Coal continued utilization

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. 

Many of the Southwest states have a large number of gas fired boilers. These units were very low in original investment cost and their continued utilization concerns utilities in those areas. Hydrotreated coal derived distillates offer a means of keeping these units available for years of additional service. 

All this swirling around costs taxpayer money and does little to reduce the acid rain problem. The trees in the northeast portion of the United States and in Eastern Canada continue to die and more lakes are sterilized. The primary result of the activity of both governments is the support of the bureaucracies funding research and their staffs. The problem continues. Since 1978 the United States Department of Energy has invested 15 billion in fossil energy research. Of this 58% was spent on coal conversion utilization, 24% on electricity Production, 14% oil gas Production and 4% on environmental characterization control. 

Another impetus to develop such processes is the desire of the U.S. Department of the Interior to ensure the continued utilization of coal. As our most abundant fossil fuel, it represents about 85% of the fuel reserves of this country. With the advent of nuclear technology and the pollution problems associated with burning sulfur-bearing coal in conventional power plants, much of this market will be lost to the atom. The continued use of this vast energy source will depend upon the ability to convert it into more versatile and desirable fuels. 

US coal prices have increased somewhat due to rising transportation costs (Figure 2.6). However, the overall trend in coal prices as measured at the mine (mine mouth) is downward as coal producers continue to find ways to increase the productivity of the average mine. The average delivered price for utilities increased just 5.7% during 2004 (EIA 2004), but 13.2% for industrial users. The widespread use of futures contracts in the coal industry has helped to keep prices stable. The overall stability of coal prices likely also will lead to a renewed interest in coal by utility officials and others, who until recently, believed natural gas was the fuel of the future. Anecdotal evidence purports an increase in coal use at the residential level. Homeowners with access to delivered coal found it is possible to heat less expensively with coal than natural gas or oil in the 2005-2006 heating season (Kamery 2006). 

Direct-Firing System. The pulverizing equipment developed for the direct-firing system permits continuous utilization of raw coal directly from the bunkers. This is accomplished by feeding coal of a maximum top size directly into the pulverizer, where it is dried as well as pulverized, and then dehvering it to the burners in a single continuous operation. Components of the direct-firing system are illustrated in Fig.6.20. 

Electric Power Generation. Coal is the primary fuel for thermal electric power generation. Since 1940 the quantity of bituminous coal consumed by electric utilities has grown substantially in each successive decade, and this growth is expected to continue for many years. Coal consumed by electric utilities increased from about 536 x 10 t in 1981 to 689 x 10 t in 1989 (2). The reasons for increased coal demand include availability, relative stability of decreasing coal prices, and lack of problems with spent fuel disposal as experienced in nuclear power plants (see Nuclearreactors). 

Historically, under both federal and state regulations, the demand for gas to heat homes and to meet needs of business and industiy took priority over utility use to generate electricity. These restrictions have been eased by amendments to the Fuel Use Act in 1987, and, as a result, new gas-fired generation units are being constructed. However, coal-fired units continue to provide over 50 percent of the total utility generation of electricity. 

Three major compliance options for SOj emissions available to utilities using coal-fired boilers are to switch fuels, purchase/sell SO, allowances, or install flue gas desulfurization (FGD) technologies. Costs, availability, and impact on boiler operation must be considered when evaluating switching to low-sulfnr coal or natural gas. As more utilities enter the free market to purchase SO, allowances, prices will rise. Therefore, to minimize costs and, at the same time, meet environmental standards, power producers should continuously monitor the tradeoffs among these three options. 

About 25 years ago, a major conference on coal science was held at The Pennsylvania State University. The papers presented at that conference were subsequently published as Coal Science, an out-of-print volume in the Advances in Chemistry Series of the American Chemical Society. Some of the chapters in that volume are still cited in current literature, a testament to the quality and continuing relevance of that work to the field of coal science. The conference organizer, Peter Given, had come to Penn State a few years earlier after a 10-year career with the British Coal Utilization Research Association. Even then. Given had established a reputation as a significant contributor to coal science. In the following years, he came to be recognized as one of the dominant coal scientists of the post-World War II era. 

In Table II, a former oil burning boiler that was converted to burning low sulfur coal could not meet particulate compliance levels. To continue to operate, the utility was forced to derate from 650 Mw to 440 Mw. The LPA flue gas conditioner, however, allowed operation at 582 Mw, well within particulate compliance levels. (LPA and LAC are product series designations of Apollo Chemical Corp.)... 

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