When powders with similar physical properties come together in a heterogeneous mixture, separation and recovery present a major challenge. This task is particularly interesting in terms of sustainable resource conservation and economic reuse (recycling). Hosokawa Alpine, one of the leading suppliers in the area of processing technology and film extrusion, tackled this issue through an intensive series of tests in the Process Consulting department. Since 2018, this department at Hosokawa Alpine has been applying its many years of expertise to challenges in process and plant planning and developing sophisticated solutions.
When it comes to sorting materials, engineers are confronted with special tasks, as Christian Eisenbarth, Process Consultant Technical Division at Hosokawa Alpine, explains: "If the product consists of materials with significant differences in terms of particle size and weight, the separation is easily carried out using the numerous classifier solutions in our portfolio. It becomes difficult when the materials no longer differ sufficiently, for example if a product consists of several minerals of similar fineness and weight."
While searching for solutions, Christian Eisenbarth and his team were able to determine that the key to sorting lies in classification of the product mixture. In this process, individual product fractions are produced by means of classification, which are then analysed. As a result, it is possible to assess how the individual substances accumulate and at which cut point classification is promising. Different classifiers can be tested according to the fineness. The accumulation of the individual fractions is determined in the Hosokawa Alpine laboratory by acid digestion, loss on ignition, images with the scanning electron microscope or by an external testing laboratory.
"After this preliminary investigation and the assessment of the individual fractions, we carry out further tests with the suitable pilot plant machine and can thus develop an industrial solution for our customers for their individual tasks. This means that recovery can take place in a homogeneous manner, saving landfill costs, for example," explains Christian Eisenbarth. Application examples can be found in the building materials industry, where additives are to be separated from the primary product. This is the case, for example, with cleaning batches in mortar mixers. Another application is the processing of waste from central aspiration. These separation tasks can be solved with the newly developed process.