Abstract
In addition to the blast furnace converter route, electric steel production in the electric arc furnace (EAF) is one of the two main production routes for crude steel. In 2019, the global share of crude steel produced via the electric steel route was 28%, which in numbers is 517 million metric tons of crude steel. The production and processing of steel leads to the output of a variety of by-products, such as dusts, fines, sludges and scales. At the moment, 10–67% of these by-products are landfilled and not recycled. These by-products contain metal oxides and minerals including iron oxide, zinc oxide, magnesia or alumina. Apart from the wasted valuable materials, the restriction of landfill space and stricter environmental laws are additional motivations to avoid landfill. The aim of the Fines2EAF project, funded by the European Research Fund for Coal and Steel, is to develop a low-cost and flexible solution for the recycling of fines, dusts, slags and scales from electric steel production. During this project, an easy, on-site solution for the agglomeration of fine by-products from steel production has to be developed from lab scale to pilot production for industrial tests in steel plants. The solution is based on the stamp press as the central element of the agglomeration process. The stamp press provides the benefit of being easily adapted to different raw materials and different pressing parameters, such as pressing-force and -speed, or mold geometry. Further benefits are that the stamp press process requires less binding material than the pelletizing process, and that no drying process is required as is the case with the pelletizing process. Before advancing the agglomeration of by-products via stamp press to an industrial scale, different material recipes are produced in lab-scale experiments and the finished agglomerates are tested for their use as secondary raw materials in the EAF. Therefore, the tests focus on the chemical and thermal behavior of the agglomerates. Chemical behavior, volatilization and reduction behavior of the agglomerates were investigated by differential thermogravimetric analysis combined with mass spectroscopy (TGA-MS). In addition, two melts with different agglomerates are carried out in a technical-scale electric arc furnace to increase the sample size.
Highlights
The agglomeration of residues into briquettes is one way to handle the challenge of reducing the amount of material disposed in landfill and the amount of primary raw materials
The residues that are agglomerated in this work are produced during different steps of the electric steel production process chain or sometimes even originate from other manufacturing processes, for instance the grinding sludge is a residue of a local bearing manufacturer located next to the steel plant
thermogravimetric analysis combined with mass spectroscopy (TGA-MS) tests combined with thermogravimetric experiments give detailed carried out in a furnace allowing for a larger sample size, which gives a large enough sample for further information about the chemical behavior of the briquettes at high temperatures
Summary
The agglomeration of residues into briquettes is one way to handle the challenge of reducing the amount of material disposed in landfill and the amount of primary raw materials. During the production of steel by the electric arc furnace (EAF) route different types of by-products occur. Three European steel plants are participating in the project to find a low-cost and flexible solution to recycle their residues/by-products internally. The adjustable press force, pressing speed and mold size as well as grain size flexibility are beneficial properties of the stamp press for the agglomeration of the different by-products of the steel plants. Another benefit is that the stamp press does not require an additional drying process, as is the case with the pelletizing process [20,21]. An economical and environmental evaluation of the agglomeration process is not part of this work and will be part of a separate work
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