Impurities in coal

L.26 Sulfur is an undesirable impurity in coal and petroleum fuels. The mass percentage of sulfur in a fuel can be determined by burning the fuel in oxygen and dissolving the SO, produced in water to form aqueous sulfuric acid. In one experiment, 8.54 g of a fuel was burned, and the resulting sulfuric acid was titrated with 17.54 mL of 0.100 m NaOH(aq). (a) Determine the amount (in moles) of H2S04 that was produced, (b) What is the mass percentage of sulfur in the fuel ... 

The combustion products from sulfur Impurities In coal are particularly damaging to the environment. In humans, prolonged exposure to sulfur dioxide diminishes lung capacity and aggravates respiratory problems such as asthma, bronchitis, and emphysema. Concentrations as low as 0.15 ppm can incapacitate persons with these diseases, and at about 5 ppm everyone experiences breathing difficulties. In 1952 a particularly serious episode of SO2 pollution In London caused approximately 4000 deaths over several days. 

C05-0119. Explain in your own words how sulfur impurities in coal can lead to acid rain. Use balanced equations... 

Raask, E., Mineral Impurities In Coal Combustion, Hemisphere Publishing Corp., New York 1985. 

Differences in the range of impurity in coal account for the different grades of coal. 

The impurities in coal beds, present either as distinct partings or disseminated throughout, are composed of clay materials that have a high density and a high natural radioactivity relative to coal. Consequently, the... 

Free impurities impurities in coal that exist as individual discrete particles that are not a structural part of the coal and that can be separated from it by coal preparation methods (ASTM D-2234 ASTM D-4915). 

Raask, E. Mineral Impurities in Coal Combustion, Hemisphere Publishing, N.Y. (1985). 

The first of the previous reactions is responsible for a good portion of the acid rain problem troubling the industrialized world. Sulfur, present in small quantities as an impurity in coal and oil, is converted to sulfur dioxide when the coal or oil is burned then the sulfur dioxide reacts with the moisture in the air to produce sulfurous acid. Sulfurous acid can react with the oxygen in air to produce sulfuric acid. These acids are washed from the air by rain (or snow), and the solution can cause some corrosion of concrete and metal in buildings. Acids in the air and in the rain or snow also injure trees and other plants, as well as animals, including humans. In high concentrations, acids and acid anhydrides in the air can make breathing difficult, especially for people who are already in poor health. 

Mineral impurities in coal are known to be primary contributors to the slagging and fouling of utility boilers, fly ash and bottom ash production as well as atmospheric pollution. They also produce undesirable effects in some parts of hydrogenation processes such as liquifaction and gasification (1,2,3). Despite a long history of investigation prompted by these observations, many questions remain unanswered. 

Mineral Impurities in Coal Combustion - The Behaviour, Problems and Remedial Measures" Hemisphere New York, 1985. 

Fly ash starts out as impurities in coal, mostly clay, shales, limestone, and dolomite, which ends up as ash, and fuse at high temperature becoming glass. Two U.S. classifications of fly ash are produced. Class C and Class F, according to the type of coal used. Class C fly ash, typically obtained from subbituminous and lignite coals, must have more than 50% total of silica, alumina, and iron oxide. Class F fly ash, typically obtained from bituminous and anthracite coals, has more than 70% of these oxides. 

We discuss catalysts in Chapter 16 and H2SO4 production in Chapter 21. These two sulfur oxides also form when sulfur impurities in coal burn and then oxidize further. In contact with rain, they form H2SO3 and H2SO4 and contribute to a major pollution problem that we discuss in Chapter 19. 

Raask, E., 1985, Mineral impurities in coal combustion. Hemisphere Pub. Corp., Washington. 

Williams FA and Crawley CM, Impurities in Coal and Petroleum, The Mechanism of Corrosion by Fuel IMPURITIES. Butterworth, London, UK, 1963, p. 34. 

The principal consideration of coal beneficiation is to upgrade the quality of coal for direct use in steam and power generation, or for special uses such as chemical feedstock, feed to liquefaction, and gasification. The properties and quantities of impurities in coal are known to be the major factors that place limitations on coal utilization. All coals are not the same (Chapters 1 and 2). Thus, the type of coal beneficiation technology and the extent of beneficiation depend mostly on the type of coal, the means of mining, and the clean coal utilization. 

Actually, the abrasiveness of coal may be determined more by the nature of its associated impurities than by the nature of the coal substance. For example, pyrite is 20 times harder than coal, and the individual grains of sandstone, another common impurity in coal, also are hard and abrasive. 

Combustion of coal produces various forms of CCPs due to the mineral impurities in coal body. Fly ash is one of the most important CCPs requiring efficient control during coal combustion (Akar et al., 2009). Especially, the fine particulates (PMjq) in the fly ash may pass through the dust collection devices and be released to the atmosphere. 

Marina OA, Pederson LR, Coyle CA, Thomsen EC, Coffey GW (2005) NiA SZ anode interactions with impurities in coal gas. ECS Trans 25(2) 2125-2130... 

Nature of Impurities in Coal. Impurities can be divided into two general classifications— inherent and removable. The inherent impurities are inseparably combined with the coal. The removable impurities are segregated and can be eliminated, by available cleaning methods, to... 

Gravity Concentration. Removal of segregated impurities in coal by gravity concentration is based on the principle that heavier particles separate from the lighter ones when set-thng in a fluid. This principle is applicable because most common solid impurities are heavier than coal (Table 6.10). 

In a review paper, Cayan et al. (2008) summarized study results on the identification of impurities in coal syngas on the performance of SOFCs. 

Note 2. Electrical heating during the Kjeldahl digestion and ammonia recovery is preferable to gas heating. The chance of contamination of the sample by nitrogenous impurities in coal gas is thereby avoided. 

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