## 4 Conclusions  
Based on the consideration of environmental protection and the underground safety of coal mine, a preparation method of new composite powder explosion inhibitor based on industrial solid waste is proposed to suppress an underground coal dust explosion, and the explosion suppression effect of coal dust is experimentally studied. It is found that modified solid waste materials--modified red mud (MRM), modified slag (MSA), modified fly ash (MFA) and modified sludge (MSU)--as the load, NaHCO3, KH2 PO4 and Al(OH)3 as the carrier, and the industrial solid waste-based composite powder explosion inhibitorscan be successfully compounded by wet coating by solvent-crystallization (WCSC) and dry coating by ball milling (DCBM).  
In terms of the underground safety of a coal mine, the new composite powder explosion inhibitors can effectively reduce the explosion overpressure of coal dust and suppress the explosion of pulverized coal at the content of 40-50%. The paper also compares the explosion suppression effect and economic analysis between the explosion suppression experimental results and the powder explosion inhibitor commonly used in industrial production. It is found that using industrial solid waste-based composite powder explosion inhibitors to suppress a pulverized coal explosion can effectively reduce the use cost of an explosion inhibitor and the manufacturing cost of explosion suppression equipment and increase the explosion suppression effect on coal dust. In terms of the explosion suppression effect and cost, industrial solid waste-based composite powder explosion inhibitors have a good application prospect. In addition, considering the environmental protection of coal mines, the modified industrial solid waste combined with a small amount of active explosion suppression materials can synthesize explosion inhibitors. The modified solid waste has no heavy metals or toxic substances, and a small amount of NaHCO\({}_{3}\), KH\({}_{2}\)PO\({}_{4}\) and Al(OH)\({}_{3}\) basically have no impact on the underground soil environment of coal mines. Therefore, the industrial solid waste-based composite powder explosion inhibitor can avoid polluting the application environment.  
According to the current explosion suppression measures in the coal mine, the industrial solid waste-based composite powder explosion inhibitor can be sprinkled into the roadway with more coal dust in a certain proportion. When the coal dust is lifted by the shock wave, the new composite powder explosion inhibitor can be mixed in the dust cloud to prevent and suppress the coal dust explosion. In addition, the industrial solid waste-based composite powder explosion inhibitor can be placed in the explosion-proof groove at the top of the roadway. When the shock wave overturns the explosion-proof groove, the new composite powder explosion inhibitor forms a dust cloud, which can suppress the explosion flame. In addition, the industrial solid waste-based composite powder explosion inhibitor can be placed in the fixed explosion inhibitor. When the explosion suppression device is triggered, the new composite powder explosion inhibitor is ejected within the specified time, forming a dust cloud in the roadway, so as to achieve the purpose of suppressing the coal dust explosion.  
Conceptualization, B.L. and Y.Z. ([PERSON]); data curation, B.L. and N.M.; formal analysis, B.L.; investigation, B.L. and K.X.; methodology, B.L., K.X. and Y.Z. ([PERSON]); supervision, Z.H. and N.M.; validation, K.X. and Z.H.; writing--original draft, K.X.; writing--review and editing, B.L., K.X., Y.Z. ([PERSON]) and Y.Z. ([PERSON]). All authors have read and agreed to the published version of the manuscript.  
This work was supported by the National Natural Science Foundation of China (52074066).  
Not applicable.  
Informed Consent Statement: Informed consent was obtained from all subjects involved in the study.  
Not applicable.  
The authors declare no conflict of interest.