Re-explosion hazard potential of solid residues and gaseous products of coal dust explosion

[Display omitted] •Solid residues and gaseous products after lignite coal dust explosion were collected.•Solid residues could explode again and are characterized with the Kst of 8.66 MPa‧m/s.•Compoents of gaseous product included CO, H2, CH4 and other CxHy gases.•Gaseous products were flammable, and had wide explosion limits and low LOC. In the present work, solid residues and gaseous products after the initial explosion of coal dust were collected by self-made devices, respectively, and their explosiveness was further studied to assess the re-explosion hazard. The results show that the solid residue can explode again, and its explosion pressure (Pex) and pressure rise rate ((dP/dt)ex) both increase gradually as dust concentration and ignition energy increase, but decrease with the larger particle size. Solid residue is characterized by a lower deflagration index (Kst) than raw lignite dust, but it can produce greater severity than some raw high-rank coal dust in some cases. The gaseous products of coal dust explosion are mainly composed of CO, H2 and CH4, and some trace gases. The volume fraction of CO and H2 in the gaseous products rises in proportion to the concentration of coal dust. For coal dust explosion with a concentration >200 g/m3, the gaseous products collected are flammable and have a wider explosion limit and a lower limited oxygen content. This research provides valuable information and reference for future prevention and control of secondary explosion disasters in coal mines.