From Waste to Waste: Iron Blast Furnace Slag for Heavy Metal Ions Removal from Aqueous System

Blast furnace slag (BFS) is considered a cheap sorbent for the get rid of Co2+ and Pb2+ ions from an aqueous medium. The slag is characterized using X-ray diffraction (XRD), X-ray fluorescence (XRF), N2 adsorption-desorption isotherms, energy dispersive X-ray analysis (EDX), scanning electron microscopy (SEM), and zeta potential. The removal of Co2+ and Pb2+ ions was carried out using batch adsorption experiments from an aqueous medium. The influence of several variables as pH, duration, sorbent quantity, temperature, and preliminary ions concentration was considered. The isotherm, kinetic, thermodynamic, and recyclability were also conducted. The maximum uptake capacity for Co2+ and Pb2+ was 43.8 and 30.2 mg g-1 achieved at pH 6 after 60 min. contact duration. The adsorption kinetics and isotherms of BFS for Co2+ and Pb2+ fitted well to Avrami and Freundlich models, respectively. The main sorption mechanism between BFS and the metal ions was ion exchange. The regeneration of the used slag was studied for reuse many cycles. In terms of economics and scalability, the treatment with the unmodified BFS has great potentials.

CFD Simulation for Heat Transfer In Blast Furnace

Iron blast furnace is used in the metallurgical field to extract molten pig iron from its ore through a reduction mechanism. The furnace is a vertical shaft with circular cross section. It has five main parts: stack, belly, bosh, tuyeres and hearth. Amongst these regions, hearth is the most important one for the asset life of a furnace. Erosion of refractory lining of the hearth reduces the furnace’s campaign life. So it is necessary to understand the interactions occurring between the slag, molten metal and the refractories. But the severe operating conditions and very high temperature inside the hearth make it impossible to practically observe the processes taking place within it. In order to overcome this problem, the hearth is modeled by using various Computational Fluid Dynamics (CFD) soft-wares such as ANSYS Fluent, ANSYS-CFX, FLUENT for CATIA V5, ANSYS CFD-Flo etc. The numerical model is then supplied with data which are already known from practical situations as boundary conditions. Proper physical properties of the materials are also used as input. The software runs several simulations and provides us with the result that can validate the experimental observations up to the most accurate level. In this study, temperature distribution profile inside a blast furnace hearth has been shown by modeling a simple hearth with the help of ANSYS 15.0 Workbench. The model is simulated by changing some parameters and making several assumptions. The discrepancy in the calculated and the observed temperature opens up new scope for further improvement.

Oxidative Leaching of Zinc and Alkalis from Iron Blast Furnace Sludge

The sludge from a wet-off gas cleaning system of the iron blast furnace (BF) contains significant amounts of iron; however, they cannot be recycled due to their high content of zinc and alkalis. These compounds are detrimental to the optimal performance of iron and steelmaking furnaces. In this work, a comparative laboratory study to reduce zinc and alkali contained in the blast furnace sludge (BFS) is presented. The effect of leaching parameters such as oxidant (i.e., ferric ion, oxygen or ozone), aqueous solution media (i.e., 0.2 M NH4Cl, 0.2 M HCl and 0.1 M H2SO4) and temperature (i.e., 27 and 80 °C) on Zn and alkalis (Na2O and K2O) removal were studied by applying an experimental design. The results obtained show that Zn and K2O removal of 85% and 75% were achieved under the following conditions: Ozone as an oxidant agent and 0.1 M H2SO4 as an aqueous medium, temperature had no significant effect. The results are supported by thermodynamic diagrams and the possible chemical reactions are mentioned. Although the results also indicate that leaching under the above conditions dissolves up to 9% of iron, this loss is much less than leaching without the oxidizing conditions generated by the ozone. The BFS obtained from this treatment could be recirculated to the iron or steelmaking processes to recover iron values.

Environmental footprint of small-scale, historical mining and metallurgy in the Swedish boreal forest landscape: The Moshyttan blast furnace as microcosm

The history of mining and smelting and the associated pollution have been documented using lake sediments for decades, but the broader ecological implications are not well studied. We analyzed sediment profiles covering the past ~10,000 years from three lakes associated with an iron blast furnace in central Sweden, as an example of the many small-scale furnaces with historical roots in the medieval period. With a focus on long-term lake-water quality, we analyzed multiple proxies including geochemistry, pollen and charcoal, diatom composition and inferred pH, biogenic silica (bSi), visible near-infrared spectroscopy (VNIRS)-inferred lake-water total organic carbon (LW-TOC), and VNIRS-inferred sediment chlorophyll (sed-Chl). All three lakes had stable conditions during the middle Holocene (~5000 BCE to 1110 CE) typical of oligo-dystrophic lakes: pH 5.4–5.6, LW-TOC 15–18 mg L−1. The most important diatom taxa include, for example, Aulacoseira scalaris, Brachysira neoexilis, and Frustulia saxonica. From ~1150 CE, decreases in LW-TOC, bSi, and sed-Chl in all three lakes coincide with a suite of proxies indicating disturbance associated with local, small-scale agriculture, and the more widespread use of the landscape in the past (e.g. forest grazing, charcoal production). Most important was a decline in LW-TOC by 30–50% in the three lakes prior to the 20th century. In addition, the one lake (Fickeln) downstream of the smelter and main areas of cultivation experienced a shift in diatom composition (mainly increasing Asterionella formosa) and a 0.6 pH increase coinciding with increasing cereal pollen and signs of blast furnace activity. The pH did not change in the other two lakes in response to disturbance; however, these lakes show a slight increase (0.3–0.5 pH units) because of modern liming. LW-TOC has returned to background levels in the downstream lake and remains lower in the other two.