Flotation of synthetic metal phases through the example of fine fractions of waste incineration bottom ashes


Project description

In the context of current efforts in the field of resource- and energy-efficiency, waste streams and deposits with fine-grained metals are getting more and more interesting.

Unlike the processing of metals from coarse materials, processing of fine materials from waste and other secondary sources are not investigated and process plants are not established. While the metal phases of primary minerals are known and have been investigated for many decades, the metal phases in waste streams are not completely identified, yet. These metal phases that consist out of metals, alloys and metal compounds have often no natural equivalent and are called artificial metal phases.

One example of fine grinded waste streams with artificial metal phases are incinerator bottom ashes. These ashes are processed by grinding, sieving  ferrous and non-ferrous metal separation. Today, only a processing of the fraction over 2 mm is realized in an industrial scale. At the TU Clausthak, a process for smaller particles based on selective crushing and sorting classifying has been developed. One disadvantage of this process is that the processing of the fraction below 160 µm is an unsolved problem. Only first attempts in flotation of this fraction were carried out.

The current project investigates the possibility of flotating the metals in the fine and finest fractions of incinerator bottom ash. The project is carried out in several steps. First, a mineral characterization must take place. This is done by chemical and microprobe (pictures below) analyses. When the relevant metal phases are identified, pure material of these phases must be synthesized. With this synthetic material analytics like determination of the contact angle and the zeta potential are carried out. Based on this information, flotation tests such as reagent screenings will be made. Tests will start by investigating pure fraction and will end by investigating complex generic mixtures. The last step of the project will includes transferring the investigated parameters to real incinerator bottom ashes.

Supported by:

DFG - Deutsche Forschungsgemeinschaft

Projekt number 403179546

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