Aurora M. Rubel

The effect of low-concentration SO2 on the adsorption of NO from gas over activated carbon

The effect of low-concentration SO2 on the adsorption of NO over activated carbon was studied using adsorption-desorption profiles obtained during thermal analysis-mass spectrometry. Using three different gas mixtures and adsorption temperatures between 293 and 413 K with NO and SO2 as the reactants, it was determined that NO2 and SO2 were the primary adsorbed species. The uptake of NO2 decreased with increasing temperature, whereas the uptake of SO2 was independent of temperature. Except at the highest adsorption temperatures, the amount of NO2 adsorbed was greater than that of SO2 adsorbed. The presence of SO2 inhibited adsorption of NO2, but the co-adsorption of NO2 promoted the adsorption of SO2. These data point to the possibility that the SO2 binding sites on the carbon are associated with the reaction NO + 12 O2 → NO2, and to the different adsorption mechanisms which control NO2 and SO2 uptake.

CH4 storage on compressed carbons

Abstract Compressibility indices and CH 4 uptake capacities were determined for three commercially produced carbons, using a specially designed cell, developed for a high pressure thermal gravimetric analyzer. The cell was used during CH 4 uptake measurements on non-compacted and compacted carbon materials, while maintaining a constant sample volume. Compressibility, piece density, and CH 4 uptake capacities were measured for carbons having different particle sizes, after physical blending, and before and after coke deposition. Pore size distributions and pore volumes was obtained. Compaction of the activated carbons and a graphite powder increased the CH 4 uptake per unit volume of the material beyond that expected from densification. The data suggested that compaction and physical blending provides additional CH 4 adsorption sites in inter-particle voids.

Comments on the Modified Fischer Assay of Eastern oil shales of Kentucky

Abstract The Modified Fischer Assay is the accepted method for evaluating the potential liquid fuel yield of an oil shale. For a given shale, percent of Fischer Assay oil yield has become the standard used for judging technologies. The method has been developed for and is well understood when applied to oil shales in the western United States. However, the assay can be successfully applied to eastern United States oil shales only if care is taken in several areas that prove less important for its successful application to western shales. In particular, standardized sample preparation and handling with minimum air exposure of pulverized shale is required; a well-controlled and reproducible heating profile during retorting must be employed; and consistently effective liquid product collection must be accomplished. These considerations have a major influence on assay accuracy. Only with care in these areas, can Modified Fischer Assays suitable for eastern shale resource evaluations and technology comparisons be obtained.

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.

Structural and surface characterization of ultrafine iron carbide particles generated by laser pyrolysis. I. High temperature He treatment

Three samples of passivated ultrafine iron carbide particles, synthesized by laser induced pyrolysis of gaseous precursors, were examined by x‐ray diffraction, x‐ray photoelectron spectroscopy, and thermogravimetry/mass spectroscopy at temperatures as high as 600 °C under a He atmosphere. The approximate 6–7 nm diam particles began to sinter at temperatures between 300 and 400 °C and formed a complex mixture of carbide, oxide and metallic phases. Preservation of the carbide structure on heating was dependent on the purity of the carbide, and the concentration of oxygen and carbon in the particles. A topotactic transformation from Fe7C3 to Fe0.98O was observed and is discussed relative to the as‐synthesized/passivated particles composition and structure. This topotaxy leads to the selective formation of γ‐Fe2O3 from specific ultrafine particle carbides.

EFFECT OF PROCESS SOLIDS ON SECONDARY REACTIONS DURING OIL SHALE RETORTING

Abstract The effect of solids processing, oil vapour-solids interactions and contact time on coke formation from oils produced during Eastern US oil shale pyrolysis was investigated. Both long and short vapour contact time reactors were used to study the coking reactivity of sand, processed shales and clay minerals typically associated with Eastern US oil shales. BET nitrogen surface area and reflected light microscopy were used to correlate physical properties of the solids with carbon deposition. Combusted shales were more reactive coking substates than pyrolysed or gasified shales. Physical measurements indicated that macropores and fractures (not measured by BET) were important in coke formation. Steam treatment of oxidized shale decreased coking without changing measured physical properties. This is possible evidence for chemical alteration of the mineral matrix. Combustion temperature (773 versus 1098 K) did not affect the reactivity of oxidized shales. Therefore, high coking cannot be attributed to temperature-induced activation of the mineral matrix. Coking on clay minerals correlated to nitrogen BET surface area. Process-induced macroporosity, which allowed access to an active mineral matrix, was postulated as important in coke deposition.

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.

A study of the suitability of the KENTORT II eastern shale oil for asphalt paving applications

Abstract The uncertain future of petroleum reserves has fuelled the search for alternative resources. A feasibility study was conducted to determine potential paving applications of the oil extracted from eastern shale by the KENTORT II process. The eastern shale oil (ESO) in this study was separated into two drastically different viscosity portions, designated as ‘hard’ and ‘soft’ ESO. It was hypothesized that the ‘hard’ portion might enhance the asphalt performance by increasing the stiffness. It was discovered that the ‘hard’ ESO modified asphalt properties deteriorate significantly with time. On the other hand, the ‘soft’ ESO was found to exhibit desirable properties in an asphalt recycling application. Further studies are recommended to fully characterize the binder and mixture properties of ESO modified/rejuvenated asphalts.

Comparison of oils produced from Kentucky oil shales by fluid bed and Fischer assay retorting

Physical properties and chemical composition of oils produced from a master sample of the Ohio Shale by bench scale fluid bed and Fischer Assay retorting are compared. The fluid bed oil was found to have a higher nitrogen content, lower H/C ratio, more heteroaromatic and heavy hydrocarbons, higher alkene/alkane ratios, a higher naphthalene/(C/sub 11/ + C/sub 12/) ratio and a higher aromatic carbon content than the Fischer Assay oil. Since vapor phase cracking is the major source of oil loss during fluid bed retorting with coking being near zero, these results are in agreement with correlations developed for western U.S. shales. Additionally, there is evidence to suggest that under fluid bed conditions, raw shale aromatic carbon is converted to oil.

Fluidized bed gasification characteristics of Devonian oil shale char

A Kentucky oil shale char was gasified in a fluid bed reactor. The effects of mean solid residence time (MSRT), bed temperature, and steam and CO2 partial pressure were studied. Carbon reactions during gasification were found to be dependent on all three parameters. The steam/char reaction was the dominant primary gasification reaction. The CO2/char reaction did not proceed significantly under the conditions studied and COCO2 ratio was dependent on the steam partial pressure. Sulphur removal was less dependent on temperature and steam partial pressure and was essentially complete by 1800 s MSRT. Nearly complete sulphur conversion was the result of both thermal decomposition and steam reaction with pyrrhotite. Conversions of 80–85% sulphur and 70–75% carbon (raw shale basis) were obtained for combined pyrolysis/gasification. The implications of the results for the development of a retorting process for Devonian shales are discussed.