Treating fly ash produced during waste incineration is a multi-step process. First, it is mixed with the flue gas cleaning washing water, which leads to metals and salts being released from the ash. A BHS belt filter then filters the resulting suspension. After a further wash, the solid that remains is purified ash.
The process water used in the first step is treated further to recover both salts and metals. After the salt water has been separated, a BHS rubber belt filter with continuous vacuum filtration filters the suspension; the metals are left behind as solids. The process water can now be returned to the process.
This means that this new process (HALOSEP) for treating fly ash has two advantages: On the one hand, recyclable materials are recovered from the ashes, and on the other hand, the ashes are upgraded from hazardous waste. In the future, the processing should go so far that they can be used directly as an additive for building materials. BHS technology is also used in related processes, such as FLUWA.
BHS-Sonthofen not only supplied the technology, which needs to be robust and resistant to corrosion for this application, but also impressed the customer by the close cooperation in the preliminary stages above all: The filters were perfectly adapted to the new process following laboratory-scale tests at the customer’s site. The commissioning of the complete plant took place in a Vestforbraending waste-to-energy plant in early 2021.