Reducing CO2 emissions from oil shale semicoke smoldering combustion by varying the carbonate and fixed carbon contents

One technique used to recover oil from ground oil shale, or to burn oil shale semicoke, consists of propagating a smoldering front through a packed bed. One drawback of this technique is that the mineral structure of the shale is decarbonated due to the high temperature of the front. This phenomenon causes 70% of the CO₂ emissions released during such processes. The remaining 30% result from the fixed carbon oxidation. With the aim of decreasing the front temperature and thus avoiding decarbonation at the front passage, the impact of two parameters was experimentally tested in this work: first, increasing the amount of carbonates, as they may play the role of a heat sink, and second, decreasing the amount of fixed carbon in the medium. It is shown that increasing the amount of carbonates can only decrease the front temperature to 800 °C but not lower, which is still too high to avoid decarbonation. On the other hand, the front temperature can be decreased enough for decarbonation to be almost completely avoided by reducing the amount of fixed carbon. At the low temperatures reached, almost all the fixed carbon is oxidized, but not all the oxygen transported in the air is consumed by the chemical front. The velocity of the front is consequently decreased.     

Resonant Oscillations in Multiple-Filled Skutterudites

Partially filled skutterudites were investigated by ultrafast spectroscopy using a femtosecond laser system, which excites resonant oscillations due to the host–guest interactions. To investigate the effect of individual guest elements on phonon-mediated thermal transport, four skutterudite samples were studied: three samples partially filled with Ba, Yb, and La, respectively, and a fourth with a combination of these three elements. The spectrum of the oscillations in the transient thermoreflectance signal was analyzed by Fourier transformation. Comparison with the Raman spectra shows that different guest elements cause resonant oscillations with different frequencies, which can scatter phonons in different spectrum spans. This further demonstrates that multiple guest elements can scatter a wider spectrum of phonons than a single guest element at similar filling fractions, which results in lower lattice thermal conductivity (κ _L) in skutterudites. These findings are consistent with thermal conductivity measurements reported previously.     

Statistical profiles of highly-rated learning objects

The continuously growth of learning resources available in on-line repositories has raised the concern for the development of automated methods for quality assessment. The current existence of on-line evaluations in such repositories has opened the possibility of searching for statistical profiles of highly-rated resources that can be used as priori indicators of quality. In this paper, we analyzed 35 metrics in learning objects refereed inside the MERLOT repository and elaborated profiles for these resources regarding the different categories of disciplines and material types available. We found that some of the intrinsic metrics presented significant differences between highly rated and poorly-rated resources and that those differences are dependent on the category of discipline to which the resource belongs and on the type of the resource. Moreover, we found that different profiles should be identified according to the type of rating (peer-review or user) under evaluation. At last, we developed an initial model using linear discriminant analysis to evaluate the strength of relevant metrics when performing an automated quality classification task. The initial results of this work are promising and will be used as the foundations for the further development of an automated tool for contextualized quality assessment of learning objects inside repositories.     

High-density automotive hydrogen storage with cryogenic capable pressure vessels

LLNL is developing cryogenic capable pressure vessels with thermal endurance 5–10 times greater than conventional liquid hydrogen (LH₂) tanks that can eliminate evaporative losses in routine usage of (L)H₂ automobiles. In a joint effort BMW is working on a proof of concept for a first automotive cryo-compressed hydrogen storage system that can fulfill automotive requirements on system performance, life cycle, safety and cost. Cryogenic pressure vessels can be fueled with ambient temperature compressed gaseous hydrogen (CGH₂), LH₂ or cryogenic hydrogen at elevated supercritical pressure (cryo-compressed hydrogen, CcH₂). When filled with LH₂ or CcH₂, these vessels contain 2–3 times more fuel than conventional ambient temperature compressed H₂ vessels. LLNL has demonstrated fueling with LH₂ onboard two vehicles. The generation 2 vessel, installed onboard an H₂-powered Toyota Prius and fueled with LH₂ demonstrated the longest unrefueled driving distance and the longest cryogenic H₂ hold time without evaporative losses. A third generation vessel will be installed, reducing weight and volume by minimizing insulation thickness while still providing acceptable thermal endurance. Based on its long experience with cryogenic hydrogen storage, BMW has developed its cryo-compressed hydrogen storage concept, which is now undergoing a thorough system and component validation to prove compliance with automotive requirements before it can be demonstrated in a BMW test vehicle.     

Sensory acceptability of slow fermented sausages based on fat content and ripening time

Low fat dry fermented sausages were manufactured using controlled ripening conditions and a slow fermented process. The effect of fat content and ripening time on the chemical, colour, texture parameters and sensory acceptability was studied. The fat reduction in slow fermented sausages produced an increase in the pH decline during the first stage of the process that was favoured by the higher water content of the low fat sausages. Fat reduction did not affect the external appearance and there was an absence of defects but lower fat content resulted in lower sausage lightness. The sausage texture in low fat sausages caused an increase in chewiness and at longer ripening times, an increase in hardness. The sensory acceptability of the fermented sausages analyzed by internal preference mapping depended on the different preference patterns of consumers. A group of consumers preferred sausages with high and medium fat content and high ripening time. The second group of consumers preferred sausages with low ripening time regardless of fat content except for the appearance, for which these consumers preferred sausages of high ripening time. Finally, the limit to produce high acceptability low fat fermented sausages was 16% fat content in the raw mixture that is half the usual content of dry fermented sausages.     

Subsolidus Phase Relations in the Pseudoternary System SrO·6M2O3 (M = Fe, Cr, Al) in Air

Crystalline powder samples belonging to the pseudoternary system SrO·6M₂O₃ (M = Fe, Al, Cr) were synthesized in air. The limit of the magnetoplumbite-type (M-type) phase solid solution is governed by the presence of Cr³⁺ in the structure and is accompanied by the formation of a chromate and a sesquioxide. The extension of the solid solution in the Cr-containing pseudobinaries depends to a large extent on the crystallographic site preference of the host cation. The extension of the M-type solid solution is also narrowed at a lower temperature.     

A time temperature integrator for particulated foods: thermal process evaluation

 A time temperature integrator (TTI) was developed by immobilizing Bacillus stearothermophilus spores in a cylindrical particle consisting of an alginate-starch-mushroom purée. The particle showed homogeneous spore distribution, and when heated over a temperature range of 121 – 130° C negligible spore leakage was observed after the thermal process. The experimental data on spore survivor levels obtained for each temperature-time combination were compared with theoretical predictions using a mathematical model. The results showed a good correlation between the experimental and theoretical data. All these results provide evidence that this artificial particle could be a very reliable TTI for monitoring the thermal impact on micro-organisms during validating sterilization processes in continuous aseptic systems. Received: 25 February 1997     

Photocatalytic oxidation on nanostructured chalcogenide modified titanium dioxide

Surface mesoscopic titanium dioxide (P25) films deposited onto conducting glass plates (SnO₂:F) were modified by colloidal Ru_xSe_y nanoparticles (2 nm diameter). A decrease of the photocurrent was found upon modification of TiO₂ films. However, interfacial electron transfer kinetics to oxygen was favored. The increase of the catalyst surface concentration onto TiO₂, shifts the onset of the photocurrent under UV-illumination, to 0.6 V/RHE in presence of oxygen dissolved in the electrolyte. Concomitant to this, the cathodic current becomes important and shifts to more positive potentials. This phenomenon allows the system to work catalytically under open circuit conditions. On non-modified TiO₂, the application of a 0.3 V/RHE potential leads to an enhancement of the photooxidation of formic acid. Photocurrent images revealed a non-homogeneous distribution of the catalyst on the titanium dioxide films.