Mercury in fossil fuels

INTRODUCTION 1.1 The Global Mercury Cycle FUNDAMENTAL GEOCHEMISTRY. 2.1 Solid Earth Abundance and Distribution. 2.2 Isotopic Distributions. 2.3 Minable Deposits. 2.4 Occurrence of Mercury in Fossil Fuels SOURCES OF MERCURY TO THE ENVIRONMENT. 3.1 Volcanic Mercury Emissions... 

In this section, we consider aspects of the fundamental geochemistry and biogeochemistry of mercury used later in the chapter. These topics include (i) solid Earth abundance and distribution, (ii) isotopic composition and recent advances in mercury cosmochemistry, (iii) the formation and distribution of minable mercury deposits, and (iv) mercury in fossil fuels. 

Occurrence of Mercury in Fossil Fuels SOURCES OF MERCURY TO THE ENVIRONMENT. 3.1 Volcanic Mercury Emissions... 

Although the petrochemical and metals industries were the primai y focus of the toxic air pollutants legislation, approximately forty of these substances have been detected in fossil power plant flue gas. Mercury, which is found in trace amounts in fossil fuels such as coal and oil, is liberated during the combustion process and these emissions may be regulated in the future. EPA issued an Information Collection Request (ICR) that required all coal-fired plants to analyze their feed coal for mercury and chlorine. Since these data will be used in making a regulatory decision on mercury near the end ot the year 2000, it is critical that the power industry provide the most accurate data possible. 

Mercury is one of a number of toxic heavy metals that occur in trace amounts in fossil fuels, particularly coal, and are also present in waste materials. During the combustion of fuels or wastes in power plants and utility boilers, these metals can be released to the atmosphere unless remedial action is taken. Emissions from municipal waste incinerators can substantially add to the environmental audit of heavy metals, since domestic and industrial waste often contains many sources of heavy metals. Mercury vapor is particularly difficult to capture from combustion gas streams due to its volatility. Some processes under study for the removal of mercury from flue gas streams are based upon the injection of finely ground activated carbon. The efficiency of mercury sorption depends upon the mercury speciation and the gas temperature. The capture of elemental mercury can be enhanced by impregnating the activated carbon with sulfur, with the formation of less volatile mercuric sulfide [37] this technique has been applied to the removal of mercury from natural gas streams. One of the principal difficulties in removing Hg from flue gas streams is that the extent of adsorption is very low at the temperatures typically encountered, and it is often impractical to consider cooling these large volumes of gas. 

Mercury Measurements in Fossil Fuels, Particularly Petrochemicals... 

ABSTRACT The dangers of mercury and its derivatives, especially organomercury compounds have been well dociunented for almost half a century. Concerns remain regarding mercury contamination in aqueous ecosystems. Significant quantities of mercury are present in fossil fuels, particularly petrochemicals. 

Despite its availability and current use, coal is not as widely used today as the other fossil fuels. Coal s major weakness is that it does not burn cleanly. It often contains trace amounts of other elements, including mercury, arsenic, and sulfur, and when it burns, it releases these toxic substances into the air. Over time, coal pollution builds up in the environment. Mercury released during coal combustion, for example, settles in water and builds up in the bodies of fish and shellfish. When these fish and shellfish are eaten by humans and other animals, harmful amounts of mercury can be ingested. In 2008, bluefm tuna served in expensive New York restaurants was found to contain unacceptably high levels of mercury. These fish eat smaller organisms in the ocean, and when these small organisms contain mercury, the toxic element becomes concentrated in the body of the tuna. 

Mercury is mined predominantly as HgS in cinnabar ore and is then converted commercially to a variety of chemical forms. Key industrial and commercial applications of mercury are found in the electrolytic production of chlorine and caustic soda the manufacture of electrical equipment, thermometers, and other instruments fluorescent lamps dental amalgam and artisanal gold production. Use in pharmaceuticals and in biocides has declined substantially in recent years, but occasional use in antiseptics and folk medicines is still encountered. Thimerosal, an organomercurial preservative that is metabolized in part to ethylmercury, has been removed from almost all the vaccines in which it was formerly present. Environmental exposure to mercury from the burning of fossil fuels, or the bioaccumulation of methylmercury in fish, remains a concern in some regions of the world. Low-level exposure to mercury released from dental amalgam fillings occurs, but systemic toxicity from this source has not been established. 

Interest in trace element emissions received impetus from published reports of widespread atmospheric dissemination of these substances (1), especially mercury (2, 3), as a consequence of fossil fuel use. More current information indicates that the original mercury discharge estimates were overstated, since they were based on nonrepresentative, ore-associated coal samples (4). Of the fossil fuels, coal is considered the major source of atmospheric pollution (5) and, compared with oil and... 

Solely on the basis of volatility profiles, fossil fuel burning is expected preferentially to transfer As, Hg, Cd, Sn, Sb, Pb, Zn, Tl, Ag, and Bi to the atmosphere (1). In a study designed to detect fallout from a major coal burner equipped with a precipitator, Klein and Russell (27) showed that Ag, Cd, Co, Cr, Fe, Hg, Ni, Ti, and Zn were deposited in the surrounding soil (115 sq mi), and with the exception of mercury, enrichment correlated with the respective metal concentrations in the coal. Mercury was more widely disseminated to the environment. Previous work has indicated that mercury exists primarily in the volatile phase of the flue gas and consequently as much as 90% bypasses the electrostatic precipitation control device (2). Bolton and co-workers have evidence that selenium and arsenic may present a similar problem (see Chapter 13). 

Cadmium is close to lead and mercury as a metal of current toxicological concern.12346 Extraction of lead and zinc ores, which contain cadmium, pollutes the environment with cadmium. The use of cadmium before 1900 was infrequent however, its valuable metallurgical properties, such as resistance to corrosion, increased its use markedly, for example in the manufacture of alloys and as a coating on steel. It is also now widely used in nickel cadmium ( nicad ) batteries. Coal and other fossil fuels contain cadmium which is released into the environment on combustion. 

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