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Computer simulation of the impact of fed-in mineral substances on air and methane flow in longwall goaf

This paper presents a mathematical model for sealing mine goaf. The model has been applied using VentZroby software for determining air distribution patterns in goaf varying over time as the goaf are gradually filled. The developed model is based on the balance of the volume of a mixture supplied and contained in the body formed in the goaf. The geometric body shape has been assessed on the basis of observations and the results from model studies available in literature. However, the real shape of the body formed in goaf from a supplied mixture has not so far been known. There is also no theoretical model of the flow of such a mixture through a porous medium that would allow the body shape in relation to the mixture parameters – such as viscosity and fluidity – and the other medium properties, to be determined. But even a simplified model of the mixture body and its variations presented in this paper allows – using VentZroby computer simulation software – the air flow distribution in goaf to be determined, and its variations over time while filling goaf with observed suspended matter. The prognostic calculations made for the first time reveal the impact of suspended matter applied to goaf on changes in the air and methane flow parameters, and also on the development of goaffire. An interesting case of prognostic simulations from applying a water-ash suspension to goaf areas is presented. In subsequent figures the phases of feeding goaf with a suspended matter in accordance with the assumed calculation scenario are presented. The observed variations in the height of filling the goaf in a D-31 longwall demonstrates the effects from applying suspended matter that spreads over a goaf over time. The outlet of the pipeline supplying a suspended mixture runs in the upper part of the D-31a (h = 2.5 m) ventilation airway, and in this case the suspended matter fills the goaf area to this height. We also noted that due to the slope of the goaf (see the elevations in the goaf area) the suspended matter supply pipeline has its outlet at the highest point of the goaf. This undoubtedly facilitates the penetration of suspended matter into the goaf. To complete the above it should be noted that such elements as the longwall slope and the point where the suspended matter is supplied in relation to the longwall slope or location of the fire centre is of great importance for fire prevention. The above example does not exhaust our fount of knowledge concerning these solutions. The VentZroby computer simulation software allows study of the application of suspended matter to goaf as a function of the location of the supply pipeline outlet, goaf area seal-tightness, fire location, and the spatial situation of the mined longwall.