Utilization Prospects of Carbon Concentrate – a Product of Aluminium Smelting Carbon Dust Processing

The possibilities of utilization of technogenic products of aluminum production: coal foam and carbon concentrate (СС) are considered. It is proposed to utilize CC in order to extract valuable components. The regularities of the utilization process of CC by the combustion method have been studied. It was found that the content of germanium in ash is determined by the temperature and the oxygen partial pressure in the system. Gallium is concentrated in ash in an amount of 0.8 wt.% during the combustion in a fluidized bed at a temperature of 1200 °C, the germanium extraction into sublimates reaches 90 %. The results of the leaching of gallium from the ash residue in acidic and basic media are presented; the maximum gallium extraction was 90 and 94 %, respectively.

Synthesis and Applications of Inorganic Materials Derived from Aluminium Smelting Waste

<p>Red mud is the highly alkaline, toxic residue of the aluminium ore bauxite after extraction of the aluminium by the Bayer process. The storage and utilization of red mud present significant environmental problems. The possibility of producing viable inorganic polymers (geopolymers) from red mud and its precursor mineral bauxite was investigated, using sodium hydroxide and/or sodium silicate as the activator, and adjusting the composition of the mixture by the addition of fine silica or ρ-alumina. The compressive strengths of the samples were measured after curing for 21 days. Although all the samples showed drying cracking, the strengths were very encouraging, the highest strength being 58 Mpa from a red mud sample containing additional silica, and the highest strength from bauxite samples being 28 MPa; the compositions of these samples also being adjusted by the addition of fine silica. These strongest samples were prepared from red mud and bauxite that had been calcined at 500°C given by RMGP4, and 28 MPa from BS2. They were made from calcined red mud and bauxite, which therefore seem to be more reactive to alkali than the as-received materials. XRD, SEM/EDS and solid-state NMR spectroscopy were used to study the microstructure and compositions of the end products. XRD revealed that iron occurs as hematite (Fe₂O₃) in the red mud, bauxite and most of the red mud geopolymers, and is present as other crystalline minerals in the other geopolymer samples. SEM spectroscopy shows that the red mud and bauxite were relatively highly porous and non-crystalline. EDS confirms that iron is present as one of the major elements in the material as well as in the geopolymers. ²⁷Al NMR spectroscopy revealed that Al is present in more tetrahedrally coordinated sites than in octahedral. ²⁹Si NMR is greatly affected by the presence of iron, resulting in very noisy spectra and in some cases no signals were obtained. These results suggest that iron does not necessarily interfere with geopolymer formation, and thus the utilisation of red mud to produce usefully strong geopolymers on a larger scale is feasible, provided the problem of cracking can be solved.</p>

Synthesis and Applications of Inorganic Materials Derived from Aluminium Smelting Waste

<p>Red mud is the highly alkaline, toxic residue of the aluminium ore bauxite after extraction of the aluminium by the Bayer process. The storage and utilization of red mud present significant environmental problems. The possibility of producing viable inorganic polymers (geopolymers) from red mud and its precursor mineral bauxite was investigated, using sodium hydroxide and/or sodium silicate as the activator, and adjusting the composition of the mixture by the addition of fine silica or ρ-alumina. The compressive strengths of the samples were measured after curing for 21 days. Although all the samples showed drying cracking, the strengths were very encouraging, the highest strength being 58 Mpa from a red mud sample containing additional silica, and the highest strength from bauxite samples being 28 MPa; the compositions of these samples also being adjusted by the addition of fine silica. These strongest samples were prepared from red mud and bauxite that had been calcined at 500°C given by RMGP4, and 28 MPa from BS2. They were made from calcined red mud and bauxite, which therefore seem to be more reactive to alkali than the as-received materials. XRD, SEM/EDS and solid-state NMR spectroscopy were used to study the microstructure and compositions of the end products. XRD revealed that iron occurs as hematite (Fe₂O₃) in the red mud, bauxite and most of the red mud geopolymers, and is present as other crystalline minerals in the other geopolymer samples. SEM spectroscopy shows that the red mud and bauxite were relatively highly porous and non-crystalline. EDS confirms that iron is present as one of the major elements in the material as well as in the geopolymers. ²⁷Al NMR spectroscopy revealed that Al is present in more tetrahedrally coordinated sites than in octahedral. ²⁹Si NMR is greatly affected by the presence of iron, resulting in very noisy spectra and in some cases no signals were obtained. These results suggest that iron does not necessarily interfere with geopolymer formation, and thus the utilisation of red mud to produce usefully strong geopolymers on a larger scale is feasible, provided the problem of cracking can be solved.</p>

Numerical Modelling of Gaseous Fuel Combustion Process with the Stepwise Redistribution of Enriched Combustion Air

The authors of this paper present the results of simulations for burner system design changes in the smelting aggregate. Based on the analysis of the existing burner system in the experimental aluminium smelting equipment, changes in the burner design were proposed. The obtained results are presented in tables and figures. The properties of the proposed changes were investigated using the simulation software ANSYS. The simulations confirmed the suitability of the proposed system for shortening the flame length and intensification of the mixing of gaseous media.