Inertinite Content Research Articles

Perchloroethylene (PCE) adsorption on coal macerals as derived from micro-FTIR spectroscopic analysis and mapping of the C=C bonds from PCE

ABSTRACT Organic liquids are used to prepare the density medium to produce clean coal composites for coal quality and coking test evaluations during the coal exploration stage. Perchloroethylene (PCE) is commonly used as a density medium for this procedure; however, it has been shown before that PCE affects Gieseler Fluidity and Ruhr Dilatation indices of coal, as well as the quality of the resulting coke. It was also found that PCE has a negative effect on the coking properties of coals with a high inertinite content. This paper investigates the adsorption of PCE on various coal maceral surfaces using micro-Fourier Transform Infrared Spectroscopy (micro-FTIR) analysis to observe the changes in the absorbance of the double carbon bond C = C (C = C absorbance peak is used as a marker to indicate the presence of PCE) before and after PCE was applied onto their surfaces. The micro-FTIR mapping of absorbance intensity of the C = C bond on coal macerals showed an increasing trend in the presence of these bonds on the surface of all macerals with the time after exposure to the PCE. The SEM- energy-dispersive X-ray spectroscopy was used to analyze the composition of minerals associated with fusinite and semifusinite, as they were filling the pores in these macerals.

A new equation for the prediction of coal self-heating based on maceral content

ABSTRACT The potential of occurrence of coal self-heating is controlled by various properties, both intrinsic and extrinsic. In the intrinsic properties, the maceral content has an important role in influencing its occurrence. This parameter has not been discussed in a comprehensive study among the researchers. Thus, the study of the influence of this parameter on coal self-heating is required. In the present work, the coal self-heating potential was predicted based on the maceral content. A total of 51 coal samples from different underground coal fields in Iran with different percentages of maceral content were collected, and R70 test method was carried out on each coal sample. Then, the regression analysis technique was used for modeling and predicting the coal self-heating potential. For validation and testing, 11 coal samples were randomly gathered from coalfields, and R70 test method was carried on each coal sample and results obtained were compared through a regression analysis. By examining and comparing the results and values obtained from R70 test method and the regression analysis, it was found that increase in the vitrinite and liptinite contents and decrease in the inertinite content increased the coal self-heating potential.

Nitrogen injection to enhance methane and water production: An experimental study using the LF-NMR relaxation method

Nitrogen injection is an effective way to improve coalbed methane (CBM) recovery, but there are few studies of the regularity of fluid flow during nitrogen injection. To study the flow of methane and water during nitrogen injection into coal reservoirs, a high-volatile bituminous B coal from the southern margin of the Junggar Basin, Xinjiang and a low-volatility bituminous coal from the central and eastern regions of the Qinshui Basin, Shanxi province were selected, and the real-time flow of methane and water in a coal reservoir under nitrogen injection was monitored by low-field nuclear magnetic resonance (LF-NMR). The results showed that, without nitrogen injection, primarily free methane (bulk methane and methane confined in porous media) and very little adsorbed methane are produced. The rate of production of methane increases logarithmically with time and reaches a balance after a period of time. With nitrogen injection, the production balance is broken, resulting in the flow and production of adsorbed methane, and the production rate is significantly improved. It is suggested that nitrogen injection provides a sustained driving force for the desorption of absorbed methane and flow of methane that causes the production rate to increase linearly with time. The flow of methane is asynchronous during the stages with and without nitrogen injection; that is, the bulk methane is produced first, followed by the methane confined in porous media and finally, the adsorbed methane. This occurs because the resistance to the flow of the methane present in different pore apertures is different, resulting in differences in the flow of methane with time. Nitrogen injection has a significant effect on the production of free water and capillary water but no obvious effect on absorbed water. By comparing two samples with different coal ranks, material composition and fracture development, it is found that the nitrogen injection effect on high-volatile bituminous B coal with more fractures and higher inertinite content is better than the nitrogen injection effect on low-volatility bituminous coal. Nitrogen injection significantly enhanced the recovery of CBM by improving the production of adsorbed methane and free water under in situ reservoir conditions; for reservoirs with different physical properties, the stimulation effect will differ.

Comparative study on sorption characteristics of coal seams from Barakar and Raniganj formations of Damodar Valley Basin, India

The methane retention mechanism in coal seams is markedly different from those of conventional gas reservoirs. Methane remains mainly as physically adsorbed molecules on micropore surface. Chemical and petrographic compositions of coal are the measures of maturity and type of organic matter that control the methane sorption characteristics of the coal. 99% of Indian coal occurrences are contributed by lower Gondwana sequences housed in two major geologic formations, younger Raniganj and older Barakar. The Raniganj Formation is best exposed in Raniganj Sub-basin and Barakar Formation is best exposed in Jharia Sub-basin of Damodar Valley. Present work attempts a systematic investigation on comparative account of methane sorption characteristics of coals from Raniganj Formation of Raniganj Sub-basin and Barakar Formations of Jharia Sub-basin in relation to their chemical composition and petrographic makeup. Chemical analyses shows that moisture, ash, volatile matter and fixed carbon varies between 2.5 and 4.6%, 10.0–27.2%, 38.8–40.2% (dmmf) and 59.8–61.2% (dmmf), respectively for Raniganj coals and, 0.5–1.1%, 16.7–32.9%, 20.7–22.0% (dmmf) and 78.0–79.3% (dmmf), respectively for Barakar coals. Carbon content is distinct for the suites of coal, 79.2–85.4% and 85.6–92.0% for Raniganj and Barakar coals, respectively. The vitrinite reflectance for the Raniganj coals ranges 0.53–0.72% and the Barakar coals ranges 1.09–1.23%. Based on the chemical composition and vitrinite reflectance value Raniganj coals belongs to high volatile bituminous type, whereas Barakar coals belongs to high to medium volatile bituminous type. Such variation in composition and maturity is mainly attributed to the variation in precursor organic matter as well as the basinal and thermal history of the sub-basins under consideration.H/C atomic ratio of the Raniganj and Barakar coals varies between 0.65 and 0.80 and 0.51–0.72 and O/C atomic ratio varies between 0.05 and 0.13 and 0.01–0.07, respectively. Coals of both the Raniganj and Barakar formations are mostly of kerogen Type-III with Raniganj coals falling in wet gas maturity stage approaching early-thermogenic methane generation whereas Barakar coals falling in condensate gas stage approaching peak-thermogenic methane generation. The Langmuir volume ranges from 9.3–21.8 cc/g (daf) for Raniganj coals and 21.1–29.1 cc/g (daf) for Barakar coals. Sorption capacity for the set of coals shows a strong rank dependency and increase with corresponding increase in rank down the stratigraphic column. Methane sorption capacity shows positive relationship with carbon content and vitrinite reflectance, and negative relationship with moisture content, ash and volatile matter. Moisture effect is more prominent in low rank Raniganj coals. The adsorption capacity shows a strong positive relation with vitrinite content and a moderate negative relation with inertinite content for both the Raniganj and Barakar coals, which may be attributed to dominancy of micropores in vitrinites with rank enhancement. The multiple regression analysis shows that the moisture is the main predictor of the VL, and the interaction of moisture with ash and reflectance mainly control the sorption capacity. A predictive model equation is developed for determination of sorption for Damodar basin coals from carbon, ash and moisture data.

Characteristics of Early Cretaceous wildfires in peat-forming environment, NE China

Inertinite maceral compositions in coals from the Early Cretaceous Erlian, Hailar, and Sanjiang Basins in NE China are analyzed in order to reveal palaeowildfire events and palaeoclimate variations. Although huminite is the dominant maceral group in the studied basins, the inertinite group, as a byproduct of palaeowildfires, makes up a considerable proportion. Occurrence of inertinite macerals indicates that wildfires were widespread and frequent, and supports the opinion that the Early Cretaceous was a “high-fire” interval. Inertinite contents vary from 0.2% to 85.0%, mostly within the range of 10%–45%, and a model-based calculation suggests that the atmospheric oxygen levels during the Aptian and Albian (Early Cretaceous) were around 24.7% and 25.3% respectively. Frequent fire activity during Early Cretaceous has been previously related to higher atmospheric oxygen concentrations. The inertinite reflectance, ranging from 0.58%Ro to 2.00%Ro, indicates that the palaeowildfire in the Early Cretaceous was dominated by ground fires, partially reaching-surface fires. These results further support that the Cretaceous earliest angiosperms from NE China were growing in elevated O2 conditions compared to the present day.

Petrographic analysis of hard coal in grain class

There are presented results of petrographic analysis of the finest class of hard coal (<1mm). Examined Medium-Rank coals – orthobituminous C – came from four seams of western part of Upper Silesian Coal Basin. The coal samples have been obtained from froth flotation in processing plant. Microscopic analysis comprised defining of vitrinite reflectance and determining of percentage of maceral groups and group of microlithotypes. Petrographic characteristic of examined coals enable to count them to high-vitrinite coals with vitrinite content V = 22-88%vol., low liptinite content L = 2-3%vol. and medium inertinite content I = 3-11%vol. (where the most often semifusinite and inertodetrinite occurred). The highest content of mineral matter (72%vol.), carbominerites and rock have been stated obviously in tailings. Concerning grain size (<1 mm) detailed determining of the art of mineral matter using microscope in transferring light was impossible – there were distinguished only quartz and feldspars. There was mostly approved occurring of isolated macerals. Too fine granulation (<1mm) did not allow to conduct combine analysis, because grain size classified counting mainly as mentioned `isolated` macerals or `on the border of the grain`. The amount of sections of the net did not allow to distinguish microlithotypes, among which there was only possibility to observe vitrite as `observed` microlitothype.

A Comprehensive Study of Effect of Maceral Content on Tendency of Spontaneous Coal Combustion Occurrence

Coal mining has many serious hazards, and the spontaneous combustion phenomenon is one of them. Many factors can influence the tendency for occurrence of this phenomenon. The maceral content is one of the coal inherent characteristics, which has a crucial aspect in the occurrence of this process. Until now, this parameter has not been discussed in a comprehensive study by the scientists. Thus a final conclusion about the effect of maceral content on spontaneous coal combustion is required. Maceral content is directly affected by the growth of coalification and origin of coal formation. This study aimed at developing a new statistical model for predicting the spontaneous coal combustion tendency based on the maceral content. In this work, firstly, 51 coal samples with a variety of maceral contents were collected for training data of the overall underground coal fields in Iran, and the Crossing Point Temperature (CPT) test was carried out on each coal sample. Then the method of regression analysis was used for modeling and predicting the spontaneous coal combustion tendency. For validation and testing, 11 coal samples of another coalfield were collected, the CPT test was carried out on each one of them, and the results obtained were compared using the regression equation. Validation of the developed model was checked by the F test. By examining the experimental results and comparing the CPT test values, it was found that with increase in the vitrinite and liptinite contents and decrease in the inertinite content, the coal samples displayed a higher tendency for spontaneous combustion. The results also showed that the spontaneous combustion tendency could be reliably predicted using the proposed model.

Petrology and palynology of select coal samples from the Permian Waterberg Coalfield, South Africa

The petrology and palynology of coals from the Permian-aged Waterberg Coalfield, situated in the Limpopo Province of South Africa, are considered. The Waterberg Coalfield contains a significant portion of the country's coal reserves, but is still comparatively underexplored. Detailed maceral analyses, combined maceral-microlithotype analyses, mean random and maximum vitrinite reflectance analyses, etching, and palynology studies were undertaken on coals from four productive horizons. There is a general upward trend in vitrinite content through the sequence (15–59 vol% mineral matter free), dominated by collotelinite, along with a slight decrease in coal rank. The lower Vryheid Formation coal has a comparatively low mineral matter and high inertinite content, dominated by inertodetrinite. The upper Grootegeluk Formation samples contain above 35 vol% mineral matter, and liptinite contents ranging from 14 to 21 vol%. The use of blue-light fluorescence in conjunction with incident light (single-scan method) revealed that liptinite is intimately associated with inertodetrinite and mineral matter, specifically clays and occasionally pyrite. It is evident that the liptinite maceral content has previously been under-reported in the Waterberg coals. The palynofloras correlate with the well-studied Witbank Coalfield. The petrography, along with the palynology, essentially confirm the palaeoenvironment of the Karoo Basin as progressing from a cooler, more oxidising environment, to a wetter, seasonal environment.

Evaluation effect of macerals petrographic and pyrite contents on spontaneous coal combustion in Tabas Parvadeh and Eastern Alborz coal mines in Iran

ABSTRACT Among the fossil fuels, coal is the most widely used one all over the world for different purposes and is a stable source of energy. Coal mining has serious hazards such as spontaneous combustion. Many factors can influence the tendency for occurrence of this phenomenon in coal mines and coal storages, one of which is the petrographic characteristics (maceral and pyrite contents). The petrographic characteristics are directly affected by the growth of coalification and origin of coal forming. In this research work, firstly, the maceral and pyrite contents in coal samples were identified in two various mines in Iran (Tabas Parvadeh and Eastern Alborz coal mines). Then the spontaneous coal combustion propensity of each sample was measured using the Crossing Point Temperature (CPT) test method. The aim for carrying out this research work was to measure the effect of the maceral and pyrite contents on the grade of spontaneous coal combustion propensity. It was found that the pyrite contents and the vitrinite, liptinite, and inertinite mean levels in the Tabas Parvadeh and Eastern Alborz coal mines were (2.08%, 53.30%, 9.91%, 34.71%) and (1.14%, 53.06%, 6.39%, 39.41%), respectively. The mean CPT value was 148.43ºC in the Tabas Parvadeh coal mines and 175.86ºC in the Eastern Alborz coal mines. By examining the results of the experiments and comparing the CPT values, it was found that with an increase in the liptinite and pyrite contents and a decrease in the inertinite content, the Tabas Parvadeh coal mines tend to have more tendency for spontaneous coal combustion in comparison with the Eastern Alborz coal mines.

Environment of paleomire of lignite seams of Bikaner-Nagaur basin, Rajasthan (W. India): petrological implications

Petrological and chemical investigations of lignites from the Bikaner-Nagaur Basin, Rajasthan (Western India) have been undertaken to understand their petrographic characteristics and the paleomire. The huminite reflectance (VRr) (0.21-0.26%) put these lignites as 'low rank C' coals. Huminite is the most abundant maceral group which is dominated by detrohuminite (densinite and attrinite). Telohuminite (chiefly ulminite-A and ulminite-B) occurs next in abundance. Liptinite and inertinite occur in subordinated amount. High GI and low TPI values indicate a continuous wet condition in the basin with a slow rate of subsidence. However, Gurha lignites, suffered few spell of relatively drier period as revealed by increased inertinite content in few bands. The study indicates a limno-telmatic swamp and a slow fall in ground water table. Petrography based models suggest a wet moor condition having a moderate flooding with increasing bacterial activity that prevailed under coastal-marshy setting during the transgressive phase. [Received: February 18, 2017; Accepted: September 21, 2017]

Gas sorption capacity, gas sorption rates and nanoporosity in coals

Bituminous coals from a wide range of sources (including Australia, New Zealand, Europe, China, South America, Canada, the US and South Africa) were characterised by their capacity for gas sorption, rate of gas sorption of CO2 and CH4, and their nanoporosity (pore size distribution less than 50 nm radius) in order to identify the relationships between them. The following new relationships were established:The rate of gas sorption was unrelated to the capacity for gas sorption. The rate of gas sorption for CH4 and CO2 increased exponentially with the amount of total and accessible porosity in the size range 8–50 nm (with no influence of coal origin on the relationship being discerned), suggesting that the extent of porosity of coals in this size range controls the rates of gas sorption in coals. In contrast, the capacity for gas sorption was only weakly related to pore numbers in this size range, which shows that the number of 8–50 nm pores do not control capacity for gas sorption. Moreover, this difference in relationship shows the number of pores of the size where gas is sorbed predominantly (<5 nm) does not correlate strongly with the number of larger pores.Both the number of pores and rates of gas sorption tended to increase with inertinite content but the relationship with inertinite content differed for coals from different sources. The inertinite-rich coals from Australia (except those from the Illawarra region) had both the greatest porosity and gas penetration rates, whereas in coals sourced from other regions, although the gas penetration rate increased with inertinite content, the effect was not so strong. The rates of sorption in the inertinite-rich coals also tended to decrease with increasing rank below 0.9% Rv,max. In contrast to the results obtained with kinetic studies, we found no overall trend of capacity for gas sorption with maceral composition, though the Australian bituminous coals generally had greater capacity than the other bituminous coals examined. This suggests that not only the number of 8–50 nm pores in coals sourced from Australia (not those from the Illawarra region) and elsewhere are different, the number density of accessible <5 nm pores (not directly measurable in coals by SANS) may also be systematically different between these coals.The relationships developed in this study have important implications in predicting coal structure, fundamental understanding of gas transport through coal beds, and explaining the variation of coking properties of coals sourced from Australia and elsewhere.

Full-size pore structure characterization of deep-buried coals and its impact on methane adsorption capacity: A case study of the Shihezi Formation coals from the Panji Deep Area in Huainan Coalfield, Southern North China

The characteristics and influence on methane adsorption capacity of the pore structure of coals was investigated through an approach that integrates mercury intrusion porosimetry, low pressure N2/CO2 adsorption, and field emission scanning electron microscopy. Shihezi Formation coal samples from the Panji Deep Area in Huainan Coalfield in Southern North China were adopted as the study subjects. The fractal features of heterogeneous coal pore structures were quantified on the basis of N2 adsorption isotherms by using the Frenkel−Halesy−Hill (FHH) model. Pore structure and morphology characterizations confirm that Shihezi Formation coals developed with multiple pore types and heterogeneous pore structures, and the slit-shaped and ink-bottle-shaped pores are mainly distributed at the pore size interval of 3.3–10 nm. Our coal samples present uni-modal and multi-modal pore size distributions, wherein multiple peaks are concentrated in the intervals of 0.45–0.55 nm and 2–20 μm. The major volumes from mesopores (2 nm < pore diameter < 50 nm) and macropores (pore diameter > 50 nm) occur in the full-scale pore size distributions, revealing Shihezi Formation coals are mesopores and macropores rich. Micropores (pore diameter < 2 nm) provide the majority of pore specific surface area, whereas pore volume is mostly contributed by mesopores and macropores. The volumes and specific surface areas of mesopores and macropores are positively correlated with ash yield and inertinite contents but are negatively correlated with maximum vitrinite reflectance (Ro,max). The methane adsorption capacity of Shihezi Formation coals is largely independent of mesopores and macropores but is positively correlated with the pore volume and specific surface area of micropores. This correlation suggests that micropores provide the predominant sites for methane adsorption. The calculated values of pore surface fractal dimension D1 and spatial fractal dimension D2 are 2.440–2.610 (avg. 2.515) and 2.542–2.761 (avg. 2.650), respectively, suggesting that the pore structures of Shihezi Formation coals are highly complex and heterogeneous. The positive correlation between D1 and methane adsorption capacity reveals that high surface roughness of the pore structure is associated with high methane adsorption capacity. However, the irregular pore structure does not influence methane adsorption capacity.

Depositional environment and characteristics of Late Eocene carbonaceous swampy tidal flat facies in the Fayoum Basin, Egypt

This study addresses the stratigraphic and sedimentological characteristics of the Late Eocene carbonaceous shale-bearing Qasr El Sagha Formation in the Fayoum Basin, Egypt. The Qasr El Sagha succession is comprised of four facies types: coastal mudflat, tidal flat, swamp, and storm-affected tidal channels. The swamp facies contain the Fayoum carbonaceous shale facies, which have not been studied in the past. The present study reports the first publicly available sedimentological, palynological, and geochemical results for the Fayoum facies. Eight samples of the sequence were taken from a freshly exposed road cut and analyzed petrographically, geochemically, and palynologically in order to determine the paleoenvironment of deposition and prevailing conditions. The palynomorph assemblages show that the lower part of the sequence was deposited in a lowland-riparian environment with continued freshwater influx. The depositional regime in the upper part of the sequence was swampy and dominated by fresh water. Mixed angiosperms and pteridophytes dominated the woody forest vegetation and were the source for the formation of the Fayoum carbonaceous shale facies. The recovered palynomorph assemblage points to the prevalence of a tropical to a sub-tropical, warm, humid climate with heavy precipitation in the lowland, swampy areas that were in close proximity to the freshwater influx. The water table was above the fen surface, preventing oxidation of the vegetation. Intermittent flooding or fluctuation in paleo-water levels likely occurred in the peat paleo-mire. The Fayoum samples have Ro,ran values of ~0.40–0.50%, which is in very good agreement with the Tmax from Rock-Eval pyrolysis. Although a few of the samples have elevated S2 (15–24 mg HC/g rock) and HI values (125–140 mg HC/g TOC), they do not have any hydrocarbon generating potential in the sampled location as a result of their immaturity. Petrographically, the analyzed samples are dominated by huminite group macerals (up to 77%), with telohuminite (eu-eulminite B) being dominant. Liptinite content is up to 3.5%, whereas inertinite content is up to 6%, dominated by fungal sclerotia (funginite). The TOC of the facies samples does not exceed 40 wt%.

Effect of multi-intensification on the liberation of maceral components in coal

In order to achieve high-quality coal resources in western China, this study focused on a coal sample from the Shangwan Coal Mine, owned by the China Shendong Group, and employed scanning electron microscopy (SEM), mineral liberation analysis (MLA), and maceral component quantitative analysis for investigating the coal sample’s liberation characteristics and crack distribution patterns after pre-grading and microwave processing. The results show that the physical properties of coal maceral components significantly affected the related enrichment performances, and many intra-group and inter-group cracks were produced under the induction of microwave radiation. The cracks then developed and stopped growing among the different maceral components and mineral components, thereby inducing selective and random pulverization along the crack growth direction in further pulverization process and effectively enhancing the liberation properties of different components. Using the Sandbox method, the fractal dimension of the cracks on the particle surface was calculated to be 1.01, which confirmed the self-similarity of the cracks on the coal surface. Multi-intensification maceral liberation also yielded favorable grading performances. The inertinite content was the highest (75.23%) in grade-3 product, while the vitrinite content was the highest (66.3%) in grade-1 product; the corresponding enrichment ratios were 2.15 and 1.59, respectively. Moreover, the ash content in grade-2 product was the lowest, which dropped by 3.61% compared with that in raw coal sample.

Study on the structural differences between Heidaigou long flame coal and its vitrinite

ABSTRACTHeidaigou long flame coal (HDC), with high inertinite content but outstanding liquefaction properties and its vitrinite (HDV) were studied. The structural characteristics of HDC and HDV were studied simultaneously on the basis of structure models developed by 13C cross-polarization/magic angle spinning nuclear magnetic resonance (NMR) and X-ray photoelectron spectroscopy (XPS). Aliphatic structures, aromatic structures, and the structures of nitrogen and oxygen in HDC and HDV were investigated and compared. Besides, the different structures and units in HDC and HDV were found and represented.

Characterization of pore structure and its impact on methane adsorption capacity for semi-anthracite in Shizhuangnan Block, Qinshui Basin

To determine the pore structure characteristics and its effect on the adsorption capacity of semi-anthracite, high pressure mercury injection (HPMI), Low pressure nitrogen gas adsorption (LP-N2GA), Low pressure carbon dioxide gas adsorption (LP-CO2GA) and isotherm adsorption experiments were carried out on eight coal samples collected from the Shizhuangnan Block. The results show that the semi-anthracite reservoirs predominantly developed semi-open pores with poor connectivity and various pore morphology. The combined pore size distribution (PSD) from results of HPMI, LP-N2GA and LP-CO2GA indicated that the super-micropores in semi-anthracite reservoirs are most developed, providing the main storage space, accounting for 80.75% of the total TPV and 99.69% of the total SSA, followed by macropores. Additionally, the pore volume and SSA distributions of semi-anthracite reservoirs are unimodal with peak values present at 0.5–0.6 nm, indicating that pores with pore diameter between 0.5 and 0.6 nm are the largest contributors to TPV and SSA, accounting for 40.09% of the TPV and 56.95% of the total SSA. The super-micropores have a controlling factor on the adsorption capacity of semi-anthracite reservoirs. Vitrinite-rich coals developed stronger adsorption capacity as the vitrinite is rich in super-micropores whereas there are no obvious correlations between inertinite content with super-micropore SSA and VL. Additionally, mineral has a negative effect on the adsorption capacity of coals by inhibiting the development level of super-micropores. The combination application of HPMI, LP-N2GA and LP-CO2GA can more accurately reflect the pore structure of coal reservoir, especially for super-micropores.

Petrographic and chemical reactivity assessment of Indian high ash coal with different biomass in fluidized bed co-gasification

The reactivity of coal and biomass has been evaluated by comparing the optical and chemical changes in feed material prior and after the co-gasification. The proximate, ultimate, GCV, low-pressure N2 sorption isotherm, micropetrography, SEM and EDX spectroscopy analyses are carried out to assess the reactivity of blends of high ash Indian coal and biomass. The relative changes in parameters like surface area, pore size, and pore volume have been correlated with reacted percentage area of coal macerals and cellulose-lignin cellular structures of biomass. The Optimas image processing software is being used to mark the reacted portion of organic constituents and calculated the reactivity percentage. The bottom ash of pure coal has shown the least reacted organic matters, indicating inefficiency of high ash coal due to a large amount of inorganic and inertinite contents that is resisting the oxidation. The reactivity percentage is determined by the petrographic and SEM images, and varies from 36.34 to 99.64% and 6.61–96.22%, respectively. It is summarised that the estimation of percentage alteration of macerals and other micro-organic constituents can be used as one of the practical approaches for the assessment of the reactivity of coal and biomass. The blending ratio 6:4 of coal and press mud has shown the highest reactivity (>99.64%). The values of petrographic and SEM reactivity have shown good correlations with the carbon contents, unreacted vitrinites, mineral matters and biomass remnants. These relations have been taken into account to formulate the proposed petrographic empirically calculated reactivity (RPEC). The focus has also been made to investigate the influence of feed composition on carbon conversion and heating value of the product gas.

Methane adsorption characteristics and its influencing factors of the medium-to-high rank coals in the Anyang-Hebi coalfield, northern China

The variation of coal rank in the Anyang-Hebi (Anhe) coalfield has the phenomenon of anti-Hilt law, which makes the coalfield distinctive for coalbed methane exploration research. The methane adsorption characteristics and influencing factors of the medium-to-high rank coal samples of the Shanxi Formation in this coalfield were analyzed. The results indicate that the Langmuir volume ( VL) of coals in the shallow western part of the Anhe coalfield is generally higher than that in the deep eastern part. The coal rank and the coal macerals are the dominant factors that influence the methane adsorption capacity of coals in this anti-Hilt law area. The methane adsorption capacity, represented by VL, first increases and then decreases with the coal rank, and the highest VL value corresponds to the maximum vitrinite reflectance of ∼2.1%. The adsorption capacity has a positive correlation with the vitrinite and the moisture content, a negative relationship with the inertinite content. In general, the adsorption capacity of coal samples shows a “V-shaped” change with the ash yield, and the lowest VL value corresponds to the ash yield of ∼9%. A prediction model of the gas content of the Anhe coalfield was proposed based on changes of the methane adsorption capacity and principal component analysis. Areas with a critical depth ranging from 400 m to 700 m are suggested to be methane enrichment regions for coalbed methane exploration in the Anhe coalfield.

Relationship between Maceral of Coal and Coal-bed Methane adsorption ability in Sihe Coalmine of Qinshui Basin, China

Maceral components and its content of coal were divided based on the microscopic characteristics of coal. The Langmuir volume and the Langmuir pressure were tested, and the Langmuir volume represents the adsorption capacity of coal. The formation of coal bed methane is affected by the partition of the maceral components in coal. Therefore, the relationship between maceral composition and coal bed methane adsorption capacity of coal was analyzed. The results show that the maceral components of coal are dominated by vitrinite and inertinite in the study area, and the content of inertinite is below 32%. The vitrinite group has a negative linear correlation with the Langmuir volume, and the inertia composition has a positive linear correlation with it. The cellular structures in the inertinite are the main site of coal bed methane enrichment. The microstructure of coal affects the coalbed methane content and the stage of hydrocarbon generation in coal. This indicates that the microstructure of coal is one of the important factors influencing the adsorption capacity of coal seam.

Processing Nigerian coal deposits for energy source

Some coal deposits in Nigeria were assessed through geochemical Rock Eval pyrolysis, organic petrology and combustibility studies to characterize them and to determine their suitability as an energy source. The following correlations were obtained. Rock Eval hydrogen indices (HI) correlate proportionally with the petrographical liptinite content; oxygen indices (OI) correlate proportionally with the combustibility time and with the petrographical inertinite content (made up mainly of fusinite). The coals with higher values of OI correlating with high inertinite content produce more visible smoke during combustion, while those with lower OI and higher liptinite content produce less visible smoke (smoke perception). The Okaba coal deposits in the Northern Anambra Basin contain higher values of HI, lowest values of OI and inertinite content and correspondingly had the shortest combustibility time. It also has very little visible smoke and assumed to be the most suitable for smokeless fuel production and electrical energy generation. Using theses parameters to characterize the other coals, the Owukpa and Omelehu come next as a good coal energy source. The Ogboyaga coals have relatively high OI and inertinite contents; it produced the most visible smoke. The Lafia-Obi coals with high inertinite content took the longest time to bring the same volume of water to boiling point, compared to the other coals. Defusinization experiments in which samples were digested with eight types of organic acids gave results that show that Benzoic and Formic acids can be used to clean the coals (to some extent) to make them more suitable as environmental-friendly energy source.