Low Volatile Bituminous Research Articles

Effects of Fracturing Fluids Imbibition on CBM Recovery: In Terms of Methane Desorption and Diffusion

Summary Hydraulic fracturing technology has been widely used to improve the productivity of the coalbed methane (CBM) reservoir, during which tons of fracturing fluids infiltrate the coal seam. However, the effects of fracturing fluids imbibition on CBM recovery are still unclear. In this study, spontaneous and forced water imbibition experiments in methane-bearing low-volatile bituminous (LVB) coal were conducted at various gas adsorption equilibrium pressures, following which methane desorption and diffusion experiments were performed. These experiments simulated the complete process of fracturing fluid imbibition during well shut-in and subsequent methane production upon reopening, which is helpful in understanding the impact of fracturing fluid imbibition on CBM production. The results show that water imbibition displaces adsorbed methane in the coal matrix, and with reservoir pressure increasing, the displaced effect decreases. Furthermore, the forced imbibition (FI) displaces less methane than the spontaneous imbibition (SI) due to water rapidly filling fractures and blocking methane migration out of the matrix in the FI. In the initial stages of gas production following spontaneous or forced water imbibition, the displaced methane diffuses out of the coal at a rapid rate and then slows down. Furthermore, in the case of FI, a significant amount of residual gas remains after desorption and diffusion due to the water blocking effect. However, the water blocking effect has a minimal impact on coal undergoing SI. In terms of desorption and diffusion, this study provides a comprehensive understanding of the effects of fracturing fluids imbibition on recovery of CBM, which is useful for practical shut-in operations following hydraulic fracturing in LVB coal seams.

Revisiting the petrology of lower Pennsylvanian (Namurian and Langsettian) coals in southern West Virginia and southwestern Virginia, USA

Namurian and Langsettian coals representing a vertical span of about 650 m were sampled from cores in southern West Virginia and western Virginia. The coal rank ranges from medium through low volatile bituminous. Historically, a significant portion of the production from the region has been for smokeless steam coals and for metallurgical coal. Despite the presence of thrust faults and the potential for fault-induced movement of mineralizing fluids, a depth-of-burial/geothermal-gradient model, as proposed earlier, appears to be sufficient to describe the increase of rank with depth. The coals generally have >70% total vitrinite (mineral-free basis) and a telovitrinite/(telovitrinite + detrovitrinite) ratio exceeding 0.75. Fusinite dominates the inertinite group macerals. An unnamed Langsettian coal had a high liptinite content but, otherwise, in part owing to the difficulty of detecting liptinites in medium and low volatile bituminous coals, liptinite appears to be sparse. Among the coals in the study, not all of them have been extensively mined. The Pocahontas coals represent the most significant economic resource.

The Permian Tunas Formation (Claromecó Basin, Argentina): Potential naturally fractured reservoir and/or coal bed methane (CBM) play?

The analysis of structural discontinuities in the Tunas Formation helps characterize this unit as a potential naturally fractured reservoir. The principal discontinuities are 1) fractures parallel to the bedding planes, 2) fractures coplanar to the axial planar cleavage, 3) dilatant fractures filled by quartz, and 4) subvertical shear fractures. Over a thousand measurements on microtectonic structures help infer a stress field whose maximum principal stress (σ1) has a SW-NE orientation. Based on this structural analysis, optimal orientations for exploration and/or production wells in the Claromecó Basin should be a 130° azimuth. Fracture spacing range between 30 and 100 cm in outcrops of the Tunas sandstones along the Ventana foldbelt (VFB). A similar fractured network is postulated for the subsurface of the basin.Organic-rich levels, ranging from coals to carbonaceous shales, occur in the Tunas Formation in the subsurface of the Claromecó Basin and are a potential shale gas resource play. These beds tend to cap successions of interbedded shales and sandstones. The coals range from semi anthracitic to low volatile bituminous. Vitrinite and fusinite prevail as organic matter types, ranging between 1.3 and 2.4 vitrinite reflectance (Ro). The occurrence within condensate-wet gas to dry gas windows reflect subsurface processes such as strong diagenesis and anchimetamorphism. The coal-rich levels in the Tunas Formation can be correlated with other Lower Permian organic-rich units in the Paraná Basin in Uruguay (Tres Islas Formation) and Brazil (Rio Bonito Formation). All are analogous to the lower Upper Permian Vryheid coals of the eastern Karoo Basin in South Africa with shale gas and coal bed methane (CBM) prospectivity.

Study on petrographic characteristics of devolatilization char/coke related to coal rank and coal maceral

Char/coke is the medium product of coal gasification, combustion, and metallurgy, whose morphological and optical characteristics are determined by coal rank and pyrolysis conditions. Twelve coals varying in coal rank from lignite to anthracite, collected in China, were used to study morphological and optical characteristics of char/coke upon different pyrolysis conditions systematically, specifically the char/coke structure and texture influenced by coal rank and coal maceral. Coke and char are distinguished by their caking ability. The morphology of the chars derived from low rank coals and high rank coals are closely related to coal maceral composition, whereas the morphology of cokes derived from high volatile bituminous A, medium, and low volatile bituminous is closely related to coal rank. In lignite, subbituminous, high volatile bituminous C, semianthracite, and anthracite, macerals are infusible during the heating process, but cavities generated in the low rank coals are related to the shapes of the liptinite macerals in the raw coals. Morphological changes of chars derived from high rank coals are difficultly to identify microscopically using an oil-immersion objective with a 1-lambda gypsum plate. in addition, the random reflectance (Rr) range of the chars becomes narrower as pyrolysis temperature increases. Overall, the Rr range of cokes is much larger than that of the chars, which is a result of the optical anisotropy of the caking coals. Although the Rr of vitrinite/huminite in the low and high ranks is distinct, the Rr of their chars is always similar when the pyrolysis conditions are the same. The Rr of char/coke is closely related to both coal rank and the final pyrolysis temperature. Longer residence time of the char/coke at the same pyrolysis temperature did not show a relevant difference in the reflectance of char/coke.

Predicting nitrogen release during coal tar decomposition

This paper develops a detailed phenomenological reaction mechanism for N-species transformations throughout tar decomposition, including tar-N sequestration into soot. It expands the previously validated mechanism for tar decomposition based on FLASHCHAIN® theory to cover N-transformations during pulverized fuel firing. Tar-N transformations are described by two distinctive features: (1) An elimination reaction that produces HCN governs the decay in the average moles of nitrogen per aromatic nucleus throughout tar decomposition; and (2) Empirical observations determine the fraction of tar-N incorporated into soot. Validation cases represent heating rates of at least several thousand degrees per second; temperatures from 600 to 1100 °C; tar contact times from 75 ms through 2 s; and coal ranks from subbituminous through low volatile bituminous. The predicted partitioning of coal-N into tar-N, HCN, soot-N, and char-N was within measurement uncertainties for all coals for simulated p. f. firing conditions, including the variation in fractional char-N levels from 0.4 to 0.8 across this domain. Since primary tar-N levels are directly proportional to fractional primary tar yields, and since ultimate soot-N levels account for one-third of tar-N with any coal type, the ultimate coal-N partitioning for CFD furnace simulations can be accurately described with two analyses: (1) A primary devolatilization mechanism to predict primary tar yields under rapid heating conditions; and (2) A submechanism to predict HCN release from char throughout devolatilization up to the point of char ignition. Dynamics may be resolved with either global reactions or the full tar decomposition mechanism, depending on the impact of the lag between tar decomposition and soot production in the subject application.

Visual Representation of Carbon Dioxide Adsorption in a Low-Volatile Bituminous Coal Molecular Model

Carbon dioxide can be sequestered in unmineable coal seams to aid in mitigating global climate change, while concurrently CH4 can be desorbed from the coal seam and used as a domestic energy source. In this work, a previously constructed molecular representation was used to simulate several processes that occur during sequestration, such as sorption capacities of CO2 and CH4, CO2-induced swelling, contraction because of CH4 and water loss, and the pore-blocking role of moisture. This is carried out by calculating the energy minima of the molecular model with different amounts of CO2, CH4, and H2O. The model used is large (>22 000 atoms) and contains a molecular-weight distribution, so that it has the flexibility to be used by other researchers and for other purposes in the future. In the low-level molecular modeling presented here, it was anticipated that CO2 would be adsorbed more readily than CH4, that swelling would be anisotropic, greater perpendicular to the bedding plane because of the rank of this ...

Improved Low-Volatile Bituminous Coal Representation: Incorporating the Molecular-Weight Distribution

A large ({gt}22 000 atoms) molecular representation of Pocahontas No. 3 low-volatile bituminous coal was generated that contains 215 separate molecular entities, ranging between 78 and 3286 amu, creating a molecular-weight distribution. Data used in this construction were based on (1) the average molecular properties and the carboxylation-oxidation molecular-weight distribution, (2) aromatic 'raft' size evaluation via image analysis of lattice fringe high-resolution transmission electron microscopy images, (3) molecular-weight distribution through laser desorption mass spectrometry, and (4) physical characteristics (molecular orientation and helium density). The large-scale coal representation enabled the incorporation of molecular-weight diversity, which is an improvement to the structural modeling of coal. The large-scale model is necessary to conform to an appropriate molecular-weight distribution. A preferred orientation that is expected for a coal of this rank was imposed. The inclusion of these improvements will better enable the model to be used in application studies. 39 refs., 7 figs., 2 tabs.

Evaluating the coalbed methane potential of the Gething coals in NE British Columbia, Canada: An example from the Highhat area, Peace River coalfield

Abstract Lower Cretaceous coals from the Gething Formation in the Highhat area of NE British Columbia were analyzed for gas content as part of an exploration program. Samples of continuous wireline core and cuttings were processed. Vitrinite reflectance and dry ash-free volatile matter both indicate that the rank of the coal is low volatile bituminous. The coals are well cleated and contain shear fractures, as seen in the core description and in the FMI logs. Coal cuttings were screened to remove a very fine fraction (− 200 mesh) and then treated in heavy liquid (SG 1.75 g/cm 3 ) to remove inorganic lithologies. For the cores, total gas content ranges from 516.9 to 876.8 scf/t (16.1–27.4 cm 3 /g; adb) with a mean value of 671.1 scf/t (20.9 cm 3 /g) at 20.5% ash (adb). For the cuttings, all desorbed gas was assigned to the + 200 mesh/float 1.75 SG weight fraction. On this recalculated basis, total gas content for the processed cuttings ranges from 651.8 scf/t (20.4 cm 3 /g) to a high value of 2083.6 scf/t (65.1 cm 3 /g; adb). Weight yields after screening/floating are generally low. For samples yielding very low values ( 3 /g; adb) with a mean value of 760.4 scf/t (23.8 cm 3 /g) at 15.5% ash (adb). The desorbed gas is predominantly methane (98–99%; air-free and acid-free basis) and average carbon dioxide is about 6%. Methane is thermogenic based on isotopic analysis. Methane adsorption isotherm analysis at reservoir conditions shows that the Gething coals are at least 95% gas saturated. Using 1300 m as a depth cut-off and an average gas content of 672 scf/t (21 cm 3 /g), GIP (gas-in-place) in the Highhat prospect area is estimated to be 270 bcf (billion cubic feet). This translates to 24.5 bcf/section (a section is equal to a square mile or 640 acres) for the 11 sections of land in the vicinity of the corehole or to 3 bcf/m/mile 2 . The low absolute permeability of the coals (0.5 md) is the main limiting factor for producibility and commercial development of the resource. Even at today's high natural gas prices, these coals are not economically viable.

Chlorine in coal: A review

This review embraces approximately 100 publications on chlorine (Cl) in coal. Topics reviewed in this paper include: (a) historical introduction; (b) some peculiarities of Cl environmental geochemistry; (c) estimation of the Cl coal Clarke value; (d) occurrence of high-Cl coals; (e) mode of Cl occurrence in coal; (f) factors influencing the distribution of Cl in coal; and (g) origins of Cl in coal. 1. The world average Cl contents in coals (coal Clarke of Cl) for hard and brown coals are, respectively, 340 ± 40 and 120 ± 20 ppm. The average Cl content on an ash basis is 1435 ppm which is much more than the Clarke value for sedimentary rocks (150 ppm); hence, chlorine is, on average, a highly coalphile element. Just this alone shows that the authigenic sorption fraction, Clsorb, must be dominant in coals. Aside from “normal” coals with average Cl contents, there are “saline” coals, strongly enriched in Cl, up to 1 wt.% and more. Although there are different genetic concepts, it seems that such coals were mainly formed in epigenesis — when coal beds were influenced by basinal chloride brines (often by hot ore-forming brines, containing also some ore elements such as As, Pb, Zn, etc.). The modes of Cl occurrence in coal are surprisingly varied. Among them are found inorganic salt-like Na and other chlorides, as well as the Cl-bearing silicates, carbonates, sulfides, as well as dissolved chlorides in pore moisture. Organic-associated Cl seems to predominate in coal. It may consist of two different types. One (minor) site (“true” Clorg) may be as covalent-bonded Cl in coal organic macromolecules. The major organic Cl is represented by “semi-organic” Cl, as anion Cl−, sorbed on the coal organic surface in pores and being surrounded by pore moisture. These are HCl-complexes bonded with bases, such as quaternary nitrogen. If Cl in coal is mainly of syngenetic origin, a “true” Clorg form may be of value, and Cl is concentrated in low-ash gelified coal macerals. If coals were submerged by epigenetic impact from basinal brines, Clmin (NaCl and other salts) and “semi-organic” Clsorb forms have to be dominant. In such instances, Cl may be enriched in fusain and in high-ash coals. There is a complicated relationship between Cl-contents in coal and coal rank. On the one hand, the coals subjected to epigenetic brine influence are, as a rule, bituminous coals that have been submerged to considerable depths where basinal brines exist. On the other hand, if coals have a rank higher than low volatile bituminous A (Cdaf more than 86%), the Cl content decreases due to decreasing sorption capacity of the high carbonized coal organic matter.

Coal facies studies in Canada

The present study is a compilation of published data on coal facies studies in Canada based on coal petrological and other methods. The geological age of the coals range from the Devonian coal deposits in Arctic Canada to coals of Tertiary age in the Western Canada Sedimentary Basin, intermontane British Columbia and Arctic Canada. In terms of rank, the coal deposits studied range from lignite to low volatile bituminous. Coal petrological methods include maceral and microlithotype analyses, frequently integrated with data from palynological and geochemical analyses. Most recently, a number of studies have applied sequence stratigraphic concepts to the coal-bearing strata including the interpretation of coal petrological data in the context of this concept.

Adsorption of aqueous heavy metals onto carbonaceous substrates

The present study determines the efficiency with which a range of Australian coals could adsorb a single heavy metal, Cr( iii), which is frequently found in industrial waste streams. The extent of adsorption is measured as a function of pH on a range of coals varying in rank from brown to low-volatile bituminous. In addition, the efficiency with which brown coal could adsorb a variety of aqueous heavy metals is measured. The adsorption results for each of the metal systems are directly compared. The adsorption profiles resulting from this investigation are interpreted in terms of both the solution properties of the metal ions and the ranks of the coals under investigation.

A Comparison of Coal Char Reactivity Determined from Thermogravimetric and Laminar Flow Reactor Experiments

The reactivity of nine different coals ranking from subbituminous to low-volatile bituminous has been studied by thermogravimetric analysis (TGA). At a standard set of conditions a qualitative fuel...

Nitrogen Release during Coal Combustion

Experiments in entrained flow reactors at combustion temperatures are performed to resolve the rank dependence of nitrogen release on an elemental basis for a suite of 15 U.S. coals ranging from lignite to low-volatile bituminous. Data were obtained as a function of particle conversion, with overall mass loss up to 99 % on a dry, ash-free basis. Nitrogen release rates are presented relative to both carbon loss and overall mass loss. During devolatilization, fractional nitrogen release from low-rank coals is much slower than fractional mass release and noticeably slower than fractional carbon release. As coal rank increases, fractional nitrogen release rate relative to that of carbon and mass increases, with fractional nitrogen release rates exceeding fractional mass and fractional carbon release rates during devolatilization for high-rank (low-volatile bituminous) coals. At the onset of combustion, nitrogen release rates increase significantly. For all coals investigated, fractional nitrogen loss rates re...

Burning velocities of multicomponent organic fuel mixtures derived from various coals

In pulverized coal flames, nonuniform mixing and particle dispersion ensure that the products of primary devolatilization are transformed by secondary pyrolysis they burn. This laboratory study shows how the rates of volatiles combustion change during the course of secondary pyrolysis for a spectrum of coal types. Volatiles mixtures are generated in a novel coal flow reactor that independently regulates the extent of secondary pyrolysis. After tars, soot, and char particles are filtered out, oxygen and nitrogen are added to prepare combustible mixtures that have specified fuel equivalence and dilution ratios. Flames are propagated through the mixtures in a combustion bomb to acquire the pressure histories that define laminar burning velocities. Burning velocities of noncondensible volatiles from 4 coals representing ranks from subbituminous to low volatile bituminous are reported for fuel equivalence ratios from 0.4 to 1.5, at two dilution ratios and two unburned gas temperatures. For all coal types, burning velocities triple as the extent of secondary pyrolysis increases from 50 to 100%, in rough proportion to variations in the H 2 levels. This tendency is consistent with conversion of the oxygen and hydrogen in tar into CO and H 2, and of light hydrocarbons into acetylene. For complete secondary pyrolysis, the burning velocities of volatiles from higher rank coals approach the comparable values for hydrogen combustion. But this tendency is not seen with lower rank coals because hydrogen makes smaller contributions to their heating values. Increasing contributions from hydrogen explain the impact of increasing extents of secondary pyrolysis, and different proportions of CO and H 2 determine the variation of burning velocities among different coal ranks. This database is used to develop a correlation based on a scaling from the thermal theory of laminar flame propagation and only two pseudo-components: the actual H 2 and CO levels plus the amounts associated with instantaneous partial oxidation of all hydrocarbons. Provided that flame temperatures are based on actual mixture compositions, this strategy closely correlates a database that covers virtually the entire spectrum of coal types, the last half of secondary pyrolysis, the full range of equivalence ratio encountered in practice, plus two dilution ratios and two unburned gas temperatures. The same scaling is used to assign nominal burning rates from the measured burning velocities, which are found to be up to an order of magnitude faster than burning rates of soot, as expected.

Predicting the evolution of fuel nitrogen from various coals

Nitrogen release from most coal types occurs by three mechanisms: tar shuttling, HCN production from char-N, and combustion of char-N. This modeling study extends FLASHCHAIN to characterize the first two N-release mechanisms for heating rates from 5 to 10 4 K/s, temperatures to 1550 K, pressures from vacuum to several atmospheres, and 13 coals of rank from sub-bituminous through low volatile bituminous. Based primarily on the accuracy of predicted tar yields, the agreement among predicted and observed evolution histories of tar-N, HCN, and char-N and the nitrogen contents of tar is within experimental uncertainty throught this domain. Under conditions of rapid heating, tar shuttling is the only mechanism for nitrogen release as long as tar is being expelled, but for slower heating conditions, it is overlapped by HCN production from char-N. The predictions correctly depict the rank dependence of nitrogen evolution, exhibiting a broad maximum for hv bituminous coals before falling off for low volatility coals. Tar shuttling is almost entirely responsible for this trend. Also, the predicted nitrogen contents of tar increase throughout primary devolatilization as cumulative tar yields grow, in accord with measured values. HCN production from char-N has an extremely broad thermal response that is well represented with a very broad distribution of activation energies. Predicted char-N and HCN evolution histories for numerous coals based on the same energy distribution are within experimental uncertainty of observed levels for several coal types, although indications that HCN production becomes slower for coals of progressively higher rank are also considered.

Combustion of the noncondensible volatiles from various coals

In pulverized coal flames, the products of primary devolatilization are radically transformed by secondary chemistry after they escape into the gas phase, but before they burn. This laboratory study aims to clarify the macroscopic combustion characteristics of coal volatiles, especially the way that burning rates increase as tar is converted into soot during secondary pyrolysis. Mixtures of the noncondensible fuel compounds released under simulated pulverized fuel firing conditions are generated in a novel coal flow reactor that independently regulates the extent of secondary pyrolysis. After tars, soot, and char particles are filtered out, the fuel mixtures are blended with oxygen and ignited in a combustion bomb. Laminar burning velocities are assigned from transient pressure measurements during flame propagation. Burning velocities are reported for (fuel) equivalence ratios from 0.5 to 1.5 at two dilution ratios for noncondensible volatiles from four coals representing ranks from subbituminous through low volatile bituminous. For all coal types, burning velocities triple as the extent of tar conversion into soot increases from 50 to 100%. This tendency is consistent with conversion of all of the oxygen and hydrogen in tar into H 2 and CO, and of all light hydrocarbons into acetylene. The burning velocities for volatiles from the bituminous coal are two-and-one-half times greater than those for the volatiles from the subbituminous coal, consistent with the abundance of oxygen in the subbituminous coal, and its correspondingly higher yield of CO and lower yields of H 2 and hydrocarbons. A correlation for this database is developed from the thermal theory of premixed laminar flame propagation and a generic skeletal mechanism for hydrocarbon combustion. This scaling is also used to assign nominal burning rates from the measured burning velocities. The rates are up to an order of magnitude faster than burning rates of soot. Nominal burning rates also gauge the combined influences of coal loading, rank-dependent yields and heating values, and extent of secondary pyrolysis.

The combustion of individual particles of various coal types

This modeling study characterizes the initial stages of pulverized fuel (p.f.) firing of various types of coal, at the level of individual particles. Noncondensible gases and tars from different coal types are distinguished by different evolution rates, elemental compositions, average molecular weights, and transport properties. Since the gaseous reactants are always hotter than hydrocarbon ignition temperatures, finite-rate homogeneous kinetics are omitted, and volatiles combustion is represented with flame sheets. The combustion enthalpies, flame temperatures, and stoichiometric requirements of the volatiles flames are based on thermochemical equilibrium among 12 species, including primary dissociation fragments. Fuel vapor accumulation between the particle surface and flame is also accounted for. Transient temperatures of particles and flames, flame trajectories, and audits of the heat release from the flames are presented for four coal types: Zap lignite, Ill. #6 bituminous, Pit. #8 bituminous, and Pocahontas low volatile bituminous. Maximum flame temperatures are nearly the same for coals at both ends of the rank spectrum, but significantly hotter for hvA bituminous coals. No single aggregate heat release or stoichiometric parameter identifies the distinctive behavior. Up to two thirds of the heat of volatiles combustion is fed back to the particle for most coal types at typical p.f. firing conditions. When flame temperatures exceed 2500 K, significant portions are also dissipated as recombination energies of dissociated products. The combustion mode shifts from heterogeneous combustion of devolatilization products in “attached” flames to lifted envelope flames at a particle size which is also rank dependent. This size is inversely proportional to the mass-specific heat of combustion of the ultimate yields of gases and tar.

Biaxial vitrinite reflectance in coals of the Elk Valley coalfield, southeastern British Columbia, Canada

Ninety-nine grab coal samples collected from ten different diamond drill-cores from the Jurassic-Cretaceous Mist Mountain Formation in the Elk Valley coalfield in southeastern British Columbia were analyzed petrographically for mean maximum vitrinite reflectance ( R max ), mean random vitrinite reflectance ( R m ) and the lengths of the maximum, intermediate and minimum axes of the reflectance indicating surface or RIS of vitrinite ( R max R int and R min). Coal rank in the coalfield ranges from high-volatile A to low-volatile bituminous. Values of R max in the core samples range from 0.95 to 1.50%. R max , R m , R max , R int and R min are all strongly intercorrelated ( r>0.89 in all combinations). The vitrinite in all samples is biaxial, in most cases biaxial negative. As a consequence, R max is always less than R max, the relationship being R max = 1.044 R max . There is no relationship between degree of vitrinite reflectance anisotropy, as represented by the RIS shape, and rank. The results indicate that a secondary stress field, not perpendicular to bedding, existed during coalification.

A Coal Bed Methane Resource Estimation of the Alberta Basin

Alberta contains approximately 6000 gigatonnes of coal ranking from subbituminous to low-volatile bituminous. The authors calculations show the amount of coal bed gas potentially in place is in the order of 73.5 {times} 10{sup 12} m{sup 3} (2.6 {times} 10{sup 15} ft{sup 3}). This is an enormous resource that is being updated continuously as new data become available. Estimates of the maximum coal gas in place for the United States are about 4 {times} 10{sup 14} ft{sup 3}. In the Alberta portion of the Western Canada Sedimentary basin the coals are distributed throughout the foothills and plains regions and range from Jurassic to Tertiary in age. The potential that these coals may generate sufficient gas to be considered a significant commercial fuel source has only been realized in the last several years. Because of the relative infancy of this resource development in Alberta, only limited direct data are available. The coals in Alberta have not been extensively tested for gas content. However, the evaluation of coal bed methane resources are possible through the use of indirect data such as thickness, rank, and depth, as well as proximate analysis to obtain an estimate of the gas content. This paper reviews themore » formations and geographic areas of gas potential and the reasoning used to derive the coal and gas content resource estimates.« less

Application of FT-IR emission/transmission (E/T) spectroscopy to study coal combustion phenomena

This paper describes the application of a recently described Fourier Transform Infrared (FT-IR) Emission and Transmission (E/T) technique to study coal flames produced in a transparent wall reactor. Comparisons are made for the ignition, soot formation, particle temperature and gas temperature for a number of coals varying in rank from lignite to low volatile bituminous. Samples of chars prepared at different temperatures and demineralized coals were also studied. Flame properties were compared with characteristics of the samples to determine the factors which control flame behavior. A comparison of the ignition of several samples suggests that the rate of ignition correlates with the initial rate of weight loss in air in a TGA experiment at lower temperatures. Ignition of chars is heterogeneous; ignition of high rank coals is homogeneous; but low rank coals exhibit both homogeneous and heterogeneous contributions to ignition. Soot formation in combustion correlates well with tar yield in pyrolysis suggesting that tar is the chief precursor of soot.