Coal oxidized

Seam correlations, measurements of rank and geologic history, interpretation of petroleum (qv) formation with coal deposits, prediction of coke properties, and detection of coal oxidation can be deterrnined from petrographic analysis. Constituents of seams can be observed over considerable distances, permitting the correlation of seam profiles in coal basins. Measurements of vitrinite reflectance within a seam permit mapping of variations in thermal and tectonic histories. Figure 2 indicates the relationship of vitrinite reflectance to maximum temperatures and effective heating time in the seam (11,15). 

Coal Oxidation. The coal samples, ground to -325 standard mesh, were subjected to oxidation in the laboratory by heating them at 383 K in an air oven for 16 hours. This treatment will be referred to as "air oxidation" and the coal sample thus treated will be referred to as oxidized coal. 

Figure 9. Infrared spectra of samples of resinite from a bituminous coal oxidized at 140°C. for different periods of time...

In this paper, we demonstrate how mean maximum reflectance of vitrinite in oil (hereafter referred to as R ) can be used in place of conventional chemical-rank parameters (volatile matter and fixed carbon) to estimate the relative yields of carbonization products, specific properties of gas produced by carbonization, and chemical properties of coal such as calorific value and free swelling index (FS1). Further, we illustrate that measured R can be used to detect coal oxidation, to categorize coals for certain combustion uses, and to help classify coals by rank. 

A Study of Coal Oxidation by Charged-Particle Activation Analysis... 

Kawamura, K. et al. Separation of aromatic carboxylic acids using quaternary ammonium salts on reversed-phase HPLC 2 application for the analysis of Loy Yang coal oxidation products. J. Sep. Sci. Technol. 2006,41, 723-732. 

The modified nonadiabatic method described for the determination of the spontaneous combustion liability of subbituminous coals can yield satisfactory results. However, a more realistic measurement of a coal s self-heating tendency might be obtained through the use of an adiabatic system. In this case, heat derived from the coal oxidation would not be transferred to the surroundings. A spontaneous combustion instrument intended for field or lab/mine applications should be less complex, yet it should be capable of producing data that is reasonably accurate for predicting the self-heating characteristics of coals. 

Some acids not found in oxidation products of lignins, land plants, and marine sediments were found in the oxidation products of coals. Among these were phenolic di- and tricarboxylic acids and hydroxy-naphthalenecarboxylic acids. From some soil fulvic and humic acids, phenolic poly carboxylic acids have been found in the oxidation products together with considerable amounts of fatty acids. Therefore, phenolic esters of fatty acids are considered to be present in these soil acids (6, 27). However, little or no fatty acids were observed in the coal oxidation products. 

The oxidation of methyl groups of aromatic compounds by CuO-NaOH has been found to be ineffective. Therefore, relatively large amounts of methyl-substituted phenolic and benzene carboxylic acids were isolated from the coal oxidation. 

This picture has been broadly validated, and in some respects refined, by other work in which coal was depolymerized by acid-catalyzed transalkylation [as by interaction of coal with phenol and BF3 (23-27)] or by similar, less clearly defined, phenolation reactions (28-31), or selectively degraded by specific oxidants, such as dichromates (32-34), hypohalites (35-38), or peroxy-acids (39-43). But these studies have also revealed some previously unsuspected features. Buffer-controlled oxidation with Na2Cr207 (34) and KMn04 (44) have indicated an occasionally significant presence of straight-chain (up to C21) and branched-chain (up to C8) aliphatic compounds in coal. Oxidation with performic acid (41-43) has yielded substituted compounds that are clearly related to the microbial or chemical degradation products of lignin or flavonoids. And when applied to supposedly very similar coals, virtually identical depolymerization or oxidation procedures often furnished distinctly different product slates (45). 

Under the natural conditions of weathering, slow oxidation of coal occtrrs with the formation of carbon suboxide and no, or very little, carbon dioxide is generated (Davidson, 1990). The heat release accompar ing coal oxidation to the polymerized substance can be described as... 

Use relation (10-54) to estimate the front velocity of solid-state (coal) oxidation at low temperatures. How does the oxidation front velocity depend on temperature Which effects determine the temperature limit for acceleration of the oxidation front In which way does nonequilibrium plasma stimulate the process ... 

Figure 4. FTIR study of coal oxidation. Key A. FTIR spectrum of oxidized PSOC 377 coal (HVA) (1 h, 150°C in air) B, FTIR spectrum of fresh coal A—B,...

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