Relationship between the technical parameters of cokes produced from blends of three Polish coals of different coking ability

The demand for metallurgical coke for blast furnaces is forcing the coking industry to look for new sources of coking coals. The physical and chemical parameters of coals used in coking blends determine the quality (reactivity and strength) of the finished cokes. This study examines the technical properties of the cokes produced from various blends of three Polish coals with different coking. These coals were collected from three mines: Zofiówka, Szczygłowice, and Krupiński (Upper Silesian Coal Basin, Poland). The coal charges were coked in the laboratory scale, at temperatures of up to 1000 °C, in an inert atmosphere. The coke reactivity (index CRI) and the coke strength after reaction (CSR) were measured and correlated to the properties of parent coals using statistical analysis. The result of this study shows strong relationships between the concentration of the best coking coal (Zofiówka) in the blend and the CRI and CSR of the resulting coke. The CRI and CSR parameters for cokes obtained from single coals and from their blends show the additive character. This study also confirms the linear relationship between CRI and CSR parameters of the cokes.     

Applications of microscopy to coke making

A Canadian perspective of the petrographic, thermal rheological and grade of metallurgical coals required to make coke with high strength and strength after reaction (CSR) properties is presented. The development of automated microscopic techniques to obtain reproducible and reliable petrographic data to predict coke quality is discussed. The amount of “altered vitrinite” in the microscopic coke textures has been used as a reference to quantifiy in situ coal oxidation. Relationships between coke microscopy, coal petrography and thermal rheological data show that FSI can be used to estimate the amount of oxidized vitrinite plus petrographic inert contents of coal. Plastic temperature ranges determined from microscopic examination of the coal/coke transformations for Appalachian and Canadian coals show that standard thermal rheological tests underestimate the plastic range for high inertinite coals.     

A petrologic method of analysis of nonmaceral microstructures in coal

The petrographic maceral composition and vitrinoid reflectance of bituminous coals have been correlated with their carbonization characteristics and are widely used to predict how coals will perform in the coking process and to calculate the strength of the resulting coke. As a result, there is a growing dependence on coal petrographic data in characterizing coals for cokemaking. In addition, there is a growing awareness that there are other nonmaceral microstructures in coal such as material size, shape, association, fracturing, and weathering which should permit better characterization of coals when properly interpreted. These nonmaceral microstructures also give an insight into the metamorphic history and changes due to burial and exhumanation.To expand the use of coal petrologic and petrographic data, a new analytical procedure has been developed that requires the microscopic determination of such nonmaceral microstructures as normal coal, coal fines, pseudovitrinoids, microbrecciation, oxidation, coarse mineral matter, miscellaneous materials, and contamination. The occurrence of one or more of these microstructures in coal, depending on their kind and abundance, may have a significant effect on the coal performance in various processes. This work has resulted in formulation of a technique for determining the nonmaceral microstructures in coal and, if applied as a supplement to the routine maceral analysis of coals, should help in explaining the anomalous behavior of some coals.     

A microscopic study of the combustion residues of subbituminous and bituminous coals from Alberta, Canada

Chars produced by the combustion of a set of three coals from Alberta, Canada, were classified morphologically using reflected light microscopy. Produced chars are different in morphological features, pore thickness, anisotropy and degree of reactivity, because of differences in the vitrinite and inertinite contents.The subbituminous A coal produced the highest percentage of unreactive or slightly reactive components due to its high inertinite content (20.0%), followed by isotropic cenospheres. Isotropic cenospheres, both thin- and thick-walled, and exploded cenospheres are the characteristic chars produced by the high-voltile bituminous B coal, whereas the low-volatile bituminous coking coal produced cenospheres with granular anisotropy (mosaic) on the walls and abundant coke fragmentsOptical microscopy is useful in differentiating the performance of a series of coals during combustion based on petrographic composition and rank and can aid in understanding the relationship between ‘reactive’ and ‘non-reactive’ coal macerals to burnout performance.     

Co-carbonization of selected American coals with commercial additives

Because of the short supply of high-quality coking coals in certain areas of the world, many methods of improving the coking characteristics of poorly coking or noncoking coals have been examined as alternatives to importing more expensive, better quality coals. Co-carbonization, or the addition of coal-derived or petroleum-derived materials to the coal charge prior to carbonization, has been used on a commercial basis in the Japanese coking industry. These additives have been used in both solid and liquid form as binders in coal briquettes or as direct additions to the coal blend.In this study three different coal lithotypes were sampled from each of three United States bituminous coal seams: (1) a marginally coking high-volatile B-rank Illinois No. 6 Seam; (2) a highly fluid, good coking quality, high-volatile A-rank Pittsburgh Seam; and (3) a strongly coking low-volatile Blue Creek Seam. Each lithotype sample was carbonized in small-scale (50 g) charges with each of three additives at 0, 2, 5, and 10% additive by weight. The additives included ASP, an asphalt pitch; KRP, a petroleum residue pitch; and SRC, a solvent-refined coal product. The different lithotypes were sampled to examine the effects of coal type as well as rank. A micro-tumbler test was used to give at least a relative coke-strength value for the cokes produced. In addition, all the cokes produced were examined microscopically to determine the effects of co-carbonization on the coke structure.The Illinois No. 6, Pittsburgh, and Blue Creek Seam coals all showed substantial strength increases when co-carbonized with 2, 5, and 10% of each of the three additives, particularly at the 5 and 10% levels. The SRC appears to be the best additive overall for the three ranks of coal, as judged by its ability to combine with the coal to make a higher strength coke. There appear to be no conclusive coke-strength differences among lithotype samples for any of the three coals, probably because of the small scale of the tests and the relatively small differences in inert maceral content among the lithotypes. Five percent by weight of additive appears to be sufficient, if properly blended with the coal charge, to produce higher strength cokes. This is also probably the maximum economically viable level, particularly in the United States coking industry. Two percent is probably the minimum additive level for adequate mixing on a commercial scale.     

Scientific classification of bituminous coals

Proposals for the new international classification systems of bituminous coals, at present being prepared by the respective U.N. ECE group of experts, presuppose applying the micropetrographic parametes — vitrinite reflectance, as a measure of rank, and inertinite content. These parameters, the utilizability of which is indisputable from the scientific point of view, are not sufficient for a complete characterization of the coal mass properties in thermo-chemical transformations, particularly in the coking process. These proposals, therefore, assume the use of further parameters, specially the swelling index and volatile matter, to eliminate the limitation of the micropetrographic parameters.On the basis of an extensive sampling base of bituminous coals produced in the Ostrava-Karviná coal district (OKR coals), an evaluation was carried out of different parameters characterizing the most important properties of the coal mass and respective classifications were proposed. Selected classification parameters were: vitrinite reflectance, as a measure of rank, associated with the properties of the ordered part of vitrinite macromolecules, the H/O_at ratio, reflecting the properties of their disordered part, inertinite content and coking property, expressed by the swelling index (SI). The scientific character of this classification consists in the fact that it reflects significant physical and chemical properties which can be measured by means of the instrumental techniques available at present and, moreover, that it is associated with coal mass genesis.In order to evaluate coal reserves in seams, this classification has been modified to a less complicated variant, using three parameters, which is applicable to evaluating coal blends for coke production on the basis of expressing the coal-blend composition according to rank.     

煤岩学配煤和焦炭强度预测的研究

用配有自行研制的程序控温仪的显微热台,观察研究了P1、T3两时代煤显微组分的加热性状和焦炭的显微特征,由此揭示了不同时代等变质煤结焦性差异的原因,提出了标准活性组分（Vt,st）的新概念;确定了测定混煤中镜质体反射率的方法;最后以重钢焦化厂大量200kg焦炉试验为基础,用计算机进行数理统计分析,优选出标准活性组分（Vt,st）、镜质体随机反射率（Rran）及其标准差（S）三个参数,建立了能准确定量预测焦炭机械强度的数学模型。经焦化厂使用证实,用该方法预测和控制焦炭强度不但准确度高、简单易行,而且可适用于我国大多数焦化企业由不同煤田的多矿点供煤且常有混煤、煤质不稳定的复杂状况。     

Coal and coke petrographic investigations into the fusibility of Carboniferous and Permian coking coals

For the purpose of conducting coal/coke mass balance calculations ten Australian coals of Permian age and twenty Carboniferous coals from the Ruhr district of Germany have been carbonized, and both feed coal and coke samples have been subjected to petrographic and other laboratory analyses. The results demonstrate that inertinite dissociates thermally into four components: (1) gas and liquor; (2) fused coke matrix (FCM); (3) partly fused coke inclusions (PFCI); and (4) unfused coke inclusions (UFCI). Fluorescence intensity measurements offer the best means of identification of the boundaries between the above groups and, in doing so, divide coal components into fusible, partly fusible and infusible constituents without the need to refer to any maceral classification. Fluorescence intensity cut-offs for the three solid categories have been determined. They correspond to 3% 1 650 w for FCM/PFCI and 1.5% for PFCI/UFCI.     

The role of coal petrographic characteristics in evaluating the non-coking nature of the coals of ramagundam and Kothagudem coalfields,Godavari Valley Basin,Andhra Pradesh,India

The maceral and microlithotype compositions of coals representative of the different coal seams of the Ramagundam and Kothagudem coalfields, Godavari Valley Basin, are compared with those of the Ib River, Talcher, South Karanpura, Hura, and Brahmani coalfields. The vitrite + clarite—“Intermidiates”—durite + fusite + shale (<20%) triangular diagram places these coals in the area of non-coking coals, clearly distinct from the coking and semi-coking coals. The vitrinite reflectance is low (R_ormoil^aver: 0.38–0.71%), far below the coking-coal range. Thus, based on petrographic composition and rank, these coals are of non-coking nature. A triangular diagram is proposed delineating the coking, semi-coking and non-coking coal areas for the Gondwana coals of India.     

Coal for metallurgical coke production: predictions of coke quality and future requirements for cokemaking

This paper reviews quality requirements of metallurgical coke for the blast furnace, coke structure, and relationships between structure and quality. Models of prediction of metallurgical coke quality parameters based on maceral composition and properties of coals being carbonized are summarized. Early prediction models of cold coke strength and the development of second-generation hot-strength prediction models based on parameters as coke reactivity index (CRI) and coke strength after reaction with carbon dioxide (CSR) are assessed. The review concludes with an assessment of current coke production and coal demand in the steelmaking industry, globally, followed by a preview of possible future alternative coking technologies.     

Petrologic studies of terrestrial organic matter in Carpathian flysch sediments, southern Poland

In the Carpathian Flysch, coal is present either as exotics of Carboniferous coal deposits or as autochthonous, thin layers of lustrous coal. This paper present the results of the studies of coal-bearing rocks that are coeval with the enclosing flysch sediments. These coals form lenses up to 0.15 m thick. Their morphology precludes an exotic origin. The main petrographic component is collinite with admixtures of poorly fluorescing telinite. Minor components are: exudatinite, sporinite, fusinite, micrinite and sclerotinite. Mineral matter consists of framboidal pyrite clay minerals and quartz.The random reflectance of telocollinite varies from 0.38% to 0.72%, which corresponds to subbituminous and bituminous ranks. Correlation between chemical analysis, coking properties and relfectance measurements, leads to the conclusion that boundary between subbituminous and bituminous coals should be defined by the following values: C=80wt%, VOLATILES=43wt%; calorific VALUE=32.3 MJ/kg; and R^o=0.56–0.57%.Atypical properties, such as: upper C value (75–80wt%); high volatile matter contents (over 43wt%) and low random reflectance (^o about 0.38–0.57%) in subbituminous coals; low C value (about 80–82wt%); low reflectance (0.56–0.72%); and good coking properties, of the bituminous coals are attributed to quick coalification during increasing temperature as a result of tectonic stress.     

Maceral/ microlithotype partitioning with particle size of pulverized coal: Examples from power plants burning Central Appalachian and Illinois basin coals

Pulverized coals from eleven power plants burning Central Appalachian coal blends and eight power plants burning Illinois Basin coal blends were studied in order to assess the petrographic nature of industrial-scale coal grinding. All coals were high volatile bituminous. Coals were wet screened at 100 (150 μ), 200 (75 μ), 325 (about 40 μ), and 500 (about 25 μ) mesh. Petrographic analysis of the whole coals and size fractions consisted of a combined maceral and microlithotype analysis. Microlithotype analysis, in particular, provides a reasonable approximation of the whole-particle composition at the scale of utility coal pulverization. In the size fractions, duroclarite, the most abundant trimaceral microlithotype, is most abundant in the coarsest fraction and least abundant in the finest fraction. Vitrite, the most abundant monomaceral microlithotype, exhibits the opposite trend. Duroclarite becomes more enriched in vitrinite towards the finer sizes. The partitioning of microlithotypes and the partitioning of macerals within the microlithotypes is indicative of the relative brittle nature of vitrite compared to the hard-to-grind trimaceral microlithotypes. Increased vitrinite in duroclarite is an indication that the microlithotype within the particular size fraction is more brittle than relatively vitrinite-depleted duroclarite in coarser fractions. The relative grindability of microlithotypes will, in turn, impact combustion efficiency.     

Usefulness of petrographic classification in defining national coal resources

The usefulness of coal petrography for assessing and evaluating the properties of coal is well established. Such study is particularly helpful for evaluating Indian coals which are conspicuously heterogenous in nature. In a comparative study on the various schemes of classification and codification of coal using petrographic parameters, the importance of an international petrographic classification has been stressed. In the light of such a scheme—originally suggested for categorising Indian coals using vitrinite and exinite contents and reflectance of vitrinite as parameters—an attempt has been made to define the various important coal deposits of the subcontinent. They appear to be remarkably amenable to national planning from the standpoint of coal utilization.     

武钢使用配煤组成与胶质层粘结系数关系

近几年来,随着钢铁业的发展,工业用煤需求量愈来愈大,但煤质波动较大,致使炼焦质量在同一配比条件之下的配煤也产生不同程度的差异,使焦炭质量明显下降,其Ｍ４０为７６％～７８％,Ｍ１０为８－４％～９－０％。而焦炭的热稳定性,则是导致高炉高产顺行的主要因素之一。目前,武钢高炉碱负荷大约为７～８ｋｇｔ铁,如此高的碱负荷条件下焦炭在高炉中的热稳定性势必受其干扰。十多年来,我们在试验室及跟踪生产研究表明,焦炭在无碱或低碱（＜２ｋｇｔ铁）害的高炉中,焦炭热强度有明显差异。武钢目前生产所用焦炭,在无碱害、１１…     

Coke/carbon reactions in the study of factors affecting coke quality

Pilot-scale and plant cokes with initially different properties were subjected to weight loss by reaction with carbon dioxide, and the resulting products were characterized both microscopically and by ASTM Tumbler tests. The cokes were found to lose strength progressively as weight loss occured, and the examination of carbon forms and microstructures showed the strength changes to be related to the initial properties of the cokes and ultimately to particular compositional characteristics of the coals used to make the cokes. The results have been providing coal-selection guidelines to assist in the manufacture of higher-quality coke. Our coke reactivity test is also being used to signal changes in the coal supply and to monitor certain other coking parameters.     

The Abnormal Condition Analysis used to characterize weathered discard coals

Coal, by its nature, is unstable and weathers when exposed to moisture and oxygen. Weathering can result in a general decline on the commercial value and technological properties of coal. Coals of similar chemical properties have been shown to combust differently, and the differences can be attributed to petrographic composition variations, poor combustion environments, and weathered particles. Stockpiled and dumped discard coals have been targeted for use by a lower power utility, and a novel technique was developed to quantify and qualify the degree of weathering in these coals. The petrographic based Abnormal Condition Analysis (previously referred to as the Weathering Index Analysis) considers features not typically characterized during routine petrographic analyses, but which may have an impact on the technological properties of coals. Discard coals ranging in age from 5 to 40 years where characterized to determine the extent of secondary weathering. Eight secondary weathering features, clearly different from inherent weathering, were qualified and quantified. Margin effect appears to be an early microscopic indicator of weathering, followed by discoloration. Alteration minerals have only been observed in stockpiled and dumped coals and hence could be a useful feature to benchmark when considering whether or not a coal has been stored. Long-term stored coals have microcrack and fissure patterns clearly different from fresh coals. The length of exposure to weathering processes was determined to be proportional to the extent of weathering as determined petrographically. The Abnormal Condition Analysis should be used as a supplement to routine coal petrography as it can assist with the determination of anomalous behavior of coals.     

Application of electron paramagnetic resonance spectroscopy to examination of carbonized coal blends

Paramagnetic centers in two- and three-component coal blends carbonized at 1000 °C were studied by X-band (9.3 GHz) electron paramagnetic resonance (EPR) technique. The blends were prepared from three different Polish coals with carbon contents [wt.%]: 88.66, 86.21, and 82.67, respectively. The aim of this work was to compare EPR parameters and concentrations of paramagnetic centers in the initial and carbonized coal samples. Furthermore the spin–spin and spin–lattice interactions were characterized.EPR spectra were measured with magnetic modulation 100 kHz and microwave power 0.7 mW. Amplitudes and linewidths of EPR spectra were obtained. g-Factors were calculated from resonance condition. Concentrations of paramagnetic centers in the samples were determined. Influence of microwave power in the range 0.7–70 mW on EPR spectra was analyzed.All the studied samples revealed paramagnetism. Unpaired electrons are localized in the same atoms, because similar g-values in the range 2.0035–2.0038 were obtained for all the original samples. The EPR parameters of coal blends were additive in comparison with the parent coals. EPR spectra strongly changed after carbonization of the coal samples. Narrower EPR lines were measured for the original coal samples than for carbonized ones. We detected lower concentrations of paramagnetic centers in carbonized three-component coal blends than in two-component carbonized blends. EPR lines of the studied carbonized blends were not saturated at the microwave power used, which suggests fast spin–lattice relaxation processes in the samples. EPR examination proved chemical interactions between coal constituents during carbonization of coal blends.     

The thermal decomposition studies of three Polish bituminous coking coals and their blends

The objective of this work was to investigate the thermal decomposition of various bituminous coal blends. Three Polish coals of varying rank (82.7, 86.2 and 88.7 wt.% carbon content) and caking ability (weak, moderate and strong) were collected from the Krupiński, Szczygłowice and Zofiówka mines, respectively. These coals were used to prepare binary and ternary blends. Thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) were used. The weight loss and heat flow during pyrolysis, and storage/loss elastic modulus measured as a function of increasing temperature were related to the caking ability of coals. Parameters determined with the TGA and the DSC methods in the binary and ternary blends were correlated with the proportion of strongly-caking-coal concentration in the blend. The weight loss of coal blends was found to be additive parameter. The DSC thermograms of binary blends were found to be different from those of the ternary blends, which suggests a different course for this blend pyrolysis.     

煤岩学在炼焦配煤中的应用：—以宣钢焦化厂原料煤为例

用煤岩学研究方法，对宣钢焦化厂的原料煤进行了煤岩显微组分、荧光和Rr测试，并对其按煤岩学方法配煤，进行了10kg小焦炉试验，结果表明：27号煤可以单煤和部分配煤，所炼的焦炭机械强度M25最高可达85％，M10为10．2％。