Volatilisation Behaviour and Mechanism of Lead-Containing Slag during Physical Property Tests.

According to physical property tests of lead-containing slag, the volatilisation behaviour of lead slag will have adverse impacts on test accuracy and further affect the control of chemical reactions, solidification and removal of inclusions during smelting. To analyse the volatilisation characteristics of lead slag, in this paper, four kinds of lead slags from lead direct reduction smelting with different PbO and ZnO content are taken. thermogravimetry, ISP-TOF were used. Additionally, the changes in volatiles and slag composition and phases were analysed with XRD and ICPS, and the volatilisation reaction mechanism was discussed. The results indicated that the volatilisation of lead slag can lead to a big weight loss of about to the slag with higher PbO content. The weight loss increases with the PbO content in slag increases. The volatile corresponding to the weight loss above 900 °C is mainly PbO and less ZnO. The higher the temperature is, the stronger the volatilisation is. With the increase in temperature and keeping time, most of the PbO can be evaporated and leaves little PbO in the residual slag. This will has great effect to physico-chemical property measurement of the slag with higher PbO content, especially to the property measurement that be kept at high temperature for a long time. Because the volatiles is trend to condense with the temperature decrease, mass spectrometer is limited by the condensation of volatiles, i.e., PbO, ZnO and so on, in the connection pipeline. The device should be modified for this use.

Combustion Characteristics of Coal for Pulverized Coal Injection (PCI) Blending with Steel Plant Flying Dust and Waste Oil Sludge.

Various characterization methods are used to investigate the physical and chemical properties of steel plant flying dust and waste oil sludge, and the combustion characteristics of the mixtures with pulverized coal are studied via thermogravimetric analysis; the catalytic combustion mechanism is also explored. The results show that two types of metallurgical by-products with small particle sizes and developed pores are evenly dispersed in the pulverized coal and are stably combined with it. The additives reduce the ignition temperature and the temperature corresponding to the maximum combustion rate of pulverized coal; simultaneously, they increase the heat released during pulverized coal combustion. During the pyrolysis stage of pulverized coal, the heat generated via organic component combustion in waste oil sludge promotes a cracking reaction and improves the development of the char's micropore. During the char combustion stage, no catalyst deactivation phenomenon occurs under the ratios of inorganic components in the two types of metallurgical dust and sludge. Two additives markedly reduce the activation energy of the combustion reaction.

Viscosity estimation model of fluorine-containing mold flux for continuous casting.

A viscosity estimation model for fluorine-containing mold flux for continuous casting was investigated based on the Arrhenius formula and the rotating cylinder method combined with nonlinear regression analysis. This model is highly applicable and not limited by the slag of a certain composition. For most slag compositions, the viscosities estimated with this model deviated from the measured values by no more than 10%, which was in better agreement with the measured values than the viscosities estimated by the Riboud, Iida and Mills models. According to the model calculation and experimental detection, a viscosity isogram of CaF2-Na2O-Al2O3-CaO-SiO2-MgO slag was produced, and the mass fraction of CaF2 in the low-viscosity zone was nearly 14%. An X-ray fluorescence spectrometric analysis of slag after the viscosity test showed that CaF2 and Na2O were significantly reduced, and the measured viscosity was greater than the theoretical viscosity due to the volatilization.

Coupled Preparation of Ferronickel and Cementitious Material from Laterite Nickel Ores.

Nickel slags can be produced through ferronickel preparation by the pyrometallurgical processing of laterite nickel ores; however, such techniques are underutilized at present, and serious environmental problems arise from the stockpiling of such nickel ores. In this study, a modification to the process of ferronickel preparation by the direct reduction of carbon bases in laterite nickel ores is proposed. The gangue from the ore is used as a raw material to prepare a cementitious material, with the main components of tricalcium silicate and tricalcium aluminate. By using FactSage software, thermodynamic calculations are performed to analyze the reduction of nickel and iron and the effect of reduction on the formation of tricalcium silicate and tricalcium aluminate. The feasibility of a coupled process to prepare ferronickel and cementitious materials by the direct reduction of laterite nickel ore and gangue calcination, respectively, is discussed under varying thermodynamic conditions. Different warming strategies are applied to experimentally verify the coupled reactions. The coupled preparation of ferronickel and cementitious materials with calcium silicate and calcium aluminate as the main phases in the same experimental process is realized.

The volatilization behaviour of typical fluorine-containing slag in steelmaking.

It was taken as typical steelmaking fluorine-containing slag systems with the remelting electroslag, continuous casting mould flux and refining slag. The volatilization behaviour of each slag system was analysed by thermogravimetric (TG) and mass spectrometry (MS) detection. The results showed that the remelting electroslag volatilized significantly above 1300°C and the volatiles were mainly CaF2, MgF2 with a small amount of SiF4 and AlF3; the continuous casting mould flux volatilization was divided into two stages, in the first stage (500°C∼800°C), CaF2 and Na2O reacted to form NaF, and in the second stage (greater than 1200°C), the CaF2 evaporation was highlighted; for CaF2-CaO-based refining slag, the volatilization was the most significant at the eutectic point 84% CaF2-16% CaO, and the volatility can be reduced by adding 5% SiO2. This research will be guiding significance for the composition and performance control of fluorine-containing slag and metallurgical environmental protection in the steelmaking process.

Effect of the heating rate and premelting process on the melting point and volatilization of a fluorine-containing slag.

The melting point and volatilization characteristics of a fluorine-containing slag were investigated under different heating rates and premelting processes. The "hemisphere method" was used to detect the melting point, and the results showed that the measurements for the fluorine-free slag increased with increasing heating rate, and the deviation reached 60 °C and was affected by the hysteresis and fractional melting. The measured values and volatilization of the fluorine-containing slag decreased with increasing heating rate. The weight loss reached 16.8%, and the melting point deviation reached 90 °C, which was primarily affected by the volatility. The melting point of the synthetic fluorine-containing slag was 70 °C higher than that of the premelted slag due to flux volatilization of 8.3%. Scanning electron microscopy-energy dispersive spectroscopy revealed a large amount of CaF2 on the surface of the melted slag. The internal crystals in the synthetic slag were mainly diamond-shaped calcium fluoroaluminate (3CaO·3Al2O3·CaF2) and those in the premelted slag were needle-shaped cuspidine (3CaO·2SiO2·CaF2) that formed during secondary crystallization. Two factors that impacted the volatilization were proposed: one is the content of free CaF2, and the other is the slag structure. Based on these factors, volatilization models for synthetic and premelted fluorine-containing slags were established. This work is of significance for relevant measurement specifications to ensure the repeatability and comparability of the physicochemical properties, especially for volatile-containing slags.

Magnetic apple pomace biochar: Simple preparation, characterization, and application for enriching Ag(I) in effluents.

In order to manage and utilize a large amount of wasted apple pomace, the magnetic biochar was prepared through pyrolysis of apple pomace at 600 °C in nitrogen environment, followed by immersion aging in Fe(II)/Fe(III) aqueous solution. The characterization of the resulting magnetic biochar, herein called the M600APB, showed that the saturation magnetization value and the Brunauer-Emmett-Teller (BET) specific surface area of M600APB were 9.52 emu/g and 102.18 m2/g, respectively. The batch adsorption showed that M600APB could preferentially enrich the low concentration of Ag(I) with the maximum adsorption capacity of 818.4 mg/g in an Ag(I)-Pb(II)-Cu(II)-Ni(II)-Zn(II) aqueous system at ambient temperature. The column adsorption experiments indicated that M600APB could effectively enrich and separate Ag(I) from the same aqueous mixture. The presumable mechanism of Ag(I) adsorption on M600APB involves intra-particle diffusion, coordination, ion exchange and reduction. This study provided an effective approach to both utilize wasted apple pomace and enrich the low concentration of Ag(I) in a sustainable way.

Synthesis of rhombic dodecahedral gold nanocrystals by dimethylformamide reduction.

We report a facile and low-cost wet chemical method for preparation of gold (Au) nanocrystals with morphology of well-defined rhombic dodecahedron (RD). The Au nanocrystals with the RD shape have been synthesized by reducing HAuCl4 in N,N-dimethylformamide (DMF) solvent in an autoclave for 15-24 h at 90 degrees C. Thus-synthesized Au nanocrystals have been characterized by a scanning electron microscopy (SEM), transmission electron microscopy (TEM), and selected-area electron diffraction (SAED). The results show that the RD nanocrystals are exclusively enclosed by twelve {110}-type facets. Furthermore, concave RD Au nanocrystals can also be produced only by changing reaction time or adding ascorbic acid (AA). A possible evolution mechanism of the RD Au nanocrystals has been suggested.