Investigation on the Chemical and Thermal Behavior of Recycling Agglomerates from EAF by-Products

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.

Suitability of Self‐Reducing and Slag‐Forming Briquettes for Electric Arc Furnace Use Based on Laboratory Tests

“…The combustion behavior of the briquettes was investigated through the analysis of off-gases, and it was concluded that the CO formation rate was relatively high in biochar briquettes. Willms et al [44] conducted pilot-scale trials using direct current electric arc furnace with a volume of 45 L to assess the dissolution behavior of briquettes in melt pool by chemically analyzing changes taking place in slag and steel melt phases. Takano et al [45] evaluated the metallic yield of briquettes by charging 1 kg of agglomerates into a 2.8 kg of Fe-C liquid melted and kept at 1500 C and then weighing the metal after solidification.…”

“…At a preprocessing stage, as-received side stream materials were crushed and sieved if necessary to obtain a particle size that is less than 4 mm, a size which was empirically decided. [44] As-received ladle slag_1, for example, contained large chunks that were not suitable for particle size distribution (PSD) analysis. To determine PSD of the material, two techniques were used.…”

High-Performance Method of Recovery of Metals from EAF Dust—Processing without Solid Waste

“…The reductor batch is treated at temperatures above 1200 • C. The diffusion of oxygen from the reaction atmosphere into the material bed is limited by air flow control. Coke and CO (from partial oxidation of carbon) reduce zinc oxide and zinc ferrite to zinc metal [8,[11][12][13][14][15]. Zinc enters the gas phase and is oxidised in the gas stream to ZnO, which is collected on bag filters.…”

Determination of the Chemical, Physical and Mechanical Characteristics of Electric Arc Furnace Slags and Environmental Evaluation of the Process for Their Utilization as an Aggregate in Bituminous Mixtures

“…The life cycle analysis of the electric arc furnace slags was performed with the software SimaPro. Additionally, the physical, chemical [ 30 ] and mechanical tests established by the regulations for materials that conform the bituminous mixtures were carried out. The results reflected a clear reduction in the environmental impact by using this industrial by-product, as well as the presence of physical, chemical and mechanical properties suitable for using it in bituminous mixtures.…”