Since the European Union defined ambitious CO2 emission targets, low-carbon-emission alternatives to the widespread integrated blast furnace (BF)—basic oxygen furnace (BOF) steelmaking strategy—are demanded. Direct reduction (DR) with natural gas as the reducing agent, already an industrially applied technology, is such an alternative. Consequently, the melting behavior of its intermediate product, i.e., direct reduced iron (DRI), in either an electric arc furnace (EAF) or a submerged arc furnace (SAF), is of great interest. Based on the conditions in these aggregates, a test series to experimentally simulate the first few seconds after charging DRI was defined.

The tests were carried out on an experimental stand designed and built by the authors of this paper. The stand reproduces on a scale of 1:2 a drum made up of a double-axis horizontal mixer. The stand had the possibility to change the value of the attack angle of the mixing blades, corresponding to the following values: 30, 45, and 60 degrees. The results of the tests established the dependence between the type of material and the wear rate of the blades as well as the influence exerted by the angle of attack on the wear of the mixing blades. It was shown that when the inclination angle of the blade relative to the shaft axis increases, the cumulative mass loss decreases, with values between 43% and 55.83%, as a function of the quality of blade material.

In concrete industry production, mixers play a crucial role by facilitating the efficient and consistent blending of various constituents to create high-quality concrete. Because the mixers in the concrete industry work in conditions characterized by abrasive and erosive loadings, the authors of this paper tried to establish a dependence between the quality of the material from which the mixing elements are made and their wear resistance. Three types of cast irons alloyed with chromium, specific to the construction of mixing blades, were used in this research.

To select the best briquettes, pre-established set points were used based on the scientific literature. Within this framework, only two treatments—out of a total of 52—met all the requirements of eligibility. In the two types of briquettes, the binder of solid silicate (5.00 and 7.50%) was produced with 15.00% of water. The briquettes have the following characteristics: apparent density: 1165 kg/m3 and 1247 kg/m3 respectively, porosity: 46.2% and 46.0%; shatter strength (1.50 m): 99.3% and 98.8%; and resistance to thermal degradation: 81.2% and 82.5%.

Characterization of this waste was performed and the briquettes were produced without and with binders (Portland cement, hydrated lime, and sodium silicate), in accordance with the proportion of binder (2.50%; 5.00%; 7.50% and 10.00%). These self-reducing briquettes were tested for apparent density, porosity, shatter strength and resistance to hot degradation.

Self-reducing briquettes made with waste (silica fume, iron ore and charcoal fines) from the FeSi75 industry were studied. The objective was to determine if these briquettes could be used as a complementary load in submerged arc furnaces (SAF).

The results demonstrated that during a start-up period of 90 days, the average ammonium removal efficiency and the sulfate conversion efficiency of the reactor containing the sponge iron were 4.42% and 8.37% higher than those of the reactor without the sponge iron. The addition of the sponge iron shortens the start-up time of this greenhouse gas-free denitrification process and reduces future costs in practical applications. The removal of total nitrogen (TN) significantly increased after adding organic carbon sources and then declined sharply, while the most considerable reduction of ammonium removal efficiency from 98.4% to 30.5% was observed with adding phenol.

The typical characteristics of wastewater produced from seafood, chemical, textile, and paper industries are that it contains ammonia, sulfate, and a certain amount of chemical oxygen demand (COD). The sulfate-reducing ammonium oxidation process is a biochemical reaction that allows both ammonia and sulfate removal, but its low growth rate and harsh reaction conditions limit its practical application. Due to the adsorption properties of the iron sponge and its robust structure, it provides a suitable living environment for microorganisms.

Four cases were compared: carbon-free and carbon-containing DRI from DR-grade pellets as well as fines from a fluidized bed reactor were melted batch-wise. A slag layer’s influence was investigated using DRI from the BF-grade pellets and the continuous addition of slag-forming oxides. While carbon-free materials show a porous structure with gangue entrapments, the carburized DRI forms a dense regulus with the oxides collected on top. The test with slag-forming oxides demonstrates the mixing effect of the arc’s electromagnetic forces. The cross-section shows a steel melt framed by a slag layer. These experiments match the past work in that carburized DRI is preferable, and material feed to the hotspot is critical for the EAF operation.

Hydrogen-based direct reduction is a promising technology for CO2 lean steelmaking. The electric arc furnace is the most relevant aggregate for processing direct reduced iron (DRI). As DRI is usually added into the arc, the behavior in this area is of great interest. A laboratory-scale hydrogen plasma smelting reduction (HPSR) reactor was used to analyze that under inert conditions.