COAL: Ancient Gift Serving Modern Man
American Coal Foundation
New Technologies for Coal Combustion
The Clean Air Act, which has been in effect since 1970, and was last amended in 1990, is the most stringent air pollution control law in the world. Because of it, and through the combined efforts of business and industry, citizens and government, we enjoy some of the cleanest air to be found anywhere on the globe.
American industry has spent some $350 billion since 1970 to clean up the air, and each year the tab for pollution control totals another $33 billion.
Pollution control equipment accounts for up to 40 percent of the cost of a new power plant and 35 percent of operational costs, according to the Electric Power Research Institute. Those costs plus operating costs currently account for about $10 billion of the nation's electric bills each year, and will rise even higher under new Clean Air Act requirements.
Although environmental concerns about coal use center on the emission of sulfur and nitrogen compounds and carbon dioxide, coal is not the only for the leading source of them in our environment. However, coal combustion is a significant contributor, so as part of a national commitment to further reduce air pollution, more than a dozen advanced technologies for burning coal cleanly and more efficiently are being investigated. The development and demonstration of these technologies has required a substantial investment of more than $6 billion by government and private industry. Two of the leading technologies are:
Fluidized-bed Combustion (FBC)
Crushed coal mixed with limestone is supported on a strong rising current of air. The "fluidized" mixture acts as a boiling liquid, mixing turbulently, thus assuring efficient combustion. The limestone reacts with and removes over 90 percent of the sulfur. As a consequence, "scrubbers" (flue gas desulfurization) are not required for SO2 control. Because the operating temperature is lower than in conventional boilers, the formation of nitrogen oxides is minimized.
The FBC technology lends itself to the design of smaller boilers that can be prefabricated as modular units, and at less capital cost than conventional boilers of the same generating capacity. Because of this savings, and the favorable economics of adding additional generating capacity to a power plant only as it is needed, electric utilities and consumers both are expected to find this technology attractive.
As an alternative to direct combustion of coal, in which the heat produced is used to develop steam to drive generator turbines, a great deal of progress has been achieved on technologies that depend on first gasifying the coal. The gas itself can be burned to power gas turbines, and then the remaining heat can be harnessed to produce steam to turn turbines.
This type of arrangement, called combined cycle gasification, is extremely efficient and clean. At one demonstration plant in California, emissions of combustion products were comparable to those from a natural gas-fired facility, allowing the plant to meet California's clean air requirements, the strictest in the country. Another advantage of the coal gasification process is that it can be carried on in close proximity to the mine site. Rather than shipping the bulky coal long distances to a power plant, the power of coal can be shipped by wire from the gasification plant.
These and other advanced clean coal technologies variously hold the promise of generating more power with less fuel, and reduced operating and maintenance costs; greater pollution control; some produce marketable by-products; and many utilize smaller plants that can be modularly built. But they all speak to the same goal: making more effective and efficient use of an abundant energy resource.