lean or rich flames; moreover, NO formation is inhibited by too short a residence time. Full article

Hydrothermal liquefaction (HTL) is an emerging technology for bio-crude production but faces challenges in determining the optimal temperature for feedstocks depending on the process mode. In this study, three feedstocks—wood, microalgae spirulina (Algae Sp.), and hydrolysis lignin were tested for sub-supercritical HTL at 350 and 400 °C through six batch-scale experiments. An alkali catalyst (K₂CO₃) was used with wood and hydrolysis lignin, while e (Algae Sp.) was liquefied without catalyst. Further, two experiments were conducted on wood in a Continuous Stirred Tank Reactor (CSTR) at 350 and 400 °C which provided a batch versus continuous comparison. Results showed Algae Sp. had higher bio-crude yields, followed by wood and lignin. The subcritical temperature of 350 °C yielded more biocrude from all feedstocks than the supercritical range. At 400 °C, a significant change occurred in lignin, with the maximum percentage of solids. Additionally, the supercritical state gave higher values for Higher Heating Values (HHVs) and a greater amount of volatile matter in bio-crude. Gas Chromatography and Mass Spectrometry (GCMS) analysis revealed that phenols dominated the composition of bio-crude derived from wood and hydrolysis lignin, whereas Algae Sp. bio-crude exhibited higher percentages of N-heterocycles and amides. The aqueous phase analysis showed a Total Organic Carbon (TOC) range from 7 to 22 g/L, with Algae Sp. displaying a higher Total Nitrogen (TN) content, ranging from 11 to 13 g/L. The pH levels of all samples were consistently within the alkaline range, except for Wood Cont. 350. In a broader perspective, the subcritical temperature range proved to be advantageous for enhancing bio-crude yield, while the supercritical state improved the quality of the bio-crude. Full article

Fossil fuels, such as coal and hydrocarbons, are major drivers of global warming and are primarily responsible for worldwide greenhouse gas emissions, including carbon dioxide CO₂. The storage of CO₂ in deep saline reservoirs is acknowledged as one of the top practical and promising methods to reduce CO₂ emissions and meet climate goals. The North Dakota Industrial Commission (NDIC) recently approved the fourth Class VI permit for a carbon capture and storage project in the Williston basin of North Dakota for the geological CO₂ storage in the Broom Creek formation. The current research aimed to conduct a comprehensive petrophysical characterization and rock physics modeling of the Broom Creek deep saline reservoir to unravel the mineralogical distribution and to understand the variations in petrophysical and elastic properties across the formation. This study utilized geophysical well logs, routine core analysis, and advanced core analysis to evaluate the Broom Creek formation. Multimineral petrophysical analysis calibrated with X-ray diffraction results reveals that this formation primarily comprises highly porous clean sandstone intervals with low-porosity interspersed with dolomite, anhydrite, and silt/clay layers. The formation exhibits varying porosities up to 0.3 and Klinkenberg air permeabilities up to ∼2600 mD. The formation water resistivity using Archie’s equation is approximately 0.055 ohm-m at 150 °F, corresponding to around 63,000 ppm NaCl salinity, which is consistent with prior data. The pore throat distribution in the samples from clean sandstone intervals is primarily situated in the macro-mega scales. However, the presence of anhydrite and dolomite impedes both porosity and pore throat sizes. The accurate prediction of effective elastic properties was achieved by developing a rock physics template. Dry rock moduli were modeled using Hill’s average, while Berryman’s self-consistent scheme was employed for modeling saturated moduli. Full article

This study investigates the application of fiber optic technology to optimize completion design in a hydraulic fracture stimulation for Marcellus Shale Reservoir. With a focus on improving cluster efficiencies and overcoming interstage communication challenges, the research utilizes real-time data from distributed acoustic (DAS), temperature (DTS), and strain (DSS) measurements. The methodology comprises a comprehensive analysis of completion and stimulation reports, fiber optics, microseismic data, and well logs. Conducted at the MSEEL well pads, MIP, and Boggess, and equipped with permanent and deployable fiber optic cables, this study emphasizes that engineered/geomechanical completion design leads to sustained cluster efficiency and stage production performance. Inefficient cluster efficiencies are primarily linked to fracture communication. Recommendations include employing a geomechanical completion design, avoiding non-uniform high natural fracture zones during hydraulic fracture stimulations, implementing short stage length, and using more 100 mesh sand. These insights, derived from correlations between fracture counts, distributed strain sensing (DSS), cluster efficiency, production logging, and production data, offer significant implications for optimizing completion design in unconventional reservoirs. The effective application of fiber optic technology, providing real-time DAS, DTS, and slow strain data, proves instrumental in addressing interstage communication challenges, contributing to improved reservoir performances and cost-effective operations in hydraulic fracture stimulations. Full article

Biodiesel has emerged as a progressively widespread and significant alternative to traditional diesel fuel within the transportation sector. Despite its growing popularity, the issue of corrosive tendencies upon interaction with both moving and static components of diesel engines and fuel systems poses a serious concern. This research endeavors to assess the corrosion characteristics of materials commonly found in automotive fuel systems when exposed to various blends of rapeseed oil biodiesel and diesel. The study involved static immersion tests, lasting 3360 h at room temperature, using B0, B20, B40, B60, B80, and B100 fuels. Copper, brass, aluminum, zinc, and stainless steel plate samples were subjected to these tests. The evaluation at the conclusion of the study included weight loss measurements, corrosion rate calculations, and observation of changes in the exposed metal surfaces. Surface morphology was scrutinized using a Bresser LCD MICRO 5MP digital microscope. Additionally, the total acid number (TAN) was employed to assess alterations in fuel acidity before and after the immersion tests. Full article

Tropical firewood species are of foremost importance for charcoal production worldwide. The objective of this study was to evaluate the impact of the moisture content of tropical fuelwood on charcoal production in modified Argentinean half-orange kilns in terms of yield, quality, and economic viability. Ten tropical species from the state of Quintana Roo, Mexico, were selected for charcoal production. The data were analyzed using a completely randomized design. The moisture content of the firewood was 48.99–79.31%. Temperatures close to 500 °C were obtained in the three kilns, as well as production yields of 28% with a consumption of 6.4 m³ of firewood and 38% with a consumption of 4.5–5 m³. Charcoal moisture values of less than 8%, volatile material of 20–30%, ash < 8%, fixed carbon of 60–70%, and higher heating values of 28–30 MJ kg⁻¹ were obtained. Burn I obtained the highest energy yield of 54%, with a production of 20.87 MWh of charcoal recovered. The production cost of the kiln for the producer is USD 0.00825 (MXN 0.16) per MJ. Full article