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In order to develop a highly efficient, simple-preparation and renewable explosion suppressant of composite powders, the superfine NaHCO3-shell powder (S-S) composite explosion suppressant was prepared by one-step method with airflow crusher to fulfill the mechanical dry coating of shell powder by NaHCO3, which solved the contradiction between dispersion and suspension force of explosion suppressant particles. The composition optimization and performance test of S-S composite explosion suppressant were carried out with the use of 20 L explosion tank and large tubular coal dust characteristics identification instrument. The results show that when the shell powder particles are coated with NaHCO3, the overall water absorption performance of the powder is reduced, the particle agglomeration phenomenon is weakened, and the dispersion is obviously improved. With the increase of NaHCO3 ratio, the ignition sensitivity of coal dust decreases, and the time to reach the first explosion Pmax is gradually delayed, and both Pmax and (dP/dt)max decrease. With the following explanations: NaHCO3 has a significant effect on reducing (dP/dt)max due to its chemical reaction, while shell powder is beneficial to reducing the Pmax due to its physical barrier effect. The suppression effect of S-S composite explosion suppressant on coal dust explosion is far better than that of pure NaHCO3 or shell powder.

To relieve dust pollution in open cut coal mines and reduce the hazards of coal dust pollution to the environment and workers we optimized the synthesis of a dust suppressant by graft copolymerization of environmentally friendly soy protein isolate with methyl methacrylate. This dust suppressant could effectively control dust pollution in open cut coal mines. The optimized conditions for graft copolymerization in this case were determined by a response surface experiment designed with Design-Expert 10 software. Characterization by scanning electron microscopy showed a significant morphology change of the dust suppressant and the generation of a rigid and dense layer on its surface after interacting with coal dust. The layer exhibited good bonding and dust suppression performance. The analysis with Fourier-transform infrared spectroscopy revealed the appearance of new absorption peaks near 1300, 1072, and 1631 cm

In order to improve the pertinence of coal dust explosion suppression technology, a 20 L spherical explosion characteristic test system and a dust minimum ignition energy test device were used to study the suppression differences of different particle sizes of coal dust with inert and active explosion suppressants. The results showed that the inert explosion suppressant was more effective in suppressing coarse coal dust, while the active explosion suppressant was more advantageous in suppressing fine coal dust explosion. The maximum pressure (Pmax) and maximum pressure rise rate ((dP/dt)max)) of 30 wt% NaHCO3 in the suppression of fine coal explosion decreased by 26.8% and 54.2%, respectively, compared with that of raw coal, while the suppression data of NaHCO3 to coarse coal was 25% and 30.8%. Kinetic analysis showed that NaHCO3 was better than shell powder (SP) in inhibiting fine coal and the activation energy reached 82.76 kJ/mol which increased by 94.5%. However, the activation energy of coarse coal increased more significantly under SP suppression. The global -small scale and local-large scale explosion suppression mechanisms of coal dust with different particle sizes were put forward. This study can provide scientific theoretical guidance for targeted coal dust explosion suppression.