Mixing and Agglomeration of Shredder Fines and Flue Dust

Industrial processes are inevitably associated with generating fine-grained particulate matter. Such fine-grained residues rarely find re-entry into industrial value chains; typically they are disposed and become an environmental burden. Prominent examples are dusts from mineral processing, degraded end-of-life fibers, or micro plastic entering the natural environment. The project FINEST will process different residues in an optimized manner to generate value and to minimize hazards. FINEST will design high-value products and inert residues. Material assay, beneficial material mixing and logistic concepts will provide ideal opportunities to transform hazardous end of life products to inert residues and to products generating economic value.
Economic and ecological assessment of waste management concepts will provide op-opportunities to create value by decreased disposal costs. The project assembles a well-tailored network of industry associations, industry companies, SMEs, governmental and non-governmental institutions. Associated institutions will provide the capability to transfer FINEST results to the relevant industrial sectors and potential consumers. The appendant Research School will educate a next generation of experts for leadership positions in industry and academia. A transfer design will consider the transfer of knowledge through careers. Young postgraduate colleagues will accordingly receive tailored education in establishing technology transfer concepts and are expected to conduct internships in the course of their doctoral studentship. A central transfer desk will provide organized knowledge transfer to industry clusters and associations in order to promote joint position papers and to suggest market-shaping policies. Individual TTOs have stated their full support for the screening and exploitation of evolving IP within the sub-projects. FINEST represents an ideal combination of scientific excellence and tailored networking with an application-oriented education of the next generation of leadership personnel for the industry and academia. The project offers a well-structured approach to reduce uncertainties for an actual application of developed technologies and is ready to increase the degree of circularity in the economy by transferring its research, and to contribute to more sustainable value chains.
Fine-grained solid particles from various industrial sources, which would otherwise be discarded, should ideally be processed to valuable products or inert residues. Among others, a) shredder fines from electronics and end-of-life vehicles, and b) flue dusts from non-ferrous metallurgical processes are of timely interest. They contain valuable residuals, such as metals, that can be returned to the industrial cycle instead of being landfilled. This is one aim of the Helmholtz project FINEST in which this work is embedded. In this work, mixing and agglomeration of such particles with a size below 1 mm are investigated for further use in the metallurgical industry. Different particle sizes, shapes and densities are considered, as well as varying moisture content. Most relevant product parameters are the mixture’s homogeneity, agglomerate size and porosity. A strong focus is on the rheological behavior of the bulk goods. A continuum model will be used to simulate mixing and prospectively granulation in a cylindrical bladed mixer. The three phases, namely shredder fines, flue dust and interparticle liquid will be modelled using Computational Fluid Dynamics, adding in a Convection-Dispersion-Segregation-Model for microprocesses of mixing. The latter will introduce a Segregation-Term specifically for density differences among component. We present an experimental setup and methods for the aforementioned investigations. The process is observed experimentally using camera imaging technique and µCT. From the µCT images a mixing index is acquired. Using rapid prototyping mixing and agglomeration equipment can be adapted easily and varied for parameter studies. The results will contribute to improved mixing and agglomeration processes for efficient recycling of fine particles as well as improved understanding of mixing in many other fields, such as pharmaceuticals, construction material and food industry.