Stirrer blade

For discharge of the cake, a discharge door is provided at the edge and the cake is moved by the rotor toward the door, the stirrer blades gradually being lowered onto the surface so that a small depth of soHds is scraped away. Alternatively, the cake may be reslurried and pumped away. 

Purely aqueous polymerization systems give copolymers that are not wetted by the reaction medium. The products agglomerate and plug valves, nozzles, and tubing, and adhere to stirrer blades, thermocouples, or reactor walls. These problems do not occur in organic media or mixtures of these with water. 

It is known from many publications that aeration reduces the Ne number as a result of the formation of gas cavties behind the stirrer blades. The measured values can be described with sufficient accuracy using the following graphic correlation [23] ... 

Probe fouling was minimized when the probe was placed properly in the reactor relative to the liquid surface and to the mechanical stirrer. The ideal spot, although not explicitly stated, would presumably be deep enough into the emulsion to see a representative bulk sample and to avoid any dead unstirred spots, but far enough from the stirrer blade to avoid impact. 

The.Crvstallia Cell Where All The Experiments were Perfarmed. This was a 1 liter pyiex vessel covered by a 1 cm thick plexiglass cover. Holes in the plexiglass cover permitted the introduction of a Beckman thermometer and a specially constructed stirrer capable of accommodating two ice seed crystals on its blades. These seed crystals were attached to the tips of the stirrer blades by a slow freezing process of water in contact with the tips of the stirrer. 

The use of a monolithic stirred reactor for carrying out enzyme-catalyzed reactions is presented. Enzyme-loaded monoliths were employed as stirrer blades. The ceramic monoliths were functionalized with conventional carrier materials carbon, chitosan, and polyethylenimine (PEI). The different nature of the carriers with respect to porosity and surface chemistry allows tuning of the support for different enzymes and for use under specific conditions. The model reactions performed in this study demonstrate the benefits of tuning the carrier material to both enzyme and reaction conditions. This is a must to successfully intensify biocatalytic processes. The results show that the monolithic stirrer reactor can be effectively employed in both mass transfer limited and kinetically limited regimes. 

The monolithic stirrer reactor (MSR, Figure 2), in which monoliths are used as stirrer blades, is a new reactor type for heterogeneously catalyzed liquid and gas-liquid reactions (6). This reactor is thought to be especially useful in the production of fine chemicals and in biochemistry and biotechnology. In this work, we use cordierite monoliths as stirrer blades for enzyme-catalyzed reactions. Conventional enzyme carriers, including chitosan, polyethylenimine and different are used to functionalize the monoliths. Lipase was... 

Place 376 ml of deionized water into a 1-liter resin kettle equipped with a sealed stirrer and appropriate stirring motor (see also Note 2 of Experiment 2), reflux condenser, thermometer, and nitrogen inlet tube reaching down to just above the stirrer blade. 

The stirrer should be provided with a motor which will not ignite the hydrogen. Either an induction motor or an air stirrer may be used. The stirrer blades may be made of glass, Monel, or stainless steel. 

A 5-qt. enamel pail or bain-marie jar is fitted with two mechanical stirrers (Note 1) placed off center, a thermometer for reading low temperatures, and a dropping funnel, the lower end of which is placed just over the vortex created by one of the stirrer blades, so that each drop of added liquid is immediately mixed with and diluted by the chilled reaction mixture. 

Loiseau et al. (1977) found that their data for nonfoaming systems agreed well with Eq. (3.3). Calderbank (1958), Hassan and Robinson (1977), and Luong and Volesky (1979) have also proposed correlations for power consumption in gas-liquid systems. Nagata (1975) suggested that power consumption for agitated slurries can be reasonably predicted from these correlations by the correction factor psi/pL, where psl is the density of the slurry. Power consumption for a gas-liquid-solid system has also been studied by Wiedmann et al. (1980). They examined the influence of gas velocity, solid loading, type of stirrer, and position of the stirrer blades on power consumption plots of power numbers vs. Reynolds numbers for propeller and turbine type impellers proposed by them are shown in Fig. 13. 

Stainless steel stirrer. Propeller type, with four fixed stirrer blades set at an angle of 45°. Particular attention should be given to the construction of the stirrer its dimensions should conform to those shown in Fig. 1. 

Fill the beaker with 1000 ml of standard hard water at 30°C + 2°C. The stirrer should be centrally located in the beaker and positioned in such a way that the lower edges of the stirrer blades are 60mm above the base of the beaker. The pitch of the stirrer blades and the direction of rotation are such that the propeller pushes the water upwards. Add the tablet to the water without stirring. Wait for 1 minute. Switch on the stirrer with the speed set to about 300 rev/min... 

Large eddies with frequencies of 0 < / > with = n x z - frequency of the stirrer blades, n - stirrer speed, z - number of blades). They account for only a small part of the total energy. The relative spectral dissipation energy E f) increases with f or remains approximately constant, where E (/) is given by the expression ... 

From the energy spectra it follows that the turbulence in particular in the proximity of the stirrer blade is markedly non-isotropic and non-homogeneous. The turbulence spectra for different values of the radial coordinates R = (2r-d)/d... 

The flow round the stirrer blades interacts with the stationary baffles and produces a complex, circulating turbulent flow. When gas is sparged in a tank it collects in low pressure zones behind the stirrer blades forming gas cavities, which considerably influence the flow and the turbulence in the vessel. 

The turbulent gas/liquid flow in baffled tanks with turbine stirrer can be predicted. A mathematical model has been developed for turbulent, dispersed G/L flow. The time-averaged two phase momentum equations were solved by using a finite volume algorithm. The turbulent stresses were simulated with a K-fi-model. The distribution of gas around the stirrer blades is predicted for the first time. This model also enables an a priori prediction of the drop in the power dissipated by the stirrer in the presence of gas. Predicted flow characteristics for the gas/liquid dispersion show good agreement with the experimental data. 

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