Australia has a long history of underground mining. Even with
advances in open cut mining equipment, techniques and
economics, many orebodies are still best mined by underground
means. In addition, modern exploration tools are uncovering'
orebodies that are at increasing depths. South African mines are
currently producing from below 3 km, and developing down to
5 km depths - it is likely that Australian mines will also become
much deeper over the next 20 years. One of the most significant
technical challenges in deep mines is the problem of heat.
Community expectations and legislated standards continue to
drive operations towards improving the working conditions in
mines. The hazards and costs associated with chronic hot
working conditions (heat illness, poor safety, poor productivity,
higher operating costs and poor morale) are also becoming
increasingly recognised (Brake, Donoghue and Bates, 1998). The
exposure of miners to many other occupational hazards has been
reduced over the past 50 years. However, despite air-conditioned
cabins greatly reducing the heat stress on mobile plant operators,
there are still many Australian mine workers subject to levels of
thermal stress that existed a century ago. There are several
reasons for this, including a frequently-poor understanding of the
physiology of working in heat by mine management, no agreed
mining code of practice for working in heat, the lack of a robust,
practical-sized instrument to measure heat stress, the cost
pressures on the industry and, to some extent, deep-seated
traditional management and worker practices. However
significant progress has been made in many of these areas (Brake
and Bates, in press), with the net result that there is likely to be a trend towards installation of refrigeration of some form in many
Australian mines in the future. This will add directly to the cost
of operation, but will also have direct and indirect benefits,
including cost benefits. It should also be noted that Australia is
not at the forefront of adopting practices to manage temperatures
in the workplace: South African metal mines usually have
refrigerated cooling, and Canadian mines spend large sums on
heating, with heating costs (averaged over a full year) of up to
$A1 per tonne mined (Bandopadhyay et al, 1997).
The history of mine refrigeration dates back to 1919 when the
first plant was installed at Morro Velho, Brazil. By 1965, the total
installed capacity (worldwide) reached about 100 MW(R)i. Since 1965 the growth in mine refrigeration capacity has been
exponential, with a doubling every six or seven years (Howes and
Nixon, 1997). South Africa is by far the largest user of mine
refrigeration, with over 300 refrigeration machines installed.
This paper discusses the key design issues associated with the
application of refrigeration in underground metal or coal mines.
Whilst the emphasis is on large, surface plants, small, surface or
underground refrigeration plants can also be very effective in the
correct application and many of the principles of design and
operation are the same.