Comprehensive Investigation of the Liberation Characteristics of Pyrite and Other Mineral Matter from Coal. Semi-annual Progress Report, July 31, 1996--December 31, 1996 PDF Download

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Languages : en
Pages : 16

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A technique has been developed for generating scanning electron microscope images of sections of polished coal and coal particles that are suitable for the measurement of the linear intercept distribution functions and the distribution of three-phase linear grades. The three phases used are; pyrite, ash forming minerals, and coal. The phase-to-phase transition probabilities for the unbroken ore can also be estimated using conventional image analysis techniques. The distribution of linear intercept lengths through the pyrite, ash and coal phases were found to be described by sums of 2, 3 and 4 exponentials respectively. This reflects the presence of distinct textural regions in the coal. The linear grade distributions were determined in 710 - 1000 micron coal particles that had previously been carefully fractionated using dense liquids. The three phase linear grade distributions reflect the variation in particle composition that results from the fractionation and they provide a detailed picture of the three-phase composition of the various fractions. It is not yet possible to stereologically correct these three-phase distributions. However, the measured uncorrected distributions are very encouraging and a viable stereological correction procedure will be developed during the next phase of work on this project.

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Languages : en
Pages : 14

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The objectives of this project are: (1) Develop a set of laboratory techniques for the quantitative measurement of the liberation spectra in samples of coal particles in the size range 50 [mu]m - 1 mm. Three-dimensional spectra will be required to account for the mineral matter and pyrite separately. (2) Establish, experimentally, the Andrews-Mika diagram for a number of typical U.S. coals and to develop an appropriate parameterized description for the Andrews-Mika diagram so that it may be determined easily and quickly for coals of different origin and different type. (3) Establish an effective and reliable simulation technique so that liberation of both pyritic sulfur and ash during comminution operations can be modeled and the operation of coal preparation facilities simulated. These models will be incorporated into a computer simulation system for coal cleaning plants. During this past quarter, a sample of Pittsburgh {number_sign}8 coal was crushed using ultrasonic milling and the progeny fractionated and analyzed, and an Andrews-Mika diagram constructed. While this diagram is qualitatively similar to Andrews-Mika diagrams established for other mineral systems, it illustrates that ash is liberated comparatively slowly during comminution.

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Languages : en
Pages : 5

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Pages : 16

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The objective of this project is the development of methods for the measurement, prediction and modeling of the liberation characteristics of mineral matter and pyrite from coal, and to implement these findings in viable computer-simulation systems for coal cleaning plants. The central thrust of the project will be based on using the Andrews-Mika diagram as a convenient and experimentally verifiable model for the liberation characteristics of the constituents of coal during comminution. In order to establish the Andrews-Mika diagram, it is necessary to develop efficient techniques for density fractionation and for the measurement of the liberation spectrum in products obtained from the comminution of narrow composition fractions of coal. Dense-liquid techniques are used to produce fractionated samples, and image-analysis techniques, using linear-intercept analysis, are used to measure the liberation spectrum. The prediction of the liberation of mineral matter and pyrite from coal after comminution is based on a linear stochastic model for the description of the mineralogical texture and the random fracture pattern associated with the comminution process. Stereological correction of the distribution of linear grades is required for both the measurement and prediction of the true distribution of volumetric grades in the particle population.

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Languages : en
Pages : 14

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This document is the tenth quarterly status report on a project that is concerned with enhancing the transformation of iron pyrite to non-slagging species during staged, low-NO(subscript x) pulverized coal (P.C.) combustion. The research project is intended to advance PETC's efforts to improve the technical understanding of the high-temperature chemical and physical processes involved in the utilization of coal. The work focuses on the mechanistic description and rate quantification of the effects of fuel properties and combustion environment on the oxidation of iron pyrite to form the non-slagging species magnetite. During this report period numerical encoding of a pyrite combustion model was embarked upon. The effort was intended to lead to predictive capabilities with respect to pyrite composition during pulverized coal firing. Many subroutines were written of a FORTRAN computer program to track the fate of a pyrite particle by integrating time-dependent differential equations for species, momentum, and energy conservation. Inputs to the program include fuel-related properties such as particle size and composition, as well as properties of the reactor environment such as oxygen level, temperature, gas velocity, and a set of initial and final positions.

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The objective of this program is to examine slags formed as a result of firing coals with varying concentration levels, size distribution, and orientation of pyrite with regard to mineral matter in the coal in a laboratory furnace. The program tasks are: (1) selection of eight candidate coals; (2) chemical characterization of the coal samples and identification of the pyrite size, distribution, and orientation with respect to other mineral matter and concentration levels; (3) testing of the candidate coals in a laboratory furnace; (4) chemical and physical characterization of the slag and fly ash samples created by the impurities in the coal sample; (5) influence of coal beneficiation on furnace slagging; and (6) analysis of data and identification of parameters influencing the contribution of pyrite to slagging problems. Washing of the Upper Freeport coal from Indiana County, Pennsylvania, was completed by the last quarter of 1983. The washed product was characterized for mineral content, and a combustion test was performed. Kentucky No. 9 from Henderson County, Kentucky, selected as the sixth coal to be investigated, was characterized using size and gravity fractionation techniques and was combusted in the laboratory furnace to evaluate its slagging and fouling potential. The remaining two coals to be characterized and combusted were identified as Illinois No. 5 and Lower Kittanning from Clarion County, Pennsylvania. 80 figures, 27 tables.

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Languages : en
Pages : 13

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The objective of this research is to develop a mechanistic understanding of the oxidation of coal and coal pyrite, and to correlate the intrinsic physical and chemical properties of these minerals, along with changes resulting from oxidation, with those surface properties that influence the behavior in physical cleaning processes. The results will provide fundamental insight into oxidation, in term of the bulk and surface chemistry, the microstructure, and the semiconductor properties of the pyrite. During the fourteenth and fifteenth quarters, flotation tests were done on Upper Freeport coal from the Troutville No. 2 Mine, Clearfield County, Pennsylvania and on coal samples from the Pennsylvania State Coal Bank. The influence of electrode potential on the surface properties of coal pyrite was tested using contact angle measurements on polarized Pittsburgh coal pyrite electrode.

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Pages : 13

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The objective of this research is to develop a mechanistic understanding of the oxidation of coal and coal pyrite, and to correlate the intrinsic physical and chemical properties of these minerals, along with changes resulting from oxidation, with those surface properties that influence the behavior in physical cleaning processes. The results will provide fundamental insight into oxidation, in term of the bulk and surface chemistry, the microstructure, and the semiconductor properties of the pyrite. During the fourteenth and fifteenth quarters, flotation tests were done on Upper Freeport coal from the Troutvill {number_sign}2 Mine, Clearfield County, Pennsylvania and on coal samples from the Pennsylvania State Coal Bank. The influence of electrode potential on the surface properties of coal pyrite was tested using contact angle measurements on polarized Pittsburgh coal pyrite electrode.

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Languages : en
Pages : 14

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During the ninth quarter, electrochemical experiments were done on electrodes prepared from Upper Freeport coal pyrite and Pittsburgh coal pyrite samples provided by the US Bureau of Mines, Pittsburgh Research Center, Pennsylvania. Scanning electron microscopy and energy dispersive X-ray analysis were done to characterize the morphology and composition of the surface of as-received coal, oxidized coal and coal pyrite. In addition, electrokinetic tests were done on Upper Freeport coal pyrite.

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Languages : en
Pages : 14

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The objective of this research is to develop a mechanistic understanding of the oxidation of coal and coal pyrite, and to correlate the intrinsic physical and chemical properties of these minerals, along with changes resulting from oxidation, with those surface properties that influence the behavior in physical cleaning processes. The results will provide fundamental insight into oxidation, in term of the bulk and surface chemistry, the microstructure, and the semiconductor properties of the pyrite. During the thirteenth quarter, wet oxidation tests were done on coal samples from the Pennsylvania State Coal Bank. As-received and oxidized coal samples were studied by Diffuse Reflectance Infrared Fourier Transform (DRIFT) spectroscopy to detect functional groups that might be responsible for changing the hydrophobicity of coal samples. Coal samples from the Pennsylvania State Coal Bank were oxidized for 5 hours at room temperature using 10% H2O2 at pH 1.0, 1.0 M HNO3 or 0.05 M Fe2(SO4)3 at pH 1.0. Details of the experimental procedure used in the wet oxidation tests were provided in our September 30, 1993 report, along with results of ion-exchange analysis and film flotation tests on as-received and oxidized coal samples. Table II shows the weight percentage of carboxylic and phenolic group oxygen generated by oxidation with different treatments, as determined by ion-exchange. DRIFT spectroscopic analysis was done on as-received and oxidized samples to identify different functionalities directly, to supplement the information on carboxylic and phenolic groups obtained indirectly by ion-exchange methods. The procedure for DRIFT analysis was reported in our June 30, 1993 report.