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Analysis by Fourier transform infrared (FT-i.r.) spectroscopy of coals and their extraction products, i.e. extracts and residues, gives an insight into the chemical structure of the initial material and changes due to the separation procedure. High quality spectra are obtained for solids by diffuse reflectance FT-i.r. spectroscopy. They also provide rather broad overlapping bands which have to be...
Three coals of different rank (R 0 = 0.58-1.01%), and the lithotypes and macerals separated from these coals, were analysed in this study. The wet chemical technique was used to determine the distribution of sulfate, pyritic and organic sulfur forms in the coals and lithotypes. The morphology, size and mode of occurrence of pyrite were examined by optical microscopy and scanning electron...
The high temperature reaction of SO 2 with CaO was investigated in three reactors: a thermogravimetric reactor (TGA), a volumetric reactor (VR) and an entrained flow reactor (EFR). Several natural limestones with super fine particles were used as sorbents. It was found that the reaction could be well characterized by a two-stage process. The initial stage was very fast and lasted about...
The objective of this work was to study the effect of coal air oxidation on char gasification reactivity. Three bituminous coals with different rank, from a low volatile bituminous coal to a high volatile C bituminous coal, were used. Isothermal runs were carried out in air, using particle sizes ranging between 48 and 855 μm. The experimental results showed that char reactivity increases with degree...
The porosity, BET surface area and desulfurization reactivity of samples of CaO obtained by calcination of Ca(OH) 2 at 1000°C in a gaseous atmosphere containing different amounts of SO 2 are reported. Small amounts of SO 2 ( 50 ppm) increase the surface area and porosity of the CaO relative to those obtained without SO 2 . The desulfurization reactivity of CaO produced...
The properties of chars derived from coals of a wide range of rank produced in wire-mesh (WMR) and entrained-flow (EFR) reactors were compared. The WMR was operated at atmospheric pressure of helium or nitrogen with heating rates of 2-5000 K s -1 , temperatures up to 1773 K and residence time of 2-30 s. The EFR was operated at 1273 K with a residence time of 1 s in nitrogen at atmospheric...
Two coals (Beulah, PSOC-1483, and a Thai coal, TH23) of unusually high reactivity with hydrogen and tetralin were shown to contain significant methoxy group contents. The fate of the methoxy groups when these coals were reacted under N 2 at 320 o C (with and without added decalin) and with H 2 -tetralin and H 2 SnO 2 at 405 o C was studied. The reactions...
Two coals (Beulah, PSOC-1483, and a Thai coal, TH23) of unusually high reactivity with hydrogen and tetralin were shown to contain significant methoxy group contents. The fate of the methoxy groups when these coals were reacted under N 2 at 320°C (with and without added decalin) and with H 2 -tetralin and H 2 -SnO 2 at 405°C was studied. The reactions of TH23 coal...
Changes in the combustion reactivity of sets of chars from five coals have been determined as a function of increasing devolatilisation temperature, heating rate and pressure. Chars were prepared in wire-mesh pyrolysis reactors, where evolving volatiles are rapidly removed from the vicinity of the heating coal. Samples were heated at rates between 1 and 5000 Ks -1 to temperatures up...
Reactivity profiles are defined and measured with thermogravimetry for a dense metallurgical Longyear coke, a polymer-derived porous active carbon, Carboxen 1000, and three flame-chars, Illinois #6, Pittsburgh #8 and New Mexico Blue #1. For each sample it is found that the reactivity profile can be separated into a chemical kinetics expression and a structural profile describing reactivity evolution...
A thermogravimetric method was used to study the behaviour of seven pulverized commercial coals during the first instants of their combustion and devolatilization and combustion of the corresponding chars. Their weight variations are related to the evolution of the surface characteristics of the carbonaceous materials. In particular, BET surface areas of the chars appear to be strictly related to...
Carbon reactivity was measured in two entrained flow reactors, two drop tube furnaces and one fluidized bed. The results were interpreted by using three shrinking-core models. A number of minor differences between the models were identified and the resulting deviations could mostly be ascribed to non-measurable parameters such as particle specific heat capacity as a function of temperature, boundary...
The reactivity of Kansk-Achinsk brown coal in thermochemical conversion with tetralin is a linear function of the network flexibility, which is primarily controlled by ionic cross-linking with carboxylate bridges via polyvalent cations such as Ca 2+ .
A relative estimate of the reactivity of calcium sulfate in a number of coal combustion ash samples was obtained, using the rate of solution in water as a parameter. Measurements were also performed on standard samples of calcium sulfate prepared in different ways, for comparison. The temperature of previous treatment appeared as the most important factor determining the reactivity of CaSO 4...
A diffractometric method is proposed which characterizes coal as a heterogeneous system . The method represents an alternative to microscope-based petrographic analyses. A high-volatile bituminous coal was chemically and petrographically characterized. It was then demineralized and separated into its main organic fractions on the basis of density. The coal as a whole and its organic constituents...
The thermal cracking of benzene, toluene, diphenylmethane, biphenyl, diphenyl sulfide, diphenyl ether, phenol and dinaphthol was studied in the presence of inert gases, methane, methane-hydrogen mixtures and Cu-Beta, H-Beta and Cu-ZSM-5 catalysts at various reaction temperatures (350-480°C), pressures (3.5-9 MPa) and times (1-4h). For some systems methane assists conversion by either methylation...
Experimental gasification studies are reported for a highly reactive South Australian low-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...
Relationships between char preparation conditions and CO 2 -gasification conversions have been examined using a wire-mesh, a fluidised-bed and a ‘hot-rod’ (fixed-bed) reactor. Conversions from the direct gasification of untreated coal have been compared with those from the gasification of chars prepared: (i) in-situ under helium in each reactor, before switching over to CO 2 ; and...
Three vitrinite-rich coals, two South African and one Polish, were examined. In all three cases collotellinite dominated over other macerals. The detailed microscopic observations revealed a close relationship between this maceral and slitted particles known as pseudovitrinite. To test the carbonizing ability of pseudovitrinite, two coking coals and one highly volatile coal (a component in coking...
A laboratory investigation into the effect of inorganic matter on spontaneous combustion behaviour of a Victorian brown coal. Fourteen samples were prepared, namely, the raw coal, water-washed coal, acid-washed coal, and acid-washed coal doped with 11 additives. Each of the samples was then tested in an isothermal reactor to obtain its critical ambient temperature, above which spontaneous combustion...
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