Том 60, № 1 (2019)

The paper provides a brief description of the technological process and design of the rotary kilns for petroleum coke KEP-1 and KEP-2 calcination, as well as specifies the lining requirements for some parts of such kilns. The lining bricklaying specifics and main techniques with respect to rotary kilns (including foreign designs) are demonstrated. A feasible lining option for rotary kilns measuring 3 m in diameter and 45 m in length is described. Lining design and modern materials are proposed for a calcination kiln used in the production of calcined petroleum coke KEP-2.

We study the refractory equipment of the receiving chambers of continuous casting machines and the processes of control over the flows of metal in these chambers running in the case of casting from the steel-teeming ladle by open streams. This guarantees the possibility of effective formation of steel flows in the receiving chamber of the tundish of continuous casting machine and creates conditions for the improvement of the quality of the metal and the decrease in the number of rejected continuously cast billets.

This paper contains information on foreign manufacturers of alumina ceramics, and mainly, fine technical ceramics. The data concerning mechanical, thermal, and dielectric properties of the products manufactured by different companies are presented. Several methods for producing Al₂O₃-based ceramics are considered with respect to future commercial production.

The mechanism of self-propagating high-temperature synthesis (SHS) of AlB₂–Al₂O₃ composite powders was studied using the combustion front quenching method (CFQM). The results showed that the combustion began with fusion of B₂O₃ and Al particles followed by mutual penetration of Al and B₂O₃ in the melt. X-ray patterns exhibited reflections for Al₂O₃ that were consistent with exchange of O atoms between Al and B through the reaction B₂O₃ + 2Al → 2B + Al₂O₃. A certain amount of B₂O₃ volatilized at higher temperatures and reacted with B to form gaseous B₂O₂. Al₂O₃ and B precipitated on the Al surface. Then, the produced B dissolved in the Al melt and reacted with Al to precipitate AlB₁₂ particles. Finally, AlB₁₂ transformed into AlB₂ at the peritectic temperature during rapid cooling. Thus, the combustion could be explained by a dissolution-precipitation mechanism. The final products included AlB₂ and Al₂O₃ particles and a certain amount of Al. A model of the dissolution-precipitation mechanism was proposed. The ignition temperature of the combustion was ~800°C.

The main question for understanding the corrosion of a side lining made from silicon carbide based on a silicon nitride binder is whether corrosion of Si₃N₄–SiC material by gases (and, in particular, oxidation) is preceded by corrosion by molten electrolyte, or corrosion by molten electrolyte plays its own role in material degradation during service. It is more probable that reactions of SiC and Si₃N₄ with molten cryolite pass through a pre-oxidation stage. Calculations show that the majority of possible reactions of SiC and Si₃N₄ with oxygen, carbon monoxide, and carbon dioxide have a positive volumetric effect, which reduces material porosity, but may cause crack development within it. In this case the silicon oxide formed is dissolved in molten electrolyte and may also react with electrolyte components in the gas phase.

Results are provided for thermal cycling tests of a number of highly refractory products. It is shown that periclase products from fuzed powders coated with ZrO₂ are the most resistant to cyclic variable thermal loads. The structure of corundum products in the process of thermal cycling tests deteriorates significantly due to recrystallization and the formation of new phases. In order to organize the lining and test unit heat exchange fittings operating under conditions of variable loads in pulsed piston units objects made from fuzed periclase powders modified with ZrO₂ are recommended.

Correlation of the structure of Al₂O₃ ceramics with specimen polished surface roughness and morphology is established. On basis of this the physical nature of surface layer formation during diamond grinding of fine-grained and coarse-grained ceramics is been revealed.

In light of the continuing decrease in the cost of carbon nanotubes (CNT) and the promising properties of ceramic matrix composites (CMC) reinforced with CNTs, their wide application in industry is on the agenda. For this, inexpensive technologies for the production of CNTs are necessary. Technological stages of the industrial production of complex-shaped products from carbon nanotube-reinforced ceramic matrix composites (CNT-CMC) are reviewed: the cleaning of raw materials after their production, the dispersion of aggregates and some methods for modifying their surface.

Joint reduction of zirconium dioxide and sodium carbonate to form zirconium carbide was studied. Magnesiothermic reduction of ZrO₂ was shown to occur at 600 – 620°C; Na₂CO₃, 590 – 610°C. Thermodynamic calculations and x-ray phase analyses indicated the transformations occurring during the synthesis and the resulting reaction products. Use of graphite as the carbon source did not lead to ZrC formation at 700 – 900°C, in contrast with Na₂CO₃.

Amathematical model of vortex hydraulic dust suppression is proposed. Equations for calculating the magnitude of the reduction in the required energy for total absorption of dust particles, the effective wetting angle, and the minimum diameter of the absorbed dust particles as a function of the angular of liquid droplet rotation velocity are obtained. It is shown that vortex hydraulic dust suppression significantly reduces the size of the dispersed dust composition, water consumption, and increases the efficiency of dust suppression.

A new belt conveyor design providing the possibility of changing the conveyor belt cross section depending on the flow of transported bulk material has been proposed. A procedure for determining the load on the hold-down lever rotation mechanism is presented. A calculation of the value of equivalent load applied to the coupler (considering crimping) is provided, which allows selecting the inner diameter and trapezoidal thread parameters of the coupler, calculating the screw pair moments of resistance, and choose the appropriate size of the gear motor.

This paper reviews the fundamentals of the technology and theory of the process of thermal activation of vermiculite-sungulite conglomerates contained in the waste of the Kovdor phlogopite-vermiculite field. An analytical physical model has been developed to describe a single-layer flow of vermiculite-sungulite conglomerate vibro-transported in a thermal field using a vibration hearth platform of an electric furnace. The absorptivity and reflectivity of a dense single-layer array of the processed conglomerate located on a plane under thermal radiation conditions have been determined. Using sungulite, pyroxene, olivine, and a number of other minerals, the correlation of their absorptivity with relative thermal diffusivity and thermal conductivity was demonstrated.

This paper provides a review of aluminum oxide properties associated with its use, varieties of commercial products, methods for producing aluminum oxide in a disperse state, in the form of polycrystalline ceramics and single-crystal products, as well as chemical aspects of the related technological processes.

The influence of the carbon sorbent surface structure and electron affinity of the molecule on the adsorption of poly- and heterocyclic aromatic hydrocarbons is evaluated. By adjusting the reducing ability of the surface of the carbon material, it is possible to control the adsorption process and the selectivity of the sorbent relative to condensed aromatic systems.