Coal, analyses sampling

The water in coal is bound in different forms to its constituents. It can be divided into three types (1) Free moisture, also referred to as external moisture, superficial moisture, or the primary moisture fraction, which is present in large cracks and capillaries. Water bound in this way retains its normal physical properties. (2) Inherent moisture, also referred to as internal moisture or the secondary moisture fraction, whose vapor pressure is lower, since it is absorbed within the pore structure of the coal. (3) Water of constitution, which is mainly combined with mineral matter normally present in coal. This water is generally driven off only at temperatures higher than those normally used for the determination of moisture content. Standard methods do not make use of these terms and define (1) the total moisture content of a coal and (2) the moisture content of the coal analysis sample. Total moisture determination must be made over the sample as received in the laboratory, in an air-proof recipient. The determination consists in drying in an oven at 105 °C till constant weight. Its value is of huge interest both in international and domestic coal trade (ISO 589, ASTM D3173). 

Figure 12.23 SFC-SFC analysis, involving a rotaiy valve interface, of a standard coal tar sample (SRM 1597). Two fractions were collected from the first SFC separation (a) and then analyzed simultaneously in the second SFC system (h) cuts a and h are taken between 20.2 and 21.2 min, and 38.7 and 40.2 min, respectively. Peak identification is as follows 1, tii-phenylene 2, chrysene 3, henzo[g/ i]perylene 4, antliracene. Reprinted from Analytical Chemistry, 62, Z. Juvancz et al, Multidimensional packed capillary coupled to open tubular column supercritical fluid chromatography using a valve-switcliing interface , pp. 1384-1388, copyright 1990, with permission from the American Chemical Society.

FPN) See Standard Test Method for Volatile Materials in the Analysis Sample for Coal and Coke, ASTM D 3175-1989. 

The key word in any case is representative. A laboratory analysis sample must be representative of the whole so that the final result of the chemical analysis represents the entire system that it is intended to represent. If there are variations in composition, such as with the coal example above, or at least suspected variations, small samples must be taken from all suspect locations. If results for the entire system are to be reported, these small samples are then mixed and made homogeneous to give the final sample to be tested. Such a sample is called a composite sample. In some cases, analysis on the individual samples may be more appropriate. Such samples are called selective samples. 

Acenaphthene occurs naturally in coal tar. Based on laboratory analysis of 7 coal tar samples, acenaphthene concentrations ranged from 350 to 12,000 ppm (EPRl, 1990). Detected in Dyr aged coal tar film and bulk coal tar at concentrations of 5,800 and 5,900 mg/kg, respectively (Nelson et al, 1996). A high-temperature coal tar contained acenaphthene at an average concentration of 1.05 wt % (McNeil, 1983). Lee et al. (1992a) equilibrated 8 coal tars with distilled water at 25 °C. The maximum concentration of acenaphthene observed in the aqueous phase was 0.3 mg/L. 

Based on laboratory analysis of 7 coal tar samples, aniline concentrations ranged from ND to 13 ppm (EPRl, 1990). 

Based on laboratory analysis of 7 coal tar samples, benzo[i]fluoranthene concentrations ranged from 350 to 3,000 ppm (EPRl, 1990). Identified in high-temperature coal tar pitches used in roofing operations at concentrations ranging from 1,670 to 4,500 mg/kg (Malaiyandi et al, 1982). 

The concentration of benzo[ / r]peiylene in coal tar and the maximum concentration reported in groundwater at a mid-Atlantic coal tar site were 1,200 and 0.002 mg/L, respectively (Mackay and Gschwend, 2001). Based on laboratory analysis of 7 coal tar samples, benzo[,g / /]perylene concentrations ranged from ND to 1,900 ppm (EPRI, 1990). Benzo[,g / /]perylene was reported in a high-temperature coal tar pitch used in roofing at concentrations ranging from 754 to 3,980 mg/kg (Malaiyandi et al., 1982). 

Source Based on laboratory analysis of 7 coal tar samples, styrene concentrations ranged from ND to 2,500 ppm (EPRI, 1990). A high-temperature coal tar contained styrene at an average concentration of 0.02 wt % (McNeil, 1983). 

Two types of coal ash samples have been prepared routinely for analysis at the Illinois Geological Survey. Low-temperature ash samples (12), in which the bulk of the mineral matter remains unchanged, are prepared by reaction of the coal with activated oxygen in a radiofrequency field. The effective temperature produced by this device is approximately 150 °C. Such samples were unsatisfactory for emission spectroscopic analysis. It is postulated that the presence of largely unaltered mineral matter, such as carbonates, sulfides, and hemihydrated sulfates (12), caused the observed nonreproducibility of results. High-temperature ash samples, prepared in a muffle furnace, consisted mainly... 

Choice of an Internal Standard. One of the difficulties in the spec-trometric trace analysis of coal ash samples, in addition to choosing a suitable comparison standard matrix, is choosing an internal standard. The first choice in both analytical methods was indium, which was used as a constant internal standard added to the graphite powder diluent-buffer. The results obtained had poor reproducibility, as previously... 

Statistical Results from the Analysis Methods. Continuous time vs. relative intensity curves were made spectrometrically for each of 11 elements in seven different coal ash samples. The results showed that peak intensities for all the elements in each sample were generally reached between 50 and 60 sec after initiation of the arc. This behavior helps to explain why using iron as the variable internal standard was successful for the normally wide range of volatilities represented. The large dilution factor involved or a possible carrier distillation effect of barium nitrate might explain the almost complete absence of fractional volatilization. 

The bulk of the samples for this study came from TVA s Allen Steam Plant at Memphis, Tenn. The sampling points (Figure 4) included inlet air, coal, bottom ash, precipitator inlet, and outlet at the 268-ft stack level. During the 2-week sampling period the unit was operated under steady state conditions at 240 MW (12) with a uniform coal supply so that a mass balance might be established for a number of elements. All the coal from southern Illinois was washed and crushed so that 90% was less than 4 mesh. Nominal coal analysis indicated the following composition 9.5% moisture, 34% volatiles, 43% fixed carbon, 13% ash, and 3.4% sulfur. 

Methods and technology were developed and used at the NASA Plum Brook Reactor (PBR) to analyze trace elements in pollution-related samples by instrumental neutron activation analysis (INAA). This work is significant because it demonstrates that INAA is a useful analytic tool for monitoring trace elements in a variety of sample matrices related to environmental protection. In addition to coal, other samples analyzed for trace elements included fly ash, bottom ash, crude oil, fuel oil, residual oil, gasoline, jet fuel, kerosene, filtered air particulates, various ores, stack... 

Mercury recovered in the ash probably represents mercury in the siliceous portion of the ash and mercury adsorbed onto the surface of the ash particles as the gas stream cools. Preliminary investigations showed that the coal analysis method does not account for all the mercury in the ash. This is a result of the significantly higher silicate concentration in the ash. In addition, the higher temperature ashes have a lower mercury concentration requiring a larger sample size for analysis. Because of these properties of the ash, the coal analysis method was modified to revolatilize the mercury quantitatively in the ash. 

Work continued in 1960-1963 in the Ohio Range (formerly called the Central Range of the Horlick Mountains) to procure coal for accurate analysis. Samples of outcrop coal and one excellent sample of coal from an adit opened in one bed were collected. Coal samples were taken in 1959 by John J. Mulligan (31) at Mount Gran in the vicinity of Frank Debenham and McKenzie Taylor s old Mount Suess locality. The following season Mulligan (32) sampled coal farther inland in the Willett Range. Brown and Taylor (6) published an analytic report on coal from the Theron Mountains in 1961. 

All analyses of Antarctic coal samples submitted from the U.S. Geological Survey have been analyzed at the U.S. Bureau of Mines, Coal Analysis Section under supervision of Forrest E. Walker. Preparation of samples for analyses as well as field sampling and shipment was supported, in part, by NSF grant G-17216 administered by the Institute of Polar Studies through the Research Foundation, The Ohio State University. 

Moisture. The moisture determinations are not very reliable since the coals were sampled and then shipped to the laboratories at The Pennsylvania State University for this study. Several months elapsed between the time of sampling and analysis. However, the moisture determinations do provide some basis to demarcate the zones which are highly absorbent. The moisture content ranges from 1.58 to 10.01% in Seam 4 and from 2.07 to 9.47% in Seam 2. 

Proximate analysis, determination of moisture content of the general analysis sample of coke Proximate analysis, determination of volatile matter content Proximate analysis, determination of ash content Determination of gross calorific value Ultimate analysis of coal and coke, determination of carbon and hydrogen content, high temperature combustion method Liebig method... 

The issue of testing for bias in a coal sampling system (ASTM D-6518 ISO 13 909) is an essential part of coal analysis and is of significant importance (Gould and Visman, 1981). Accordingly, the term bias represents the occurrence of a systematic error (or errors) that is (are) of practical importance. 

ASTM D-3173. Standard Test Method for Moisture in the Analysis Sample of Coal and Coke. 

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