Coal continued

Substitute or synthetic natural gas (SNG) has been known for several centuries. When SNG was first discovered, natural gas was largely unknown as a fuel and was more a religious phenomenon (see Gas, NATURAL) (1). Coal (qv) was the first significant source of substitute natural gas and in the early stages of SNG production the product was more commonly known under variations of the name coal gas (2,3). Whereas coal continues to be a principal source of substitute natural gas (4) a more recendy recognized source is petroleum (qv) (5). 

Wliile some problems still exist, there is no question that coal mining operations are more efficient and safer for workers and leave less of an environmental footprint than operations several generations ago. As society s demand for energy from coal continues to increase and as coal s price declines (between 1978 and 1996 U.S. mine mouth prices fell from 47,118 to 18..S11 per ton in constant 1996 dollars), there is certain to be even gi eater efforts to limit the environmental impact of mining operations. 

Over the next ten years (1919-1929), U.S. annual energy demand grew from nearly 18.7 to 25.4 quadrillions Btus. The percentage of energy represented by petroleum increased from a little over 12 percent to 25 percent. Natural gas also nearly doubled its share, from 4.3 perent to 8 percent. Coal continued to lose ground as a source of energy, from 78 percent to 63 percent of total energy consumption. 

From the onset of the Depression (1929) to the beginning of World War II (1941), petroleum s share of total U.S. energy consumption continued to expand, from 24 percent to more than 34 percent (while natural gas increased its share from 8 to 11 percent). Coal continued to lose share in the nation s energy output, from 62 percent to 54 percent. Over the same period, output of motor fuel, while not matching the growth of the previous decade, nevertheless continued its upward trend, from 256.7 million barrels to 291.5 million barrels. 

About 8(1 percent of the electric energy used in the United States is derived from stored energy in coal. The stored energy has its origin in photosynthesis. Coal is the end product of the accumulation of plant matter in an oxygen-deficient environment where burning is thwarted. Formation takes millions of years. Proven reseiwes of coal in the United States are upwards of 500 billion tons, a reserve so great that even if coal continues to be burned at a rate of over one billion tons per year, the reserves will last for hundreds of years. 

Jhe distribution of hydrogen types in coals continues to be a subject of considerable interest in coal structure studies. Published data indicate that the fraction of aromatic hydrogens usually increases with increasing rank, but the absolute values depend on the specific analytical method used (7). Hydrogen type analysis of a single coal based on the application of NMR spectroscopy to the soluble fraction from depolymerization with phenol-BFa has been reported by us (3). The conversion of coal to soluble fragments in substantial yields under very mild conditions permits a reliable determination of the hydrogen types by NMR analysis, and these results can be extrapolated to the parent coal with considerable confidence. 

Concerns about the environmental effects of emissions resulting from the combustion of fossil fuels, particularly coal, continue to increase as the utilization of these fuels grows. The large amounts of sulfur dioxide and nitrogen oxides emitted into the atmosphere and the attempts to tie these fossil-fuel-derived pollutants directly to the undeniably difficult problem of acid rain have caused heated debates, numerous research studies, government actions, and serious efforts to reduce pollution. The issues are extremely complex, and our understanding of the origin, properties, behavior, and effects of these pollutants is incomplete. Often, theories are contradictory. 

As Figure 4 indicates, the picture is similar in the rest of the world. It is clear from this picture that, on a macro basis, oil, gas and coal continue to dominate. Nuclear energy plays a role, but, besides hydroelectric power, renewable energy sources — at least on the surface — appear to have a long way to go to even make a dent in the current global energy market. 

As the removal of sulfur from coal prior to combustion acquires more importance in order to meet evermore stringent antipollution regulations, research on the development of methods for the cleaning of coal continues to expand. Reviews are available which describe the various methods for... 

All this, of course, requires that economically competitive technologies will be developed. As the costs of oil, gas, and coal continue to increase, the potential economic competitiveness of hydrogen production is becoming more real daily. Accordingly, it is essential that we move forward as rapidly as we can with research and development programs involving hydrogen production and use. 

The minerals found in United States coals continue to be studied with the availability of improved instrumental procedures such as x-ray diffraction, infrared absorption, and scanning electron microscopy beyond the traditional optical and chemical mineralogical techniques as applied to thin sections, polished pellets, and isolated particles. The minerals may be grouped into the silicates (kaolinite, illite montmorillonite, and chlorite), the oxides (quartz, chalcedony, hematite) the sulfides (pyrite, marcasite, and sphalerite) the sulfates (jarosite, gypsum, barite, and numerous iron sulfate minerals) the carbonates (ankerite, calcite, dolomite, and siderite) and numerous accessory minerals (apatite, phosphorite, zircon, rutile, chlorides, nitrates, and trace minerals). 

As the annual production of coal continues to increase, it is expected that the amount of coal refuse generated will also increase... 

Coal is the world s most abundant and widely distributed fossil fuel and possibly the least understood in terms of its importance to the world s economy. Currently, about 5 billion tons are mined in more than 40 countries. In spite of considerable pnblicity and push toward clean fuels, coal continues to be second only to oil in meeting the world s energy needs. Estimate indicate that in excess of 5 billion tons will be required annually by the year 2050 just to generate electricity. 

Although the majority of mined coal continues to be consumed within the country of production, the value of traded coal is increasing. The United States and Australia account for about 50% of world coal exports. This figure increases to 70% if exports from South Africa and Indonesia are included. Japan is the largest recipient of exported coal—approximately 25% of the world coal trade—and as such, agreements with coal suppliers and Japan can have a great influence on the world coal price. Japan, Taiwan, and South Korea together import about 45% of all coal exports and countries of the European Union accounts for another 30% of the total coal exports. 

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