The utility of coal molecular models
Introduction. Molecular models of coal have progressively populated the literature over the last 70 years. While they number in excess of 125 models, the initial purpose of many of these models was to aid the comprehension of coal. Models have developed over the years to capture variations in rank and maceral composition, but …
Variation of the coal chemical structure and
Rapid pyrolysis (∼10 4 K/s) experiments investigating lignite, bituminous coal and anthracite were conducted to study the effect of the thermal process on the coal structure. The interest was focused on the chemical structure variation occurring at the early stage of pyrolysis (0–500 ms) and high temperature (1173–1773 K), which includes the …
Understanding the molecular structure of Datong coal by …
The final 2D molecular model of Datong coal is shown in Fig. 5, with the molecular formula of C 149 H 112 O 24 N 2 and molecular weight of 2314.53. The comparison between the calculated and experimental 13 C-NMR spectra of molecular model is shown in Fig. 6 (a).
Coal
Coal - Carbon, Organic Matter, Sedimentary Rock: The plant material from which coal is derived is composed of a complex mixture of organic compounds, including cellulose, …
Prediction and Characterization of the Microcrystal Structures of Coal …
The characterization of coal structures is challenging due to their broad distribution of molecular structures including large-scale entities. Previously, the microcrystal structure of coal has been extensively observed with the XRD analysis and its features were found to be closely correlated with the carbon/oxygen content. In this work, …
Molecular Structure of Coal
Coal is a sedimentary rock that is composed principally of two basic classes of materials: inorganic crystalline minerals and organic carbonaceous macerals. The …
Effect of acid concentration on organic structure and small molecule …
This side reflects that the high concentration of sulfuric acid is more destructive to the molecular structure of coal. Download : Download high-res image (442KB) Download : Download full-size image; Fig. 5. Form and content of C obtained from C 1 s XPS spectra. (a) C C or C H, (b) C O, (c) C O, (d) COO. (Note: Red bar is the …
Structural Model Construction and Optimal Characterization …
The structural characteristics of coal at the molecular level are important for its efficient use. Bituminous coal from the Baozigou Coal Mine is investigated, using elemental analysis, 13C nuclear magnetic resonance, X-ray photoelectron spectroscopy, and Fourier transform infrared. The molecular structure was determined. The aromatic compounds …
Molecular Model Construction of Low-Quality Coal and Molecular
Molecular simulations, which can explain macroscopic phenomena from a microscopic molecular perspective, are currently receiving considerable attention. The key to this is how to characterize molecular structural parameters and construct realistic numerical models of molecules. In this paper, 13C NMR tests were performed on ten …
Molecular model and ReaxFF molecular dynamics simulation of coal
Vitrinite in coal, the mainly generating methane maceral, plays an important role in hydrocarbon generation of coal. This study aims at obtaining products formation mechanism of vitrinite pyrolysis, and hence determining the chemical bond, molecular liquefaction activity, and reactions mechanism of methane and C2–4 during pyrolysis. …
Mechanism of the pore and molecular structure evolution of coal …
Fig. 2 depicts the 3-D CT models of coals under the different AMD environments. According to W. Liu et al. (2023), the 3D digital core reconstruction is linked to the spatial distribution of pores, minerals, and matrix.However, P. Liu et al. (2023) indicated that the small model size change is more sensitive to heterogeneity, while the …
The molecular representations of coal – A review
The first liptinite-rich (Barzas) coal molecular representation was generated by Patrakov et al. [68], this structure was large (10,260 amu) consisting of copious quantities of condensed-linked (but not cross-linked) hydroaromatic rings (Fig. 1 h). Vu et al. [69] developed a 3D model of a low-rank coalified wood (Australian). This model also ...
Understanding the chemistry and physics of coal …
Abstract. This article outlines our current understanding of the structure of coal in terms of both the chemical and physical bonding processes responsible for its structural integrity …
Characterization and Analysis of Molecular-Scale …
To explore the micropore structure of coal, this paper proposes a method to reconstruct coal pores at the molecular scale, characterizing and analyzing the micropore structure of coal with different metamorphic …
15.6: Coal
Figure 15.6.3 illustrates the global carbon cycle, the distribution and flow of carbon on Earth. Normally, the fate of atmospheric CO 2 is to either (1) dissolve in the …
Coal
Geologists believe that underground coal deposits formed about 250–300 million years ago, when much of Earth was swamp covered with thick forest and plant growth. As the plants and trees died, they sank under Earth's wet surface, where insufficient oxygen slowed their decay and … See more
Structural characterization analysis and …
the coal molecular structure, and the former two chemicals play a dominating role. According to the analysis results, the molecular formula of the QGP coal is ¤nally …
Coal
Coal is one of the world's most abundant sources of energy. percent fixed-carbon content and a heating value of 8,300–13,000 Btu/lb (8.8–13.7 million joules/lb). The fourth class, lignite, a soft brownish-black coal, also has a 46–60 percent fixed-carbon content, but the lowest heating value, 5,500–8,300 Btu/lb (5.8–8.8 million joules ...
Construction of molecular structure model of Tunlan coal …
Download : Download full-size image; Fig. 7. 2D molecular structure models of raw coal and residues. ... This indicates that a compact coal molecular structure has a good stereoscopic structure after optimization, and due to π-π interactions between aromatic rings, the aromatic layers show a nearly parallel arrangement. ...
Pore Structure Characterization Based on the Panxi Coal Molecular …
Reconstructing the pores of coal from a molecular perspective was realized, providing a methodological basis for the study of the microscopic properties of Panxi coal. The molecular model of the Panxi coal was established by ultimate analysis, solid-state CP/MAS 13 C nuclear magnetic resonance, and X-ray photoelectron …
Effect of surfactant on the attachment between coal particles …
The molecular structure of Daliuta coal shown in Fig. 4 (a) was built by our research team [30], [31]. The molecular weight and elemental composition of Daliuta coal are shown in the Table 2. The density of subsequent coal molecule aggregation model is 1.3 g/cm 3. Download : Download high-res image (518KB) Download : Download full …
The Molecular Model of Organic Matter in Coal-Measure …
The results show that whether the OM pores varied from 20 to 350 nm as obtained from FIB-SEM images or less than 10 nm as observed in the TEM images, both were of poor connectivity. ... Zeng F., Wang X. Construction and Evaluation of a Medium-Rank Coal Molecular Model Using a Hybrid Experi-mental–Simulation–Theoretical …
Changes of Coal Molecular and Pore Structure under …
In view of the limitation of the conventional coal seam fracturing method, an ultrasonic stimulation method was proposed. Utilizing the combined effects of ultrasonic cavitation, mechanical vibration, and thermal conditions, the coal will form a network of intertwined cracks, and the gas will desorb and flow more easily. Current research on the changes …
Molecular structure characterization analysis and molecular …
Coal is the largest non-renewable energy as well as an important basic energy and industrial raw material. Thus, correctly understanding the molecular structure characteristics of coal has important theoretical value for realizing carbon neutralization. In this work, we clarified the molecular structure characteristics of anthracite, where the …
Study on the evolution characteristics of molecular surface …
For the entire coal molecule, the distributions of the positive and negative electrostatic potentials were non-uniform. Fig. 11 (c) shows the average values of the positive and negative electrostatic potentials on the coal molecule surface, providing a partial characterisation of the average adsorption capacity of the coal molecule. As depicted ...
Structural characterization analysis and …
The coal molecular is mainly of aromatic carbon structure, where the ratio of bridge aromatic carbon to peripheral carbon is 0.198. ... The images or other third party …
Dynamic Simulation Based on a Simplified Model of 1/3 Coking Coal
The raw coal samples and coal samples immersed in water after drying, 2–3 mm coal particles are directly screened out, and the microstructure and morphology characteristics of raw coal and soaked coal are observed at 800 and 1600 times to understand the change in the internal structure of the two coal samples. Through image processing, the ...
Insight on adsorption mechanism of coal molecules at different ranks
The real coal molecular models at different ranks were constructed by relevant experiments. ... Download : Download full-size image; Fig. 15. Free methane molecule. The lowest adsorption energy forms of the aromatic structure in MTG, PX, DSC, and TL coal molecules are 4-Up-T, 5-Up-T, 7-Up-T, and 5-Up-T respectively. ...
The interactions between fine particles of coal and …
The Mulliken atomic partial charges of bituminous coal molecule (the molecular model of bituminous coal [40], [41] as shown in Fig. 4) were distributed after the geometry optimization at the PW91/DNP level in the Dmol 3 module. Download : Download high-res image (621KB) Download : Download full-size image; Fig. 4.
Theoretical understanding of coal char oxidation and …
Since the 1970 s, there are over 140 proposed molecular level representations or models of coal and coal char which are used to investigate the atomistic mechanism of the processes of oxidation, gasification and etc. [28]. At present, the molecular structure model of coal char is mainly constructed by the following ways as …