Solidification / Immobilisation of hazardous waste for subterranean storage

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Courtesy of econ industries GmbH

The use of subterranean salt mines for the final storage of inorganic hazardous waste is state of the art in Germany, and in fact most other European countries. However, the technical requirements to prepare the waste in an appropriate way are quite challenging. Over ten years ago econ supplied a plant to a salt mine in eastern Germany. The plant uses econ’s unique batch-wise working mixing technology to ensure a homogenous and non-sticky waste. It has a throughput capacity in excess of 50 t/h.

In the beginning it appeared to be impossible to obtain the necessary results in the light of that more than 100 different waste streams had to be treated by the unit. Extensive pilot tests were carried out before agreeing on the mixer design and size. One of the additional requirements was that no H2 emissions from the reactive wastes are allowed once the waste-mix was discharged. 
Finally a batch-wise working 10 m3 single shaft mixer unit in custom-made design was chosen to deal with fly ashes, dust, WWT sludge, car shredder residues, contaminated soils, etc. So far more than 1.500.000 tons of hazardous waste have been stabilised by the unit, and have been safely disposed of in safe conditions 400 meters under ground.

Performance data

  • Batch-wise mixer type: HTC 10000 on load cells; with speed controlled main drive
  • Batch size: 7000 litre or 10 tons; up to 10 batches per hour
  • Feeding equipment: Silo with screw conveyors, belt conveyors, pre-screening
  • Operating conditions: 3 shifts; approx. 300 days/year
  • Output consistency: Dust-free, non-sticky, up to 40 mm grain size

Design characteristics

  • Heavy duty, customised mixing and conveying equipment
  • Input storage capacity for silo-truck delivery of dust and fly-ashes of more than 200 m3
  • Sludge and moist solids handled by wheel loader via belt feeding units
  • Separation of foreign/oversized parts by magnetic separation and sieving devices
  • Turn key delivery incl. control unit and explosion protection by automated H2 measuring
  • Exhaust air filter system provided; including feeding of collected dust into the mixer unit

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