Kinetic studies of Ni(II) ions adsorption from aqueous solutions using the blast furnace slag (BF slag)

In this work, we used the blast furnace slag for the nickel adsorption in aqueous solution. The physico-chemical characterization showed that the BF slag consists mainly of the silica, lime, and alumina. The specific surface area of the BF slag grains is of the order of 275.8 m2/g. The optimum elimination parameters are the agitation speed 200 rpm, pH 4.5, the adsorption temperature 20 °C, and particle size between 200 and 500 μm. The adsorption capacity and the efficiency of nickel removal by the BF slag after 90 min of agitation are respectively 53.58 mg/g and 92.7%.The experimental adsorption data showed that the pseudo-second-order model was the most appropriate in nickel adsorption kinetics; the adsorption isotherm could be described well by the Langmuir model indicating that the process was monolayer, and intra-particle diffusion is not the sole mechanism involved in this process. Thermodynamic study showed that the Ni(II) elimination by BF slag process is spontaneous, exothermic, and less entropic.

Effect of MgO Content on Heat Capacity of Synthetic BF Slag and Heat Release Behavior during Cooling Process

The differential scanning calorimetry (DSC) sapphire analysis was used to measure the specific heat capacity of the BF (BF) slag and observe the CaO-SiO2-MgO-Al2O3-TiO2 5-element slag system with the binary basicity fixed at 1.17. The specific heat capacity of the BF slag and the cooling heat distribution were obtained during the cooling process when the MgO content changing from 7% to 11%. The results showed that the heat released of BF slag was more than 1.2 GJ/ton during the cooling process from 1400 °C to 35 °C, of which the sensible heat was dominant. At MgO content of 9%, the latent heat of crystallization is maximum. The cooling and heat release law of BF slag is directly associated with the phase precipitated in slag cooling and micromorphology.

The Quantitative Effect of Blast Furnace Slag Composition and Temperature on the Kinetics of Potassium Evaporation

Increased in-plant recycling and lower quality raw material in terms of alkali content drive the alkali load in the blast furnace (BF) to higher levels. Excessive load of alkalis, primarily potassium, has several negative effects on the BF operation, which necessitates means to control the removal of potassium from the BF. One method to improve the removal is by increasing the potassium retention in the slag, which is controlled by the evaporation kinetics of potassium. Although several authors have studied factors affecting the evaporation rate, none of these studies have quantitatively investigated the effect of these parameters and attempted to relate these effects to slags from the industry. In the present work, a full-factorial design of experiments with three factors (B2 basicity, MgO content, and temperature) was performed, studying the evaporation of potassium from synthetic BF slag. The results suggested that multiple linear regression is suitable to describe the evaporation kinetics of potassium within the boundaries of the design of experiments. However, extrapolating to industrial slags of different compositions and additional slag components is best performed utilizing the corrected optical basicity. The corrected optical basicity showed a linear relation to the evaporation kinetics of potassium, which was related to the correlation between diffusivity and corrected optical basicity.

Influence of polyvinyl alcohol–glutaraldehyde on properties of thermal insulation pipe from blast furnace slag fiber

The development of an environmentally friendly binder can immensely benefit and promote the BF slag fiber industry. Accordingly, in this study, fiber insulation pipes were prepared using water glass, polyvinyl alcohol (PVA), and PVA–glutaraldehyde (GA); moreover, their bulk density, moisture absorption capacity, and thermal conductivity coefficient were measured and compared. The results demonstrated that the values of these three parameters depend on the binder concentration and dosage under certain fiber quality, pipe sizes, and manufacturing process conditions. The best binder composition was proven to be that of PVA–GA, prepared using 3 wt% PVA and 5 wt% GA herein, which facilitated reduction in the bulk density and improvement of the waterproof properties and insulation performance of the slag fiber pipes.

Preparation and performance analysis of gas-quenched steel slag beads

The low utilization rate of steel slag in China has exposed serious environmental and social problems. In the present work, the basic oxygen furnace (BOF) slag was modified by blast furnace (BF) slag and then beaded by the means of gas quenching. The gas-quenching rate, bead formation rate, physical properties, microscopic characteristics and free lime (f-CaO) of gas-quenched slag beads were analyzed to broaden the utilization of BOF slag. The results show that the more BF slag is added, the higher the gas-quenching rate is, and the lower the bead formation rate becomes. When no BF slag is added, the beads are mainly composed of magnetite, limonite and melilite. After BF slag is added, a large amount of glass phase and a little amount of Ca2SiO4 and MgO are found in beads. The content of f-CaO beads decreases after the modified slag is gas quenched at high temperature. Moreover, the more BF slag is added, the higher the elimination rate of f-CaO becomes. Considering the industry standard of steel slag sand in China as well as the gas-quenching rate, physical and chemical properties, the gas-quenched steel slag beads with 5 and 15% BF slag better meet the medium sand standard, which can be used as fine aggregate.

Study of blast furnace heat filterability through coke filling

Increase of gas permeability of burden materials column lower part is one of the way of blast furnace heat intensification. Filterability of intermediate slag through coke filling determines the gas permeability of the lower zone and the blast furnace heat running. To study the filterability a methodology was elaborated and implemented, which enabled to estimate reliably the iron ore raw materials behavior in the blast furnace at high temperatures. By laboratory studies influence on the filterability of BF slag melt was determined, when MgO, MnO and CaO adding to the burden, depending on the oxides mineralogical composition. The positive influence of magnesium oxide on the slag filterability has an extreme character, at that the sinter basicity has a considerable influence. The mineral form of magnesium-containing additives introduced into the burden substantially influenced the filterability on heat products in blast furnace. Replace ofsiderite and dolomite by other magnesium-containing materials facilitates to improving of slag filterability through coke filling. Additional input of manganese in the form of manganese limestone or manganese-containing ferritic-calcium flux is an effective mean to improve filterability of sinter smelting products through coke filling. Transfer to hot metal smelting from fluxed pellets and sinter will facilitate heat products filterabilityincrease thanks to close physical andchemical properties of BF burden components in respect of smelting and slag filtering through coke filling.

Estimation of application efficiency of “Flumag M” magnesia flux in agglomeration and BF production.

To decrease viscosity of BF slag and improve its desulfurization ability during hot metal production a magnesia oxide is used, which is introduced into a blast furnace, as a rule, within iron ore sinter, as well as in the form of a fluxing additive. Dolomite, sometimes iron ore materials with increased magnesia content (for example, Kovdor concentrate, raw or roasted Bakal siderite) as well as magnesia-contained wastes, most often BOF slag, are usually used as a main source of magnesia oxide during iron ore sinter production. Brucite, which is widely used abroad, mainly in Japan during iron ore sinter production, is a very prospective magnesia flux. However, brucite was never used in sinter production in Russia. Main parameters and efficiency of its application were obtained under Japan raw materials conditions. However sinter chemical and mineral compositions at Russian and Japanese sinter plants considerably differ. In this connection studies on influence of the magnesia flux “Flumag M”, which is identical by its composition to brucite, on the process parameters of sinter burden sintering and pellets production were carried out. The estimation of application efficiency of “Flumag M” magnesia flux was made during typical sintering of NLMK sinter burden. It was determined, that partial and complete substitution of dolomite by the “Flumag M” magnesia flux in the NLMK sinter burden results in an increase of specific productivity of sintering process by 10–20% (comparative) and the sinter strength by 3–5% (comparative) correspondently. Laboratory experiments on “Flumag M” magnesia flux application, carried out in STI NITU “MISiS”, showed, that raw pellets with magnesia flux additives have higher compressive strength comparing with the pellets having dolomite additives. Impact strength and abrasion strength of roasted pellets is higher, comparing with those with dolomite. Optimal content of “Flumag M” flux in the pellets burden is 2%. The application of “Flumag M” magnesia flux enables to remove burden from the burden and increase strength of roasted pellets.

Preparation of Non-Fluorine Glass Ceramics from Modified Molten Blast Furnace Slag

Non-fluorine glass ceramics were successfully prepared from modified molten blast furnace (BF) slag. Quartz sand and Al2O3 were added as modification material. Fe2O3, TiO2, and ZrO2 were added as nucleation agents. The thermal properties of the modified BF slag and the structure of glass ceramics were investigated by differential scanning calorimetry (DSC), scanning electron microscope (SEM) and X-ray diffraction analysis (XRD). The results indicated that the crystallization temperature (Tp) decreased with increasing BF slag, and the glass stability index ΔT initially decreased and then increased. As BF slag increased, the growth of akermanite in glass ceramics was enhanced, while the formation of diopside was not notably effected. The micro-hardness of glass ceramics reached 1082 Hv and the flexural strength was 70 MPa when the BF slag was 74 wt. %.