Coal Pitch Research Articles

The introduction of a skin-core structure in mesophase pitch fibers through a successive stabilization by oxidation and solvent extraction

Two-step stabilization, air oxidation, and solvent extraction were applied to introduce a skin-core structure in a coal tar mesophase pitch based carbon fiber. Pitch fiber was first oxidized at 270°C for short periods in air or 10% O 2, successively extracted in a Soxhlet for 15 to 300 min with tetrahydrofuran (THF) or benzene, and then carbonized to 600°C at a selected heating rate (from 1 to 10dgC/min). A distinct skin-core structure was introduced in carbonized fibers of about 10 μm diameter. By adjusting the processing variables, one could sensitively control the skin-core structure without any adhesion remaining between the filaments. The extent of oxidation governed the thickness of the skin and the domain size of the core, whereas the extent of extraction prohibited the adhesion by removing the soluble or fusible fractions in the surface layers, fixing the thickness of the skin that had been oxidatively stabilized. The heating rate to carbonization should be selected according to the extent of stabilization, to prevent adhesion and deformation of the carbonized fibers.

Some petrographic applications to coal, coke and carbons

Petrographic methods have been widely applied in the coking industry especially in predicting coke strength and coke reactivity and to a lesser extent in predicting coking pressure and volume change. Non-maceral microstructure analysis is important in coal characterization; they include various coal types, oxidized coal, brecciation, coarse mineral matter, and miscellaneous materials. The non-maceral microstructure-analysis can be as important, or more important than the maceral analysis in many instances. Coke petrography is a very useful petrographic tool. Different ranks and types of coal produce different carbon forms. Coke petrographic analysis can be used to reconstruct the coal blend and to determine the amount and size of binder and filler phase, and under-coked, burnt coke and depositional carbons. Petrographic techniques have proven important in determining coal tar and pitch quality. The quinoline insolubles can be analyzed microscopically to determine the amount of fine size, low ash material from vapor or gas phase cracking and the amount of material related to coal carryover which is coarser and higher in ash. The tar and pitch quality is often related to the amount and size of the solids. Microscopic techniques have proven useful in the study of composite carbon materials, such as briquettes, electrodes, and “C” cell carbons. As the binder is often optically detectable from the aggregate it can be evaluated in terms of its distribution and wetting ability. Feedstocks also can be evaluated for use in carbon fiber production. Petrography is used in determining the amount, size and distribution of minerals in coal and in grinding studies to determine the degree of liberation of pyrites in coal. It is also used to study feed coals and residues from liquefaction processes. In addition, microscopic techniques are being developed to characterize coal feeds and solid chars or cenospheres produced in combustion. Petrographic data, such as vitrinite reflectance and maceral composition, are used in the International Codification of Coals and is being considered for use in the International Classification of Coals. The use of petrographic techniques is very broad and is developing in scope. The coal petrographer has the tools and, generally, has the background which permits him to expand his analytical repertoire to include many of the diverse applications that relate to coal, coke and carbons.

Transport properties of coal pitches during heat treatment

This work reports measurements of the DC and AC conductivities on two pitches: raw and pyrolyzed, at different temperatures ranging from 550°C to 1000°C. A pseudo-transition insulator-semiconductor is observed on DC conductivity during thermal treatment. Measurements of AC conductivity provide more complex results, the samples being uncompacted powders. A simple analysis is proposed showing that the part of polarization in transport properties is significant enough to be explained. It is found that the correlated barrier hopping model allows us to explain the dependence of the polarization conductivity both on frequency and temperature. In the framework of this model, based on carrier hops between localized sites, the energy W M of the carriers trapped in their sites, and their number N are calculated. A comparison between the number of sites concerned with the electric transport and obtained by electron spin resonance shows, as expected, that the number of free spins is much higher (ratio 10 3−10 6).

Pyrolysis of Polymer Complexes Leading to Air-Stable Ultrafine Metal Particles Uniformly Dispersedin a Carbon Matrix

Abstract New types of air-stable metal-carbon composites which contain ultrafine metal particles (Fe, Co, Ni, Pd, Pt, Rh, Cu, etc.) uniformly dispersed in a carbon matrix were obtained by pyrolysis of a variety of soluble organometallic polymers, macromolecular-metal complexes, and blends of coal pitch with metal complexes at 400-1400°C in N2. Some of their unique physical properties and functions are noted.

A structural study on the stabilization and enhancement of mesophase pitch fibre

The components of coal tar-derived mesophase pitch fibre and its blend with polyvinyl chloride (PVC) pitch were studied for chemical changes after the stabilization. Microanalyses, solubility and solid 13C NMR measurements were performed. The temperature was found to be very influential on the progress of the stabilization. At a temperature of 230° C, PVC pitch enchanced the oxygen uptake of both fusible pyridine soluble (PS) and non-fusible pyridine insoluble (PI) fractions in the pure mesophase pitch, so shortening the time required for complete stabilization and raising more rapidly the softening point of the PS fraction. More oxygen-containing functional groups, such as phenolic, ether, carboxylic and carbonyl groups, were formed in both fractions. It is noted that any increase in the aromatic ring size of the PI fraction is rather limited at this temperature. In contrast, stabilization of PVC pitch at a higher temperature of 300° C, accelerated the increase in PI without accelerating oxygen uptake of both fractions. Hence, the softening point of the remaining PS was unchanged or even lowered. An increase of aromatic ring size of the PI component by stabilization was marked at the higher temperature. Suggested stabilization schemes and the role of added PVC pitch in accelerating stabilization are discussed for each of these temperatures taking account of the above results.

IR-estimation of aromaticity of coal and petroleum pitches

IR-estimation of aromaticity of coal and petroleum pitches

Control of molecular orientations in mesophase pitch-based carbon fibre by blending PVC pitch

Coal tar-derived mesophase pitch and its blends with PVC pitch in 5 or 10 wt% were spun at temperatures from 340 to 390° C by applying pressurized nitrogen. The parent mesophase pitch and the blended pitch showed an excellent spinnability at temperatures from 360 to 380° C and from 350 to 380° C, respectively, to give a thin pitch fibre of 10μm diameter. The transverse texture of the fibres from the parent mesophase pitch showed the radial orientation regardless of a higher spinning temperature of 390° C. In contrast, those from the blended pitches showed random orientation even at the lower spinning temperature of 350° C. The amounts of the blend extruded by spinning at each temperature under 0.2 kg cm−2 G−1 were always larger than those of the mesophase pitch. It is clarified in the present study that blending PVC pitch can realize stable spinning at lower temperatures, where the molecular orientation in the transverse section of the resultant carbon fibre was controlled through decreasing the viscosity of the whole mesophase pitch.

石炭ピッチ系炭素繊維 ピッチ系高強度化へのアプローチ

石炭ピッチ系炭素繊維 ピッチ系高強度化へのアプローチ

Blending mesophase pitch to improve its properties as a precursor for carbon fibre Part 1 Blending of PVC pitch into coal tar and petroleum-derived mesophase pitches

The blending of mesophase pitch with isotropic PVC pitch was studied to improve their properties as a precursor for carbon fibre. PVC pitch prepared at 420° C which remained almost isotropic was found to be miscible with coal tar-derived mesophase pitch without reducing the anisotropic content and spinnability. The tensile strength of pitch fibres remained unchanged by the blending; however, the reactivity for stabilization was enhanced. The resultant carbon fibres from the blend exhibited slightly higher tensile strength. In contrast, petroleum-derived mesophase pitch failed to dissolve the PVC pitch, leaving a number of isotropic droplets. The structural factors of mesophase pitches with regard to their compatibility with PVC pitches are briefly discussed.

X-Ray Fluorescence Analysis of Sulphur and Trace Elements in Coal and Oil Tar Pitches, Asphalts and Other Bituminous Compounds

AbstractA novel windowless sample preparation method is described which allows for X-ray fluorescence analysis of light elements (Z = 13 to 20) in coal or oil-tar pitches, asphalts and other bituminous compounds. The article also discusses blending and spiking of pitches with suitable organometallic compounds in order to prepare a range of trace-element calibration standards. The general instrumental conditions, recommended peak counting times and detection limits are also discussed.

乾式脱硫脱硝用活性コークスの製造に関する研究

Since the dry process for the simultaneous removal of SOx and NOx in the flue gas requires the coke of high mechanical strength, catalytic and adsorption abilities, its preparative procedure was studied . Such a coke has been successfully prepared through the consecutive steps which are fluidized coking of coal into semi-coke, formed coking of semi-coke with coal and soft pitch, and the activation with steam. The optimum conditions for the respective steps were studied to reveal the following conclusions.1) The optimum temperature of fluidized coking was between 480-500 t, semi-coke of highest surface area being obtained.2) Control of the mechanical strength of the active coke can be carried out using the Roga index of the blends.3) The carbonization temperature influenced the strength and reactivity of the coke in a contrary manner, 800°C appearing optimum.4) The activation increased to surface area but reduced the strength of the active coke. The treatment at 900°C for 40 min gave temporarily the best result.SOx adsorption and the catalytic activity for NOx reduction.

石炭および石油ピッチの物性と付着カーボン量の関係

The deposition of carbon on the chamber wall brings many prob-lems to the coke oven operation. In the present paper the amounts of carbon deposi-tion of 24 coals and petroleum pitches were determined by the weight increase of alumina ball in the secondary pyrolitic furnace above the coking furnace with 300g coal charge. The factor affecting the carbon deposition was studied and the following results were obtained.(1) The amounts of carbon deposition of coals and petroleum pitches could not be explained by quantity of volatile matter alone, but proportional to the multi-plied products of that and quality parameter as indicated by carbon contents in volatile matter except CO and CO2.(2) The main source of carbon deposition in volatile matter was considered to be tar, but partially formed from hydrocarbon gas.(3) When coal and petroleum pitch was blended, a similar value of carbon depo-sition was obtained with that calculated from each coal and petroleum pitch.

Carbon fibres, manufacture, use and economy

More than a decade has passed since carbon fibre has been introduced into market. At the beginning, carbon fibre was appreciated bacause of its degree of freedom of form and its flexibility compared with solid carbon/graphite block. Main applications were: heat resistant, refractory or ablative materials. In 1959, rayon based carbon fibre with high strength and high modulus properties was introduced under a tradename of Thornel 25 by Union Carbide Corp. USA. Since then carbon fibre has come into the spotlight as a reinforcing material in the composite for structural usage.Then an intensive research work has been carried out to find the more suitable raw materials for carbon fibre (precursor) in UK and in Japan, Dr. Shindo, Osaka Industrial Institute of Japan has succeded in making carbon fibre from acrylic fibre in 1961. The scientists of RAE (Royal Aircraft Establishment, U. K.) have invented the manufacturing technology of carbon fibre based on PAN (polyacrylonitrile) in 1964. The mechanical properties of them were far excellent compared with that of rayon based carbon fibre. Since then, PAN has established the position of precursor and still the most important precursor for structural use carbon fibre.On the other hand in order to reduce the cost, a number of extensive work has been done to develop carbon fibre based on petroleum pitch or on coal pitch. Nowadays high performance carbon fibre based on pitch is industrialized by Union Carbide and also general purpose carbon fibre based on pitch has been commercialized by Kureha Chemical Co, Japan.With regards to the applications, high performance PAN based carbon fibre paves the way for reinforced resin structural materials for aerospace applications. With an increasing performance requirements from aerospace industry, carbon fibre is moving to the second phase in terms of its properties to meet these requirements. A new generation type of carbon fibre is now under development by a number of manufacturers.In this paper, the trend of carbon fibre including its characteristics applications and market estimation are reviewed.

Some aspects of the surface chemistry of coal, kerogen and bitumen as revealed by ESCA

The application of ESCA (electron spectroscopy for chemical applications) to the study of the structure, bonding and reactivity of coals, kerogens and bitumen samples has been examined, with particular reference to torbanite, vitrinite, kimmeridge kerogen, brown coal and Gilsonite pitch. The ESCA valence band spectra and C l s band profiles of a rank rangeof coal samples are discussed. Differences in C l s signal between naturally occurring heat altered coal and the unaltered coal are reported. The surface sensitivity of the ESCA experiment reveals enriched silicon and aluminium concentrations on the cleaved surfaces of grahamite bitumen, relative to bulk ESCA analyses. Surface oxidation of anthracite through atmospheric weathering is found to be amenable to study by ESCA and substantial oxidation of the coal occurs after an exposure period of one week. Artificially induced oxidation by means of low power radiofrequency oxygen plasma treatments have been performed. In the case of Gilsonite pitch the distribution of oxidized carbon functionality is found to differ from that reported during the irradiation of Gilsonite in u.v. light (254 nm) in air.

ESCA applied to aspects of coal surface chemistry

A recent evaluation of the surface sensitive analytical technique, Electron Spectroscopy for Chemical Applications (ESCA), in the analysis of coal, kerogen and gilsonite pitch is reviewed. The ability of ESCA to provide structural information on the materials as studied in their solid state is demonstrated. Comparison has been made of ESCA-derived atomic concentrations with corresponding data from standard elemental analyses for a series of well documented coal samples (Lower Kittanning seam, Ohio and Pennsylvania, USA). For organic oxygen atomic concentrations, ESCA-derived values are shown to be consistently higher than bulk data obtained from the Pennsylvania State University Coal Bank. A rankdependent trend has been noted for the organic oxygen data set, the coal of lowest rank showing the most deviation from a one-to-one, ESCA to bulk relationship. The ability of the ESCA experiment to monitor changes in surface chemistry has been clearly demonstrated with reference to the interaction of gilsonite pitch with u.v. light. Under the mild conditions employed, ESCA was able to detect extensive surface oxidation of both the carbon and sulphur components. Thus the combined use of ESCA and other analytical techniques holds considerable promise in studies of the structure and reactivity of coal and coal-related materials.

Identification of sulphur heterocycles in coal tar and pitch

The direct application of gas chromatography with a flame photometric sulphur detector and mass spectrometry to the identification of sulphur heterocycles in coal tar and pitch without the need for prior separation of a sulphur-rich fraction is described. Accurate mass measurement has allowed the assignment of atomic compositions to the sulphur heterocycles with little ambiguity, despite their presence as minor components in a complex aromatic mixture. Single ion chromatograms and retention indices calculated relative to aromatic hydrocarbons have been used to correlate the mass spectral identifications with the sulphur-selective gas chromatograms.

Microanalytical Characterization of Mineral Impurities and their Effect to Graphitizability of Brown Coal Pitch Cokes

AbstractThe main impurities in brown coal pitch cokes are Si, S, Ca, Fe, Al and Mg. Microanalysis exhibits that these elements besides sulphur are localized in non‐carbonaceous particles which are identical with the mineral impurities in the pitch precursors. Sulphur is present both in sulphate particles and as “organic” sulphur in the carbonaceous phase. The impurities reduce optical anisotropy and graphitizability of electrode cokes. Crystallite size and xylene density were measured to characterize the graphitizability.

The Influence of Mineral Impurities on the „Sulphur Puffing”︁ at High Temperature Treatment of Brown Coal Pitch Cokes

AbstractCokes rich in sulphur usually show throughout the high temperature treatment between 1500 and 1800 °C an irreversible dilatation which can be suppressed by additives of inorganic oxides or salts. In brown coal pitch cokes with high content of sulphur and mineral impurities (ash), however, this suphur puffing cannot be observed. Basic ash components (e. g. CaO, Fe2O3, MgO) are responsible for the puffing inhibition. The inhibition is already sufficient if the concerntration of basic ash components equals the suphur conentration.

Occupational Cancer Control Policy

OR decades, science writers have referred to the "mystery" of cancer. This regrettable characterization is, at f7 _ 2best, half true, reflecting the utter confusion between g cause" and "cure" with respect to cancer. There is, indeed, a great deal of mystery as regards the search for (K#*4s) effective cancer cures. In fact, during the past twenty years of intensive pursuit of cancer cures, the survival rates for the most common types of major cancers-lung cancer, breast cancer, and cancer of the colon-have remained almost unchanged (1). But what about the causes of cancer? Here, there is less mystery. Actually, our accumulated knowledge about the causes of cancer is very impressive, stretching back over 200 years. In 1775, a London physician, Percival Pott, first noted the apparent connection between exposure to coal soot among chimney sweeps and the subsequent high incidence of cancer of the scrotum among the young boys compelled to do this terrible work. Dr. Pott postulated that this malignancy, which was so common among chimney sweeps, must be attributable to the soot amassed on and within their bodies. The perceptive doctor was absolutely right, but it wasn't until this century that scientists isolated one of the cancer-causing chemicals present in coal soot-benzo (a)pyrene, the same substance that contaminates the air in many large cities and is deemed partially responsible for excessive rates of lung cancer among urban dwellers. In 1822, another English physician, J. A. Paris, identified the connection between arsenic and skin cancer, a cause-and-effect relationship that is beyond dispute today. By the end of the nineteenth century, with the onrushing advance of the modern Industrial Age, scientists and physicians were just beginning to recognize the chemical origins of cancer: skin cancer among workers in the Scottish shale industry; cancer of the lip, larynx, and lung among workers handling coal tar and pitch; lung cancer, liver cancer, and bone cancer among miners of radioactive ore. In the 1930S

Pitch and petroleum coke additions to coke oven charges

AbstractSeveral pitch materials and a petroleum coke were added to coke oven charges in an attempt to make good metallurgical coke from Canadian coal of poor coking quality. Coal and petroleum pitches were added to a low fluid western Canadian coal of medium volatile bituminous rank, and the blends coked in a technical‐scale moveable wall test oven having a 230‐kg charge capacity. Pitches improved coke tumble test indices, the principal coke quality parameter related to blast furnace performance. Varying levels of petroleum coke were added to an eastern Canadian coal of high volatile bituminous rank, and the blends, some partially briquetted, were carbonized in a test oven. Tumble indices of coke from the partially briquetted charges approached an acceptable level. These investigations confirm that petroleum products as well as coal derivative can play a useful part in the production of a metallurgical strength coke from poor or non‐coking coals.