Solid Fuel Chemistry最新文献

The effect of ultrasonic treatment modes on the microstructure and structural and rheological properties of oil emulsions with distilled water and formation water was studied. The emulsions were treated in an ultrasonic field (frequency, 22 kHz; intensity, 2, 6, and 18 W/cm²). The microstructure of the emulsions was analyzed using an AXIO LAB.A1 optical microscope (Carl Zeiss, Germany). The analysis of variances of the micrographs of the emulsions was performed to reveal the effect of the treatment conditions and the type of dispersed phase on the mean droplet diameter, dispersion, and position of the peak of water droplet size distribution in the emulsion. The rheological parameters of the emulsions before and after ultrasonic treatment were measured using a HAAKE Viscotester iQ rheometer (Thermo Scientific, the United States). For highly viscous oil with a high content of resin–asphaltene components, the degree of dispersion of water droplets decreased after pulsed ultrasonic treatment at a field intensity 6 W/cm² in two modes (5 cycles with 10 s of operation and 10 s of rest; 10 cycles with 5 s of operation and 5 s of rest).

The results of laboratory studies and pilot tests of plugging materials developed by the authors' team for eliminating steam and water breakthroughs from rock mass into oil mine workings and for filling voids in the rock mass in places where steam breakthroughs occurred are presented. Conclusions on the influence of individual components of the compositions, which allowed them to be combined to achieve the required properties of the material, were made. The tests were carried out at an experimental section of the Yaregskoye oil mine, and they showed the effectiveness of the developed materials. It is planned to further develop this work, including testing the developed plugging compositions for surface steam injection wells.

A mechanism is proposed for the cryostructuring of aqueous solutions of polyvinyl alcohol, that is, for converting the solutions from a fluid state into elastic bodies (cryogels). In addition to the theoretical justification for the mechanism, experimental results of rheological and spectroscopic studies of the resulting cryogels are also presented. An explanation is given for the significant difference between the cryostructuring temperature of an aqueous solution of polyvinyl alcohol and the melting temperature of elastic cryogels formed from it.

Thus article presents the results of studies of polyaromatic hydrocarbons (PAHs) in oil shales of the Barzas (Barzassite) and Budagovo (Sapropelite) deposits and their ash residues obtained upon thermal destruction at T = 300, 500, and 750°C with free access of oxygen. A set of physicochemical methods of analysis (extraction, infrared spectroscopy, and high-performance liquid chromatography) made it possible to establish the composition of priority PAHs of the oil shales and track changes occurring under thermal action. As a result of this work, it was shown that the yield of oil shale ash residues depended on the initial composition of oil shales and ranged from 5 to 82 wt % depending on the destruction temperature. The PAH content of the ash residues did not exceed 9.5 rel %.

The infiltration of diesel fuel (DF) into an Arctic peat deposit three months after its contamination was considered. Concentration of pollutants (92%) in the upper 0–10 cm of the section was revealed. Qualitative and quantitative parameters of the distribution of DF components in peat under Arctic conditions were analyzed; they indicated a gel filtration mechanism of differentiation of DF composition in the peat deposit.

The effect of electromagnetic field on colloidal dispersion properties of water–oil emulsions of two resinous low-paraffin oils was studied. It was shown that the maximum result of water–oil emulsion stratification was achieved after 15-min treatment at frequencies of 250 and 500 Hz and voltages of 17 and 15 kV for 10 and 30 wt % emulsions, respectively. With increasing time of emulsion treatment, the size and number of droplets in the oil phase decreased, and the residual water content of the treated emulsions after stratification did not exceed 0.5 wt %. In an electromagnetic field, the drop–drop coalescence process in the emulsion was intensified due to the rapid destruction of the armor shells of water globules, the formation of new resin–asphaltene aggregates of a larger or smaller size, and the redistribution of components between the dispersion medium and the dispersed phase.

The article presents the results of a study of asphaltenes isolated from the liquid products of initiated cracking of two tar samples at 500°C in the presence of a calcium acetate additive. Characteristic changes in the composition of cracking products depending on the amount of the additive were shown. It was established that the formation of solid condensation products depended not only on the initial concentration of asphaltenes but also on their structure. Changes in the structural-group parameters of asphaltenes in the course of the initiated cracking of tars were studied. A distinctive feature of tar cracking in the presence of calcium acetate was that the additive promoted both the destruction of structural blocks and a significant decrease in their number in the composition of asphaltene molecules. In addition, the averaged asphaltene molecules became more compact due to the destruction of aliphatic substituents and naphthenic rings, and the fraction of condensed aromatic structures in their composition increased significantly.

In order to better understand the microstructure characteristics of soft and hard coal and its influence on gas adsorption capacity, three groups of soft and hard coal samples with different maturities were collected for measurements from Ordos Basin. CH₄ isothermal adsorption experiments were performed to analyze the gas adsorption characteristics. Pore distribution and oxygen-containing groups of these soft and hard coals were detected by low-pressure N₂ adsorption and Fourier Transform Infrared Spectroscopy (FTIR), respectively. For the collected FTIR spectrum, the peak-fitting method is used to semi-quantitatively study the distribution of oxygen-containing groups. Comparison of microstructure characteristics and methane adsorption capacity has also been made between soft and hard coal samples. The results showed that soft coals has smaller pore diameter and the micropore and mesopore surface area is 43.2–75.1 and 12.2–41.1% greater than that of corresponding hard coal, respectively, but the macropore surface area is 18.9–66.7% less than that of hard coals. The aromaticity of hard bituminous coals is smaller than that of the corresponding soft coals, while the peak areas of carbonyl and hydroxyl groups are obviously larger than that of the corresponding soft bituminous coals. However, the distribution of oxygen-containing groups in soft and hard anthracite exhibits the opposite trend. Tectonic deformation contributes to the decline of oxygen-containing groups and can enhance the maturity and pore surface area of bituminous coals, exhibiting superior methane adsorption property compared with hard bituminous coals. Though soft anthracite has developed micropore/mesopore structures, its lower maturity and higher content of oxygen-containing groups lead to the decline of gas adsorption capacity. Gas adsorption behaviors of coal are closely related to the complex microstructures, and the combined effects of physical structures and chemical groups should be taken into account.

Enhancing the performance of PEMFCs significantly depends on the efficient diffusion of gases and the transport of water molecules. In this study, we utilized the high porosity and electrical conductivity of carbon fiber to promote the autonomous growth of lotus leaf graphene along the carbon fiber substrate. This innovation enables the creation of a gas cathode microporous layer for aspirated PEMFCs, which demonstrates high structural stability, minimal mass transfer resistance, and cost-effectiveness. Efficient gas diffusion and water transport are critical, as inadequate management of these factors can negatively impact battery lifespan and stability. The PEMFC cell with Gra/CC-60 exhibits a maximum current density of 1480 mA/cm², outperforming other samples. Additionally, the peak power density reaches 398.9 mW/cm² at 0.43 V. Remarkably, after 12 hours of operation at high current density, the PEMFC cell shows only a 7.94% drop in current density. This research paves the way for the development of microporous layers for fuel cells, sensors, and catalytic modules, while also introducing a novel approach to the selection and design of carbon materials.

To investigate the influence of water content on coal combustion characteristics, bituminous coal was collected as the research target from the Wusitai Coal Mine. The combustion characteristic parameters of coal samples with various water contents were measured by cone calorimeter, and the combustion efficiency of coal samples was analyzed. The spontaneous combustion characteristics of samples are significantly affected by moisture within coal. As the rise of moisture content, the ignition time of bituminous coal is firstly reduced and then it is enhanced. The coal sample with moisture content of 10.36% has the fastest ignition. The total smoke discharge, the peak heat release rate and the flue gas generation rate of bituminous coal samples are firstly decreased, then increased and finally reduced with the increase of water content. In the later stage of combustion, the CO generation rate is the smallest for the bituminous sample with water content of 6.59%, while it is the largest for the sample with 18.78% content of moisture. Large moisture content makes the coal sample incomplete combustion, which can improve the CO production rate. The combustion efficiency of bituminous coal can be improved by the appropriate moisture content. It was found that the total CO generation rate, smoke release rate and the ignition time are effectively reduced, after setting the moisture content of 6.59–10.36% of the coal. As a result, both the combustion efficiency and heat release rate are improved.