Volatile matter content coals

It is well known that the characteristics of coal differ widely according to the age of the coal formation as well as to the location of coal, etc. And the reactivity during hydroliquefaction depends on the characteristics of coals. This relationship will he a guidance to select and develop coal mines. Many parameters to indicate the reactivity of coal have heen proposed (l, 2, 2). Among these parameters, carhon content, volatile matter content, value of H/C atomic ratio, reactive macerals content, etc. are reported to he relatively closely related parameters to coal reactivity. However, these relations are usually found only in limited reaction conditions. Therefore, attempts to find better parameters still continue. 

Based on the idea mentioned above, we should pay attention to the quantity of carbon content in the volatile matter in coal. 

Previous investigations (14, 15) have shown that R° increases as the fixed carbon content increases and decreases as the volatile matter content increases. The relation of R to volatile matter for coals included here is similar to that reported by other investigators (14, 15) a progressive increase in R is accompanied by a corresponding decrease in volatile matter content, as shown in Figure 1. 

Others have related fixed carbon and volatile matter content to calorific value (4, 5) and FSI (12). However, we found that reflectance correlated better with these chemical properties (r = 0.95 and 0.87, respectively). Figure 2 shows the relationship between R. and calorific value for the coals in this study. In general the calorific value increases sharply with increases in R. in the 0.5-1.1% range, increases slightly in the 1.1-1.7 R range, then levels off... 

This investigation shows that the average reflectance of vitrinite in coal (Ro) can be used to estimate carbonization product yields, by-product gas properties, chemical properties, oxidation effects, and combustion behavior. Moreover, R along with calorific value and volatile matter content might be employed to classify accurately and consistently coals of all ranks. 

Generally, the decrepitation resistance of anthracites increases with decreasing volatile matter content, but in some cases differences in physical properties of the coals appear to nullify this relation. 

H. R. Linden High temperature pyrolysis of coal with high energy sources seems to follow readily predictable paths similar to hydrocarbon pyrolysis. The effects of pressure, gas atmosphere, reaction time, and the volatile matter" content of the coal bear the same relationship to yields of methane, ethane, ethylene, acetylene, and hydrogen as for simple hydrocarbons. Effective reaction temperature, although not directly measurable, could be estimated by means of a suitable chemical thermometer, such as the C-. H-. -C. H4-H. system which approaches equilibrium very rapidly. As Dr. Given also noted, equating the volatile matter" to the reactive portion of the coal is an oversimplification but adequate for empirical purposes the C H ratio of the coal would probably be more suitable. 

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 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. 

Determination of the volatile matter content of coal (ASTM D-3175 ISO 562) is an important determination because volatile matter data are an integral part of coal classification systems (Chapter 1) and form the basis of evaluating coals for their suitability for combustion and carbonization. The methods for determining volatile matter content are based on the same principle and consist of heating a weighed sample of coal (usually about 1 g) in a covered crucible to a... 

The composition of the volatile matter evolved from coal is, of course, substantially different for the different ranks of coal, and the proportion of incombustible gases increases as the coal rank decreases. Furthermore, in macerals isolated from any one particular coal, the volatile matter content decreases in a specific order thus, exinite produces more volatile matter than vitrinite, which, in turn, yields more volatile matter than inertinite. 

Determination of volatile matter content using a slower heating rate is applicable to a wider variety of coals. However, the values obtained are sometimes lower (1 to 3% absolute) than those obtained from the regular method. This illustrates the empirical nature of this test and the importance of strict adherence to detailed specifications. The complexity of the constituents of coal that undergo decomposition during this test makes it necessary to have wide tolerances for reproducibility and repeatability. 

The specific heat of coal (Table 7.2) usually increases with its moisture content (Figure 7.1), decreases with carbon content (Figure 7.2), and increases with volatile matter content (Figure 7.3), with mineral matter content exerting somewhat less influence. The values for the specific heats of various coals fall into the general range 0.25 to 0.37, but as with other physical data, comparisons should be made only on an equal (e.g., moisture content, mineral matter content) basis. 

The thermal conductivity of coal generally increases with an increase in the apparent density of the coal as well as with volatile matter content, ash content, and temperature. In addition, the thermal conductivity of the coal parallel to the bedding plane appears to be higher than the thermal conductivity perpendicular to the bedding plane. 

An additional property of coal that is worthy of mention at this time is the softening point, which is generally defined as the temperature at which the particles of coal begin to melt and become rounded. The softening point indicates the onset of the plasticity stage and is (as should be anticipated) a function of the volatile matter content of coal. For example, coal that produces 15% w/w... 

Rank property of coal that is descriptive of degree of coalification (i.e., the stage of metamorphosis of the original vegetal material in the increasing sequence peat, lignite, subbituminous, bituminous, and anthracite) (ASTM D-388). Anthracite rank of coal such that on a dry, mineral-matter-free basis, the volatile matter content of the coal is greater than 2% but equal to or less... 

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