Where (z_{a}) is the valence of the metallic element forming the oxide scale (i.e. 3 for chromia and alumina), 16 is the atomic mass of oxygen, and (k_{{text{p}}}) is the parabolic oxidation rate constant in g 2 cm −4 s −1.. Surface oxidation of polycrystalline Ni-base superalloys has been shown to reduce fatigue and creep lifetimes as a result of crack initiation at the brittle …
Oxidation kinetics of high purity nickel, as well as the nonstoichiometry and chemical diffusion in nickel oxide have been studied as a function of temperature (1373–1673 K) and oxygen pressure (10–10 5 Pa) using microthermogravimetric techniques. In order to eliminate the possible participation of grain boundary diffusion in scale growth at lower temperatures, the …
The pressure oxidation of low-grade nickel sulfide concentrate with high iron sulfides content generates significant amounts of sulfuric acid that must be neutralized. This acid can be utilized to leach metal values from ores …
Oxidation kinetics of high purity nickel, as well as the nonstoichiometry and chemical diffusion in nickel oxide, have been studied as a function of temperature (1373-1673 K) and oxygen …
High temperature pressure oxidation of a low-grade nickel concentrate was examined to demonstrate the potential benefits and shortcomings of this approach. The high iron sulfide content ensured that acid …
A STUDY OF OXIDATION KINIQICS OF NICKEL METAL IN FLOWING AIR AND OXYGEN-NITROGEN MI-S By D. J. Progar and B. W. Langley Research Center A study was made of the oxidation kinetics of nickel metal sheet in flowing air and in oxygen-nitrogen mixtures of varying composition.The study covered the temperatures 1500° F, 17>0° F, 2000° F, 2250° F, …
3.2. Sulfuric acid pressure oxidation processes. Sulfuric acid pressure oxidation processes have been commercially employed since the 1980s for processing of Ni-Cu mattes, zinc concentrates and refractory gold concentrates (Berezowsky et al. Citation 1991) and have seen limited use in the processing of nickel sulfide concentrates. The sulfuric ...
Oxidation kinetics of high purity nickel, as well as the nonstoichiometry and chemical diffusion in nickel oxide have been studied as a function of temperature (1373–1673 K) and …
Pressure oxidation (POX) is a well-established method for processing sulphide material containing refractory precious and base metals . POX typically takes place in a horizontal multi-compartment agitated pressure vessel at a temperature of 150–230 °C depending on the application. Sulphide minerals are broken down, reacting with oxygen and ...
TiO 2 is mainly formed on the surface of nickel-based alloys during high-temperature oxidation with low-oxygen partial pressure conditions in S-CO 2 environments. In some cases, the TiO 2 layer is observed on the top of the chromia [ 44 ].
Low pressure oxidation studies of Ni-18%Cr alloy were carried out at temperatures of 500–600°C for very brief periods. Detailed XPS, AES, SEM, and TEM studies identified four stages in the initial oxidation. These are: (1) formation of a mixed nickel-chromium oxide overlayer; (2) growth of submicron-sized oxide nodules; (3) development of dark "hole-like" patches on the surface; …
The pressure oxidation of nickel sulfide concentrates and nick-eliferous pyrrhotite concentrates has been extensively researched and processes have been both piloted and commer-cially deployed which were described in the first part of this review. Sulfuric acid pressure oxidation processes for the treat-
Alternatively, a process has been conceived to pressure oxidize nickel sulfide flotation concentrate to produce mixed hydroxide precipitate (MHP) containing nickel and …
primary alloy constituent, the fast outward diffusion of nickel from alloy substrate coupled with the rapid growth rate of nickel oxide, (&104 faster than a-Al 2O 3 [10, 11]), nickel oxide formed (region I). Since the equilibrium dissociation pressure of nickel oxide is 8 9 10-9 atm., formation continued until the pO 2 reached this value,
oxidation o f Fe +2 to Fe +3 was undertaken using 40 m l of 35 % ... This paper describes the experimental findings of the extraction of nickel and cobalt by high pressure acid leaching (HPAL) of ...
The high temperature oxidation of nickel has been investigated in air under atmospheric pressure in the temperature range 600–900°C. The oxidation kinetic curves deviate from the parabolic law for temperatures over 800°C. The observation of scale morphologies and the use of two stage oxidation experiments under 16O2/18O2 atmospheres showed that oxygen transport through …
McDonald et al. treated a high iron–low nickel concentrate by pressure oxidation at 250 °C, and the extraction of base metals from such nickel sulfide concentrates is rapid. The controlled oxidation of feed sulfide minerals demonstrated that the hydrothermal oxidation of pentlandite occurs via violarite and subsequently vaesite. Under the ...
The global production of nickel is largely based on nickel sulphide minerals (60%) with pyrometallurgical converting into matte, followed by a hydrometallurgical process with unit processes such as leaching (atmospheric and/or pressure), iron removal, solvent extraction (SX) for cobalt and nickel and final product recovery, typically by electrowinning (EW), hydrogen …
Pressure Oxidation of Nickel Concentrates to Prepare Mixed Hydroxide Precipitate: An Alternate Battery Supply Chain Feed Source ... The NiCo Sulphide is leached under pressure oxidation (POX) conditions in a continuously operating, five compartment autoclave. The autoclave retention time is approximately 2.5 h and leaching is conducted at ...
This paper summarizes on some of the extensive experimental data and corresponding models suggested to account for the oxidation mechanism of Ni in the temperature range 500–1400 °C. In addition it reports on in-house experimental data from investigations related to the oxidation of high-purity Ni from 500 to 1300 °C in the oxygen pressure range …
Examples of this include pressure oxidation (POX) of sulfide ores and concentrates, high-pressure acid leaching (HPAL) of nickel laterites, and wet-air oxidation of organics. Both batch and continuous reactors are available at Hazen for developing high-temperature processes. Hazen's engineers have assisted clients in developing POX processes for refractory gold ores, metals
Undoped NiO. Nickel oxide (Ni 1− δ O) is a metal-deficient p-type semiconductor which is thermodynamically stable in a large temperature (T) and oxygen partial pressure (p O 2) range. 20 Nickel vacancies and electron holes (h˙) are …
out the technique of measurement of metal oxidation rates using a metal nickel for which there was a relatively large amount of reliable kinetic data and for which an accepted mechanism …
Nickel concentrate · Pressure oxidation · Mixed hydroxide precipitate 1 Introduction 1.1 Background Nickel sulfide minerals found in nature can be concentrated using conventional mineral processing methods. Nickel concentrates often contain iron sulfide minerals such as pyrrhotite or pyrite, and copper sulfide minerals such as chalcopyrite
The successful commercialization of a pressure oxidation (POX) process for recovering metal values, including gold, copper, zinc, nickel and molybdenum, is the result of a carefully planned ...
The acid pressure leach for nickel-cobalt sulphides was licensed to the Finnish nickel company, Outokumpu, in 1967. ... Pressure oxidation of refractory gold ores finally came into its own in the 1980s as a healthy gold price encouraged the exploitation of …
The pressure oxidation of low-grade nickel sulfide concentrate with high iron sulfides content generates significant amounts of sulfuric acid that must be neutralized. This acid can be utilized to ...
In this paper, a variety of experimental tracer diffusivities of Ni and O in nickel oxide in the literature were first assessed. Two groups of atomic mobilities including bulk and short …
The successful commercialization of a pressure oxidation (POX) process for recovering metal values, including gold, copper, zinc, nickel and molybdenum, is the result of a carefully planned development program.
The high matte nickel firstly is ground in the ball mill, secondly leached with normal pressure under strong oxidation conditions, and then is conducted for oxidation leaching in the autoclave, so that the copper, nickel, and cobalt are completely dissolved and the iron is precipitated in the form of hematite. ... Li G-C (2005) The pressure ...
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