T he three-phase system gas/liquid/fi bre suspension is of great importance in many industrial systems, particularly in the manufacture of pulp. Both separating a gas phase from a fi bre suspension and mixing them are important processes. Pulp fi bre processing is commonly carried out in the medium-consistency (MC) range where the mass concentration of the suspension is between 0.03 and 0.15. MC technology has the potential to decrease not only water and energy consumption but also equipment dimensions. This is of particular importance in connection with the closing of mills. The disadvantages are associated with the more diffi cult processing of the fi bre suspension in operations such as screening, pumping, washing and mixing.The accumulation of gas in centrifugal pumps was one of the fi rst problems encountered when MC technology was introduced (Gullichsen and Härkönen, 1981). Centrifugal forces in the pumps caused an effi cient phase separation and accumulated gas around the pumping wheel prevented further operation. The problem was solved early with vacuum pumps removing excess air from the centre of the pump. Flotation de-inking of wastepaper involves the use of air bubbles to remove hydrophobic particles from wastepaper slurries. Ideally, a homogeneous system would provide more effi cient fl otation but bubble sizes and rise velocities are also very important. Radiographic images reveal that gas fl ow characteristics are substantially altered in the presence of fi bres (Heindel and Monefeldt, 1998).In pulp bleaching operations, gaseous reagents are often mixed into pulp suspensions. The introduction of ozone bleaching in particular has, however, caused complications. The reaction is extremely fast, which makes good gas dispersion essential. Poor dispersion leads to low selectivity, producing unevenly bleached fi bres and degraded fi bres. Byrd et al. (1992) review the literature of ozone bleaching and delignifi cation. When gases are mixed into pulp suspensions, it is important to achieve good mixing over the macro-scale, fi bre-scale and microscale. This ensures the uniform distribution of reagents throughout the suspension and leads to uniform bleaching. Bennington (1993) was the fi rst to make a thorough investigation of the mixing of gases into MC pulp suspensions. Using a high-speed video system, he identifi ed six different fl ow regimes, which were correlated to the power input, pulp consistency and volume fraction of the gas phase. Most of these regimes are less turbulent than is the case in this work. As far as is known, however, no detailed fl ow characterization has been performed on this three-phase fl ow system. Detailed fl ow measurements on a turbulent fi bre suspension (without gas) by Laser Doppler Anemometry (LDA) were reported in earlier work by Andersson and Rasmuson (2000). The measurements were performed on a refractive-index matched glass-fi bre suspension in the 3-20% wt. range. It was found that the liquid fl ow of such suspensions underwent two transitions: the Detailed continuous...

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A new method has been developed for direct analysis of volatile polar trace compounds in aqueous samples by gas chromatography. Water samples are injected onto a short packed precolumn containing anhydrous lithium chloride. A capillary column is coupled in series with the prefractionation column for final separation of the analytes. The enrichment principle of the salt precolumn is reverse to the principles employed in conventional methods such as SPE or SPME in which a sorbent or adsorbent is utilized to trap or concentrate the analytes. Such methods are not efficient for highly polar compounds. In the LiCl precolumn concept, the water matrix is strongly retained on the hygroscopic salt, whereas polar as well as nonpolar volatile organic compounds show very low retention and are eluted ahead of the water. After transfer of the analytes to the capillary column, the retained bulk water is removed by backflushing the precolumn at elevated temperature. For direct injections of 120 microL of aqueous samples, the combined time for injection and preseparation is only 3.5 min. With this procedure, direct repetitive automated analyses of highly volatile polar compounds such as methanol or tetrahydrofuran can be performed, and a limit of quantification in the low parts-per-billion region utilizing a flame ionization detector is demonstrated.

In 2006, a new species of non-calcified dasycladalean alga, Chaetocladus gracilis, from the upper Silurian of Skåne (Scania), southernmost Sweden, was erected. The original description was based on a single incomplete fossil recovered from the abandoned limestone quarry at Bjärsjölagård, a classic geologic locality in Scania. Here we present four additional and, importantly, more complete specimens from this same site and type stratum. This new material largely corroborates the general anatomical features of C. gracilis, but also adds some intricate details, most notably with regards to the external sheet-like phytoleim and organisation of the laterals. Elemental mapping confirmed an expected carbonaceous composition of the fossils, which are embedded in a calcareous mudstone. These additional fossils show that the originally described specimen was not a singular occurrence at this locality. Based on the state of preservation of our algal fossils, we note that the mudstone facies of the Ludlow Bjärsjölagård Limestone Member of the Klinta Formation (Öved-Ramsåsa Group), from which all C. gracilis have been recovered, share characteristics with deposits typically referred to as "algal-Lagerstätten".