Hidden treasure, zero waste
An enhanced separation system for a cutting-edge recycling plant
The Brantner Environment Group GmbH is a waste management company headquartered in Austria and operating in Central and Eastern Europe. It runs the first plant in Europe to use a special process in order to improve the results of the recycling process by maximizing the recovery rate of valuable materials and minimizing/eliminating the amount of remaining waste.
Improving the recycling process from waste incineration
A significant amount of waste ends up in waste incineration plants, and the remains left after incineration are known as slag. This slag is processed using the Brantner Wet Slag (BWS) method, which removes and washes the valuable metals from the waste incineration slag. Salts and fine components are then washed out of the slag and pumped into an ANDRITZ water processing system together with the wash water. The muddy process water is drained in an ANDRITZ container plant using a specially modified decanter centrifuge. The main challenge was to determine the best operating conditions and set-up for the decanter centrifuge within a very wide and constantly changing range of wash water qualities.
A decanter centrifuge designed to work around the clock
ANDRITZ SEPARATION specialists worked together to find the ideal solution for this innovative urban mining project, handling everything from the concept to laboratory tests and onsite testing with a mobile container plant, through to producing and installing the final, customized dewatering plant. An ANDRITZ decanter centrifuge D was modified to allow for continuous operation based on very different solids inlet concentrate and cleaning the circulating water. The high separation quality achieved by the decanter centrifuge means that there is no contaminated water requiring disposal, while the consumption of fresh water has been reduced considerably by applying the ANDRITZ process. Besides the decanter centrifuge having to operate with highly variable wash water quality, abrasion presented a specific challenge on this application.
ANDRITZ SEPARATION managed to overcome this by developing special wear protection for specific decanter parts (inlet feed box, outlet nozzles), based on its decades of experience in abrasive applications in, for example, mining and minerals. 2,500 kg/h of solids are continuously fed into the ANDRITZ container plant, controlled via a solids measurement device. This guarantees continuous operation with automatic adjustment of the general decanter parameters. The processed and cleaned ash is dewatered to a dry matter content of around 50% and can be transported on a wheel loader.
Output guarantees met and surpassed
The ANDRITZ decanter centrifuge has been in use since summer 2015 and has meant that the whole recycling process is now 100% closed. Before installing the decanter centrifuge, the wash water was only treated in a sedimentation tank and the slag was deposited at the Brantner site, whereas now 100% of the urban waste is reused – first by incineration producing heat and electrical energy), then by mining the valuable minerals (copper, aluminum, etc…) from the ash, and finally by dewatering the remaining wash water to produce a material that can be used in road construction in certain countries (official certificates missing from government).
Having ANDRITZ SEPARATION as a local supplier in Austria was another benefit for Brantner as this ensured the
availablity and proximity of services.
What’s more, the solution has delivered reduced down-time and excellent reliability thanks to continuous operation, coupled with low energy consumption and low operating costs. The highest quality of the end products is guaranteed thanks to the closed and self-venting system.