Abstract:
Abstract: Rotary roll extrusion pelleting technology is a kind of mainstream technology in the area of pellet forming technology, and the pellet mill has been widely used in the biomass-energy industry, feed industry, chemical industry, pharmacy, and so on. The pellet produced by the pellet mill has many advantages, such as a high forming rate, high absorption rate, high calorific value, and low pollution. But because of absence of the torque modeling theory, the existing pelleting technology with high consumption, low productivity, and low service life has been the bottleneck of industrial development. By a mathematical analysis, FEA simulation, and testing research, this paper aimed at developing an accurate torque model in the pelleting process of rotated roll forming. First, based on the unit force analysis and generalized Hooke law, the pressure distribution model along the die hole was founded. Then based on the DPC model and rolling processes, the FEA model of the pelleting process was created, and the stress distribution in the compacted zone was analyzed. Next, based on the results of the FEA, the pressure distribution in the compacting zone was set as aquadratic curve, and the pressure models in the compacting zone and extruding zone were built. Finally, the torque model in the ring-die pelleting process was developed. The experiments were designed to verify the model created, and the wireless torque testing system was used to analysis the torque datum. In order to eliminate the effect of the bending moment of the belt in pelleting process, two strain foils were stuck symmetrically along the same circumference of a shaft. The experimental material was chicken feed and the main components included Zea mays, wheat, bean, fish flour, bone flour, salt, and so on. The structural parameters of the pellet mill were as follows: the ring die radius was 175 mm, the number of rollers was 2, the ring die width was 110 mm, the die hole radius was 1.75 mm, the die hole length L was 35 mm, the percentage of the die opening area was 0.3, the roller radius was 80 mm, and the linear velocity was 6.1 m/s. When the pellet mill was in stability conditions, the torque data were tested in real time, and the average value in one minute was obtained as the torque value. At the same time, the pellets produced in one minute were collected and weighed to compute the volume of production. The tested results were as follows: the torque was 1 518.5 N·m, the production rate was 5.1 t/h, and the constant PN0 was 3.79 kPa. Based on the tested datum, all the model constants were determined and the torque model was developed. In order to verify the torque model, calculations and experiments were carried out in three other different linear velocities. It was shown that the computing datum was very close to the experimental results and the calculation error was less than 3%. The research was helpful to optimizing the structure, reducing energy consumption, and using the pellet mill efficiently.