Solid Fuel Chemistry最新文献

With the depletion of shallow coal seam resources, deep mining has become a trend, and deep stress makes coal mining in the process of repeated cyclic loading and unloading. In order to study the energy evolution law of mechanical properties of coal and rock under the action of cyclic gradient loading, the RTX-1000 high temperature and high pressure dynamic rock triaxial loading experiment is carried out on coal samples. The changes of residual strain, elastic modulus, input energy density and dissipated energy density of coal and rock under different cyclic gradient loading are compared and analyzed. The results show that with the increase of confining pressure, the number of cyclic gradients of coal and rock samples increases, and the peak strength increases, which are 16.04, 32.04, and 43.92 MPa, respectively, and the axial, radial and volumetric strains have obvious memorability. In the cyclic gradient loading, the residual variable of the coal sample under the same confining pressure decreases sharply and then slowly, and the graph is concave with the number of cycles. Under the same confining pressure and the cyclic loading gradient, the loading elastic modulus is always higher than the unloading elastic modulus, and the elastic mod-ulus of the coal sample gradually decreases under the same cyclic gradient. In the process of cyclic gradient loading, most of the input energy density is stored in the rock sample in the form of elastic strain energy, and the dissipated energy increases between 0.05 and 0.29% of the total input energy in a single cycle, which provides theoretical guidance for deep coal seam mining and roadway support.

Highlights

• The variation law of residual strain and elastic modulus of coal samples under cyclic gradient loading were investigated.

• The stress peaks of coal samples under different confining pressures were 16.04, 32.04, and 43.92 MPa at 5, 8, and 12 MPa, respectively.

• The calculation formulas of input energy density, elastic energy density, plastic energy density and dissipated energy density of coal samples were presented.

• The energy of each part of coal sample under the last cycle gradient was studied with the increase of cycle times, which provides theoretical guidance for deep coal mining and roadway support in reality.

The effects of Mg²⁺ on the combustion behavior of Loy Yang lignite (LY) were studied. The combustion behaviors of all samples were investigated using a thermogravimetric (TG) analyzer. Moreover, all samples were characterized using Fourier transform infrared (FT-IR) spectrometer with a DRIFT model, scanning electron microscope (SEM), and a specific surface area and porosity analyzer. The results showed that Mg²⁺ was successfully loaded into the acid-washed sample (LYA) in the form of carboxylates. The addition of Mg²⁺ blocked partial pores of LYA. Compared with that of LYA, the peak temperatures of the Mg²⁺ loaded samples (LYA_Mg0.05 and LYA_Mg0.1) decreased by 2.0 and 2.4%, respectively. The activation energies of LYA_Mg0.1 and LYA_Mg0.05 were lower than that of LYA. Overall, Mg²⁺ could catalyze the combustion of lignite. The higher the loading content, the more obvious the catalytic effect is. Additionally, we proposed a mechanism of Mg²⁺ catalyzing the combustion of lignite, i.e., Mg²⁺ acts as an oxygen carrier, which could enhance the transport of oxygen. Consequently, a catalytic effect of Mg²⁺ on lignite burning was observed.

In order to explore the effect of calcination temperature on the microstructure and physicochemical properties of medium and low sulfur petroleum coke, two types of petroleum coke with different sulfur contents were calcined at 600–1400°C. The sulfur content, true density, powder resistivity, Lc value, microstructure and microstructure evolution process of calcined coke were analyzed by DTA-TG-DTG, FT-IR, Raman, polarizing microscope (PLM), FE SEM and other methods. It was found that there is not much difference in the DTA-TG-DTG curves between medium sulfur petroleum coke and low sulfur petroleum coke, and the microstructure evolution process is basically consistent. As the calcination temperature increases, there are significant differences in the growth process and basic properties of carbon crystals in calcined coke, which are closely related to the presence and transformation of sulfur. This study can provide important parameters for the pre-calcined anode desulfurization process in the production of aluminum using medium and low sulfur coke.

The roof-cutting and pressure-release (RCPR) mining mode can eliminate coal pillar between the adjacent mining faces by automatically forming roadways, which shows the better mining efficiency and economy than the traditional longwall mining mode. However, this mining mode causes changes in the collapse characteristics of the overlying rock and air leakage in a coal mine goaf, which may influence spontaneous combustion of coal in a coal mine goaf. To study the distribution of the spontaneous coal combustion zone in the coal mine goaf under the RCPR mining mode, the distributions of oxygen concentration and temperature in a coal mine goaf are simulated and analyzed after the simulation verification to reveal the new characteristics of the spontaneous coal combustion zone. The research results show that (1) the spontaneous coal oxidation zone is in the type of letter C, different from the one under the traditional longwall mining mode; (2) the air leakage pathway in the type of letter S causes the unique spontaneous coal oxidation zone, which is different from the air leakage pathway in the type of right parenthesis under the traditional longwall mining mode; (3) a temperature index to divide the spontaneous coal combustion zone is determined by the comparison between the temperature distribution and oxygen concentration distribution.

Mine counter wind is an important relief measure to control airflow when disaster occurs in mine. Once a fire occurs in the main inlet area of the mine, in order to prevent the expansion of the disaster, it is necessary to carry out mine counter wind.Windy well gas ventilation system during mine air reverse distribution of gas migration is more complex, rely on experimental method is difficult to clearly grasp the mineral sheers distribution of gas migration during the wind, combined with the practice, rarely used against the wind, the lack of mineral sheers anti wind during gas migration distribution in ventilation system, resulting in many cases, difficult to make a decision on against the wind, Therefore, it is necessary to use the computer simulation program to simulate and study the reverse wind in the high gas mine with multiple air shafts. And gas migration in mine is one of the most important parameters in simulation of dispersion dispersion coefficient of gas migration, is for the study of reverse wind during the migration of gas in mine network system diffusion process, the formation of high concentration of gas cloud caused by catastrophe rule research and plan technical analysis, gas migration characteristics of dispersion experiments.

The possibility of reusing mesoporous Sibunit as an adsorbent for 2,4-dichlorophenoxyacetic acid was studied. The effectiveness of using microwave radiation to restore the adsorption properties of the studied adsorbent was shown. A decrease in the average pore size on the surface of the Sibunit sample was noted as the adsorption–regeneration cycles were carried out without reducing the value of the adsorption capacity.

In order to study the tensile properties and crack evolution of bedding coal under splitting load, Brazilian splitting tests were conducted on bedding coal. Results indicate distinct anisotropic mechanical properties of bedding coal. When the bedding dip angle is 0°, the coal sample exhibits the highest tensile strength and splitting modulus, followed by 30° and 90°, with the lowest values observed at 60°. Under the Brazilian splitting load, the crack propagation mechanism for coal samples with a bedding dip angle of 0° involves a combined tension-shear fracture. For dip angles of 0° and 60°, the crack propagation mechanism gradually shifts from tension-shear to tension failure, while at 90°, the crack propagation mechanism is primarily along the bedding plane in tension. The tensile failure characteristics of coal samples with bedding dip angles of 60° and 90° are more pronounced, and the load- acoustic emission parameter curve shows distinct bedding features. In the case of a 30° bedding dip angle, the failure is mainly due to a combined shear and tension cracking, with the acoustic emission counts exhibiting a multi-stage growth pattern. Furthermore, this study explores the implications of bedding coal fracture morphology for fracturing.

The results of a study on the pyrolysis of agricultural (coffee husks and parchment) and agroindustrial (two types of spent coffee grounds) waste from coffee production are presented. A study of the temperature dependence of the weight loss of samples during pyrolysis and the qualitative analysis of the main volatile substances were carried out using a thermogravimetric analyzer (TG) coupled with a Fourier transform infrared spectrometer (FTIR). The main stages of thermal decomposition of the samples were presented at four heating rates of 5, 10, 20, and 30 K/min. The results of an analysis of IR spectra for the volatile components of pyrolysis products of four materials were shown, and the temperature dependences of the absorption band intensities of the main gaseous pyrolysis compounds were plotted.

In this work, a study of chicken litter pyrolysis was carried out in a thermal analyzer in a temperature range from 20 to 905°C at different heating rates of the raw material. Four peaks were obtained in a graph of the temperature dependence of the rate of weight loss. The first and second peaks were associated with the decomposition of plant biomass components; the third peak was due to the decomposition of plant and manure components, and the fourth peak characterized the decomposition of compounds from the mineral part of chicken manure. Spectral analysis of the gaseous products of chicken litter pyrolysis showed that they contained flammable components typical of gaseous products of thermal decomposition of plant biomass. The temperature range of the most intense formation of main carbon-containing compounds was 140–380°C. In addition, nitrogen-containing compounds associated with the decomposition of urea and proteins from chicken manure were found in the volatile components.