Coal combustion organic compounds present

Table I. List of Organic Compounds Present in Effluents From Coal Combustion...

The high temperatures in the MHD combustion system mean that no complex organic compounds should be present in the combustion products. Gas chromatograph/mass spectrometer analysis of radiant furnace slag and ESP/baghouse composite, down to the part per biUion level, confirms this behef (53). With respect to inorganic priority pollutants, except for mercury, concentrations in MHD-derived fly-ash are expected to be lower than from conventional coal-fired plants. More complete discussion of this topic can be found in References 53 and 63. 

Coincident with the development of sampling procedures were the constant iterative improvements in extraction, separation, identification and quantitation of organic compounds. Special emphasis was placed on selected compound classes such as the polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), chlorinated benzenes, and chlorinated dibenzo-p-dioxins (dioxins). The best available procedures were used to determine these components because they have known acute or chronic effects and previous studies suggested that they might be present in effluents from the combustion of coal alone and combination coal/RDF. 

A combined listing of all the compounds identified in the vapor and on particles emitted during the combustion of coal at the /toes power plant are listed in Table I. Similar compounds have been identified in the emissions from a second coal-fired power plant located at Iowa State University. Therefore, this list may be partially representative of coal combustion in semi-modern boilers. Certainly, many more organic compounds than the listed 78 are present in these effluents, but so far these have not been positively identified. Indeed, a 1980 review of organic compounds from coal combustion (1) taken from all the literature reports had only 106 compounds identified. 

World sulfur reserves. The earth s crust contains about 0.6% S, where it occurs as elemental S (brimstone) in deposits associated with gypsum and calcite combined S in metal sulfide ores and mineral sulfates as a contaminant in natural gas and crude oils as pyritic and organic compounds in coal and as organic compounds in tar sands (Tisdale and Nelson, 1966). The elemental form commonly occurs near active or extinct volcanoes, or in association with hot mineral spings. Estimates by Holser and Kaplan (1966) of the terrestrial reservoirs of S suggest that about 50% of crustal S is present in relatively mobile reservoirs such as sea water, evaporites, and sediments. The chief deposits of S in the form of brimstone and pyrites are in Western European countries, particularly in France, Spain, Poland, Japan, Russia, U.S.A., Canada, and Mexico. World production of S in the form of brimstone and pyrites was approximately 41 Tg in 1973 other sources accounted for about 8 Tg, making a total of 49 Tg (Anon, 1973). Byproduct S from sour-gas, fossil fuel combustion, and other sources now accounts for over 50% of S used by western countries, as shown in Fig. 9.1. This percentage may increase as pollution abatement measures increase the removal of SO2 from fossil fuel, particularly in the U.S.A. Atmospheric S, returned to the earth in rainwater, is also a very important source of S for plants. 

Acetylene is formed when hydrogen is heated with carbon at the temperature of the electric arc, and when most hydrocarbons are decomposed at a high temperature. It is also formed when certain complex organic substances are subjected to destructive distillation at a high temperature. Coal gas contains about. 08 per cent of acetylene, which is formed in this way. Incomplete combustion of hydrocarbons and other organic compounds leads to the formation of the gas. Acetylene is formed in small quantity when a Bunsen burner strikes back and the gas burns at the base in a supply of air which is not sufficient for complete combustion. The odor of the gases formed is not that of pure acetylene, but of other substances present. 

The hrst hve chapters (Part 1) present an overview of some methods that have been used in the recent hterature to calculate rate constants and the associated case studies. The main topics covered in this part include thermochemistry and kinetics, computational chemistry and kinetics, quantum instanton, kinetic calculations in liquid solutions, and new applications of density functional theory in kinetic calculations. The remaining hve chapters (Part II) are focused on apphcations even though methodologies are discussed. The topics in the second part include the kinetics of molecules relevant to combustion processes, intermolecular electron transfer reactivity of organic compounds, lignin model compounds, and coal model compounds in addition to free radical polymerization. 

The sulfur presents in both inorganic and organic forms in coal. The inorganic sulfur occurs as sulfide minerals (pyritic sulfur, FeSj) and/or a range of sulfate compounds (sulfate sulfur). Pyritic and organically bound sulfur constitute the majority of sulfur content, and sulfates are at very low concentrations in coal. Approximately 95% of sulfur content is converted to sulfur dioxide (SO2) during the combustion process and a small amount of sulfur trioxide (SO3) is also formed. Sulfur dioxide is a major contributor to acid rain formation and harmful to the plants and soil (lEA, 2003 Breeze, 2005 Miller, 2005 Suarez-Ruiz and Ward, 2008 Franco and Diaz, 2009 Graus and Worrell, 2009). 

Acid gases (SOx and NOx) emitted into the atmosphere provide the essential components in the formation of acid rain. Sulfur is present in coal as both an organic and inorganic compound. On combustion, most of the sulfur is converted to sulfur dioxide with a small proportion remaining in the ash as sulfite ... 

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