Gregory J. Duffy

A four-lump kinetic model for the cracking/coking of recycled heavy oil☆

Abstract In recycled solids processes, shale oil undergoes secondary cracking/coking reactions on the surface of the recycle solids used as the heat carrier. Heavy oil recycle uses these secondary reactions to advantage to convert the heavy oil fraction produced during primary pyrolysis reactions to lighter, more desirable products, thereby reducing the overall severity of hydrotreating which would otherwise be required to upgrade this fraction to a refinery grade feedstock. A four-lump kinetic model has been developed to describe the rate of production of the lighter condensable oil, as well as the coke and non-condensable gases which are also formed. This kinetic model can be used to predict yields from the cracking/coking of heavy oil in any type of reactor.

Coking reactivities of Australian shale oils

Abstract Coking of oil on recycle solids represents the most significant cause of loss of yield during the processing of Australian oil shales. The kinetics of coke formation were measured for eight Australian shale oils on their respective shale ashes. The reactivity of Stuart ashes was found to decrease as the temperature under which they were produced increased. Preparation in a steam atmosphere resulted in an even greater reduction in their reactivity. Ashes prepared in a fluidized bed combustor were found to be less reactive than those prepared in a muffle furnace at the same temperature. A strong correlation was found between the reactivity of these ashes and their surface area. There appeared to be no difference in the coking reactivity of freshly prepared ashes and those stored for 15 days. The coking kinetics of oil fractions with different boiling point ranges on Stuart shale ash were determined. The highest rate of coking was found in oil fractions with high boiling point components. A strong correlation was found between oil coking reactivities and their nitrogen contents.

Supercritical fluid extraction of petroleum hydrocarbons from contaminated soils

Abstract Quantitative recovery of petroleum hydrocarbons from a contaminated soil by supercritical fluid extraction depends on the three-way interactions between the soil, the analytes, and the supercritical fluid. This discussion examines some of the important parameters which can influence the efficiency of supercritical fluid extraction of petroleum hydrocarbon mixtures from contaminated soils.

Mechanisms of thermal alteration of shale oils

Abstract Evidence is presented for three distinct causes of shale oil alteration, when in contact with hot shale solids. Thermal cracking, which is independent of the solid material, generates additional alk-1-enes. Active acidic sites in fully combusted spent shale are responsible for coke formation, dealkylation of aromatics, and isomerization of alkenes. These sites are deactivated by carbon coverage, for example in retorted shale. In addition, catalytic dehydrogenation of aliphatics, to give primarily ortho-disubstituted benzenes, is operative on both carbon covered and fully combusted shales.

CSIRO's Advanced Power Generation Technology Using Solar Thermal — Fossil Energy Hybrid Systems

Publisher Summary CSIRO has completed a major project to demonstrate a solar thermal-fossil energy hybrid concept for generating solar-enriched fuels and electricity with potential for high thermal efficiencies and for greatly reduced CO2 emissions. This concept features: reforming of CH4-containing gases using concentrated solar energy to generate a mixture of CO and H2 suitable for use as a fuel, metallurgical reductant or as a chemical feed stock. Another feature is further conversion of the gas to H2 and CO2 followed by recovery of CO2 in a concentrated form, as required for any subsequent CO2 disposal or utilization scheme; and further purification of gas to produce H2 for use in advanced electricity generation systems such as fuel cells and turbines. Integrated mode of operation was conducted producing PEMFC quality H2. With much improved dish mirrors, tracking algorithm, and an energy efficient reformer, solar steam reforming at 136% design feed was achieved. This indicates strong potential for further improvements resulting in commercial application of the proposed Solar Thermal Fossil Energy Hybrid System.

Comparison between model predictions and performance of process development units for oil shale processing

Abstract As part of an on-going investigation into the processing characteristics of Australian tertiary oil shales, detailed reactor models have been developed to describe the retorting of raw shale and the combustion of spent shales in fluidized beds. These models take into account the dynamics of fluidization and the relevant reaction kinetics, and allow for the mixing of solid streams and the significant increase in the volumetric flow of gas which can occur due to the evolution of product vapours and gases during the retorting of oil shales. The models are being used not only in process variable studies of full scale plants, but also to test the generality of kinetic data obtained from other studies within the oil shale programme. The reactions considered in the retort model include the pyrolysis of oil shale kerogen, and the coking and thermal cracking of oil vapour, while for the combustor, the combustion of residual char is considered. This paper reports how experimental work performed in 150 mm diameter process development units for pyrolysis and combustion is being used to assess the reliability of these kinetic data for scale-up purposes.

Comparative pyrolysis characteristics of Alpha torbanites and tertiary oil shales

Abstract Comparative pyrolysis data have been determined for samples of Alpha torbanite and its associated cannel coal using the apparatus and techniques previously applied to Tertiary oil shales. Modified Fischer assays gave C5 + oil yields of 61.5 ± 0.2% for the torbanite, almost four times the maximum yield measured with Tertiary oil shales. Oil yields of 13.4 ± 0.2% for the cannel coal were comparable with the higher grade Tertiary deposits. In terms of elemental analysis, the most significant difference in composition of the oils was the high sulphur content of the cannel coal oil, which reflected the high sulphur content of this shale. Isothermal pyrolysis kinetic studies indicated that the torbanite was less reactive than Tertiary oil shales, while the cannel coal was comparable in reactivity with Stuart oil shales. However the differences in reactivity became significantly less as pyrolysis temperature approached 500 °C.

Coking and cracking behaviour of heavy oil derived from the Stuart deposit

Abstract The coking and cracking behaviour of a heavy oil fraction derived from Stuart shale oil was investigated in a moving packed-bed reactor. Experiments were performed to evaluate the conversion of heavy oil into lower-boiling products, coke and gases when contacted with fully burnt shale ash and sand. The oil products were characterized by elemental composition, boiling point distribution and n.m.r. spectrometry. The experimental data show wide variations in the stoichiometry, depending on the relative contributions of thermal cracking and coking/catalytic cracking reactions. N.m.r. analyses of the oil products provide insight into the mechanisms of heavy oil coking and cracking. The 1-ene:internal-ene ratio of the product oil provides a reliable indicator of the relative importance of these two reactions.