Deburring, grinding or polishing by mass finishing is based on the principle that small particles are removed from the surfaces of workpieces. Abrasive media made of plastics have become increasingly common in these applications. Against the backdrop of the issue of microplastics, it is therefore essential for operators to guarantee that the micro and nanoparticles arising from the mass finishing process are not released to the environment.
The processing of workpieces by means of mass finishing is by definition a machining process, although the abraded particles are extremely small and retained in the process water. The particles come both from the – usually metallic – workpieces and from the abrasive media that today are often made of plastics. In addition to these particles, over the course of time tiny plastic particles are removed from the polyurethane coating of the work bowl, which is also subjected to abrasion during the processing.
Therefore, there are good reasons to look further into the question whether everything possible is done to prevent these microplastics from entering the environment. The particle size is commonly between a few micrometers down to the nanometer range. To rule out the risk of these particles polluting our environment, it must be guaranteed that they do not become entrained in any waters.
For both of its mass finishing processes – recirculation and through flow, Walther Trowal provides solutions that reliably ensure that no microplastics are released to the environment.
Recirculation technology: Tried and tested in numerous applications
Recirculation units have traditionally been and still are the most frequently used systems. In these units, the process water is permanently circulated within a closed system and returned to the process after passing a centrifuge or a settling tank where the solids are removed. Replacing the recirculation water at regular intervals and properly disposing of the collected sludge ensures that no micro and nanoparticles can enter the environment.
The benefits: Excellent surface properties of the workpieces achieved by means of a both economically efficient and environmentally friendly process from which no microparticles can be released to the environment.
Through-flow technology: For special applications
If different products that have to comply with exceptionally high cleanliness levels are processed or different compounds have to be used, through-flow systems are the technology of choice. An example are workpieces that have to be so clean after the mass finishing process that they are ready to be installed without any further cleaning.
After having flown through the working tank, the process water is treated in a flocculation tank followed by a filter unit. The optimized flocculants ESM and ESB supplied by Walther Trowal ensure 100 percent binding of the micro and nanoparticles in the water. The filter systems separate the sludge from the process water which is crystal-clear and of virtually drinking water quality when it leaves the treatment unit. In this condition, it can be discharged into the sewage system in line with legal requirements. The sludge containing the micro and nanoparticles is properly disposed of.
Comprehensive tests conducted by the Institute for the Environment & Energy, Technology & Analytics based in Duisburg, Germany, have shown that all of the particles – i.e. also micro and nanoplastics – are bound in the flocs and reliably separated in the filter press. For the tests, the treated, floc-containing process water was filtered through a nano screen. The particles remaining in the filter were subsequently examined by means of scanning electron microscopy. The “before – after” comparison showed that the flocculant-treated and filtered water contains no more microplastic particles.
For customers wishing to be absolutely sure that they do not release any microplastics to the environment, Walther Trowal offers the service to check the effectiveness of their flocculation systems at the company’s laboratory in Haan.
