The coagulation properties of HCCA in the system “aluminate solution - nepheline sludge” were studied, which allowed to improve the processes of thickening and washing of nepheline sludge. Solutions were developed aimed at the improvement of the coarse alumina production technology on the basis of increasing the efficiency of the carboaluminate method for separating Al (III) and Si(IV) hydroxo complexes and using the combined crystal growing modifier CaCO3 – HCCA.

This article describes a technology for the thermomechanical treatment of stainless-steel piston rings. This technology makes it possible to obtain rings with an optimal combination of plastic and strength properties that is essential for piston rings. The following thermomechanical treatment is suggested for piston rings manufacturing: quenching at 1050 °C, holding for 30 min and cooling in water, then straining by the HPT method for eight cycles at cryogenic temperature and annealing at a temperature up to 600 °C. The resulting microstructure consisted of fine austenite grains sized 0.3 μm and evenly distributed carbide particles. Annealing above this temperature led to the formation of ferrite in the structure; however, preserving the maximum fraction of austenitic component is very important, since the reduction of austenite in the structure will cause a deterioration of corrosion resistance. The strength properties of steel after such treatment increased by almost two times compared with the initial ones: microhardness increased from 980 MPa to 2425 MPa, relative elongation increased by 20%. The proposed technology will improve the strength and performance characteristics of piston rings, as well as increase their service life, which will lead to significant savings in the cost of repair, replacement and downtime.

The article is devoted to the influence of brown coal additives on the sintering of the lime-nepheline charge in the technology of alumina production from nepheline. The process of extraction of humic compounds from brown coal is considered, the effect of humic additives on the rheological properties of pulp depending on the size and moisture content of carbon-containing additives is studied.

The article is devoted to the problems of aluminate solutions sorption purification from harmful organic impurities in the production of alumina from the Bayer experiment. The study of sorption of basic classes of organic impurities isolated from industrial aluminate solutions showed that magnesium and calcium hydrocarboaluminates have a high selectivity in relation to the most harmful classes of organic substances for the process. The results of the sorption process kinetics and thermodynamics studies are given, optimal technological parameters of sorption purification and conditions for the synthesis of active sorbents from alkaline aluminate solutions and activated magnesium and calcium raw materials are determined.

No abstract