The increasing use of continuous miners in the extraction of high coal
seams has amplified the need for enhanced ventilation systems in the
headings. Owing to larger face dimensions and higher production rates,
more ventilating air is required to effectively dilute liberated methane to
acceptable concentrations. However, the increased air quantities raise and
entrain greater amounts of dust, to which the operator is subjected. Various methods (eg sprayfans, on-board scrubbers and jet fans) are
used in various configurations and combinations to ventilate the headings.
These arrangements generally result in a complex air flow pattern, which
complicates achieving an optimum balance between diluting methane and
minimising dust capture. In order to cost effectively investigate and propose solutions to this
problem for the South African coal mining industry, the Division of
Mining Technology has embarked on an extensive work program to
evaluate various ventilation methods presently in use. Four currently
generic ventilation patterns in various heading scenarios have been
simulated using the Computational Fluid Dynamics (CFD) computer
program. Evaluating these outputs against a predetermined set of criteria
allows the best system for a particular situation to be chosen. The
program also facilitates fine-tuning of an adopted system without
incurring the cost and inconvenience of doing such tests in situ. This process not only provides solutions at significantly reduced costs,
but also yields deeper insights into the factors affecting heading
ventilation than hitherto possible.