These days more and more emphasis is being placed on safety in almost all industries.
Occupational Health and Safety regulations are becoming increasingly strict, especially in the mining industry where there is always the possibility of loss of human life.  Therefore more thought and careful consideration need to go into making design decisions.  An area of particular concern is methane gas ignitions or explosions in underground coal mines.  Methane gas is naturally released from freshly cut coal and as such needs to be removed from the heading by some ventilation system to prevent the build-up of gas around the Continuous Miner (CM). For those who are not familiar with CM’s, they are machines that mine coal by driving a rotating drum with an arrangement of sharp spikes into a seam of coal and are usually controlled by an operator via a remote coil attached to the machine. Shown in Figure 1 is the development of a heading as the CM is cutting into the coal face. The friction from the cutting action generates heat and can even result in sparks.  Add this to a mix of adequate concentrations of methane gas as well as a cloud of coal dust and you have a recipe for disaster. Methane gas can ignite and burn at concentrations between 5% and 15%, and at concentrations of 9% the mixtures of oxygen and methane presents the optimum state for an ignition, provided that a significant heat source is present.

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Figure 1: Top view of a heading with CM on the right.

Recent incidents of methane gas ignitions in underground coal mines have raised many concerns and questions of “why all of a sudden”?  Thus, the need arose to investigate the reappearance of methane ignition incidents.  Coaltech (Coal Technology) is a research organisation established to conduct research specifically in the coal mining industry and they have set out to address this need.  Coaltech is at the forefront of improving safety in the underground coal mines and approached ESTEQ for a Computational Fluid Dynamics (CFD) solution to simulate the typical scenarios that could lead to methane ignitions or explosions.  ESTEQ provided Coaltech with the ‘NX’ and ‘FloEFD for NX’ solutions as the CAD and CFD tools of choice.  CFD simulation with the FloEFD technology is key in Coaltech’s research and allows for complex models to be analysed rapidly. Please see the follow up article on the breakthrough Coaltech has made with regards to underground coal mining ventilation:
Coaltech Breakthrough & Validation Study

A typical simulation entails modelling the ventilation inside the heading as it is being developed, complete with CM and scrubber arrangement, shuttle car, as well as methane gas released from the freshly cut coal.  Although it has only been applied recently, FloEFD has already provided Coaltech with valuable insights into the effects of the various ventilation systems by quickly and easily changing scrubbers or moving the cutting head of the CM up or down and performing “What if” studies.  Figure 2 shows typical velocity streamlines as air is blown into the heading from a jet fan and passes through the scrubbers.  Figure 3 shows the iso-surfaces of methane concentrations around the CM and shuttle car, highlighting areas of concern.

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[wptabtitle] Figure 2[/wptabtitle] [wptabcontent]

TrajectoriesFigure 2: Flow trajectories around the CM and shuttle car.


[wptabtitle] Figure 3[/wptabtitle] [wptabcontent]

iso-surfacesFigure 3: Iso-surfaces of methane gas concentration.