# Application of EDEM Simulation for Calculating and Optimizing a Closed Coal Fly Ash Screw Conveyor
## 2 Materials and Methods
### Altair EDEM Simulation  
The closed screw conveyor's 3D model was generated using 3D software 2023. Subsequently, this model was imported into the EDEM software for the purpose of conducting calculations. The Altair EDEM software version 8.2.0 (2022.2) was utilized, operating on a Dell Precision 5540 computer. This computer is equipped with an Intel(r) Core(tm) i7-9850H processor and 32 GB of DDR4 memory. A 3D model of the closed screw conveyor used in the simulation is illustrated in Figure 6, depicting the conveying speed of the bulk material within the screw conveyor. The optimal speed for the screw conveyor is set at 500 rpm, and the screw pitch is measured at 250 mm. The length of the closed screw conveyor feed is established at twice the screw pitch, equating to 500 mm. This configuration is designed to ensure uniform power distribution, prevent jamming, and apply even pressure at the feed port. Material flow is initiated by a rotary valve with a capacity of approximately 30 kg/s. This process is depicted in detail in Figure 7. In the simulation model, a factory environment was constructed, with a throughput capacity of 30 kg/s. Figure 6: 3D model of closed screw conveyor in simulation. Figure 7: Drawing of fly ash conveyor experiment. The precision of the physical parameters in this method constitutes a pivotal factor in ensuring the reliability of the simulation outcomes. Consequently, a thorough examination of material properties is imperative. Equally significant is the selection of an appropriate DEM modeling approach [30]. In this study, a calibration of the repose angle was carried out in EDEM using the material model depicted in Figures 8 and 9. The resulting natural repose angle closely aligns with the material properties outlined in Table 2, measuring 47.5 degrees, as shown in Figure 9. The procedure conducted by the author's team within the EDEM software is presented in Figure 10.  
In this study, material calibration was conducted to assess the static response angle of the fly ash. However, to enhance the accuracy of the simulation, it is advisable to additionally measure the dynamic response angle. This method is thoroughly and precisely analyzed in the study by [PERSON] et al. [12]. Figure 8: Established basic particle unit of the particulate material. Figure 10: Flowchart of simulation in Altair EDEM software version 8.2.0. Figure 9: The angle of repose simulation test of the particulate material. In this study, we have drawn upon findings from various research endeavors on coal fly ash in Vietnam. The material property parameters specific to coal fly ash employed in the simulation are presented in Table 1. At the range of screw conveyor speeds from 100 to 700 rpm, simulations were conducted 5 times to ensure accuracy for each speed. At speed 500, which is the operating speed, the recorded capacity of the screw conveyor averages 18.8 kg per second, which translates to 67.7 tons per hour. The capacity graph for a speed of 500 rpm is depicted in Figure 11.  
It is evident that from 2 s to 10 s, the screw's capacity consistently fluctuates around 18.8 kg/s. This demonstrates that the screw conveyor operates in a stable condition. The capacity diagram for the screw conveyor at other speeds is illustrated in Figures 12-17. Figure 6:0 Capacity diagram of coal fly ash at speed 500 rpm. Figure 6:1 Capacity diagram of coal fly ash at speed 100 rpm—capacity about 7.5 kg/s. Figure 6:2 Capacity diagram of coal fly ash at speed 200 rpm—capacity about 12.5 kg/s. Figure 6:3 Capacity diagram of coal fly ash at speed 600 rpm—capacity about 18.5 kg/s. Figure 6:4 Capacity diagram of coal fly ash at speed 700 rpm—capacity about 17.5 kg/s. Figure 6:5 Capacity diagram of coal fly ash at speed 300 rpm—capacity about 16.0 (kg/s). Figure 6:6 Capacity diagram of coal fly ash at speed 400 rpm—capacity about 17.9 (kg/s). From Figures 12-17, it can be observed that in the lower velocity range, it takes more time to reach a steady state.