Coal in South Korea.
The coal resources of South Korea are mainly anthracite. Most are contained in the Pyeong-an Supergroup of the late Permian period and are found in the Samcheok, Kangmung, Jeongsun, Yeongweol, Danyang, Munkyeong, Boeun and Honam coalfields. Other anthracites occur in the Daedong Supergroup of the early Jurassic period, being found in the Chungnam coalfield, parts of the Danyang and Munkyeong coalfields, and in the Yeoncheon and Kimpo regions. Compared with the coal seams of the Pyeong-an Supergroup, the distribution of coal seams in the Daedong Supergroup is small and the seam thicknesses are narrow.
Some lignite of Tertiary age occurs in the Kyeong Ju - Yeongil and Bukpyong regions, but this has not been mined because of the poor development of coal seams.
Total resources of coal in South Korea are estimated at 1,560 Mt of which 450 Mt are regarded as recoverable.
Because of falling output as a result of a drop in demand, the only coal currently being worked is in the Samcheok coalfield, part of the Pyeong-an Supergroup.
The anthracite coal seems of South Korea exhibit some general characteristics:
* Compared to other countries, the seams are relatively thin. Most are under 1.5 m thick except in a few structurally controlled zones.
* The anthracite is a high ash (30-40%), low sulphur (0.3-0.7%) and highly carbonised graphitic coal.
* The predominant dip of the seams is over 30 [degrees].
* The thickness and depth of the coal seams are controlled by a complicated geological structure. Major structures are compounded by secondary and even tertiary deformations.
* The carbonisation of the anthracite has been increased by strong deformation. Favourable coal seams occur in the crests and troughs of folds, and in the hanging walls of anticlines.
* Slippage and flow under the deforming stress has made the coal brittle or even pulverised. Many slickensides have developed in the coal seams. These factors have caused severe fluctations in the thickness of seams, causing serious mining problems.
The coal industry of Korea
The coal industry of Korea, which began in 1920, reached its peak in the mid-1970s following the oil price shock, with the development of some 350 coal mines having a total output of about 24 Mt/y.
However, the demand for coal has decreased drastically since 1987. The reasons for this include the stabilisation of oil prices; the general rise in the level of incomes in Korea, leading to the increased use of electricity and gas instead of anthracite for home consumption; and the relative rise in the price of anthracite resulting from increased costs of production. Taking 1985 as a base year (=100), by 1992 the price index for anthracite had risen to 121, whereas that of oil had fallen to 77.
The total consumption of anthracite in South Korea in 1987 was 26 Mt, comprising 23.59 Mt used as domestic fuel and 2.44 Mt for power generation. By 1992, these figures had fallen to 10.94 Mt and 1.96 Mt respectively, with output halved to 12 Mt/y.
Productivity and labour costs
Because of the bad ground conditions, the tunnels in South Korean coal mines have tended to be narrow, precluding the use of machine-intensive production methods. The labour-intensive methods employed and small scale of production at individual mines mean that productivity is remarkably low compared to foreign coal mines. In the mid-1980s the average output per man-shift was 1.22 t and by 1992 this had risen to barely 1.7 t, an annual increase of only 3%.
From 1988 onwards, however, the wages for coal industry workers increased rapidly owing to the increasing activity of labour unions following the development of other industries in Korea. Typical daily rates for mine labour rose from the equivalent of $US37.00 in 1988 to $59.00 in 1992, an average annual growth rate of 10%.
The labour cost increase of 10%/y strongly outpaced the 3%/y growth in productivity, resulting in the erosion of price competitiveness for Korean anthracite.
Beginning in 1989 the Korean Government introduced a closure programme for small-scale mines with little potential for economic viability. In the short span of four years, some 300 mines were shut.
However, if all Korean mines were to be closed, not only would the market for the sole indigenous Korean source of energy be lost, but so would any self-sufficiency capability should there be another energy crisis or trade war. It is a characteristic of coal mines that they are almost impossible to re-open after they have been closed. Therefore, it was deemed necessary to maintain a minimum number of coal mines in operation for reasons of national security.
The Korean Government decided that it must continue to provide support for the main coal mines deemed necessary to survive. To sustain a set level of output, conditions for the continuous ongoing development of coal mines must, it was considered, be made possible. However, a more basic solution would be to lower the costs of production, making the anthracite available at a lower price. This would help maintain demand, even though it would be at a lower level.
Thus, a number of mines were selected for modernisation, with a view to improving their productivity, re-establishing their competitiveness and maintaining a stable national output of around 8 Mt/y. The emphasis is on the development of those mines which have exploitable coal seems of 1.5 m thickness or more.
The South Korean Government established the Korea Mining Promotion Corporation (KMPC) whose principal activities are:
* Financing (including loans) for mining business funds;
* Purchasing, leasing or sale of mineral products, machinery, tools and materials for mining;
* Arranging education and training of personnel in the use of new equipment, including safety apsects, plus technical consulting in respect of mine modernisation.
Since 1989 KMPC technicians have been studying the use of declines and ramps as a means of access to mines in major coal-exporting countries with the most highly mechanised mines such as those in the U.S., Canada, Australia and South Africa. A study of the applicability of the decline system to Korean mines has revealed that productivity would be dramatically improved, allowing the introduction into the mines of modern trackless equipment. The existing small-sized tunnels (2.8m x 2.1m) would be replaced by tunnels of up to 5m x 5m cross-section, pneumatic drills would be replaced by 2-boom hydraulic drill jumbos, [0.25m.sup.3] rocker-shovels by [4-6m.sup.3] LHDs, small rail cars by free-steered haulage trucks, steel arch supports by rock bolting and shotcreting.
The changes, it is recognised, would not be made without problems, and the potential difficulties have also been studied. Some of the aspects considered are summarised below.
Cost of tunnelling
It was suggested that, by using large sized decline tunnels instead of the conventional small sized tunnels, investment costs would increase. However, the investment in large sized diesel LHDs and mine trucks improves the excavation efficiency. It has been concluded that the excavation cost of a conventional 2.8m x 2.1m tunnel and that of a larger sized 5m x 5m tunnel are effectively the same. The excavation efficiency in the conventional small size tunnel is 0.25m/person-day, while that of the large size tunnel is 1.11m/person-day..
If multiple headings are being driven, careful programming of the work takes maximum benefit from the mobility of the equipment and improves efficiency still further.
The rocks in Korean coal mines are weak and studies were made of tunnel support systems used in foreign coal mines which also have extremely weak rocks. In March 192 two engineers were sent abroad for this purpose.
It has been concluded that even if the drilling, charging and mucking stages were modernised and automated, this would be a waste of resources and efficiency if conventional steel arches were still used for tunnel support. Thus it was considered necessary to introduce, at the same time, a support system based on rock bolting, weld mesh and shotcreting. In 1992, KMPC began experiments with rock bolting and the successful results have confirmed the safety and efficiency of this system under Korean conditions.
The exhaust gases produced by the introduction of diesel-powered equipment required improved ventilation, calling for larger volumes of air. However, the larger section of tunnel employed offers much lower resistance to air flow than the small size of tunnel previously used, so that increased air flow does not, in general, call for much increase in the power demand for ventilation. The diesel equipment now being produced has a duplicated system of exhaust-gas filtation, so that the quantity of objectionable exhaust gases is in any case minimised.
The benefit of a ramp
Some doubts have been expressed at the value of an investment in a new ramp access system without, necessarily, changing the actual method used in winning the coal. However, studies undertaken by KMPC have shown that, even if the mining method remains unchanged, the benefit of a ramp system in reducing overall manpower in the mine and lowering the costs of transporting the coal to surface will, by itself, bring considerable improvements in productivity and thus a reduction in costs. For this reason, as a first objective, ramps are being introduced into Korean coal mines.
Meanwhile, it is recognised that the larger tunnel size will facilitate the introduction into the mines of larger coal-getting equipment. Thus the second objective will be to make use of the possibilities offered and subsequently introduce new coal-winning methods.
KMPC has so far supported the purchase of around 30 items of equipment for use by the private mining corporations Samchuk and Dongwon mines in developing access ramps. Samchuk initiated work on a decline in late 1992 and will begin to bring coal up the tunnel in late 1993. By 1995, it will be producing around 1.4 Mt/y, all of which will be brought to surface by this route.
It has been estimated that the introduction of the decline ramp system into Korean coal mines will, of itself, improve productivity from 1.7t/man-shift to 5-t/man-shift and reduce the production cost from $63/t to $37/t.
Such a reduction would restore the competitive commercial position of Korean anthracite.
Table 1: Large coal mines in Korea Mine Deposit Mineable Production Sector name resource reserves in 1992 (Mt) (Mt) (Mt) Dongwon 75.8 52.9 1.72 Private Samchuk 112.1 77.1 1.28 Private Kyungdong 48.1 33.6 1.12 Private Hanbo 49.0 34.1 0.51 Private Hamtae 33.1 17.9 0.51 Private Eoryong 11.2 7.8 0.06 Private Changseong 192.3 59.1 1.83 State-run Togae 72.6 49.1 0.82 State-run Total 594.2 331.6 7.85