Coke and Chemistry最新文献

A method is developed for automated identification of groups of macerals (vitrinite, inertinite, liptinite, and semivitrinite) and mineral inclusions from digital microphotographs of polished coal briquet surfaces. It is based on convolutional neural networks (CNN) and computer vision. For a test sample, the accuracy attained is 92.31%; that is comparable with the results of manual assessment. This method greatly increases the speed of coal assessment and reduces the subjectivity. The algorithm only works for preexisting images. The current study doesn’t address the creation of new images: the equipment required, sample preparation, and the specifics of microphotography.

Six samples of G (gas) coal differing in yield of volatiles, atomic ratio H/C, and vitrinite reflection coefficient R_{o, r} (0.68–0.75%) are studied by ¹³C NMR spectroscopic analysis. With increase in R_{o, r}, the aromatic content f_a of the organic mass in many samples increases from 0.65 to 0.71. This increase in f_a is proportional to the decrease in content of aliphatic carbon in structural fragments within the range 0–51 ppm. The plastic-layer thickness y is lowest for the sample with the highest f_a and lowest carbon content in aliphatic structural fragments of the coal’s organic mass.

The influence of volatiles in Tuva coal (of ranks GZh and Zh) on its temperature characteristics in combustion is investigated by synchronous thermal analysis (thermogravimetric analysis and differential scanning calorimetry) and infrared (IR) spectroscopy. The yield of volatiles is greater for Kaa-Khem FZh coal (47.5%) than for Mezhegey Zh coal (36.4%), on account of differences in their coalification and elemental composition. Pyrolysis at 600–900°C leads to the formation of more thermostable carbon materials with a lower yield of volatiles (<10%). Thermogravimetric analysis reveals inverse proportionality of the yield of volatiles and the ignition temperature. The reactivity is greatest for samples obtained at 600°C (ignition temperature up to 480–500°C), whereas carbonizates obtained at 900°C have high thermal stability (ignition temperature up to 640°C). IR spectroscopy confirms the destruction of oxygen-bearing and aliphatic groups on pyrolysis, with the formation of condensed aromatic structures. The results of this research may be applied to equipment used to generate thermal energy and also employed in switching to alternative fuels.

The formation of nanostructured composites by the thermal decomposition of transition metal nitrates in pores of a carbon matrix obtained in the carbonization of sapropelic coal is investigated. The nitrates—Co(NO₃)₂, Ni(NO₃)₂, Mn(NO₃)₂, Cu(NO₃)₂, Fe(NO₃)₃, Cr(NO₃)₃, and AgNO₃—are introduced in the matrix by adsorption from 0.5 M aqueous solutions. Emission spectroscopy with inductively bound plasma shows that the concentration of the transition metals in the nanostructured composites is 2–6 wt %. It is established by X-ray spectral analysis that the thermal decomposition products of the transition metal nitrates in the pores of the matrix are X-ray amorphous, except for AgNO₃ and Cu(NO₃)₂, probably because the particles formed are small. Adsorption porosimetry indicates that the specific surface and pore volume of the carbon matrix are slightly reduced when introducing the filler by this means. According to derivatographic data, carbon matrices containing the precursor of the filler are less resistant to thermal oxidation in air, probably on account of catalysis by the transition metal oxide nanoparticles that form. The electrochemical properties of the resulting nanostructured composites for electrode production are investigated by cyclic voltammetry. The results show that, in some cases, the introduction of filler by the thermal decomposition of transition metal nitrates yields composites whose unit electrical capacitance exceeds that of the initial matrix. The growth in unit electrical capacitance is greatest (20–25%) for nanostructured composites filled with the decomposition products of magnesium (II) and copper (II) nitrates.

The best available technologies for coke production in Russia and elsewhere are briefly analyzed and the most promising is selected, with a view to producing coke with high coke strength after reaction CSR from batch containing low-value coal. For the example of Severstal coke plant, it is shown that stamp charging of the coal batch increases the hot strength of coke by a factor of 1.14 relative to traditional gravitational charging and permits the use of up to 60% of low-value coal in the batch to produce coke with CSR no lower than 50%.

Analysis of the equilibrium naphthalene concentrations over coal tar, its absorbent fraction, and petroleum-based absorbent oil shows that thorough removal of naphthalene from coke oven gas requires an absorbent—whether petroleum- or coal-based absorbent oils—with low initial naphthalene concentration and low absorption temperatures.

The dynamics of phenol absorption from aqueous solution on AG-3 activated carbon is studied. Breakthrough curves—showing the time dependence of the relative concentration—are determined experimentally for different thicknesses of the immobile carbon layer and flow rates of the phenolic water. The mathematical model proposed to describe these curves is an equation with a hyperbolic tangent. The sorptional equilibrium constant for phenol at activated carbon is found (K = 3.472 × 10^–4 m^–1). In modeling the dynamic adsorption of phenol, the range of the permissible hypothetical flow rate in the sorption system is determined: 2.9–10.8 m/h. The influence of this factor on the process is demonstrated.

The caking property is a prerequisite and essential condition for coal to form coke. Investigating the impact of different functional group structures in coking coal on its caking property would be help to optimize coal blended, while the functional group structures of coal samples was used to characterize through Fourier transform infrared spectroscopy (FT-IR). The changes in these structures were investigated on eight coking coals of varying degrees of metamorphism during high-temperature pyrolysis in this paper. The peak fitting of infrared spectra was used to derive the structural parameters of the functional groups in the coal. Multivariate linear regression was then employed to analyze the correlation between different functional group structures and caking property (G value). The results demonstrated that the infrared parameters aromatic hydrogen rate ((f_{{{text{ar}}}}^{{text{H}}})), aromatic carbon rate ((f_{{{text{ar}}}}^{{text{C}}})), aromaticity (AR), the degree of aromatic ring condensation (DOC), and the length of the aliphatic chain or the branching degree of aliphatic chains (F) increased, when the longer aliphatic chains would break down into more short aliphatic chains during pyrolysis. Multivariate linear regression analysis revealed that the caking property G value of coking coal could be primarily determined by the length of the aliphatic chain or the branching degree of aliphatic chains, with secondary factors being the content of hydrogen bonds and aliphatic content. A higher aliphatic side chains content, primarily short aliphatic chains, a high degree of branching, and a significant amount of hydrogen bonds would be beneficial for generating more plastic layer, thereby enhancing the coal’s caking property. Therefore, the established regression model indicated that when the relative content of aliphatic groups in coking coal was around 0.50–0.65, the degree of branching was around 2.0, and the relative content of hydrogen bonds was between 1.5–4.0, the coal caking property G value was between 65~80, which could guide coal blending and coking from the perspective of coal molecular functional group structure.

The prospects for the formation of Fe–Pt nanoparticles in the pore structure of highly porous carbonizate of sapropelic coal are analyzed. Specific thermally stimulated behavior is established, demonstrating the great potential of such carbonizate to address the oxidation of iron often observed in the synthesis and storage of Fe–Pt nanoparticles, which are promising for catalytic and magnetic applications. In the Fe–Pt/C system, spontaneous reduction processes are noted at 250–900°C in an inert atmosphere. The reduction is due to CO and H₂ formed by catalytic reactions involving the carbon matrix and a platinum-bearing metal phase.

In this study, an efficient, sustainable, and low-carbon slag-based rapid repair mortar (SBRRM) was developed to overcome the inherent limitations of slow hardening and insufficient early strength in conventional rapid repair materials. Response surface methodology (RSM) was employed to systematically optimize the composition, investigating the effects of varying cement substitution rates on setting time, mechanical performance, and bonding strength. Microstructural analyses were conducted using X-ray diffraction (XRD), scanning electron microscopy (SEM), and nitrogen adsorption-desorption (BET) techniques. The optimal composition identified through the model comprised a cement substitution rate of 24.82%, a water glass modulus of 1.5, an alkali equivalent of 8.1%, and a water-to-binder ratio of 0.54. Under these optimized conditions, the deviation between the predicted and experimental results was merely 3.82%, highlighting the model’s high predictive accuracy. After 28 days of curing, the optimized SBRRM exhibited significantly enhanced mechanical properties, achieving a compressive strength of 67.88 MPa and a bending bond strength of 4.9 MPa, corresponding to respective improvements of 16.5 and 54.84% compared to the pure slag system. Moderate incorporation of cement promoted the formation of calcium silicate hydrate (C–S–H) gels, refined the microstructure, reduced the number of large pores, and substantially improved the compactness and stability of the mortar. Additionally, nitrogen adsorption capacity decreased notably from 18.5326 to 14.1033 mmol/g, further confirming a denser and more cohesive microstructure. This study provides valuable theoretical insights into the design and practical application of eco-friendly rapid repair materials featuring high slag utilization and reduced cement content. The findings align closely with contemporary sustainable development goals, demonstrating significant potential for practical engineering applications and environmental benefits.