scholarly journals Reduction of New Zealand Titanomagnetite Ironsand by Hydrogen Gas in a Fluidised Bed System

2021 ◽  
Author(s):  
◽  
Sigit Prabowo
Keyword(s):  
New Zealand ◽  
High Temperatures ◽  
Metallic Iron ◽  
Reduction Rate ◽  
Hydrogen Gas ◽  
Oxide Shell ◽  
Experimental Program ◽  
Reactor Wall ◽  
Pure Hydrogen ◽  
Fluidised Bed

<p>Titanomagnetite (TTM) ironsand has been used to produce steel in New Zealand (NZ) for about 40 years. However, the current steelmaking process in NZ produces high emissions of CO2 because it uses coal as a primary reducing agent. The fluidised bed (FB) process allows the use of pure hydrogen gas to reduce ironsand, and as a result, does not produce CO2 gas. However, for conventional hematite ores, reduction in a FB system is usually limited by the onset of particle sticking at temperatures ≳ 800°C. This thesis investigates the reduction of NZ TTM ironsand by hydrogen gas in the FB system with a key focus on ore sticking behaviour.  Initially, this thesis reports preliminary fluidisation tests by nitrogen and helium gases at room temperature, carried out to determine key fluidisation parameters for ironsand powder. From these results, a laboratory-scale experimental FB reactor has been designed and built for the hydrogen reduction study at high temperatures. A key feature of the reactor is a novel in-situ sampling system, which enables extraction of multiple samples during a single experimental run without interrupting operation of the FB.  Quantitative X-ray diffraction (q-XRD) has been used to determine the metallisation degree of partially reduced samples. Phase evolution during the reaction has also been analysed using q-XRD alongside scanning electron microscopy/energy dispersed spectroscopy (SEM/EDS). Additionally, the water vapour compositions in the exhaust gas were calculated from the q-XRD data and also measured in real-time using a high-temperature humidity sensor.   The effect of various parameters has been investigated within the FB reduction experiments: hydrogen gas concentrations, hydrogen gas flow rate, bed mass, particle size, and temperature. The results indicate that across the entire range of controlled studied, the FB reduction rate of TTM ironsand is simply controlled by the rate of hydrogen gas supply. Interestingly, there were no occurrences of the sticking phenomenon at any point during the reduction by hydrogen gas at high temperatures of up to 1000°C. Sticking appears to be prevented by the formation of a protective titanium-rich oxide shell around each particle during the initial reduction stage. Importantly, this shell remains present throughout the reduction process, and as a result, the reduction reaction proceeds rapidly to completion with a metallisation degree of ~93%.  The influence of temperature on the reaction progress has also been investigated. The reduction pathway appears to vary within different temperature regimes. At low temperatures (750°C-800°C), TTM is directly reduced to metallic iron and ilmenite without any evidence of wüstite phase. At ‘intermediate temperatures’ (850°C-900°C) small amount of short-lived wüstite is observed. Some of the amount of TTM appears to be reduced to wüstite, and some is directly reduced to metallic iron. At high temperatures (≥ 950°C), approximately half of the initial TTM phase is quickly reduced to wüstite. After that point, wüstite is then reduced to metallic iron whilst the reduction of TTM stops. This is due to the enrichment of Ti species in TTM phase, which stabilises TTM crystal. Once wüstite has been fully reduced, the reduction of TTM then resumes.   Throughout the entire experimental program for this thesis, particle sticking was observed to occur only under two specific sets of experimental conditions. These were: reduction by 100% H2 gas at 1050°C (case A) and reduction by 7.5 mol.% H2O – 92.5 mol.% H2 at 950°C (case B). In both cases, sticking occurred as a sinter which nucleated at the reactor wall surface, while most particles remained fluidised as loose powder. The mechanism of these sticking cases has been analysed by XRD and SEM. The results suggest that silica from the quartz reactor wall reacted and bonded with Fe from particles to nucleate the initial sinter.   In summary, the findings in this thesis show that the hydrogen-FB process is highly effective in reducing NZ ironsand to a direct reduced iron (DRI) product. These findings open up the possibility of developing a new industrial FB technology for the direct reduction of NZ TTM ironsand, with extremely low CO2 emissions.</p>

scholarly journals Reduction of New Zealand Titanomagnetite Ironsand by Hydrogen Gas in a Fluidised Bed System

2021 ◽  
Author(s):  
◽  
Sigit Prabowo
Keyword(s):  
New Zealand ◽  
High Temperatures ◽  
Metallic Iron ◽  
Reduction Rate ◽  
Hydrogen Gas ◽  
Oxide Shell ◽  
Experimental Program ◽  
Reactor Wall ◽  
Pure Hydrogen ◽  
Fluidised Bed

<p>Titanomagnetite (TTM) ironsand has been used to produce steel in New Zealand (NZ) for about 40 years. However, the current steelmaking process in NZ produces high emissions of CO2 because it uses coal as a primary reducing agent. The fluidised bed (FB) process allows the use of pure hydrogen gas to reduce ironsand, and as a result, does not produce CO2 gas. However, for conventional hematite ores, reduction in a FB system is usually limited by the onset of particle sticking at temperatures ≳ 800°C. This thesis investigates the reduction of NZ TTM ironsand by hydrogen gas in the FB system with a key focus on ore sticking behaviour.  Initially, this thesis reports preliminary fluidisation tests by nitrogen and helium gases at room temperature, carried out to determine key fluidisation parameters for ironsand powder. From these results, a laboratory-scale experimental FB reactor has been designed and built for the hydrogen reduction study at high temperatures. A key feature of the reactor is a novel in-situ sampling system, which enables extraction of multiple samples during a single experimental run without interrupting operation of the FB.  Quantitative X-ray diffraction (q-XRD) has been used to determine the metallisation degree of partially reduced samples. Phase evolution during the reaction has also been analysed using q-XRD alongside scanning electron microscopy/energy dispersed spectroscopy (SEM/EDS). Additionally, the water vapour compositions in the exhaust gas were calculated from the q-XRD data and also measured in real-time using a high-temperature humidity sensor.   The effect of various parameters has been investigated within the FB reduction experiments: hydrogen gas concentrations, hydrogen gas flow rate, bed mass, particle size, and temperature. The results indicate that across the entire range of controlled studied, the FB reduction rate of TTM ironsand is simply controlled by the rate of hydrogen gas supply. Interestingly, there were no occurrences of the sticking phenomenon at any point during the reduction by hydrogen gas at high temperatures of up to 1000°C. Sticking appears to be prevented by the formation of a protective titanium-rich oxide shell around each particle during the initial reduction stage. Importantly, this shell remains present throughout the reduction process, and as a result, the reduction reaction proceeds rapidly to completion with a metallisation degree of ~93%.  The influence of temperature on the reaction progress has also been investigated. The reduction pathway appears to vary within different temperature regimes. At low temperatures (750°C-800°C), TTM is directly reduced to metallic iron and ilmenite without any evidence of wüstite phase. At ‘intermediate temperatures’ (850°C-900°C) small amount of short-lived wüstite is observed. Some of the amount of TTM appears to be reduced to wüstite, and some is directly reduced to metallic iron. At high temperatures (≥ 950°C), approximately half of the initial TTM phase is quickly reduced to wüstite. After that point, wüstite is then reduced to metallic iron whilst the reduction of TTM stops. This is due to the enrichment of Ti species in TTM phase, which stabilises TTM crystal. Once wüstite has been fully reduced, the reduction of TTM then resumes.   Throughout the entire experimental program for this thesis, particle sticking was observed to occur only under two specific sets of experimental conditions. These were: reduction by 100% H2 gas at 1050°C (case A) and reduction by 7.5 mol.% H2O – 92.5 mol.% H2 at 950°C (case B). In both cases, sticking occurred as a sinter which nucleated at the reactor wall surface, while most particles remained fluidised as loose powder. The mechanism of these sticking cases has been analysed by XRD and SEM. The results suggest that silica from the quartz reactor wall reacted and bonded with Fe from particles to nucleate the initial sinter.   In summary, the findings in this thesis show that the hydrogen-FB process is highly effective in reducing NZ ironsand to a direct reduced iron (DRI) product. These findings open up the possibility of developing a new industrial FB technology for the direct reduction of NZ TTM ironsand, with extremely low CO2 emissions.</p>

scholarly journals Observations on the theory of respiration

1837 ◽  
Vol 3 ◽  
pp. 334-335
Keyword(s):  
Carbonic Acid ◽  
Venous Blood ◽  
Hydrogen Gas ◽  
The Body ◽  
Pure Hydrogen ◽  
Atmospheric Air ◽  
Acid Gas ◽  
Arterial Blood ◽  
Dark Colour ◽  
Oxygen Gas

From the fact that no carbonic acid gas is given out by venous blood when that fluid is subjected to the action of the air-pump, former experimentalists had inferred that this blood contains no carbonic acid. The author of the present paper contends that this is an erroneous inference; first, by showing that serum, which had been made to absorb a considerable quantity of this gas, does not yield it upon the removal of the atmospheric pressure; and next, by adducing several experiments in proof of the strong attraction exerted on carbonic acid both by hydrogen and by oxygen gases, which were found to absorb it readily through the medium of moistened membrane. By means of a peculiar apparatus, consisting of a double-necked bottle, to which a set of bent tubes were adapted, he ascertained that venous blood, agitated with pure hydrogen gas, and allowed to remain for an hour in contact with it, imparts to that gas a considerable quantity of carbonic acid. The same result had, indeed, been obtained, in a former experiment, by the simple application of heat to venous blood confined under hydrogen gas; but on account of the possible chemical agency of heat, the inference drawn from that experiment is less conclusive than from experiments in which the air-pump alone is employed. The author found that, in like manner, atmospheric air, by remaining, for a sufficient time, in contact with venous blood, on the application of the air-pump, acquires carbonic acid. The hypothesis that the carbon of the blood attracts the oxygen of the air into the fluid, and there combines with it, and that the carbonic acid thus formed is afterwards exhaled, appears to be inconsistent with the fact that all acids, and carbonic acid more especially, impart to the blood a black colour; whereas the immediate effect of exposing venous blood to atmospheric air, or to oxygen gas, is a change of colour from a dark to a bright scarlet, implying its conversion from the venous to the arterial character: hence the author infers that the acid is not formed during the experiment in question, but already exists in the venous blood, and is extracted from it by the atmospheric air. Similar experiments made with oxygen gas, in place of atmospheric air, were attended with the like results, but in a more striking degree and tend therefore to corroborate the views entertained by the author of the theory of respiration. According to these views, it is neither in the lungs, nor generally in the course of the circulation, but only during its passage through the capillary system of vessels, that the blood undergoes the change from arterial to venous; a change consisting in the formation of carbonic acid, by the addition of particles of carbon derived from the solid textures of the body, and which had combined with the oxygen supplied by the arterial blood: and it is by this combination that heat is evolved, as well as a dark colour imparted to the blood. The author ascribes, however, the bright red colour of arterial blood, not to the action of oxygen, which is of itself completely inert as a colouring agent, but to that of the saline ingredients naturally contained in healthy blood. On arriving at the lungs, the first change induced on the blood is effected by the oxygen of the atmospheric air, and consists in the removal of the carbonic acid, which had been the source of the dark colour of the venous blood; and the second consists in the attraction by the blood of a portion of oxygen, which it absorbs from the air, and which takes the place of the carbonic acid. The peculiar texture of the lungs, and the elevation of temperature in warm-blooded animals, concur in promoting the rapid production of these changes.

Phase transformations during fluidized bed reduction of New Zealand titanomagnetite ironsand in hydrogen gas

2021 ◽  
pp. 117032
Author(s):  
SigitW. Prabowo ◽  
Raymond J. Longbottom ◽  
Brian J. Monaghan ◽  
Diego del Puerto ◽  
Martin J. Ryan ◽  
...  
Keyword(s):  
New Zealand ◽  
Phase Transformations ◽  
Fluidized Bed ◽  
Hydrogen Gas

scholarly journals Slow Strain Rate Testing of Ti-6Al-4V Alloy in Hydrogen Gas at High Pressures and High Temperatures

2017 ◽  
Vol 58 (6) ◽  
pp. 886-891 ◽  
Author(s):  
Kenichi Koide ◽  
Toshirou Anraku ◽  
Akihiro Iwase ◽  
Hiroyuki Inoue
Keyword(s):  
Strain Rate ◽  
High Temperatures ◽  
High Pressures ◽  
Hydrogen Gas ◽  
Slow Strain Rate ◽  
Slow Strain Rate Testing ◽  
Rate Testing

Effects of hydrogen on the microstructure and microchemistry of Ti3Al – Nb intermetallics at high temperatures and high pressures

1996 ◽  
Vol 11 (9) ◽  
pp. 2186-2197 ◽  
Author(s):  
H. Z. Xiao ◽  
I. M. Robertson ◽  
H. K. Birnbaum
Keyword(s):  
Solid Solution ◽  
High Temperatures ◽  
High Pressures ◽  
Chemical Potential ◽  
Substitutional Solid Solution ◽  
Hydrogen Gas ◽  
Solid Solution Phase ◽  
Face Centered Cubic ◽  
Fine Grained ◽  
Surrounding Matrix

The microstructural and microchemical changes produced in a Ti–25Al–10Nb–3V–1Mo alloy (at. %) by charging at high temperatures in high pressures of hydrogen gas have been studied using transmission electron microscopy (TEM) and x-ray methods. Hydrides incorporating all of the substitutional solutes that formed during charging have a face-centered cubic (fcc) structure and exhibit either a plate or fine-grained morphology. With increasing hydrogen content, the size of the hydrides decreases and their microchemistry changes as they approach the stable binary hydride, TiH2. Rejection of substitutional solute elements from the hydride produces changes in the microchemistry, and consequently in the crystal structure, of the surrounding matrix. In alloys containing 50 at. % H, this solute redistribution results in the formation of an orthohombic substitutional solid solution phase containing increased levels of Nb. The driving force of this redistribution of solutes is the reduction in the chemical potential of the system as the amount of the most stable hydride, TiH2, forms. The hydrides reverted to a solid solution on annealing in vacuum at 1073 K, and the original microchemistry of the alloy was restored. Reversion from the hydride structure to the original α2 ordered DO19 structure proceeds via a disordered HCP phase.

scholarly journals Laser-Plasma and Self-Absorption Measurements with Applications to Analysis of Atomic and Molecular Stellar Astrophysics Spectra

Atoms ◽  
2019 ◽  
Vol 7 (3) ◽  
pp. 63 ◽  
Author(s):  
Christian G. Parigger ◽  
Christopher M. Helstern ◽  
Ghaneshwar Gautam
Keyword(s):  
Molecular Species ◽  
Laser Plasma ◽  
Emission Spectra ◽  
Hydrogen Gas ◽  
Spectral Radiance ◽  
Pure Hydrogen ◽  
Line Profiles ◽  
Emission Data ◽  
Balmer Series ◽  
Gaseous Mixtures

This work discusses laboratory measurements of atomic and diatomic molecular species in laser-plasma generated in gases. Noticeable self-absorption of the Balmer series hydrogen alpha line occurs for electron densities of the order of one tenth of standard ambient temperature and pressure density. Emission spectra of selected diatomic molecules in air or specific gaseous mixtures at or near atmospheric pressure reveal minimal plasma re-absorption. Abel inversion of the plasma in selected gases and gas mixtures confirm expansion dynamics that unravel regions of atomic and molecular species of different electron temperature and density. Time resolved spectroscopy diagnoses self-absorption of hydrogen alpha and hydrogen beta lines in ultra-high pure hydrogen gas. Radiation from a Nd:YAG laser device induces micro-plasma for pulse widths in the range of 6–14 ns, energies in the range of 100–800 mJ, and peak irradiances of the order 1–10 TW/cm 2 . Atomic line profiles yield electron density and temperature from fitting of line profiles to wavelength and sensitivity corrected spectral radiance data. Analysis of measured diatomic emission data yields excitation temperature of primarily molecular recombination spectra. Applications of the laboratory experiments extend to investigations of stellar astrophysics white dwarf spectra.

Uranium Hydride Formation Study as Observed by Scanning Surface Potential Imaging

2006 ◽  
Vol 986 ◽  
Author(s):  
Marilyn E. Hawley ◽  
Mary Ann Hill ◽  
Yongqiang Wang ◽  
Roland K. Schulze
Keyword(s):  
Surface Potential ◽  
Nuclear Power ◽  
Scanning Force Microscopy ◽  
Hydrogen Gas ◽  
Pure Hydrogen ◽  
Force Microscopy ◽  
Chemical Impurities ◽  
Conventional Weapons ◽  
Scanning Force ◽  
Materials Failure

AbstractUranium is an extremely important material for commercial and military applications (i.e. nuclear power, nuclear weapons, conventional weapons, and armor systems) and, like a number of other materials, is vulnerable to corrosion by environmental gases that affect their properties, leading to component degradation, shortened lifetimes and materials failure. For uranium this is particularly true in the case of corrosion by hydrogen. A fundamental understanding of the corrosion process at the nucleation stage is of critical importance. The goal of this work is to study the role of common chemical impurities in uranium with initiation sites for the formation of destructive hydride blisters. Samples were implanted with various ions, annealed under vacuum at 200°C, than exposed to one atm of ultra-pure hydrogen. Scanning force microscopy surface potential imaging was used to characterize the structure and corresponding electrical properties of polycrystalline uranium surfaces that resulted from the implantation of different suspect atoms after exposure to hydrogen gas. Surface potential images revealed features related to different oxide structures and hydride spots/blisters as well as other features not obvious in the corresponding topograph. In the surface potential images, blisters appear as bright (higher potential) features in sharp contrast to the uranium oxide background. Often a possible inclusion was observed in the center of a blister. Blister formation did not appear to correlate with implantation of any specific specie, however, distinct differences were seen between implanted and non implanted sides of the same sample.

A Thermodynamic Analysis of Compressing Hydrogen for Storage

2006 ◽  
Author(s):  
Clinten D. Lingel
Keyword(s):  
Energy Source ◽  
Internal Combustion Engines ◽  
Hydrogen Gas ◽  
Methane Reforming ◽  
Pure Hydrogen ◽  
Combustion Engines ◽  
End User ◽  
Storage Container ◽  
Real Issue ◽  
Formed Hydrogen

Storing hydrogen gas under pressure to provide an energy source for fuel cells or internal combustion engines is a real issue that must be addressed. Diatomic hydrogen does not occur naturally and therefore, must be made through electrolysis, methane reforming or some other process. From the production of pure hydrogen to the final end user, the entire cycle must be considered. Once formed, hydrogen will need to be compressed to a storage container. A hydrogen based transportation system will be both an economic and engineering challenge.

Behavior of Cement Composites Loaded by High Temperature

2015 ◽  
Vol 824 ◽  
pp. 121-125
Author(s):  
Veronika Špedlová ◽  
Dana Koňáková
Keyword(s):  
High Temperature ◽  
Portland Cement ◽  
High Temperatures ◽  
Experimental Program ◽  
Mechanical And Thermal Properties ◽  
Cement Composites ◽  
Basalt Fibers ◽  
Coefficient Of Thermal Conductivity ◽  
Aluminous Cement ◽  
Better Than

In this paper, there are summarized the results of an experimental program focused on basic, mechanical and thermal properties of cement composites according to the high – temperature loading. Four different materials were studied, which differed in used kind of cement and amount of fibers. As a matrix for studied composites the aluminous cement was chosen because of its resistance in high temperature. For a comparison the Portland cement was also tested. The second main ingredient used to provide better resistance in high temperatures - the basalt aggregate, was mixed in every specimen. The basalt fibers were chosen for two of the measured samples, remaining two ones were tested without fibers. The obtained data in this presented analyses show that the application of the aluminous cement leads to increase (depending on temperature) of porosity, which is the cause of decreasing of the coefficient of thermal conductivity. It can seems, that these cement composites will have low mechanical strength in high temperatures, but because of better sintering, the aluminous cement keeps its strength in high temperatures better than Portland cement.

Preparation and Sintering Behavior of Fe Nanopowders Produced by Plasma Arc Discharge Process

2007 ◽  
Vol 534-536 ◽  
pp. 585-588 ◽  
Author(s):  
Chul Jin Choi ◽  
Ji Hun Yu
Keyword(s):  
Sintering Temperature ◽  
Arc Discharge ◽  
Hydrogen Gas ◽  
Shell Structures ◽  
Oxide Shell ◽  
Sintering Behavior ◽  
Discharge Process ◽  
Plasma Arc ◽  
Densification Rate ◽  
Plasma Arc Discharge

The nano-sized Fe powders were prepared by plasma arc discharge (PAD) process using pure Fe rod. The microstructure of the prepared nanopowders was evaluated and the effect of hydrogen gas in the chamber atmosphere was investigated. In addition, the sintering behavior of nanosized Fe powders was analyzed and compared with those of conventional micron powders. The prepared Fe nanopowders had nearly spherical shapes and consisted of metallic core and oxide shell structures. In PAD nanopowder sintering, the higher volume shrinkage at low sintering temperature was observed due to the reduction of surface oxide. The PAD nanopowders showed 6 times higher densification rate and more significant isotropic shrinkage behavior than those of micron sized Fe powders.

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