Solid fossil fuels

Solid fossil fuel and wood residue-fired... 

The problems involved in the study of humic substances are, as expected, also encountered in the case of fossil fuels. Most C-13 CP/MAS spectra of solid fossil fuels (coals, oil shales) do not exhibit a high level of spectral resolution50,51). They consist essentially of two broad bands — one in the aromatic/olefinic region from about 170 ppm to 95 ppm and one in the aliphatic region from about 90 to —5 ppm relative to TMS. On the other hand, lignite, an imperfectly formed coal, shows a considerable amount of fine structure. 

Prior to the discovery of plentiful supplies of natural gas, and depending on the definition of the resources (1), there were plans to accommodate any shortfalls in gas supply from solid fossil fuels and from gaseous resources by the conversion of hydrocarbon (petroleum) liquids to lower molecular weight gaseous products. 

Of all the fossil fuels, the use of natural gas results in the formation of the least amount of C02 per unit of heat eneigy produced. On a constant energy basis, natural gas combustion produces approximately 30% less C02 than liquid petroleum fuels and approximatdy 45% less C02 than coal and other solid fossil fuels. 

Because of substantial reserves of coal, situated in distant locations from consumers, the limited sources of oil and natural gas, expected growing price of oil and gas a considerable development and progress in the coal pipelining can be expected especially in the USA, in the former Soviet Union and also in other countries in a near future. One of prospective ways of energy transportation, i.e. gas, liquid and also solid fossil fuels transport, seems to be the transport of solidified oil in LNG and pipelining of coal in methanol. 

Figure 1 shows the pressurised fluidised bed test installation (DWSA) at IVD, University of Stuttgart. The DWSA is used for several years in the framework of research in the field of conversion of solid fossil fuels under well-defined reproductive process conditions and on a small scale (50 kWth maximal), see e.g. Nagel et al, [2]. 

Two major types of gasifiers for solid fossil fuels are available commercially at the present time. The cocurrent or downdraft versions are used in small internal combustion engine applications for sawmills, remote communities, and to satisfy power needs for developing nations. A more recent advance is the fluidized-bed gasifier, which is appropriate for larger-scale conversion of biomass to producer gas or other products. 

Bartuska, V. J., Maciel, G. E., Schaefer, J., and Stejskal, E. O. (1977). Prospects for carbon-13 nuclear magnetic resonance analysis of solid fossil fuel materials. Fuel 56, 354-358. 

Institute of Solid Fossil Fuels Preparation (lOTT)... 

A solid fossil fuel mostly consisting of carbon... 

Two other more dilute and much less easily worked sources of solid fossil fuels are oil shale and tar sands. Each of two relatively small areas of the North American continent have amounts of oil bound in shales and sands which, when retorted out, could produce more oil than the total of all of that of the Middle East (5), Billions of dollars have been spent and are being spent to implement the work of a thousand chemical, mechanical, mining, and civil engineers, geologists, and other scientists working for 15 to 20 companies. Climate problems add to the material problems of having to mine, process by extraction and/or retorting, and then replace ten times as much solids as products. The oil shales are in an almost barren semidesert and the tar sands are in a very wet (in summer) area within 10° of the Arctic Zone. 

D. E. Axelson, Solid State Nuclear Magnetic Resonance of Solid Fossil Fuels, Multiscience Publications Ltd. CANMET and Canadian Government Publishing Centre, Montreal,... 

NMR Characterization of Solid Fossil Fuels Using Cross-Polarization and Magic-Angle Spinning... 

Most of the studies of solid fossil fuels have used the mushroom3c and bullet types,3a made of Kel-F. 1h decoupling fields of about lO-to-14 gauss are most common. In fossil fuel work cross polarization (contact) times of about 1 ms and repetition times of about Is are typically used, although variations of these parameters have been made (see below). Spin-temperature alternation, in which one alternates by 180° the phase of the H spin-locking field and also alternates the... 

One reason why one might inquire about the possibility that some of the carbon atoms in a solid fossil fuel are not accounted for in a CP/MAS experiment is that there are large concentrations of unpaired electrons in such samples. 

Such studies are really only of use for SCPs rather than IASs. The vast majority of IASs come from solid fossil-fuels (coals, oil shale) but there is no morphological means by which to separate them, coming as they do from the fused minerals present within the fuel. Similarly, there is no certain way of identifying sources chemically, as the chemical composition of the IAS particle is dependent upon the original mineral rather than the fuel-type and hence the particle compositions are also potentially very similar between fuel-types (i.e., mainly aluminosilicate). However, Alliksaar et al. (1998) suggest that oil shale IASs contain higher Ca and K and lower Al than their coal-derived counterparts. 

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