Search Results (19)

This study investigates the thermal decomposition, ignition, combustion, and gasification processes of composite fuels derived from anthracite coal and pine sawdust. The research highlights the non-additive behavior of composite fuels, demonstrating enhanced reactivity and combustion efficiency compared to simple mixtures. Thermogravimetric analysis (TGA) revealed distinct stages of thermal decomposition, with composite fuels exhibiting combined processes of volatile release and coke residue decomposition, unlike mixtures. Ignition experiments in a vertical tubular furnace showed reduced flash delay times for composites, attributed to the formation of active surface centers during mechanical activation. Flare combustion studies confirmed more stable and complete combustion of composites, achieving higher temperatures and improved flame stability. Plasma gasification experiments indicated that composite fuels provide more uniform gas evolution, with higher yields of hydrogen (H₂) and carbon monoxide (CO), while reducing nitrogen oxide (NO) emissions. The findings underscore the potential of composite fuels for optimizing energy efficiency and reducing environmental impact in coal-fired power plants, supporting the transition to sustainable energy solutions. Full article

A series of experiments were conducted on quartz sand beds wetted with transformer oil under initial temperatures of 80–140 °C and fuel–sand mass ratios of 1:4–1:8. The flame spreading process over the fine sand bed wetted with limited liquid fuel can be divided into the development and quasi-steady stages. Experimental results reveal that the flame spread rate in the quasi-steady stage increases with the initial temperature and fuel–sand mass ratio. The effect of sand bed width on flame spread depends on the initial temperature. The flame spread rate is insensitive to the sand bed width at low initial temperatures; however, it increases with sand bed width at an initial temperature close to the flash point of liquid fuel. This discrepancy mainly results from the enhanced capillary effect due to the decreased viscosity at high initial temperatures. The capillary effect is the dominant factor determining fuel vaporization and, thus, the flame spread rate, and flame radiation plays an increasing role with increasing initial temperature. The maximum flame height is sensitive to sand bed width and fuel–sand mass ratio but changes little with initial temperature. A dimensionless model was proposed to predict the normalized flame height. Full article

A flash smelting furnace operation is based on the exothermic reduction of copper concentrates in the combustion shaft, and these reactions occur at high temperatures (1250–1350 °C), where flame control is fundamental to optimizing copper reduction. Furthermore, inherent physicochemical reactions of the reduction process have been shown to emit spectral lines in the visible-near infrared spectrum (250–900 nm). Thus, an optoelectronic sensor prototype is proposed and developed for flame measurements of an industrial copper concentrate flash smelting furnace. The sensor system is composed of a high-temperature optical fiber probe, which functions as a waveguide to capture the emitted flame radiation and a visible-near infrared spectrometer. From the measured radiation, flame temperature and flame dynamics are analyzed. Flame temperature is estimated using the two-wavelength temperature estimation method, and flame dynamics are defined as variations in the total emissive power, which are studied in the time and frequency domain via the Fourier Transform method. These combustion dynamics are then used to create a flame instability index, which is used to characterize the flame combustion quality. The combination of this index and sensor platform provides a powerful tool to aid in proper flame control. Full article

This study applied a risk assessment technique to the steam reforming process in hydrogen production facilities to generate baseline data for preparing safety protocols in related workplaces. To this end, consequence analysis (CA) was conducted using DNV-PHAST v.8.9., focusing on the reforming process, which operates at the highest temperature and pressure among related processes. This study predicted jet fire damage resulting from the total failure of a 65 mm syngas pipe at the rear end of the reformer, with a projected flame length of up to 23.6 m based on a radiant heat of 5 kW/m². As per the assessment, a vapor cloud explosion (VCE) caused damage of up to 42.6 m at an overpressure of 0.07 bar (1 psi), while a flash fire had an impact range of approximately 12.7 m based on hydrogen’s LFL (lower flammable limit). This quantitative risk assessment of the general steam reforming process provides valuable basic data for the design and operation of related facilities. Full article

Graphite anode materials and carbonate electrolyte have been the top choices for commercial lithium-ion batteries (LIBS) for a long time. However, the uneven deposition and stripping of lithium cause irreversible damage to the graphite structure, and the low flash point and high flammability of the carbonate electrolyte pose a significant fire safety risk. Here, we proposed a multifunctional electrolyte additive diphenylphosphoryl azide (DPPA), which can construct a solid electrolyte interphase (SEI) with high ionic conductivity lithium nitride (Li₃N) to ensure efficient transport of Li⁺. This not only protects the artificial graphite (AG) electrode but also inhibits lithium dendrites to achieve excellent electrochemical performance. Meanwhile, the LIBS with DPPA offers satisfactory flame retardancy performance. The AG//Li half cells with DPPA-0.5M can still maintain a specific capacity of about 350 mAh/g after 200 cycles at 0.2 C. Its cycle performance and rate performance were better than commercial electrolyte (EC/DMC). After cycling, the microstructure surface of the AG electrode was complete and flat, and the surface of the lithium metal electrode had fewer lithium dendrites. Importantly, we found that the pouch cell with DPPA-0.5M had low peak heat release rate. When exposed to external conditions of continuous heating, DPPA significantly improved the fire safety of the LIBS. The research of DPPA in lithium electrolyte is a step towards the development of safe and efficient lithium batteries. Full article

Difficult to handle seed material and poor germination commonly limit the uptake of native grasses in restoration and commercial-scale seeding efforts. Seed enhancement technologies (SETs) offer valuable solutions for improving the handling of seed material and optimising germination. This study considered eight widespread Australian native grasses; two representative of Mediterranean to temperate climates (‘cool-climate’ species) and six representative of arid to subtropical climates (‘warm-climate’ species). Through a series of experiments, this study logically selected and applied SET treatments to improve seed handling and germination for each study species. Seed handling was prioritised and addressed using flash flaming and/or acid digestion, while hydropriming was used following seed-handling treatments to enhance germination. Flash flaming and acid digestion were both applied to successfully reduce or remove bulky floret structures while maintaining or improving germination. Flaming at 110 ± 10 °C with continuous exposure for 10 min and acid digestion concentrations of 75–80% with exposure times of 1–2.5 min were generally successful. Sub-optimal concentrations of sulphuric acid often compromised germination. Hydropriming did not improve germination outcomes when applied following flaming or acid digestion. Optimising SETs for germination, emergence and establishment in different environments, and the viability and costs of application on larger seed batches are key considerations for the implementation and upscaling of SETs in the future. Full article

Fires are considered among the most dangerous accidents on manned spacecraft. That is why several programs of combustion experiments were implemented at the International Space Station (ISS) since 2008. In the experiments with n-heptane and n-dodecane droplet combustion, a new phenomenon was discovered, namely, the phenomenon of the radiative extinction of a burning droplet with subsequent multiple flashes of flame. In this paper, n-dodecane droplet ignition, combustion, radiative extinction, and subsequent low-temperature oxidation with multiple flashes of cool, blue, and hot flames under microgravity conditions are studied computationally. The mathematical model takes into account multiple elementary chemical reactions in the vicinity of a droplet in combination with heat and mass transfer in liquid and gas, heat release, convection, soot formation, and heat removal by radiation. The model is based on the non-stationary one-dimensional differential equations of the conservation of mass and energy in liquid and gas phases with variable thermophysical properties within the multicomponent diffusion concept in the gas phase. Calculations confirm the important role of the soot shell formed around the droplet and low-temperature reactions in the phenomenon of droplet radiative extinction with multiple flame flashes in the space experiment at the ISS. Calculations reveal the decisive role of the blue flame, arising due to the decomposition of hydrogen peroxide, in the multiple flame flashes. Calculations with forced ignition of the droplet reveal the effect of the ignition procedure on droplet evolution in terms of the timing and the number of cool, blue, and hot flame flashes, as well as in terms of the combustion rate constant of the droplet. Calculations with droplet self-ignition reveal the possible existence of new modes of low-temperature oxidation of droplets with the main reaction zone located very close to the droplet surface and with only partial conversion of fuel vapor in it. Full article

The conversion of polymer waste, food waste, and biomasses through thermochemical decomposition to fuels, syngas, and solid phase, named char/biochar particles, gives a second life to these waste materials, and this process has been widely investigated in the last two decades. The main thermochemical decomposition processes that have been explored are slow, fast, and flash pyrolysis, torrefaction, gasification, and hydrothermal liquefaction, which produce char/biochar particles that differ in their chemical and physical properties, i.e., their carbon-content, CHNOS compositions, porosity, and adsorption ability. Currently, the main proposed applications of the char/biochar particles are in the agricultural sector as fertilizers for soil retirement and water treatment, as well as use as high adsorption particles. Therefore, according to recently published papers, char/biochar particles could be successfully considered for the formulation of sustainable polymer and biopolymer-based composites. Additionally, in the last decade, these particles have also been proposed as suitable fillers for asphalts. Based on these findings, the current review gives a critical overview that highlights the advantages in using these novel particles as suitable additives and fillers, and at the same time, it shows some drawbacks in their use. Adding char/biochar particles in polymers and biopolymers significantly increases their elastic modulus, tensile strength, and flame and oxygen resistance, although composite ductility is significantly penalized. Unfortunately, due to the dark color of the char/biochar particles, all composites show brown-black coloration, and this issue limits the applications. Full article

This research effort is geared towards revealing the latent potential of discarded shoe polish that might be repurposed as an asphalt fluxing agent for the construction of durable and sustainable road surfaces. To drive this creative invention, the effect of various proportions of waste shoe polish (e.g., 5, 10 and 15 wt. % WSP) on the performance of base AP-5 bitumen was inspected in great detail. A meticulous investigation of the chemical, physical, and rheological properties of the resultant combinations was carried out using a variety of state-of-the-art laboratory techniques, specifically: thin-layer chromatography-flame ionization detection (TLC-FID), Fourier transform-infrared spectroscopy (FT-IR), needle penetration, ring-and-ball softening point, Brookfield viscometer, ductility, flash/fire points, dynamic shear rheometer (DSR), multiple stress-creep recovery (MSCR), and bending beam rheometer (BBR) tests. The Iatroscan data disclosed that the continuous feeding of binder with WSP had a minor impact on SARA fractional distribution, regardless of aging. According to the FT-IR scan, the stepwise addition of WSP to the binder did not result in any significant chemical alterations in the blends. The combined outcomes of the DSR/BBR/empirical test methods forecasted that the partly bio-sourced additive would greatly improve the mixing–compaction temperatures, workability, and coating–adhesion properties of bituminous mixtures while imparting them with outstanding anti-aging/cracking attributes. In short, the utilization of waste shoe polish as a fluxing agent for hot asphalt mix production and application is not only safe, feasible, and affordable, but it has the potential to abate the pollution caused by the shoe-care market while simultaneously enhancing the overall performance of the pavement and extending its service lifespan. Full article

The main purpose of this work is to illustrate the flame retardant properties of corn starch that is used as an additive to the classic electrolytes in lithium-ion cells. The advantages of using natural biomass include the increased biodegradability of the cell, compliance with the slogan of green chemistry, as well as the widespread availability and easy isolation of this ingredient. Due to the non-Newtonian properties of starch, it increases work safety and prevents the occurrence of thermal runaway as a shear-thinning fluid in the event of a collision. Thus, its use may, in the future, prevent explosions that affect electric cars with lithium-ion batteries without significantly degrading the electrochemical parameters of the cell. In the manuscript, the viscosity test, flash point measurements, the SET (self-extinguishing time) test and conductivity measurements were performed, in addition to the determination of electrochemical impedance spectroscopy (EIS) for the anode system. Additionally, the kinetic and thermodynamic parameters, for both flow and conductivity, were determined for a deeper analysis; this constitutes the scientific novelty of this study. Through mathematical analysis, it was shown that the optimal amount of added starch is 5%. This is supported primarily by the determined kinetic and thermodynamic parameters and the fact that the system did not gel during heating. Full article

The present paper compares the flow structure and flame dynamics during combustion of methane and syngas in a model gas-turbine swirl burner. The burner is based on a design by Turbomeca. The fuel is supplied through injection holes between the swirler blades to provide well-premixed combustion, or fed as a central jet from the swirler’s centerbody to increase flame stability via a pilot flame. The measurements of flow structure and flame front are performed by using the stereo particle image velocimetry and OH planar laser-induced fluorescence methods. The measurements are performed for the atmospheric pressure without preheating and for 2 atm with the air preheated up to 500 K. The flow Reynolds numbers for the non-reacting flows at these two conditions are 1.5 × 10³ and 1.0 × 10³, respectively. The flame dynamics are analyzed based on a high-speed OH* chemiluminescence imaging. It is found that the flame dynamics at elevated conditions are related with frequent events of flame lift-off and global extinction, followed by re-ignition. The analysis of flow structure via the proper orthogonal decomposition reveals the presence of two different types of coherent flow fluctuations, namely, longitudinal and transverse instability modes. The same procedure is applied to the chemiluminescence images for visualization of bulk movement of the flame front and similar spatial structures are observed. Thus, the longitudinal and transverse instability modes are found in all cases, but for the syngas at the elevated pressure and temperature the longitudinal mode is related to strong thermoacoustic fluctuations. Therefore, the present study demonstrates that a lean syngas flame can become unstable at elevated pressure and temperature conditions due to a greater flame propagation speed, which results in periodic events of flame flash-back, extinction and re-ignition. The reported data is also useful for the validation of numerical simulation codes for syngas flames. Full article

Knowledge of the drying properties of tobacco in high temperatures above 100 °C and its dust are crucial in the design of dryers, both in the optimization of the superheated-steam-drying process and in the correct selection of innovative explosion protection and mitigation systems. In this study, tobacco properties were determined and incorporated into the proposed model of an expanding superheated steam flash dryer. The results obtained from the proposed model were validated by using experimental data yielded during test runs of an industrial scale of a closed-loop expansion dryer on lamina cut tobacco. Moreover, the explosion and fire properties of tobacco dust before and after the superheated steam-drying process at 160, 170, 180, and 190 °C were experimentally investigated, using a 20 L spherical explosion chamber, a hot plate apparatus, a Hartmann tube apparatus, and a Godbert–Greenwald furnace apparatus. The results indicate that the higher the drying temperature, the more likely the ignition of the dust tobacco cloud, the faster the explosion flame propagation, and the greater the explosion severity. Tobacco dust is of weak explosion class. Dust obtained by drying with superheated steam at 190 °C is characterized by the highest value of explosion index amounting to 109 ± 14 m·bar·s⁻¹, the highest explosion pressure rate (405 ± 32 bar/s), and the maximum explosion pressure (6.7 ± 0.3 bar). The prevention of tobacco-dust accumulation and its removal from the outer surfaces of machinery and equipment used in the superheated steam-drying process are highly desirable. Full article

The demand for native grasses is increasing in restoration and agriculture, though their use is often limited due to seed handling challenges. The external structures surrounding the grass seed (i.e., the floret) possess hairs, awns, and appendages which create blockages in conventional seeding equipment. Flash flaming is a patented technology which allows precision exposure of floret material to flames to singe off hairs and appendages. We used two grasses native to Mediterranean ecosystems of Western Australia (Amphipogon turbinatus R.Br. and Neurachne alopecuoidea R.Br.) to evaluate the effects of different flaming techniques on flow properties and germination. Flaming significantly improved flowability in both species and had both neutral (A. turbinatus) and negative (N. alopecuroidea) effects on germination. Flaming torch size influenced germination, though flaming temperature (low or high) and whether this was kept constant or alternating had no effect. The best evaluation of germination following flaming was achieved by cleaning flamed florets to seed and/or germinating in the presence of karrikinolide (KAR₁) or gibberellic acid (GA₃). We suggest that flaming settings (particularly torch size) require species-specific evaluation and optimisation. Removing seeds from flamed florets and germination testing this material in the presence of stimulants may be a useful protocol for future flaming evaluations. Full article

Algae are emerging as a major and reliable source of renewable biodiesel that could meet the energy requirements of the world. Like plants, algae produce and store oils in their cells. Algal samples were collected from Gujrat District, Pakistan, their oil content was analyzed, and the best oil producing alga was identified as Spirogyra crassa. After collecting sample, oil was extracted using the Soxhlet extraction method. Spirogyra oil was characterized physico-chemically for the evaluation of its quality. Acid value, density, saponification value, peroxide value, as well as viscosity and iodine values were determined and their values were 16.67 ± 3.53 mg KOH/g, 0.859 ± 0.050 g/cm³, 165.33 ± 13.20 mg KOH/g, 4.633 ± 0.252 meq/kg, 5.63 ± 0.833 mm²/mL, and 117.67 ± 13.01 mg I₂/g, respectively. Chemical as well as enzymatic transesterification protocols were employed for biodiesel production using NaOCH₃ and NOVOZYME-435, respectively. Different reactions parameters involved in transesterification were optimized by the response surface methodology. The optimized yield of biodiesel (77.3 ± 1.27%) by the chemical transesterification of algal oil (spirogyra) was observed by carrying out the reaction for 90 minutes at a reaction temperature of 45 °C using 1.13% catalyst (NaOCH₃) concentration and 6:1 methanol:oil. Meanwhile, for enzymatic transesterification, the optimized yield (93.2 ± 1.27%) was obtained by conducting the reaction for 42.5 h at the temperature of 35 °C using 1% enzyme concentration and 4.5:1 methanol:oil. Fuel properties, including flash point, pour point, cloud point, fire point, kinematic viscosity, and density, were determined and their values are 125.67 ± 2.11 °C, −19.67 ± 0.8 °C, −13 ± 1 °C, 138.667 ± 2.52 °C, 5.87 ± 2.20 mm²/mL, and 0.85 6 ± 0.03 g/cm³, respectively. Fourier transfer infrared spectroscopic (FTIR) and Gas chromatography with flame ionization detector (GC-FID) analysis were performed for the monitoring of the transesterification process and fatty acid methyl acid (FAME) profiling, respectively. Full article

Fire propagation and burning characteristics of upward flame spread over flexible polyurethane (FPU) foam board were investigated under coupling effects of pressure and orientation. As a further comparative research of our previous work, three pressures (70, 85 and 100 kPa) and four fuel surface inclination angles (0°, 30°, 60°, 90°) were applied, respectively, as before, to study the variation of typical parameters including flame spread rate (FSR), burning rate, heat transfer components, flame length, etc. First, a phenomenological interpretation was taken to show the special spreading process with melting flow combustion and flash burning observed. Second, an overall theoretical analysis was proposed to reveal the individual or coupling effects of pressure and inclined burning surface on spreading behavior. A semi-quantitative correlation was developed and formulated to show the tendency of FSR as a function of pressure, inclination and other burning parameters, which was validated by data in paper. Meanwhile, comparison of detailed differences between upward and downward spread was conducted to give a full insight on FPU fire development. At last, comprehensive discussions of coupling effects on variation of spreading characteristics and heat transfer mechanisms were performed based on fire dynamics. Full article