Hydrometallurgical extraction of antimony from lead refining slags

Today, in order to optimize the production of copper, zinc, and lead, as well as to reduce the circulation of associated metal impurities (such as antimony, tin, bismuth and others) between the processing facilities, an ever greater attention is given to the development and implementation of processing schemes that would enable to extract associated metals and use them to produce commodities. In connection with the above, a process has been developed and tested for processing lead refining slags which include, %: 25–30 Sb, 2–10 Pb, 1–8 Sn, 3–12 As, 0.1–0.2 Cu. The resultant products included the Su-2, Su-1 and Su-0 grades of antimony or antimonous oxide. It was found that the forms in which antimony was present in the untreated slag included Sb2O3, Sb2O4, Sb2O5 and NaSb(OH)6. A hydrometallurgical process based on the use of sulphide alkaline solutions was taken as the basic slag processing technique. It is proposed to wash the slag additionally before leaching to remove arsenic from antimony, and to use the electrowinning stage to separate tin from antimony. Regimes have been identified for obtaining cathode deposits containing 96–99% Sb, with the recovery of antimony from untreated slag being 67%. The cathode deposits were refined with the help of pyrometallurgical methods and electrolysis in sulphate-fluoride media. The paper also considers the possibility of obtaining antimonous oxide by oxidizing the antimonous oxide melt and recovering Sb2O3 from exhaust gases. Based on the findings and the results of the tests, Uralelectromed is now working on designing a slag processing facility.

Corrosion of MgO-C with Magnesium Aluminate Spinel Addition in A Steel Casting Simulator

For more than 20 years, the sidewalls and bottom of steel ladles have been lined with carbon-bonded magnesia (MgO-C) and magnesia-alumina bricks (MAC). The alumina raw materials react with magnesia forming a spinel, which decreases open porosity and slag infiltration. The amount, grain size, and chemistry of the added spinel impact the properties of spinel-containing MgO-C. Corrosion tests have been performed in a steel casting simulator at 1580 °C using 18CrNiMo7-6 steel and Fe-rich slag as corrosion medium. Digital light microscopy and SEM/ EDS (scanning electron microscope with energy dispersive spectroscopy) were used to evaluate the corrosion mechanisms. The metal casting simulator test showed that the addition of CaO-MgO-Al2O3 aggregates results in the highest corrosion resistance against molten steel and synthetic basic slag compared to alumina-rich spinel aggregates.

Design of ESR Slag for Remelting 9CrMoCoB Steel under Simple Protective Ar Gas

Thermodynamic calculations by using Factsage 7.3 and simple protective gas electroslag remelting (ESR) experiments were conducted to design the appropriate ESR slag for remelting the qualified 9CrMoCoB ingot. First, the proper basic slag was determined based on the phase diagram of CaF2–CaO–Al2O3–x%MgO calculated using Factsage 7.3. Second, equilibrium reactions between 9CrMoCoB and the basic slag containing varied SiO2, and B2O3 contents were calculated to study the effects of B2O3 and SiO2 on B, Si, and Al contents in steel. Then, equilibrium reaction experiments were conducted to validate the calculated results. Finally, the appropriate slags were attained and the simple protective Ar gas ESR experiments were conducted to make a verification. Results showed that the liquid phase region of the slag of CaF2–CaO–Al2O3–x%MgO at 1300–1400 °C increased first, then decreased with the MgO addition. With the B2O3 content increasing, the boron content increased, while the Si, Al contents decreased, and at a given B2O3 addition, the B and Al contents decreased with the SiO2 content increasing, whereas the Si content increased. The appropriate slags for simple protective gas ESR remelting 9CrMoCoB were 55%CaF2–20%CaO–3%MgO–22%Al2O3–2%SiO2–1.3%B2O3 and 55%CaF2–20%CaO–3%MgO–22%Al2O3–3%SiO2–1.7%B2O3.

Long term carrying over effects of basic slag, soil aggregate size and groundwater treatments for the reclamation of acid sulfate soils

A pot experiment was conducted to study the carrying over effects of soil aggregate size, groundwater level and basic slag treatments in acid sulfate soils of Badarkhali and Cheringaseries which were examined for the reclamation during 1998-2001. Initially the soils were very strongly acidic (pH 3.9 for Badarkhali; 3.6 for Cheringa) and very strongly saline (ECe 23 mS/cm for Badarkhali) to moderately saline (10.3 mS/cm for Cheringa). Application of these treatments exerted remarkable improvement in soil fertility and plant growth on these soils after 18 years of occasional cultivation. In 2016, pH at different treatments in these soils ranged from 6.2 to 7.4 for Badarkhali, 5.2 to 7.1 for Cheringa and ECe from 1.7 to 3.2 mS/cm for Badarkhali, 1.5 to 8.75 for Cheringa soils. At the same time in Badarkhali soil, organic matter content (1.3 - 2.8%), total N (0.02 - 0.11%), available N (2.69 - 18.29 mmol/kg), available P (0.78 - 5.08 mmol/kg) were determined and almost similar values of these parameters were recorded in Cheringa soil. Available S contents were found to decrease and ranged from 0.06 - 0.18 cmol/kg in Badarkhali and 0.08 - 0.21 cmol/kg in Cheringa soils. In spite of using basic slag, the concentrations of lead and cadmium in the studied soils were determined below (highest value of Pb was 2.07 mg/kg and Cd 1.8 mg/kg) the normal contents (Pb 70 mg/kg and Cd 10 mg/kg) in the agricultural soils.Bangladesh J. Sci. Res. 30(1&2): 69-79, December-2017

Nutrition of rice as influenced by reclamation techniques for acid sulfate soil in Cox’s Bazar

A field experiment was conducted for the reclamation of a Cheringa hot spot of acid sulfate soil manipulated by flash leaching followed by basic slag (BS; BS10 and BS20: basic slag at 10 and 20 t ha-1), aggregate size (A; A20 and A30: aggregate sizes of soil less than 20 and 20-30 mm) treatments under two different techniques (Tech 1: pyrite layer at top, jarosite layer at middle and top soil at the bottom of ridge; Tech 2: top soil at top, pyrite layer at middle and jarosite layer at the bottom of ridge). Nutritional responses to two cultivars of rice with the treatments were evaluated. The initial soil had very low pH (H2O); 3.4, and high EC; 1.6 m S-1, and pyrite content, 76 g kg-1. Magnesium content (5.38 c mol kg-1) of the soil was about 3 fold than that of Ca (1.71 c mol kg-1), and Al content (9.22 c mol kg-1) was at a highly toxic level. The average soil data of all the treatments, except for the control plots after harvesting of rice were increased by 1.5 units for soil pH and 12 to 463% for the contents of N, P, Ca and Mg, while the concentrations of Fe, Al, Na, Cl- and SO4 2- decreased by 27 to 93% compared with the initial soil. The highest N, P, K, Ca, and Mg contents in both the BR 14 and Pizam rice shoots at maturity were obtained by the A20BS30 followed by A20BS20?A30BS30 treatments. The other treatments also resulted in a significant (p?0.05) improved performance on plant nutrition compared with the control. The local Pizam exhibited the best responses under the Tech 2 in order of these nutrient uptakes. Sulfur content in the rice plants on control plots was high (1.8-2.1 g kg-1) but it decreased significantly by the different treatments.Bangladesh J. Sci. Ind. Res. 52(2), 97-106, 2017

New FCAW Electrode for Producing Ultra-Clean High-Toughness Welds in X-80 and X-100 Steel

The challenges associated with the welding of high-strength pipeline steels, such as X-80 and X100, are well established. While there are many filler metals that provide either adequate strength or good impact toughness, it is difficult to find products that provide both. Add to that the need for all-position welding and high deposition rates, and the options become almost non-existent. Several years ago, Hobart® Filler Metals began working on a line of flux-cored arc welding (FCAW) consumables that are unique in the welding industry. The products have a basic slag system, but do not operate like traditional EXXXT-5 electrodes. Traditional T-5 electrodes have a low-melting, fluid slag, which makes welding out-of-position especially difficult. They also have a high level of calcium fluoride, which affects the stability of the arc and causes weld spatter. While the weld metal mechanical properties and crack-resistance are excellent, the welder appeal and ease-of-use tend to be sorely lacking in most EXXXT-5 electrodes. The new approach utilizes aluminum for deoxidation, which has the added benefit of very clean weld deposits. The composition has been carefully optimized with appropriate levels of carbon, silicon, nickel and manganese. Alternative fluorine sources are used in place of calcium fluoride, which results in very good welder appeal and all-positional capabilities, including vertical down. The novel use of aluminum in a gas shielded process results in very low oxygen, nitrogen and sulfur content, providing exceptionally clean, tough weld deposits. Although the new products have been produced over a range of strength levels, the primary emphasis of this paper is on E691T5-GC (E101T5-GC) and E831T5-GC (E121T5-GC) electrodes. Testing shows that tensile strength levels ranging from 700–880 MPa (100–128 ksi) can be achieved, with toughness levels of 120 J at −60°C (90 ft-lbs at −76°F) or better. The highly basic slag, combined with low weld metal hydrogen (less than 4 ml/100 gm), provides excellent resistance to cracking. The product can be used in all positions, including vertically down, making it an especially appealing choice for welding high-strength pipe.

Investigation into Electrical Conductivity of the Multicomponent System of Trackbed

The article deals with the measuring results of the specific conductance of multicomponent systems which consist of more than three materials of various characteristics. As it was shown the electrical conductivity of systems composed of soil, slag and water depends in a lesser degree on the amount of slag and in a greater degree on slag’s chemical composition. The value of specific conductance decreases when the amount of slag increases for basic slag, and increases for acid slag. For a system, which includes gravel particles coated with organic substances, the value of specific conductance correlates with the electric properties of the materials used, namely the function of chemical composition of the musticomponent system. Thus, there is a possibility to design a mathematical model for forecasting electric properties of multicomponent systems, which is based on an objective characteristic, namely, chemical structure of the materials used.