Effects of reduction on the catalytic performance of limonite ore

The concentration of low grade iron ore resources was evaluated by washing and reduction. The advanced concentration methods for low grade limonite and hematite iron ores of South Eastern Anatolian resources required such specific methods. The followed column flotation and magnetic separation, microwave radiated reduction of hematite slime and limonite sand orewere investigated on potential reducing treatment. The bubling fluidized bed allows more time to the heat radiation and conduction for reducing to the resistive ıron compounds. Furthermore, heavy limonite and iron oxide allowed sufficient intimate contact coal and biomass through surface pores in the bubbling fluidized bed furnace due to more pyrolysis gas desorption. Bubbling bath porosity decreased by temperature decrease. This research was included reduction in microwave of poor hematite and limonite ores in the microwave ovens, but through smaller tubing flows as sintering shaft plants following column flotation and scavangering operation. Two principle stages could still manage prospective pre reduction granule and pellet production in new sintering plants. There is a lack of energy side which one can produce reduced iron ore in advanced technology plants worldwide. However, for the low grade iron ores such as limonite and sideritic iron ores it was thought that microwave reduction technique was assumed that this could cut energy consumption in the metallurgy plants.

Australia has large reserves of limonite and clay-based laterites that are currently underutilized. This review summarizes the latest nickel laterite upgrading studies reported in the literature which use physical beneficiation – only studies reported after the most recent review in 2015 included – as well as high-temperature methods involving oxidation/reduction roasting (with and without additives), sulphidation, and other high-temperature methods. The focus of this review is on upgrading limonite ores, but studies using other types of laterites are also discussed for comparative purposes. Oxidative roasting has proven to be ineffective but producing a magnetic phase by reduction roasting then magnetically separating it from gangue minerals has produced nickel grades and recoveries of up to 14% and 99% respectively with limonite ores. The choice of reductant has negligible effect although hydrogen reduction is predicted to occur at slightly lower temperatures and recoveries are slightly lower compared with carbon-based reductants. The addition of sulfurous compounds improves agglomeration of ferronickel particles, increases the nickel grade and recovery. The highest recovery of 97.91% (grade 13.62%) was reported when sulfur was used as an additive during the roasting of a limonite ore with coal and limestone at 1400°C for 6 h. The results show reduction roasting followed by magnetic separation is effective for upgrading nickel ores, but challenges with this technology are the potentially high reagent usage and temperatures required. The economic feasibility for processing limonite ores via this route is not clear and should be investigated further.

Phase transformation of iron in limonite ore by microwave roasting with addition of alkali lignin and its effects on magnetic separation

Mass-Transfer Limitation in Mesopores of Ni–MgO Catalyst in Liquid-Phase Hydrogenation

The deterioration mechanism of reforming catalysts used for internal reforming molten carbonate fuel cells is studied through post-test analyses of the used catalysts. The catalysts studied are Ni/MgO-Al2O3. Deactivation of the catalysts is caused both by a decrease in Ni surface area of the catalyst and by loss of specific activity of the Ni surface (alkali poisoning). The decrease in Ni surface area is characterized firstly by accelerated sintering of Ni particles due to the existence of alkali metals (attached electrolyte). Secondly, sulfur poisoning also plays an important role, especially for sintered catalysts with small Ni surface areas. As for the effect of alkali poisoning, the specific activity of the Ni surface decreases to 15–60% of the original one. Blockage of pore structure by the electrolyte does not seem to be important for the loss of Ni surface area.

Production of ferronickel from limonitic laterite ore using hydrogen reduction and cementation

Reduction behavior of iron oxides in hydrogen and carbon monoxide atmospheres

The iron and steel industry is a major emitter of carbon. In the context of China’s dual-carbon goals, hydrogen-based reduction ironmaking technology has garnered unprecedented attention. It is considered a crucial approach to reducing carbon dioxide emissions in the steel sector and facilitating the realization of carbon neutrality. This work conducted isothermal thermogravimetric analysis on limonite ore in a N2/H2 atmosphere. The influences of reduction temperature, particle size, and hydrogen partial pressure on the hydrogen reduction reaction process of limonite were investigated. Based on the principles of isothermal thermal analysis kinetics and the unreacted core model for flat-plate particles, the mechanism function and kinetic parameters for the reduction of limonite particles were determined. The research results show that the hydrogen reduction process of limonite ore is influenced by multiple factors, including temperature, hydrogen partial pressure, and particle size. Increasing the reduction temperature and hydrogen partial pressure can significantly speed up the reduction reaction rate and enhance the degree of reduction. The kinetic parameters for the hydrogen reduction of limonite particles were obtained as follows: the reaction activation energy was 44.738 kJ·mol−1, the pre-exponential factor was 31.438 m·s−1, and the rate constant for the hydrogen reduction of limonite was k=31.438×e−44.738×1000RTm⋅s−1. In addition, contour maps were plotted to predict the reaction time and reaction temperature required for a complete reduction of limonite particles of different sizes to iron (Fe) particles under varying hydrogen partial pressures. The research findings can serve as a scientific basis for optimizing hydrogen-based reduction ironmaking technology in the iron and steel industry and achieving carbon neutrality goals.

Novel and green metallurgical technique of comprehensive utilization of refractory limonite ores

The utilization of fossil fuels has led to a gradual increase in greenhouse gas emissions, which have accelerated global climate change. Therefore, there is a growing interest in renewable energy sources and technologies. Biogas has gained considerable attention as an abundant renewable energy resource. Common biogases include anaerobic digestion gas and landfill gas, which can be used to synthesize high-value-added syngas through catalytic reforming. Because syngas (CO and H2) is synthesized at high reaction temperature, carbon is generated by the Boudouard reaction from CO and CH4 cracking; thus, C blocks the pores and surface of the catalyst, thereby causing catalyst deactivation. In this study, a simulation was performed to measure the CH4 and CO2 conversion rates and the syngas yield for different ratios of CO2/CH4 (0.5, 1, and 2). The simulation results showed that the optimum CO2/CH4 ratio is 0.5; therefore, biogas reforming over the 3 wt% Ni/Ce-MgO-ZrO2/Al2O3 catalyst was performed under these conditions. CH4 and CO2 conversion rates and the syngas yield were evaluated by varying the R values (R = (CO2 + O2)/CH4) on the effect of CO2 and O2 oxidants of CH4. In addition, steam was added during biogas reforming to elucidate the effect of steam addition on CO2 and CH4 conversion rates. The durability and activity of the catalyst after 200-h biogas reforming were evaluated under the optimal conditions of R = 0.7, 850 °C, and 1 atm.

A series of Ni/AC catalysts is prepared using acetylacetone nickel as the precursor and low-rank coal as the carbon source. Their catalytic performance in methane cracking for hydrogen production and the regeneration effect of hydrogen reduction on these catalysts are systematically investigated. First, the effects of hydrogen flow rate and reaction time are studied when the catalyst is regenerated after cracking methane. Subsequently, by varying nickel loading (5%, 10%, 15%, 20%), the influence of metal dispersion, pore structure, and coking on catalytic activity and stability is investigated. The results show that after the first hydrogen reduction treatment, the methane conversion of the 20-AC increases from 9.00% to 13.40%. Methane conversion of the 20-AC-20 increases from 9.10% to 12.90%. Hydrogen flow rate and reaction time are set to 20 mL/min and 20 min, respectively. Catalyst can be recovered to optimal catalytic activity after multiple cycles of methane catalytic cracking for hydrogen production. The 10-Ni/AC catalyst exhibits the highest methane conversion (16.94%) and catalytic stability. The actual loadings of Ni in 10-Ni/AC are 6.80%. The 10-Ni/AC is analyzed by the XRD, BET, SEM, and TEM. Its surface of 10-Ni/AC contains uniformly distributed metallic Ni. The carbon materials formed on the surface of 10-Ni/AC after the methane cracking reaction are mainly carbon nanotubes and flaky carbon. The carbon nanotubes on the surface of 10-Ni/AC exhibit both tip growth and base growth. As the reaction time increases, carbon atoms continuously accumulate on the surface of nickel, and gradually thicken the graphite layers. This will lead to the deactivation of the catalyst. The hydrogen reduction of 10-Ni/AC effectively restores partial activity, but the active site gradually decreases with increasing reaction cycles. The hydrogen reduction primarily exposes more Ni by consuming carbon deposits to enable catalytic activity, while specific surface area plays only a secondary role.

Hydrogen production by steam reforming of ethanol over P123-assisted mesoporous Ni–Al2O3–ZrO2 xerogel catalysts

Nickel in the form of nickel laterite ore is one of the most prominent types of mining products in Southeast Sulawesi, Indonesia. One of the utilization of laterite nickel ore is as raw material for ferronickel and NPI production. In this research, the NPI was produced from laterite nickel ore originating from Sulawesi Island in electric arc furnace (EAF). This study aims to determine the effect of the amount of flux (limestone) and type of reducing agent (coal, coke, and shell charcoal) on the content of Ni and Fe in the NPI product and metal yield. Laterite nickel ore used in this study is a type of limonite from Pomaala (Sulawesi Island). The reducing agents used are coke, coal, and coconut shell charcoal. Limestone was used as a flux to adjust the basicity of material during the smelting process of lateritic nickel ore. Reduction and melting process of limonite nickel ore to produce NPI were conducted in small EAF with capacity of 30 kg/heat. The dried pellets are reduced and melted in the EAF with added reducing agents and limestone. Based on the results of the study it can be concluded that the results of the flux addition effect obtained that the optimum Ni and Fe values were obtained on basicity of 1. The results of the reductant type effect showed that coke was the greatest reductant in this study due to the highest Ni content produced when coke used as reductant. In addition, the XRD results showed that the FeNi phase has been formed.

Single (Iron) and Binary (Iron and Cobalt) Metal Oxide Doped Silica Membranes for Gas Separation

Effect of modified basicity in selective reduction process of limonitic nickel ore