Characteristics Of Macerals Research Articles

Chemical bond dissociation insights into organic macerals pyrolysis of Qinghua bituminous coal: Vitrinite vs inertinite

Coal pyrolysis essentially involves the decomposition chemical reaction of organic matters in coal under the drive of thermal fields. This heavily depends on the directed dissociation of different types of chemical bonds in coal macrostructures. The mechanism of temperature field regulation of various chemical bond dissociation during coal pyrolysis has not been obtained. The quantitative and intuitive depiction of the chemical bond dissociation of macerals is lacking at the microscopic perspective. This work provides chemical bond dissociation insights into macerals pyrolysis based on a comprehensive study. The relationship between temperature range and various chemical bonds dissociation have been established. The pyrolysis kinetics characteristics of macerals are quantitatively described. The molecular structure evolution characteristics and different chemical bonds dissociation of macerals are directly visual depicted by molecular dynamics calculations. The work could guide the intensification of the orderly conversion regulation and the chemical energy cascade release in coal utilization.

Relationship between fluorescence characteristics of coal macerals and excitation time

The fluorescence characteristics of coal macerals can be used as one of the indexes to evaluate the properties of coking coal. In this work, a single-wavelength laser with a wavelength of 360 nm was used as the excitation source to excite the surface of particulate block under a polarizing microscope. Effect of excitation time on fluorescence characteristics of the macerals was studied. The relationship between spontaneous fluorescence intensity and the excitation time of each maceral of six kinds of coking coals show that the fluorescence characteristics of coal macerals are related to the type and metamorphism of coal. The excitation time has a certain effect on the fluorescence parameters of the macerals. By comparing the relative fluorescence intensity values under different excitation times, it is found that the mean relative fluorescence intensity within 15 s can be used as an optical parameter to characterize the structure and metamorphic grade of different macerals. The essence of this method is to express movement of electrons in outer layer of nucleus by macroscopic fluorescence spectrum and relative fluorescence intensity of the initial state value and simplify microscopic complexity into macroscopic and numerical form generally accepted.

Pore Structure and Adsorption Characteristics of Maceral Groups: Insights from Centrifugal Flotation Experiment of Coals.

Coal has various types of macerals, which have different pore structures and adsorption properties that change with coal's thermal metamorphism. In-depth study of the characteristics of different coal macerals, especially the pore structure and adsorption properties, can better predict the coal reservoir gas storage capacity and migration ability. In this study, the sub-samples enriched in a specific maceral group with different coal ranks and particle sizes were obtained by centrifugal flotation experiments. Then, experiments containing low-temperature N2 isotherm adsorption (LT-N2GA), low-temperature CO2 isotherm adsorption (LT-CO2GA), and methane isothermal adsorption were carried out on the sub-samples to quantitatively analyze the evolution characteristics of pore structure and adsorption properties of different maceral groups. The results showed the following: (1) The separation effect of the light maceral groups by centrifugal flotation experiments increased with the decrease of particle sizes, which were treated with the heavy liquid of low and medium densities, while that of the heavy maceral groups had the relatively best separation effect in the particle sizes of 0.1-0.125 mm, which were treated with the heavy liquid of high densities. (2) The vitrinite-enriched samples had more ultra-micropores (mainly within the diameter range of 0.4-0.65 nm), while the inertinite enriched samples had more mesopores and transition pores (mainly within the diameter range of 40-50 nm). (3) For the low-rank coal, inertinite had more potential methane adsorption capacity. However, for the medium- and high-rank coal, vitrinite had more potential methane adsorption capacity. (4) For the low-rank coal, the adsorption potential and adsorption space increased with the increase of the inertinite content, while the adsorption potential, adsorption space, and surface free energy for the medium- and high-rank coal increased with the increase of vitrinite content. It is expected that the results can deepen the understanding about the gas storage capacity and migration ability and be used in the prevention of gas outburst and the reduction of carbon emission.

Petrographical and geochemical investigation on maturation and primary migration in intact source rock micro-plugs: Insight from hydrous pyrolysis on Woodford Shale

This study proposes a new approach to investigate primary migration in petroleum source rocks under laboratory conditions. It was conducted on organic carbon-rich, type II kerogen-bearing Upper Devonian-Lower Mississippian Woodford Shale. Hydrous pyrolysis was performed on polished source rock micro-plugs at different temperatures. Maceral characteristics are observed before and after the different pyrolysis experiments. Applying this new approach, in situ maceral changes at different maturities are directly visualized at the exact same place after artificial maturation at 300 °C, 320 °C, 330 °C, and 340 °C for 24 h. After each heating step, the surface was cleaned with dichloromethane. The bitumen adsorbed to some of the Tasmanites surfaces leads to the brighter fluorescence color after chemical extraction. Leiosphaeridia alginites are less stable than Tasmanites; they first expand and then shrink during thermal evolution partly leaving empty holes in the matrix. Tasmanites keep a strong yellow fluorescence and start to bituminize at the edge of the particles. Liptodetrinite shows significantly decreasing fluorescence intensities already at low pyrolysis temperature (320 °C) and disappears to a great extent at 330 and 340 °C.

Study on maceral characteristics and separation of low-rank coal

ABSTRACT This paper studies the characteristics of Shenhua low-rank coal, including industrial analysis, element analysis, density composition, particle-size composition, maceral characteristics and enhanced gravity. The separation characteristics of Shenhua low-rank coal maceral were examined by manual enrichment, screening enrichment and centrifugal heavy-liquid separation. After manual enrichment, vitrinite content was 31.06% higher than vitrinite content in raw coal, and inertinite content was increased by 13.50% compared with raw coal. The screening results show that vitrinite is easily broken into small pieces to be enriched in coarser particle size (0.125–0.074 mm), and inertinite is easily enriched in fine particle size (−0.045 mm); Centrifugal heavy-liquid separation showed that product in range of −1.30 g/cm3 was taken as pure vitrinite and product in range of 1.36–1.40 g/cm3 was regarded as purer inertinite. Finally, using rod mill products as feed material of enhanced gravity separation to study effect of feed speed, rotation frequency and recoil water on vitrinite recovery, vitrinite recovery of 71.81% and vitrinite content of 68.72% are obtained respectively under the optimal conditions of 30 Hz rotation frequency, 0.03 MPa recoil water pressure and 15 ml/s feed speed.

The characteristics of maceral in Huangling coal and its in-situ pyrolysis

In order to reveal the pyrolysis and coking characteristics of different components in coal, the macerals in Huangling coal were enriched by centrifugation, and the pyrolysis characteristics of macerals were studied. The transformation characteristics of macerals during pyrolysis were observed in-situ by heating stage microscope. The purities of vitrinite and inertinite are more than 90% and 80%, respectively, while the purity of liptinite is nearly 70%. The initial pyrolysis temperature of liptinite is about 385°C, and those of the other macerals are all about 410°C. The maximum pyrolysis temperatures are between 470–480°C for all macerals studied. The maximum weight loss rate and the total weight loss rate decrease in the order of liptinite, vitrinite, semi-vitrinite and inertinite. The softening temperature of the liptinite (including sapropelic groundmass) is 350–370°C, while that of vitrinite is about 410–420°C as shown by the in-situ pyrolysis in a heating stage microscope. The pyrolysis process of vitrinite goes through the stages of edge shrinking, pore formation, surface softening, the formation of liquid phase, and solidification. Only slight morphological changes are observed in semi-vitrinite, while no changes are observed in inertinite. The active components in Huangling coal are vitrinite and liptinite, and the liptinite can promote the softening and melting characteristics of the adjacent vitrinite.

Enrichment Characteristics of Macerals during Triboelectrostatic Separation in the View of Surface Microstructure, Pore distribution, and Typical Electrical Parameters.

Vitrinite and inertinite, respectively, are the reactive and inert macerals for coal liquefaction, which could be effectively enriched in triboelectrostatic separation specialized in particle processing. Inertinite has a higher specific surface area and more pores than vitrinite and a more balanced mesopores distribution, while the mesopores in vitrinite are mainly focused in the 4 nm × 7 nm range. As for electrical properties, inertinite has a higher relative dielectric constant than vitrinite in all granularities, while its resistivity is only higher than vitrinite in the <74 μm fraction, which means inertinite and vitrinite tend to have negative and positive charges, respectively, in their mutual friction, but inertinite (<74 μm) has a stronger ability to maintain surface charge. During triboelectrostatic separation, the 105 μm × 150 μm fraction of clean coal has the highest vitrinite content, whereas inertinite tends to concentrate at tailings <74 μm under the co-effect of separation granularity limit and electrical characteristics of macerals; this conclusion has a certain guiding significance to maceral separation.

Study on the Liberation of Organic Macerals in Coal by Liquid Nitrogen Quenching Pretreatment

In order to study the liberation characteristics of different macerals in coal, one must improve the liberation degree of macerals in coal and promote the utilization of macerals based on their properties. Based on the idea of quick cooling to change the brittleness and toughness of different macerals, the characteristics of macerals in coal are studied here by liquid nitrogen quenching pretreatment. In particular, coarse-grained samples (with a particle size of 1–3 mm) were. For this study, coal samples were sourced from the Yan’an Formation (J2y), a middle Jurassic coal formation in the Huangling no. 1 coal mine, located in northern Shaanxi Province, China. Firstly, we analyzed the coal properties and coal petrographic characteristics by the Chinese national standard method. Secondly, the distribution characteristics of macerals in different particle sizes (&gt;0.9, 0.5–0.9, 0.1–0.5, and &lt;0.1) were studied. Then, the samples with different particle sizes were quenched with or without liquid nitrogen to obtain the experimental group and blank group products. Finally, the differences in the liberation characteristics between the experimental group and the blank group products were studied via analyzing the micromorphology, specific surface area, pore volume, pore size and liberation degree. Our results for the particles size and liberation degree analysis indicate that inertinite and vitrinite were enriched in the coarse particles (&gt;0.5 mm) and fine particles (&lt;0.1 mm) here, respectively. Moreover, quenching pretreatment could contribute to the liberation of different macerals from coal, mainly because of the different effects of stress on the different components when they suddenly encounter cold, and this kind of liberation is mainly arc-shaped liberation between different macerals. In addition, along with the above results, this paper presents an optimized model for the liberation of macerals based on a combination of screening, liquid nitrogen quenching pretreatment and re-crushing.

Research on the maceral characteristics of Shenhua coal and efficient and directional direct coal liquefaction technology

AbstractIn this research, molecular structure models were developed respectively for Shenhua coal vitrinite concentrates (SDV) and inertinite concentrates (SDI), on the basis of information on constitutional unit of Shenhau coal and elemental analysis results obtained from 13C-NMR analysis characterization, FTIR analysis characterization, X-ray diffraction XRD and XPS analysis characterization. It can be observed from characterization data and molecular structure models that the structure of SDV and SDI is dominated by aromatic hydrocarbon, with aromaticity of SDI higher than that of SDV; SDV mainly consists of small molecule basic structure unit, while SDI is largely made from macromolecular structure unit. Based on bond-level parameters of the molecular model, the research found through the autoclave experiment that vitrinite liquefaction process goes under thermodynamics control and inertinite liquefaction process under dynamics control. The research developed an efficient directional direct coal liquefaction technology based on the maceral characteristics of Shenhua coal, which can effectively improve oil yield and lower gas yield.

Maceral Characteristics and Vitrinite Reflectance Variation of The High Rank Coals, South Walker Creek, Bowen Basin, Australia

DOI: 10.17014/ijog.v8i2.156The Permian coals of the South Walker Creek area, with a vitrinite reflectance (Rvmax) of 1.7 to 1.95% (low-volatile bituminous to semi-anthracite), are one of the highest rank coals currently mined in the Bowen Basin for the pulverized coal injection (PCI) market. Studies of petrology of this coal seam have identified that the maceral composition of the coals are dominated by inertinite with lesser vitrinite, and only minor amounts of liptinite. Clay minerals, quartz, and carbonates can be seen under the optical microscope. The mineral matter occurs in association with vitrinite and inertinite macerals as syngenetic and epigenetic mineral phases. The irregular pattern of the vitrinite reflectance profile from the top to the bottom of the seam may represent a response in the organic matter to an uneven heat distribution from such hydrothermal influence. Examination of the maceral and vitrinite reflectance characteristics suggest that the mineralogical variation within the coal seam at South Walker Creek may have been controlled by various geological processes, including sediment input into the peat swamp during deposition, mineralogical changes associated with the rank advance process or metamorphism, and/or hydrothermal effects due to post depositional fluid migration through the coal seam.

Maceral Characteristics and Vitrinite Reflectance Variation of The High Rank Coals, South Walker Creek, Bowen Basin, Australia

Maceral Characteristics and Vitrinite Reflectance Variation of The High Rank Coals, South Walker Creek, Bowen Basin, Australia

Relations between the reflection coefficients of the basic groups of macerals: A review

Quantitative relations are found between the structural and chemical characteristics of macerals of the basic coal groups (vitrinite Vt, inertinite I, liptinite L), on the one hand, and their reflection coefficients Rr and the corresponding dispersions σR, on the other. For coal of a particular metamorphic stage, the reflection coefficient declines in the series I > Vt > L, on account of the reduction in aromatic chemical structure and in the degree of condensation of the aromatic blocks. In the metamorphic series, the reflection coefficients of the macerals rise; the values for Vt and L at intermediate stages converge. The dispersion of the reflection coefficients (and hence the reflectograms) is due to the spread in characteristics of the chemical structure of the coal’s organic content, as confirmed by calculations for the vitrinite of D, G, Zh, and K coal.

The Synergistic Effect Between Coal Macerals During Hydropyrolysis

Using TGA technology, the volatile matter yields during hydropyrolysis of Chinese Shenmu coal and its derived high purity macerals under different heating rates and pressures were investigated. The Δ W, calculated by the difference between the volatile matter yield of parent coal and that of macerals, is used to evaluate the synergistic effect of macerals during hydropyrolysis. The results showed that with increasing pressure and decreasing heating rate, the Δ W increases. At temperature of 500°C and pressure of 3 MPa, the difference of volatile matter yield between parent coal and vitrinite reaches the maximum and the Δ W also occurs the highest value of 14.1%, suggesting the existence of the synergistic effect between macerals during hydropyrolysis. Based on the structural characteristics of macerals and the basic knowledge of hydropyrolysis, the possible explanation for the synergism are proposed.

Thermogravimetric-Mass Spectrometric Study of the Pyrolysis Behavior of Shenmu Macerals Under Hydrogen and Argon

The pyrolysis characteristics of macerals separated from Chinese Shenmu coal were systematically investigated using TG-151 pressurized thermobalance coupling with mass spectrometer under 0.1 MPa of Ar and H2, heating rate of 10°C/min and final temperature of 900°C. The TG/DTG results showed that vitrinite always had a higher volatile matter yield, larger maximum rate of weight loss, lower temperature of the maximum rate of weight loss than inertinite. Inertinite showed high response to the external hydrogen, especially at a higher temperature. The gases evolved during thermogravimetric analysis of macerals were analyzed on-line by mass spectrometer for the relative intensity of H2O, C1–C4, and C6H6. An obvious difference in evolution curves could be observed. The content of all gases evolved from vitrinite was higher than those from inertinite in both atmospheres. The amount of H2O and light hydrocarbons was higher in H2 than that in Ar, indicating the hydrogenation of oxygen-containing functional groups and free radicals formed during pyrolysis. The evolution curves of H2O and CH4 had different peak distributions and evolution temperatures under H2 and Ar, suggesting the different reaction mechanism during pyrolysis in different atmosphere. The evolution curves also revealed the different structural characteristics among vitrinite, inertinite and the parent coal.

The variation of structural characteristics of macerals during pyrolysis ☆

Vitrinite and inertinite were separated by DGC from Chinese Shenmu bituminous coal and the structural characteristics of the macerals, before and after pyrolysis, were analyzed by ultimate analysis, FTIR and 13C NMR. The results showed that vitrinite chars always had higher H and lower C content than inertinite char at the same pyrolysis temperature. The FTIR and 13C NMR indicated that vitrinite had more aliphatic C–H, hydrogen bonding and lower aromaticity. With increasing temperature, the aliphatic C–H decreased, aromatic C–H, aromaticity and H ar/H al ratio increased. At the same temperature, inertinite always had higher H ar/H al ratio than vitrinite, which is consistent with that inertinite had higher aromaticity than vitrinite. And the H ar/H al ratio was also related to the remainder volatile matter. With increasing H ar/H al ratio, the remainder volatile matter in vitrinite and inertinite decreased. The higher aromaticity and H ar/H al ratio and lower H content of the inertinite in all temperature range were correlated with its higher thermal stability and lower volatile yield than vitrinite.

蛍光ビジュアルケロジェン法によるマセラルの蛍光特性

蛍光ビジュアルケロジェン法によるマセラルの蛍光特性

97/00062 Ultramicro characteristics of macerals of hydrocarbon source rocks in Tarim Basin

97/00062 Ultramicro characteristics of macerals of hydrocarbon source rocks in Tarim Basin

96/05271 Maceral characteristics of pulverized coal for power generation boilers

96/05271 Maceral characteristics of pulverized coal for power generation boilers

Coal structure characterization and analysis by digital texture processing

Coal is a non-homogeneous substance; it consists of different constituents called macerals, each one characterized by its own set of properties. Macerals differ from mineral constituents of rocks because they do not have a well defined chemical composition. The purpose of this paper is to describe the use of digital processing techniques based on the analyses of sample images to characterize coals taking into account the reflectance-textural characteristics of macerals. These characteristics were recognized, analysed and modelled. A pattern vector characteristic of each maceral was thus identified. The procedure is based on the processing of data (digital images) acquired by means of reflected light optical microscopy. Polished specimens of coal ores are considered for the study. In such a way it is pointed out a suitable procedure for a quantitative characterization of the different macerals constituting the coal.

Pyrolysis characteristics of macerals separated from a single coal and their artificial mixture

Sufficient quantities of the three major maceral groups (vitrinites, fusinites and liptinites) were separated from a single coal, Pingshuo bituminous coal. Nine model coals were prepared by mixing the individual macerals in different amounts. The behaviour and kinetics of these 12 samples during nitrogen pyrolysis have been investigated and the pyrolysis mechanism has been analysed in conjunction with the information obtained by Fourier transform infrared spectrometry and X-ray diffraction. The data presented indicate that there are three stages in the overall devolatilization process, and each stage is a first-order reaction. The pyrolysis conversion of the maceral mixtures (model coals) is equal to a calculated sum of the individual macerals, and the activation energy in each stage equals the sum of the activation energies of the individual macerals.