JUSTIFICATION OF EXTRUDER PARAMETERS WITH FLEXIBLE SCREW ELEMENT

Abstract

For dry grain extrusion, autogenous single-screw extruders are mostly used, in which more than 85% of the supplied energy is spent on overcoming frictional forces. This leads to heating of the body and screw of the extruder and uneven wear along their length. The greatest wear is observed in the zone of maximum pressure and temperature. The wear of the screw causes a decrease in the productivity of the extruder and a deterioration in the quality of the extrudate. In addition, in case of wear of the ridges, it is necessary to change the screw, that is, the costs associated with the repair and maintenance of the extruder increase. In order to increase productivity and reduce maintenance costs, a sectional design of the working part of the extruder is proposed, the characteristic feature of the screw of which is that grooves are cut on the outer surface of the section along the helical line, into which spring segments are inserted. The sections of the screw are installed close together, and their grooves form a continuous screw line. Moreover, the width of the grooves allows the springs, as a result of periodic pressure changes in the pre-matrix zone of the extruder, to move along the axis of the screw. Determination of rational parameters and modes of operation of the extruder with an elastic screw element was carried out using the method of planning multifactorial experiments. The specific performance of the extruder was chosen as the optimization criterion. It was found that with the diameter of the extruder screw 50 mm, the temperature of the extrusion process 142...145 0С, the moisture content of the grain mixture 18.0...18.6% and the diameter of the die 5.5 mm, the following values of the factors are rational from the point of view of the maximum specific productivity of the extruder: screw rotation frequency 330...480 rpm; the depth of the screw channel is 5.3...7.1 mm; screw pitch 20...21mm; the number of grooves cut on the inner surface of the extruder body is 7...9 pieces.