Some features of the formation of the oxidation zone of the Kokpatas ore field in Uzbekistan

Our article discusses the materials obtained by the authors in the study of the oxidation zone and primary ores of various deposits of the Kokpatassky ore field. The obtained research results confirm that the predominant part of gold remains in minerals replacing sulfides (pyrite, arsenopyrite) with the preservation of gold and its characteristic satellites in the oxidation products of sulfides (hedrogoethite, goethite and scorodite). Native gold belongs to fine and small size classes. The main concentrators of native gold are quartz, carbonate and oxidized forms of sulfides. Often, together with gold, arsenopyrite, scorodite, tetrahedrite, acanthite, electrums are noted.

High Efficient gasification in a Low-tar biomass (LTB) gasifier by Coupling with Inclined Nozzle and Combustor for Tar Reduction

A novel design of low-tar biomass (LTB) gasifier with an inclined nozzle in the pyrolysis zone and a separate combustor installed inside the partial oxidation zone has been designed, developed and tested, while maintaining an extremely low tar in the producer gas. The design process was focused on a swirling flow created by an inclined nozzle which allows a good mixing between gasifying air and pyrolysis gases in the pyrolysis zone. A separate combustor which has large annular and reverse flow zones with the help of swirl flow. The resulted mixing gases has sucked inside in to the combustor and burning the mixture with the help of induced thermal cracking in the partial oxidation zone. At an equivalence ratio of 0.35, the gasifier had a thermal capacity at 23.8 kW and a maximum cold gas efficiency of 93.1%. Using wood chips with a moisture content of 9–34%, the LTB gasifier had generated a producer gas at 7.4-27.14 mg/Nm3 with a lower heating value of 4.57–5.11 MJ/Nm3. The resulted producer gas can be piped directly to the internal combustion engine or a gas turbine at small to medium scale power plant in remote rural off-grid areas.

Oxidation Behavior of Inconel 740H Nickel Superalloy in Steam Atmosphere at 750 °C

The oxidation behavior of the nickel superalloy Inconel 740H was studied at 750 °C for 100, 250, 500, 1000, and 2000 h in a steam atmosphere. Microstructure observations were performed using scanning electron microscopes and scanning-transmission electron microscope. The phase identification of existing oxidation products was conducted by electron diffraction in transmission electron microscope. The obtained results showed that the microstructure of Inconel 740H was stable during the oxidation process. The kinetic data showed that the superalloy has the ability to form protective oxide layers that are characterized by good adhesion and no tendency to spallation during the test. The oxidation products were mainly composed of external and internal oxides mainly at grain boundaries. The oxides in the external layer were Cr2O3, MnTiO3,, and α-Al2O3 after 2000 h of oxidation. Internal oxides were α-Al2O3 and TiO2. The occurrence of discontinuities in the internal oxidation zone was also observed after 500 h of test. It was found that the thickness of the internal oxidation zone was greater than the thickness of the external oxide layer, which proves the strong tendency of the superalloy to form internal oxides after oxidation in the steam atmosphere.

Distribution Law of Three Spontaneous Combustion Zones in the Goaf Area of a Fully Mechanized Working Face under High Ground Temperature

To figure out the distribution law of three spontaneous combustion zones in the goaf area of fully mechanized working face under high ground temperature, this study took the 11501# fully mechanized mining face of Zhujixi Coal Mine as the research object, and employed software Fluent to perform numerical simulations on the O2 concentration distribution in the goaf; then, combining with the actual situations on the site, the high-location boreholes and grout holes of the roof gas drainage roadway of the 11501# working face were selected as measuring points to measure the O2 concentration changes in a few positions such as in middle part of the goaf, on the air intake side, and on the air return side. The results show that, the numerical simulation results were basically consistent with the field measurement results, in the middle part of the goaf, the scope of the oxidation zone was 26.4m-62m; on the air intake side, the scope of the oxidation zone was 32m-96m; on the air return side, the scope of the oxidation zone was 28.4m-91m. The research findings of this paper provided a scientific reference for formulating fire-prevention and fire-extinguishing technical plans for mines.

Assessment of the Possibility of Hydrometallurgical Processing of Low-Grade Ores in the Oxidation Zone of the Malmyzh Cu-Au Porphyry Deposit

The geochemical features of the ores present in the oxidation zone of the gold-copper Malmyzh mineral deposit are characterized. This deposit is located in the the Nanaian region of the Khabarovsk Territory in the Russian Federation, and a technological assessment of ores present was carried out. The initial gold content in the oxidized ore is 0.1–1.2 ppm, and the leachability of gold from different size fractions by hot cyanide revealed the fact that the ore is not refractory and characterized by increased cyanide consumption. The results demonstrated a high gold content in fine size fractions. Different leaching reagents were applied for oxidized ore testing. These reagents were used both for oxidative pretreatment and leaching process. Activation of solutions was carried out by electrolysis and UV radiation. Different reagent combinations were tested in laboratory with the highest gold recovery (94%) provided by the chloride system with peroxide-sulfuric pretreatment of the oxidized ore. The same reagent combination resulted in 91–94% gold recovery during the column leaching of crushed (−10 mm) ore.

Chemical and mineral composition of sulfide nodules from the Mikhaylovsky and Belousovsky ancient mines, Orenburg Gis-Urals

Cu-sulfde and rare Fe-sulfde nodules up to 2–5 cm in size are found in gray marl siltstones, which occur in a sequence of Permian sandstones of Orenburg Cis-Urals. The Cu-sulfde nodules are characterized by high Cu content (>20 %) and low contents of trace elements (Fe <1.2 %, As, Ag, V, and Pb <130 ppm). They are composed of Cu sulfdes (minerals of the chalcocite group and covellite) with minor barite and mottramite. The Cu sulfdes are transformed to malachite and, to a lesser degree, to chrysocolla and brochantite. The decomposition of Ag-bearing Cu sulfdes leads to the formation of a Ag sulfde. The Fe-sulfde nodules of the Belousovsky mine are composed of pyrite. In the oxidation zone, pyrite is replaced by ferrous opal; single grains of plumbogummite are associated with Fe hydroxides.

Investigating Magnetohydrodynamic Stability of an Aluminium Electrolytic Cell under Various Manufacturing Process Conditions

Mathematical simulation of industrial aluminium electrolytic cell operation allows us to predict and indicate the causes of magnetohydrodynamic (MHD) instability and bath level skewing, as well as investigate other features of the aluminium electrolysis process. In order to analyse the MHD stability of the electrolytic cell, we adapted a three-dimensional mathematical model that uses a multi-phase approach to describing the media (aluminium, electrolyte and gas) and treats the hydrodynamic, electromagnetic, thermal and electrochemical processes in the bath as interrelated. Our test calculations confirmed that the model is adequate and that the numerical solution proposed converges with sufficient accuracy. The paper describes our numerical investigation results concerning MHD stability of a multi-anode electrolytic cell when its thermal conditions and working space shape configuration change; our simulation included the metal-electrolyte phase interfaces and took into account the MHD instability developing when replacing burnt-out anodes. We estimated how various initial crust configurations affect the MHD stability. We investigated how the process parameters affect the working space shape in the bath, which is a dynamic object, same as the metal-electrolyte interface and the reverse oxidation zone surface. We specifically studied the way changes in potential affect the MHD stable shape of the working space in the bath. We show that varying the potential between any given pair of anodes can change the shape of the working space, that is, crust melts as potential increases, while lowering potential leads to further accretion. As this happens, we note that there is an increase in the vibration magnitudes of the liquid metal and the lower reverse oxidation zone boundary, but these variations are still within the range acceptable in terms of MHD stability of the electrolysis process

Six-months CrossFit training improves metabolic efficiency in young trained men (Seis meses de CrossFit mejora la eficiencia metabólica en jóvenes entrenados)

The objective was to analyse the effects of 6 months’ CrossFit on physical performance, metabolic efficiency, body composition, and biochemical parameters. Ten trained CrossFit practitioners were assessed before and after CrossFit training. Anthropometric measurements, biochemical parameters and physical performance parameters were assessed with functional and incremental tests. After 6 months of CrossFit, fat oxidation rate and energy percentage obtained from fat significantly increased (+221.43%; p=.043 and +222.39%; p=.043 respectively) with a concomitant decrease in carbohydrate oxidation rate and use of carbohydrates in maximal values (-47.35%; p=.043 and -34.41%; p=.043, respectively). In the maximal fat oxidation zone, maximal oxygen uptake increased (+20.3%; p=.043). Fat oxidation rate significantly increased with a concomitant decrease in carbohydrate oxidation rate (+62.75% vs -27.67%; p=.043). Lactate dehydrogenase values increased significantly (+27.13%; p= .043). In conclusion, 6 months of CrossFit improves the metabolic efficiency of the fat oxidation zone, without muscle damage.

JUSTIFICATION OF AIR FLOW SPEED IN THE OXIDATION AREA OF A GASIFIER IN CASE OF STRAW PELLETS USING

On the basis of the Bernoulli equation the dependence for determining the air flow rate in the oxidation zone of the gasifier was obtained. The obtained dependence makes it possible to theoretically establish the average speed and diameter of the air flow depending on the flow length. To check and clarify the obtained dependence for determining the air flow rate in the oxidation zone, the value of the total loss coefficient of the air flow rate in the volume of straw pellets, which are used as fuel for the gasifier, is experimentally established.