Reversed pitch element

Reverse pitch elements are used to generate backpressure and therefore create sections of 100%i fill that, for example, can be used to separate unit operations, or totally fill a mixing section. 

Wheat bran and sodium hydroxide were blended at room temperature in a separate reactor one hour before each experiment. Tlie initial L/S ratio was seven and the mixture was stirred for five minutes. The L/S ratio was increased to ten just before the introduction of the mixture into the twin screw extruder with a Nemo excentric-screw pump. Straw was introduced in the extruder s first section with a screw feeder. Straw was mixed with the alkaline dough in the first zone of the barrel through the neutral pitch element and the reverse-pitch screw element successively. The washing water was injected downstream from this zone, and the mixture was conveyed through the second reverse pitch located just downstream from the filtration module. The filtrate was collected and kept in a cold room before further processing, while the refined cellulosic fibres were gathered at the barrel outlet. 

FIGURE 831 Flow in a Kenics static mixer. The mixer consists of a pipe with heUcal elements of alternating reverse pitches. 

SE45/120 45 mm pitch/ 120 mm length transport screw element SE20/30(R) 20 mm pitch/ 30 mm length reverse screw element... 

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