Aerated bunker discharge of fine dilating powders

The discharge rate of coarse powders (mean particle size 500 ¿m) from bunkers without aeration can be described by both empirical relations and theoretical models. In the case of small particles the discharge rate is largely overestimated. As the powder dilates during flow a negative pressure gradient develops near the hopper outlet, inducing an air flow into the hopper. This extra drag force decreases the discharge rate for fine particles. Aeration of the hopper through a porous cone section will create an opposite pressure gradient, and thereby increase the discharge rate. The aim of this investigation was to incorporate the dilation in an ad hoc way into the model of Altiner in order to improve its predictive power. To test the modified model we carried out experiments with a fluid catalytic cracking powder to study its discharge as a function of aeration. As the improved model needs a dilation parameter as input, the local bulk density was measured during flow at the outlet and at the bin/hopper junction using gamma-ray absorption. At the bin/hopper junction the bulk density was found to be independent of the discharge rate and equal to the bulk density at minimum fluidisation. At the outlet the bulk density goes through a maximum when the amount of aeration gas is increased. Without aeration gas a large dilation, i.e. a 15¿35% lower bulk density, was observed. With these data the model predictions improved from 600% overestimation error to 25¿90% underestimation for pure gravity discharge, and from 100% to 0¿20% error for aerated discharge. However, the bulk density at the outlet cannot be predicted from the powder compressibility, as it seems to depend on dilation at fluidisation

Cluster of Botulism among dutch tourists in Turkey, june 2008

In June 2008, three Dutch tourists participating in a mini-cruise in Turkey needed urgent repatriation for antitoxin treatment because of symptoms of botulism. Because there was a shortage of antitoxin in the Netherlands, an emergency delivery was requested from the manufacturer in Germany. An outbreak investigation was initiated into all nine cruise members, eight of whom developed symptoms. C. botulinum type B was isolated in stool culture from four of them. No other patients were notified locally. Food histories revealed locally purchased unprocessed black olives, consumed on board of the ship, as most likely source, but no leftovers were available for investigation. C. botulinum type D was detected in locally purchased canned peas, and whilst type D is not known to be a cause of human intoxication, its presence in a canned food product indicates an inadequate preserving process. With increasing tourism to areas where food-borne botulism is reported regularly special requests for botulism antitoxin may become necessary. Preparing an inventory of available reserve stock in Europe would appear to be a necessary and valuable undertaking

Crosslinked agarose encapsulated sorbents resistant to steam sterilization. Preparation and mechanical properties

The application of agarose in hemoperfusion is hampered by the lack of a suitable sterilization method. A technique has been developed for the crosslinking of agarose encapsulated sorbents by the reaction with 1,3-dichloro-2-propanol (DCP) under strong alkaline conditions. A twofold molar excess of DCP with respect to agarose and an equimolar amount of sodium hydroxide at a concentration of 0.3 mol/L with a reaction time of 1-4 h at 50°C are found to be the optimal conditions. The compressive strength of crosslinked beads is increased by a factor of 4. Agarose capsules are found to degrade by the influence of Y radiation, but are resistant to steam sterilization at 134°C during at least 30 min when crosslinked

CAD implementation of design rules for aluminium extrusion dies

Aluminium extrusion is an industrial forming process that is used to produce long profiles of a constant cross-section. This cross-section is shaped by the opening in a steel tool known as the die. The understanding of the mechanics of the aluminium extrusion process is still limited. The flow of aluminium within the die is governed by tribomechanical and rate- and temperature-dependent effects that have not yet been fully mathematically modelled. As a result, it is difficult to design the die geometry in such a way that the aluminium profile complies with high customer demands regarding dimensional accuracy and surface quality. Die design has to a large extent been empirically based. This, along with a low level of automation, causes a large variation in the performance of dies. This often necessitates corrections to the die and results in a high percentage of scrap production. This dissertation is a continuation of a research project that has existed since 1991. In cooperation with the aluminium extrusion company Boalgroup, researchers at the University of Twente have worked to gain more insight into the extrusion process. With the help of finite element simulations this has led to the formulation of design rules and approaches that are based on a more fundamental understanding of the process than the existing empirical knowledge. A design method was devised that balances the exit velocity of flat dies by using a combination of variable sink-in and bearing geometry. This leads to die designs that exhibit a more stable and predictable flow balancing behaviour than traditional designs based on length variations of parallel bearings alone. In addition, a formula is given that estimates the pressure acting on the die, so that the calculation time of finite element analysis of the die deflection is drastically reduced. Along with making a contribution to the developments mentioned above, the work presented in this thesis focuses on the implementation of these design rules and approaches into CAD tools. The provided automation of these design tasks significantly accelerates the design process and increases the consistency of the results, without removing the control of the human designer. By taking constraints of the manufacturing process into account while generating the geometry, the risk that the die manufacturer has to make unexpected changes to the die design is reduced. The reduction of design time that was achieved has enabled Boalgroup to greatly increase the number of in-house die designs. Since the majority of these new designs is showing a significant performance increase, the company’s overall productivity has increased steadily, helping them to deal with the ever rising labour and energy costs

Farm mechanization and soil structure.

Pore space was 0.25-1.5 vol. % higher and air content at pF 1.9 was 0.5-1.9 vol. % higher in fine-textured soils on farms using horse-traction only than on farms using tractor-drawn implements only. The differences were greater in wet years when the general level of soil structure was low than in dry years. (Abstract retrieved from CAB Abstracts by CABI’s permission