# Simulation and Catastrophe Detection of Spontaneous Combustion Processes in Suffide Ores
## 2 Materials and Methods
### Experimental Equipment and Conditions  
The complete experimental setup, independently developed according to the practical plan, is shown in the diagram of Figure 2 and in the physical picture of Figure 3, respectively. It mainly consists of a programmable high-temperature test chamber, a simulated ore heap, an Agilent data acquisition system, temperature probes, and a portable sulfur dioxide (SO\({}_{2}\)) detector. Before the experiment, the ore samples are mixed with approximately 0.48 kg of water to achieve a moisture content of 5%. After mixing, the mixture is allowed to settle for 1 h. The ore is then evenly and steadily stacked on a tray within a programmable high-temperature test chamber. An Agilent data acquisition system and temperature probe are connected, and a portable sulfur dioxide (SO\({}_{2}\)) detector is positioned at the outlet of the metal pipe. High-temperature-resistant materials are used to seal any gaps between the ventilation openings and the pipe to minimize temperature loss and gas leakage. The temperature gradient heating process begins at an initial temperature of 25 \({}^{\circ}\)C, which is incrementally increased by 5-10 \({}^{\circ}\)C. Once each target temperature is reached, it is  
Figure 3: Physical picture. \begin{table}
\begin{tabular}{c c c c c} \hline measurement point & A & B & C & D \\ \hline Coordinates/mm & ( 0,0,150 ) & ( \(-\)75,\(-\)75,80 ) & ( \(-\)32,\(-\)32,120 ) & ( \(-\)140,\(-\)140,10 ) \\ \hline measurement point & E & F & G & H \\ \hline Coordinates/mm & (113,113,25 ) & (5,5,80 ) & ( 38,38,40 ) & ( 135,135,5 ) \\ \hline \end{tabular}
\end{table} 
Table 3: Temperature measurement points distribution. Figure 2: Diagram of the self-developed experimental setup. 1—Programmable high-temperature test chamber. 2—Simulated ore pile. 3—Agilent data acquisition system. 4—Temperature probes. 5—Portable sulfur dioxide (SO\({}_{2}\)) detector. allowed to stabilize for 5-10 min. The maximum experimental temperature does not exceed 300 \({}^{\circ}\)C. SO\({}_{2}\) concentration data are recorded throughout the experiment. Subsequently, the temperature and SO\({}_{2}\) concentration data from the acquisition system are transferred to a computer for further analysis and processing. Extracting the Information of the Whole Unsteady Process of Spontaneous Combustion of Suffide Ore Heap  
The temperature data obtained from the indoor simulation experiments are influenced by multiple factors, including the temperature gradient increment in the programmable high-temperature test chamber and the oxidative self-heating of the ore. The former primarily affects the temperature variations at different measurement points within the ore heap. Consequently, the experimental data alone are insufficient for exploring the nature of the entire unsteady process of spontaneous combustion in the sulfide ore heap. To address this, it is necessary to extract useful information from the entire unsteady process of spontaneous combustion while filtering out experimental noise and accounting for the influence of the temperature gradient increment in the test chamber. Given this context, the study employs wavelet analysis to decompose the measured temperature sequence into low-frequency and high-frequency components. The low-frequency sequence captures the effects of temperature gradients in the constant temperature chamber, while the high-frequency sequence reflects the intrinsic spontaneous combustion process of the ore. The high-frequency component contains detailed information about the entire unsteady process of spontaneous combustion in the sulfide ore heap. However, the choice of wavelet function significantly impacts the results of wavelet decomposition and reconstruction. Different wavelet functions can lead to substantial variations in the analysis of the same temperature sequence. Therefore, selecting the most appropriate wavelet function is critical for accurate analysis.