## 3 Results and Discussion
### Analysis of Explosion Residues
The explosion suppression process of the MSA-NaHCO\({}_{3}\) composite powder explosion inhibitor involves material reactions related to physical inhibition:  
\[2\mathrm{Fe(OH)}_{3}\underset{\mathrm{Pyrolysis}}{\rightarrow}\mathrm{Fe}_{2}\mathrm{O }_{3}+3\mathrm{H}_{2}\mathrm{O}\uparrow \tag{2}\]  
\[2\mathrm{Al(OH)}_{3}\underset{\mathrm{Pyrolysis}}{\rightarrow}\mathrm{Al}_{2} \mathrm{O}_{3}+3\mathrm{H}_{2}\mathrm{O}\uparrow \tag{3}\]  
\[2\mathrm{NaHCO}_{3}\underset{\mathrm{Pyrolysis}}{\rightarrow}\mathrm{Na}_{2} \mathrm{CO}_{3}+\mathrm{H}_{2}\mathrm{O}\uparrow+\mathrm{CO}_{2}\uparrow \tag{4}\]  
\[\mathrm{Na}_{2}\mathrm{CO}_{3}\underset{\mathrm{Pyrolysis}}{\rightarrow}\mathrm{ Na}_{2}\mathrm{O}\uparrow+\mathrm{CO}_{2}\uparrow \tag{5}\]  
\[\mathrm{Na}_{2}\mathrm{O}+\mathrm{H}_{2}\mathrm{O}\rightarrow 2\mathrm{NaOH} \tag{6}\]  
Chemical inhibition is achieved through homogeneous and heterogeneous reactions of solid inhibitor particles after entering the combustion-explosion region, as well as multiple chain reactions with the free radicals subject to combustion-explosion chain reaction. These reactions consume the key free radicals O- and OH- that maintain the combustion-explosion chain reaction and limit the exothermic reaction between the free radicals H, OH-, and O-, thus inhibiting the combustion-explosion reaction. The explosion of oil shale dust is a process of devolatilization-homogeneous combustion and heterogeneous combustion, in which the volatile content is separated and mixed with oxygen to cause combustion [33; 34; 35]. The explosion chain reactions resulting from the mixing of the volatile content in the oil shale with oxygen typically include:  
\[\mathrm{C}_{\mathrm{n}}\mathrm{H}_{\mathrm{m}}\rightarrow\mathrm{C}_{\mathrm{n }}\mathrm{H}_{\mathrm{m-1}}\cdot+\mathrm{H}\cdot \tag{7}\]  
\[\mathrm{C}_{\mathrm{n}}\mathrm{H}_{\mathrm{m}}+\mathrm{O}_{2}\rightarrow \mathrm{C}_{\mathrm{n}}\mathrm{H}_{\mathrm{m-1}}\cdot+\mathrm{OH}\cdot \tag{8}\]  
Figure 13:0  
Figure 13:1  
Figure 13:2  
Figure 13:3  
The reactions of the free radicals in the inhibitor with those subject to explosion chain reaction typically include:  
Figure 13:4  
Figure 13:5  
Inhibition Mechanism of MSA-NaHCO\({}_{3}\) Composite Powder Explosion Inhibitor on Oil Shale Dust Explosion  
A physical model suitable for describing the suppression effect of the MSA-NaHCO\({}_{3}\) composite powder explosion inhibitor on oil shale dust explosion, as shown in Figure 15, was built based on the explosion mechanism of oil shale dust while taking into account the suppression behavior of the inhibitor during explosions. Firstly, the oil shale dust and MSA-NaHCO\({}_{3}\) composite powder explosion inhibitor form a dust cloud. Then, after being excited by external energy, the two dusts are heated by external energy at the same time. The oil shale dust is decomposed into shale oil and volatile matter by heating, which combines with oxygen in the air to trigger combustion reaction. The explosion reaction takes place in two different explosion paths: devolatilization-homogenous combustion and heterogenous combustion. Under the action of the explosion shock wave, the explosion inhibitor particles are broken and separated into MSA, NaHCO\({}_{3}\), and metal hydroxides in MSA. The oil shale particles are coated by fine MSA, which can prevent the oil shale particlesfrom radiation heating, thus playing the role of coating isolation. The decomposition of NaHCO\({}_{3}\) and metal hydroxides in MSA is endothermic, and large amounts of NaOH, CO\({}_{2}\), H\({}_{2}\)O, and Fe\({}_{2}\)O\({}_{3}\) are generated in the decomposition reaction, which plays the role of endothermic cooling. CO\({}_{2}\) and H\({}_{2}\)O compete for space with O\({}_{2}\) in limited environment and play the role of gas inerting.