Solid Fuel Chemistry最新文献

In recent years, ethanol has emerged as a popular additive for biodiesel/diesel blends, to decrease the carbon footprint left by combustion products. Nanoparticles added with biodiesel/diesel have promoted greater ignition and combustion rate, lower ignition delay, and reduced exhaust emissions. This study evaluated the filter performance of prosopis juliflora biodiesel and bioethanol mixed with diesel with selected nano particles, namely graphene(G) and graphene oxide(GO) nanoparticles. Different nano additive proportions of 50, 100, 150, 200, 250, and 300 ppm were blended in diesel blends of BED20 (10% biodiesel + 10% ethanol + 80% diesel) and the filtration characteristics of these fuel blends were evaluated to determine the best nanoparticle mixture. Tamson filter blocking tendency (TFBT) apparatus was utilized to determine filter blocking tendency (FBT). The filtration performance was measured by following the ASTM standard (D2068-14) for initial pressure, fuel temperature and fuel flow rate. Results found that the FBT tends to rise with the addition of additive proportion. It was seen that FBT values of 200 ppm of grapheme (G) nanoparticles and 250 ppm graphene oxide (GO) were found to be 1.32 and 1.4 respectively which inline the acceptable range (1.41).

Air leakage between goaf and working face increases the risk of spontaneous combustion in goaf, posing a threat to production safety in the working face. The study uses CFD software to simulate the impact of wind speed and goaf depth on the distribution of air leakage, oxygen concentration, and carbon monoxide concentration. It was found that as wind speed increases, the air leakage plume and CO gas concentration move towards the return air side, and the air leakage speed at the working face boundary and tases with depth, and the range of CO distribution and the range of oxygen distribution on the intake side decrease. Based on this, a dynamic measurement method for air leakage is proposed. The error of wind resistance value comparison is within ±5%, indicating the feasibility of dynamic quantitative measurement of the air leakage flow field at the working face, which can improve the accuracy of air leakage measurement in the working face. Then the method was applied in the 509 working face of Ma Di Liang coal mine. The results show that the average air leakage volume in the goaf of the 509 working face is 152.19 m³/min, and the average air leakage velocity is 0.41 m/s.

The particle sizes of main mineral compounds in the structure of lignite were determined using physical methods (SAXS, TEM, and XRD analysis) and chemical processes of selective dissolution. It has been shown that calcium and magnesium compounds in the structure of lignite were present in the form of small nanoparticles with sizes of about 10 nm. Particles consisting of aluminum and iron compounds had larger sizes of about 20–35 nm. Silica-containing particles in the structure of lignite had sizes of 100 nm or greater.

The results of a study of rare-earth metals in dictyonema shales of the Paleozoic Baltic sedimentary basin are presented. In the territory of the studied Kaibolovo–Gostilitsy prospecting area, high up to potentially industrial rare-earth element (REE) contents were confirmed based on a large factual and analytical material. The average REE concentration was 289 g/t with maximums up to 724 g/t. REEs were found in dictyonema shales in various forms (mineral, organic, ionic, molecular, and colloidal). The occurrence of REEs in the mineral matter of dictyonema shales predominated. The fraction of heavy (and most valuable) lanthanides (15.6% on a total basis) in the test dictyonema shales was higher by a factor of 2 than that in ore deposits. This fact and the presence of large geological REE resources in the dictyonema shales of the Baltic region of Russia determine the need for their integrated development with other associated components.

A kinetic model of the formation of a pyrocarbon layer on the surface of filaments of a carbonized PAN fiber is proposed. The resulting kinetic model is confirmed by experimental data. The formation of a pyrocarbon layer on an individual carbon fiber filament is described with a prediction of an increase in the thickness of the carbon layer on a bundle of filaments after a long cycle of CVD.

The active coals obtained from high-moor peat of the European North of Russia by thermochemical activation with NaOH and various types of pre-treatment (debituminization and pre-pyrolysis) were studied. Based on the results of the low-temperature adsorption of nitrogen, the resulting active coals belonged to adsorbents whose structure was dominated by micropores. The specific surface area of coal pores reached 2330 m²/g, and the total pore volume was 1.44 cm³/g. The introduction of the stage of pre-pyrolysis made it possible to increase significantly the yield of active coals. This increase was 28 or 97% for the initial peat or debituminized samples, respectively; moreover, the sorption characteristics were significantly improved. It has been shown that weakly decomposed high-moor peat of the European North of Russia can be used as a raw material for the production of high-efficiency carbon microporous adsorbents.

The energy and spectral kinetic characteristics of the ignition of anthracite microparticle powders with a bulk density of 0.5 g/cm³ were measured when exposed to continuous wave laser radiation at wavelengths λ = 450 and 808 nm with an exposure time of 1 s. The ignition delay times were measured depending on the radiation power density, and the critical values of the ignition energy density of anthracite samples were determined. The energy costs for igniting anthracite for radiation with λ = 450 nm are lower than those for radiation with λ = 808 nm. In the emission spectra of anthracite resulting from the absorption of laser radiation, a glow associated with the release and ignition of volatile substances (CO flame and glow of excited CO, C₂, and H₂O molecules) and a thermal glow associated mainly with the heated surface of the samples and the emission of hot carbon particles were observed.

The influence of metal-rolling production waste and iron nitrate on the characteristics of the process of layer combustion of coal was investigated. Coal of T grade was used as a solid fuel. Metal scale and iron nitrate were introduced into the fuel by mechanical mixing. According to XRD analysis data, the phases of iron oxide Fe₃O₄ and manganese oxide Mn₃O₄ were identified in the metal scale. The process characteristics of the combustion of test samples were studied using high-speed video recording in a combustion chamber at a heating medium temperature of 700°C. The process of activated layer combustion of coal was also scaled up using a solid fuel boiler unit. It has been experimentally established that the use of metal scale and iron nitrate led to an increase in the reactivity of the fuel, as evidenced by a decrease in the ignition delay time. The carbon loss and the concentration of CO formed in the gas-phase combustion products were reduced due to the intensification of the combustion process.

The results of obtaining titanium carbide by a vacuum-free electric arc method using various types of biocarbon obtained by classical pyrolysis of biomass waste, such as tangerine peel, pomelo peel, banana peel, pine nut shells, and walnut shells, are presented. An analysis of X-ray diffraction patterns of the synthesized materials showed the repeatability of the experiment with the receipt of diffraction maximums indicating the formation of a cubic structure of titanium carbide. An analysis of the thermal oxidation of the resulting powders showed that the process proceeded slowly up to 1000°C, but the rate of oxidation increased significantly with temperature. It has been established that the weight of the studied titanium carbide powders obtained using various types of carbon increased upon thermal heating in an oxidizing atmosphere, as confirmed by thermogravimetric analysis.

To investigate the desorption behavior of O₂ through CO₂/N₂ injection in the gob of a gassing mine, we focused on the adsorption configuration of coal containing O₂–CH₄. The mechanism underlying the enhancement of O₂ desorption in coal due to CO₂/N₂ injection was elucidated using the Grand Canonical Ensemble Monte Carlo (GCMC) and Molecular Dynamics (MD) methods. Furthermore, the impact of CH₄ on O₂ desorption was unveiled by detailed calculations and studies of energy variation, concentration distribution, and diffusion coefficients of oxygen.Our findings indicate the following: (1) CO₂ and N₂ facilitate the displacement of oxygen primarily by occupying adsorption sites. The CO₂–O₂ model exhibits a significantly higher concentration of free O₂ molecules compared to the N₂–O₂ model, and the CO₂–O₂–CH₄ model surpasses the N₂–O₂–CH₄ model in free O₂ molecules. (2) The total energy of the CO₂–O₂ model is lower than that of the N₂–O₂ model, indicating greater stability in the former. Similarly, the total energy of the CO₂–O₂–CH₄ model is lower than that of the N₂–O₂–CH₄ model, highlighting its superior stability. It is concluded that CO₂ injection is more effective in promoting oxygen desorption than N₂, regardless of the presence of methane. (3) Under equivalent injection pressure, the root mean square displacement of O₂ in the CO₂–O₂ system surpasses that in the N₂–O₂ system. Furthermore, compared to the N₂–O₂–CH₄ system, the CO₂–O₂–CH₄ system exhibits a larger root mean square displacement of O₂, signifying higher O₂ molecule activity. The diffusion coefficient of O₂ in the CO₂–O₂ system is higher, underscoring the superior effectiveness of CO₂ in promoting O₂ desorption.In summary, our research outcomes offer valuable theoretical insights for fire prevention technology in goaf.