New method to neutralise flooded opencast mines

Pilot project

Quelle/Source: GMB GmbH

GMB GmbH developed a new method based on submerged floating pipes equipped with nozzles (GSD method) for the neutralisation of pit lakes of former lignite mines. This concept was demonstrated successfully for the first time on behalf of LMBV in Lake Scheibe, Lusatia

Quelle/Source: GMB GmbH

Separate sources installed on the shores enrich the waters of the lake with lime and CO₂

Quelle/Source: GMB GmbH

The lime is stored in silos with a capacity of 100 m³. They are located at the fixed facility on the lake shore

Quelle/Source: GMB GmbH

A dosage system ensures the right quantity is introduced

Quelle/Source: GMB GmbH

The mixer blends the lime with water from the lake according to a predefined ratio. Pipes then carry the suspension to the lake

Quelle/Source: GMB GmbH

Chemical industry standard pumps provide the necessary pressure

Quelle/Source: GMB GmbH

Six nozzle pairs in a horizontal arrangement inject the mixture of lime and water into the lake approximately 50 centimetres below the surface. Here, the GSD method uses the natural phases in the lake's circulation

Quelle/Source: GMB GmbH

Booster pumps transport collected lake water to the CO₂ gas release reactors, where the liquid is enriched with carbon dioxide from two 50 000 litre tanks

Quelle/Source: GMB GmbH

The mixture is then fed into pipes and pumped into the lake around 25 metres beneath the surface

Quelle/Source: GMB GmbH

Luftaufnahme Scheibesee # View from the air: Scheibesee

Quelle/Source: GMB GmbH

Lignite can only be extracted from opencast mines if the ground water level is lowered to below the coal seam. This has a strong influence on the region’s water balance. Depending on the chemism from the overburden, the rising ground water after mining in the pit lake may become acidic due to pyrite weathering. Thus ground water remediation projects seek to balance out the ground water deficit and to neutralise the lakes in the former mines so that flora and fauna may be established.

Lime is usually used in this process for example using ships to introduce lime into the lake water with sprinkler systems. Large quantities of lime are needed to treat an entire water body, however, as there is only a low level of blending that takes place in the process. GMB GmbH developed the UNP-Underwater Nozzle Pipelines (German: GSD-Getauchte Schwimmleitung mit Düsen) method as an alternative: lime mixed with lake water is pumped through the nozzles of floating pipes into the lake, where it uses the natural lake circulation to blend thoroughly, distributing the suspension evenly...