Gino A. Irdi

Microscopic study of spheres and microspheres in fly ash

Abstract Spherical particulates in fly ash from two bituminous coals, two subbituminous coals and one lignite have been studied by interference contrast polarized light microscopy (ICT-PLM) and scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS). Most of the glassy spheres were between 8 and 50 μm in diameter. Second phase material was seen on many of the solid sphere surfaces. Microspheres attached to the surfaces of larger spheres were found to have different compositions from that of the host sphere. Microparticulate capture by the larger spheres is a phenomenon that needs more study before the capture mechanism and its efficiency can be understood.

Carbon Dioxide Transport and Sorption Behavior in Confined Coal Cores for Carbon Sequestration

Summary Measurements of sorption isotherms and transport properties of carbon dioxide (CO2) in coal cores are important for designing enhanced coalbed-methane/CO2-sequestration field projects. Sorption isotherms measured in the laboratory can provide the upper limit on the amount of CO2 that might be sorbed in these projects. Because sequestration sites will most likely be in unmineable coals, many of the coals will be deep and under considerable lithostatic and hydrostatic pressures. These lithostatic pressures may reduce the sorption capacities and/or transport rates significantly. Consequently, we have studied apparent sorption and diffusion in a coal core under confining pressure. A core from the important bituminous coal Pittsburgh #8 was kept under a constant, 3D effective stress; the sample was scanned by X-ray computer tomography (CT) before, then while, it sorbed CO2. Increases in sample density because of sorption were calculated from the CT images. Moreover, density distributions for small volume elements inside the core were calculated and analyzed. Qualitatively, the CT showed that gas sorption advanced at different rates in different regions of the core, and that diffusion and sorption progressed slowly. The amounts of CO2 sorbed were plotted vs. position (at fixed times) and vs. time (for various locations in the sample). The resulting sorption isotherms were compared to isotherms obtained from powdered coal from the same Pittsburgh #8 extended sample. The results showed that for this single coal at specified times, the apparent sorption isotherms were dependent on position of the volume element in the core and the distance from the CO2 source. Also, the calculated isotherms showed that less CO2 was sorbed than by a powdered (and unconfined) sample of the coal. Changes in density distributions during the experiment were also observed. After desorption, the density distribution of calculated volume elements differed from the initial distribution, suggesting hysteresis and a possible rearrangement of coal structure because of CO2 sorption.

Pollen and fungal spore sampling and analysis. Statistical evaluations

Statistical evaluations of samples obtained from a Burkard seven-day recording volumetric pollen/spore trap were performed to determine the precision of the sampling and analysis procedures. The reproducibility of co-located traps was also investigated. The results showed that pollen grain transect counting was not significantly different, while fungal spore counting produced statistically different results. There was no statistical difference in the number of pollen and fungal spores counted between the co-located samplers. Reasons for the differences in the fungal spore counts are presented.

Exploratory study of some potential environmental impacts of CO2 sequestration in unmineable coal seams

An initial investigation into the potential environmental impacts of CO2 sequestration in unmineable coal seams has been conducted, focusing on changes in the produced water during enhanced coalbed methane (ECBM) production, using a CO2 injection process (CO2-ECBM). A high volatile bituminous coal, Pittsburgh No. 8, was reacted with synthetic produced water and gaseous carbon dioxide at 40C and 50 bar to evaluate the potential for mobilisation of toxic metals during CO2-ECBM/sequestration. Microscopic and X-ray diffraction analysis of the post-reaction coal samples clearly show evidence of chemical reaction and chemical analysis of the synthetic produced water shows substantial changes in composition. These results suggest that changes to the produced water chemistry and the potential for mobilising toxic trace elements from coal beds are important factors to be considered when evaluating deep, unmineable coal seams for CO2 sequestration.

The petrography and mineralogy of two Indian coals

Abstract Two coals, Kathara bituminous middlings from north-eastern India (Damodar Valley) and Neyveli lignite from south-eastern India (Tamil Nadu), were petrographically characterized. The Kathara sample is a high-ash coal produced in the beneficiation of a bituminous coking coal. It is relatively high in inertinite and mineral matter, with an unusually large amount of iron oxides in the form of hematite, magnetite and hydrated iron oxides. The Neyveli sample is relatively low in ash and sulfur, and consists mostly of the huminite group of macerals, with a considerable amount of liptinite also present. Low-temperature ashes and bottom ash samples of both coals were analysed by X-ray diffraction to help in interpreting the petrographic data. These coals were also tested for combustion characteristics.

Statistical relationship between pyrite grain size distribution and pyritic sulfur reduction in Ohio coal

Abstract This paper presents a statistical relationship between the pyrite particle size distribution and the potential amount of pyritic sulfur reduction achieved by specific-gravity-based separation. This relationship is obtained from data on 26 Ohio coal samples crushed to 14 × 28 mesh. In this paper a prediction equation is developed that considers the complete statistical distribution of all the pyrite particle sizes in the coal sample. Assuming that pyrite particles occurring in coal have a lognormal distribution, the information about the particle size distribution can be encapsulated in terms of two parameters only, the mean and the standard deviation of the logarithms of the grain diameters. When the pyritic sulfur reductions of the 26 coal samples are related to these two parameters, a very satisfactory regression equation ( R 2 = 0.91) results. This equation shows that information on both these parameters is needed for an accurate prediction of potential sulfur reduction, and that the mean and the standard deviation interact negatively insofar as their influence on pyritic sulfur reduction is concerned.

Determination of pyrite particle size distribution in coal by merging analyses of size distributions at different microscopic magnificiations: Optimum allocation of number of observations to different size groups

Abstract In the characterization of particle size distributions, it is often useful to measure the size of smaller particles using optical magnifications that are higher than the magnifications used to measure relatively large particles. This results in an examination of a smaller area in the sample specimen. This paper considers the question of how many fields should be microscopically analysed at different k magnifications to arrive at an efficient estimate of the mean particle diameter (by count). The resolution of this question depends upon the following three factors: 1, the relative sizes of areas scanned under different magnifications; 2, the expected number of particles of a given size range per optical field under a given magnification; and 3, the standard deviation within each size range scanned under the same magnification. A formula is provided for the optimum allocation of field counts at each magnification when measuring particle sizes in various size ranges. Numerical examples are also provided. The discussion in this paper is illustrated by reference to the measurement of pyrite particle sizes in a given coal. It is well known that the size distribution of pyrites in coal influences the potential amount of sulphur reduction that can be achieved by physical coal cleaning methods.

Carbon Dioxide Transport and Sorption Behavior in Confined Coal Cores for Enhanced Coalbed Methane and CO2 Sequestration

Measurements of sorption isotherms and transport properties of CO2 in coal cores are important for designing enhanced coalbed methane/CO2 sequestration field projects. Sorption isotherms measured in the lab can provide the upper limit on the amount of CO2 that might be sorbed in these projects. Because sequestration sites will most likely be in unmineable coals, many of the coals will be deep and under considerable lithostatic and hydrostatic pressures. These lithostatic pressures may significantly reduce the sorption capacities and/or transport rates. Consequently, we have studied apparent sorption and diffusion in a coal core under confining pressure. A core from the important bituminous coal Pittsburgh #8 was kept under a constant, three-dimensional external stress; the sample was scanned by X-ray computer tomography (CT) before, then while it sorbed, CO2. Increases in sample density due to sorption were calculated from the CT images. Moreover, density distributions for small volume elements inside the core were calculated and analyzed. Qualitatively, the computerized tomography showed that gas sorption advanced at different rates in different regions of the core, and that diffusion and sorption progressed slowly. The amounts of CO2 sorbed were plotted vs. position (at fixed times) and vs. time (for various locations in the sample). The resulting sorption isotherms were compared to isotherms obtained from powdered coal from the same Pittsburgh #8 extended sample. The results showed that for this single coal at specified times, the apparent sorption isotherms were dependent on position of the volume element in the core and the distance from the CO2 source. Also, the calculated isotherms showed that less CO2 was sorbed than by a powdered (and unconfined) sample of the coal. Changes in density distributions during the experiment were also observed. After desorption, the density distribution of calculated volume elements differed from the initial distribution, suggesting hysteresis and a possible rearrangement of coal structure due to CO2 sorption.

Preconversion chemistry and liquefaction of coal in the presence of a molybdenum-containing catalyst

Publisher Summary This chapter discusses the interactions of a catalyst and several different solvent media with a bituminous coal at various temperatures. Information on the influence of the catalyst during the early stages of conversion is also presented. The results presented show the importance of a solvent medium in enhancing the primary dissolution of coal at lower reaction temperatures. With a catalyst, the presence of coal-derived products provided the best results under these conditions. Softening and solubilization of the coal are likely the important factors in this regime. Analysis of short time products obtained at 375°C show that a major role of the catalyst in the beginning phases of coal dissolution is to facilitate the transfer of hydrogen to aromatic species in the coal. Catalyst is effective above 375°C when used alone.

PYRITE PARTICLE SIZE DISTRIBUTION AND PYRITIC SULFUR REDUCTION IN CRUSHED COALS: A PRELIMINARY REPORT

ABSTRACT Six bituminous coals were ground to 28, 100, and 400 mesh x 0, and examined by optical automated image analysis (AIA) to estimate their pyrite particle size distributions and degree of liberation (DOL). These data were used to determine the feasibility of estimating specific-gravity-based pyritic sulfur reduction by AIA methods. Preliminary results indicate that further research is warranted. A review of the progress is presented.