scholarly journals A Study on the Reduction Behavior of FeO by Analyzing Pore Characteristics Using the Labyrinth Coefficient at High Temperature

Metals ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 414
Author(s):  
Sang Gyun Shin ◽  
Dong Joon Min
Keyword(s):  
Reduction Rate ◽  
Pore Characteristics ◽  
Reduction Behavior ◽  
Reduction Stage ◽  
Initial Stage ◽  
Initial Reduction ◽  
Bet Analysis ◽  
Bet Technique ◽  
Feo Reduction ◽  
Abnormal Effect

The effect of extrinsic porosity on the reduction behavior of FeO was evaluated by thermogravimetric analysis (TGA), scanning electron microscopy (SEM) and the Brunauer–Emmett–Teller (BET) technique and analyzed using the labyrinth coefficient of FeO. The extrinsic pore exhibited an abnormal effect on reduction behavior in the range of less than 50% reduction degree, despite the increase in apparent porosity. SEM and BET analysis indicated that the abnormal reduction behavior by extrinsic pores at the initial reduction stage was speculated to be due to the characteristic of extrinsic pore that is open only at one end. However, the overall porosity and reduction rate after a 40% reduction revert to the normal relationship. In addition, the experimental results indicated that the abnormal effect of the extrinsic pores in the initial stage was mitigated by an increase in the temperature. The abnormal effect of extrinsic porosity on FeO reduction was mathematically analyzed using the labyrinth coefficient. It can be summarized that not only the number of pores, but also their quality and distribution are important in determining the reduction rate.

scholarly journals A Study on the Effect of Alumina on the Morphology and Reduction Behavior of Sinter by In Situ Observation

Metals ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 740
Author(s):  
Sang Gyun Shin ◽  
Wan Ho Kim ◽  
Dong Joon Min
Keyword(s):  
Reduction Rate ◽  
Al2o3 Content ◽  
Confocal Laser ◽  
In Situ Observation ◽  
Sintering Process ◽  
Reduction Behavior ◽  
Reducing Gas ◽  
Interfacial Chemical Reaction ◽  
Reaction Routes

The effects of Al2O3 content on the morphology and reducibility of sinter were respectively investigated using confocal laser microscopy and thermogravimetric analysis at 1273 K under CO gas. To understand the effects of the sintering process, separate samples were prepared via the equilibrium and metastable reaction routes. In the equilibrium samples, the addition of Al2O3 led to the formation of the silico-ferrite of calcium and alumino phase and a decrease in the reduction rate due to the lowered reactivity of iron oxide. In contrast, in the metastable samples, the reduction rate increased after the addition of 2.5 mass% Al2O3. The addition of Al2O3 decreased the fraction of the liquid phase and increased the fraction of pores in the sample. As a result, the reduction rate is proportional to the Al2O3 content owing to the changes in the sinter morphology. In determining the reduction rate of the sinter, the influence of the microstructure on the diffusion of the reducing gas is more significant than that of the interfacial chemical reaction due to the formation of the SFCA phase. The microstructure changes of the sinter with the addition of Al2O3 and the corresponding reduction behaviors are further discussed.

scholarly journals Propagation of International Supply-Chain Disruptions between Firms in a Country

2021 ◽  
Vol 14 (10) ◽  
pp. 461
Author(s):  
Hiroyasu Inoue
Keyword(s):  
Supply Chain ◽  
Reduction Rate ◽  
Value Added ◽  
Shock Propagation ◽  
Firm Level ◽  
Supply Chain Disruptions ◽  
Agent Based ◽  
Initial Reduction ◽  
The Us ◽  
Import And Export

This study shows how import and export shocks propagate through domestic supply chains using actual Japanese supply-chain data and a world input-output table (WIOT) based on firm-level agent-based simulations. We propose three different models with which to connect the domestic firms to a WIOT. Then, we estimate the value-added losses of Japanese firms caused by shocks of different magnitudes and durations originating in China, in the EU and the US, and globally. The volume and rates at which losses increase are very different across the connection models, which indicates that the assignment of international connections to firms matters greatly. The losses increase sublinearly as the duration expands, which indicates that the shock propagation ultimately saturates the economy. Rates of saturation differ substantially depending on the assignment of international connections. The losses increase superlinearly as the initial reduction rate increases. This occurs because there is a greater probability of one supplier being replaced by other suppliers if the reduction is smaller.

Pebax 1657 Nanocomposite Membranes Incorporated with Nanoadsorbent Derived from Oil Palm Frond for CO2/CH4 Separation

2020 ◽  
Vol 1007 ◽  
pp. 52-58
Author(s):  
Alia Aqilah Ghazali ◽  
Sunarti Abd Rahman ◽  
Rozaimi Abu Abu Samah
Keyword(s):  
Oil Palm ◽  
Gas Permeation ◽  
Nanocomposite Membrane ◽  
Nanocomposite Membranes ◽  
Pore Characteristics ◽  
Bet Analysis ◽  
Oil Palm Frond ◽  
Significant Attention ◽  
Palm Frond ◽  
Dipping Time

Membrane technology has attracted significant attention from the researchers, especially in gas separation process due to their simple process design and low capital cost compared to conventional techniques. In this work, oil palm frond (OPF) waste was used as nanoadsorbent embodied in polyether block amide (Pebax 1657) nanocomposite membrane to improve the CO2/CH4 separation. The effectiveness of the nanoadsorbent derived from OPF was evaluated by varying the nanoadsorbent concentration (2–8 wt %) and controlling the Pebax 1657 concentration (5 wt %), dipping time (5 s), and number of sequential coatings (3 layers). The pore characteristics of the nanoadsorbent was analyzed using Brunauer–Emmett–Teller (BET) analysis. The morphology and the existence of active groups in the newly synthesized nanoadsorbent and nanocomposite membranes were investigated using field emission scanning electron microscopy (FESEM) and Fourier transform infrared spectroscopy (FTIR), respectively. The single gas permeation process was carried out at constant pressure (2 bar) and room temperature (25 ± 5 °C). The optimum condition with 5 wt % nanoadsorbent made the nanocomposite membrane exceeded the trade-off limit of the Robeson plot with a CO2 permeability and CO2/CH4 selectivity of 1475.09 Barrer and 40.48, respectively.

scholarly journals Chemical Reduction Behavior of Zirconia Doped to Nickel at Different Temperature in Carbon Monoxide Atmosphere

2019 ◽  
Vol 20 (1) ◽  
pp. 105
Author(s):  
Norliza Dzakaria ◽  
Maratun Najiha Abu Tahari ◽  
Fairous Salleh ◽  
Alinda Samsuri ◽  
Masitah Abdul Halim Azizi ◽  
...  
Keyword(s):  
Carbon Monoxide ◽  
Physical Properties ◽  
Chemical Reduction ◽  
Chemical Effect ◽  
Reduction Temperature ◽  
Reduction Behavior ◽  
Absorption Isotherm ◽  
Temperature Programmed ◽  
Bet Technique ◽  
Reduction Characteristics

The reduction behavior of nickel oxide (NiO) and zirconia (Zr) doped NiO (Zr/NiO) was investigated using temperature programmed reduction (TPR) using carbon monoxide (CO) as a reductant and then characterized using X-ray diffraction (XRD), nitrogen absorption isotherm using BET technique and FESEM-EDX. The reduction characteristics of NiO to Ni were examined up to temperature 700 °C and continued with isothermal reduction by 40 vol. % CO in nitrogen. The studies show that the TPR profile of doped NiO slightly shifts to a higher temperature as compared to the undoped NiO which begins at 387 °C and maximum at 461 °C. The interaction between ZrO2 with Ni leads to this slightly increase by 21 to 56 °C of the reduction temperature. Analysis using XRD confirmed, the increasing percentage of Zr from 5 to 15% speed up the reducibility of NiO to Ni at temperature 550 °C. At this temperature, undoped NiO and 5% Zr/NiO still show some crystallinity present of NiO, but 15% Zr/NiO shows no NiO in crystalline form. Based on the results of physical properties, the surface area for 5% Zr/NiO and 15% Zr/NiO was slightly increased from 6.6 to 16.7 m2/g compared to undoped NiO and for FESEM-EDX, the particles size also increased after doped with Zr on to NiO where 5% Zr/NiO particles were 110 ± 5 nm and 15% Zr/NiO 140 ± 2 nm. This confirmed that the addition of Zr to NiO has a remarkable chemical effect on complete reduction NiO to Ni at low reduction temperature (550 °C). This might be due to the formation of intermetallic between Zr/NiO which have new chemical and physical properties.

scholarly journals Reduction of Haematite Using Hydrogen Thermal Plasma

2019 ◽  
Author(s):  
Masab Naseri Seftejani ◽  
Johannes Schenk ◽  
Michael Andreas Zarl
Keyword(s):  
Thermal Plasma ◽  
Hydrogen Plasma ◽  
Reduction Rate ◽  
Reduction Process ◽  
Pilot Scale ◽  
Phosphorus Concentration ◽  
Smelting Reduction ◽  
Reduction Behavior ◽  
Degree Of Reduction ◽  
Hydrogen Utilization

The development of hydrogen plasma smelting reduction as a CO2 emission-free steel-making process is a promising approach. This study presents a concept of the reduction of hematite using hydrogen thermal plasma. A laboratory scale and pilot scale hydrogen plasma smelting reduction (HPSR) process are introduced. To assess the reduction behavior of hematite, a series of experiments has been conducted and the main parameters of the reduction behavior, namely the degree of hydrogen utilization, degree of reduction and the reduction rate are discussed. The thermodynamic aspect of the hematite reduction is considered and the pertinent calculations have been carried out using FactSageTM 7.2. The degree of hydrogen utilization and the degree of reduction were calculated using the off-gas chemical composition. The contribution of carbon, introduced from the graphite electrode, ignition pin and steel crucible, to the reduction reactions was studied. The degree of reduction of hematite, regarding H2O, CO and CO2 as the gaseous reduction products, is determined. It is shown that the degree of hydrogen utilization and the reduction rate were high at the beginning of the experiments, then decreased during the reduction process owing to the diminishing of iron oxide. Conducting experiments with the high basicity of slag B2=2 led to a decrease of the phosphorus concentration in the produced iron.

scholarly journals Influence of a Prior Oxidation on the Reduction Behavior of Magnetite Iron Ore Ultra-Fines Using Hydrogen

2021 ◽  
Author(s):  
Thomas Wolfinger ◽  
Daniel Spreitzer ◽  
Heng Zheng ◽  
Johannes Schenk
Keyword(s):  
Iron Ore ◽  
Direct Reduction ◽  
Reduction Behavior ◽  
Thermogravimetric Analyzer ◽  
Initial Stage ◽  
Degree Of Oxidation ◽  
Apparent Activation Energies ◽  
High Degree ◽  
Positive Effect ◽  
Prior Oxidation

AbstractThe reduction behavior of raw and prior-oxidized magnetite iron ore ultra-fines with hydrogen was investigated. Reduction tests were conducted with a thermogravimetric analyzer in a temperature range from 873 K to 1098 K at 1.1 bar absolute, using hydrogen as reducing gas. The experimental results show that a prior oxidation of the magnetite has a positive effect on the reduction behavior because of changing morphology. The apparent activation energies show a turnaround to negative values, depending on the prior oxidation and degree of reduction. A multi-step kinetic analysis based on the model developed by Johnson–Mehl–Avrami was used to reveal the limiting mechanism during reduction. At 873 K and 948 K, the reduction at the initial stage is controlled by nucleation and chemical reaction and in the final stage by nucleation only, for both raw and pre-oxidized magnetites. At higher temperatures, 1023 K and 1098 K, the reduction of raw magnetite is mainly controlled by diffusion. This changes for pre-oxidized magnetite to a mixed controlled mechanism at the initial stage. Processing magnetite iron ore ultra-fines with a hydrogen-based direct reduction technology, lower reduction temperatures and a prior oxidation are recommended, whereby a high degree of oxidation is not necessary.

Effect of Hydrogen Addition on Reduction of Sinter

2013 ◽  
Vol 753-755 ◽  
pp. 58-61
Author(s):  
Xiang Wei Li ◽  
Ling Kun Chen ◽  
Wei Wang
Keyword(s):  
Blast Furnace ◽  
Reduction Rate ◽  
Content Increase ◽  
Reduction Behavior ◽  
Hydrogen Addition ◽  
Furnace Shaft ◽  
Reducing Gas ◽  
Coal Injection ◽  
High Level ◽  
Different Content

High level coal injection increases hydrogen of the gas in the blast furnace shaft, which changes the reduction behavior of sinter. This paper investigates the effect of hydrogen addition on reduction of sinter. Experiments of the sinter reduction in different content of hydrogen had been made. The experimental results show that the reduction rate increases with the hydrogen content increase in the reducing gas.

Cell Density Dependent Reduction Kinetics of Hexavalent Uranium byShewanella oneidensis

2002 ◽  
Vol 757 ◽  
Author(s):  
Lisa Mullen ◽  
Vanja Klepac ◽  
Chanathip Pharino ◽  
Ken Czerwinski ◽  
Martin Polz
Keyword(s):  
Cell Density ◽  
Inductively Coupled Plasma ◽  
Reduction Rate ◽  
Shewanella Oneidensis ◽  
Atomic Emission ◽  
Solution Concentration ◽  
Uranyl Acetate ◽  
Electron Acceptors ◽  
Initial Reduction ◽  
A Cell

ABSTRACTShewanella oneidensisis a widely distributed species of bacteria and is known to utilize several elements such as iron, manganese and sulfur as electron acceptors. In an anoxic environment lacking more electrochemically favourable electron acceptorsS. oneidensisis shown to reduce uranium, changing its oxidation state from hexavalent to tetravalent, by the following reaction: H2+ UO22+→ 2H++ UO2. The uranyl solution concentration (U(VI)) was measured using inductively coupled plasma atomic emission spectroscopy (ICP-AES), and the reduction data were fit to first order. Several cell concentrations were examined and both the rate of uranyl reduction and the total amount of uranyl reduced are found to be dependent upon cell density. The largest rate constant was 0.7 hr-1corresponding to a cell density of 2.4*109cells/mL and an initial reduction rate of 1414 μM/hr. A cell concentration of 6.6*108cells/mL gave rise to an initial reduction rate of 400μM U(VI) per hour, and had, within a period of 72 hours approximately 98% of the original 2 mM uranyl acetate reduced, as opposed to only 87% for 2.4*109cells/mL.

Reaction couples of ceramic thin films prepared by CVD

1988 ◽  
Vol 46 ◽  
pp. 798-799
Author(s):  
D.W. Susnitzky ◽  
S.R. Summerfelt ◽  
C.B. Carter
Keyword(s):  
Thin Film ◽  
Vapor Deposition ◽  
Chemical Vapor ◽  
Deposition Process ◽  
Solid State Reactions ◽  
Spatial Distributions ◽  
Diffusion Couples ◽  
Kinetics Studies ◽  
Ceramic Thin Films ◽  
Initial Stage

Solid-state reactions have traditionally been studied in the form of diffusion couples. This ‘bulk’ approach has been modified, for the specific case of the reaction between NiO and Al2O3, by growing NiAl2O4 (spinel) from electron-transparent Al2O3 TEM foils which had been exposed to NiO vapor at 1415°C. This latter ‘thin-film’ approach has been used to characterize the initial stage of spinel formation and to produce clean phase boundaries since further TEM preparation is not required after the reaction is completed. The present study demonstrates that chemical-vapor deposition (CVD) can be used to deposit NiO particles, with controlled size and spatial distributions, onto Al2O3 TEM specimens. Chemical reactions do not occur during the deposition process, since CVD is a relatively low-temperature technique, and thus the NiO-Al2O3 interface can be characterized. Moreover, a series of annealing treatments can be performed on the same sample which allows both Ni0-NiAl2O4 and NiAl2O4-Al2O3 interfaces to be characterized and which therefore makes this technique amenable to kinetics studies of thin-film reactions.

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