Milorad Gavrilovski

Combustion of Metallurgical Wastes Using Secondary Aluminum Foils

ABSTRACT Simulating the reactions in a complex system can lead to self-sustaining and energy efficient treatment of wastes in recycling promoting manner. In this contribution, the synergic combination of electric arc furnace dust (EAFD), mill scale, and secondary aluminum, in a form of waste foil, was researched aiming to use exothermal energy of reactions and to obtain environmentally favorable products. The secondary aluminum in the form of foil was prepared in different ways in order to develop aluminum surface and to be suitable for aluminothermic reactions. The commercial aluminum powder was used to determine optimal conditions using full factorial experiment design. After that, research was performed on aluminothermic reactions with the aluminum powder obtained from secondary aluminum foils. Results show that the secondary aluminum can be successfully used for a treatment of oxides bearing hazardous wastes in an energy efficient and environmentally friendly manner. The comparative life-cycle assessment revealed several advantages of using the secondary aluminum foil as a reduction agent compared to the conventional recycling of the secondary aluminum foil.

Development of the universal tool for testing of tensile properties of hexagonal steel wire mesh for civil engineering

The developing of the universal tool for testing of tensile properties of hexagonal steel wire mesh for civil engineering is described in this paper. The developed tool allows repeated testing of hexagonal steel wire mesh of different dimensions without tool changes and is generally related with the procedure for the determination of tensile strength properties of different wire meshes. The construction of the tool which is related to the aims of the decreased mass consumption and high operation safety is described in detail. Particular attention is focused on the safety component of the tool which ensuring safety testing by preventing slipping of the wire mesh samples during loading. The paper also presents the Finite Element Analysis performed in order to verify the high safety factor of the developed tool. The contact regions with stress concentration behavior are analyzed by non-linear solvers. The obtained results and conclusion about the possible contributions of the developed universal tool for extensively testing of wire meshes for civil engineering are discussed.

Kinetics of NiO and NiCl2 Hydrogen Reduction as Precursors and Properties of Produced Ni/Al2O3 and Ni-Pd/Al2O3 Catalysts

The objects of this investigation were the comparative kinetic analysis of the NiO and NiCl2 reduction by hydrogen during an induction period and elimination of the calcination during the synthesis of Ni/Al2O3 catalysts. The effect of temperature and time on NiO and NiCl2 reduction degrees was studied. Avrami I equation was selected as the most favorable kinetic model and used to determine activation energy of the NiO and NiCl2 reduction for the investigated temperature range (623–923 K) and time intervals (1–5 minutes). The investigation enabled reaching conclusions about the reaction ability and rate of the reduction processes. Afterward, Ni/Al2O3 catalysts were obtained by using oxide and chloride precursor for Ni. The catalysts were supported on alumina-based foam and prepared via aerosol route. Properties of the samples before and after low-temperature hydrogen reduction (633 K) were compared. Obtained results indicated that the synthesis of Ni/Al2O3 catalysts can be more efficient if chloride precursor for Ni is directly reduced by hydrogen during the synthesis process, without the calcination step. In addition, Ni-Pd/Al2O3 catalysts with different metal content were prepared by using chloride precursors. Lower reduction temperature was utilized and the chlorides were almost completely reduced at 533 K.

The effect of primary copper slag cooling rate on the copper valorization in the flotation process

Technological procedure of slow cooling slag from primary copper production is applied in the purpose of copper recovery in the level of 98.5% to blister. This technological procedure is divided into two phases, first slow cooling of slag on the air for 24 hours, and then accelerated cooling with water for 48 hours. Within the research following methods were used: calculation of nonstationary slag cooling, verification of the calculation using computer simulation of slag cooling in the software package COMSOL Multiphysics and experimental verification of simulation results. After testing of the experimentally gained samples of slowly cooled slag it was found that this technological procedure gives the best results in promoting growth or coagulation of dispersed particles of copper sulfide and copper in the slag, thereby increasing the utilization of the flotation process with a decrease of copper losses through very fine particles.