Fuels, Volume 4, Issue 1 (March 2023) – 8 articles

Torrefaction pretreatment is a mild form of pyrolysis that has the potential to produce a high-quality raw material for making biofuel that serves as a replacement for coal in the bioenergy industry. Microwave-assisted torrefaction was conducted on white spruce sawdust (WSS) at temperatures of 200 °C, 250 °C, and 300 °C and retention times of 5 min, 7 min, and 9 min in an inert environment. The torrefaction process produces a solid carbon, commonly known as biochar, and condensable (torrefaction liquid (TL)) and non-condensable gases. In this study, torrefaction characteristics were investigated to observe its effects on the thermal and physiochemical properties of the pellets produced. During the torrefaction process, a significant mass loss associated with the decomposition of hemicellulose was observed. The hemicellulose content drastically reduced to approximately 1.8% and the cellulose content was reduced by approximately 10%, while the lignin gained approximately 35% as the severity increased. This led to an improvement in the higher heating value (HHV), hydrophobicity, bulk, particle density, pellet dimensional stability, and pellet density. However, the pellet tensile strength decreased as the torrefaction severity increased. Pellet tensile strength is a critical indicator of biomass pellets that expresses the force required to crush or damage a pellet. Therefore, to enhance the tensile strength of the pellets, the introduction of a binder was necessary. Torrefaction liquid and sawdust were used as additives at different proportions during pelletization. The addition of binders (torrefaction liquid and sawdust) to the pellet formulation increased the tensile strength of the torrefied WSS by approximately 50%. The OH groups in the biomass break down to a limited degree due to dehydration. This hinders the formation of H bonds, thereby increasing the chances that the pretreated biomass will become hydrophobic. The SEM graphs showed that the torrefied WSS pellets demonstrated more firmly glued surfaces with fewer pores spaces when set side by side with the raw pellets. The thermogravimetric analysis conducted showed that the torrefaction of WSS slightly reduced its thermal stability. Full article

Multilateral well drilling technology has recently assisted the drilling industry in improving borehole contact area and reducing operation time, while maintaining a competitive cost. The most advanced multilateral well drilling method is Fishbone drilling (FbD). This method has been utilized in several hydrocarbon fields worldwide, resulting in high recovery enhancement and reduced carbon emissions from drilling. FbD involves drilling several branches from laterals and can be considered as an alternative method to hydraulic fracturing to increase the stimulated reservoir volume. However, the expected productivity of applying a Fishbone well from one field to another can vary due to various challenges such as Fishbone well design, reservoir lithology, and accessibility. Another challenge is the lack of existing analytical models and the effect of each Fishbone parameter on the cumulative production, as well as the interaction between them. In this paper, analytical and empirical productivity models were modified for FbD in a dry gas reservoir. The modified analytical model showed a higher accuracy with respect to the existing model. It was also compared with the modified empirical model, which proved its higher accuracy. Finally, machine learning algorithms were developed to predict FbD productivity, which showed close results with both analytical and empirical models. Full article

The Conventional Laser Absorption Scattering (C-LAS) technique is used to measure the mixture concentration and visualize the vapor phase. The former is determined by the attenuation of visible and ultraviolet light whereas the latter is achieved via light absorption and scattering theory. The C-LAS uses the Nd: YAG pulsed laser and CCD cameras to provide one spray shot at a particular instance which requires time and effort. However, the temporal measurement of a single spray shot is not possible. To record the distribution of the whole vapor phase in an injection event and measure liquid and vapor concentrations inside the spray, a High-Speed Laser Absorption Scattering (HS-LAS) technique was developed. The HS-LAS consists of continuous diode light sources, high-speed video cameras, and an image intensifier for UV light, which can provide the temporal variation of a single-shot spray. In the experiment, a commercial seven-hole injector with a hole diameter of 0.123 mm allowing high injection pressure of up to 100 MPa was used to avoid the potential inconsistencies with a single-hole test injector. The diesel surrogate fuel which consists of 97.5% n-tridecane and 2.5% of volume-based 1-methylnaphthalene was used. The injection amount of 5.0 mg/hole was selected to investigate the structure and mixture formation process of the spray. The findings of the experiments show that this imaging approach is a promising diagnostic technique for concurrently obtaining quantitative information on the quantity of vapor and droplets in a fuel spray. Furthermore, the turbulent/vortex fluid dynamics’ temporal development/variation can be investigated. Full article

Petcoke is a solid carbon-rich residue produced during petroleum refining. Petcoke mineral matter is rich in vanadium that, when alloyed with other metals, can significantly improve its properties. Vanadium extraction from steel slags is well studied, while extraction from secondary sources such as petcoke is not well understood. Vanadium is one of the 50 critical minerals identified by the United States Department of Interior. Considering the annual production of petcoke, it is a valuable secondary source of vanadium, especially in places with no steel production. This review paper critically examines the compositional differences between steel and petcoke slags and the various extraction methods that apply to vanadium production, particularly from petcoke, considering the environmental issues associated with each technique. Information on the characterization of US petcoke is also included to identify specific extraction methods for vanadium. Full article

Water-in-diesel (W/D) emulsion fuel is a potential alternative fuel that can simultaneously lower NOx exhaust emissions and improves combustion efficiency. Additionally, there are no additional costs or engine modifications required when using W/D emulsion fuel. The proportion of water added and engine speed is crucial factors influencing engine behavior. This study aims to examine the impact of the W/D emulsion diesel fuel on engine performance and NOx pollutant emissions using a compression ignition (CI) engine. The emulsion fuel had water content ranging from 0 to 30% with a 5% increment, and 2% surfactant was employed. The tests were performed at speeds ranging from 1000 to 3000 rpm. All W/D emulsion fuel was compared to a standard of pure diesel in all tests. A four-cylinder, four-stroke, water-cooled, direct-injection diesel engine test bed was used for the experiments. The performance and exhaust emissions of the diesel engine were measured at full load and various engine speeds using a dynamometer and an exhaust gas analyzer, respectively. The second purpose of this study is to illustrate the application of two optimizers, grey wolf optimizer (GWO) and intelligent grey wolf optimizer (IGOW), along with using multivariate polynomial regression (MPR) to identify the optimum (W/D) emulsion blend percentage and engine speed to enhance the performance, reduce fuel consumption, and reduce NO_X exhaust emissions of a diesel engine operating. The engine speed and proportion of water in the fuel mixture were the independent variables (inputs), while brake power (BP), brake thermal efficiency (BTE), brake-specific fuel consumption (BSFC), and NOx were the dependent variables (outcomes). It was experimentally observed that utilizing emulsified gasoline generally enhances engine performance and decreases emissions in general. Experimentally, at 5% water content and 2000 rpm, the BSFC has a minimal value of 0.258 kJ/kW·h. Under the same conditions, the maximum BP of 11.6 kW and BTE of 32.8% were achieved. According to the IGWO process findings, adding 9% water to diesel fuel and running the engine at a speed of 1998 rpm produced the highest BP (11.2 kW) and BTE (33.3%) and the lowest BSFC (0.259 kg/kW·h) and reduced NOx by 14.3% compared with the CI engine powered by pure diesel. The accuracy of the model is high, as indicated by a correlation coefficient R² exceeding 0.97 and a mean absolute error (MAE) less than 0.04. In terms of the optimizer, the IGWO performs better than GWO in determining the optimal water addition and engine speed. This is attributed to the IGWO has excellent exploratory capability in the early stages of searching. Full article

In an attempt to avoid serious problems that can affect the efficiency of refueling ground-operated vehicles and aircraft during military operations, the Armed Forces of the North Atlantic Treaty Organization (NATO) are introducing the use of a unique fuel for both air and land use. The fuel that has been selected is the F-34, similar to Jet A-1, which is used in civil aviation, in order to replace diesel fuel in many applications. It has to be mentioned that tests performed with this fuel, which is kerosene type on the high frequency reciprocating rig (HFRR) have shown that such fuel is responsible for severe wear. This very high wear is related to the very low lubricity of aviation fuel. Having the idea to improve the lubricity of aviation fuel to the level of fuels used in compression ignition engines (diesel fuel), seven N,N-Bis(2-ethoxyethyl) fatty acid amides were formulated from various vegetable oils (sunflower oil, soybean oil, cottonseed oil, olive oil, tobacco seed oil, coconut oil, used frying oil), and they were evaluated as lubricity improvers of the aviation fuel. The required tribological measurements for lubricity rating were carried out by employing ISO 12156-1 test method on an HFRR instrument. The test conditions during the measurements were in the range of 55% to 58% for the relative humidity and 24 °C for the temperature. The results from the tribological measurements showed that all N,N-Bis(2-ethoxyethyl) fatty acid amides used were rated as efficient in order to provide an acceptable mean wear scar diameter (below 460 μm) at concentrations from 150 to 300 ppm. Additive concentrations below 150 ppm did not improve the lubricity at the required level. The increase of N,N-Bis(2-ethoxyethyl) fatty acid amides at concentrations over 300 ppm did not have any significant decrease in the wear scar diameter. A comparison between the N,N-Bis(2-ethoxyethyl) fatty acid amides showed that those formulated by non-polyunsaturated oils like olive oil and coconut oil seem to have better lubricity improver characteristics. Full article

Poly(oxymethylene) dimethyl ether (OME) are a much-discussed and promising synthetic and renewable fuel for reducing soot and, if produced as e-fuel, CO₂ emissions. OME production is generally based on the platform chemical methanol as an intermediate. Thus, the OME production cost is strongly dependent on the methanol cost. This work investigates OME production from methanol. Seven routes for providing methanolic formaldehyde solutions are conceptually designed for the first time and simulated in a process simulator. They are coupled with a state-of-the-art OME synthesis to evaluate the economics of the overall production chain from methanol to OME. For a plant size of 100 kt/a, the average levelized product cost of OME is 79.08 EUR/t plus 1.31 times the cost of methanol in EUR/t. Full article