Allerton Press

Tests on the treatment of zinc cakes were carried out according to the flow chart, including the sulfatization with oleum and leaching with the sulfuric acid solution.

The feasibility of developing a waste heat recovery system from waste hot air generated by the reduction system in Kroll process to pre-heat water is studied in this paper, in order to reduce energy loss. In the proposed system, the hot air from reduction reactor was first collected by pipelines with insulating material, and then supplies to a shell-and-tube heat exchanger to heat up water. And the energy, exergy analysis of the whole waste heat recovery system have been carried out firstly on the basis of material, energy and exergy balance. Then, the thermo-economic analysis and economic analysis of the waste heat recovery system are also discussed. The results show that the waste heat recovery system presented in this paper could be applied not only for restricted category of reduction system in Kroll process, although the energy efficiency and exergy efficiency of the waste heat recovery system are as low as 26.84% and 11.09%, respectively. And more than two times equivalent energy could be obtained from the waste heat recovery system. The payback period of a waste heat recovery system is about 4.39 years.

The kinetics of hydrogen absorption by a powder of yttrium dihydride is investigated. A sample having a known specific surface area and a composition close to the lower concentration boundary of the homogeneity region of dihydride is saturated with hydrogen in a Siverts apparatus at 300–450°C and hydrogen pressures of 5–45 kPa. The diffusivities of hydrogen (D H) are evaluated on the basis of absorption kinetic curves using a previously developed technique based on the possibility of ignoring the surface curvature at degrees of saturation tending to zero. The temperature dependence of D H (m2/s) in the range of 300–450°C is log D H = −12.7 − 1770/T.

The influence of the precrystallization flow of copper and aluminum melts on the hardness and abradability of ingots is investigated. The flow was organized via passing the melts through the round-section tubes. The hardness of metals was determined by the Brinell method, and abradability was evaluated on a setup for investigating the friction properties of materials. The stability of the chemical composition of metals was monitored by spectral chemical analysis. It is established that there is an 8–17 and 7–10% increase in hardness and a 11–15 and 10–11% decrease in abradability, respectively, in the samples of copper and aluminum subjected to the flow in the molten state. It is noted that, taking into account the results of a spectral chemical analysis, the variation in the properties of metals is most likely caused primarily by the directed precrystallization flow of corresponding melts rather than by variations in the chemical composition.

A simulation of the direct extrusion method of large-size rods with diameters of 188, 214, 252, 283, 326, and 560 mm made of alloy 7075; coefficients of friction of 0 and 0.5; and die cone angles of 80° and 90° from a container with a diameter of 800 mm using a 200-MN press with the help of the DEFORM-2D software package is performed. The distribution of radial velocities of metal flow on a working surface of a pressure pad depending on the contact friction, die cone angle, and elongation ratio at the main and final stages of extrusion is found. The butt-end height at the beginning instant of funnel formation is accepted equal to the distance between the pressure pad plane and input plane of extruded metal into a screw channel of flat or cone dies. The combined effect of the elongation ratio, coefficient of friction, and die cone angle on the butt-end height, extrusion force, intensities of strain rates and stresses, and temperature on the die orifice edge is investigated. Numerical experiments are performed according to the complete factorial plan 23 for variability intervals of parameters: Х1 = 3–9, Х2 = 0–0.5, Х3 = 80°–90°. Friction between the tool and the billet at the final stage of extrusion plays a negative role, noticeably decreasing the radial velocity. This leads to the earlier onset of the formation of the central funnel. Extrusion into a conical die and an increase in the elongation ratio, on the contrary, increase the radial flow velocity and provide the later onset of formation of a central funnel. The main factor that determines the butt-end height is the elongation ratio. A mathematical model is proposed to select the butt-end thickness for concrete extrusion conditions of large-dimensioned rods with small elongation ratios.

An analysis of flowsheets for processing sulfide and oxide copper ores, reagent modes, processing equipment, and flotation indicators in some domestic and foreign processing plants and productions is carried out. Autogenous and semiautogenous mills are commonly used in the primary grinding stage in ore processing plants, which excludes medium and fine crushing. The alternative is high-pressure grinding rolls, which can reduce electricity consumption compared with autogenous and semiautogenous grinding. An increase in the use of large-volume and high-performance ore-processing flotation equipment to maintain the quality and quantity of the product is noted. In addition to ball mills, fine- and ultra-fine-grinding mills in different configurations are widely used in the regrinding stage of the rougher flotation concentrate. An analysis of the flotation reagents to increase the efficiency of the separation process is made, where domestic and foreign approaches to the selection of flotation reagents are given. It should be noted that the combination of primary and secondary collectors is often used in foreign processing plants. Flotation reagents used in the processing of copper sulfide and oxide ores and their costs are presented. The combined circuit of flotation-hydrometallurgical processing of mixed copper ore at the Udokan deposit is considered. The conclusions reveal the current trends in the processing of copper ores, including the choice of equipment.

The conditions of obtaining manganese dioxide using diaphragm-free electrolysis are investigated. The optimum mode of obtaining the product is established, depending on the current density, process duration, and acidity.

A group of composite bronzes BrZhNKA 9-4-1-1, BrZhNA 12-7-1, etc., has been studied. Brittle intermetallic compounds of the Cu3Sn type are replaced by steel dendrites in them.. The mass transfer of Fe, Ni, Co, and Al between the matrix and dendrites in these bronzes is studied. The dispersity of dendrites depending on the production method of the mentioned alloys can be increased tenfold, for example, with the vacuum casting method. The mechanical properties of the samples of the BrZhNKA type (σu = 372 MPa, δ = 25%, and ψ = 42%) when compared with the BrO10 prototype are higher: hardness σu by 50%, plasticity δ and ψ by a factor of 4–5, and wear resistance by an order of magnitude; the coefficient of friction is 20–30% lower. The fact of the substantial influence of dispersity of the dendritic component on the wearing intensity of the bronze of the BrZhNA type is established. For example, the wearing intensity with the transversal section of dendrites of 1 and 10 μm is 0.002 and 0.025, respectively, which is an order of magnitude lower, while the coefficient of friction remains herewith invariable; i.e., it is independent of the dispersity of dendrites. A whole complex of mechanical, process, and service properties makes it possible to consider the half-industrial approval of this new class of composite bronzes of the BrZhNKA type reinforced by dendrites of N12K7Yu maraging steel for sliding friction units substantiated and promising.