Rice hulls are a relatively high‐volume, low‐cost by‐product commodity which contains the two basic components needed to produce silicon: silica and carbon. Impurity analyses have indicated that rice hulls from various sources are compositionally similar and that they have low concentrations (10–20 ppmw) of aluminum and iron, the major impurities in conventional raw materials used to prepare metallurgical silicon. The levels of the major impurities (Ca, K, Mg, and Mn) in rice hulls can be reduced by about a factor of 100 to around 20 ppmw by hot hydrochloric acid leaching. The doping impurities boron and phosphorus, important in silicon intended for solar cells, were less affected by acid leaching. Their concentrations were found to be 1 and 40 ppmw, respectively, in leached hulls. Coking of unpurified rice hulls produced a material with a C:SiO2 ratio of about 4:1. An increase in concentrations of some impurities was noted since coking results in about a 67% loss in sample weight. The coked hulls were extruded with sucrose as a binder to produce 5 mm diam pellets with an average bulk density of about 800 g/l. The pellets gave favorable changes in bulk density and compression strength with increasing percentage sucrose. The abrasiveness of silica caused die wear in the extruder, resulting in roughly a doubling of the original concentration of iron in the coked hulls. Coked rice hull pellets showed excellent reactivity for producing silicon. Laboratory tests employing the reaction of silicon monoxide with carbon in the pellet showed very high reactivities for both purified and unpurified materials. A test in a small arc furnace of unpurified material showed energy consumption per unit weight of silicon to be about 15%–30% lower than normal. Unpurified rice hulls were used for these tests. Although the silicon produced in the arc furnace test was contaminated, estimates of silicon purity attainable from coked hulls, unpurified and purified, indicate their potential as raw materials for the production of MG‐Si and solar‐grade silicon.

A sensitive computational method allowed the determination of normalΔnormalHf°298false(SiHCl3,normalgfalse)=−116.9± 0.7 kcal/mol based on various previously reported experimental investigations. For the first time the gaseous compounds SiCl3 and Si2Cl6 were included in a thermodynamic evaluation of the Si‐H‐Cl system. Diagrams relating normalCl/Hfalse(0.01–10false)normalto Si/normalCl over the temperature range of 400°–1700°K indicate the equilibrium state of the system with respect to the corresponding increase or decrease of silicon in the gaseous phase.

Die Partialdrücke gasförmiger Spezies, die sich im Gleichgewicht mit festem Si im System Si‐H‐Cl befinden, werden als Funktion der Temperatur bei verschiedenen Cl/H‐Verhältnissen und Gesamtdrücken behandelt.

We investigated the accuracy of surface seismic attributes in predicting fracture density variations within the Nordegg Formation in west central Alberta. We know from core, drill samples, well-log, and drilling data that the Nordegg zone is fractured to some degree. These fractures are of interest because the reservoir has very low permeability, and therefore natural fractures may materially affect well performance. 3D surface seismic techniques such as amplitude variation with azimuth or azimuthal AVO (AVAz), variation of velocity with azimuth (VVAz), curvature, and coherence techniques are all tools that have been used to predict fractures in a qualitative fashion. In this study, we wanted to understand how well these attributes predicted the reservoir quality in a quantitative fashion. Previous quantitative studies have used image log orientation data or estimated ultimate recoveries (EUR) in vertical wells as validation data. The conclusiveness of these studies has been subject to several problems: firstly, the limited sample statistics provided by vertical wells applied to the validation of lateral variations, and secondly by the potential nonuniqueness of the EUR to fracture density relationship.