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Pyrite is considered the most common of the sulfide minerals. Pyrite's metallic luster and pale brass-yellow hue give it a superficial resemblance to gold, hence the well-known nickname of fool's gold. The color has also led to the nicknames brass, brazzle, and Brazil, primarily used to refer to pyrite found in coal.
Sep 28, 2015· Three forms of sulfur exist in coal: pyrite, sulfate and organic sulfur (Lu and Liu 1999).Pyrite plays a vital role in coal spontaneous combustion. The specific heat of pyrite is only one-third of that of coal; but with the same heat absorption, the temperature rise of pyrite is three times higher when compared to coal.
This includes the mining of coal, copper, gold, silver, zinc, lead, and uranium. The mineral pyrite, more commonly known as "fool's gold," is iron disulfide (FeS 2). Pyrite is one of the most important sulfides found in the waste rock of mines. When exposed to water and oxygen, it can react to form sulfuric acid (H 2 SO 4). The following ...
When bituminous coal is heated in an inert atmosphere (He) containing small amounts of oxygen at 393–455 °C, pyrite (FeS 2) in coal is partially converted to magnetite (Fe 3 0 4).The maximum amount of Fe 3 0 4 formed during the time of heating corresponds to 5–20% of the total pyrite present, depending on the coal sample. The magnetite forms as an outer crust on the pyrite grains.
When bituminous coal is heated in an inert atmosphere (He) containing small amounts of oxygen at 393-455 ??C, pyrite (FeS2) in coal is partially converted to magnetite (Fe304). The maximum amount of Fe304 formed during the time of heating corresponds to 5-20% of the total pyrite present, depending on the coal sample. The magnetite forms as an outer crust on the pyrite grains.
The sulfur content of coal treated in accordance with this method can be reduced by subjecting the treated coal to a low-strength magnetic field for moving at least 50% by weight of the pyrite from the coal although a smaller fraction, about 5 to 25%, of the pyrite is actually converted to magnetite.
Jan 28, 2012· The key difference between magnetite and hematite is that the iron in magnetite is in +2 and +3 oxidation states whereas, in hematite, it is only in +3 oxidation state.. Magnetite and hematite are minerals of iron. Both have iron in different oxidation states, and they are in the forms of iron oxides.Another important difference between magnetite and hematite is that the magnetite is black in ...
Aug 16, 2018· The thermal phase transition of pyrite from coal was studied using thermogravimetry and derivative thermogravimetric, infrared spectroscopy and X-ray diffraction (XRD). According to the XRD results, the phase transition of the pyrite starts at 350 °C, pyrrhotite and magnetite are intermediate products of the oxidation from pyrite to hematite.
Sulfide minerals, dominantly pyrite in a matrix of anhydrite, silica, and clay minerals, are present throughout Hole 1188A core. However, the modal percent sulfide rarely exceeds 5%, designated as the threshold for "sulfide rocks" for Leg 193 (see "Sulfide and Oxide Petrology" in the "Explanatory Notes" chapter for details). The threshold value was achieved in nine of the 23 cores recovered.
Jul 15, 2002· The changes in composition are followed by X-ray diffraction (XRD). The results indicated that the mechanism of wetting and adherence of molten pyrite over iron oxides is chemically induced: both di and mono iron sulphides interact with the oxide layer, changing the oxidation state of iron in oxide scale, from hematite to magnetite.
Pearson19 showed that, in the pyrite oxidation process, a minimum of 7 electron-transfer steps are necessary to describe completely the oxidation on the pyrite surface. Furthermore, it is well-known that different bacteria can catalyze the pyrite oxidation at a much rapid rate, making its mechanism even more complex.20
The presence of pyrite (FeS2) in coal can cause or contribute to several problems for the coal mining industry. These problems, which include spontaneous combustion, roof falls, floor heave, and accidental explosions in coal surface mining when ammonium nitrate-fuel oil (ANFO) explosives are used, result from pyrite oxidation.
Abstract. This document is the third quarterly status report on a project conducted at the High Temperature Gasdynamics Laboratory at Stanford University, Stanford, California and concerned with enhancing the transformation of iron pyrite to non-slagging species during staged, low-NO{sub x} pulverized coal (P.C.) combustion.
The fact that the magnetic properties of the pyrite grains are substantially increased by the magnetite crust suggests that pyrite can be separated from coal by use of a low magnetic field.
The decomposition of pyrite was investigated in a thermo‐balance. In neutral or reducing gases it decomposes between 550° and 700°C to volatile sulfur and ferrous sulfide.
Apr 28, 1987· Method for oxidation of pyrite in coal to magnetite and low field magnetic separation thereof . United States Patent 4661118 . Abstract: A method for increasing the magnetization of pyrite-containing pulverized coal comprises heating the coal in an atmosphere of inert gas, desirably nitrogen, containing 3 to 60 torr, preferably 12 to 16 torr ...
Decomposition and oxidation of pyrite. ... Fe2O3 and magnetite, Fe3O4) are the main products of the oxidation of pyrite. ... Pyrite present in coal undergoes oxidation at elevated temperatures to ...
Mechanisms of Pyrite Oxidation to Non-Slagging Species by Reginald E. Mitchell and A. E. Jacob Akanetuk ... A project was undertaken to characterize the oxidation of iron pyrite to the non-slagging species magnetite during pulverized coal combustion. ... the results of this project suggest that pyrite oxidation rates could be accelerated by ...
Magnetite forrnation by the reduction of hematite with iron under hydrothermal conditions Ar-lN Mnrrnnws Department of Geology, Hebrew Uniuersity Jerusalem, Israel Abstract The formation of magnetite by the reduction of hematite with iron in the presence of aqueous solution at 350-570"C, 1-2 kbar pressure, takes place by two reactions: (l) the
A project was undertaken to characterize the oxidation of iron pyrite to the non-slagging species magnetite during pulverized coal combustion. The work was aimed at defining the pyrite transformations responsible for the higher slagging propensity of staged, low-NO{sub x} pulverized coal combustor burners. With such burners, coal is injected into a reducing environment.
GEOCHEMICAL CHARACTERISATION OF PROCESS-TAILINGS, PYRITE-CONCENTRATE AND MAGNETITE-CONCENTRATE SAMPLES Implications for Process-Stream Management GRAEME CAMPBELL AND ASSOCIATES PTY LTD ... stoichiometry for the complete- oxidation of pyrite by O 2 to "Fe(OH) 3" and H 2SO 4, and
into 38-45µm to simulate the excluded pyrite in the coal ... Excluded pyrite: (1) hematite > magnetite; (2) hematite increases ... Because delayed oxidation of pyrite are expected, which will result in a longer duration of the melt phase and favors the deposition of iron phases on the waterwall.
In oxygen it oxidizes in two stages: between 445° and 520°C, it forms sulfur dioxide and ferrous sulfide: between 610° and 660°C. it forms more sulfur dioxide and hematite'In air Or with fast cycles, the reactions are overrun and do not show the two stages. Carbon dioxide reacts very slowly and gives magnetite.
Pyrite-pyrrhotine redox reactions in nature A. J. HALL Department of Applied Geology, University of Strathclyde, Glasgow G1 1XJ ABSTRACT. The origin in rocks of the common iron sulphides, pyrrhotine, Fe 1 xS and pyrite, FeS2 and their behaviour during geochemical processes is best con-
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