Coal, properties

Pieces of coal are mixtures of materials somewhat randomly distributed in differing amounts. The mineral matter can be readily distinguished from the organic, which is itself a mixture. Coal properties reflect the individual constituents and the relative proportions. By analogy to geologic formations, the macerals are the constituents that correspond to minerals that make up individual rocks. For coals, macerals, which tend to be consistent in their properties, represent particular classes of plant parts that have been transformed into coal (40). Most detailed chemical and physical studies of coal have been made on macerals or samples rich in a particular maceral, because maceral separation is time consuming. 

Physical Properties. Most of the physical properties discussed herein depend on the direction of measurement as compared to the bedding plane of the coal. Additionally, these properties vary according to the history of the piece of coal. Properties also vary between pieces because of coal s britde nature and the crack and pore stmcture. One example concerns electrical conductivity. Absolute values of coal sample specific conductivity are not easy to determine. A more characteristic value is the energy gap for transfer of electrons between molecules, which is deterrnined by a series of measurements over a range of temperatures and is unaffected by the presence of cracks. The velocity of sound is also dependent on continuity in the coal. 

Corrosion. The primary coal properties affecting corrosion are sulfur and chlorine levels. The range of sulfur levels in Table 2 shows a low of 0.3% for SUFCo and a high of 5.2% for petroleum coke. R F coal has 4.2% sulfur. The highest chlorine level in this group of coals is 0.41% for Pyro No. 9 coal. 

Coal properties influence pulverizer capacity and the sizing of the air heater and other heat-recovery sections of a steam generator. Furnace size and heat-release rates are designed to control slagging characteristics. Consequently, heat-release rates in terms of the ratio of net heat input to plan area range from 4.4 MW/m" (1.4 X 10 Btii/[h ft ]) for severely slagging coals to 6.6 MW/m (2.1 X 10 Btii/[h ft ]) for low-slagging fuels. 

Coal properties (range, degree and permeability) determine the suitability of the site, either for storage or storage with only CH4 recovery. 

Day S., Duffy G., et al. Effect of coal properties on C02 sorption capacity under supercritical conditions. 2008 International Journal of Greenhouse Gas Control 2(3) 342-352. 

A statistical study of the conversion with tetralin of 68 coals (60) must now be regarded as superseded by a later, more comprehensive paper (61), but it did show very clearly that bivariate plots are of little value in interrelating liquefaction behavior with coal properties at least two or three coal properties must be taken into account in seeking to explain the variance of liquefaction behavior, and some of these properties are not related to the rank of the coal. The paper implies strongly that any interrelationships of coal characteristics must necessarily be multivariate. Hence in any study of coal a large sample and data base is essential if worthwhile generalizations are to be made. 

Principal components analysis of the characteristics of the coals in each of the three groups showed that the interrelationships between coal properties were markedly different that is, the trends of properties with increasing rank are different, in... 

South African coals differ from most Northern Hemisphere coals in their geological age, unusual petrology and their high mineral matter content. If these coals are to be used for conversion to synthetic fuels then criteria must be found to enable predictions of their behaviour under liquefaction conditions to be determined. This paper describes the hydrogenation of a number of South African coals using two different techniques, to ascertain whether well known coal properties can be used to predict their hydrogenation behaviour. 

Experimental Two different experimental procedures were used in this study, to identify the coal properties of importance in coal conversion which are independent of processing conditions. These were ... 

The effect of the following coal property parameters was studied in relation to liquid yields and conversions during coal hydrogenation using both experimental procedures. 

Cost of GasificatUm-Tiased Power Systems Comparing power options is complicated by the many different parameters that must be considered in making a cost determination coal cost coal properties, inclnding sulfur and moisture contents ambient temperature degree of process integration gas turbine model and gas cleanup method. These, and many other factors, have a significant impact on cost. 

Correlation of Coal Properties with Hydroliquefaction Reactivity A Brief Review... 

Since the earliest days of coal liquefaction processing and research, the need for correlations of coal properties with coal reactivity under direct hydroliquefaction conditions has been recognized by coal scientists. This article traces the history of reactivity correlations from the earliest work of Bergius through the classic work at the Bruceton Bureau of Mines during the 1940 s to the most recent advances in this subject. Particular emphasis in this review is placed on an examination of the contributions of Professor Peter Given and his co-workers. Reactivity methodologies and techniques for correlation are presented and critically evaluated for utility and applicability as predictive tools. 

Many of the compositional parameters utilized as independent variables in the work cited above represented derived coal properties rather than fundamental chemical features. Further, variables traditionally used are often highly correlated with each other (for example volatile matter and hydrogen). As pointed out by Neavel (34) / this limits the utility of such parameters in correlational models. Instrumental techniques such as pyrolysis/mass spectrometry (35.36 C-n.m.r, FTIR, and... 

Coal is an extremely heterogeneous material, both from a macroscopic and microscopic point of view. Correlation of liquefaction reactivity with coal properties is, as a result, inherently difficult and any truly "universal correlations that will be developed will need to be based... 

The Influence of Coal Properties on Behaviour In Conversion Process... 

This paper touches on the chemistry of coal gasification and liquefaction comments on the current status of conversion processes and the influence of coal properties on coal performance in such processes and examines the contributions which coal conversion could make towards attainment of Canadian energy self-sufficiency. Particular attention is directed to a possible role for the medium-btu gas in long-term supply of fuel gas to residential and industrial consumers to linkages between partial conversion and thermal generation of electric energy and to coproduction of certain petrochemicals, fuel gas and liquid hydrocarbons by carbon monoxide hydrogenation. 

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