Thermal Treatment

Disarming of emission peaks during the thermal treatment of precious metal containing residues

The process and control concept developed has been used to curb emission peaks associated with the operation of installations for the recovery of precious metals in batch mode. Compliance with the limiting values defined in the 17th Federal Immission Control Ordinance has been achieved in all investigations conducted using the pilot plant.

Summary

Incineration installations for the thermal treatment of precious metal-containing residues used to date have exceeded the limiting values for polychlorinated dibenzodioxin and –furan emissions defined in the 17th Federal Immission Control Ordinance. This is a consequence of the batch mode operation of these installations and the varying composition of residues.

In order to improve the environment-friendliness of future operations for the recovery of precious metals, technical improvements for the optimisation of the combustion process have been incorporated into a pilot plant.

Results:

  • By the modification of incineration chambers, the duration of incineration has been reduced by some 50%, thereby allowing a 50% increase in the input of residues.
  • The incorporation of an automatic gas extraction system has resulted in a significant reduction in emission peaks during the gas extraction process.
  • The recirculation of cold flue gas in the thermal post-combustion phase, in combination with the use of lambda probes for process control, has reduced NOx formation by 40 – 60%.
  • Flue gas scrubbing by the use of bag filters has been optimised by the injection of an activated carbon-bearing adsorption agent and the application of an appropriate installation control system.

Conclusion:

By the application of these measures, each of the 311 emission measurements recorded lay within the limiting values defined by the 17th Federal Immission Control Ordinance.

The resulting findings may be applied to other thermal installations using batch mode operation, such as crematoria or incinerators for household or hospital wastes.

Project Participants

Implementing Institution

C. Hafner GmbH & Co. KG

More Project Informations

Project title:  Thermal treatment of precious metal containing residues: development of a new process on a pilot-plant scale

Project number:  1471060

Project period:  01.08.1996 – 31.12.1999

Project contact:

Udo Demant

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Source: German National Library of Science and Technology Hannover (TIB)