چكيده به لاتين
In this work, simulation of waste polymers was studied inside a rotating drum. Used tire was selected as one of the waste polymers. In this regard, Discrete Element Method (DEM) and Eulerian approach were used. Since performance and efficiency of rotary reactor were highly affected by the flow of particles, the hydrodynamic of a rotary bed was studied using the both methods. The effects of essential parameters such as rotating speed and fill level on particles behavior were examined. The segregation phenomenon due to the differences in sizes of particles as well as cohesiveness was studied using DEM. Performance of the rotating reactor was influenced by temperature distribution and heat transfer rate. Therefore, heat transfer was simulated by DEM coupled with conducive heat transfer and Eulerian models using kinetic theory of granular flow. In order to accurately measure heat transfer using DEM, the effect of physical mixing on thermal mixing was investigated. Also, the obtained model for segregation phenomenon was used for heat transfer measurement. Considering the results of the rotary reactor simulation, selection of an appropriate kinetic model plays an important role. Experimental studies of pyrolysis process were done in the rotary reactor. They were conducted under nitrogen atmosphere and in the wide range of operating temperatures. The obtained values from pyrolysis process were reported for gas, liquid and solid phases. The results indicated that by increasing the temperature up to 550 °C, the amount of liquid increased. However, increasing the temperature above 550 °C would be resulted in decreasing the liquid amount. Amount of the produced gas increased with increasing temperature. While the amount of solid decreased with increasing temperature. Using the experimental data, the coefficient of the kinetic model was optimized. The comparison of simulation results with experimental data showed that the relative error is less than 14.3% for low temperatures whereas it is approximately 28.5% for higher ones. Furthermore, CFD simulation results in different conditions were obtained and discussed. The results implied that when reaction heat increased from 100 to 300 kJ/kg, the time required for 95% conversion, increased from 93 to 96 minutes. Thus, an increase in the reaction heat did not have significant effects on reaction rate. The heat transfer coefficient also greatly influenced heat transfer rate. As an example, when the heat transfer coefficient increased from 5 to 100 W/m^2 K, the required time for 95% conversion reduced from 165 to 92 minutes. While other reaction conditions remained constant, increasing the reactor temperature from 600 to 950 °C resulted in time reduction required for 95% conversion from 94 to 27 seconds.
