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and safe recovery

and safe recovery a new melting and recycling process can separate toxic residues from contaminated metals and retain them safely in filters and slag. The process, developed by Siempelkamp of Krefeld, Germany, was originally meant for the nuclear industry to melt and recycle radioactively contaminated metallic residues from nuclear installations.

There is a tremendous need for effective ways of toxic waste disposal and recycling right across the world. Several hazardous wastes pose a significant risk to the environment and human health. A large quantity number of pipes, valves, pumps and other components that have been contaminated with mercury need to be disposed of when a crude oil and natural gas extraction plant is shut down. Approximately 640 such oil platforms operate in the North Sea, 60 of which have already been shut down. Thus, an ecologically sound disposal system was required for the disposal of sludge from these installations that is highly contaminated with radioactivity.

Extensive research revealed that this process was suitable for the recovery of the chemically contaminated metals along with the nuclear wastes. Siempelkamps developed the procedure with a melting process to separate the toxic residues for recycling and disposal. The Siempelkamp gerta plant (a large-scale plant for recycling of toxic wastes) started operating in January 1998.

The key element of the gerta plant is its advanced furnace with an exhaust hood to limit emissions. The special charging device is also connected to the exhaust. Mercury evaporates during the melting process and passes through the exhaust cover to the filter plant. Here, it undergoes three steps:

- cyclone (for separating coarse dust)

- bag filter (for separating fine dust)

- fixed bed absorber (for separating mercury).

To ensure the safe operation of the process, data pertaining to gas emissions, ambient air in the workshop, and analyses of recycled material and the residues are monitored at regular intervals. After melting, the metal is cast into the ingots. As this metal does not contain any contaminants, it can be used in the iron and steel industry. The slag can be used for road construction.

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