# 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  
The material property of fly ash from coal-fired power plants in Vietnam has been determined. These parameters are of great importance in the calculation, simulation, and evaluation of technology and design. A set of general material parameters is provided. The detailed material parameter set is shown in Table 1. The most important properties for research and calculations are the angle of repose, the bulk density and solid density of the material, and the friction coefficients between the material and the equipment. In addition, the size parameters of materials, as well as the distribution ratio of materials, should also be considered. The fast calculation tool based on the Roberts theory is well suited for the calculation and optimization of screw conveyors for the rapid identification of parameters with good accuracy. The simulation model in the EDEM software fully reflects the operation of the screw conveyor, the operation of the material particles, higher capacity accuracy, and is close to reality. Table 5 presents a comparison of the capacity between the two methods and the actual model. This comparison provides a clear understanding of the performance and accuracy of each method in relation to the actual model. It can be observed that among the screw conveyor speeds of 300 rpm, 500 rpm, and 700 rpm, the results obtained from the quick calculation using the VBA Excel software tool show a minimal error rate at a speed of 500 rpm. Specifically, when compared to the actual values, the error rate is only 3.87%. At speeds of 300 rpm and 700 rpm, the corresponding error rates are 4.17% and 6.74%, respectively. This demonstrates the feasible accuracy and effectiveness of the VBA Excel tool in these calculations. Additionally, the disparity between the simulation and the actual experiment is even lower, at just 0.97%. This level of error is quite small and may be deemed acceptable. The accompanying line chart visually represents the error rate between the two methods. This demonstrates the high level of accuracy achieved through both calculation and simulation approaches. A comparative study was conducted to assess two methods for calculating the flow of granular materials: a rapid calculation tool and DEM simulation. As observed in Figure 19, at speeds of 300 rpm, 500 rpm, and 700 rpm, the deviation between the actual capacity and the capacity calculated using the EDEM method is consistently lower compared to the deviation with the VBA method. This suggests that the \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**No.**} & **Speed** & **Capacity** & **Capacity** & **Capacity** & **Difference** & **Actual** & **Deviation Ratio** \\  & **(rpm)** & **in EDEM** & **in UBA** & **(ton/h)** & **2** & **between** & **Capacity** & **EDEM/VBA** \\  & & **(kg/s)** & **(ton/h)** & **(ton/h)** & **2** & **Methods** & **(ton/h)** & **(\%/\%)** \\ \hline
1 & 100 & 7.5 & 27.0 & 23.1 & 14.4\% & & \\ \hline
2 & 200 & 12.5 & 45.0 & 41.1 & 8.7\% & & \\ \hline
3 & 300 & 16.0 & 57.6 & 54.3 & 5.7\% & 56.7 & 1.66\%/4.17\% \\ \hline
4 & 400 & 17.9 & 64.4 & 62.5 & 3.0\% & & \\ \hline
5 & 500 & 18.8 & 67.7 & 65.7 & 2.9\% & 68.3 & 0.97\%/3.87\% \\ \hline
6 & 600 & 18.5 & 66.6 & 64.0 & 3.9\% & & \\ \hline
7 & 700 & 17.5 & 62.8 & 57.4 & 8.7\% & 61.5 & 2.11\%/6.74\% \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Capacity between 2 methods calculation and actual test. EDEM method may provide a more accurate estimation of capacity at these speeds. Indeed, while the deviation for the EDEM method ranges from 0.97% to 2.11%, the VBA method consistently exhibits a deviation between 3.87% and 6.74%. At the higher speed of 700 rpm, the deviation of the EDEM method from reality is relatively low, at only 2.11%, whereas the VBA method shows a much higher deviation of 6.74%. The discrepancy between the two methods also takes a substantial leap to 8.7%.