Adding value through innovative recycling technologies

Around 200,000 tonnes of metal sludge and 950,000 tonnes of metal powder are produced in metal production and processing each year in Germany alone.

These metallic by-products are produced, for example, during grinding, rolling and milling. High-quality materials such as stainless steel and high-speed steel (HSS) are processed. Consequently, the resulting waste streams also still contain valuable metals. However, oils, cooling lubricants or emulsions are also used in the grinding process. As a result, the metallic production waste is mostly contaminated with oil and water, which in turn makes it difficult to recover the metals. Conventional processing methods are therefore usually unable to fully recover the metals, which is why this is often referred to as downcycling. The loss of quality of the materials means that reprocessing is rarely economically efficient for companies, so that a large part of the production waste is landfilled or incinerated at a cost.

This issue has been the basis for CRONIMET Envirotec GmbH. The company based in Bitterfeld, Germany has developed an innovative recycling process that enables the complete and sustainable reprocessing of metallic by-products without any loss of quality.

The following example shows how innovative recycling technologies can lower disposal and raw material costs while benefiting the environment.

Starting point: HSS grinding sludge

A tool producing company from Germany generates HSS containing waste. One of its main fields of activity is the wet grinding service. This produces about 1,000 tonnes of grinding sludge per year. The grinding sludge is declared as hazardous waste because of its oil content of about 20 per cent. In the past, this used to be thermally processed or incinerated. Since 2017, CRONIMET Envirotec has been recycling the grinding sludge, which allows the company to economize its disposal costs and reimburses it for the material.

Recycling solution for the recovery of HSS

CRONIMET Envirotec recycles metallic waste such as filter dusts, filter cakes, mill scale as well as grinding sludge in two unique plants. The company's vacuum distillation plant allows the recycling of raw materials in combination with oil and water. Solids and liquids are separated from each other in two vacuum dryers. This form of recycling is a particularly energy-efficient process, as the absence of oxygen in the vacuum also prevents oxidation of the metals, i.e. the chemical composition remains unchanged and the quality of the material is maintained. Furthermore, the inert atmosphere reduces the need for an expensive reduction when reusing many metals.

After processing, oil, distilled water and pure metal powder are afforded in separate fractions. Through the process, the waste loses its declaration as hazardous and is no longer subject to monitoring.

About 750 tonnes of HSS powder can be recovered from the 1,000 tonnes of grinding sludge, which contain among other substances 39 tonnes of tungsten and 34 tonnes of molybdenum. The powder is then pressed into briquettes. An organic binder guarantees high solidity and does not change the chemical composition of the HSS material.

The briquettes produced in this way can then be melted down similar to scrap. They can thus be used directly in the production of new HSS which closes the raw material cycle.

Beneficial for companies and the environment alike

The cooperation with CRONIMET Envirotec established significant financial added value for the tool producer. In addition, the recycling solution decreases the company's waste balance results. Valuable raw materials, such as tungsten, molybdenum and chrome can be recovered instead of being disposed of in landfills or incineration plants. In this way, the need for primary raw materials can be reduced and a previous hazardous waste is turned into a resource again.

By closing the raw material cycle, the CRONIMET Envirotec process represents a sustainable innovation in contrast to existing disposal routes. The return of 750 tonnes of HSS material to the production cycle also contributes to a CO2 saving of at least 1,250 tonnes of CO2 compared to the extraction of primary raw materials.