OXYFINES Technique for Upgrading Zinc Containing Blast Furnace Sludge—Part 1: Pilot Trials

Transformation behavior of hazardous jarosite into recyclable hematite in a solution with high concentrations of K+ and Na. Sci Rep 2024;14:13949. [PMID: 38886494 PMCID: PMC11183046 DOI: 10.1038/s41598-024-64502-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

Iron in the leaching solution with high K+ and Na+ concentrations was usually precipitated as the typical hazardous and toxic jarosite residues. However, this method of treatment has been greatly restricted by increasingly strict environmental regulations. Here we propose that iron can be precipitated from the solution with high K+ and Na+ concentrations as recyclable hematite products by adjusting the concentration ratio of sodium and potassium ions in the solution. The transformation behavior of jarosite into hematite in high concentration potassium ion and sodium ion solution was explained based on collision theory. The results indicated that in instances where the concentration ratio of Na+/K+ is ≥ 4:1, the iron present in the solution can be effectively precipitated as a recyclable hematite product, as opposed to forming the conventional hazardous jarosite residue, even under conditions where the potassium ion concentration reaches levels as high as 4 g/L. On the other hand, thermodynamic and molecular dynamics simulations indicate that at a temperature of 185 °C, the decomposition transformation of Na-jarosite (32.64 kJ and 7.25 eV) is more energetically advantageous compared to that of K-jarosite (61.07 kJ and 15.31 eV). The results were verified by the leaching solution from smelting industry. The iron content in the residues is above 58%, the sulfur content is below 4%, the zinc content is below 1%, and the total iron concentration in the supernatant is about 4 g/L, reaching the production index of the smelting industry. The green, environmentally friendly, and recyclable separation of iron in a solution with high concentrations of potassium and sodium ions is achieved, which is of great significance for the treatment of iron-containing solution and wastewater in the chemical industry and metallurgy fields.

Suitability of Auger Pressing Briquettes for Blast Furnace Use Based on Laboratory Tests

Briquetting is a process in which fine materials unsuitable for use as such are agglomerated to achieve a larger particle size. Auger pressing is a novel briquetting method to efficiently improve the recycling of by-products from iron and steelmaking. The high-temperature properties of auger pressing briquettes mainly consisting of blast furnace sludge and mill scale were evaluated. The aim was to determine the suitability of the briquettes for blast furnace (BF) ironmaking by studying the reduction, swelling, and cracking behavior using a laboratory-scale furnace. The blast furnace simulator (BFS) capable of performing non-isothermal reduction experiments with changing gas compositions was used to simulate the different stages of reduction up to 1100 °C in an atmosphere with N2, CO, and CO2 gases. A commercial olivine pellet and a conventional industrial BF briquette were used as reference samples. The sample weight losses were monitored by thermogravimetry, swelling as a change in the volume, and cracking by visual inspection. The samples were analyzed using microscopes and an elemental analyzer. Based on the BFS experiments, the briquettes proved to be a promising raw material for BF use. They were of a self-reducing quality due to their carbon content and showed reduction to metallic iron faster compared to the reference samples. The swelling was slight, and despite the minor cracking the structure of the briquettes did not degrade.

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

A highly effective method of the processing of steelmaking dust in an arc-resistant furnace has been presented. The aim of the research was to investigate the possibility of processing steelmaking dust in terms of waste minimization and selective recovery of valuable components. For this purpose, an electric arc resistance furnace was used. Granulated steelmaking dust with reducer (coal dust) was the input material. The products of the process are zinc oxide, iron alloy and slag, with properties meeting high ecological requirements. The technology does not generate solid waste. Zinc recovery is over 99% and iron recovery over 98%. The content of heavy metals (Zn + Pb + Cu) in glassy slag is below 0.2%, which ensures very low leachability.

OXYFINES Technique for Upgrading Zinc Containing Blast Furnace Sludge—Part 2: System Analysis

Integrating novel technology in production systems for the upgrading and further use of residual materials is a potential way of improving the resource efficiency. Assessing technology integration prospects, by performing system analysis, assists in the forecasting of effects and opportunities for different concepts. Based on pilot trials results, using Linde’s OXYFINES technique for upgrading zinc containing blast furnace sludge, a system analysis was performed on the prospects of integrating an OXYFINES concept in an iron and steel production route. The calculations were made based on one option for a full-scale OXYFINES concept for indicating the effects on the blast furnace zinc load, raw material consumption, energy use and carbon dioxide emissions from using the OXYFINES sinter product as a raw material in blast furnace ironmaking or in the basic oxygen furnace steelmaking. The summarised system analysis results showed that the most advantageous metallurgical, environmental, and economic potential was realised in the calculations of using the sinter in the basic oxygen furnace. However, the sinter was found as well suitable for use in the blast furnace when considering mainly the metallurgical and the economic effects.