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The distribution of the various organic and inorganic constituents and their influences on the combustion of coal has been comprehensively studied. However, the combustion characteristics of pulverized coal depend not only on rank but also on the composition, distribution, and combination of the macerals. Unlike the proximate and ultimate analyses, determining the macerals in coal involves the use of sophisticated microscopic instrumentation and expertise. In this study, an attempt was made to predict the amount of macerals (vitrinite, inertinite, and liptinite) and total mineral matter from the Witbank Coalfields samples using the multiple input single output white-box artificial neural network (MISOWB-ANN), gene expression programming (GEP), multiple linear regression (MLR), and multiple nonlinear regression (MNLR). The predictive models obtained from the multiple soft computing models adopted are contrasted with one another using difference, efficiency, and composite statistical indicators to examine the appropriateness of the models. The MISOWB-ANN provides a more reliable predictive model than the other three models with the lowest difference and highest efficiency and composite statistical indicators.

Previous studies demonstrated that melting, initiated by supercritical fluids in the 375–400 °C range, occurred as part of anthracite metamorphism in the Appalachian Basin. Based on the known behavior of vitrinite at high temperatures and, to a lesser extent, at high pressures, it was determined that the duration of the heating, melting, and resolidification event was about 1 h. In the current study, featureless vitrinite within banded maceral assemblages demonstratesthe intimate association of melted and resolidified vitrinite with anthracite-rank macerals. By analogy with metamorphosed inorganic rocks, such associations represent diadysites and embrechites, i.e., cross-cutting and layered migmatites, respectively. Even though the temperature of formation of the anthracite structures is several hundred °C lower than that seen in metamorphosed inorganic rocks, anthracites are metamorphic rocks and the nomenclature for metamorphic rocks may be appropriate for coal.

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.

The Chichali Formation encountered in Chanda 01 well, located in the Shakardara Kohat, Khyber Pakhtunkhwa Province of Pakistan has been studied in detail as a source for hydrocarbon. Nine drill cuttings of the formation were subjected to geochemical analyses and organic petrography. Various screening techniques including TOC analysis by using Leco-CS analyzer, Rock Eval pyrolysis and organic petrography were used to determine the quality, quantity, maturity and depositional environment of the organic matter. The total organic carbon (TOC) of samples from Chichali Formation ranging from 0.47 to 2.76 wt% indicate fair to very good source rock. Pyrolysis parameters resulted in S1values ranging from 0.21 to 0.83 mg/g of rock, S2 0.44 to 0.61 mg/g rock, PI 0.32–0.51 and Tmax 442–448 °C. The Tmax and vitrinite reflectance data (0.72–0.84 Ro %) indicate that Chichali Formation is effective source rock and is in the process of generating hydrocarbons and falls within oil window. Geochemical parameters Hydrogen index (HI), Oxygen index (OI), Tmax along with organic petrography analyses (maceral) are used for kerogen type evaluation. The calculated HI ranges between 31 and 54 mg HC/g TOC and OI 30–96 mg O2/g TOC. Using modified Van Krevlen diagram between HI vs OI of Rock Eval pyrolysis and maceral analyses, kerogen type II/III and transition between anoxic to oxic depositional environments is interpreted for the studied Chichali Formation.

Upper Jurassic Naokelekan Formation, being part of the intercepted strata of the well-known Miran oilfield in Kurdistan region of Northern Iraq, has been previously extensively evaluated as a potential/effective source rock, mainly by means of organic geochemistry. In the present study, a total of 60 samples were collected from four Naokelekan Fm. outcrops, those of Banik, Galy-Derash, Barsarin and Dwawa, in order to conduct organic petrographical study and organic geochemical assessment, including both biomarker and Rock-Eval analyses. The average recorded TOC content for Banik, Galy-Derash, Barsarin and Dwawa section is considerable to very high, corresponding to values of 27.5, 9.0, 3.5 and 5.2 wt%, respectively, with the highest values representing the notably organic-rich bottom part of the Formation, known as “coal layer”. According to the petrographical analysis, solid migrabitumens comprise the predominant component for all the analysed samples, whereas the maceral groups of vitrinite, liptinite and/or inertinite showcase a minor to trace occurrence. In terms of organic geochemistry, each of the four sections of interest shows a different biomarker profile. Nevertheless, a number of calculated parameters related to kerogen type and depositional conditions, including the isoprenoids/n-alkanes ratios, suggest a mixed terrestrial-marine organic matter. Furthermore, as indicated by the Ro (%) measurements along with Rock-Eval parameters and the vitrinite reflectance equivalent based on aromatic compounds, the maturity level is marginally mature in the cases of Banik and Galy-Derash, whereas in the cases of Dwawa and Barsarin sections it is mature to post-mature. A synthesis of the organic petrography and geochemical appraisal applied in the present study, suggests that the reported solid hydrocarbons in Naokelekan Fm., particularly at its basal layers are non-indigenous/migrated and the precursor organic matter was deposited in a marine environment, under oscillating conditions ranging from euxinic to well‑oxygenated. Accordingly, the organic features of the notably bitumen-rich “coal-bed” fit the profile of a reservoir and/or migration path., This research was supported by the University of Patras, Greece, the University of Soran, KRG-Iraq, INCAR, Spain, as well as from EU Erasmus + Programme.

High volatile bituminous coal C and B is currently exploited at Spitsbergen-Svalbard, Norway. Several coal seams formed during the Palaeocene, of which some were reworked by mass wasting (MW), (glacial)-fluvial (GF) and coastal-marine wave-dominated (WM) processes under periglacial conditions during the Quaternary. This supergene alteration resulted in different landforms and deposit bearing four different types of depositional environments in Svalbard: (1) Invisible floral and faunal remains, (2) visible floral remains, (3) drift wood, (4) coal placers s. The subaerial slow- and fast-moving MW was accompanied by chemical weathering giving rise to jarosite coatings indicative of acidic meteoric solutions, whereas the remaining subaquatic processes operated under neutral to slightly alkaline conditions. Fast-moving MW and WM are productive processes, whereas GF ones are destructive with regard to coal accumulation. The most efficient tools to study the origin of the OM-bearing coarse-grained deposits are the morphology and orientation of bioclasts while the LER/HER (= low exothermic / high exothermic reaction) ratio is used for finer-grained OM-bearing sediments. The maceral analysis revealed that the landforms accounted for by GF and WM were emplaced as a result of geogenic and anthropogenic processes and aged younger than 1900 CE, while MW is Quaternary and true geogenic. Driftwood is cast in the role of a marker for coal-bearing (fluvial-) marine environments different in age and rank of coalification. With this in mind it is an excellent tool to drawn the boundary in paralic settings between the marine and fluvial impact. In conclusion, coal fragments are markers for short-term, periodical and fast landform-building processes, whereas siliciclasts from the host and bedrock are markers for long-term and episodical geomorphological and sedimentological supergene alteration.

Drilled core samples of the Araromi Formation in the eastern Dahomey basin penetrated by Araromi and Gbekebo exploratory wells were investigated to establish the source rocks potentials in the onshore area of the basin. The sediments are of Maastrichtian age deposited in the shallow marine environment with varying thicknesses. Rock-Eval data of forty seven (40) shales give Total Organic Carbon (TOC) range of 0.50–4.78 wt%, Hydrogen Index (HI) value range of 1 - 327mgHC/gTOC, Tmax values from 398 °C–437 °C and Source Potential (SP) values range from 0.01 - 14.56kgHC/ton of rock. The maceral compositions of the shales are liptinite (av. 26.0%), abundance vitrinite (av. 38.1%) and inertinite (av. 35.9 %) with vitrinite reflectance (VRo) ranging from 0.51 - 0.68 %Ro. Hydrocarbons and biomarkers results reveal a bimodal n-alkane envelope between (nC16 and nC18) and (nC27 and nC29) suggesting organic matter of mixed origin of algae and higher plant generally in the two well. The Significant contribution of marine algae in the deeper part of Gbekebo well was observed by the presence of C30 24-n-propyl cholestane (%C30 sterane range from 0.45 to as high as 5.23%). Integration of the Rock-Eval, organic petrology and biomarkers data reveal that the kerogen constituents of the source rocks in Araromi well are mainly Type II/III, III and IV with a high amount of inertinite constituents suggesting they have been reworked. Type II and II/III kerogen derived from marine algae are better preserved in the deeper part of Gbekebo well located more southerly in the basin than in the Araromi well. The source rocks are generally immature to marginally mature and hydrocarbon exploration effort should be targeted towards Gbekebo well area where we have more promising potential source rocks capable of generating more hydrocarbons essentially at a deeper depth.

The gas permeability of coal varies due to the comprehensive effects of effective stress increase, coal matrix shrinkage, gas slippage, and Knudsen diffusion during gas pressure depletion. In this chapter, a model was established to predict the adsorbing-gas (CO2) permeability change by coupling pore size evolution with the permeability change during gas pressure depletion. Two parameters (change ratio of permeability and total loss of flow rate) were proposed to quantitatively evaluate the dynamic process of CO2 flow in different coal ranks. Furthermore, the effects of the maceral composition and initial permeability of coal on the dynamic gas flow were observed. The total loss of flow rate is positively related to the change ratio of permeability and decreases with increasing coal rank from high volatile bituminous to semianthracite coal but increases in anthracite coal. In different coal ranks, the total loss of flow rate and change ratio of permeability are comprehensively affected by the maceral composition and initial permeability of the coal, of which the maceral composition primarily affects the total loss of flow rate and change ratio of permeability changes in bituminous and semianthracite coals. The initial permeability dominates the changes in the total loss of flow rate and change ratio of permeability as coal rank varies from semianthracite to anthracite coal. For the same rank, coals (especially some bituminous and anthracite coals) with lower and higher initial permeabilities have smaller values of total loss of flow rate and change ratio of permeability.

A Pleistocene coastal lignite outcropping between the Muândeje Lake (Maputo Province)and Nhachuendezo Lake (Gaza Province)was recognized during geological mapping performed in 2009. However, these outcrops started to be investigated only in 2017 through paleontological fieldwork under the PaleoMoz Project (www.paleomoz.org). Here the chemical and petrographic compositions of a coal sample from this locality are reported. This new occurrence represents the first lignite occurrence from coastal Mozambique. The lignite is a Low Rank C (Lignite C)coal with a huminite reflectance of 0.248%. The results show that the lignite has high ash yield (46.5%, d); volatile matter (65.2%, daf), carbon (57.3%, daf), hydrogen (5.3%, daf)and nitrogen (2.3%, daf)contents are according to the rank of this coal; and, low total sulphur (1.8%, d). The coal is richer in huminite (86%)than liptinite (10%)and inertinite (4%). The maceral analysis indicates that lignite's peat precursor derived mainly from herbaceous plants and Botryococcus algae deposited in a topogenous mire (fen)under mesotrophic anoxic conditions. The water level remained above the paleomire's surface., This work was developed under the auspices of PaleoMoz Project (funded by Museu Nacional de Geologia, Programa Aga-Khan/Fundação para a Ciência e Tecnologia and National Geographic Society Standard Grant CP-109R-17). RA would additionally like to acknowledge additional funding through Fundação para a Ciência e a Tecnologia (SFRH/BPD/96205/2013). D. Flores acknowledges the funding provided by the Instituto de Ciências da Terra, Polo Universidade do Porto, through the contracts UID/GEO/04683/2013

Central Tertiary Basin (CTB) coals from a variety of palaeogeographic conditions within the Longyear and Verkhnij seams, were sampled to assess the relationship between the petroleum present, the remaining generation potential and coal geochemistry in order to improve the spatial predictability of petroleum resources within the basin. Vitrinite reflectance (VR) values from the CTB coals have been shown to be suppressed (Marshall et al., 2015b). This study attempts to quantify and correct for this suppression effect by applying the Lo (1993) method (LoVR), which uses Hydrogen Index (HI) values to modify VR data, and the coal Rank(Sr) scale of Suggate (2000, 2002), a technique not affected by suppression. In addition, the oil generation and expulsion thresholds for the CTB coals were investigated, with discussions on oil potential versus marine influence upon the mires in which the coals formed. A pseudo-van Krevelen diagram shows that the majority of the coals plot on the Type II kerogen line, while the remainder plot between the Types II and III kerogen lines, with HI between 151 and 410 mg HC/g TOC; however, maceral analysis shows that Type III kerogen predominates. This is attributed to the presence of abundant fluorescing (oil-prone) vitrinites. The LoVR, Tmax and Rank(Sr) parameters all show that maturity increases from basin margins towards basin centre (i.e. from Bassen to Lunckefjellet, to Breinosa and Colesdalen) and indicate that all the coals are within the oil generation window. The marginal samples at Bassen are within the early mature stage of the oil window (i.e. ~ 0.7% RO); meaning the threshold for oil generation in the basin could not be clearly defined. However, the observed maturation trend somewhat parallels the maturation pathway of the New Zealand Coal Band (NZ Coal Band) and the “envelope” of the Sykes and Snowdon (2002) NZ coal data-set; therefore, it is considered that the oil generation threshold for the CTB coals is likely at Rank(Sr) ~ 9–10, Tmax ~ 420–430 °C in line with the observed rise in Bitumen Index (BI). Some of the Lunckefjellet coals and all the Breinosa and Colesdalen coals have either reached or progressed beyond the threshold for oil expulsion as indicated by the peak in HI at Rank(Sr) ~ 11–12, LoVR ~ 0.75–0.85% RO, Tmax ~ 430–440 °C. The peak in BI at Rank(Sr) ~ 12.5–13.5 suggests that some of the Lunckefjellet and Breinosa coals, and all the Colesdalen coals have reached the “effective oil window”. Total sulphur (ST) contents range between 0.46 and 12.05% indicating non-marine to strong marine influence upon precursor peats, with ST contents of the Longyear seam appearing to record instances of coastal retreat associated with base level rise. Marine deposition seems to significantly control the distribution of oil-prone coals within seams and across the CTB. The levels of marine influence (as indicated by ST content) show clear positive relationships between BI and HI within the Bassen samples because they have not started expelling oil. Conversely, the levels of marine influence show clear negative relationships with BI and HI within the Colesdalen samples because they have commenced oil expulsion, and probably reached the “effective oil window”. The more marine influenced coals appear to have commenced petroleum generation relatively earlier, which is a plausible explanation why the coals from the Lunckefjellet locality appear to be at different stages within the oil window.

Shale gas can either exist in the free state in natural fractures and intergranular pores, an adsorbed state on organic maceral or clay particle surfaces, or a dissolved state in fluid. This chapter covers a study carried out on the modes of occurrence and characteristics of lacustrine shale gas based on laboratory test analysis data, in order to estimate the gas content of every state by well-logging and gas reservoir engineering (using the PVT equation of state method).

This chapter presents a comprehensive review of the effects of the physical and chemical properties of coal on the gasification process. These include coal reactivity (rank, macerals, porosity, surface area, mineral matter contents, etc.); ash and slag properties (mineral matter transformation, ash fusibility, slag viscosity, ash agglomeration, fouling, clinkering, etc.); coal particle size and fragmentation; and caking and swelling. Different considerations, such as gasifier types, syngas compositions and ash-related problems during gasification are also discussed. Moreover, methods for preventing ash-related problems during gasification are summarized.

Poland is considered the most prospective country for shale gas production in Europe. Hydrocarbon generation/expulsion scenarios, drawn in the latest intensive exploration phases, tend to overestimate maturation levels when compared with brand new data acquired after recent drillings. We tested an integrated workflow to correlate published and original thermal maturity datasets for the Paleozoic to Jurassic successions cropping out in the Holy Cross Mountains. These successions, when preserved in subsurface, host the major source rocks in the area. The application of the workflow allowed us to highlight the burial and thermal evolutionary scenarios of the two tectono-stratigraphic blocks of the Holy Cross Mountains (Łysogory and Kielce blocks) and to propose this approach as a tool for reducing levels of uncertainty in thermal maturity assessment of Paleozoic successions worldwide. In particular, published datasets including colour alteration indexes of Paleozoic microfossils (conodont, acritarchs) and vitrinite and graptolite reflectance data, show differences in levels of thermal maturity for the Łysogory (mid mature to overmature) and Kielce (immature to late mature) blocks. Original data, derived from optical analysis, pyrolysis, and Raman spectroscopy on kerogen, and X-Ray diffraction on fine-grained sediments, mostly confirm and integrate published data distribution. 1D thermal models, constrained by these data, show burial and exhumation events of different magnitude, during the Late Cretaceous, for the Łysogory (maximum burial depths of 9 km) and Kielce (burial depths of 6 km) blocks that have been related to the Holy Cross Fault polyphase activity. In the end, Palynomorph Darkness Index and Raman spectroscopy on kerogen, for Llandoverian and Cambrian rocks, turned out to be promising tools for assessing thermal maturity of Paleozoic organic facies devoid of vitrinite macerals.

a b s t r a c t A new technique that allows dynamic measurement of thermal properties, expansion and the elemental chemistry of the volatile matter being evolved as coal is pyrolysed is described. The thermal and other properties are measured dynamically as a function of temperature of the coal without the need for equilibration at temperature. In particular, the technique allows for continuous elemental characterisation of tars as they are evolved during pyrolysis and afterwards as a function of boiling point. The technique is demonstrated by measuring the properties of maceral concentrates from a coal. The variation in heats of reaction, thermal conductivity and expansion as a function of maceral composition is described. Combined with the elemental analysis, the results aid in the interpretation of the chemical processes contributing to the physical and thermal behaviour of the coal during pyrolysis. Potential applications in cokemaking studies are discussed.

This study deals with the palaeohydrological information obtained from lipids composition and vegetal tissue preservation of two peat cores from Asturias, North Spain. The two profiles differ in the type of peatland (raised bog in La Borbolla and blanket bog in Buelna) and the type of organic matter being more bryophytic in the raised bog and more herbaceous in the blanket bog. The peatlands are located close to the coast on impermeable, old flat erosion surfaces which favoured peat accumulation within a distance of 3.5 km from each other. The accumulation rate varied between 0.05 and 0.07 mm/yr and the records extend from around 9000 to 2500 cal. yr BP. The main differences between the two peat sites can be summarized as follows: the raised bog has lower mineral matter content and H/C atomic ratio and higher C/N ratio and extraction yields compared to the blanket bog. It has also a higher Tissue Preservation Index for Huminite macerals and increasing Inertodetrinite Index with depth. Regarding biomarkers, the raised bog has a relatively higher concentration of n-alkane-2-ones compared to the corresponding n-alkane of similar carbon number, higher concentration of medium- vs. high-molecular-weight-methyl-ketones and higher triterpenoids/steroids ratio than the blanket bog. Alternating humid/dry periods have been recorded in both profiles based on lipid concentrations indicating that the Sphagnum-rich intervals in the raised bog are more sensitive than the herbaceous blanket peat record to climatic variations. The main humid intervals identified are dated as 5000–7500 cal. yr BP in the blanket bog and as 6000–3500 cal. yr BP and last 2500 cal. yr BP in the raised bog and correlate with the humid periods traced in other peatlands locations in this region. The transition Middle-to-Late Holocene is characterized by humid conditions in the region which favoured the Sphagnum growth in the peats. The reflectance of huminite in these records appears to be more related with differences in the oxidative conditions than with variation of peat maturity. It is higher in the layers with high mineral matter content at the beginning of organic matter accumulation and also in the upper part of the profile subjected to seasonal desiccation. A more intense biochemical gelification coincides with higher concentration of hopanoids derived from bacteria in the upper part of the profile (acrotelm). High amount of nonadecan-2-one (K19) and high concentrations of triterpenyl acetates, which are also determined in other peat profiles from Northern Spain are also detected in these profiles. This indicates that the specific conditions required for the formation of these compounds, probably associated to wet temperate climate, dominated throughout the region., The financial support provided by the Spanish Ministry for Science and Innovation (CGL2009-13990-C02-01), MINECO (CGL2013-46458-C2-1-R) and ERD funds is gratefully acknowledged. J. Urbanczyk thanks MEC for a FPU fellowship.

The effect of magma intrusion on gas outburst is illustrated by a case study of the exposed magma intrusion in the 313 mining area, upper coal seam Number 3, in the Qiwu Mine located in Shandong province. Vitrinite reflectance, mercury injection, and maceral statistical analysis are used to characterize the coal. The aspects of coal metamorphism include changes in micro-components as well as in coal structure, the formation of new substances, and changes in gas absorption and storage. The results show that vitrinite reflectance increases within the region influenced by magma intrusion. The metamorphosed region may be divided into a weakly affected belt, a medium affected belt, a strongly affected belt, and a completely affected belt. Compared to the unaffected coal the total pore volume, as well as the amount of big and middle sized holes, increases while the number of transition holes and micro-pores decreases. This diminishes the absorption capacity of the matrix but enlarges the total gas storage space. Vitrinite content initially decreases slightly but then increases rapidly while the inertinite content increases at first but then decreases. Exinite content decreases, then increases, and finally drops to zero. Higher vitrinite, and a lower inertinite, content increase gas absorption ability. This balances reduced adsorption caused by changes to pore structure. Consequently, gas adsorption capacity is not substantially reduced as the coal rank increases. Thermal metamorphism of the coal produces CH4 and other hydrocarbons that increase the total gas content in the coal seam. Asphaltene migrates into the medium and weakly affected regions filling in the pores and fractures there. This plugs the pathway for gas transport. A barrier is formed that hinders gas flow. CO2, H2S, N2, and other gases carried in by the magma react to produce CO2, which increases in relative concentration and enhances the risk of gas outburst. The two barriers, magma intrusion on one side and the medium and weakly affected belts on the other, as well as the unaffected coal seam itself, trap a large amount of gas during the thermal activity. This is the basic reason for gas outburst. These conclusions can enlighten activities related to gas prevention and control in a low rank coal mine affected by magma intrusion. Keywords: Magma intrusion, Gas outburst, Low rank mine, Thermal metamorphism, Pore structure, Adsorption and storage performance

The aim of this work is to investigate the influence of the addition of organic inerts such as charcoal with a well-controlled particle size on the development of fluidity in three coking coals of different rank, maceral composition, and rheological properties. Three size fractions of charcoal, < 20, 20–80, and 80–212 μm, that can be considered as artificially prepared inertinites were used. The different charcoal fractions were added in amounts of 2, 5, 10, and 15 wt.% to selected high-quality coking coals with a Gieseler maximum fluidity (Fmax) of 373 (LF), 541 (MF), and 1891 (HF) ddpm. Increasing the amount of charcoal in the blend led to a progressive inverse exponential reduction in fluidity. This reduction was accompanied by a shortening of the fluid interval due to an increase in the softening temperature. In the case of the finest charcoal fraction, the inhibition of fluidity was even more pronounced. The HF coal with a relatively high fluidity was very sensitive to minimum amounts of charcoal addition, losing nearly half of its fluidity when 5 wt.% charcoal was added. A similar reduction in Fmax was also observed for LF, while MF with only a slightly higher fluidity displayed a different trend. From the results it can be seen that the inherent characteristics of a coal are critical factors that affect the extent of the reduction in fluidity caused by the incorporation of charcoal. The differences can be partially attributed to the amount of inertinite present in the parent coal and to the macerals within the inertinite, especially fusinite, semifusinite, and inertodetrinite. In relation to petrographic changes in the matrix of the semicokes, there is a general trend for isotropic material to increase and the size of the anisotropic textures to decrease with the addition of charcoal. Inclusions within the semicoke matrix also change according to the amount and the size of the charcoal added to coal., The research leading to these results has received funding from the Research Programme of the Research Fund for Coal and Steel (Grant Agreement number RFC-PR- 09024). Co-financing from PCTI grant COF11-39 and funds from MICINN (PIB2010BZ-00418 project)

The development of coal char structures with pyrolysis has been extensively investigated but has traditionally been focused on the carboniferous coals in the northern Hemisphere. In this investigation, the properties of pyrolysis chars generated from inertinite- and vitrinite-rich coals (81% and 91% mmb by volume, respectively) collected from selected South African coalfields were determined. Chars were generated at 450, 700 and 1000 °C. The properties of coals and chars were examined using the chemical, physical, petrographic, solid-state 13C NMR and X-ray diffraction analytical techniques. The objective was to generate results for further studies including molecular modelling and atomistic reaction kinetics. A good correlation was found between the total maceral scan (rank) and aromaticity as the pyrolysis temperature increased, as well as between the aromaticity measurements with XRD and NMR techniques. The chemical structure of the intertinite-rich and vitrinite-rich chars at 700–1000 °C was remarkably similar in terms of the proximate, ultimate, total maceral scan and aromaticity values. Greater transition occurred in the vitrinite-rich coal, implying a thermally more activated coal. Differences in the physical structure of the chars at these temperatures were observed in terms of the surface area using the Dubinin–Radushkevich (D–R), the Brunauer–Emmet–Teller (BET) and Langmuir methods as well the microporosity from the CO2 adsorption method. The macerals were not distinguishable at 700–1000 °C. However, the differences in maceral composition of the coals resulted in substantially different char forms during thermal conversion. The intertinite-rich coal formed more denser chars and higher proportions of thicker-walled networks (60–65% by volume). The vitrinite- rich coal showed higher proportions of isotropic “coke” (91–95% by volume), which contributes to a high distribution of surface area and micropores. Therefore, on a chemical level, the high temperature chars were similar. Differences existed in the physical structure at high temperatures. The physical structures, char forms and crystallite diameter (La) significantly distinguished the chars at high temperatures, where La for inertinite-rich chars was 37.6 Å compared with 30.7 Å for the vitrinite-rich chars. The La property, in particular, played a significant role in investigations for the molecular structural properties of the inertinite- and vitrinite-rich chars, including their reactivity behaviour with carbon dioxide gas South African Research Chairs Initiative of the Department of Science and Technology and National Research Foundation of South Africa (Chair Grant No. 86880, UID85643, Grant No. 85632); SANEDI

Pulverized fuel combustion should be efficient in terms of power generation, resulting in less unburned carbon (UBC) in ash. In this study, three types of samples from stockyard, coalfeeders to mills, and bottom ash (BA) were taken from a local thermal power plant for 12 days. Proximate analysis of stockyard coal (sub-bituminous) resulted as 9.57% ash, 37.14% volatile matter, 52.91% fixed carbon, and a gross calorific value of 6640 kcal/kg. Petrographic analysis of coal showed that more than 80% consisted of reactive macerals. Coal from coalfeeders was also analyzed in terms of moisture content and sieve analysis. BA samples were analyzed and UBC content of BA over a 12 day period changes between 0.49 and 0.71% for Unit 1 and 0.26 to 0.69% for Unit 2. A relationship was seen between the moisture content and size distribution of coal from the mill inlet with UBC in the BA. A modified population model was used to estimate UBC as a function of size distribution, moisture content, mill environment constant, boiler environment constant, and residence time. A population model was used because the grinding and combustion operations are similar in terms of formation of new particles. It is seen that the model proposed is in agreement with the experimental results. In conclusion, in order to lower the amount of UBC in ash, the size distribution and moisture content of feed coal to mills should be stabilized. © 2015 Elsevier B.V. All rights reserved.

An investigation was undertaken to determine the distribution of chemical-, petrographic- and mineralogical properties of large coal particles of different sizes and densities and to evaluate a suitable reaction rate model for combustion of corresponding chars. This was undertaken in order to contribute to the knowledge of the combustion kinetics of large particles in fluidized bed combustion and moving bed combustion/gasification. The study was confined to a mineral rich (24.1 wt%) and inertinite rich (74 wt%) parent coal (precursor) that was separated into different sizes and density fractions. The combustion reactive properties of chars prepared at 1100 °C and at a reaction temperature of 1000 °C were determined using a horizontal tubular furnace with the associated on-line analysers and temperature controllers. Coal particles in the size range of 0.50–53 mm diameter and density from 1.4 g cm−3 to 2.0 g cm−3 were studied. The characterisation of the different coal samples consisting of ash content, maceral content, fuel ratios and calorific values showed that the parameters did not vary significantly over the particle size ranges, but were different for the different density fractions. Combustion studies showed that particle size and density influenced the time required for complete conversion of the chars. The smaller particles and low density particles reacted faster and the modeling of the experimental data showed that the isothermal shrinking un-reacted core model with film and ash layer diffusion was applicable. The effective ash layer diffusion becomes more prominent as the density increased and the mass transfer coefficients correlated well with published results National Research Foundation, South Africa

The generation of coal chars is an important intermediate step in coal conversion processes such as combustion and gasification. The char structure impacts their behaviour in these processes. Detailed investigations on slow-heated coal chars utilizing molecular modelling approaches are limited in comparison to the more extensive work on coal. Also South African (SA) coal is generally not as well studied as the vitrinite-rich coals in the Northern Hemisphere. Both inertinite-rich and vitrinite-rich coals are available in SA, formed with the same inputs but in different depositional environments, thus providing an opportunity to examine maceral influences without the challenges associated with maceral separation. Experimental work was performed to characterize de-ashed chars generated by heating the inertinite- and vitrinite-rich South African Gondwana coals of the Permian Age under inert atmosphere (nitrogen gas) to 1000 °C at a rate of 20 °C/min and maintain this temperature for 60 min before cooling. Experimental work included petrographic analysis, elemental analysis, helium density, 13C NMR, XRD, and HRTEM analyses. The maceral purity was enhanced with density separation prior to pyrolysis. Analytical data was used to construct molecular structures comprising polyaromatic hydrocarbons with oxygen, nitrogen and sulphur functionalities. Aromaticity and skeletal density measurements provided additional constraining data. The inertinite-rich char model comprised 8586 atoms comprising 21 individual molecules with a composition (normalised to 1000 carbon atoms) of C1000H105O14N22S1, while the vitrinite-rich char model was 8863 atoms within 37 molecules with a normalised composition of C1000H125O21N22S3. The two chars were thus chemically similar; however, the size of polyaromatic molecules differed, as observed from HRTEM and XRD data. The inertinite-rich chars contained larger molecules (La (10) = 37.61 ± 2.32 Å) than the vitrinite-rich chars (La (10) = 30.74 ± 0.77 Å). This will influence the fraction of active carbon sites located on the crystallite edges and defects of the basal planes that may contribute to the lower reactivity of inertinite-rich chars in comparison to vitrinite-rich chars. Atomistic representations of these chars was constructed capturing a portion of the structural diversity observed from image analysis of the HRTEM lattice fringe micrographs. While the char generation parameters used in this study produced similar chars derived from the South African inertinite- and vitrinite-rich coals, the crystallite diameter, La, was found to be the property that distinguished the two chars significantly. This may hold promise for exploring structural-reactivity relationships South African Research Chairs Initiative of the Department of Science and Technology and National Research foundation of South Africa (Chair Grant No. 86880, UID85643, Grant No. 85632)

Large dumps of coal waste are a necessary consequence of coal mining. In some cases, the waste material undergoes self-heating and combustion that changes the nature of the organic- and mineral matter of the wastes. The range of the alterations depends on the properties of the waste rocks (maceral composition and rank of organic matter) and the heating history, especially the rate and duration of heating and the degree of access for air and moisture. The Starzykowiec dump located within Chwalowice coal mine (Upper Silesia, Poland) dates from the beginning of the previous century. It contains wastes that have been thermally altered to varying degrees—reflected in colors ranging from black through yellowish, orange, red, to white and in their structure (some altered wastes are hard and solid, others soft). A coal mud collector is located on the top of the dump. Some of the waste contains organic matter both visible under a microscope and as a bituminous fraction analyzed by GC-MS. Others contain organic matter only visible under a microscope or only a bituminous fraction analyzable by GC-MS or, in some, no organic matter at all. The alterations typically seen in the wastes indicate that the temperature rose slowly; macerals show paler colors, higher reflectance, and no porosity due to devolatilization. In some waste, their yellowish color and very high reflectance indicate a very pronounced degree of alteration. In other strongly altered waste, porous, yellowish organic matter is indicative of high heating rates. Mineral-matter compositions of the waste on the Starzykowiec dump also show a wide range of thermally induced changes. There are wastes where mineral matter is unchanged and others where primary compositions are completely transformed. High-temperature mineral phases, e.g. diopside, mullite, and indialite, may be formed. On the basis of the color of powdered samples, wastes can be divided into eight groups of different mineral compositions. However, mineral phases such as gypsum and other sulfates formed due to late-stage weathering can change the chemical compositions of the waste. The organic compounds present in dichloromethane extracts, the distributions of which were determined with GC-MS, include n-alkanes, acyclic isoprenoids, pentacyclic triterpanes (hopanes and moretanes), aromatic hydrocarbons together with their C1–C5 alkyl derivatives, and PAHs from naphthalene to perylene. Relative percentage contents of PAHs, and biomarker- and alkyl-PAHs ratios allow waste organic matter composition, geochemical features, and thermal transformations caused by self-heating to be assessed. Several diagnostic changes in biomarker distributions identified include the thermal removal of lighter compounds and related changes in Pr/Ph, MNR, DNR, and TNR values, and enrichment in C31 pentacyclic compared to C30 and C29 triterpanes. Geochemical parameters were correlated to each other and to vitrinite reflectance. Results indicate that biomarker- and aromatic-hydrocarbon parameters, normally applied in the assessment of organic matter thermal maturity, show comparable patterns in the coal waste. Correlations with vitrinite reflectance and between individual geochemical parameters agree with thermal evolution trends typical of coal-waste deposits unchanged by self-heating whereas, in rocks altered by self-heating, biomarker- and aromatic-hydrocarbon parameter values approximate those characterizing overheated organic matter and coal pyrolysates.

Coal consists of organic and mineral matter. Fixed carbon from organic matter measures the energy output of coal during combustion. Mineral matter determines how coal responds to combustion and affects reservoir porosity and permeability. Minerals infill pores, cleats, or fractures and replace the organic composition of coal. Organic composition is grouped into maceral association as microlithotypes and macrolithotypes, the latter for megascopic field descriptions (e.g. coal cores and mine face). Coal composition controls reservoir properties such as gas adsorption capacity, gas content, porosity, and permeability. Permeability is important to gas transport from coal matrix pores to the production well. Coal permeability is a function of the width, length, and height of cleats or fractures as well as the aperture, spacing, frequency or density, and connectivity of cleats or fractures. Coal cleats or fractures formed during burial, compaction, and coalification (endogenetic) and after coalification during deformation, uplift, and erosion of the basin of deposition.

Coalification is caused by temperature and pressure inherent to burial and is enhanced by geologic time and tectonism. Coalification processes include dehydration, bituminization, debituminization, and graphitization, which involve chemical and physical changes of organic matter. Coal is classified as lignite, subbituminous, bituminous, and anthracite but is classified differently by the United Nations Economic Commission for Europe and the American Society for Testing Materials. Coal is composed of vitrinite, liptinite, and inertinite maceral groups, which influence hydrocarbon generation. Thermogenic gas forms during bituminization and biogenic gas is generated after uplift and exposure of coals when groundwater and microbial activity are established. Gases are stored by adsorption on surfaces of coal pore and cleat (fracture) systems. Pore types consist of intramolecular nanopores, coal matrix micropores, mesopores, and macropores. Gas is released by reduction of hydrostatic pressure, leading to gas diffusion in the coal matrix obeying Fick's law, and migrates to the cleat system, governed by Darcy flow to the open borehole.

This chapter describes the basics of petrographic analysis including lithology, the classification of macerals, minerals and their associated rocks, the concept of rank, and the impact that these factors have on the technological properties of coal. The development of modern techniques towards grain analysis and mineral and maceral transitions is briefly described.

This chapter introduces the basic principles governing fuel blending applied to coal–coal blends, with particular emphasis on different ranks of coal. The study of macerals is introduced. Blending coal for combustion and gasification, particularly electricity generation, distinguished from blending for coke production in the steel industry. The combustion and gasification processes are explained. The chemical composition and calorific value of a fuel are discussed. The importance of kinetics, thermodynamics, and ash chemistry are all discussed.

This chapter presents the basic concepts of coal petrology and discusses coal parameters that have been noted as potential triggers for spontaneous combustion. Macerals, the microscopically identifiable organic constituents of coal, are one of three basic parameters that define coal. The other two parameters are the coal rank, the measure of metamorphism of the organic constituents, and the inorganic content of the coal, most visibly seen as the minerals associated with coal. Among many factors that trigger spontaneous combustion, oxidation of coal at ambient temperature is the major one. It is an exothermic reaction, the exact mechanisms of which are not fully understood. At very low temperatures, reaction between coal and oxygen is physical (adsorption), and it changes into chemisorptions starting at ambient temperature. Particle size and available surface area are important because adsorption is an important process in coal oxidation. Higher adsorption, and the monolayer capacity in particular, influences the amount of moisture that can be retained in the coal and moisture is frequently cited as the main control on spontaneous combustion. Fractured and faulted thick coal seams with pyrite and organic shale partings are particularly susceptible to spontaneous combustion.

This chapter begins by describing coal and coke. The composition of coal is very complex, and the types of coal differ considerably. All coal has been formed from biomass. Coal is often classified in terms of its rank, which increases from brown coal to anthracite. Brown coal, lignite and sub-bituminous coals are designated as low-rank coals, whereas higher-rank coals are often called hard coals. There are two methods to analyze coal, namely, the proximate analysis and the ultimate analyses. The proximate analysis determines the moisture, volatile matter, ash and fixed carbon in the coal. The analysis is an essentially practical tool providing an initial indication of the coal's quality and type. For the ultimate analysis, the percentages of carbon, hydrogen, oxygen, sulfur and nitrogen are determined. There are also other elements that are contained in the carbon like chlorine and phosphorous. The heating value of the coal is determined through combustion of the sample in a calorimeter. Other properties like caking and swelling properties, hardness, and density are also discussed. The chapter also discusses liquid and gaseous feedstocks, in which refinery residues are explored. The term “refinery residue” covers a wide range of materials, some of which are solid at ambient temperatures and others that are liquid under these conditions. The most common residues are obtained by thermally cracking vacuum residue or by subjecting it to solvent de-asphalting. Finally, biomass is also discussed along with its properties, production, etc.

Publisher Summary Coal is the dominant solid fuel source worldwide. This chapter discusses coal formation, coalification, and characteristics, with an emphasis on the organic or combustible materials in coal. Coal is a sedimentary rock composed of both organic and inorganic materials. Coal is composed of macerals, discrete minerals, inorganic elements held molecularly by the organic matter, and water and gases contained in submicroscopic pores. Organically, coal consists primarily of carbon, hydrogen, and oxygen, and lesser amounts of sulfur and nitrogen. Inorganically, coal consists of a diverse range of ash-forming compounds distributed throughout the coal. The inorganic constituents can vary in concentration from several percentage points to parts per billion of the coal. This chapter also discusses the relationships between coal structure and behavioral characteristics, and coal resources and reserves, with an emphasis on those located in North America and the United States. It presents coal petrography, traditional methods for analyzing coal, and evaluation of coal properties by nontraditional characterization methods, with an emphasis on how they are applied in industrial applications. Furthermore, it describes traditional coal characterization methods and their application to industry, with some special tests specific to some companies and nontraditional techniques.

5 pages, 2 figures.-- PMID: 17204447 [PubMed].-- Available online on Dec 1, 2006., A recent paper by Sun [X. Sun, Spectrochim. Acta A 62 (1–3) (2005) 557] attempts to characterize a variety of liptinite, termed “barkinite”, from Chinese Permian coals. The component identified does not appear to fundamentally differ from previously-described liptinite macerals included in the International Committee for Coal and Organic Petrology's system of maceral nomenclature. Further, chemical comparisons made with macerals from coals of different rank and age are flawed because the author did not account for changes in chemistry with rank or for the chemical changes associated with botanical changes through geologic time. The author has not satisfactorily proved his hypothesis that the component differs morphologically or chemically from known liptinite-group macerals.

12 pages, 7 figures, 3 tables.-- Printed version published on Nov 3, 2007., Laser ablation ICP-MS has been used to produce element profiles from polished coal samples. The elements analysed (V, Ge, Ni, Cu, Zn, Sr and Ba) were those known to have an organic association, with the addition of Al and Fe as controls on the clay and pyrite abundances. The element profiles were compared with the petrography and a statistical analysis was also carried out. Sporinite was found to have low trace element concentrations, inertinite higher concentrations of detrital elements and vitrinite higher concentrations of V, Ge and Al. The relationships between these elements are explored and all are thought to be present in the organic matter and not as minerals. It is thought that these elements became concentrated during diagenesis, with the possibility that some of the Al could be residual. The Cu/Ni ratio in the pyrite is relatively constant, suggesting constant ionic proportions during diagenesis, and possibly a seawater source.

This chapter explores the process of pyrolysis, which is the thermal breakdown of solid fuels in a gaseous environment. It examines elements of reactor design relevant to the pyrolysis of solid fuels. The samples handled, range from forestry and other organic wastes to bituminous coals. Using some of these tools, the chapter also examines the pyrolytic behavior of coal macerals and several Southern Hemisphere coals. Furthermore, it addresses the particular difficulties inherent in designing pyrolysis experiments and describes how the configurations of specific bench-scale pyrolysis reactors affect the results of measurements. Eventually, it attempts the conceptual integration of sample characterization, reactor design, and the evaluation of resulting product distributions. It also focuses on reactor design with respect to tar recovery. Finally, it illustrates several examples, where bench-top experiments were used to develop a better understanding of the behavior of solid fuels in pilot or plant scale operation. The chapter also highlights how a study of the thermochemical reactions of coal macerals was extended to Southern Hemisphere coals, to evaluate their properties during pf-combustion.

Publisher Summary Coal petrography is the study of the organic constituents of sedimentary rocks, originally, by optical microscopy of thin sections (transmitted light) or of polished blocks (reflected light). Fluorescence microscopy is used to complement the more traditional approaches. The latter technique is based on the ability of organic matter to absorb UV light and then emit (fluorescence) at longer wavelengths in the visible spectrum. This chapter presents several well-regarded works on the formation of coals and their macerals and on relationships between their chemical structures, morphologies and pathways of geochemical maturation. ‘Macerals' are the organic components of coals, defined in terms of their morphologies, as observed by optical microscopy. Broadly, these morphological features correspond to the structures of original plant material deposited in peat bogs. With maturation, the properties of the different biomasses tend to converge toward a narrower spectrum. The microscopically identifiable morphological features of macerals correlate reasonably well with trends in measured chemical properties, such as elemental composition (aliphatic/aromatic content) and observed pyrolytic behavior. Based on these works, the chapter evaluates methods for examining the thermal behavior of coals.

A multiple reaction model (MRM) was used to characterize the kinetics of pyrolysis of single coals and binary blends; the MRM represents the kinetics through a continuous distribution of the activation energies of the individual reactions (DAEM). Kinetic parameters were assessed from experiments performed in a drop-tube reactor at high temperatures (1000-1300degreesC) and low residence times (60-320 ms). Results are given for three single coals and two binary blends. Volatile yields are generally greater than the ASTM standard values due to fewer secondary reactions under the experimental conditions. The proposed model satisfactorily reproduces devolatilization curves as a function of activation energy distribution and a parameter that depends on the liptinite, vitrinite and ash content of the coal or blend. A defined "Pyrolysis Yield Index" (PYI) that combines the maceral composition and ash content, appears to correlate well with a parameter of the kinetic model. Blends constituted by petrographically similar coals show no significant deviation from the expected weighted average of the single coals. (C) 2003 Elsevier B.V. All rights reserved.

This work analyses a set of perhydrous coals (mainly composed of huminite/vitrinite maceral group) in order to determine the inter-relations between the hydrogen content and the modifications in the coal structure at a molecular level. The study involves the direct solid state characterisation of the coal combined with the analysis of representative fragments of the coal network obtained through flash-pyrolysis. The perhydrous character of the coals is not reflected either in the aliphatic hydrogen concentration (from FTIR data) or by the presence of straight-chain aliphatic moieties in the pyrolysates. This structural study shows that perhydrous coals contain mainly aromatic structures with 1–2 rings and a very small concentration of aromatic rings of large size. In agreement with this, phenol and alkyl phenols are the most prominent degradation products whereas other aromatic compounds (mainly benzene and naphthalene derivatives) are minor and probably evaporative compounds. The major structural elements in the samples studied are simple phenols with a preponderance of substituted para alkyl. The results obtained show that the processes of hydrogen enrichment affect the reactions of aromatisation and condensation. During the natural evolution of the perhydrous coals the transformations of the oxygenated functionalities in the lignin precursor seem to have taken place without the parallel structural reorganisation of the lignin framework responsible for the formation of polycyclic aromatic systems. As a result, the chemical structure of perhydrous vitrinites in coals is substantially modified with respect to that described in ‘normal' coals. The results obtained also indicate that the source of hydrogen content and the effect that it has during the subsequent evolution process of the coals, affects the chemical structure of the perhydrous vitrinite and hence its properties and behaviour., Financial support for this work was provided through a contract with the European Community (No. 7220/EC-769).

This paper deals with all solid sedimentary fossil fuels, i.e. coal, the main one for geological reserves and resources, peat, and oil shales. Definitions of coal ( < 50% ash) and coal seam (thickness and depth limits) are examined in view of an international agreement regarding new concepts for a common reserves and resources evaluation using the same nomenclature. The 50% ash limit, already adopted by UN-ECE for coal definition, allows the creation of a new category—the organic shales (50–75% ash)—comprising energetic materials still valuable for thermal use (coal shales) or to be retorted for oil production (oil shales). Geological relations between coals, oil shales, solid bitumen, liquid hydrocarbons, natural gas, and coalbed methane are also examined together with environmental problems. As a final synthesis of all topics, the paper discusses the problems related with a modern geological classification of all solid sedimentary fuels based on: various rank parameters (moisture content, calorific value, reflectance), maceral composition, and mineral matter content (and washability). Finally, it should be pointed out that the paper is presented as series of problems, some of them old ones, but never resolved until now. In order to facilitate the next generation of coal geologists to resolve these problems on the basis of international agreements, all sections begin with documented introductions for further questions opening an international enquiry. The authors hope that the answers will be abundant enough and pertinent to permit synthetic international solutions, valuable for the new millennium, with the help of interested consulted authorities, international pertinent organisations, and regional experts. D 2002 Elsevier Science B.V. All rights reserved.

Publisher Summary Coal is very heterogeneous and is a mixture of organic matter (macerals) and inorganic matter (minerals). Organic matter was formed through the accumulation of plant material, which has undergone biochemical and metamorphic changes referred to as “coalification.” Depending on the coalification (rank), composition of the coal organic matter and the coal properties vary. The surface of coal is heterogeneous at different levels. At the molecular level, it can be depicted as a hydrocarbon matrix that contains various functional groups. The composition of the matrix varies with the coalification. Maceral make-up, inorganic matter inclusions, and porosity determine heterogeneity at the microscopic level. Various associations of macerals with each other and with minerals are referred to as “lithotypes” and it is known that many coal physical properties can be predicted from lithotype characteristics. This chapter first defines what is meant here by surface properties. Although the relationship between wettability and floatability is not straightforward, only those particles of which the wettability is characterized by a contact angle larger than zero (Θ > 0) can float, so it is generally assumed that wettability as expressed by contact angle is the most fundamental of flotation-related surface property. In one of the attempts at describing the coal flotation properties, it was postulated that coal surface properties are determined by (1) the hydrocarbon skeleton of coal (related to coal rank), (2) the number and type of oxygen functional groups, and (3) mineral matter impurities.

Publisher Summary Coal is an organic sedimentary rock whose chemical composition changes with coalification. As metamorphic development of coal (coalification) is synonymous in chemical terms with progressive enrichment of the coal substance in organically bound carbon, all coals, regardless of their origin or type, can be arranged in an ascending order of carbon content. Coal chemists distinguish coals into three structures: (1) first-order structure that gives the size distribution of the macromolecules and molecules in coal and the degree of cross-linking, (2) second-order structure that details the cross-links and the structure of the carbon skeleton, (3) third-order structure that is the nature and distribution of the functional groups. In all coal classification systems by rank, volatile matter content and calorific value (heating value) are the most important indices. Lower-rank coals are classed according to their calorific values calculated on a moist basis. Coal, an organic sedimentary rock, is very heterogeneous; it contains organic matter that consists of various components with distinct chemical and physical properties referred to as “macerals” and inorganic matter mostly in the form of minerals. The definition of the macerals is based on microscopic examination. The macerals are classified into three groups—vitrinite, exinite (liptinite) and inertinite—either because of similar origin (exinite group) or because of differences in preservation (macerals of vitrinite and inertinite groups).

Publisher Summary This chapter discusses the role of coal maceral composition in reducing sulfur dioxide and oxides of nitrogen emissions from pulverized coal flames. Coal-fired plants emissions are influenced by fuel nitrogen and fuel sulfur content as well as combustion temperatures and combustion histories. Recent investigations show that the volatiles evolution and char combustion patterns are dependent on its coal chemical composition and the maceral composition. Thus, it is reasonable to expect that through a combination of effects, controlled by the petrographic distribution of fuel sulfur and nitrogen as well as the individual reactivities of the coal macerals themselves, the production histories of the oxides of sulfur and nitrogen and their final emission levels is influenced by the coal petrographic composition.

Publisher Summary This chapter discusses the production of coal fractions with varying petrographic and mineral compositions in hydrocyclone separator and the liquefaction of each coal fraction to assess the roles of petrographic and mineral composition on conversion and product distribution. The overflow fractions obtained by hydrocyclone separation, concentrated in reactive macerals and reduced in mineral content, produced an improvement in liquefaction conversions over the original coal, together with a shift in the net product distribution toward higher oils and lower residue content in the liquid products. The quantity of mineral matter removed at the stage of filtration decreased. Using these beneficiated coal fractions, possible economic benefits may be obtained due to the reduced size of the liquefaction unit. More results are required to confirm these findings and work is being carried out using coal fractions obtained by froth flotation.

Publisher Summary Fine-coal cleaning is studied using dry, triboelectrostatic experimentation. The 45–75 μn coals are pneumatically transported through a Cu-loop tribocharger and then transported through a 100–200 kV/m electric field. Positively charged coal is deflected to the negative electrode and negatively charged minerals are deflected to the positive electrode. Samples are retrieved and subjected to petrographic analysis. Petrographic analysis of these samples showed that for high volatile A and B bituminous coals, vitrinite macerals are significantly enhanced in the clean coal, whereas the fusinite + semifusinite + exinite maceral are enhanced in the tailings/minerals. For a high volatile C bituminous coal, this trend in enhancement is not observed. The vitrinite partitioning, greater for dry processing than for wet processing, may be related to differences in surface chemical and physical properties of the coals.

Publisher Summary This chapter discusses the production of coal maceral concentration by floatation. It was possible with timed batch flotation tests to produce an inertinite-rich concentrate provided the only reagent added is a frother. Tests on point of Ayr coal show that with the addition of even small quantities of collector, (paraffin) this effect nullified to the point where there is no differential floatability among the macerals. Results from flotation tests on discrete size fractions of three coals produced widely differing inertinite enrichment ratios. This differential floatability is considered to be due to variations in the liberation characteristics of inertinite macerals.

Publisher Summary This chapter examines several coal preparation processes, including alkali leaching, acid washing, selective oxidation of sulfursulfursulfur, and chemical removal of coal nitrogen. The benefits and consequences of the various coal pretreatments on the subsequent conversion processes are being assessed from various viewpoints: coal/char reactivity, the nature of the residual mineral matter, and the possible impacts on things as the total energy balance, process economics, and the overall pollutant yield. The chapter presents an alkali leaching process to remove the mineral matter from coal, which changes the coking properties of the coal and increases the reactivity to carbon dioxide (CO2). Work is underway to determine the relative distribution and mode of the association of potential catalytic species in the cleaned coal sample and the effect of the cleaning process on the intrinsic reactivity of the resultant chars to O2 and H2O. Work is being carried out using the laser nanoreactor to extend the range of temperatures and reactant concentrations to cover the range of maceral types present in the coal.

Noncaking bituminous coals were separated to three groups respectively by a sink-float method in zinc chloride solution. Each group of samples was rapidly pyrolyzed in a free-fall pyrolyzer at atmospheric pressure under nitrogen, at temperatures up to 1253K, and heating rates of 4000~6000Ks−1. The pyrolysis characteristics of the lowest density group revealed the highest liberation rate and the most effective desulfurization extent. The reactivity of organic sulfur was considerably affected by the variable contents of sulfur form with the change in maceral group content.

Some high organosulfur coals occur in upper Permian coal—bearing sequence in Guidin, southwest China. By electron microprobe analyses, the content of organosulfur in desmocollinite is as high as 10.3%. Petrologically, the coal has following characteristics: 1)Desmocollinite accounts for a great part of macerals; 2)Most of the desmocollinite fluoresces brown — orange, although the coal rank is up to VRo, max = 1.48%; 3)There are many pyritized microbe bodies with the shapes of coccoid, rod and curved rod, indicating that a large amount of microbes took part in the peatification; 4)Many authigenic calcite, dolomite and quartz crystals existed in the coal; 5)Some marine fossils are found in coal. XPS analysis has been made on the bulk sample. The major organosulfur form is thiophenic, while a very small part is aliphatic. Three series of thiophenic compounds and its derivatives were determined by GC — MS in extract, and no aliphatic sulfur was detected.

The behaviour in hydroliquefaction (H2, tetralin, 400 °C) of four Spanish lignites with different petrographic composition and a similar ash content was studied and the nature of the derived oils was evaluated. Vitrinite and/or vitrinite plus exinite contents and percentages of total and organic sulphur correlate with conversion yields. Maceral composition does not appear to influence the nature of the derived oils., The authors thank EC (contract no. EN3V-0055-E) and CICYT for financial support.

Publisher Summary This chapter presents a study of coal surfaces by means of energy-dispersive X-ray microanalysis (EDXMA). Sections through coal macerals were prepared from fresh bulk coal samples. Conventional optical microscopy was used to select macerals for detailed analysis. A simple method was developed for oxygen analysis where the ratio of the oxygen to carbon peaks was measured. The O/C peak ratio changes monitor oxidation directly and can be related to standard curves of measured O/C against oxygen content of stable materials. A JEOL JSM35CF scanning electron microscope with a Kevex Delta Quantum light element detector was used. Measurements were made at an accelerating voltage of 5 kV so that the X-rays were generated within a volume of approximately 1.5 μm radius. The electron beam produced local pitting on the maceral surface, which marked the analyzed site exactly. As SEM images naturally highlighted mineral matter, areas without mineral oxygen could be selected with confidence.