Ways and Means to Achieve Higher Recovery of the Deposits in the Lignite Mines of the Koflach District in the Alps

Summary

In 19791 1.6 million tons were mined out of the lignite mine situated in the western part of Styria; it represented approximately 60 per cent of the total output of the Austrian coal mining. This figure is published in all reports of world mining and international statistics tinder “other European mining production”.

Based on this west-Styrian coal production a new 330 MW-power station is now under construction to supply power from 1983 for the production of one million tons of coal per year until 2008. This power station is supposed to use the latest technology of combined heat and electricity generation.

The west-Styrian coal production coal deposits are divided into two different geological deposits, separated from each other. The main district in Voitsberg Köflach contains up to three lignite seams in the form of varying synclines; the adjoining district, 40 km to the south, in the Wies Eibiswald area, has a flat seam of sub-bituminous coal.

81.2 million tons of proven coal and 20 million tons of possible coal deposits were mentioned by W. Petraschek for the Koflach-Voitsberg district in 1926. 92.7 million tons of lignite were mined from 1926 to 1979. Explorations carried out from 1939 on the volume and extension of the deposit were brought to an end in 1976. According to the 1980 classifications 40.3 million tons of proven and 6.3 million tons of possible deposits were estimated. Space problems determined the different kinds of technological development in the several mines of the main district (that includes housing and living space for approximately 30,000 people).

Due to modernization in the open-pit mining technology from 1950, a series of deposit sections unused underground in the past decades were mined in open pit mining. Old coal pillar fields—often with less than 0.1 million tons total reserves—were mined for production.

The balance between underground and open-pit mining of four to five production deposits has become the guiding principle in the economics of the whole mining operation. The machinery, such as shovel excavators, used for open-pit mining has not been changed for more than 30 years. Special attention was paid to the current modernization of haulage methods. For more than 20 years the development cost of open-pit mining made it possible to offset the high costs resulting from underground mining and moreover to achieve a higher deposit recovery.

The ratio of overburden to coal in the individual operations varied between 1:1 and 6:l. The reason why increasingly unfavourable overburden-coal ratios could be accepted was the modernization of overburden technology. The use of concrete pile wall and bolting technology has led to an increase in mineable reserves.