A highly developed circular economy i.e. a closure of material cycles is one of the most important columns for a sustainable metallurgical industry. Residues from ferrous and nonferrous metal production processes represent secondary resources with considerable amounts of valuable materials. Therefore, the focus is on a development and operation of processes to reuse the residues. The benefits of recycling technologies are a reduced demand of primary resources and landfill volume. Furthermore, economic savings can be generated for plant operators.
In the current Project 1.3, treatment and recycling concepts for residues from the ferrous and nonferrous industry should be further developed focusing on a recovery of valuable metals and on a reutilization of the residues within existing processes. Beside the process development itself, bulk characteristics of fine-grained residues as well as their behavior during agglomeration are of interest.
Objectives and Motivation
- Concept for a RecoDust module for the treatment of LD dust with a throughput of 1,000 kg/h
- Fine-grained injectable secondary raw material mixtures and stable agglomerates for the copper refining process
- Concept for the treatment of copper containing secondary raw materials for the removal of undesired elements and impurities
- Influence of the bulk material characteristics of metallurgical dusts on the storage and conveying behavior
The planned methodology contains theoretical activities (literature studies, CFD simulations) as well as comprehensive experimental campaigns in lab- and pilot-scale. LD dust can consist of up to 15 wt.-% zinc and more than 50 wt.-% iron. The pyrometallurgical RecoDust process was developed to recover these metals. Within the current Project 1.3, experimental melting campaigns at the Flash reactor pilot plant will be executed. Accompanying CFD simulations should support the design of the RecoDust process components for a LD dust throughput of 1,000 kg/h. The products generated during the RecoDust process (zinc oxide dust, iron-rich slag) will be analysed and evaluated in terms of their further utilization.
Beside LD dust, further process dusts are in the focus of Project 1.3. residues from waste gas cleaning systems from sinter plants, blast furnaces and electric arc furnaces (EAF) will be analysed in lab-scale with an annular shear cell regarding their flow characteristics and their time-dependent coagulation. Further parameters being relevant for the flowability such as angle of repose, bulk density and the particle grain size distribution will be measures. The obtained data will be analysed regarding possible relations and correlations.
Dusts from a sinter plant gas cleaning system will be leached in lab scale tests. The focus is on a characterization of the remaining solid residue regarding its suitability for a recycling into the sinter process. Beside this, the leachate will be analysed regarding further necessary treatment.
To quantify the influence of EAF dust on the properties of agglomerates as mixtures containing different residue types with and without EAF dust, agglomerate strength will be determined with varying process parameters of the agglomeration step.
Circular economy is also important within the nonferrous metallurgy. Secondary raw materials for the copper refining process often contain undesired elements and must be treated before being used. A treatment concept should be developed, whereas an accompanying literature research should provide the necessary theoretical input. The secondary raw materials should be agglomerated on the one hand. On the other hand, the activities are focused on a generation of fine-grained material mixtures, which can be injected into a copper refining furnace. Results from lab-scale tests regarding agglomerate strength and the storage and conveying behavior of fine-grained materials respectively serve as basis for a concept up-scaling as well as for planned experimental tests at the real refining furnace.
Results and application
At the end of the current Project 1.3, process concepts should be available for a recycling and utilization of fine-grained residues from metallurgical plants of the ferrous and nonferrous industry. These concepts should contribute to an increased residual efficiency regarding circular economy (closure of material cycles).
More precisely, a conceptual design of an industrial RecoDust module for the treatment of LD dust should be provided with a throughput of 1,000 kg/h.
Furthermore, an improved design of components for residual handling coming from waste gas cleaning plants is expected. This should lead to reduced safety risks regarding storage and transport. A broader knowledge base in terms of leaching the residues of a sinter waste gas cleaning plant will give support to sinter plant operators to design such a leaching system more easily. Finally, a better understanding regarding the influence of EAF dusts in mixtures for a residue briquetting will represent the base for an EAF dust recycling via the agglomeration route.
A recipe of copper containing secondary raw materials should be developed, which induces an increased strength level with a reduced hardening time during the briquetting process. These agglomerates should be useable in the copper refining process. Beside this, a fine-grained material mixture for a trouble-free injection under certain copper refining furnace operation is expected. This also includes all parameters, which describe the pneumatic transport behavior. Beside this, a feasibility study for a removal of impurities from copper containing secondary materials should be generated.