Mykola Saporoschenko

Mössbauer studies of iron in Lurgi gasification ashes and power plant fly and bottom ash

Iron Mossbauer spectroscopy and X-ray diffraction methods were applied to the study of a selection of ashes produced in a Lurgi gasification plant and fly ash from a pulverized coal combustion. The ashes contained hematite, magnetite, and goethite. Sixty percent or more of the iron in these ashes was in the oxide form, with the remainder present in mullite and other silicate phases. Iron was divalent in the latter, and present as both Fe+2 and Fe+3 in mullite. Ratios of Fe+2 and Fe+3 varied from 0.3 to 0.7. By comparison, a water-quenched molten bottom ash was free of iron oxides and contained only amorphous silicate phases with virtually all iron in the divalent state.

Mössbauer spectroscopic investigation of iron species in coal

Abstract A series of Herrin No. 6 coal and three coal-derived samples have been examined by Mossbauer spectroscopy. It is established that Mossbauer spectroscopy can be used to identify multiple iron species in a whole coal or an autoclaved char sample without the need to concentrate the minerals to enhance resolution. Our results indicate that there may be an association between the pyrite in raw coal and the coal matrix. This association appears to be broken down when the coal is heated to temperatures as low as 175 °C. It is also apparent that the iron sulphide present in the whole coal is converted to pyrite at these low temperatures. For our samples, the total quantity of iron species in different coal lithotypes is about the same, but they differ in their distributions. The fusain has the least amount of Fe 2+ species when compared to the vitrain or whole-coal sample used. At least two types of nonstoichiometric pyrrhotite are produced in the heat-treated samples. One of these pyrrhotites is unstable and contains dissolved sulphur which is apparently liberated as the temperature is increased.

Iron partitioning in oil shale of the Green River Formation, Colorado: A preliminary Mössbauer study

Abstract Oil shale of the Green River Formation (Eocene) in the Piceance Creek Basin, Colorado contains seven major iron-bearing minerals: pyrite, marcasite, pyrrhotite, Mg-siderite, Fe-dolomite, ankerite and Ca-ankerite. Only recently have workers recognized that these rocks contain large quantities of iron-bearing carbonate minerals. Preliminary Mossbauer spectroscopy analysis of four oil-shale and two marlstone samples from the Green River Formation shows that the dominant iron-bearing compound is usually an iron-carbonate mineral, generally Ca-ankerite or Fe-dolomite. The second most abundant iron-bearing phase is an iron sulphide, generally pyrite. In the samples studied, the iron partitioning is variable between the carbonate and sulphide phases. Lower grades of oil shale and marlstone also have an iron-bearing silicate phase, which is perhaps an iron-bearing phyllosilicate, possibly chlorite.

Mössbauer spectroscopic studies of the mineralogical changes in coal as a function of cleaning, pyrolysis, combustion and coalconversion processes

Abstract The mineralogical changes in a Perry County, Illinois coal from the Herrin (No. 6) Member due to cleaning, pyrolysis, combustion, and coal-conversion processes were studied. Mossbauer spectroscopy was used in tandem with X-ray diffraction to follow the changes in the forms of iron originally present in the coal resulting from processing. The chemistry of the pyrite conversion is less complex than expected. Iron does not become uniformly distributed in all possible minerals but tends to form simple products. Pyrrhotites along with spinel and hydrated ferrous sulphates are the primary mineral products found in coat liquefaction and pyrolysis process residues; while mullite, ferrous silicates and the iron oxides (hematite, geothite and magnetite) are the most abundant mineral products found in Lurgi gasification and power plant fly ashes. The detailed distribution of iron, however, is dependent upon conditions in the particular process equipment in which the coal is used and the conversion process in which it is used.

Kinetics and mechanisms of iron sulfide reductions in hydrogen and in carbon monoxide

The reduction of iron sulfides by hydrogen and by carbon monoxide has been studied using plug flow and thermogravimetric methods. The reactions were studied in the 523-723/sup 0/K temperature range and were found to be first-order processes. Plug flow studies were used to correlate reactions rates between pyrite and the gases as a function of the surface area of the pyrite. The rate of H/sub 2/S formation increases with the surface area of the pyrite sample. The results of thermogravimetric experiments indicate that the reactions consist of several steps. Rate constants for the pyrite reduction by H/sub 2/ and by CO were obtained. The activation energies increased with degree of reduction. Value of E/sub a/ were 113.2 (step I) and 122.5 kJ/mole (step II) for pyrite reduction with CO and 99.4 (step I), 122.4 (step II), 125.2 (step III), and 142.6 kJ/mole (step IV) for pyrite reduction with hydrogen.

Mössbauer studies of illites and heat-treated illite as related to coal-conversion processes

Abstract Mossbauer spectra of iron species in the following illites were studied: Grundite, Fithian, Minerva, and New Albany. Spectra of samples of Fithian illite heated at temperatures of 225, 700, and 1000 °C were also obtained. Analyses of these spectra provide Mossbauer parameter values of iron species in the illites and heat-transformed illite for comparison with similar species found in coals containing illites and in coal process residues derived from them. The illites contain both ferric and ferrous species. Mossbauer parameters for one of the ferric species, designated M(2), are virtually the same as those of pyrite. The two species are therefore difficult to distinguish from one another. Values of the concentration of pyrite in coals and shales may be inflated if the pyrite concentration is measured by Mossbauer spectroscopy. Mossbauer spectra of the heat-treated illite samples reveal changes in iron distribution, principally at the 700 and 1000 °C levels, where there are found three and six different iron species respectively. These changes are accompanied by reduction of ferric to ferrous iron. This process should be integrated into any assessment of the iron chemistry which accompanies coal-conversion processes.

Correlation of natural gas content to iron species in the New Albany shale group

Abstract Mossbauer parameters were obtained for four Illinois Basin shales and their corresponding

Methods for detecting the mobility of trace elements during medium-temperature pyrolysis

Abstract The mobility (volatility) of trace elements in coal during pyrolysis has been studied for distances of up to 40 cm between the coal and the trace element collector, which was graphite or a baffled solvent trap. Nineteen elements not previously recorded as mobile were detected.