Materials and Energy Balance of E-Waste Smelting—An Industrial Case Study in China

The application of Nerin Recycling Technologies (NRT) in electronic waste (E-waste) smelting was introduced in this study, and the material and energy balance was calculated based on the practical data with the METSIM software (METSIM International, USA). The main results are as follows: (1) the optimized processing parameters in the NRT smelting practice were the E-waste feeding rate of 5.95 t/h, oxidation smelting duration of 3.5 h, reduction smelting duration of 0.5 h, oxygen enrichment of 21–40 vol.%, oxygen consumption of 68.06 Nm3/ton raw material, slag temperature of 1280 °C, slag composition: Fe/SiO2 mass ratio of 0.8–1.4, CaO, 15–20 wt.%, Cu in crude copper ≥ 95 wt.%, Cu in slag, 0.5 wt.%, recovery of Cu, Au, and Ag ≥ 98%; (2) 98.49% Au, 98.04% Ag, 94.11% Ni, and 79.13% Sn entered the crude copper phase in the smelting process, 76.73% Pb and 67.22% Zn volatilized to the dust phase, and all halogen elements terminated in the dust and off-gas; (3) total heat input of the process was 79,480 MJ/h, the energy released by chemical reactions accounted for 69.94% of the total, and heat from fuels burning accounted for 33.04%. The energy brought away by the off-gas was 38,440 MJ/h, which was the largest part in heat output. The heat loss with the smelting slag accounted for 28.47% of the total.

The Micro-Tribological Behavior and Friction Mechanism of the Graphite/Cu Composites and Copper-coated Graphite-graphite/Cu Composites

The ring-block tribological behavior of the graphite/Cu(G/Cu) composites and copper-coated graphite-graphite/Cu(CCG-G/Cu) were studied by observing the friction coefficient,wear rate,microstructure and morphogoly of the composites after friction experiments.SEM and TEM were used to character the micro-morphology and micro-structure of debris,friction surface and friction cross section of the composites.The results show that adding 20wt% copper-coated graphite could reduced the friction coefficient and wear rate of the composites.The micro-morphology and micro-structure show that the copper phase are undergo oxidation and plastic deformation under cyclic stress,results in abundant deformation area in copper-rich zones.Interlaminar shedding and intramolecular tearing occurs in graphite phase,and then laid flat on the friction surface,forming a friction film with higher integrity and reducing the friction coefficient of the composites.The TEM images of the friction cross section show that deformation zone is mainly composed of accumulation zone,drag zone and carbon film.The simulation of the friction process shows that the initial stage is mainly dominated by abrasive wear and adhesive wear.With the progress of the experiment,the exposed copper phase is oxidized and oxidative wear occurs,graphite is shed and transferred to the contact surface.In the later stage of the experiment,a complete friction film with high graphite content is formed on the contact surface,which is mainly dominated by fatigue wear.

Evolution of microstructure and wear-friction behavior of W-30 wt.% Cu nanocomposite produced via a mechanochemical synthesis route

W-30 wt.% Cu nanocomposites were prepared by chemical reduction of a ball-milled WO3-CuO powder mixture under a hydrogen atmosphere. The prepared samples were analyzed by means of X-ray diffraction, transition electron microscopy, scanning electron microscopy and energy dispersed spectroscopy. Microstructural studies revealed higher density of the composite sintered at 1300 °C compared to 1 050 °C and 1 150 °C due to activated liquid phase sintering as well as the solution-reprecipitation mechanism at 1300 °C. Density and hardness of the W-Cu composite samples measured in the range of 87.5- 97.3 g cm-3 and 22 - 63 Rockwell A, respectively. It was also found that the wear mechanism of the composite includes the following steps: chipping of tungsten particles, plastic deformation of copper phase and formation of some Cu-free pores and micro-cracks, pulling out of tungsten particles and plastic strain and deformation of tungsten particles and formation of a mechanically mixed layer on the surface.

Study on the extraction of metals from tails of flotation enrichment of copper sulfide ores

Flotation processing of copper-pyrite ores is accompanied by the formation of flotation tailings containing 0.2-0.7 % wt Cu and 0.6-1.4 g/t Au. Deeper extraction of these components into commercial products is of practical interest. The possibility of additional recovery of copper and gold using the example of tailings from the current processing of PJSC “Gaysky GOK” was studied. It was shown that thin emulsion impregnation of chalcopyrite (less than 10 μ) in pyrite prevented the copper and gold from being extracted from the tailings by ore dressing methods. A scheme for the deep extraction of valuable components, based on the preliminary concentration of gold and copper by pyrite flotation, was proposed. About 84.5% of gold and 60.9% of copper were extracted into pyrite concentrate, while the gold content in the chamber product was 0.25 g/t. The increase in the extraction of copper was impossible due to nature of copper phase in chamber product that consisted mainly of copper oxides. Further processing of the pyrite concentrate can be accomplished by the way based on oxidative roasting (550-600 °C), with subsequent sulfuric acid leaching of copper from the calcine, washing and cyanidation of washed cake. Acid leaching is recommended to be done without external heating with solutions of 10-20 g/l of sulfuric acid. Copper was precipitated from leachates by cementation with iron powder in the form of copper concentrate (22-32 % wt Cu), then the gold-containing solution is processed to produce ligature gold. The optimal conditions for the cyanidation of the calcine were determined as follows, L:S = 2, the initial concentration of NaCN was 2 g/l, the duration of cyanidation was 2 hours The possibility of achieving end-to-end extraction of 66% of gold, and 45% of copper in commercial products is shown. The proposed scheme makes it possible to reduce the specific consumption of NaCN during cyanidation from 2.5-2.8 to 0.8 kg/t of tailings. It is assumed to gain sulfuric acid from the burning gases.

Effect of Gallium Loading on Reducibility and Dispersion of Copper-Based Catalyst

The effect of gallium-promoted copper-based catalysts has been investigated in connection with the characteristic of the active copper phase. CuO-ZnO-Ga2O3catalysts with different gallium loadings were prepared using oxalate co-precipitation method. The effects of gallium loading on the properties of catalysts were studied by means of X-ray diffraction (XRD), transmission electron microscopy (TEM) and temperature-programmed reduction (TPR). The dispersion and metal area of copper were also determined by dissociative nitrous (N2O) adsorption technique conducted on a metal dispersion analyzer (BELCAT). The TPR profiles showed that the presence of two different reduction regions in the CuO-ZnO catalysts can be attributed to the reduction of highly dispersed copper oxide species (reduced at 246 °C) and bulk-like CuO (reduced at above 390 °C). By contrast, the only low-temperature reduction peak was presented in the TPR profiles after the Ga2O3loading was higher than 4 wt%. With the same molar ratio (Cu/Zn = 2:1), the reducibility of CuO-ZnO-Ga2O3was found to be more facile than CuO-ZnO due to the lower copper oxide crystallite sizes of gallium-promoted catalysts. Higher Ga2O3loadings resulted in an increase in both copper dispersion and metal surface area of all the catalysts studied in good agreement with the reduction behaviors in the TPR profiles, although all the gallium-promoted catalysts were slightly different for the reducibility.

Realization of a highly effective Pd–Cu–Clx/Al2O3 catalyst for low temperature CO oxidation by pre-synthesizing the active copper phase of Cu2Cl(OH)3

The Pd–Cu–Clx/Al2O3 catalysts (PCC) were prepared by a two-step impregnation (TI) method in organic solvent, wet impregnation (WI) method and NH3 coordination-impregnation (CI) method.