Impact of operations at low anode-cathode distance on energy consumption and greenhouse gas emissions at Aluminerie Alouette

The energy consumption for aluminum production by the Hall-Héroult process has been significantly improved during the last few decades. This has been achieved mainly as a result of improved cell design and suitable process control strategies that have allowed higher cell currents and smaller anode-cathode distance (ACD). Without taking suitable corrective actions, operations at lower ACD conditions can negatively impact aluminum re-oxidation, by-pass current, alumina dissolution and anode effect rates. Superior operational practices are therefore required to maintain acceptably low instability levels along with lower specific energy consumption. This paper discusses anode effect fundamentals and greenhouse gas emissions in relation with industrial cells operating at low ACD at the Aluminerie Alouette plant in Quebec.     

An experimental investigation of effusivity as an indicator of powder blend uniformity

Effusivity has recently been proposed as a process analytical technology (PAT) for monitoring the uniformity of powder blends resulting from pharmaceutical mixing processes. The objective of this work is to gain insight into the accuracy, sensitivity and limitations of effusivity as an indicator of blend uniformity. Two series of experiments were carried out. First, monitoring experiments were used to determine and compare the optimal blending times of a pharmaceutical mixture obtained by three different methods: effusivity, density and UV spectroscopy. A second series of experiments was conducted to quantify the influence of density on effusivity measurements. The potential of effusivity to be used as a tool for assessing blend uniformity is discussed. In particular, the results from these experiments reveal that the accuracy of effusivity in determining optimum blending times depends on the blend physical characteristics and is significantly influenced by density.     

Mesohabitat use by brown trout (Salmo trutta) in a small groundwater‐dominated stream

Groundwater‐dominated streams have particular flow regimes that commonly support populations of trout. Meso‐ and micro‐habitat surveys were carried out on a reach of the river Tern that drains a Triassic sandstone aquifer in the English West Midlands, to investigate brown trout (Salmo trutta) habitat use with varying flows. Mesohabitats were mapped over a range of summer and autumn flows and coupled with direct underwater observation (snorkelling) of fish locations together with point measurements of velocity and depth. The number of habitat types recorded was low and dominated by glides, runs, and backwaters. Brown trout showed a strong association with glides and runs with adults being more associated with runs and parr with glides. General habitat use curves showed brown trout to favour depths between 0.30 and 0.40 m and velocities below 0.40 m s^?1. A clear preference was shown for sand and gravel bed materials. However, the differentiation of hydraulic habitats was weak and there was no trend in mesohabitats or change in trout use of mesohabitats with discharge. The study raises limitations of the mesohabitat survey approach when linking fish ecology, flow and physical habitat in small streams with low flow variability and low habitat diversity. In these situations, other factors (especially cover features) appear to strongly influence brown trout distribution. Copyright © 2010 John Wiley & Sons, Ltd.     

Reconstruction of three-dimensional chemiluminescence images with a maximum entropy deconvolution algorithm

Three-dimensional (3D) images of flame emission are reported using a single direction of optical access. A Cassegrain system was designed with narrow depth of field. Images from this system are dominated by emission from the focused object plane with defocused contributions from out-of-plane structures. Translation of one mirror in the system allows for scanning the object plane through the flame. Images were taken at various depths to create a family of images. Reconstruction of the 3D flame structure was accomplished using a maximum entropy algorithm adapted for use with 3D imaging. Spatial resolution in the direction of imaging is examined using laminar flames with variable offset.