Contents of coals

When a suitable reaction involving the analyte does not exist it may be possible to generate a species that is easily titrated. Eor example, the sulfur content of coal can be determined by using a combustion reaction to convert sulfur to sulfur dioxide. 

In the United States there was Httie interest in solvent processing of coals. A method to reduce the sulfur content of coal extracts by beating with sodium hydroxide and zinc oxide was, however, patented in 1940 (116). In the 1960s the technical feasibiHty of a coal deashing process was studied (117),... 

Nuclear magnetic resonance (nmr) is a nondestmctive means of measuring the amount of hydrogen in various materials for example, nmr has been used to determine the hydrogen content of coals (251). 

Humic acids are alkaH-extractable materials and total humic acid content is a term that refers to the humic acid content of coal that has had its carboxylate cations removed with sodium pyrophosphate. Values for some typical AustraHan brown coals range from 24—92% (13). Treatment of lignitic coals with mineral acid to release the alkaH and alkaline cations may dissolve up to 20% of the coal. The naturally moist coals are slightly acidic and have a pH of 3.5—6.5. 

Zinc, like most metals, is found in all natural waters and soils as well as the atmosphere and is an important trace element in plant and animal life (see Mineral nutrients). Rocks of various kinds contain 20—200 ppm zinc and normal soils 10—30 ppm (average ca 50 ppm) in uncontaminated areas. The average zinc content of coal is 33 ppm. Seawater contains 1—27 )-lg/L (median ca 8 p.g/L), and uncontaminated freshwater usually <10 / g/L. 

The pyritic sulfur in coal can undergo reaction with sulfate solutions to release elemental sulfur (see Sulfurremoval and recovery). Processes to reduce the sulfur content of coal have been sought (75). The reaction of coal and sulfuric acid has been used to produce cation exchangers, but it was not very efficient and is no longer employed. Efforts have turned to the use of hot concentrated alkaH in a process called Gravimelt. 

Coal ash is derived from the mineral content of coal upon combustion or utilization. The minerals are present as discrete particles, cavity fillings, and aggregates of sulfides, sulfates, chlorides, carbonates, hydrates, and/or oxides. The key ash-forming elements and compounds are (4,5) ... 

Solid fuels, unlike gases and liquids, are entirely characterized by their composition. For example, coal can be characterized by its carbon, hydrogen, oxygen, sulfur, and nitrogen content. The water and mineral content of coal are also important means of differentiating coals from various sources. 

The sulfur content of coals available to utilities ranges from about 4 percent in high-sulfur coals to less than 1 percent in some Western coals. Although transportation costs maybe higher for Western coals, many Eastern utilities elect to burn Western coals to comply with increasingly stringent SO, regulations. 

One of the most studied of the polyaromatic hydro-carbone (PAH) is benzo(a)pyrene (BaP), which is present in coal tar at coke oven plants. The BaP content of coal tar is between 0.1% and 1 % and it contributes to the serious potential health effects on employees exposed to coke oven emissions. The largest sources of BaP are open burning and home heating with wood and coal. The latter alone contributes 40 percent of all the BaP released each year in the USA. 

Moreover, in coals of a similar carbon level, such as Miike coal, Newdell coal, and Grose valley coal, the reactivity of coal decreases greatly with the increasing inert content of coal. 

Pines, A., Aromatic Carbon Contents of Coals, SRCs, and Residues Were Determined by CP-l C-NMR", Under a Subcontract to EPRI, RP-410-1. 

Unfortunately, pyrite sulfur makes up only half the sulfur content of coal, while the other half is organically bound. Coal gasification is the only means by which this sulfur mode can be removed. Of course, it is always possible to eliminate the deleterious effects of sulfur by removing the major product oxide S02 by absorption processes. These processes impose large initial capital investments. 

Recent work reported a method for estimating the mineral content of coals based on the electron-mlcroprobe-determlned chemical composition of discrete particles. (1,2) Each particle Is assumed to contain only one mineral component. Possible ambiguities In qualitative Identification of discrete mineral particles can be eliminated by XRD analyses of the bulk material to Identify the minerals present. For most geological materials, such separations are not readily obtainable. Thus, this method Is limited to materials that can be dispersed Into particles composed of single minerals. 

H/C = atomic hydrogen-to-carbon ratio V = vitrinite content of coal VM volatile matter St = total sulfur TRM = total reactive macerals The adequacies of these reactivity correlations, expressed as a percentage of the total variation in the data set explained by the model, were 80.0%, 79.2%, and 47.5% respectively. A later paper in the series (21) concentrated on the development of reactivity correlations for a set of 26 high volatile bituminous coals with high sulfur contents, and extended the models previously developed in include analyses of the liquefaction products and coal structural features. These structural features included the usual... 

Simultaneous Determinations of Sulfur and Heat Content of Coal 194... 

The accompanying table shows how the trace metal content of coal-ash aerosols depends on particle size 1 ... 

The sulphur content of coals, oils, tars, asphalts, etc., may be determined by combustion in an oxygen bomh, a little ammonium nitrate being added to the charge to ensure complete oxidation to sulphuric acid (see p. 136).5 After washing out the bomb the sulphur is determined as barium sulphate. 

There are significant differences in the carbonate mineralogy of coals from different parts of the world. Calcite is nearly the only carbonate mineral observed in Illinois coals (1) whereas ankerite is the dominant carbonate mineral in British coals (5,6), and siderite, ankerite, and calcite are common in Australian coals (7). The carbonate minerals make up 9% of the total mineral matter content of coals from the Illinois Basin (1). 

Zubovic, P., Minor Element Content of Coal from Illinois Beds 5 and 6... 

TJecent interest in the trace element content of coal has increased the need for rapid and accurate analytical methods for their determination. Because x-ray fluorescence analysis has demonstrated its usefulness in determining major, minor, and trace elements in numerous other types of materials, it was felt that this method could be extended to trace element determinations in whole coal. In the past, such analyses were seriously hampered by the lack of standard samples. However, research being conducted in our laboratories under the sponsorship of the U. S. Environmental Protection Agency produced a large number of coal samples for which trace elements had been determined by two or more independent analytical procedures, for example, optical emission, neutron activation, atomic absorption, and wet chemical methods. These coals were used as standards to develop an x-ray fluorescence method that would determine many trace and minor elements in pressed whole coal samples. 

Small-scale, tabletop nuclear fusion devices, known as compact accelerator neutron generators, are routinely used as a source of neutron radiation. By design, however, these devices consume more energy than they release. The beam of neutrons generated by these devices can be used to identify the elemental composition of amaterial.The coal industry uses such beams to measure the sulfur content of coal in real time as the coal moves over conveyor belts. The cement industry similarly uses these beams to judge the quality of cement mixes. These fusiongenerated neutrons are also used to identify the elemental composition of nuclear wastes and for the detection and identification of explosives. 

Figure 7 shows several curves which have been proposed to relate carbon content of coals to the a-axis crystallite size (4, 5, 11, 19, 24). Curves I and II are based on criteria now superseded and are considered to be obsolete. From these data, layer diameters between 8 and 9 A. are suggested for the anthraxolite (94% C). Since these values are close to the c-axis lengths (which as reported above may be too large), it is felt that typical crystallites of the anthraxolite may be nearly equidimensional cylinders. 

Figure 12. Relations of specific gravity and carbon content of coals to carbonization temperature. After MacFarlane (24). Dashed lines give parameters of Martinsburg anthraxolite...

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