Darrell N. Taulbee

The effect of sulfate on the crystal structure of zirconia

Zirconia can be prepared to produce either tetragonal phase or predominantly monoclinic phase upon calcination at 500 °C. The precursors for each phase of zirconias was treated with 1N H2SO4 to produce a sulfated material. The results reveal that sulfation causes the tetragonal phase to be formed for both types of zirconia contrary to the data before sulfation, and sulfation increases the crystallization exotherm by 150 °C.

Quantitative 13C NMR study of structural variations within the vitrinite and inertinite maceral groups for a semifusinite-rich bituminous coal

Abstract To determine the structural variation within vitrinite and inertinite maceral groups, fractions with purities over 90% in vitrinite and semifusinite were obtained by density gradient centrifugation from a medium volatile Australian bituminous coal and the bulk structural compositions of the maceral concentrates were determined by the quantitatively reliable single pulse excitation (SPE) solid state 13C NMR technique. As previously reported for coals and chars, the aromaticities determined by cross polarisation are often lower than those by SPE, due to the unfavourable spin dynamics. As expected, the aromaticities of the vitrinite fractions are significantly lower than those of the semifusinite ones, but the aromaticity, the fraction of non-protonated aromatic carbon and the number of rings per cluster all increase with density within both the maceral groups. The vitrinite and semifusinite fractions contain 3–6 and 9 to over 15 aromatic rings, respectively. Methyl groups account for greater proportions of the aliphatic carbon with increasing density. These structural trends are consistent with the variations evident in random reflectance.

Fluidized bed steam retorting of Kentucky oil shale

Abstract A three-inch (7.6-cm) diameter fluidized bed reactor has been used at the Kentucky Center for Energy Research Laboratory (KCERL), operated by the Institute for Mining and Minerals Research (IMMR), to investigate the fluidized bed retorting characteristics of Kentucky oil shales. Because steam has been indicated to be a reactive pyrolysis gas for both Eastern and Western U.S. oil shales by many, a main objective of the fluidized bed investigation was to determine the effects of steam as a fluidizing medium. This was accomplished by comparing the yields and compositions of the products from steam and N2 retorting under otherwise equivalent fluidized bed conditions. Oil yields obtained from steam fluidization were approximately 2% greater than oil yields obtained from N2 retorting. Steam retorting released significantly more pyritic sulfur from the shale, providing evidence that reduced hydrogen scavenging from the kerogen for H2S production was a possible mechanism for the increased oil production. Steam fluidization resulted in increased oil collection efficiency, and represented the most significant difference between the steam and nitrogen systems. Liquid product quality was similar for both steam and N2 fluidization and the oils were more aromatic, more viscous, higher in density, higher in nitrogen content, and lower in volatility than Fischer Assay oil derived from the same shale.

Application of hot stage micro-FT-i.r. to the study of organic functional group changes during pyrolysis

Abstract A modified Leitz hot stage fitted to a Spectra-Tech microscope and interfaced with a Nicolet 20-SXC Fourier transform infrared (FT-i.r.) analyser was used to collect infrared (i.r.) spectra from a series of heat treated coal or kerogen samples. Hot stage modifications included installation of an i.r. transparent ZnSe cover disc and routing of a microthermocouple to the interior of a 50 μl platinum sample pan. Spectra were collected in the reflected light mode prior to and then during or after heat treatment. This provided a means to monitor organic functional group changes or depletion resulting from heat treatment. Obstacles encountered and their solutions are discussed.

Processing of eastern US oil shale in a multistaged fluidized bed system

Abstract A multistaged processing concept for eastern US oil shale, KENTORT II, integrates dense-phase fluidized bed pyrolysis with fluidized bed gasification and combustion steps. The fluidized bed retort produces enhanced yields for eastern US oil shale by minimizing cracking and coking reactions. Residual carbon and sulphur are converted in the gasification zone to medium-Btu, H 2 - and H 2 S-rich gas, leaving a low sulphur char for combustion. Heat is provided for gasification via recirculating solids from the combustion zone, and for pyrolysis from hot gases and recirculating solids from the gasification zone. Both experimental systems used in this study indicate that carbon and sulphur conversion are sufficiently rapid to proceed under moderate gasification conditions. Coking induced from solids recirculation was small, and particle agglomeration was not observed during combustion.

Predicted CO2 emissions from maceral concentrates of high volatile bituminous Kentucky and Illinois coals

Abstract A large collection of well-characterized coals, documented in the Center for Applied Energy Researchs (CAER) database, was used to estimate the CO 2 content of maceral concentrates from Kentucky and Illinois high volatile bituminous coals. The data showed no correlation between CO 2 versus coal ranks and between CO 2 versus maceral content. Subsequently, eight sets of low-ash density-gradient centrifugation (DGC) maceral concentrates from five coal beds were examined, spanning in the high volatile rank range. Heating value was not determined on the concentrates, but instead was calculated using the Mott–Spooner formula. There was a good correlation between predicted CO 2 and maceral content for the individual iso-rank (based on vitrinite reflectance, analyzed on whole (parent) coal) sets. In general, the predicted CO 2 increases from liptinite-rich through vitrinite-rich to inertinite-rich concentrates (note: no “concentrates” are absolutely monomaceral).

Petrography of liquefaction residues: semifusinite concentrates from a Peach Orchard coal lithotype, Magoffin County, Kentucky

Abstract Liquefaction of a semifusinite-rich lithotype of the Peach Orchard coal from Magoffin County, Kentucky, indicated conversions at high temperatures and long residence times was a consequence of vitrinite, liptinite, and semifusinite reactivity. The percentage of oils and gases were similar to that produced at lower severity from a Springfield (Western Kentucky No. 9) coal. Semifusinite is converted to vitroplast and anisotropic semicoke in the liquefaction of an DGC inertinite concentrate and to anisotropic semicoke in the liquefaction of the parent coal. Granular residue increases in concentration in the higher severity residues.

Examination of micrinite concentrates from the Cannel City coal bed of eastern Kentucky : proposed mechanism of formation

Abstract A high volatile B, micrinite-rich bituminous coal from Morgan County, Kentucky, was crushed and screened to −100 mesh, demineralized and subjected to density gradient centrifugation (DGC). In an initial density separation, micrinite concentration was increased from 52 vol% in the demineralized coal to a maximum of 67% in the 1.25–1.26 g/ml density fraction. Micrinite enriched fractions (1.21–1.29 g/ml) were combined to yield a sample containing ∼61% micrinite. This sample was crushed to −200 mesh in an attempt to enhance micrinite liberation then reprocessed by DGC. Reprocessing resulted in a slight increase in purity to 69 vol% in the 1.25–1.28 g/ml density fraction. The original −100 mesh sample was density separated a second time with the material recovered between 1.22 and 1.30 g/ml combined, crushed, screened past 325 mesh and reprocessed by DGC. Micrinite was recovered at a purity ranging up to 73% (1.27–1.28 g/ml) from the −325 mesh sample. A density of 1.26g/ml and H/C atomic ratio of 0.79 was calculated for micrinite in one of the higher purity micrinite fractions. These values are notably different than published fusinite values and are more similar to vitrinite values measured in high volatile-B coals. The results from this study suggest that the partitioning of micrinite to a density near that of vitrinite was governed by the inherent micrinite density and not particle aggregation. Transition of the micrinite precursors through a mobile liquid phase is proposed as an explanation for the discrepancy between chemical properties and reflectance as well as to account for the observed microlithological occurrences of micrinite in this sample.

Testing of an Irati oil shale in a multi-stage fluidized bed retorting process

Abstract A Permian Irati oil shale from Brazil was tested in a 7.6cm diameter prototype of the Kentort II process which is a multi-stage fluidized bed retort containing pyrolysis, gasification and combustion zones. To facilitate comparisons, test conditions were maintained similar to those from a recent study utilizing a Devonian shale (Cleveland Member of the Ohio Shale) from Kentucky. The Irati shale was processed with all three zones of the process in operation and solid recirculation was used to transfer heat throughout the reactor. Generally, the Irati shale performed well in the process, but generation of fines was more prevalent. Oil yields averaged 112% of the modified Fischer assay despite the use of recycled solids to transfer heat to the pyrolyser. Due to the more aliphatic nature of the kerogen, carbon conversion to oil was significantly greater for the Irati shale compared to the Cleveland shale. Otherwise, gasification and combustion kinetics and hydrocarbon gas production were similar for the two shales.

Density gradient centrifugation of − 100 mesh coal: An alternative to using micronized samples for maceral separation

Abstract Using micronized coal for density gradient centrifugation (DGC) may increase maceral separation but the small size of the coal particles also leads to uncertain petrographic and chemical analyses as well as a product size that may not be useful for additional comparative testing. By contrast DGC maceral separations performed on − 100 mesh (150 μm) coal gave excellent, repeatable results with concentrations usually over 95% and a product size which could be more easily utilized for further tests.