Thermogravimetry, coupled with a mass spectrometer (TG-MS) was used to investigate the catalytic effect potassium carbonate (K2CO3) and potassium chloride (KCl), on the char conversion and the product gas limerick of chars derived from a South African inertinite-rich bituminous coal. Sequential leaching of the coal with HCl-HF-HCl was performed to reduce the mineral thing nowadays in the coal. This was done in order to reduce possible undesirable interactions between the minerals and inorganic compounds in the coal during heat treatments. The leaching process essentially reduced the ash content from 21.v% to less than 3%. K2CO3 and KCl [0.5, ane, 3, v Yard-wt %] were loaded to the demineralized coal, raw coal and demineralized coal with added mineral mixture prior to charring. The mineral mixture was made up of kaolinite, quartz, pyrite, siderite, calcite, anastase and hydromagnesite. The 'doped' coal samples were so subjected to heat treatments in a CO2 atmosphere up to 1200 °C. The results obtained showed that both K2CO3 and KCl exhibit a catalytic event on the char conversion during heat treatments in CO2 atmosphere and the char conversion was increased with increasing loadings upwardly to 5 K-wt% of K2CO3 and KCl. The temperature ranges at which conversion occurred were found to be lower for K2CO3 than for KCl. Subsequently, char conversion occurred over a relatively narrower temperature range for K2CO3 than observed for KCl. The catalytic behaviour of K2CO3 and KCl was confirmed by the results obtained. The results also indicated that the catalytic influence of K2CO3 is greater than that of KCl and that KCl is more susceptible to deactivation by minerals and inorganic compounds present in the coal than K2CO3. Different analytical techniques (XRF and XRD) were used to decide the extent of interaction of the catalysts used with the char material in the 5 K-wt% 'doped' coal samples. From the XRF results, information technology was observed that the K2O content was reduced after estrus treatments in CO2, however, no potassium crystalline phases were observed in the XRD results later rut treatments in CO2. The reduced K2O content may be attributed to the potassium been taken upwards in other mineral thing during char reaction with CO2, forming new amorphous inorganic complex compounds. Thus the potassium retained in the sample after rut treatment, indicated by the XRF results, may exist in an amorphous phase. Mass spectrometry (MS) indicated that temperatures at which the maximum rate of evolution of gaseous species occurred were relatively lower for K2CO3 loaded char samples than observed for KCl loaded samples. In addition, no mass-to-charge ratio (m/z) summit at 39 atomic mass unit (amu) from the MS results was observed, indicating that no potassium was detected in the gaseous phases for all the char samples. The undetected potassium in the gaseous stage may exist due to the detection limit of the MS equipment. The MS results also indicated that improver of the catalyst facilitates the evolution of H2 from the coal char samples. Addition of the catalysts to the samples lowered the temperature at which maximum H2 was given off. The shift to lower temperatures was observed with increased catalyst loadings for both K2CO3 and KCl loaded samples.

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The add-on of K2CO3, Na2CO3 and a mixture of the two catalysts showed an increase in the CO2 reactivity of the char prepared from the demineralized inertinite rich bitumious coal at 900 °C in nitrogen. The CO2 reactivity of the char is higher when the catalysts are added to the coal before preparing the char in comparison to addition of the catalyst to the prepared char. The distribution of the catalyst on the char particles thus seems to be better upon improver of the catalyst to the coal (before charring). An added effect could exist the evolution of CO2 during charring that may increment the surface area of the produced char. The surface surface area values of the chars (>400 m2/g) were college than the values for the demineralized coal samples (approximately 150 m2/1000) and the values for the char prepared from the coal with added catalysts increased from 413 to 445 m2/m. XRF, XRD and QEMSCAN analyses were performed to determine the species of K2CO3 and Na2CO3 formed during thermal treatment of the samples. KCl, NaCl, K2O and Na2O are some of the species that were detected.

  • Zhan-Guo Zhang
  • Shigetoshi Hayashi
  • Takashi Kyotani
  • Akira Tomita Akira Tomita

Temperature-programmed desorption (TPD) profiles of HâO-gasified and Oâ-chemisorbed coal chars were investigated with five coals of different ranks. Coals were devolatilized in Nâ and so gasified in HâO at 1100 Chiliad. Initially, TPD of the partially gasified char was determined to 1100 K in vacuo. Later the TPD experiment was repeated after the Oâ-chemisorption at 420 K on the in a higher place heat-treated sample. The precipitous peaks in TPD patterns, corresponding to HâO, COâ, and CO evolution, all resulted from the presence of mineral matter, since no abrupt peak was observed in the TPD patterns of the demineralized coal chars. The gas evolution design from the demineralized char was almost contained of coal type, and all of the demineralized coal chars exhibited near the same gasification reactivities. The relationship between the gasification reactivity and the total amount of COâ and CO development during TPD of gasified chars and Oâ-chemisorbed chars is discussed.

  • Jie Wang Jie Wang
  • Mingquan Jiang
  • Yihong Yao
  • Jianqin Cao

Steam gasification of coal char catalyzed past potassium carbonate was investigated on a laboratory fixed-bed reactor to examine the catalytic furnishings not only on the reaction charge per unit but as well on the reaction selectivity, and non-catalytic gasification of coal char was performed by way of contrast. Information technology was observed that the catalytic gasification of coal char with steam occurred significantly in a temperature range of 700–750 °C, producing a hydrogen-rich gas with slight germination of carbon monoxide and virtually no germination of methane. An oxygen transfer and intermediate hybrid machinery of the catalytic char gasification with steam is proposed for understanding of the experimental data regarding both the kinetic behaviors and reaction selectivity. The study has highlighted the advantages of the catalytic gasification of coal char over the conventional coal gasification with respect to the reaction selectivity. The catalytic steam gasification of coal char makes information technology possible to eliminate or simplify the methane reforming and water–gas shift processes in the traditional gas-to-hydrogen purification organisation.

  • H. Günzler
  • A. Williams

The "Handbook of Analytical Techniques" serves as a concise, ane-finish reference source for every professional, researcher, or student using analytical techniques. All relevant spectroscopic, chromatographic, and electrochemical techniques are described, including chemical and biochemical sensors, also as eastward. g. thermal analysis, bioanalytical, nuclear or radiochemical techniques. Special articles are devoted to full general topics such as chemometrics, sampling, and sample preparation. All manufactures were written and reviewed by acknowledged experts. They cover the fundamentals, instrumentation, and applications of each technique. Numerous references for each article facilitate access to the primary literature. This ii-volume handbook comprises most ane,200 pages with more than 900 figures and has an attractive 2-column folio layout. It is the key source for problemsolving in all areas of analysis, e. g. of nutrient, water, wastewater, air, soil, biomolecules, pharmaceuticals, or for materials characterization. © WILEY-VCH Verlag GmbH, D-69469 Weinheim (Federal Republic of Germany), 2001. All rights reserved.

  • G.P. Huffman
  • Frank Huggins Frank Huggins

An overview is presented of the reactions and transformations of the inorganic constituents of coal at elevated temperatures. Post-obit a brief review of the types of inorganic matter in Eastern and Western coals, reactions and transformations of mineral matter that are of importance in coal combustion are discussed. The importance of ash melting and the utilization of phase diagrams are emphasized in the discussion of slagging behavior and slag deposition. In the section on fouling deposits, emphasis is placed on the reactions of volatile alkalies that give ascent to molten phases (alkali sulfates and brine silicates). Finally, a very brief discussion of the role of mineral matter in other coal conversion processes (liquefaction, carbonization, gasification) is given. Throughout the chapter, the importance of modern analytical techniques (Moessbauer spectroscopy, Ten-ray absorption spectroscopy, computer-controlled scanning electron microscopy) in the analysis of circuitous assemblages of minerals and mineral derivatives is stressed.

  • Harold J. Gluskoter

The term, "mineral matter in coal," refers to mineral phases or species present in coal and also to all chemical elements in coal that are more often than not considered to be inorganic. Most mineral affair occurs in coal as silicates, sulfides, and carbonates. Four coals, separated into serial of specific gravity fractions, have been analyzed. The trace elements, germanium, beryllium, and boron, accept the greatest organic affinities, whereas Hg, Zr, Zn, As, Cd, Pb, Mn, and Mo are generally inorganically combined in the coal. Each of the other trace elements determined plain occurs in both organic and inorganic combination. P, Ga, Sb, Ti, and V are more closely associated with the elements having strong organic affinities while Co, Ni, Se, Cr, and Cu are more than closely associated with the elements having potent inorganic affinities.

  • Sabri Ergun

Kinetics of the reaction of carbon with CO2 has been investigated in the temperature range 700-1400° at atmospheric pressures employing three carbons of dissimilar origin having dissimilar physical backdrop. The following reaction mechanism has been derived: Certain carbon atoms, reaction sites, tin can disassemble an oxygen atom from a gaseous CO2 molecule, reducing CO2 to CO and form an occupied site. Reversely, gaseous CO tin remove the oxygen atom from occupied sites to form CO2: CO2 + Cf ⇄k1k1′ CO + C0. These interactions plant dynamic two-phase (solid-gas) oxidation-reduction and are termed "oxygen-exchange reactions." The carbon transfer from solid phase to gas phase originates from occupied sites: C0 →k3 CO. This is the slowest step of the reactions and can be considered every bit unidirectional. The sorption of CO2 is not a prerequisite pace of the reaction. The reaction rate is proportional to the concentration of occupied sites. CO retards the charge per unit by reducing the concentration of occupied sites. The rate constants k1, k1′ and k3 are functions of temperature only and are mutual to all carbons having trigonal (coplanar) bonds, regardless of origin, particle size, porosity and crystallinity. The differences in the reaction rates of carbons are due to specific number of reaction sites. In studying the validity of the above theory, data obtained in the present study have primarily been utilized. The theory has been found to be applicative to published data likewise. For the beginning time it has been demonstrated that carbons of different origin, particle size, porosity and crystallinity tin exist treated on a common footing.

  • Due east Thousand Stach
  • Th K Mackowsky
  • G H Teichmuller
  • Sfuftgarf

The titleof this volume is atribute to Professor Erich Stach of Krefeld. Germany, who is one of the founding fathers of modern Coal Petrology. In his Original Lehrbuch der Kohlenpefro-graphie he showed, with many illustrations, the smashing merit and facility of examining the heterogeneity of coal with the aid of polished sections and oil immersion objectives. Bully strides have been made in coal microscopy Since publication of the commencement edition in 1935. The current version is a complete new work past a number of authors of international repute, who have made contributions in their specific areas of expertise. In addition, the new edition is published in the English language and, like the original textbook, is profusely illustrated with excdlent photomicrographs and diagrams. The volume is a comprehensive survey of nearly all aspects of coal petrology and since it is at present the just one of its kind, it most cerlainly fillsanimportant gap in fundamental scientific literature. It deals with the discipline matter in five chapters, which accept been written under single authorship or by several authors. with each contributing individual parts. The chapters have the following titles: I) Introduction and historical survey (4 p.); two) Fundamentals of coal pelrology (l p.); 3) Origin d t h eastward petrographic constituents of coal (74 p.): iv) Methods and tools of examination (73 p.): 5) Applied coal petrology (80 p.). Chapter two discusses the origin of coal and the development of coal facies in relation to different peat-forming environments, and how the original vegetable material changes into coal is dealt with under diagenesis and coalification. Of interest also is a comparing between coalification (leading lo coal germination) and bituminization (leading tooil generation). The recently developed views of M. Tdchmuller regarding the formation of oily substances during the coalification procedure are briefly referred to. A large part of Chapter 2 is devoted to detailed descriptions and terminology of the macerals, themicrdithotypes and the lrthotypes of coal equally defined past the International Committee on Coal Petrology. In Chapter iii theindividual coal constituents are related to botanical entities and to specificconditions of peat formation. The alteration of these constituents duringthe peat, brown coal and difficult coal stages is mentioned and illustrated with photomicrographs. Chapter 4 givesan fantabulous survey of the melhods used in preparing the coal for microscopic study; too described are the procedures used tor the quantitative maceral, microlithotype. and mineral affair assay besides every bit for rank determinations. The latter are carried out by vitrinite reflectance measurements, which are dealt with in considerable detail. A section on coke microscopy is included also. For those unfamiliar with coal petrology, the concluding chapter of the book may well be a revelation. It shows how varied are theapplications of these investigations. They range from bodily coal technological processes, such as coal grooming, and the evaluation of suitability of coking coals and their blends lor the product of metallurgical coke, to geological applications. In the latter field, the value of coal petrology for seam correlations and for oil and gas prospecting (through vitrinite reflectance measurements) are discussed in some detail. This volume has coveredthe discipline thing In a most admirable manner and the authors can be congratulated on a job well done. It is modern in concept, contains an all-encompassing and upwards-to-date bibliography, and tin can be recommended for both college students and professionals who desire more information on this comparatively new field of scientific try. Only the high toll is considered a disadvantage tor individual purchases. MS received August 23,1976.

  • A.A. Polyakov
  • P.A.J. Huber
  • S.B. Marston
  • D. K. Zhang

Experimental gasification studies are reported for a highly reactive South Australian depression-rank coal, Bowmans coal, with steam and with carbon dioxide in a single-particle reactor operating at atmospheric pressure and at temperatures between 714 and 892°C. Gasification rate at a given temperature is found to be independent of particle size, suggesting that the gasification rate follows the homogeneous model. The observed gasification rate constants are as follows.For CO2 gasification: For H2O gasification: Information technology is establish that the reactivity of Bowmans coal is far higher than for other coals reported in the literature, because of to its high inherent content of inorganic matter. Acid-washed Bowmans coal has similar reactivity to other low-inorganic-content low-rank coals. Gasification reactivity follows the other Na > G > Ca > Ni with the same anions. The combined result of different cations is establish to be less than for the sum of the individual cations. Heat handling of acid-washed coal prior to ion exchange results in greatly reduced reactivity due to loss of carboxylic functional groups. Reactivity can exist varied past removing or adding active cations. A reasonably good correlation is found to exist betwixt gasification reactivity and full Na + Ca cation content.

  • Christina G. Vassileva
  • Stanislav Vassilev Stanislav Vassilev

Bulgarian subbituminous (Pernik, Bobov Dol) and bituminous (Balkan) coals were gradually heated nether air from 100 °C to their fluid ash-fusion temperatures (1400–1600 °C) via 100 °C intervals and the behaviour of their inorganic matter (IM) was studied. The original minerals and newly formed inorganic phases in the oxidation and combustion products (OCPs) of these coals were identified and the behaviour of 33 minerals and phases was described. The coals studied reveal high detrital affluence and low authigenic mineralization with sulphide–sulphate, carbonate or mixed sulphide–sulphate and carbonate tendencies. The IM of coals is composed mainly of quartz, kaolinite, illite + muscovite, feldspars, pyrite, and calcite, while the other minerals identified have subordinate occurrence. The IM of OCPs includes various pre-existing minerals and newly formed phases. The latter phases are glass, quartz–cristobalite–tridymite, mullite, baggy clay material, hematite–magnetite, anhydrite, and others originating from the heating of these coals or storage of their OCPs. The physico-chemical processes and temperatures that result in the germination of new phases in OCPs are described. The relationships between the ash-fusion behaviour and chemical and mineral limerick of the coals are also discussed. A systematization of the physico-chemical transformations and some comparative characterizations, as well every bit prediction of certain technological and environmental problems related to the behaviour of IM during heating of Bulgarian lignites, subbituminous and bituminous dress-down are also described and summarized.

Coal is a crucial feedstock for Southward Africa's unique synfuels and petrochemicals manufacture and used by Sasol as a feedstock to produce synthesis gas via the Sasol-Lurgi Fixed Bed Dry Lesser (FBDB) gasification procedure. The ash fusion temperature (AFT) gives detail information on the suitability of a coal source for gasification purposes, and specifically to which extent ash agglomeration or clinkering is likely to occur within the gasifier. Ash clinkering inside the gasifier tin cause channel called-for and unstable operation.

Several Spanish chars, ranging from lignite to anthracite, were studied in their gasification with dry air. Their behaviour was essentially related to the rank of the parent coal, and mineral matter content. Potassium was added to the demineralized char both as carbonate and acetate. Reactivity of the supported catalysts thus obtained was increased when K2CO3 was the precursor salt. Yet, this increase was lower, and in some cases at that place was no increase, when potassium acetate was used. The behaviour establish for the two potassium salts, was due to a greater reduction in the area of the char when potassium acetate was the forerunner salt, which brought about a lower accessibility of the reactant gas to the active surface centres. The consequence of K was inhibited in a char because of the loftier silica content of its ashes.

  • D.W. McKee
  • D. CHATTERJI

The reactions that occur in different gaseous environments betwixt graphite and alkali metal carbonates and oxides have been studied past simultaneous thermogravimetry-differential thermal assay and hot-stage microscopy. The catalytic effects of these salts during gasification of graphite in oxygen and carbon dioxide are interpreted on the ground of singled-out oxidation-reduction cycles, involving the intermediate formation of peroxide in the erstwhile case and alkaline metal in the latter. The thermodynamic feasibility of the proposed cycles has been discussed in detail.

Between 1942 and 2010 there were >134 proposed molecular level representations (models) of coal. While they spanned the rank range, bituminous representations are the majority, with far fewer lignite, and very few subbituminous or anthracite representations. They have transitioned from predominantly second pen and paper drawings into 3D computational structures, and have recently increased in complication, and to a limited caste, in calibration. Advances in belittling techniques as well as modeling software, and computation power have resulted in improved partial representations of coal structure. Computer aided design has helped to overcome some of the challenges in model construction for a few models. Yet generally information technology is the capturing of the constitution of coal that remains elusive. Evaluation of physical parameters and behavior observations has aided our confidence in the representations simply models are typically generated for a specific use. No model has faced the gambit of "tests".

  • James Grand. Speight

The Handbook deals with the various aspects of coal assay and provides a detailed explanation of the necessary standard tests and procedures that are applicable to coal in gild to assistance define usage and beliefs relative to ecology issues. It provides details of the meaning of various exam results and how they might be applied to predict coal behavior during use. Emphasis is on ASTM standards and test methods simply ISO and BSI standards methods are included. Affiliate headings are: Coal analysis; Sampling and sample preparation; Proximate analysis; Ultimate assay; Mineral thing; Concrete and electrical properties; Thermal properties; Mechanical properties; Spectroscopic backdrop; Solvent properties; and Glossary.

The catalytic issue of inorganic species, within the ash, on the CO2 gasification of three S African coals containing like carbon-structural properties (elemental, structural and petrographical backdrop) was assessed. The reactivity of the coals with a particle size betwixt 150 and 250μm was adamant in a thermo gravimetric analyser. The reactivity was measured at temperatures betwixt 900 and 1000°C, pressures betwixt 1 and 10bar, and fractions of CO2 between 10 and 30%. For the selected coals, the reactivity decreased with ash content, and was constitute to exist dependent on the limerick of the ash. Specifically, the reactivity increased with calcium and magnesium content and alkali index.

Two South African coals of the same rank and age, but unlike in maceral limerick were subjected to extensive structural analyses. Inertinite-rich Highveld coal (dominated by semifusinite) and vitrinite-rich Waterberg coal were studied to make up one's mind structural differences and similarities. The two coals had similar carbon content (∼84%, dmmf) and vitrinite reflectance (mean-maximum 0.71% for vitrinite-rich vs. 0.75% for inertinite-rich), but differed in hydrogen content (6.23% for vitrinite-rich and 4.53% for inertinite-rich). The inertinite-rich coal was more than effluvious (86% for inertinite-rich and 76% for vitrinite-rich) and more polycondensed (indicated by a higher bridgehead carbon content). The inertinite-rich coal was structurally more than ordered, with a college caste of crystalline stacking. Both dress-down had like boilerplate aromatic cluster sizes (sixteen carbons for vitrinite-rich and eighteen carbons for inertinite-rich) and number of cluster attachments (half dozen attachments for vitrinite-rich and 5 attachments for inertinite-rich). Mass spectrometry showed that both coals consist of similar molecular weight distributions; ranging to approximately 1700 m/z with a maximum abundance of ∼450 m/z for the vitrinite-rich coal and ∼550 m/z for the inertinite-rich coal. Compared to the Argonne Premium dress-down the Southward African vitrinite-rich Waterberg coal was comparable to the coals in the high-volatile bituminous range and inertinite-rich Highveld was closer to the medium- to low-volatile bituminous range. Both coals were surprisingly like in majority label, although inertinite-rich Highveld coal was structurally more ordered, hydrogen deficient, and more aromatic.

Maceral transitions during solvent swelling and extraction of ii South African dress-down similar in rank and age, but dissimilar in maceral composition, were evaluated. Inertinite-rich Highveld coal (dominated by semifusinite) and vitrinite-rich Waterberg coal were used. Maceral-group analysis of solvent-extracted and solvent-swelled residues showed no changes in the maceral composition for both coals. Solvent-extracted residues exhibited meaning observable changes of some particles: particle fracturing, decrease in reflectance and rounding of particle edges. Inertinite-rich coal exhibited extensive fracturing during solvent treatment. Random reflectance analyses of both coals showed that solvent treatment reduces reflectance values of both vitrinite and inertinite. Vitrinite reflectograms showed a shift from the dominant reflecting V-types to lower-reflecting V-types. The inertinite reflectograms exhibited an increase in the number of reflecting inertinite-types (I-types) with solvent treatment, resulting in a broadening of the reflectograms. The changes in reflectance between the original and solvent-treated coal may be attributed to a combination of structural, elemental or surface changes. Electric current data for these South African coals suggests a human relationship between solvent extraction and mean random reflectance: the higher the extraction yields the lower the hateful random reflectance.

  • Ljubisa Radovic Ljubisa Radovic
  • Hong Jiang
  • A. A. Lizzio

Transient (unsteady-country) kinetics, a relatively new technique for studying noncatalytic gas/solid reactions, has been used successfully to further our understanding of char (carbon) gasification. It provides the unique capability of separately determining the reaction rate constant (site reactivity or turnover frequency) and the number of active sites participating in the reaction (reactive surface surface area). Its application to the uncatalyzed gasification of coal-derived chars and polymer-derived carbons is illustrated. In particular, the heretofore elusive quantitative understanding of their reactivity variations with conversion has been achieved for gasification in both carbon dioxide and oxygen.

Thermal beliefs and evolution characterization under designed combustion conditions of thirteen Chinese dress-down of different ranks were investigated by means of thermal assay/mass spectrometry (TA/MS). The experiments were carried out in a constructed air atmosphere (20% oxygen+80% nitrogen) with a menstruation rate of 150 ml min−1 and the samples were heated from 40 up to 1200°C at a abiding heating rate of 10 Chiliad min−one. The volatile products and their evolution profiles against the temperature during the combustion were identified through the on-line recorded mass spectra. The results revealed that the whole combustion procedure could be broadly divided into iv phases and the temperature of the maximum weight loss rate shifted to lower temperatures as the coal rank decreased. In addition to the primary combustion products h2o and carbon dioxide, fragments with the masses m/z 15, 55–sixty, 66, 67 and sulphur dioxide (k/z 64) were also found in the mass spectra.

  • Hong Jiang
  • A. A. Lizzio
  • Ljubisa Radovic Ljubisa Radovic

The gasification reactivity profiles of different carbons (chars) are analyzed from both a theoretical and an experimental betoken of view. The virtues of and/or issues with utilizing the concepts of total surface expanse (TSA), agile area (ASA), and reactive surface surface area (RSA) to explain or predict gasification rate variations with conversion are discussed. An analysis of several models of char gasification kinetics which predict the development of TSA with conversion revealed that the experimentally observed reactivity variations with conversion in carbon dioxide may exist explained using just the initial properties of the char. An experimental investigation of char gasification in carbon dioxide using the transient kinetics approach gave a direct measurement of RSA. Gasification rates normalized with respect to RSA were substantially constant over the entire conversion range. A temperature-programmed desorption technique was also used to determine the amount of reactive surface intermediate formed on these chars during gasification in carbon dioxide; the results were in agreement with those obtained from transient kinetics. The application of these two independent only complementary techniques provided the heretofore elusive quantitative experimental explanation of reactivity variations with conversion for char gasification in carbon dioxide.

Two South African coals similar in rank and age, but dissimilar in maceral composition, were studied using solvent swelling. Inertinite-rich Highveld coal (dominated by semifusinite) and vitrinite-rich Waterberg coal were evaluated for swelling extent and swelling rate using North-methylpyrrolidone (NMP) and CS2/NMP. A finish-movement videography method was adult to written report individual particle swelling behavior. This method immune observation of overshoot and climbing-blazon swelling, equally well as swelling kinetics. Single-particle swelling experiments showed that both coals exhibited overshoot-type and climbing-type swelling. The inertinite-rich coal swelled much faster (in both solvents) than the vitrinite-rich coal. The swelling in CS2/NMP was faster for both coals. Kinetic parameters showed that solvent swelling was governed by relaxation (super-Case II relaxation) of the coal structure. 10-ray computed tomography was conducted over a 50h swelling period in NMP for single particles of each coal. Anisotropic swelling was observed in all the particles (swelling greater perpendicular to the bedding plane than parallel to information technology). The subtle changes in molecular structure, fine structural and concrete differences resulted in meaning differences in solvent swelling beliefs.

  • Ian Glasspool Ian Glasspool

The written report of six bulk coal samples from the Early Permian Vryheid Germination of the Karoo Basin, South Africa has revealed the importance of wildfire in this coal-forming environment. Inertinite is a major elective of these coals and was predominantly produced by wildfire. The accumulation of the peat in this setting was both autochthonous and hypautochthonous/allochthonous, conditions varying between the occurrence of standing h2o and desiccation. Woody gymnosperms and as well lycopods were important components of the coal swamp vegetation, of which the diversity and abundance of the lycopods may be tentatively assessed by the distribution of megaspores in the coals. Consistent with lycopod reproductive strategy, these megaspores are more abundant and diverse where the vitrinite content is greater.

  • C.L. Spiro
  • Jingyi Wong Jingyi Wong
  • F. Westward. Lytle
  • Southward.H. Lamson

High resolution X-ray absorption spectroscopy utilizing synchrotron radiation equally a calorie-free source was used to probe the bonding and structure of potassium in coal and coal-derived products. The potassium sites in coals of various ranks and in the products of thermochemical processing were identified by comparing of unknown spectra with those of a wide range of selected potassium model compounds and minerals. For most dress-down examined, potassium was plant to occur in a site in illite, a layered clay related to muscovite. Such coals included subbutuminous, high and low volatile bituminous, cannel and anthracite types. The lower rank subbituminous and lignite coals prove other forms of alkali, where potassium appears to exist in a noncrystalline environs. Examination of the almost-edge spectra fails to reveal similarities between potassium in low-rank coal and in any organically bonded potassium model compounds such equally carboxylic, phenolic, benzoic, phthalimide or intercalated groups. It is possible that the exchangeable potassium is still inorganically associated on disordered clay surfaces, though this remains equivocal. Thermal treatment of potassium-begetting phases inherent to coals generally leads to formation of a potassium aluminosilicate glass. Samples include those obtained from flash pyrolysis, gasification, laboratory combustion and a large scale pressurized fluidized-bed combustor including bed material, scrubbing hot cyclones, and quench-cooled pins for vapour stage degradation. No potassium sulphates were observed in the deposits.

  • Robert J. Lang

Many alkali metal salts are proficient catalysts for gasification of carbon. Generally, the activity of alkali metal salts increase with the size of the cation, from litium to caesium, simply the associated anion can influence action more than than the cation. It is proposed that some anions can compete with the char for the alkali cations and thus inhibit the formation of an brine-carbon circuitous which is believed to exist the active gasification site. Techniques are described which alter this balance and activate salts which are normally poor catalysts. The activation, by hydrolysis, of relatively inactive chlorides was used to estimate the tendency of the alkalis and alkaline earths to grade carbon complexes. Free energies of formation were adamant and used to explain the inhibiting effects of CO2 in catalysed steam gasification of coal char.

A systematic study of the catalytic activity of brine metallic carbonates on the CO2 gasification of activated carbon revealed the following guild: Li < Na < Thou < Rb < Cs. Outgassing in an inert gas results in a pronounced activity decrease for Cs, whereas the other alkali metals show a slight increase. The activated carbon itself is unaffected. Apparent activation energies for the CO2 gasification are also inverse by outgassing and decrease from Li to Cs. Upon outgassing of the samples, CO2 and CO are released in five distinguishable temperature regions, arising from decomposition of surface complexes and carbonate-similar species, gasification phenomena and reduction of oxidic species. Outgassing patterns of all alkali metals are quite similar. During brine-metal-catalysed gasification in CO2 2 types of oxidic species are nowadays: surface bonded -OM species of high stability and oxidic species having less interaction with the carbon surface.

  • David A. Sams
  • Farhang Shadman

The effect of potassium on the rate of char-CO2 gasification at 800 °C was investigated. The instantaneous rate depends on both catalyst concentration () and the internal porous structure of the solid. At low values of atomic ratio, the charge per unit increases sharply with the addition of goad. Every bit catalyst concentration is increased, the rate starting time levels off so decreases. The levelling off is attributed to the saturation of the surface with catalytic sites. The subsequent subtract in rate seems to be due to the plugging of micropores past catalyst deposits. The reaction charge per unit changes significantly during gasification and drops sharply before gasification is completed. The drop in rate earlier total conversion can exist explained by goad aggregating and pore plugging.

  • J. D. Blackwood
  • A. J. Ingeme

A study was made of the reactions of purified carbon with carbon dioxide ; at pressures upwardly to 40 atm and in the temperature range 790 to 870 tained ; C. The effect of carbon monoxide was examined by adding varying proportions of ; this gas to the carbon dioxide supplied to the reactor bed. At loftier carbon ; dioxide and carbon monoxide partial pressures the rate of formation of carbon ; monoxide is greater than would be expected from the mechanism proposed by Gadsby ; et al. (1948). A mechanism is proposed whereby the increased charge per unit may be ; explained by additional steps involving the interaction of a carbon dioxide ; molecule with an adsorbed carbon monoxide to produce adsorbed oxygen: COâ, ; + (CO) â were ob 2CO + (O). A general rate equatton was derived which ; includes this step and satisfies the experimental results. The reverse mechanism ; by which carbon monoxide tin disappear is non the simple reverse of the forward ; process and at high pressures equilibrium cannot exist expressed by the usual ; expression derived for the simple unmarried-stage reversible process. The possible ; nature of agile sites was examined by studying the reactivity of a series of ; chars prepared at unlike temperatures. The reactivity appears to be related ; to the oxygen content of the chars and the blazon of active centers involved may exist ; different from those which control the carbon-steam mechanism. (auth);

  • Kazuhide Kubota
  • Jianqin Cao
  • Takashi Kyotani
  • Akira Tomita Akira Tomita

The combustion and gasification of 5 coals in air and CO2, respectively, accept been carried out in a wide temperature range between 500 and 1500°C to examine the effects of coal rank and catalysis past mineral matter. Information technology was found that the catalytic effect of mineral matter determined the reactivity of coal in the region where the rate was controlled by chemic reaction. At high temperature where external mass improvidence is dominant, the order of reactivity among five coals decreased with increasing coal rank. Obviously, the chemistry is still of import to some extent in the latter loftier temperature region; the reactivity depends on the type of coal, and in that location is some catalytic issue by mineral species.

  • Richard Lehman Richard Lehman
  • Jefffery S Gentry
  • Nick Grand Glumac

The beliefs of potassium carbonate was studied by thermal analysis near its melting point under 1atm total pressure. Literature data are scant regarding the degree to which K2CO3 decomposes in sub- and pro-liquidus thermal environments, and reliable thermodynamic information are non bachelor for the reaction K2CO3⇌K2O+CO2 in the temperature range of interest. TGA and DTA analyses indicate that pregnant volatilization occurs beneath the melting signal and the logarithm of the rate of volatilization is a linear function of ane/T above the melting bespeak. The outcome of CO2 fractional pressure was highly meaning in reducing, but non eliminating, volatilization nigh the melting point. Graphs of ln[PCO2×weight loss rate] vs. (1/T) were linear, supporting a decomposition model rather than congruent volatilization. The melting indicate of K2CO3, as measured past DTA, is 905°C in CO2 and 900°C in N2.

  • H.H.B. Hagelskamp
  • C.P. Snyman

Three seam profiles from the Highveld Coalfield were analysed for their maceral composition, with special reference to their proportions of vitrinite, low- and high-reflecting inertinite, as well as of massive, detrital and cellular macerals. Distinct circadian patterns can exist delineated, based on the vitrinite content, as well as on the ratios of massive and detrital macerals. The coals consist mainly of detrital macerals and low reflecting inertinite. Information technology is suggested that the coals are hypauthochtonous. Thus they initially formed under good preservation weather resulting in humification and gelification of the major part of the peat. Subsequently the peat was transported and redeposited, so that it was physically disintegrated (resulting in high proportions of detrital macerals) and partly oxidized (resulting in a high ratio of low-reflecting inertinite).

  • Michael J. Veraa
  • Alexis Bell Alexis Bell

A detailed study has been conducted of the effects of LiCl, NaCl, KCl, RbCl, CsCl, KOH, and K2CO3 on the steam gasification of char produced from a western sub-bituminous coal. Initial screening of results revealed that K2CO3 had the greatest catalytic activeness for a fixed cation content in the char. Subsequent experiments were performed to determine the effects of K2CO3 loading and gasification temperature on the rate of gasification and the product-gas limerick. The results show that gasification charge per unit is enhanced with increasing K2CO3 loading and reaction temperature. Increasing K2CO3 loading causes CO to be formed in preference to CO2 and H2 and suppresses the production of CH4. Increasing temperature also causes CO to be formed in preference to CO2 and H2 but enhances the production of CH4. These results are discussed in the light of a machinery to explain the unique catalytic behaviour of K2CO3.

  • Krystyna J. Kruszewska

Maceral, microlithotype and fluorescing maceral content were analysed forth with the vitrinite relative fluorescence measurements. Thirty samples from the Due south Africa Soutpansberg, Waterberg and Main Karoo Basins were investigated. These results were also compared with previously measured vitrinite reflectance values.The application of fluorescence techniques has immune the identification of much college liptinite content (about 5%) every bit compared with the results of routine maceral analysis in white light. Results presented provide an explanation of this divergence, which is caused by difficulties in identifying fine liptodetrinite particles under illumination by the halogen lamp. Therefore, detritic particles of uncertain affinity should be verified under fluorescing calorie-free during routine maceral analysis.The presence and intensity of the fluorescing vitrinite in Southward African coals were also studied. The occurrence of this component is continued with the rank of coal but could be also affected by the facies (sample no. B 35) and in situ coal oxidation (sample no. B 3). The relative fluorescence intensity of vitrinite depends on the rank of the coal only also on its degree of oxidation.It seems also to exist continued with the expulsion of oil which enhances its intensity.The influence of the fluorescing macerals content on some coal properties was proved by the positive correlation between fluorescing vitrinite likewise every bit sum of fluorescing macerals and calorific value (0.66 and 0.74 corr. coeff., respectively). This proves the necessity of fluorescence awarding in routine maceral analysis carried out for coal quality evaluation.

  • Atsushi Ishihara
  • I. Putu Sutrisna
  • Ida Nuryatin Finahari
  • Toshiaki Kabe

Roles of mineral matters and oxygen functional groups of coal on hydrogen transfer reaction with gaseous hydrogen were investigated by using a tritium tracer technique in a fixed-bed reactor system. Mineral matters in coal were removed by HCl or HCl/HF treatments. Brine metals and a role of pyrite were removed by HCl treatment. SiO2 and Al2O3 were removed just past HCl/HF treatment. A large part of pyrite was removed past HCl/HF treatment only almost 20% of them still remained even later on the treatment. It was observed that the efficiency of hydrogen transfer of coal decreased to some extent when cations and mineral matters were removed by HCl handling. Farther decrease in hydrogen transfer was observed after HCl/HF handling. These results suggested that iron species from pyrite may catalyze the hydrogen transfer reaction with H2 gas. Mineral matters assist the H-transfer to the carbon network of coal but does not promote hydrogen transfer to hydroxy groups.

A kinetic characterization of the CO2 gasification of chars from Argentinean low-rank coals, subbituminous (SB) and high volatile bituminous (HVB), is performed by isothermal thermogravimetry. Temperatures in the range 1173–1433 Thousand and CO2 concentrations amid l% and 70% v/v are employed. Experimental data obtained for both chars for the whole range of experimental atmospheric condition explored were satisfactorily described past a single master curve. Reactivity differences between chars are discussed in terms of carbon content, microporosity and crystallinity of the char carbonaceous part. In add-on, potential catalytic effects of inherent minerals on chars gasification reactivity are examined by demineralizing the chars. For the subbituminous char, catalytic effects due to mineral affair content are detected upward to 1333 M, whereas at higher temperatures they become considerably less pronounced. For the bituminous char, reactivity seems to depend more on structural and textural features than on catalysis over the whole range of operating atmospheric condition. Intrinsic gasification rates for both chars are properly represented by the well-known random capillary and random pore models (RPM). Recent models based on modifications introduced to the latter are also applied and kinetic information description is discussed.

  • Klaus J. Hüttinger
  • Roland Minges

Based on a fundamental clarification of the activeness of various potassium salts as precursors for potassium catalysed water vapour gasification in role one of this paper, the catalytic activity was studied past gasification experiments in a fixed bed menstruum reactor using equimolar argon/h2o vapour and hydrogen/water vapour mixtures. The catalytic activities found with the various potassium salts (hydroxide, carbonate, nitrate, sulphate, chloride) characterized past the onset of catalysed gasification and the maximum gasification rates during linear heating (4 K min −1), were found to exist identical with the kinetics of the activation, confirming the post-obit sequence: KOH ~ K2CO3 ~ KNO3 >K2SO4 >KCl. As potassium hydroxide represents the fundamental component in the activation of all salts, the active species has to be formed from this compound. The agile species is divers every bit a non-stoichiometric potassium-oxygen compound KxOy (y < x) with varying oxygen contents. Information technology acts as a dissociation centre for water and transfers the oxygen to the carbon surface, from which carbon monoxide is finally desorbed. A high selectivity towards carbon dioxide found in argon/h2o vapour and a high selectivity towards methane in hydrogen/water vapour are explained past the shift reaction and methanation of primary formed carbon monoxide existence catalysed past the actual active species of different oxygen content. Deactivation of the agile species by sulphur does non occur. There is besides strong irreversible deactivation of the active species by silicates. Inhibition by hydrogen is interpreted by blocking of agile sites at the carbon surface.

  • Teus Wigmans
  • Rien Elfring
  • J.A. Moulijn J.A. Moulijn

In this study a detailed clarification is given of reactivities, selectivities and kinetics in the potassium carbonate catalysed gasification of highly pure activated carbon with low pressures of steam. It is shown that the absolute reactivity increases at increasing initial goad loading and at increasing burn off, the latter leading to a maximum value between 40 and 80% burn off, dependent on the initial loading. The reactivity per unit weight of carbon reacting increases linearly with the goad loading up to 40 weight %, either initially or created by partial gasification. This implies that the catalyst is mobile under reaction conditions. Activation of the catalyst in the region up to 50% fire off is probably due to breaking up of K-O-C bonds. The lack of activity at low catalyst concentrations is explained by intercalate formation, which makes the catalyst inaccessible for the gaseous reactant. The results suggest that both CO and CO2 are principal reaction products from different reaction pathways, in which potassium catalysis is basically controlled by the goad-carbon interaction. The reaction tin exist described past a redox mechanism in which the reduction stride becomes more important at higher catalyst loadings. It is finally shown, that the assumption of h2o gas shift equilibrium is hundred-to-one during the potassium catalysed low force per unit area steam gasification of activated carbon. A Langmuir blazon rate equation appears to be operative with an adsorption constant for water increasing with the catalyst loading.

  • Takashi Kyotani
  • Akira Tomita Akira Tomita

An attempt was made to clarify the reaction of carbon with NO or N2O by using an ab initio molecular orbital theory. This method allows the simulation of the chemisorption procedure of these gas molecules on zigzag and armchair edge sites of carbon. Information technology was plant that NO adsorption with the Northward atom downward is more thermally favorable than the adsorption with the O atom downwardly, while the O downwards mode is more favorable than the N down 1 for N2O adsorption because the onetime procedure releases a stable N2 molecule to form a surface oxygen complex. The chemisorption of NO or N2O with its bond axis parallel to the edge line gave the most stable chemisorbed species. The presence of surface oxygen complexes (quinone-type carbonyl group) on the edge decreases the forcefulness of some bonds in NO- and N2O-chemisorbed species and consequently lowers their thermal stability. Furthermore, the N2 formation process in the C−NO/N2O reaction was analyzed and possible N2 formation routes were proposed. The routes predicted by the molecular orbital theory were compared with the previous experimental results.

Pyrolysis of alternative biomasses, which contributes to the recovery of arid soils and does not compete with comestible biomass, could increase utilise of biomass as feedstock in energy product facilities. In this sense, in order to optimize this thermal process and proceeds meliorate insight the origin and evolution of the principal produced volatiles, nonisothermal thermogravimetry coupled to mass spectrometry (TG/MS) has been practical for samples of two biomasses [Leucaena Leucocephala (Leucaena) and Chamaecytisus Palmensis (Tagasaste)], which find application every bit energy crops and contribute to soil restoration. In a start stage, autocatalytic kinetics has been used in order to obtain the mass loss rate profiles (DTG) of each biomass pseudocomponent (hemicellulose, cellulose, lignin, and extractives) during pyrolysis. In a second phase, the experimental mass spectrometry signals of the main volatiles (CO, CO2, and Water) have been simulated using a linear combination of the previously calculated DTG profiles. The accurate fitting obtained, explains the origin of these volatiles from a uncomplicated volatization process, mainly from lignin. In a 3rd stage, in order to simulate the hydrogen point, it has been necessary to consider the char produced during the volatization process. According to the model, the charring procedure explains close to 77 wt % of the total hydrogen obtained during pyrolysis. Considering the specific char production of each biomass pseudocomponent, it is possible to measure their individual contributions to hydrogen production: hemicellulose, 27.5; cellulose, ix.seven; and lignin, 60.9 wt %, for Leucaena. Taking into account the composition of the samples, the relation between the specific hydrogen productions of the unmarried pseudocomponents (hemicellulose:cellulose:lignin) can be calculated: 3.4:ane.0:7.half-dozen.

  • A. A. Lizzio
  • Ljubisa Radovic Ljubisa Radovic

In this paper, the deactivation behavior of K, Ca, and Ni catalysts during carbon (char) gasification in COâ is investigated. Correlations were sought between gasification rates and reactive surface areas (RSA) of the chars. In addition, the results immune some speculation on recently proposed mechanisms of catalysis. An excellent correlation was found in the case of K catalysis, suggesting the charge per unit-determining step in the overall mechanism to be the same every bit in the uncatalyzed reaction, i.e., desorption of the reactive C(O) intermediate. For the Ca-catalyzed reaction, the quality of the correlation depended on catalyst dispersion, suggesting that an additional process, besides the direct decomposition of the reactive C(O) intermediate, contributed to the transient development of CO (due east.m., oxygen spillover). No correlation was found for Ni-catalyzed gasification; an oxygen-transfer machinery is proposed to explain these findings. Mixed catalyst systems (Ca/Chiliad, K/Ni, Ca/Ni) were as well studied. An fantabulous correlation between reactivity and RSA was observed in cases where the Chiliad-catalyzed reaction was dominant.

Molecular orbital theory calculations and recent high-temperature TPD experiments revealed the feasibility of a new type of active oxygen complex on graphite. This type of complex is formed past bonding of an oxygen atom to a saturated carbon atom (in the caved-in position) adjacent to the unsaturated edge carbon atom that is already bonded to an oxygen atom. Molecular orbital calculation results also evidence that this blazon of complex is substantially more active than the known complexes that accept been discussed in the literature, due east.g., semiquinones and carbonyls. On the ground of this new type of complex, a unified mechanism is proposed for the gasification reactions of carbon with all oxygen-containing gases. The proposed machinery can account for all major features of the published experimental results on temperature-programmed desorption, transient kinetic, and steady-state rate studies of the gas-carbon reactions.

  • HY Cai
  • R. Kandiyoti R. Kandiyoti

Pyrolysis experiments accept been carried out with sets of inertinite graded samples prepared from 2 South African coals (Durban Navigation and Vryheid Coronation Collieries). The furnishings on product distributions of increasing inertinite concentration, and of different heating rates, take been determined. An atmospheric pressure wire-mesh pyrolysis reactor was used during these experiments (1 or 1000 K south(-1) to 700 degrees C with 30 southward holding at height temperature) in guild to minimize reactor related effects on the results. Tar and total volatile yields from the South African samples decreased with increasing inertinite concentration; the decrease in yields were in line with those observed for a set of maceral concentrate samples from a UK coal (Betoken of Ayr) and other Northern Hemisphere dress-down. Total volatile yields showed no detectable deviations when plotted alongside a correlation based on information from 24 Northern Hemisphere derived coals. Relative combustion reactivities of the chars from the pyrolysis experiments have been determined using a standard TGA-based method, every bit a function of inertinite contents of the original samples. The lower rank DNC set showed a rapid drop in char combustion reactivity with increasing inertinite concentration. By dissimilarity, the reactivity of the VCC samples showed no sensitivity to changes in maceral concentration. Information technology seems tempting to accredit this similarity between vitrinites and inertinites of the VCC samples to progressively diminishing differences between macerals of higher rank coals. Clearly, still, many more samples demand to be studied before definitive conclusions can be drawn.

Coal devolatilization experiments are generally conducted separately from char oxidation experiments, and the relationship between the chars generated in the ii types of inquiry is oft ignored. However, char is 1 of the most important products of coal devolatilization and must be characterized equally a function of temperature and heating rate in a way like to that for gaseous devolatilization products. The chemic structure of the parent coal directly affects devolatilization behavior. In this piece of work, the chemical structure of chars from 5 coals of different rank are examined, and implications on char reactivity are discussed. Chars were obtained as a part of residence fourth dimension in a devolatilization experiment (1250 K, 2 X 10(iv) One thousand/s in nitrogen) and just subsequent to devolatilization in a laminar flame-fired experiment (1500 K, five x 10(4) K/s). Quantitative measurements of chemic structure were performed on the coals and chars using C-13 nuclear magnetic resonance (NMR). Results show that the chemic structures of fully-devolatilized chars are very like, even though a wide diversity is seen in the parent coal structures. For example, the average cluster molecular weights of the chars span a range of only 50 amu, and the side-chain molecular weights of the chars bridge a range of only 6 amu. The similarity in chemical structure of fully-devolatilized coal chars suggests that differences in measured heterogeneous char reactivities are caused by differences in the physical structure of the char.