Uses of dielectric spectra and immersional calorimetry in the characterization of low-rank coals
Moisture in low-rank coals is believed to involve at least two fundamentally different mechanisms for binding water to the coal matrix. The objective of our work was to investigate the application of two experimental techniques, dielectric relaxation spectroscopy and immersional calorimetry, to the characterization of moisture content and pore structure of low-rank coals. Dielectric techniques can sometime prove valuable in studying bulk matter containing specific polar molecules. From a theoretical standpoint, a parallel plate capacitor with a vacuum between its electrodes ceases to behave as a pure capacitance (at all frequencies) when a condensed matter dielectric is inserted. If an alternating voltage is applied to the capacitor containing a dielectric, the current and voltage will no longer be precisely ..pi../2 radians out of phase, ..pi../2 being the value for a vacuum-filled capacitor. The degree of departure from ..pi../2 radians as expressed by the angle delta, depends on the lossyness of the dielectric. The process of adsorption (defined as the concentration of a substance on a surface where the substance, the adsorbate, is in a gas or liquid form and the absorbent a solid) is spontaneous and is characterized by a fall in the entropy of the system and a decrease in surface free energy. This necessitates the adsorption process to be exothermic, the resultant energy being referred to as the heat of immersion or heat of wetting. Therefore the exothermic heat liberated when a porous solid is immersed in a liquid is related to the surface energy of the solid and the measurement of it can be used to determine the surface area of various solid samples.
- Research Organization:
- North Dakota Univ., Grand Forks (USA). Energy Research Center
- DOE Contract Number:
- FC21-83FE60181
- OSTI ID:
- 5912302
- Report Number(s):
- DOE/FE/60181-114; CONF-850417-2; ON: DE85003165
- Resource Relation:
- Conference: 189. national meeting of the American Chemical Society, Miami, FL, USA, 28 Apr 1985; Other Information: Portions are illegible in microfiche products
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
COAL
BINDING ENERGY
COMPARATIVE EVALUATIONS
DIELECTRIC PROPERTIES
WETTING HEAT
WATER
CALORIMETERS
EXPERIMENTAL DATA
FREQUENCY DEPENDENCE
TEMPERATURE DEPENDENCE
CARBONACEOUS MATERIALS
DATA
ELECTRICAL PROPERTIES
ENERGY
ENERGY SOURCES
FOSSIL FUELS
FUELS
HYDROGEN COMPOUNDS
INFORMATION
MATERIALS
MEASURING INSTRUMENTS
NUMERICAL DATA
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
010600* - Coal
Lignite
& Peat- Properties & Composition