Mining in focus
Conventional mining
vs surface miners
Several opencast mining operations are looking at using surface
miners rather than conventional mining methods to unearth coal
deposits. Edited by Leon Louw
M
method over a period of four months,
based on various performance
indicators. The conventional mining
system comprises two supersize
dozers for ripping and stacking the
material and a super-large wheel
loader for loading it onto dump
trucks with payloads of 130–190t.
Better HSE
Compared to the three mining
machines used at the mine previously,
using a surface miner significantly
reduced noise emissions.
Mining with the 4200 SM
likewise has a positive impact on dust
emissions. In contrast to the dozers
and wheel loader — all of which
generate considerable quantities
of dust that impact the work
environment — the dust produced
by a surface miner is contained in
the cutting drum housing. A dust
suppression system comprising an
integrated water spray system also
helps to additionally reduce and bind
the dust.
An analysis of the two mining
methods further demonstrated that
fuel consumption is about 79% lower
— and therefore also CO2 emissions
— with surface miners than when
using the conventional method. The
lower number of machines in use
additionally has a positive effect on
risk management, because fewer
machines mean a reduced risk of
accident at the mine.
The surface miner’s anti-vibration
cabin offers better ergonomics and
optimised working conditions for
the machine operator. The vibrations
generated in the 4200 SM were
rated as ‘low’ according to Australia’s
AS 2670-2001 standard, while the
ratings for the conventional systems
were higher.
Coal seams generally are of
varying thickness and separated
by interburden layers. Precisely
separating the various materials is
of tremendous importance if coal
is to be mined as cost-efficiently
as possible, because it significantly
reduces processing costs. Another
major cost driver in this regard is
the percentage of fines, as they are
much costlier to process than coarse
material.
For the study, a total of 100
samples (30t each) were analysed
during operation of the surface
miner to determine the particle
size distribution. Those samples
were compared with similar ones
taken from the conventional mining
equipment and identical mining
fields. Significant advantages
emerged when working with the
surface miner, which produced 14%
fewer fines at grain sizes of less than
2mm compared to the conventional
mining system. The portion of fines
to be processed dropped by 22% at
grain sizes of less than 1mm and
even by 36% at grain sizes of less
ining operators are
increasingly looking
at alternative mining
methods to the usual rip-and-stack
or drill-and-blast operations to
improve efficiencies and reduce
costs. One of the new methods
being advanced is to use a massive
machine called a surface miner.
German company Wirtgen, who
manufacturers surface miners, claims
that recent studies have shown that
surface miners offer considerable
advantages in terms of both
economic efficiency and the final
product.
In collaboration with RWTH
Aachen University, Wirtgen
conducted a study in a black coal
mine in Queensland, Australia.
The following article explores the
advantages that surface miners offer
in coal mining, based on the results
of this study. Please note that the
following is not the view of Mining
Mirror and that we remain impartial.
For the study, a Wirtgen 4200 SM
surface miner was integrated into an
ongoing operation for the selective
mining of coal and interburden.
Previously defined targets were
checked regularly to determine if
they were being met. The project
scorecard illustrated the advantages
of using a surface miner in this mine.
The production rates of the surface
miner were compared with that of
the previously used rip-and-stack
[32] MINING MIRROR NOVEMBER 2018
www.miningmirror.co.za