This paper describes the application of matrix assisted laser desorption ionization (MALDI) to coals and coal-derived materials using sinapinic acid as the matrix. The mass range of molecules in coal and coal-derived materials has been extended by a factor 100 compared with prelaser desorption mass spectrometric measurements. A peak of intensity is observed for coals and coal-derived materials in the mass range 1000–5000 u which is sample dependent. The upper mass ranges of the spectra vary according to sample, ranging from over 260 000 u for Point of Ayr coal and 200 000 u for a coal tar pitch, to 20 000 u for a maceral concentrate liquefaction extract. These results confirm earlier results using laser desorption mass spectrometry and are in broad qualitative agreement with size exclusion chromatography results. Detailed quantitative agreement, however, requires further work. The implications of this work for the debate on coal structure and models of coal conversion are considerable.
The use of cattle manure (referred to as feedlot biomass, FB) as a fuel source has the potential to both solve waste disposal problems and reduce fossil fuel based CO2 emissions. A co-firing technology is proposed where FB is ground, mixed with coal, and then fired in existing, pulverized coal-fired boiler burner facilities. A research program was undertaken in order to determine (i) fuel characteristics, (ii) combustion characteristics when fired along with coal in a small scale 30-kWt (100,000 BTU/h) boiler burner facility, and (iii) combustion and fouling characteristics when fired along with coal in a large pilot scale 150-kWt (500,000 BTU/h) DOE-NETL boiler–burner facility. Part I presented a methodology for fuel collection, fuel characteristics of the FB, its relation to ration fed, and the change in fuel characteristics and volatile oxides due to composting. Part II addresses the pyrolysis characteristics of coal, FB, and blend and presents results on the performance of 90:10 coal:FB (PC) blend as fired in a 30-kWt boiler–burner unit. The boiler–burner unit is made of steel and lined with a cast ceramic liner for long duration operation and a commercial feeding system is used for firing the coal and the blend. Thermogravimetric analyses (TGA) performed on coal, FB, and 90:10 coal:FB blend reveal that biomass will start releasing gases at 273 °C (523 °F) which is about 100 °C (212 °F) lower than that of coal. The maximum rate of volatile release is about 0.000669 kg/s kg for FB while that of coal is 0.000425 kg/s kg. The experiments revealed that the 90:10 blend burns more completely in the boiler, due to the earlier release of biomass volatiles and higher amount of volatile matter in FB. The NOx emission for coal was 290 ppm, 0.162 kg/GJ (0.3768 lb/mm BTU) and 260 ppm, 0.1475 kg/GJ (0.343 lb/mm BTU) for the 90:10 blend at 10% excess air. Even though the effective N content of the blend increased by 18%, compared to coal the NOx emission decreased which is attributed to the higher VM of FB and more N in the form of NH3. However, due to limited residence time and higher VM, the CO emission increased from 15,582 ppm, 5.29 kg/GJ (12.305 lb/mm BTU) to 22,669 ppm, 7.81 kg/GJ (18.16 lb/mm BTU) when fuel was switched from coal to 90:10 blend. Large scale pilot plant tests performed at the 150-kWt facility (DOE-NETL) reveal increased falling potential for the blend compared to coal (Part III), emissions were negligible.
The cost of maintaining aeroplanes is still considerable. It concerns especially operation cost where fuel is a substantial part. At the moment the special 100LL gasoline is used to fuel aircraft piston engines. It is about 20% more expensive than ES95 gasoline featuring comparable properties.The article shows the results of test-bed research conducted on the radial piston aircraft engine fuelled by aircraft 100LL gasoline and automotive ES95 gasoline. The object of research was ASz-62IR engine by WSK PZL-Kalisz that was equipped with an experimental fuel injection system. Power, fuel consumption, head temperatures and indicated pressure in cylinders were analysed in the selected typical operating points. The testing was carried out in steady state. It was proved that it is possible to exchange fuels with no engine power loss and merely an insignificant increase of fuel consumption but with significant increase of IMEP cycle-to-cycle variation.
Measurements were made of the reaction rate of three sizes (2.9, 0.9 and 0.22 mm) of petroleum-coke particles with carbon dioxide over the temperature range 1018–1178 K, and at carbon dioxide partial pressures between 26 and 118 kPa. A limited number of similar measurements were made on samples of a commercial aluminium-smelting anode, an experimental anode, and AGKSP graphite. The materials were all reacted under conditions of chemical rate control alone: there were no rate limitations due to transport processes without or within the carbon particles. The order of the rate with respect to carbon dioxide concentration was found to be close to 0.6 for the petroleum coke and anode carbons, and between 0.6 and 0.8 for the graphite. Activation energies in the range 203–237 kJ/mol were found for petroleum coke; 187–237 kJ/mol for electrode carbon; and 293 kJ/mol for the graphite. For the petroleum coke, the order was found to be constant up to 45% burn-off and the activation energy essentially constant between 21 and 45% burn-off. The reactivity ϱs, based on unit pore surface area of the petroleum coke at a carbon dioxide pressure of 101 kPa, can be represented by: . For the 2.9 and 0.9 mm particles, α = 6.1 /sx 106 g/m2 min and E = 215 kJ/mol; for the 0.22 mm particles the respective values are 1.8 /sx 107 and 222. The reactivity ϱ of the commercial electrode on a weight basis was within the range of those of the coke and experimental electrode. For AGKSP graphite, values of ϱs were close to those found by Walker and Raats14.
The significant changes of surface texture in CaCO3 crystallites due to reaction in an equimolar SO2O2 mixture were examined by scanning electron microscopy. Surface modifications were extensive above 870 K, which is close to the temperature of CaCO3 dissociation and of CaSO3 oxidation. It appears that both rate processes participate in the conversion of calcite to CaSO4 by reaction with SO2 under oxidizing conditions. The results confirm the production of sulfate above 870 K, but this generation of product across the surfaces represents a barrier to gas-solid contact that prevents complete reaction of the CaCO3 particles. The observations show that potassium ions enhance CaSO4 formation, probably by promoting fusion of the barrier layer, and that rapid heating does not disrupt calcite crystals sufficiently to increase the reactant surface area. The product barrier layer is identified as controlling both rate and extent of the reaction of calcite in desulfurization processes.
This paper presents the results obtained for the operation of a 10 kWth chemical-looping combustor using a South African coal as the solid fuel and an oxygen carrier of ilmenite, a natural iron titanium oxide. A chemical-looping combustor for solid fuels was designed and built. It consists of two interconnected fluidized beds, an air reactor where the oxygen carrier is oxidized and a fuel reactor where the coal is gasified by steam and the syn-gases react with the oxygen carrier. A constant coal flow corresponding to a thermal power of 3.3 kW was introduced into the fuel reactor. The tests were conducted at temperatures above 850 °C and for a total test duration of 22 h. The particle integrity of ilmenite and the particle circulation between the two reactors were investigated and verified. The effects of particle circulation on coal conversion, gas conversion of the fuel reactor and carbon separation or CO2 capture between the air and fuel reactors were investigated. The actual CO2 capture ranged between 82.5% and 96% while the gas conversion from the fuel reactor was in the range 78–81%, based on measurements of unconverted CO and CH4.
The chemistry of tin added in various forms as catalyst in the liquefaction of Victorian brown coal was determined by 119Sn Mössbauer analysis. After 60 min hydrogenation at 380 °C and 6 MPa initial hydrogen pressure, tin was principally distributed between β-Sn, SnS and SnO2. No significant dependence of liquefaction yield on the initial tin compound was apparent. The results extend earlier work and support the previous conclusion that elemental tin is the important species for promoting hydroliquefaction in these systems.
Boron and its compounds are environmentally hazardous substance and are well-known condensed products that appear in coal fly ash during combustion of coal in coal-fired electric power stations. In a previous study, we suggested that boron in coal fly ash obtained from Nantun coal in China, identified as Ash–N, may exist on the surface of relatively large coal fly ash particles or as very fine particles generated by homogeneous nucleation. Although the characterization of boron in coal fly ash is important for its effective stabilization or removal, its detection is quite difficult because of its low concentration in coal fly ash and its light atomic weight. In the present work, solid-state magic angle spinning nuclear magnetic resonance (MAS-NMR) technique has been applied to reveal the local chemical structures of boron in Ash–N. In the 11B MAS-NMR spectrum of Ash–N, two peaks which are attributed to a three-oxygen coordinated boron unit (BO3) and a four-oxygen coordinated boron unit (BO4) were observed with high resolution. We have estimated quadrupole parameters of the BO3 unit in Ash–N using computer simulation, and we have fingerprinted these moieties with the parameters of borates. The result of the present analysis shows that calcium- or magnesium-bearing orthoborate or pyroborate are the most likely forms of boron in Ash–N.
The chemical characteristics of fly ash samples from combustion of three fuels: coal, peat and wood chips, have been studied. The ash materials were collected in the 12 MW CFB at Chalmers University of Technology during full load combustion with similar standard combustion parameters. The samples were characterized in terms of chemical composition, mineralogy and leaching behavior. The special characteristics of the mineral matter in each fuel were reflected in the leaching results. Upon reaction with moderate amounts of water secondary mineral phases such as ettringite and calcite, were formed. These compounds were shown to affect the leaching rates for calcium and sulfate as well as the pH of the leachates.
Carbon-13 Nuclear Magnetic Resonance Spectroscopy has been applied to coal-derived liquids in order to obtain additional information regarding molecular structure and composition. The data have demonstrated that, although the chemical structure is extremely complex, a significant amount of material is present in the form of normal paraffinic material both as free paraffins and alkyl substituents on aromatic and hydroaromatic materials. Semiquantitative estimates are made of the alkyl content of the liquids and the atom percentage of this material that must exist in the unprocessed coal.
Optimum experimental conditions for a quantitative n.m.r. analysis of oil products are given together with the expected degree of repeatibility and accuracy. Conclusions are drawn regarding the possibility of using characteristic shift ranges to recognize structural features of chemical importance. In this respect aromatic carbons may be subdivided into four categories: protonated, methyl-and alkyl-substituted, and condensed (polyaromatic and benzonaphthenic carbons). A method is suggested to estimate approximately the aliphatic and naphthenic saturated carbons.
Carbon-13 chemical shifts are reported for tetralin, hydrophenanthrenes and hydropyrenes and their alkyl substituted derivatives. Mono- and di- plus tri-aromatic fractions of hydrogenated phenanthrene and pyrene were also examined by carbon-13 n.m.r. and, wherever possible, the components in them identified.
The n.m.r. methods described previously are tested upon a synthetic base oil made up of a mixture of alkylbenzenes, and are then applied to five heavy ends derived from the same Arabian Light crude oil. The computed structure parameters show a regular increase of the aromaticity factor and of the aromatic and naphthenic condensation degree from the middle distillate (gas oil) to the heavy residues (vacuum residue and asphalt).
13C n.m.r. spectra of kerogen concentrates isolated from several different subbituminous to high-volatile bituminous coal macerals have been obtained by a combined cross polarization/magic-angle spinning technique. The samples comprise three vitrinites, two sporinites, two alginites and one fusinite, all of Upper Paleozoic age. It is shown that this technique can be used to differentiate the maceral types by providing characteristic spectral fingerprints. Aromaticities decrease in the order fusinite vitrinite sporinite alginite, as expected with the rank range studied. Furthermore, fine spectral details provide general information on the nature and distribution of discrete structural moieties and their variations with both type and rank.
The gasification of carbon-13 doped with nitrogen was used as a model for coal char gasification. The nitrogen was inserted into the carbon-13 by treatment with ammonia at high temperatures. N2O and N2 could thus be distinguished from CO2 and CO respectively in a thermogravimetric analysis-mass spectrometry instrument. The results of temperature-programmed gasification in oxygen-argon mixtures showed that the nitrogen in the carbon matrix was gasified to nitric and nitrous oxides with clearly bimodal gas evolution profiles, whereas the corresponding carbon monoxide and carbon dioxide profiles were symmetrical. The results are interpreted in terms of the gasification of different types of nitrogen functionality.
Six crude oils from the North Sea and the corresponding silica-adsorbed fractions are analysed by 13C nuclear magnetic resonance spectroscopy and subsequent principal component analysis. Solvent shifts, integrals and peak heights are used as input in the principal component analysis. The silica-adsorbed fractions are enriched in condensed aromatics relative to the crudes. The individual crudes vary from being relatively naphthenic/aromatic to relatively paraffinic. The principal component loadings for the peak heights strongly indicate the presence of a long straight chain aliphatic compound containing a heteroatom substituent. The compound is particularly abundant in the paraffinic oils. It is believed that it may be active in the formation of stable water-in-crude oil emulsions.
The difficulties associated with obtaining quantitative results from 13C nuclear magnetic resonance spectroscopy are discussed. By careful choice of the experimental conditions quantitative results have been obtained for a mixture of model compounds, containing most of the types of carbon linkages present in coal-derived materials, and for an aromatic fraction of a coal extract.
Solid state 13C n.m.r. analysis of the insoluble organic matter associated with the clay mineral, silica, and heavy metal minerals of heavy oils/bitumen is reported. The conditions under which these measurements can be made are related to the concentration of organic matter found, the nature and amount of paramagnetic constituents, and contact times. The data are related to changes in hydrophilic/hydrophobic surface properties of the solids. The relationship with bitumen losses in recovery processes is also discussed.
Selected, multiplet C n.m.r. spectra are obtained for three test samples deriving from petroleum and coal sources, by combining gated spin echo (GASPE) and conventional spin echo 13C n.m.r. procedures. Each selected multiplet spectrum contains resonances due to only one of the following groups: aromatic C or CH or aliphatic C, CH, CH2orCH3. In general artifacts contribute only minor intensity to individual spectra, with the separation between aliphatic CH and CH3 spectra being the most difficult to achieve. Each spectrum can be integrated to yield the relative abundances of CHn groups (n = 0 to 3). Selected multiplet 13C n.m.r. spectra provide a more detailed view of the component hydrocarbon groups in fossil-fuel derived materials than can be deduced from conventional 13C n.m.r. spectra.
Solid-state 13C n.m.r. (CP/MAS-13C n.m.r.) spectroscopy provides a direct method for estimating potential oil yields of oil shale formations. Relative aliphatic resonance areas correlate linearly with oil yield and provide a method for oil yield estimation that obviates the need to determine weight per cent organic carbon for each specimen. This direct measurement is performed using an internal area standard, the carbonyl resonance of N-(2-13C-propanonyl)-N,N,N-trimethylammonium chloride, to monitor spectrometer sensitivity. Oil shale samples obtained as a function of depth at a site in the Mahogany Zone of the Green River Formation show a near-constant aliphatic carbon fraction, fal ≡ (1−fa), and a twofold, nonlinear variation in oil yield over the vertical dimension of the sampling. Aliphatic carbon resonance band shape changes among these samples are interpreted qualitatively as reflecting a two component mixture composed of the condensed alicyclic structures which link together to form the kerogen matrix and an n.m.r.-distinct but not necessarily chemically distinct contribution from normal-long chain hydrocarbon residues.
A sample of kerogen from Aleksinac oil shale was examined by high-resolution solid-state 13C n.m.r. spectroscopy. The presence and relative proportions of kerogen structural units were estimated using a combination of NQS and T1ϱC methods with a peak-synthesis technique applied to the 13C CP—MAS spectrum. Relaxation parameters from these experiments were used to estimate differences in relative ‘mobility’ of various structural units. The kerogen was found to be highly aliphatic and to contain ∼ 79% long-chain aliphatic plus alicyclic structures, as well as ∼ 9% aromatic structures. These findings are in good agreement with the characterization of the same kerogen from its oxidation products.
Biomass pyrolysis for the production of fuels and chemicals is certainly one of the most promising strategies to replace petro-chemical polymers. Generally the biomass is first pyrolysed using temperature up to 700 °C to obtained vapors that are further cracked using catalysts. The catalyst can be poisoned by tars that are formed during the pyrolysis step and that are entrained with the vapor. In order to understand and model the behaviour of the biomass during such a process, a complete structural study of the chars was performed with high-resolution solid-state 13C, EPR, and susceptibility measurements. The origin of biomass does not affect the nature of the solid residues that are formed during the thermal treatment. They all loose their ligno-cellulosic structure and are transformed to polycyclic material with a preponderance of aromatic structures with proton amounts that decrease drastically as the temperature of treatment increases. The presence of unpaired electrons is undoubtedly indicated with EPR spectroscopy. Most of metallic compounds found in the solid residues are easily removed by a mild acidic treatment. It indicates that they are not intercalated inside the polycyclic plans. The occurrence of ferri/ferromagnetic parts has been clearly shown. Their origin is probably exogenous. The study has revealed some non-classical and unexpected features of the NMR spectra that are presented and discussed in relation to the structural properties of the pyrolysed biomass.
13C-1H heteronuclear dipolar dephasing n.m.r. techniques allow discrimination between different chemical species contributing to the 13C n.m.r. spectra of complex hydrocarbons. Model compound studies show significantly different effective transverse relaxation constants for carboxyl and quaternary carbon atoms (≈200 μs), secondary and tertiary (≈20 μs), and primary carbon atoms (≈80 μs). Use of these effective relaxation data, together with appropriately timed windows in the continuous wave decoupling applied in standard cross-polarization-magic-angle spinning experiments on anthracite coal allow discrimination between aromatic tertiary and aromatic quaternary ring carbon atoms in this coal. Within the accuracy of experimental error, and of the structural modelling experiments herein reported, the use of the dipolar dephasing technique together with results of X-ray diffraction on coals allows a reasonable estimate to be made of the average number of condensed polynuclear rings in an ‘average molecule’ in the anthracite studied. Based on a model of pericondensed aromatic rings, this number lies between 33 and 45.
The chemical structure of Estonian kukersite kerogen is evaluated using a simulation of 13C MAS NMR spectrum. A reasonable fit to the experimental NMR spectrum is obtained by assuming a model of the geomacromolecule with empirical formula C421H638O44S4NCl and a set of structural elements comprising mainly alkylated phenolic structures particularly alkyl-1,3-benzenediols and condensed alicyclic rings. From the presented model new views are coming up on the carbon skeleton of kerogen and constraints on the phenol formation pathways in the retorting process, i.e. up to 80% of methylene groups in kerogen are located in aliphatic chains and the complicated mixture of phenols in the retort oil seems to result mainly from the thermal conversion of alkyl-1,3-benzenediol units originally present in kerogen.
A new theoretical model has been developed which explains the association between the molecular structure and the knock resistance of individual gasoline compounds convincingly. The constitutions of more than 300 individual gasoline components were correlated with their knock rating (Blending Research Octane Number, BRON) simultaneously. 13C NMR spectra of all compounds were binned in 28 chemical shift regions of different size. The number of individual carbon signals of the nearly 2500 carbons was counted in each shift region and was combined with the information about the presence or absence of the structure groups Oxygen, Rings, Aromatics, aliphatic Chains and oLefins (ORACL). These numbers were used for the encoding of the chemical structure. The relations between the structure information and the knock ratings were determined using an artificial neural network. For a validation data set of 50 individual chemical compounds from various substance classes consisting only of C, H and O a good agreement was found with their experimentally determined BRON (R=0.933).
