Coal Carbon Research Articles

Numerical investigation of the physical-thermal-chemical behaviours of particles during coal combustion and desulfurization processes in a CFB combustor

The desulfurization process has been practised for the clean utilization of coal in chemical engineering fields, yet the physical, thermal, and chemical characteristics of particles are still lacking understanding. In this work, a comprehensive numerical model based on the Eulerian-Lagrangian framework was established to study the particle behaviours during coal combustion and desulfurization processes in a pilot-scale circulating fluidized bed (CFB) combustor. After model validation, the effects of several crucial operation parameters (e.g., excess air ratio, calcium to sulphur ratio, and calcium oxide size) on particle behaviours are illuminated. The results show that density-induced segregation causes coal particles to accumulate in the upper part of the riser. The sand, coal, and CaO particles have time-averaged Reynolds numbers of 15, 6.5, and 0.5, respectively. The particle temperature is higher in areas with lower solid concentrations. Increasing excess air ratio (ϕg) decreases the temperature of sand particles but elevates that of coal and CaO particles. The average particle heat transfer coefficients (HTCs) for sand, coal, and CaO particles are 205 W/m2·K, 172 W/m2·K, and 275 W/m2·K, respectively. With the increase in ϕg, the HTC of sand particles increases but that of CaO particles remains unchanged, additionally, the mass of coal particles decreases and the mass of carbon in coal particles decreases along with the riser. The influence of the Ca/S ratio and CaO size on the axial distribution of coal particle mass and carbon mass fraction is negligible. For each particle species, the axial dispersion coefficient (Dz) is two orders of magnitude greater than the radial ones (Dx, Dy), indicating that the vertical introduction of the fluidizing gas dominates the dense gas-solid flow in the riser.

Exploring the Linkage Effects between Coking Coal Futures and Carbon Emission Rights Prices under the Dual-Carbon Framework

Coking coal is a vital energy resource for economic development, with fluctuations in coking coal futures prices significantly guiding spot prices. Additionally, variations in carbon emission rights prices directly affect China's energy conservation and emission reduction efforts. This paper examines the daily trading prices of carbon emission rights and coking coal futures. It utilizes various tests, including the ADF test and cointegration test, and constructs a two-dimensional vector autoregression (VAR) model with a two-period lag. The paper also performs an impulse response function analysis and variance decomposition. Empirical results reveal: First, the daily trading prices of coking coal futures have exhibited a fluctuating upward trend over the past six years; Second, there is a long-term cointegration relationship between coking coal futures prices and carbon emission rights prices; Third, there is no Granger causality between the two; Fourth, fluctuations in carbon emission rights prices have a stronger guiding effect on coking coal futures prices than vice versa. Recommendations include: (1) Strengthening oversight of the coking coal futures market and leveraging policy guidance to prevent extreme prices; (2) Systematically including more participants in the carbon market, optimizing the trading structure, and promoting healthy market development; (3) When developing policies for carbon emission rights, the government should mitigate the impact of price fluctuations on other sectors.

Tailoring the Optical Properties of Coal Pitch-Derived Carbon Dots by Graphitization Controlling

Tailoring the Optical Properties of Coal Pitch-Derived Carbon Dots by Graphitization Controlling

Reaction mechanism of catalytic gasification by calcium-based catalysts and oxidized coal residues in coalfield fire zones

Fires originating from coal spontaneous combustion within coalfields result not only in substantial coal resource depletion but also producing residual low-activity pyrolysis coal chars exhibiting varying degrees of oxidation. These chars develop progressively through successive heat penetration at the fire front and post-fire extinguishment phases. This paper focuses on the alkaline earth metal-activated catalytic gasification of residual oxidized coal in fire zones, constructs a carbon-based model of oxidized coal in fire zones. The results show that the reaction active sites of the oxidized coal carbon matrix model are mainly concentrated on the carbon atoms at the end of the aromatic ring. During catalytic gasification, the calcium-based catalyst engages with these active sites, forming a preliminary catalyst. The transformation of oxidized coal into CO primarily occurs through two distinct routes. Calcium attaches to the surface of the oxidized coal’s carbon-based structure, establishing active sites. Acting as a facilitator, it aids the movement of CO2 to the carbon-based surface, leading to its further breakdown into CO. The catalytic species containing calcium persistently amalgamates with active sites on coal coke surface, fostering the release of additional CO. Moreover, these catalytic species with calcium also bind CO2 and unite with active coal coke sites, generating carbon–oxygen complexes on the surface. These complexes are thermally unstable and decompose, yielding CO and initiating the formation of fresh active sites on the coal coke surface. Consequently, they interact further with calcium-based catalytic species, culminating in the creation of catalyst precursors, which drive a recurrent catalytic reaction process.

OBTAINING POROUS CARBON MATERIAL AND INVESTIGATION OF ITS PHYSICAL AND CHEMICAL PROPERTIES

The proposed method for producing porous carbon material involves the thermal decomposition of brown coal from Kazakhstan deposits, optimized by a treatment process where steam is used for coal activation, enhancing the safety of the process. The resulting product exhibits high characteristics, including high dielectric permittivity, specific surface area, and capacity, making it effective for use in supercapacitors as an electrode material and for hydrogen storage. The coal carbonization process includes an initial low-temperature (at 180°C, with a heating rate of 10°C/min) treatment of the raw material in the presence of air for 1 hour, followed by carbonization in an inert atmosphere at temperatures ranging from 180-900°C with a heating rate of 5°C/min, and steam activation at the maximum temperature for 1 hour of the coal ground to a 0.1 mm fraction. The material is then extruded into cylindrical shapes (diameter: 2-3 mm, length: 5-10 mm) using a binder material: starch - 5%, sodium hydroxide - 0.5%, water - 17%.

Impact of external moisture on quantitative analysis of coal and rapid drying by a CO2 laser to improve prediction accuracy based on laser induced breakdown spectroscopy

For high-accuracy determination of ash, fixed carbon, and volatile matter in coal, generally, the impact of external moisture content in coal must be considered and removed in quantitative modeling based on laser-induced breakdown spectroscopy (LIBS). Herein, the ash, fixed carbon, and volatile of coals with moisture contents from 3% to 15% are quantitatively assessed using partial least squares based on principal component analysis (PCA-PLS), and the predictive limit of this model for moist coals is explored based on LIBS. To validate the industrial feasibility of the method, an infrared CO2 laser based heating technique is employed to rapidly dry the moist coals before laser ablation. The results demonstrate that root mean square error of prediction (RMSEP) of all ash, volatile carbon, and fixed carbon become higher with moisture content increase. Nevertheless, as the moisture content reaches 3%, the prediction model retains an acceptable predictive capability with mean absolute error (MAE) of ash, volatile matter, and fixed carbon of 1.85%, 1.5%, and 1.79%, respectively. When the IR laser for drying is employed to irradiating for 40 ms, external water in coal with an original moisture content of 15% can be quickly removed, resulting in a decrease in RMSEP of ash, volatile matter, and fixed carbon from 3.06%, 5.42%, and 6.22% to 1.47%, 3.16%, and 3.34%, respectively. This method provides a potential technical solution for the use of infrared laser-assisted LIBS real-time online rapid detection of indicators in raw coal with high moisture content.

A new pathway to integrate novel coal-to-methanol system with solid oxide fuel cell and electrolysis cell

Considering the significant emissions associated with conventional coal-to-methanol (CTM) systems and the increasing demand for renewable energy consumption, this study proposes a novel scheme for CTM, which couples a solid oxide fuel cell (SOFC) and solid oxide electrolysis cell (SOEC). The objective is to reduce coal consumption and carbon emissions. The proposed scheme involves introducing green hydrogen, enriching CO2 concentration, and recovering it from exhaust gas. A system simulation model was developed using Aspen Plus/Aspen Custom Modeler software for the design and sensitivity analysis. The design results demonstrate that by utilizing green hydrogen produced through H2O electrolysis in the methanol synthesis process, the coal consumption per unit of methanol production can be reduced from 1.26 kg/kg to 0.74 kg/kg. Moreover, by employing SOFC instead of conventional heat boiler system, the CO2 concentration in CTM exhaust can be significantly improved from 9.11 % to 30 %, enhancing the efficiency of carbon separation. The inclusion of a CO2 electrolysis process helps converting CO2 into a part of methanol capacity and achieving zero-carbon emissions. The findings aim to provide a reference basis and theoretical guidance for the design, optimization, and integration of renewable energy sources into the novel coal-to-methanol system with solid oxide cells.

Innovative strategy for the effective utilization of coal waste slag in the Fenton-like process for the degradation of trichloroethylene

In response to environmental concerns at the global level, there is considerable momentum in the exploration of materials derived from waste that are both sustainable and eco-friendly. In this study, CS-Fe (carbon, silica, and iron) composite was synthesized from coal gasification slag (CGS) and innovatively applied as a catalyst to activate PS (persulfate) for the degradation of trichloroethylene (TCE) in water. Scanning electron microscope (SEM), fourier transmission infrared spectroscopy (FTIR), energy dispersive x-ray spectroscopy (EDS), brunauer, emmet, and teller (BET) technique, and x-ray diffractometer (XRD) spectra were employed to investigate the surface morphology and physicochemical composition of the CS-Fe composite. CS-Fe catalyst showed a dual nature by adsorption and degradation of TCE simultaneously, displaying 86.1% TCE removal in 3 h. The synthesized CS-Fe had better adsorption (62.1%) than base material CGS (36.4%) due to a larger BET surface area (770.8 m2 g−1), while 24.0% TCE degradation was recorded upon the activation of PS by CS-Fe. FTIR spectra confirmed the adsorption and degradation of TCE by investigating the used and fresh samples of CS-Fe catalyst. Scavengers and Electron paramagnetic resonance (EPR) analysis confirmed the availability of surface radicals and free radicals facilitated the degradation process. The acidic nature of the solution favored the degradation while the presence of bicarbonate ion (HCO3−) hindered this process. In conclusion, these results for real groundwater, surfactant-added solution, and degradation of other TCE-like pollutants propose that the CS-Fe composite offers an economically viable and favorable catalyst in the remediation of organic contaminants within aqueous solutions. Further investigation into the catalytic potential of coal gasification slag-based carbon materials and their application in Fenton reactions is warranted to effectively address a range of environmental challenges.

Isotopic composition of carbon (δ13C) and nitrogen (δ15N) of petrologically different Tertiary lignites and coals

This study investigates the carbon (δ13Corg) and nitrogen (δ15N) isotopic composition of tertiary lignites and coals from six sedimentary basins: Velenje, Mura-Zala, and Zasavje in Slovenia; Sokolov in Czech Republic, Barito in Indonesia; and Istria in Croatia. The aim is to investigate the correlation between the fine detrital (fD) component and δ13C and δ15N in Velenje lignite samples. Additionally, we aim to evaluate the biogeochemical processes of organic substances during their deposition in all analyzed samples, calculate their δ13CCO2 values and compare the analyzed values of δ13C and δ15N to those reported in the literature. Thirty-two samples were analyzed, predominantly from the Velenje ortho-lignite (Pliocene), with additional lignites and coals from the Pannonian to Paleocene epochs for comparison. Carbon isotopic composition (δ13Corg) ranged from -27.9 to -23.6 ‰, and nitrogen isotopic composition (δ15N) ranged from 1.8 to 7.4 ‰. The fine-detrital lithotypes of the Velenje ortho-lignite exhibited the most negative δ13Corg values due to anaerobic bacterial activity in an intramontane alkaline lake environment influenced by the carbonate hinterland. Moreover, gelification processes affected fine-detrital organic matter more than larger wooden pieces. Terbegovci, Hrastnik meta-lignites, and Barito sub-bituminous coal also displayed low δ13Corg values, indicating limited gelification, while variations in the δ15N values suggested differences in mineralization. The Velenje xylitic lithotypes have higher δ15N values, indicating a more intense mineralization under aerobic conditions. Raša ortho-bituminous coal, deposited in a brackish environment, displayed the highest δ13Corg values and a wide range of δ15N values due to fluctuating water tables in a paralic carbonate platform environment. The lowest δ15N value was observed in the Sokolov Basin lignite coal, indicating minimal mineralization and low bacterial activity. The isotopic composition of CO2 in air (δ13Cair), which was calculated using the δ13C values in lignites and coal, ranged from -8.4 to -3.4 ‰, with Velenje lignite displaying the minimum value and Raša coal showing the maximum value. The determined δ13C and δ15N values of the coal and lignite samples in this research fall within the typical range of world coals.

Microscopic Structural Evolution of Oxidized Coal Residues with Different Oxidation Degree.

Coalfield fires represent a critical environmental and safety concern, warranting a comprehensive understanding of the factors influencing the reactivity of oxidized coal residues within fire zones. This study investigates the influence of the oxygen volume fraction and oxidation temperature on the residual structure of oxidized coal, elucidating the underlying mechanisms driving reduced coal reactivity. The representative oxidation conditions for coalfield fire zones were determined. Through industrial and elemental analyses, complemented by methods such as infrared diffuse reflection, specific surface area determination, and pore size analysis, results indicate that higher temperatures and oxygen levels decrease volatile matter and fixed carbon, notably above 400 °C due to oxygen-deficient combustion. Hydroxyl groups decrease with a rising temperature in high oxygen conditions, while carboxyl groups increase at lower temperatures with elevated oxygen. Oxygen-lean and high-temperature conditions reinforce the coal structure, evidenced by the reduced condensation index in aromatic hydrocarbon. Oxidation alters the pore morphology, progressing from micropores to larger irregular pores through various stages, including pore formation, expansion, and merging. Elevated oxygen levels intensify oxidation, consuming the coal carbon matrix and reducing micropores, hindering internal gas diffusion, which is the key to a reduced coal reactivity in fire zones.

The pressure of coal consumption on China's carbon dioxide emissions: A spatial and temporal perspective

As the world's largest coal consumer, China is facing the dual challenge of implementing strict coal reduction policies while heavily relying on coal. It is crucial to comprehend the pressures exerted on carbon dioxide emissions from coal consumption as China strives to transition towards a carbon-neutral era. This study defines and classifies the pressure of carbon dioxide emissions resulting from coal consumption, referred to as “carbon-coal pressure”, in 30 provinces (including municipalities and autonomous regions) from 1997 to 2019. This classification enriches the study of the pressure on carbon dioxide emissions by specific energy types. By calculating the centre of gravity of the carbon-coal pressure and its evolution trends, the spatial pattern of the carbon-coal pressure and the evolution characteristics of the centre of gravity of the pressure are revealed. The results demonstrate that, despite the continuous growth in total coal consumption and carbon dioxide emissions in China, the carbon-coal pressure index exhibits a decreasing trend in certain regions, with significant inter-regional differences. Most provinces fall into the high-pressure and higher-pressure categories. The number of high-pressure provinces has decreased by 33% from 18 to 8, while the number of low-pressure provinces has risen from 0 to 1, and both higher and medium pressure types have increased. The overall stress index decreases from 0.79 to 0.7. The pressure centre displays a similar spatial trend to the overall changes in coal consumption and carbon dioxide emissions centre, albeit with a smaller magnitude of change. Beijing stands out as the only province with low pressure.

In-situ capture defects through molecule grafting assisted in coal-based hard carbon anode for sodium-ion batteries

Sodium-ion batteries is not essential but also potential to support energy storage system due to the low cost. It's worth noting that low price and high carbon production helps coal extraordinary promise as hard carbon precursor. However, low initial coulombic efficiency (ICE) and practical Na+ storage specific capacity barrier their application owing to lots of defects. Herein, a grafting method is proposed to decrease defects, introducing glucose with simple one step carbonization process. Utilizing the reaction between glucose and coal reduces the defects, which generates a high ICE with less irreversible sodium ion consumption. Meanwhile the expanded carbon layer spaces enable the fast sodium ions transfer, leading to an optimized sodium storage performance. The grafted glucose obviously decreases the defects during the carbonization process and contributes extra sodium storage capacity. The optimal CG0.1 exhibits higher reversible capacity of 293 mAh∙g−1 and ICE of 84 % than pristine coal pyrolytic carbon (250 mAh∙g−1 and 79 %). Besides, it also delivers outstanding capacity retention with 95.3 % and 95.8 % after 1000 cycles at 0.3 A∙g−1 (240 mAh∙g−1) and at 1 A∙g−1 (207 mAh∙g−1).

Coal consumption and carbon emission reductions in BRICS countries.

The primary energy consumption structure of BRICS countries is dominated by fossil energy, particularly coal. Coal consumption in BRICS countries is a major driver underlying increased carbon emissions. Therefore, this study developed a spatiotemporal decoupling mode and incorporated factors related to coal consumption-induced carbon emissions into a spatiotemporal decoupling analysis method to provide differentiated and targeted policies for energy restructuring and emission reduction targets in BRICS countries. Moreover, a temporal-spatial decomposition logarithmic mean Divisia index model was developed using the spatiotemporal decoupling index method. The model is based on CO2 emissions generated by coal consumption in BRICS countries, with a primary focus on data from Brazil, Russia, South Africa, India, and China. The findings reveal distinct spatiotemporal distributions and driving effects of coal consumption and carbon dioxide emissions across various countries. Factors such as CO2 emission intensity, coal consumption intensity, economic output per capita, and population structure exerted either positive or negative effects on the distributional effect of the carbon emission-economic output per capita association in BRICS countries. Additionally, country-level heterogeneity in the influence of the distributional effects of CO2 emissions was observed within each BRICS country. Thus, different policies are needed to achieve carbon emission reduction targets in different countries.

Coal Control and Carbon Reduction Path in Henan Province's Power Industry Under the Carbon Peak and Neutralization Target: A Medium- and Long-term Study

Achieving peak carbon dioxide emissions and accelerating decarbonization progress in the power industry is of paramount significance to Henan Province's objective of achieving carbon peak and neutrality. In this study, the Carbon Emission-Energy Integrated Model (iCEM) was employed to conduct scenario studies on the coal reduction and carbon reduction paths under the "dual-carbon" goal of Henan's power industry. The results indicated that, by considering measures such as optimizing the power source structure and technological progress, Henan Province's power industry carbon emissions will reach their peak between 2028-2033, with coal consumption in the power industry continuing to grow during the "14th Five-Year Plan" period. With a peak range between 2027-2031, the peak value increased by 1881, 1592, and 11.48 million tce, respectively, compared with that in 2020. To control coal in Henan Province under the constraint of carbon peak goals, it is proposed to develop clean energy sources such as wind and solar power, use more low-carbon or zero-carbon heat sources, increase the proportion of external electricity supply, and enhance energy-saving transformation in coal-fired power plants. Accelerating the elimination of backward units and energy-saving transformation of existing units, accelerating non-fossil energy development, advanced planning for external electricity supply, improving market mechanisms for the exit of coal-fired power plants and peak regulation, increasing system flexibility, and accelerating external policies to ensure clean energy security are effective paths for controlling coal and reducing carbon emissions in Henan's power industry. Additionally, inland nuclear power layout is one of the crucial paths to alleviate coal control pressure in Henan Province and achieve "dual-carbon" goals during the carbon-neutral stage. Therefore, it is imperative to conduct research on demonstrations in advance. Henan Province is highly dependent on energy from other provinces, and the power supply and demand situation in Henan Province will become increasingly tense in the future. It is necessary to support Henan Province from the State Grid and coordinate the construction of inter-provincial and inter-regional power transmission channels.

The influence mechanism of ionic liquids on the ash melting and combustion characteristics of Zhundong high-alkali coal

ABSTRACT This study investigated the ash reduction and quality improvement effects of four types of ionic liquids on Zhundong high-alkali coal, focusing on the evolution laws of coal ash melting and combustion performance under the ionic liquid system, which provided a theoretical basis for the subsequent utilization of high-alkali coal. Ionic liquids can effectively reduce inorganic mineral content and volatile matter yield, increase fixed carbon and oxygen content in coal, and reduce hydrogen and sulfur content. The silicon-aluminum ratio of coal ash increased, and the content of low-melting minerals in coal ash decreased, while the content of refractory minerals increased, leading to an increase in the melting temperature of coal ash. Ionic liquids can inhibit the oxidation reaction of coal, which is beneficial for suppressing spontaneous combustion of coal and improving safety during storage and transportation.

GASIFICATION TECHNOLOGY AND ITS FUTURE: A REVIEW

Gasification technology has the potential to revolutionise the energy industry by providing a clean and efficient way to produce energy from a variety of raw materials. This technology have the ability to produce synthesis gas from raw materials based on negative or low carbon values such as high sulphur fuel oil, petroleum coke, coal, domestic wastes, industrial and biomass wastes. The gas produced from the process is used to replace natural gas, to generate electricity, or as a basic raw material to produce chemicals and liquid fuels. Gasification is a process that uses heat, pressure, and steam to convert substances directly into gases, such as carbon monoxide and hydrogen. Gasification technology has differences in various aspects but there are four engineering factors that are the core of the gasification system such as atmospheric gasification reactor (level of oxygen or air content), internal and external heating, reactor design and operating temperature. The raw material used, prepared and introduced in dry form and small particles to the reactor chamber are called gasification. Raw materials experience heat, pressure and an environment rich or low in oxygen content in the gasification. There are three main products from the gasification process which are hydrocarbon gas (also called syngas), hydrocarbon liquid (oil) and coal (carbon black and ash). Syngas can be used as a fuel to produce electricity or steam or as a based material for many types of chemicals. When mixed with air, syngas can be used in petrol or diesel engines as a vehicle fuel with minor modifications to the engine. Gasification technology has several advantages over traditional fossil fuel-based energy production methods. It is able to produce energy from a wide range of raw materials, including waste, which reduces the need for landfills and incineration. Additionally, gasification can reduce greenhouse gas emissions by producing energy from low or negative carbon value raw materials.

An investigation to enhance the performance of molten carbonate-direct coal/carbon fuel cells through improvements in anode layouts and the compositions of carbonate electrolyte

Two anode configurations are systematically tested in composite electrolytes of molten carbonate with Cs2CO3 at various temperatures using different carbon fuels, including bituminous coal, bituminous coal char, carbon black, and graphite powder. The results of electrochemical impedance spectroscopy show that electrolytes composed of (Li-K)2CO3 62:38 doped with 20 wt% Cs2CO3 and utilizing graphite powder as a fuel exhibit reduced ohmic and charge transfer resistance. This can be attributed to the decreased surface tension, which enhances the gas solubility of the reactants within the electrolytic matrix. The analysis of particle size distribution through laser diffraction reveals that the graphite specimen has the smallest mean particle size, resulting in an enhanced rate of electrochemical oxidation. The ultimate and proximate analysis indicates that graphite powder has a lower moisture and ash ratio along with a significantly higher fixed carbon content compared to other carbon fuels. Therefore, the obtained V-j &P-j curves in Anode 1 illustrate that graphite powder yields the highest current density and power density of 903 mA/cm2 and 172 mW/cm2, respectively, at an operating temperature of 680 °C under the laboratory conditions. These values surpass those reported in the existing literature. In contrast, Anode 2 exhibits low performance, due to ash particles regime-controlled at the lower part of the chamber during the coal pyrolysis. Based on results, we suggest that graphite powder is the promising fuel candidate for MC-DCFC to achieve the higher performance.

Effect of lignin on coal slime combustion characteristics and carbon dioxide emission

The escalating total amount of industrial solid waste is increasingly taxing the ecological environment. Co-combustion technology is seen as a potential solution to this problem. This study investigated the interaction mechanism and carbon dioxide emissions during the co-combustion process of coal slime and biomass (lignin) using a programmed heating method. The experimental results reveal that the two sub-reaction models effectively depict the combustion process of coal slime. In the co-combustion process, the comprehensive combustion and ignition performance of the mixed fuels surpasses that of coal slime, but the stability of the combustion flame is reduced. The combustion performance of the mixed fuel is primarily influenced by two common factors. The interaction between lignin and coal slime significantly changes with the variation of mixing ratio and heating rate. The main product in the combustion process of mixed fuels is carbon dioxide. Due to the competition for oxygen among volatile matter, the emission of carbon dioxide is lower than the theoretical value. When the mass percentage of lignin is 70 %, the impact on carbon dioxide is most pronounced. The experimental results of this study provide a foundation for understanding the interaction mechanism of coal slime and biomass co-combustion. The research findings also provide theoretical guidance for the safe operation of coal slime and biomass co-combustion equipment.

Relevance between various phenomena during coking coal carbonization. Part 4: Insight into the interaction of coal blending

Medium metamorphism strong bonding properties coal is usually used as the main coal in the coal blending scheme. A study of the matching effect of low metamorphism coal is conducive to expanding the utilisation of coal resources. Three kinds of coal: C1 (low metamorphism with strong bonding properties), C2 (low metamorphism with weak bonding properties), and C3 (middle metamorphism and strong bonding properties) were used as research samples. The thermogravimetry-plastometer-swelling pressure (TG-P-SP) apparatus was used to measure the release behaviour of volatiles, the evolution of quantity and performance of the plastic layer, and the change of swelling pressure and volume deformation by mixing C1 and C2 with C3 in different proportions. Blending C1 and C3, the release of volatiles and the evolution of the plastic layer shifted toward the low-temperature zone, and the semi-coke yield was lower than the theoretical expectation. C3 had a strong chemical effect on C1. Other proportions were investigated, although the plasticity was inhibited only when the proportion was equal. The final shrinkage was lower than the predicted result. Blending C2 and C3, the release rate of volatiles was inhibited, and the yield of semi-coke was consistent with the calculation results, and the plasticity of the plastic layer was inhibited. The release behaviour of volatiles and the plastic layer had the opposite effect on the shrinkage interaction. The final shrinkage was close to the ideal calculation value. The interaction was the combination result of coal composition, the correlation among various phenomena, and the multiple interactions of phenomena of coal blending.

Methane production from the biodegradation of lignite with different sizes by mixed fungi-methanogen microflora.

Biogenic coalbed methane (CBM) is a developing clean energy source. However, it is unclear how the mechanisms of bio-methane production with different sizes of coal. In this work, pulverized coal (PC) and lump coal (LC) were used for methane production by mixed fungi-methanogen microflora. The lower methane production from LC was observed. The aromatic carbon of coal was degraded slightly by 2.17% in LC, while 11.28% in PC. It is attributed to the proportion of lignin-degrading fungi, especially Penicillium, which was reached 67.57% in PC on the 7th day, higher than that of 11.38% in LC. The results suggested that the limited interaction area in LC led to microorganisms hardly utilize aromatics. It also led the accumulation of aromatic organics in the fermentation broth in PC. Increasing the reaction area of coal and facilitating the conversion of aromatic carbon are suggested means to increase methane production in situ.