Structure evolution of a magnetite iron ore/carbon composite pellet during solid-state reduction under microwave heating

In the present study, the structure evolution under direct reduction of a Minh-Son magnetite iron ore/carbon composite pellets in a microwave-heating kiln under different microwave wattage of 60 and 90 % (with the firing time from 15 to 120 min.) was investigated. The microstructure of the pellets was characterized by scanning electron microscopy coupled with energy dispersive spectroscopy and X-ray diffraction (XRD). The phase formation was indexed using MDI Jade from the peaks matching the reference sample. At the microwave’s wattage of 60 %: the wustite (FeO) has appeared after firing time of 60 min., the metallic iron and fayalite have appeared in the reduced samples after firing time of 90 min. to 120 min. with retained phases of Fe203, Fe304, FeO and Si02– While at the microwave’s wattage of 90 %, the metallic iron has appeared in the reduced samples after firing time of 30 min. to 120 min and fayalite has appeared in the reduced samples after firing time of 60 min. to 120 min. The final reduced pellet, under microwave’s wattage of 90 % and firing time of 120 min., shows the only phases of metallic iron and fayalite according to the XRD resolution. The present work could provide a scientific understanding to illustrate iron ore/carbon composite pellet behavior during solid-state carbothermic reduction under a microwave-heating.

Intelligent Traffic Signal Control Based on Reinforcement Learning with State Reduction for Smart Cities

Efficient signal control at isolated intersections is vital for relieving congestion, accidents, and environmental pollution caused by increasing numbers of vehicles. However, most of the existing studies not only ignore the constraint of the limited computing resources available at isolated intersections but also the matching degree between the signal timing and the traffic demand, leading to high complexity and reduced learning efficiency. In this article, we propose a traffic signal control method based on reinforcement learning with state reduction. First, a reinforcement learning model is established based on historical traffic flow data, and we propose a dual-objective reward function that can reduce vehicle delay and improve the matching degree between signal time allocation and traffic demand, allowing the agent to learn the optimal signal timing strategy quickly. Second, the state and action spaces of the model are preliminarily reduced by selecting a proper control phase combination; then, the state space is further reduced by eliminating rare or nonexistent states based on the historical traffic flow. Finally, a simplified Q-table is generated and used to optimize the complexity of the control algorithm. The results of simulation experiments show that our proposed control algorithm effectively improves the capacity of isolated intersections while reducing the time and space costs of the signal control algorithm.

Nanocrystalline Formation and Magnetic Properties in Fe2O3–C System by Mechanical Alloying

The effect of mechanical alloying (MA) on the solid state reaction of hematite and graphite system with a positive reaction heat was investigated using a mixture of elemental Fe2O3–C powders. The solid state reduction of hematite to Fe3O4 has been obviously observed after 3 hours of MA by a vibrating ball mill. A two-phase mixture of Fe3O4 and remaining Fe2O3 is obtained after 5 hours of MA. Saturation magnetization gradually increases with MA time due to the formation of Fe3O4 and then reaches 23 emu/g after 5 hours of MA. In addition, a Fe3O4 single phase is obtained by MA after 3 hours and subsequently heat treated up to 700°C. X-ray diffraction result shows that the average grain size of Fe3O4 prepared by MA for 5 hours and heat treatment to be in the range of 92 nm. The saturation magnetization of Fe3O4 prepared by MA and heat treatment reaches a maximum value of 56 emu/g for 5 hours MA sample. It is also observed that the coercivity of 5 hours MA sample annealed at 700 °C is still high value of 113 Oe, suggesting that the grain growth of magnetite phase during annealing process tends to be suppressed.

Physics and Chemistry of Solid State Direct Reduction of Iron Ore by Hydrogen Plasma

Presently, Iron is produced from iron ores by using carbon from coal. The production process is consisting of many stages. The involvement of multi-stages needs high capital investments, large-scale equipments, and produces large amounts of carbon dioxide (CO2) responsible for environmental pollution. There have been significant efforts to replace carbon with hydrogen (H2). Although H2 is the strongest reductant, it still also has thermodynamic and kinetic limitations. However, these thermodynamic and kinetic limitations could be removed by hydrogen plasma (HP). HP comprises rovibrationally excited molecular, atomic, and ionic states of hydrogen. All of them contribute to thermodynamic advantage by making the Gibbs standard free energy more negative, which makes the reduction of iron oxides feasible at low temperatures. Apart from the thermodynamic advantage, these excited species increase the internal energy of HP, which reduces the activation energy, thereby making the reduction easier and faster. Apart from the thermodynamic and kinetic advantage of HP, the byproduct of the reaction is environmentally benign water. This review discusses the physics and chemistry of iron ore reduction using HP, emphasizing the solid-state reduction of iron ore. HP reduction of iron ore is a high potential and attractive reduction process.

Reaction Rate Analysis of Manganese Ore Prereduction in CO-CO2 Atmosphere

Variations in energy efficiency and climate gas emissions in production of manganese ferroalloys are largely related to the solid-state reduction of the manganese ores used as raw material in the production. The gas-solid reduction is known to be dependent on the ore characteristics, making information on the factors governing the kinetics crucial. A reaction rate analysis of thermogravimetric data obtained for the reduction of Comilog and Nchwaning manganese ores in CO-CO2 atmosphere was performed. Experimental variables were CO partial pressure, ore particle size, temperature regimes (isothermal/non-isothermal), as well as heating rate for non-isothermal experiments. The effects of particle size, CO-concentration, and temperature on the reaction rates were quantified. It was found that the reduction rate of both ores was proportional to the inverse average particle size. Different sensitivities towards the CO-concentration in the gas feed was determined, where the rate of Comilog-ore was proportional to $$ p_{\text{CO}}^{0.7} $$ p CO 0.7 , and Nchwaning to $$ p_{\text{CO}}^{1.5} $$ p CO 1.5 . The activation energy of Comilog ore was estimated to be 17 kJ/mol, whereas 63 kJ/mol was found for Nchwaning ore.

Influence of the Application of a Sound Field on the Flow State Reduction of Newman Fine Iron Ore

To improve the fluidization of the fluidized bed in ironmaking, the particle loss and bonding during the fluidized bed are largely removed by changing the properties of the particle surface or by adding an external field. Currently, the vibration, magnetic, sound, and electric fields have been commonly applied to provide external energy to the fluidization bed systems. In this work, experiments are conducted for Newman ore particles under the application of an external sound field at a reduction temperature of 1023 K, linear velocity of 0.6 m/s, duration of 60 min, pressure of 0.2 MPa, and typical mineral powder particle size of 80–100 mesh, with H2 used as the reducing gas. The power and frequency of the ultrasonic field are varied, and the effects of sound field are evaluated by the comparative analysis of the effects of the sound field with different powers of sound fields and application times on the metallization rate and binder ratio of the samples. The acoustic pressure and frequency were varied to determine the critical speed and influence on the bed and to study the interactions of the iron ore powder particles in the sound field and the bonding mechanism of the particles. The results of this paper reproduce the actual particle fluidization process and analysis of the interactions of the particles in the sound field well. The influence of the external sound field on the gas-solid flow was studied from the perspective of macroscopic motion and force analysis.

Spatio-temporal modelling for the evaluation of an altered Indian saline Ramsar site and its drivers for ecosystem management and restoration

Saline wetlands are keystone ecosystems in arid and semi-arid landscapes that are currently under severe threat. This study conducted spatio-temporal modelling of the largest saline Ramsar site of India, in Sambhar wetland from 1963-2059. One CORONA aerial photograph of 1963 and Landsat images of 1972, 1981, 1992, 2009, and 2019 were acquired and classified under 8 classes as Aravalli, barren land, saline soil, salt crust, saltpans, waterbody, settlement, and vegetation for spatial modelling integrated with bird census, soil-water parameters, GPS locations, and photographs. Past decadal area statistics state reduction of waterbody from 30.7 to 3.4% at constant rate (4.23%) to saline soil. Saline soil increased from 12.4 to 21.7% and saline soil converted to barren land from 45.4 to 49.6%; saltpans from 7.4 to 14% and settlement from increased 0.1 to 1.3% till 2019. Future predictions hint at a net increase of 20% by wetland, vegetation by 30%, settlement by 40%, saltpan by 10%, barren land by 5%, and net loss of 20%, each by Aravalli and salt crust. The biggest loss of 120% was seen by saline soil converted to barren land. Notably, 40% of the current wetland will be lost by 2059. Additionally, soil-water parameters result state a loss of saline character of wetland ecosystem; subsequently bird statistics indicate a shift in migratory birds disturbing the wetland food web. India has been losing a critical habitat of migratory birds, halophytes, and halophiles, along with livelihood. This study looks to bridge the missing link from local to global wetland ecological disconnect, providing thereby lake management and restoration strategies.