Mixing action

Fluidized-bed reactor systems put other unique stresses on the VPO catalyst system. The mixing action inside the reactor creates an environment that is too harsh for the mechanical strength of a vanadium phosphoms oxide catalyst, and thus requires that the catalyst be attrition resistant (121,140,141). To achieve this goal, vanadium phosphoms oxide is usually spray dried with coUoidal siUca [7631-86-9] or polysiUcic acid [1343-98-2]. Vanadium phosphoms oxide catalysts made with coUoidal sUica are reported to have a loss of selectivity, while no loss in selectivity is reported for catalysts spray dried with polysUicic acid (140). 

High-Intensity Mixer. Mixers such as that shown in Fig. 18-44 combine a high shear zone with a fluidized vortex mixing action. Blades at the bottom of the vessel scoop the batch upward at peripheral speeds of about 40 m/s (130 ft/s). The high shear stress (to 20,000 s" ) and blade impact easily reduce agglomerates and aid intimate dispersion. Since the energy input is high [200 kW/m (about 8 hp/fE)h even powdery material is heated rapidly. 

Amount of conveying and mixing action affected by amount of pitch and type of ribbons mounted on exterior of hollow screws. 

The average composition of the stream leaving a continuous mixer is the same as the average of the added entering streams. Variations in proportions of the entering streams will be damped out by the mixing action of a continuous mixer. These effluent-stream variations will become smaller as average solids residence time is increased and the frequency of the variations increases. 

Axial flow, in which the liquid enters the impeller and discharges along a parallel path to the axis, is shown in Figure 9. The radial and longitudinal components are primarily responsible for the derived mixing action. The tangential component is important when the shaft has a vertical orientation and is positioned near the center of the tank. 

Biogas is produced by the bacteria in the form of small bubbles these float upward through the sludge bed/blanket, providing a good mixing action. When the biogas reaches the top of the reactor, it is collected and used as a fuel. 

Amplify mixing action by effectively increasing the rado of mixer to container diameter. 

Plasticize It is the mixing action to soften a plastic and make it processable usually through the use of heat. 

Clearly recognizable is the big flucmation of the power supply. During the phases in which the power input is high, mixing action takes place together with a remarkable temperamre increase. 

Type of equipment Mixing action Applications Examples... 

In the case of the intermeshing rotor machine the majority of the mixing action takes place between the rotors with the shearing action being created by the rotor design. Unlike the tangential mixers where the rotors revolve at different speeds, the rotors in intermeshing machines run at the same speed. 

The mixing mechanism of this mixer revolves around two axes. The mixing blades revolve around a common axis and also their own axis of rotation. This mixing action is particularly effective especially for less viscous solutions. 

Phenylephrine and phenylpropanolamine, which are sympathomimetics of mixed action, are also used in medicine for reducing edema in the mucous membranes. 

Practically every examined substance of mixed action has indirect action (such as that of tyramine), in addition to a direct action (activation of adrenoreceptors), and aU are a- and j3-adrenomimetics of indirect (mediated) action. 

Ephedrine is an alkaloid that is present in various forms of the ephedrine family, and which is still extracted from Ephedra sinica and Ephedra equisetina. Because of the presence of two asymmetric atoms, there are four isomeric forms. Pseudoepinephrine (d-isoephrine) is a stereoisomer with pharmacological action that differs slightly from ephedrine. The pharmacological action of ephedrine is typical of noncatecholamine sympathomimetics of mixed action. It stimulates both a- and 8-adrenoreceptors, and simultaneously causes a release of norepinephrine from synaptic neurons. Its vasoconstrictive ability is approximately 100 times weaker than that of epinephrine however, the duration of action is approximately 10 times longer. It is much less toxic than epinephrine, which allows it to be used widely in medicine. 

As drugs of mixed action, amphetamines activate adrenergic receptors and simultaneously release endogenic catecholamines (norepinephrine and dopamine) from neurons of the brain and periphery. Sympathomimetic effects on the periphery are very similar to those of ephedrine. Amphetamine elevates systolic and diastolic blood pressure and has weakly expressed, broncholytic action. These effects are more prolonged, yet less expressed, than with epinephrine. The distinctive feature of amphetamines is their psychostimulatory activity. Larger doses can cause hallucinations and mental conditions similar to paranoid schizophrenia. As a sympathomimetic, amphetamine is sometimes used for uterine inertia. Synonyms of amphetamine are phenamine and benzedrine. 

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