Papers by Keyword: Twin Screw Pulping Extruder

Abstract: Usually the gearbox casing of twin screw pulping extruder was designed by experience and greater weight. In order to reduce the casing weight under the premise of ensuring its stiffness and strength, firstly the casting lower box and the weakest axle in the casing were analyzed with finite element method by ANSYS software. And then the optimum design was carried out to take the minimum volume as an objective function. Finally, the welding casing has been designed as considering the manufacturing cost. The results show that the weight of the casting lower box after optimization is 22.95% lower than that of the experience design, and the weight of the welding part is 19.09% lower than that. The work has certain significance for optimum design of gearbox casing.

Abstract: In order to select rational screw parameters for improving the pulping quality, efficiency and reducing specific energy, the paper studied the effects of the rotational speed of screw, lead number of reverse thread and slot width of reverse flight of the twin screw pulping extruder (TSPE) on specific energy, flux and pulping quality (reject rate, fiber length and fine component content) in the processes of extrusion mechanical pulping. The experimental results show that synthetically considering and pulping quality the efficiency, the screw rotational speed of 300 r/min–400 r/min is more appropriate. For poplar chips, the lead number should be greater than or equal to six. And for cotton stalks and wheat straws, the lead number should be no less than seven. For the combination screws of multiple extrusion zones, the slot width of the ultimate extrusion zone plays a decisive role on the fiber length. In addition, the slot width can also adjust the barrel pressure and the axial force of the screws. The work of the paper is significant for optimum design of the TSPE.

Abstract: Formulas of flux and power consumption of twin screw pulping extruder (TSPE) based on extrusion model deal with nearly all of geometrical and mechanical parameters of the twin screw and the material processed, they are not convenient for estimation and initial design of the machine. Adopting dimensional analysis based on similarity theory and considering the most important factors, such as outer diameter of screw, rotational speed of screw and average pressure between barrel and material processed, estimation equations of flux and power consumption of the TSPE are deduced in the paper, and the correction coefficients are determined by experiment data. The estimation results show that the estimation and theoretical results have similar changeable trend although there are some errors. The work is easy to apply in the estimation and initial design of the TSPE, and complement the design theory and method of the TSPE.

Abstract: In order to enhance design reliability of a co-rotating twin screw pulping extruder (TSPE), optimum design on screw parameters of the TSPE was studied based on the extrusion model. The maximum shear flux or the minimum power consumption, or the two synchronous optimizations were taken as objective functions, and constraint conditions, such as thread lead, depth of thread, screw rotational speed, number of reverse thread lead, actual top width of the flight, torsional strength and stiffness of the screw mandrel, and so on were confirmed base on actual requirements of the TSPE manufacture and application. The optimizing results show that two-objective optimum design results split the difference of the two single-objective optimum design, and it is the most economical in reducing manufacture cost of the equipment and pulping expenses.

Abstract: In order to calculate important design parameters, screw axial force and power consumption of twin screw pulping extruder (TSPE), considering actions of the solid material plug in reverse thread of the TSPE and according to static balance principle, an extrusion model including plug flowing and shearing in reverse thread is proposed in the paper. Based on the model, screw axial force, screw torque, power consumption and flow rate can be derived. When changing thread lead numbers or slot width on the flight of the reverse thread, theoretical calculating results and testing results are better consistent.