Orifice plate wetting

Rietz Extruder This extruder, shown schematically in Fig. 18-49, has orifice plates and baffles along the vessel. The rotor carries nmlti-ple blades with a forward pitch, generating the head for extrusion through the orifice plates as well as battering the material to break up agglomerates between the baffles. Typical applications include wet... 

Class 11 flowmeters have no wetted moving parts to break and are thus not subject to catastrophic failure. However, the flow surfaces such as orifice plates may wear, eventually biasing flow measurements. Other disadvantages of some flowmeters in this class include high pressure drop and susceptibility to plugging. Very dirty and abrasive fluids should be avoided. 

The equipment system scheme is essentially the same as that shown in Fig. 6.14 but with two differences (1) The orifice plates are used for metering airflow rates and (2) Since the equipment is much larger than that used in the model investigation and therefore the feeding rate is much larger, the screw feeder for wet material feeding in the quasi industrial test is not as complex as that shown in Fig. 6.14 in structure, but is a common one. 

The main problem associated with falling film units is the need to distribute the liquid evenly to all tubes. All tubes must be wetted uniformly and this may require recirculation of the liquid unless the ratio of feed to evaporation is relatively high. Recirculation can only be accomplished by pumping. Distribution can be achieved with distributors for individual tubes, with orifice plates above the tubes and tubesheet, or by spraying. Updraft operation complicates the liquid distribution. 

The setup consists of a 0.0254 m ID and 1.52 m long glass pipe, which bears a canvas filter at its upper end, and which is sealed by an orifice plate at the bottom. This latter plate contains a single 0.4 mm ID orifice in its center. The apparatus is operated in such a way that the jet gas velocity approaches the speed of sound in the orifice. The filter keeps all material inside the system. To assess the degradation extent, one should screen the material by wet sieving through —325 mesh (44 pm). The attrition rate is defined as the ratio of the... 

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