Coal Carbon Research Articles

Effects of Different Biological Carriers in Microbial Fuel Cells.

In this study, to investigate their effects on battery power generation performance and wastewater treatment capacity, coal semicoke granular-activated carbon, granular graphite, and walnut shell-activated carbon were added to the anode compartment of a microbial fuel cell. As revealed from the experimental results, adding activated carbon and graphite can significantly decrease the startup time of microbial fuel cells as well as provide the shortest startup time of coal semicoke-activated carbon fluidized bed microbial fuel cells (MGAC-MFCs). The activated carbon particle diameter did not increase from 0.275 to 0.55 mm, and the voltage changed the chemical oxygen demand (COD) degradation efficiency. However, the 0.275 mm activated carbon exhibited a maximum open-circuit voltage of 935 mV as well as a COD degradation efficiency of 95%, and the operation cycle was shortened. After running a cycle, the COD removals of different systems were 85, 93, and 89%, and the maximum value was obtained by the MGAC-MFC system. After the activated carbon and graphite particles were added, the electrical performance and production capacity of the sewage treatment microbial fuel cells were significantly enhanced.

Stable isotopes of organic carbon, palynology, and petrography of a thick low-rank Miocene coal within the Mile Basin, Yunnan Province, China: implications for palaeoclimate and sedimentary conditions

Coal contains detailed long-term records of contemporaneous environment, climate, and subsequent diagenetic processes. Stable isotopes of carbon, petrological, palynological, and mineralogical analyses were carried out on a 28 m thick low-rank Miocene coal seam from the Mile Basin, Yunnan Province, China for the purpose of deciphering the palaeoclimate and sedimentary conditions during peat deposition. The coal is characterized by both pale and dark lithotypes. Palynological analyses show that both lithotypes are dominated by angiosperms, which is interpreted to indicate a moderately warm climate. The absence of Fagus and Taxodiaceae pollen suggests that there may have been dry periods during peat accumulation; in general, both Fagus and Taxodiaceae require a constant wet environment in order to proliferate. Organic petrography, δ13C, and gypsum concentrations corroborate that there were alternating drier and wetter periods within the palaeomire during peat accumulation. The fine-scale variability in the δ13C signature appears to be controlled by plant type. Angiosperm/gymnosperm ratios and Vegetation Index are directly correlated with δ13C isotopic values. Plant type, however, seems to be proximally controlled by water level. Angiosperms were more dominant during times of lower water table or less moist conditions, interpreted to correspond to less negative values of δ13C. The correlation of greater concentrations of gypsum with less negative δ13C values also supports drier conditions. However, in addition to the fine-scale variability, four larger scale cycles are defined based on less negative δ13C values. A less negative δ13C isotopic signature demarcates the top of each of these cycles, which represent spikes of lower water table and/or drier conditions. In addition, a general correlation of the δ13C variations in the studied coal seam with atmospheric CO2 suggests that the atmosphere also had a significant influence on peat formation in the Mile Basin. Although the Mile Basin palaeomire accumulated over a long time, an integrated approach to its analysis has demonstrated considerable variation in palaeoclimate. Changes in wetness/dryness had a direct effect on the ecological composition of the palaeomire. These floral changes would not have only been restricted to the palaeomire but most likely had a regional influence. Thus, detailed analysis of coals can yield useful, insightful and practical knowledge on past regional palaeoenvironmental conditions, which can then be placed within a global context.

Analysis of CO2 Abatement Cost of Solar Energy Integration in a Solar-Aided Coal-Fired Power Generation System in China

Utilization of renewable energy, improvement of power generation efficiency, and reduction of fossil fuel consumption are important strategies for the Chinese power industry in response to climate change and environment challenges. Solar thermal energy can be integrated into a conventional coal-fired power unit to build a solar-aided coal-fired power generation (SACPG) system. Because solar heat can be used more efficiently in a SACPG system, the solar-coal hybrid power system can reduce coal consumption and CO2 emissions. The performance and costs of a SACPG system are affected by the respective characteristics of its coal-fired system and solar thermal power system, their coupling effects, the solar energy resource, the costs of the solar power system, and other economic factors of coal price and carbon price. According to the characteristics of energy saving and CO2 emission reductions of a SACPG system, a general methodology of CO2 abatement cost for the hybrid system is proposed to assess the solar thermal energy integration reasonably and comprehensively. The critical factors for carbon abatement cost are also analyzed. Taking a SACPG system of 600 MW in Jinan, Shandong and in Hohhot, Inner Mongolia in China as an example, the methodology is further illustrated. The results show that the efficiency of solar heat-to-electricity should be high and it is 0.391 in the scheme of SIH1 in Hohhot, and that the designed direct normal irradiation (DNI) should be greater than 800 W/m2 in order to make full use of solar energy resources. It is indicated that the abatement cost of a SACPG system depends significantly both on the cost of solar power system and its relevant costs, and also on the fuel price or the carbon prices, and that the carbon abatement cost can be greatly reduced as the coal prices or CO2 price increase. The methodology of carbon abatement cost can provide support for the comprehensive assessment of a SACPG system for its design and optimal performance.

Experimental Investigation on Mixed Combustion Characteristics of Coal, Tobacco Straw, and Cinder in an Energy-Saving Bake Process

Abstract In view of high-energy consumption, high baking cost, and serious pollution emission during the baking process of tobacco leaves, thermogravimetric analysis is employed to investigate the combustion characteristics of coal, tobacco straw, and cinder. Analyzing thermogravimetric-derivative of thermogravimetric (TG-DTG) characteristics of samples with different blending ratios and based on the ignition temperature and burnout temperature, the combustion characteristics of the samples are obtained. Compared with the individual combustion of coal, the blending ratio of the optimal positive effect is obtained. It is illustrated that different blending ratios of coal, tobacco straw, and cinder result in different effects between promotion and inhibition. Tobacco straw is beneficial to burn on fire but adverse to keep combustion of fixed carbon. Compared with the TG and DTG characteristics in different blending ratios of coal, tobacco straw, and corresponding combustion characteristic parameter, it is illustrated that the best blending ratio of tobacco straw is 40%. According to the TG and DTG characteristics of different blending ratios of coal, cinder, and corresponding combustion characteristic parameter, it is shown that the more blending ratio of cinder, the more adverse effect to fixed carbon burning. The composite fuels with 40% tobacco straw, 10% coal cinder, and 50% coal have two obvious advantages. On the one hand, it can maintain quick burning and the volatile combustion of the tobacco straw at low-temperature stage. On the other hand, it can keep continuous combustion of the fixed carbon in coal at high-temperature stage.

Integrated assessment and obstacle factor diagnosis of China's scientific coal production capacity based on the PSR sustainability framework

The Scientific Coal Production Capacity (SCPC) is an important decision-making basis for the sustainable development of China's coal industry. It is important to objectively measure its evolution characteristics and identify its key impact factors. Based on the Pressure-State-Response (PSR) model and the connotation of SCPC, this paper constructs a comprehensive SCPC evaluation system from the dimensions of resources, technology, safety, environment and benefits. Furthermore, this paper proposes an integrated analysis method to evaluate and identify the evolutionary characteristics and key influencing factors of SCPC from 2000 to 2016. The results show that, a) China's SCPC assessment system reflects the current state of pressure drive, operational state and regulatory response of China's coal overcapacity and its interaction mechanism. b) The integrated assessment method of SCPC can effectively remedy the deviation caused by the method of constant power evaluation and improve the accuracy of the evaluation method and the reliability of the evaluation results. c) China's SCPC tends to improve overall during the period of 2000-2016, but its development is slow. The reason is that the operation state of SCPC and its response mechanism are improved, and the impact of the pressure-driven factors of SCPC still exists and has not be improved. d) The obstacle factors of the pressure-subsystem of SCPC mainly involve coal transportation and carbon mitigation constraints. The obstacle factors of the state-subsystem are mainly coal quality, employee health and asset operation ability, and the obstacle factors of the response-subsystem are market regulation and demand-side response mechanisms. The key to improving China's SCPC in the future is to strengthen the construction of coal transportation channels, achieve clean utilization of coal resources, pay attention to employee health, improve asset operation efficiency and promote coal market reform.

Effects of sequence stratigraphy on coal characteristics and CH4 adsorption capacity of the low-rank coal in Santanghu Basin, China

This paper focusses on sequence stratigraphy of coal-bearing strata, coal petrography, coal chemistry, and the CH4 adsorption capacity of the Badaowan Formation in Santanghu Basin, China. The comprehensive coal characteristics of 12 coal samples were determined, coupled with maceral composition, proximate analysis, elemental analysis, reflectance (Ro), and high-pressure CH4 adsorption. The results indicated that maceral composition and chemical properties of coal were controlled by the sequence stratigraphic framework. During the TST, the content of vitrinite, the ratio of vitrinite to inertinite (V/I) and the content of carbon in coal increased gradually from bottom to top. While during HST, an opposite trend was observed. Furthermore, due to the intrusion of the lake water, the ash yield in the TST is higher than that in HST. The CH4 adsorption capacity is positively correlated with the content of vitrinite and V/I. There is a moderate positive correlation between fixed carbon contents and VLad. Ash content was strongly correlated to Langmuir volume under the air-dry basis, with increasing Ad associated with the reduction of the VLad. It was observed that the CH4 adsorption capacity generally gradually increased during the TST, and gradually decreased in the HST. Gas content also shows a similar change rule. CH4 adsorption capacity is functionally dependent on coal characteristics, which again are dependent on sequence stratigraphy and thus the coal-forming environment. The base level and cycles of the sequence establish a theoretical and practical framework for CBM extraction from low-rank coal reservoirs.

A model for assessing the compound risk represented by spontaneous coal combustion and methane emission in a gob

In recent years, the spontaneous combustion of coal has led to numerous gas explosions in mines that have resulted in hundreds of fatalities and very substantial damage to facilities. The present work developed a fully coupled model capable of simulating spontaneous coal combustion and carbon monoxide (CO) release together with methane (CH4) desorption rates, concentration distributions and migration. The aim was to evaluate the combined hazard posed by spontaneous coal combustion and CH4 build-up in mine as a result of the heat release generated by coal oxidation. The results show that the zone representing the highest degree of compound hazard is in the shape of an inclined strip located between 75 and 115 m from the working face on the inlet airway side but closer to the working face on the return airway side. Increases in the CH4 concentration in the return corner decrease as the ventilation flux increases, while the potential danger zone moves deeper into the gob. A greater initial CH4 release rate from the coal increases the size of the danger zone and moves this zone closer to the working face. The danger zone also moves away from the working face with decreases in the residual coal thickness and in the coal oxidation rate. Multivariate functions were developed to predict the positions of the gas explosive zone and the oxidation zone in the gob, and a model for assessing the risk of the compound hazard was established based on evaluating the index gas concentrations in the return corner.

Analysis of the three-phase state in biological hydrogen production from coal

The production of biohydrogen from coal is a new research direction in the bioengineering of coalbed methane. In order to study the transformation process and mechanism of the gas-liquid-solid tripe phase in biohydrogen production from coal, a biohydrogen production experiment from low-rank coal is carried out under laboratory conditions. The results show that: The daily gas production of hydrogen reaches a peak value of 1.23 mL/g on the fifth day. The cumulative hydrogen production is 6.24 mL/g. The pH of the liquid products gradually decreases to 5, and the Eh gradually increased from −180 to −50 mV during the experiment. The peak value of lignin degradation rate is 0.42% on the 7th day. The chemical oxygen demand (COD) first increases and then decreases. The highest COD is 4068 mg/L, and the final COD degradation rate is 46.3%. The peak values of cellulase are 0.021 mg/(mL h) and 0.223 mmol H2/(min mg) at 3 d later than that of hydrogenase. The absorbance of bacterial turbidity first increases and then decreases, with the community structure proving that the hydrolytic bacteria are dominated by Acinetobacter, Comamonas, Intestinimonas, and some fermentation bacteria, including Macellibacteroides. The changes of carbon, oxygen, nitrogen, sulfur and functional groups of carbon and oxygen in coal are obvious, with aliphatic carbon (methoxy, carbonyl, and so on) representing the main part of the biochemical reaction in the macromolecular structure of coal. The analysis of the three-phase state in the process of coal hydrogen production is helpful to study the mechanism of hydrogen production by coal fermentation from different perspectives, and also provides a reference for the promotion of coal hydrogen production by fermentation in the next step.

Estimation of coal elemental composition from proximate analysis using machine learning techniques

ABSTRACT Knowing the properties of coal, which is still the most widely used among primary energy sources, is critical for determining the application area and the technology to be applied. The ultimate analysis results contain important information for the estimation of the gas product composition to be released to the environment as a result of the combustion process. This study aims to make a comparative study using different machine learning models, namely, Support Vector Regression (SVR), Regression Trees (RT), the Ensemble of Trees (ET), Gaussian Process Regression (GPR) for predicting the elemental composition of coal. The moisture, ash, volatile matter, and fixed carbon contents were used as input variables to predict carbon, hydrogen, and oxygen contents of coal. 70% of 6339 coal samples (4437 data) containing different quality coal types were for the training of the models, whereas the remaining 30% sets of data (1902 data) were used to evaluate the prediction performance of the developed models. Analysis results proved that the GPR-exponential model performs best among all models. In the training stage, the correlation of determination (R2), mean absolute percentage error (MAPE), root mean square error (RMSE) and mean absolute deviation (MAD) values were obtained as 0.9970, 0.7525%, 0.6492, 0.4635 for Carbon content; 0.9900, 0.5712%, 0.0646, 0.0297 for Hydrogen content; 0.9951, 4.0664%, 0.7910, 0.4152 for Oxygen content, respectively. Reported indices showed that the GPR-exponential model is a promising procedure for achieving high accuracy and can be used as a reliable model to predict the coal elemental components successfully.

Analysis of the Effect of a Magnetic Field Applied to a Process of Adsorption of Water Contaminants Using Adsorbents of Different Magnetic Orderings

Adsorption studies were carried out to determine the behavior of three carbonaceous adsorbents with different magnetic orderings (ferromagnetic, paramagnetic, and diamagnetic) and the effect of an external magnetic field on the adsorption of a cation (lead, Pb2+) and an anion (fluoride, F–). Two different static magnetic field intensities were used to analyze the sensitivity of the adsorption system as a function of the applied magnetic field, based on computational simulations, with the aim of determining the degree of magnetization of each system and the distribution of the flow density generated by each magnetic field application system. The results of the adsorption studies for the removal of Pb2+ showed a correlation between the adsorption capacities and the magnetic ordering of the adsorbent material. Particularly, the activated carbon of bituminous coal (ferromagnetic) showed an increase of 15%, whereas bone char (paramagnetic) showed an increase of 6%. On the other hand, this behavior was not observed in the studies for the removal of fluoride.

Ultrasonically assisted removal of toxic dye using Iranian bituminous coal based-activated carbon: synthesis, characterization, modeling, equilibrium and kinetic studies

Bituminous coal as an abundant natural resource in Iran was successfully employed to facile synthesis nanoparticle and nanosheets of activated carbon (AC) for refinement of methylene blue (MB) effluent. The structural features of prepared carbon nanoparticles and nanosheets were determined by BJH (Barret–Joyner–Halenda), TEM (transmission electron microscopy), FTIR (Fourier transform infrared), SEM (scanning electron microscopy) and XRD (X-ray diffraction) analysis. A combination of central composite design (CCD) with response surface methodology (RSM) has been applied to obtain a model and optimize the influencing variables on MB elimination by produced AC. More specifically, the impacts of influencing variables including sonication time, dye concentration, adsorbent mass, and temperature have been inspected. A total of 31 experiment sets were designed to achieve maximum adsorption percentage (R%) and adsorption capacity (qe). The best adsorption percentage, equal to 100%, was obtained under optimum conditions set as 0.20 g of adsorbent, MB concentration of 10.81 mg L−1, temperature equal to 44.2 °C, and 7.3 min of sonication time. The results exhibited that the pseudo-second-order and Langmuir model suitably suited to the experimental data of adsorption. The proposed technique in comparison with the recently reported techniques for cationic dye adsorption indicates that the bituminous coal-based AC by utilizing a cleaner production process has several remarkable advantages such as the abundance of raw materials, low cost, ease of production, sustainability, fast adsorption kinetics, and high-performance index.

Coal phase-outs and carbon prices: Interactions between EU emission trading and national carbon mitigation policies

The European Union Emission Trading System (EU ETS) constitutes the core instrument of the European Union climate protection policy. It limits greenhouse gas emissions of its member states and aims at facilitating an efficient allocation of emission reduction across national borders. Accompanying this policy at the European level, individual member states have introduced national mitigation policies, including renewable energy (RES) expansion measures or coal phase-outs.This study examines to what extent national policies affect the effectiveness of the EU ETS and to what degree the impact is reflected in prices for European Union Allowances (EUA). To investigate this question, a fundamental optimization model of the European electricity markets is deployed and model endogenous EUA prices are derived with a set of future market scenarios. Overall findings indicate that fundamental market forces strongly affect EUA prices. Furthermore, national policies play a critical role: The expansion of RES does not affect the capacity of the EU ETS to provide sufficient price signals for the desired level of decarbonization but a coal phase-out has a strong price-suppressing effect. A withdrawal of certificates can re-establish the effectiveness of the EU ETS but prices can rise drastically when overestimating the necessary amount.

A comparison of coal flow and carbon emissions in Shanxi province between 2011 and 2016

A comparison of coal flow and carbon emissions in Shanxi province between 2011 and 2016

Earth CO2 dynamics: from CO2 to organic matter and organic matter back to CO2 – an estimate of fluxes

The Earth CO2 is constantly changing. During photosynthesis CO2 is assimilated and immobilized in the form of organic matter. In the other way around, under the action of chemical and biochemical processes, the CO2 of the organic matter is released again into the atmosphere. The current concentration of CO2 in the atmosphere is about 390 ppm. Based on information from the literature, it is possible to estimate the amount of organic matter produced from the CO2 available in the atmosphere. On the other hand, by incinerating all the plant and animal organic matter on the Earth, it is possible to estimate the amount of CO2 produced and released to the atmosphere. In order to test these hypotheses, mathematical models were developed. By the models it is possible to estimate that if all CO2 in the atmosphere is assimilated via photosynthesis, it would produce 296 Mg.ha-1 of organic matter. On the other hand, by incinerating all vegetable and animal organic matter from the Earth, excluding petroleum, coal and other carbon sources, and considering an average value of 100 Mg.ha-1 the CO2 concentration in the atmosphere would increase by 131.8 ppm. This value added to the existing 390 ppm would raise CO2 concentration to 521.8 ppm. According to the models and results presented, forests may not be as important as carbon accumulators, making the environment conducive to life on Earth, but according to literature they are essential in the formation of rainfalls and maintenance of humidity, especially in areas far from the oceans and seas.

Thermodynamics and phase relationship of carbonaceous mesophase appearing during coal tar pitch carbonization

Carbonaceous mesophase appears as an intermediate product in production of electrical and mechanical carbon materials, needle coke for graphite electrodes used in electric-arc furnaces, pitch-based fibers and aluminum-smelting prebaked electrodes through carbonization process. A thermodynamic approach for phase behavior estimation of carbonaceous mesophase is presented to provide more insights and to lead to semi-quantitative modeling of this process. Phase behavior of binary, ternary and multi-component systems are described by minimization of the Gibbs free energy function proposed by Hu and Hurt for mesophase pitches which exhibits orientational energy contribution of molecules in mesophase. The model enables estimating the reversible phase transition of mesophase upon temperature cycling as suggested by Lewis. The capability of the model to estimate the molecular weight distribution of species in the phases in equilibrium and variation of mesophase content with thermal soaking time has been discussed. Estimated ternary isothermal sections showing isotropic-mesophase and iso-iso immiscibility are presented for the first time. The phase behavior of ternary systems with average molecular weight in the range of average molecular weight of coal tar pitches are described. The application of the model to phase diagram prediction of the specific systems which exhibit the miscibility gap has been studied.

Coal mines, carbon budgets and human rights in Australian climate litigation: Reflections on Gloucester Resources Limited v Minister for Planning and Environment

ABSTRACT This article examines the ground-breaking case of Gloucester Resources Limited v Minister for Planning and Environment in which, for the first time in Australia, a court endorsed the rejection of a coal mine partly on climate change grounds. This article provides an analysis of this case, which involved a challenge to a coal mine refusal, as a significant public interest case, and situates this case in the context of global climate litigation and previous litigation in Australia challenging the climate impacts of coal-fired power-stations and coal mines. It identifies how the decision established more ambitious, and climate-attentive, environmental standards for the assessment and approval of coal mines—especially due to its rejection of the ‘market substitution’ defense that has previously been relied upon by coal proponents and has been a major hurdle to successful climate litigation against coal mines in Australia. This article also suggests that this decision could, through its endorsement of the concept of a ‘carbon budget’, help advance future arguments that new coal mines and other fossil fuel developments should be refused due to the impacts climate change will have on a whole range of human rights.

A new approach of reduction of carbon dioxide emission and optimal use of carbon and hydrogen content for the desired syngas production from coal

This research is designed to make progress in overcoming the challenges through the development of a two-stage coal processing. Specifically, a two-stage process was used to maximize the use of the carbon in coal or increase the carbon monoxide yield or lower carbon dioxide and methane yields. Carbon dioxide-char gasification in the absence of water can generate carbon monoxide with near-zero methane, which is desired to produce high-carbon and low-hydrogen chemicals such as oxalic acid through catalytic carbon monoxide coupling and hydrolysis. The technology is applicable to any coal, although Power River Basin (PRB) coal is used as an example feedstock in this research Also, the sodium-iron catalyst can accelerate not only the reaction kinetics in both stages but also increase the hydrogen/carbon monoxide ratio in the syngas produced in the second stage. In other words, the catalyst is a multifunctional agent, which can not only intensify the overall coal process efficiency but also improve the qualities of the desired syngas products and reduce carbon dioxide emission. Thus, In the 1st stage, the catalysts can significantly reduce the CO2-char gasification by as high as 75.00%. In the 2nd stage, the H2/CO ratio of ideal syngas is ∼2:1 with near-0 CH4 generation and the CH4 production can be reduced as high as 61.29% for the CO2–H2O-Char coal gasification. The activation energy for the 2nd stage is reduced by as high as 35.43% than that of raw coal without use Na–Fe catalyst. The overall carbon footprint reduction for the study is reduced by 87.33% in the 1st stage and 96.77% compared to the direct coal combustion.

Coal-based S hybrid self-doped porous carbon for high-performance supercapacitors and potassium-ion batteries

A hybrid composed of sulfur self-doped 3D hierarchical porous carbon (S-3DHPC) with a high defect density area and a high specific surface is prepared through direct carbonization of coal and activators without any additional template. The synthesized S-3DHPC is directly used as an electrode for supercapacitors and potassium ion batteries. The large surface area of the three-dimensional carbon network allowed full contact of the electrolyte with the electrode interface, and the transport path of the electrolyte ions and K+ is shorter. In addition, S-type doping in hierarchical porous carbon improves the electronic conductivity and provides superior electrochemical performance. The S-3DHPC electrode with 431.7 F g−1 at 1 A g−1 in a 3 M KOH electrolyte demonstrates an adequate rate performance and cycle stability. In particular, the assembled S-3DHPC-based flexible symmetric supercapacitor exhibits a high energy density of 17.8 Wh kg−1 at a power density of 652 W kg−1. Furthermore, S-3DHPC as the anode for K-ion batteries exhibits a high reversible capacity of 212.9 mAh g−1 at 50 mA g−1, an excellent rate capability, and outstanding cycling performance. Therefore, S-3DHPC has broad application prospects as a high-performance energy storage electrode material.

Characterization of bio-coal briquettes blended from low quality coal and biomass waste treated by Garant\xae bio-activator and its application for fuel combustion

Experimental research was carried out on the manufacturing of bio-coal briquettes from a blend of two different types of low-quality coal and biomass waste in the absence of coal carbonization, where the third blend of the material was fermented by adding a bio-activator solution before pressurizing the components into briquettes. The coal samples from Caringin–Garut Regency (BB–Garut) had a low calorific value and a high sulfur content (6.57 wt%), whereas the coal samples from Bayah–Lebak Regency (BB–Bayah) had a higher calorific value and a lower sulfur content (0.51 wt%). The biomass added to the coal blend is in the form of fermented cow dung (Bio–Kohe), and it had a calorific value of 4192 kcal/kg and a total sulfur content of 1.56 wt%. The main objective of this study is to determine the total decrease in the sulfur content in a blend of coal and biomass in which a fermentation process was carried out using a bio-activator for 24 h. The used bio-activator was made from Garant® (1:40) + molasses 1 wt%/vol, and its used amount was 0.2 L/kg. Also, the total sulfur content in the blend was 1.00 wt%–1.14 wt%, which fulfills the necessary quality requirements for non-carbonized bio-coal briquettes. The pyritic and sulfate content in the raw coal was dominant, and the organic sulfur, when fermented with Garant®, was found to be less in the produced bio-coal briquettes by 38%–58%.

Understanding the molecular structure of HSW coal at atomic level: A comprehensive characterization from combined experimental and computational study

In this work, the coal samples from Hongshiwan (HSW) mining area, Ningxia, northwest of China, are characterized by using several modern materials characterization techniques, such as proximate and ultimate analyses, solid state 13C nuclear magnetic resonance (13C NMR), X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy (FT-IR). Then the key information about elements, valence, and chemical bonding for coal molecular structural construction is obtained. The results reveal that the main structure of HSW coal has 75.96% aromatic skeleton in mass. The ratio of aromatic bridge carbon to aromatic peripheral carbon of HSW coal is 0.315, indicating more naphthalene than benzene and anthracene in coal structures. Oxygen predominantly presents in the forms of ether (C–O), carbonyl (CO) and carboxyl (–COO). Nitrogen presents in the forms of both pyridine and pyrrole. Methyl (–CH3) group is predominant in cyclic and aliphatic hydrocarbons. Based on obtained structural information and the approaches of average molecular structure, the single molecular formula of HSW coal is defined as C221H148O28N2, with a molecular weight of 3142.32. Also, the 2D and 3D molecular model of HSW coal are built with computer-aided modeling. The model is optimized and further verified by FT-IR and 13C NMR spectra simulation with quantum chemical calculations. Besides, a more complicated structure of complex model for HSW coal containing 10 single-molecules is also obtained. Therefore, molecular structure of HSW coal has been comprehensively depicted and understood at atomic level from both experimental and quantum chemical approaches in the current work.