The level of securing dust deposits against the possibility of coal dust explosion in the drilled dog headings

The article presents the analysis how the real coal dust explosion hazard occurs at the distance of the initial 200m of the protective zone maintained along the entire length of driven inclined drift II - face 567 in Polish colliery KWK „BRZESZCZE”, which was used during realization of the project titled Modelling of the mechanism of explosive coal dust deposition in the vicinity of mined faces in terms of identification, assessment and levelling the possibility of its explosion financed by the National Centre for Research and Development in Poland. The mine dust level was between 0.014 kg/m3 and 0.193 kg/m3, and the coal dust level between 0.003 kg/m3 and 0.051 kg/m3, at the content of incombustible solids between 62.9% and 96.9%. In the analysed fragment of the mine working there was settled dry and volatile mine dust of transient water content between 0.1% and 3.8%. In a few measurement points (sidewalls, floor, and the dust explosion barrier) it was observed that the content of incombustible solids was lower than required by the regulations (unsecured mine dust), which resulted from the insufficient application of stone dust and increased intensity of dust settlement, especially in the area near the longwall face. Analyses of the fraction distribution of the settled mine dust showed the presence of fine dust, while coarser fractions were found in the places of lowered content of non-combustible solids. The conclusions indicate that it is necessary to modify the currently applied dust-explosion prevention measures, which ought to adjust the amount of stone dust applied in given sections of the safety zone and the stone dust ought to be applied with more diligence