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Clean Coal Engineering Technology
By Bruce G. Miller
Butterworth-Heinemann
Copyright © 2011 Elsevier Inc.
All right reserved.
ISBN: 978-0-08-096116-3
Chapter One
Coal as Fuel Past, Present, and Future
1.1 Organization of this Book
Coal is the largest source of solid fuel in the world. It exists in almost every country, and approximately 70 countries mine it. Coal is the primary fuel source for power generation, and as developing countries become more industrialized, more coal is being used, and its use is projected to increase over at least the next couple of decades. Coal is also being considered as a way to produce liquid fuels. More countries are considering installing facilities to produce liquid fuels via indirect liquefaction (i.e., gasifying coal and producing liquid fuels from the gases), which South Africa has done since the 1950s. Countries are also seriously exploring direct coal liquefaction technologies for fuel production. China has taken the lead in constructing direct coal-to-liquid plants, and it is likely that more countries will do the same.
Along with increased coal usage, however, come concerns about the environment. System efficiencies must be improved; coal cannot be used as a "dirty" fuel. Emissions, including carbon dioxide, must be controlled. Clean coal technology is not an oxymoron, and using these technologies for efficient coal consumption in an environmentally acceptable manner must be ramped up immediately. This book provides significant information on all of the issues associated with clean coal technologies.
Chapters 1 through 3 discuss coal use in the past and present and the potential future trends of coal usage, coal distribution throughout the world, and coal chemistry. The effect of coal as a fuel on human health and the environment is presented in Chapter 4. Chapter 5 introduces the four major technologies for utilizing coal: carbonization/pyrolysis, combustion, gasification, and liquefaction. Chapter 6 looks at the anatomy of a coal-fired power plant, which developing countries are installing at a rapid pace.
A discussion of clean coal technologies, such as fluidized-bed combustion, advanced pulverized coal power plants, and integrated gasification combined cycle systems, is provided in Chapter 7. Coal-fired emission regulations are presented in Chapter 8. Emissions-control strategies are presented in Chapter 9, and the process of carbon capture and storage is examined in Chapter 10. A discussion of clean coal technology programs for near-zero emissions when generating electricity is provided in Chapter 11. Finally, Chapter 12 discusses coal's role in providing energy security for the world, especially in the United States.
1.2 The History of Coal Use
The next sections present a brief history of the use of coal, including a comparison to other energy sources. Although the concentration here is on coal use in the United States, a global perspective is also presented, especially with regard to comparing overall energy consumption. In addition, the sections look at the different types of technologies that were used in the past and were developed as part of the Industrial Revolution. A more in-depth discussion of major coal technologies, however, is provided in subsequent chapters.
1.3 Coal Use before the Industrial Revolution
Coal has been used as an energy source since ancient times, but it was considered a minor resource until the Industrial Revolution. The first mention of coal in European literature dates from the fourth century B.C., but scholars are certain that coal was first used in China as early as 1000 B.C.. By A.D. 1000, coal was the primary fuel source in China, and its use was reported by the Venetian traveler Marco Polo in the thirteenth century.
The first documented use of coal in Western civilization was by the Greek philosophers Pliny, Aristotle, and Theophrastus—Aristotle's pupil. The first definitive record of coal being used for fuel is found in Aristotle's Meteorology, where he writes of combustible bodies. Theophrastus, in his fourth-century Treatise on Stones, describes a fossil substance used as a fuel. Theophrastus and Pliney both mention blacksmiths using coal. This was most likely brown coal from Thrace in northern Greece and from Ligurai in northwestern Italy. Because it was high in impurities and did not create a very hot fire, it was not commonly used in iron smelting furnaces. Pliney, however, refers to its use in copper casting, which can be done at considerably lower temperatures.
Although the Greeks and Romans knew about coal by 400 B.C., they mostly used wood for fuel, since it was so plentiful. Coal was used as a domestic heating fuel in some parts of the Roman Empire, particularly in Britain, but it never made more than a marginal contribution as a fuel resource. As the Romans invaded northward, they saw coal being mined and used in the vicinity of St. Etienne in Gaul (France) and in Britain, where coal cinders that have been discovered in Roman ruins show that coal was used during the Roman occupation from approximately A.D. 50 to 450.
During the Middle Ages, coal had to be rediscovered in Europe, and for some time coal was of little local importance. Although coal was used on a small scale in Western Europe for thousands of years, the remains of a body that had been cremated with coal during the Bronze Age were discovered in South Wales. Evidence of Roman coal-fueled fires has also been discovered on the northern English frontier along Hadrian's Wall. It does not appear that European coal was used for hundreds of years after the fall of the Roman Empire. Records from the Middle Ages show that coal was given to the monks in the Abbey of Peterborough in A.D. 852 as an offering or as a settlement of a claim. Coal was mined in Germany as early as the 900s and was mentioned in the charter (dated 1025) of the French priory of St. Sauveuren-Rue.
Even though peasants probably continued to use surface coal for domestic heating fuel, no evidence of coal use for industry has been found until around 1200. Coal was discovered to be a very good fuel for iron forges and metalworking because it burned almost as slowly as charcoal, which is produced from wood and was the primary fuel of choice for village smiths. Shipping records from this period show that coal was marketed in Western Europe; smiths preferred coal over charcoal if they could get it at a reasonable price. Liège in Belgium, Lyonnais in France, and Newcastle in England all became important mining centers.
At first, only coal that was near the areas where it was mined was used because wood and charcoal were much lighter and thus less expensive than coal to transport by land. However, as water transportation on rivers and the sea increased, and as wood became scarcer, particularly in the cities, coal became the fuel of choice. By the mid-1200s, sea-coal—as it was called to distinguish it from charcoal—was being transported to London by sea from Newcastle. By the 1370s, 84 coal-boats were traveling down the east coast of England to ten different ports along the European coast between France and Denmark, returning with iron, salt, cloth, and tiles.
Although coal became the fuel of choice for blacksmiths during medieval times, it had limited use as a heat source because of its fumes. However, as wood became increasingly scarce and coal became less expensive in the cities, coal use increased significantly. With the increased use of coal (mainly in fireplaces designed to burn wood) came increased pollution problems, mainly black smoke and fumes. In 1257, Queen Eleanor was forced to flee Nottingham Castle as a result of smoke and fumes rising from the city below. In 1283 and in 1288, the air quality in London suffered because coal was being used in lime kilns. In 1307, a Royal Proclamation forbade the use of coal in lime-burners in parts of South London. This proclamation did not work, however, and a later commission was ordered to punish offenders with fines and ransoms for a first offense and the demolition of their furnaces for a second offense.
Eventually, economics and a change in government policy won out over the populace's comfort, and London's air continued to be polluted by coal fumes for another 600 years. The price of firewood increased, and it became more profitable to transport coal over longer distances. In addition, during late sixteenth- and seventeenth-century England faced the dilemma of conserving its remaining forests and using the only available substitute: coal. In 1615, the English government encouraged the substitution of coal for wood whenever possible. A fundamental change in English domestic building followed with more brick chimneys constructed to accommodate the fumes from coal.
1.3.1 The Early History of U.S. Coal Mining and Use
Coal was reportedly used by the American Indians of the Southwest before the arrival of the early explorers in America. The first mention of coal in the United States is a map prepared around 1673–1674 by the Frenchman Louis Joliet that indicates charbon de terra along the Illinois River. In 1701, coal was discovered near Richmond, Virginia, and a map drawn in 1736 shows the location of several "cole mines" on the upper Potomac River, near what is now the border of Maryland and West Virginia. By the mid-1700s, coal was also reported in Pennsylvania, Ohio, and Kentucky, with the first commercial U.S. coal production beginning near Richmond, Virginia.
Blacksmiths in colonial days used small amounts of coal to supplement the charcoal they used in their forges. Farmers dug coal from beds exposed at the surface and sold it. Although most of the coal for the larger cities along the eastern seaboard was imported from England and Nova Scotia, some of it came from Virginia.
1.4 Coal Use during the Industrial Revolution
Several developments during the eighteenth century caused an expanded use of coal in England and culminated with the Industrial Revolution from 1750 to 1850. These developments included the transport revolution, the iron industry revolution, and the demise of the forests.
In eighteenth-century England, coal was the only available fuel because the supply of wood had become exhausted in the populated areas. Demand for coal increased as a source of fuel for domestic needs and the small businesses that developed in the towns, such as bakeries, smithies, tanneries, sugar refineries, and breweries. Transporting the coal by sea was not sufficient to meet the demand for coal because sea transport was unreliable, and it could not accommodate the demand in inland areas. Canals, however, could meet this need. More than half of the Navigation Acts passed between 1758 and 1802 to establish a canal or river improvement company were for those whose primary business was to transport coal. Establishing a transport system was crucial to the success of the Industrial Revolution, which would ultimately be driven by the coal and iron industries. Bulky raw materials and the finished products needed to be transported quickly and cheaply across England.
Both the iron industry and the increased need for coal to produce coke for iron smelting were important contributing factors to the development of the Industrial Revolution. Abraham Darby successfully smelted iron with coke as early as 1709, and this technological innovation became very important in the 1750s as the price of charcoal rose and the price of coal declined. Once the switch from wood to coal was complete, an ironmaster's constraint on his output was not his fuel supply, but his power supply to provide an adequate blast in his furnace. In 1775, Boulton and Watt's invention, the steam engine, provided an unlimited source of power that up to that time had been water power and, to a lesser extent, wind power. The steam engine, which was fueled by coal, removed any restrictions on the ironmasters as to the size or location of iron works. The ironmasters could now move into areas that were rich in coal and iron resources and reap the economies of scale of a modern industry. With the invention of the steam engine came the locomotive, another means for mass transportation of raw materials and products, which also consumed coal as a fuel source.
The uses for coal did not stop with coking and solid-fuel combustion for transportation. It was discovered that the gases released from coal during the coking process could be burned as well. This in turn led to the establishment of the manufactured gas industry to take advantage of the illuminating power of coal gas. In 1810, an Act of Parliament was obtained to form a company to supply coal gas to London.
The Industrial Revolution began in England, but it soon spread to continental Europe, mainly France and Germany, and eventually to the United States. These countries were able to benefit from the discoveries that were driving the Industrial Revolution because they had ample supplies of coal as well. During the 1800s in the United States, coal became the principal fuel used by locomotives, and as the railroads branched into the coal fields, they became a vital link between the mines and the markets. Coal also found growing markets as fuel for homes and steamboats and in the production of illuminating oil and gas. In fact, shortly after London began using coal gas, Baltimore became the first city in the United States to light streets with coal gas in 1816. As in England, coke soon replaced charcoal as the fuel for iron blast furnaces in the latter half of the 1800s.
1.5 The Post–Industrial Revolution Use of Coal
The technologies that used the most coal—combustion, gasification, liquefaction, and carbonization, which is the production of coke—either got their start during the 100-year-plus period of the Industrial Revolution/post–Industrial Revolution era or, in the case of coke production, they made major strides in technology development and usage. These technologies are discussed in detail in Chapter 5, but an introduction to their history is provided here. The demand for coal increased as additional fuel chemistry and engineering technologies were developed. In 1855, R.W. Bunsen invented the atmospheric gas burner, which led to a wide range of heating applications.
Electric lighting, which had its start in the late 1800s, led to widespread coal combustion in the process of producing steam for power generation. The generation of electricity through the use of coal has undergone various stages of technology development since the late 1800s, and examples include areas such as advanced combustion technologies; new materials of construction; innovative system designs; and new developments in steam production, electricity generation, and pollution control. These are discussed in detail in later chapters.
As the use of coal gas became more widespread, the production of gas for heating purposes was also developing. The first gas producer that created low-Btu gas was built in 1832, and at the turn of the century was an important method for heating furnaces. Another development in the gas production field was the discovery of the carbon–steam reaction, where steam is reacted with carbon to produce carbon monoxide and hydrogen. This gasification technology had its major start in the mid- to late 1800s and increased until less expensive natural gas replaced manufactured gas.
Coal hydrogenation began in 1913 with the Bergius concept of direct hydrogenation of coal under hydrogen pressure at an elevated temperature. The production of liquid hydrocarbons through indirect liquefaction—known as the Fischer-Tropsch synthesis—was also conceived at this time.
1.6 An Overview of Energy in the United States
The United States has always been a resource-rich nation, but in Colonial times, nearly all of the energy was supplied by muscle power—both human and animal; water; wind; and wood. The history of energy use in the United States began with wood being the dominant energy source from the founding of the earliest colonies until late last century, as shown in Figure 1.1. Consumption is illustrated in quadrillion (i.e., 1015) Btu in Figure 1.1. Although wood use continued to expand along with the nation's economic growth, energy shortages led to the search for other energy sources. Hence, coal began to be used in blast furnaces for coke production and in the making of coal-gas for illumination in the early 1800s. Natural gas found limited application in lighting. It was still not until well after mid-century that the total work output from engines exceeded that of work animals.
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Excerpted from Clean Coal Engineering Technology by Bruce G. Miller Copyright © 2011 by Elsevier Inc.. Excerpted by permission of Butterworth-Heinemann. All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.
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