Proximate analysis

The proximate analysis of coal is presented as a group of test methods (ASTM D-3172 ASTM D-3173 ASTM D-3174 ASTM D-3175 ASTM D-5142 ISO 1171) that has been used widely as the basis for coal characterization in connection with coal utilization. These analyses are in contrast to the ultimate analysis of coal, which provides information about the elemental composition. 

The standard test method for proximate analysis (ASTM D-3172) covers the methods of analysis associated with the proximate analysis of coal and coke and is, in fact, a combination of the determination of each of three of the properties and calculation of a fourth. Moisture, volatile matter, and ash are all determined by subjecting the coal to prescribed temperature levels for prescribed time intervals. The losses of weight are, by stipulation, due to loss of moisture and, at the higher temperature, loss of volatile matter. The residue remaining after ignition at the final temperature is called ash. Fixed carbon is the difference of these three values summed and subtracted from 100. In low-volatile materials such as coke and anthracite coal, the fixed-carbon value equates approximately to the elemental carbon content of the sample. 

The term volatile matter content (of coal) is actually a misnomer, insofar as the majority of the volatile matter is the volatile product of the thermal decomposition of coal through the application of high temperatures. The extent to which the more volatile smaller molecules of coal (Vahrman, 1970) add to this is dependent on the coal and should be determined by nondestructive methods such as extraction by solvent(s). Relative yields and boiling-point profiles provide the extent to which natural molecules contribute to the volatile matter without any influence from high-temperature cracking. 

the objective of the proximate analysis is to determine the amount moisture, volatile matter yield, ash yield, and fixed carbon from the coal sample. Mineral matter is not directly measured but may be obtained by one of a number of empirical formula either from the yield of mineral ash or from data derived from the ultimate analysis. 

The variables are measured in percent by weight (% w/w) and are calculated in several different 

FIGURE 8.5 Data types obtained from (a) proximate analysis and (b) ultimate analysis. 

Moisture is an important property of coal, as all coals are mined wet. Groundwater and other extraneous moisture are known collectively as adventitious moisture and are readily evaporated. Moisture held within the coal itself is known as inherent moisture and is analyzed. Moisture may occur in four possible forms within coal  

As a result of these several forms, the quantitative measuranent of water is complicated because the water is present within the coal matrix in more than one form (AUardice and Evans, 1978). The total moisture in coal may be determined by means of a single-stage method or by means of a two-stage method in which the as-received sample is air-dried at approximately room temperature and the residual moisture is determined in the sample (ASTM, 2011v ISO, 20111). 

It is the determination of (a) Moisture content (b) Volatile matter (c) Ash content and (d) Fixed carbon. The analysis is consumer oriented and empirical in nature. The results vary with the procedure adopted and have no absolute significance. However, when the analysis is carried out in accordance with standard specifications (British Standard or American Society for Testing and Materials, ASTM), it gives reproducible results which are essential to assess the suitability of the fuel for a particular domestic or industrial use. 

To get a first overview on the quality of the coal, the proximate analysis is carried out resulting in values for  

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The proximate analysis of charcoal is 20-25% volatile matter, 70—75% fixed carbon, and 5% ash. Charcoal briquets have lower heating values than charcoal lumps, because of additives in the briquets. The higher heating value of lump charcoal is - 28 kJ/kg (12,000 Btu/lb). The higher heating value of briquets is 23 to 25 kj/kg ( -- 9,900-10,800 Btu/lb). 

Analysis. The proximate analysis is based on determinations of volatile matter, moisture, and ash for a coal sample. Fixed carbon is then calculated by difference. Volatile matter is determined empirically by measuring the weight loss when coal is heated in a covered cmcible at either 950°C (ASTM D3175 or D5142) or 900°C (BS). 

Typical proximate-analysis data for the combustible components of industrial and municipal sohd wastes are presented in Table 25-52. 

TABLE 25-52 Typical Proximate-Analysis and Energy-Content Data for Components in Domestic/ Commercial/ and Industrial Solid Waste ... 

Fixed carbon, the residue left after the volatile matter is driven off, is calculated by subtrac ting from 100 the percentages of moisture, volatile matter, and ash of the proximate analysis. In addition to carbon, it may contain several tenths of a percent of hydrogen and oxygen, 0.4 to 1.0 percent nitrogen, and about half of the sulfur that was in the coal. 

Proximate analysis - a relatively low-cost analysis in which moisture content, volatile combustible matter, fixed carbon, and ash are determined. The fuel value of the sludge is calculated as the weighted average of the fuel values of its individual components. 

Qosil, . . Coa3> lty type Ultimate analysis (d. a. f. ) Proximate analysis VC s) Inerts... 

Original Ultimate analysis (d.a.f.) Proximate analysis Characteristics Conv. (50... 

Coal NCB Coal rank code (CRC) Proximate analysis (ar) ana Ultimate Lysis % (dmmf) ... 

Each of these is reported in the proximate analysis. Coal analyses can be reported on several bases as-received, moisture-free (or dry), and mineral-matter-free (or ash-free). 

Table V. Proximate Analysis (%) Cottonseed Flakes of Defatted Cottonseed and Cot-n-nuts Flour,...

Utilizing proximate analysis data on all blend constituents and... 

Table 6.12 shows the proximate analysis data and higher heating values (HHV) of samples. The HHV (MJ/kg) of the moss and alga samples as a function of fixed carbon (FC), wt.% can be calculated from ... 

A number of studies have been carried out, describing the main chemical composition of the edible part of the decorticated morama bean (T. esculentum) and few samples of T. fassoglense have also been included. A literature survey of the performed proximate analysis is summarized in Table 5.2. 

By 1750 the realm of the neutral salts had become the most secure, the most explicitly empirical of all chemical knowledge. It has provided the evidence which most securely demonstrates the doctrine of affinities, the operating concept of proximate analysis, the confirmation of composition by the cycle of analysis and synthesis. The chemistry of neutral salts was to become the empirical core of the new nomenclature that organized the new chemistry of the chemical revolution. 

Polymer Selection. The selection of corn starch as the starting material was made due to its low cost, ready availability, multitude of previous derivatization literature work and favorable chemical and physical properties (i.e., inert, readily deriva-tized homopolysaccharide capable of forming high solids content aqueous dispersions with relatively low viscosities). The corn starch used in this study was purchased in bulk from a local food cooperative. Table I gives the proximate analysis of a typical corn starch. 

The coal service laboratory, which in the past was concerned with determining the ASTM Procedures for Ultimate and Proximate Analysis, is now responsible for analyzing trace elements in coal. With this sort of facility and technical skill in mind, our own wet chemical laboratory devised relatively routine procedures for determining trace elements in coal that could have an undesirable environmental impact including Hg, Be, Se, As, Cd, Pb, F, Cu, Ni, Zn, Cr, Te, Ge, Mn, Sn, B, Bi, Sb, V, Li, Co, and Ag. 

Table III. Proximate Analysis of Coal Consumed During Test Period ...

We have investigated the humification of straw, as an example, under constant conditions of humidity and temperature in a climatic chamber (4,18) and separated different fractions according to a modified method of Waksman s proximate analysis. The amount of nitrogen present in these processes is the factor limiting the rate of decomposition. Therefore we added nitrogen in form of ammonium nitrate in a quantity of 1% of straw dry weight to a nutrient solution in one experiment while the nutrient solution had no nitrogen in a parallel experiment. Table I shows the calculated data. 

Most of the analyses of Antarctic coal were based on blocks of transportable size taken from surface outcrops. In earlier work, sections of purer coal were cut from the blocks and submitted for analysis. In later work, selected blocks were crushed, and a float fraction of purer coal was submitted to provide analytic data from each deposit. These samples, while not useful for determining coal grade, may be adequate for indicating rank. Practically all of the Antarctic coal, with the exception of that at Amery (which may represent high volatile bituminous coal), corresponds to medium volatile bituminous or higher rank. The high apparent rank Antarctic coal may be classified according to conventional ASTM standards of rank based on proximate analysis, but it seems clear that these results serve only as a first approximation. 

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