# Application of EDEM Simulation for Calculating and Optimizing a Closed Coal Fly Ash Screw Conveyor
## 3 Results and Discussion
### Capacity Discrepancy: Calculation vs. Actual Test
These results reflect, in part, the accuracy of the employed method and emphasize the need for further research and adjustments to the parameters. However, accepting results with slightly lower accuracy to save time in the initial calculations of the design phase is also a consideration. This discrepancy is attributed to the heightened velocity of granular particles at elevated speeds. Consequently, meticulous consideration of the physical interactions among particles and between particles and the device's surface is imperative. In particular, when comparing the actual capacity curve with the EDEM-simulated capacity curve, it is observed that at 500 rpm, the actual capacity values are higher. However, the opposite is true at 300 rpm and 700 rpm, but these deviation values are not too high, measuring just under 2.11%. Therefore, it can be seen that the actual capacity curve and the EDEM-simulated capacity curve closely follow each other and have points of intersection. The capacity curve calculated using VBA has not achieved this, but with a relatively small deviation of about 6.74%, it can be completely acceptable in initial calculations, with the advantage of saving time. Figure 19 shows a comparison of the capacity of the screw conveyor using the VBA tool, the EDEM simulation, and the actual test. The combined application of these two methods enables evaluation across a broader range of speeds, encompassing both low and high speeds, where other conventional screw conveyor calculation methods may fall short. These conventional methods typically excel only within specific speed ranges, angles of inclination, and certain inlet sizes. In contrast, the EDEM method demonstrates superior performance in this context. Traditional methods for calculating screw conveyors often depend on factors such as filling ratio and inclination correction factor, as seen in methods such as the CEMA method or the KWS method. There are also empirical-based methods. The outcomes of these methods frequently produce capacity-speed curves that are linear within a particular speed range or under certain conditions. The DEM simulation method demonstrates superior accuracy compared to the rapid calculation VBA tool in the case of this screw conveyor. Employing a combined approach encompassing both the rapid calculation VBA tool and EDEM simulation software emerges  
Figure 19: Competition between calculation and EDEM simulation and actual test. as a highly effective strategy for designers, manufacturers, and optimizers. This integrated methodology not only enhances initial accuracy but also leads to cost reduction during the evaluation phase, particularly when assessed based on the 3D design model. Furthermore, virtual EDEM simulation affords insights into material movement patterns and facilitates the detection of potential design errors. The capacity curve, contingent on the screw conveyor's shaft speed, furnishes users with the adaptability to fine-tune capacity parameters. The utilization of both methods comes with distinct advantages and drawbacks. The quick design tool necessitates only fundamental material parameters such as density and friction coefficient between the fly ash and screw conveyor surface. The programmed rules facilitate rapid and smooth calculations, albeit with a trade-off in accuracy. Conversely, employing the EDEM software demands a comprehensive comprehension of material properties, precise material model construction, and longer processing times. On average, each simulation takes approximately 120 to 200 min. If exclusively relying on the EDEM method, optimization becomes more intricate and time intensive. To mitigate execution time in simulating complex systems, omitting stationary material particles can yield up to a 25% reduction in processing time. Additionally, adjustments to material size in the simulation model warrant consideration [11; 31].