Abstract： To evaluate the influence of inert mediums on explosion hazard of coal dust， and ensure safety in production, Godbert-Greenwald furnace apparatus was used to study the influence of diffusing pressure, content of inert mediums NH₄H₂PO₄, KH₂PO₄, Ca(H₂PO₄)₂ and CaCO₃ powders, as well as particle size of NH₄H₂PO₄ and CaCO₃ powders on minimum ignition temperature of coal dust cloud. The results show that the effect of high diffusing pressure is more significant, and the best diffusing pressure is 0.03 MPa. The minimum ignition temperature of coal dust cloud is the lowest, which is 594 ℃ at this diffusing pressure. The minimum ignition temperature of coal dust cloud increases with the increase of inert mediums content, and there are mutation concentrations. The mutation concentrations （mass fraction） of NH₄H₂PO₄, KH₂PO₄ and Ca(H₂PO₄)₂powders are all 28.6 %, that of CaCO₃ is 33.3% . According to the inhibition effect of inert mediums to the minimum ignition temperature of coal dust cloud, the order from strong to weak of the inert mediums isNH₄H₂PO₄, Ca(H₂PO₄)₂, KH₂PO₄, and CaCO₃. The minimum ignition temperature of coal dust cloud increases with the decrease of the inert medium particle size. The influence of size change of CaCO₃ powders on inhibition effect is more obvious than that of NH₄H₂PO₄．

Keywords: coal dust; minimum ignition temperature; inert medium