# Application of EDEM Simulation for Calculating and Optimizing a Closed Coal Fly Ash Screw Conveyor
## 2 Materials and Methods  
### Specification of Coal Fly Asht  
The accurate selection of fly ash properties holds significant implications for the precision of calculations and simulations. Extensive research has been conducted to investigate various properties of fly ash, including bulk density, angle of repose, particle size distribution, particle shape, etc. The authors' methodology for determining the properties of coal fly ash involves leveraging research papers on fly ash to obtain the necessary material parameters for their calculation methods. Once these parameters are secured, they incorporate the GEMM_particle_material_8454 material from the Altair EDEM software version 8.2.0's material library. This material was chosen due to its close resemblance to the material property values derived from the aforementioned studies. Following this, a detailed analysis of the properties of coal fly ash is conducted as follows:  
The first property of note is the inherent angle of repose of the material, which has been extensively discussed by [5; 17]. This natural angle of repose is intertwined with other material attributes such as friction coefficient, bulk density, internal friction angle, and particle size. Initially measured in the eighteenth century, the angle of repose can now be assessed through experimental methods. In contemporary times, numerical techniques, such as the discrete element method (DEM), have enabled accurate determination of the angle of repose [18]. Figure 1 illustrates the principal method for measuring the angle of repose of a bulk material. This figure provides a visual representation of the method, making it easier to understand. A study conducted revealed that the angle of repose for fly ash obtained from a power plant measured 47 degrees [17]. This angle exhibited an upward trend in tandem with rising moisture content. Moreover, the particle size distribution of the fly ash exerted an influence on the angle of repose; finer particle distributions resulted in a lower angle compared to coarser distributions. In a comprehensive study on coal ash in Vietnam, encompassing its deposition and utilization [19]. The particle size and distribution of fly ash in Vietnam were also investigated in a study conducted by [20; 21]. The fly ash particles in Vietnam are characterized by their small size and high fineness, with particles smaller than 45 \(\upmu\)m accounting for up to 83.9%. Real-life images of fly ash and observations under an electron microscope are presented in Figure 2.  
The authors also conducted a study on the chemical composition of fly ash in Vietnam, where the predominant components were found to be SiO\({}_{2}\) and Al\({}_{2}\)O\({}_{3}\), constituting over 80% of the composition [21; 22; 23]. The detailed composition of fly ash is outlined in Table 1. \begin{table}
\begin{tabular}{c c} \hline \hline
**Component** & **Percentage** \\ \hline SiO\({}_{2}\) & 57.02\% \\ Al\({}_{2}\)O\({}_{3}\) & 23.82\% \\ K\({}_{2}\)O & 6.56\% \\ Fe\({}_{2}\)O\({}_{3}\) & 4.69\% \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Grain size distribution and chemical compositions of Vietnam dry fly ash. Reprinted from ref. [23]. Figure 1: The method for measuring the angle of repose of a bulk material. Figure 2: (**a**) Fly ash particle shape in natural state; (**b**) fly ash particle shape through scanning electron microscope. The study led by [24] delved into the bulk density of fly ash. This study conducted an extensive assessment of fly ash types worldwide, demonstrating that the bulk density of fly ash falls within the range of 640-1440 kg/m\({}^{3}\). Notably, the bulk density demonstrated an inverse relationship with particle size distribution, registering the highest values for fly ash with finer particles and the lowest for coarser distributions.