Hidehiko Okada

Computational fluid dynamics simulation of high gradient magnetic separation

Abstract A computational fluid dynamics (CFD) model was developed for High Gradient Magnetic Separation (HGMS) of particles in liquids flowing through magnetic filters. Using this model, we simulated the effect of fluid flow, magnetic forces, and particle diffusion on the particle filtration efficiency in an HGMS liquid particle filter. By simulating capture efficiency of the simple configuration, the overall filtration efficiency of HGMS filters can be determined. This paper describes this numerical model and simulation results for an HGMS liquid particle filter.

Removal system of arsenic from geothermal water by high gradient magnetic separation-HGMS reciprocal filter

We have developed a high gradient magnetic separation (HGMS) system to remove arsenic from geothermal water and to supply hot water for public use by using a superconducting magnet. We attained the reduction of arsenic concentration to 0.015 mg/L that is less than the standard for discharge of 0.1 mg/L and slightly larger than the environmental standard of 0.01 mg/L in Japan. The system consists of a pretreatment process that adds extra magnetization to arsenic by chemical reaction, and a reciprocal HGMS filter using a superconducting magnet that extracts magnetized arsenic from the geothermal water. We present the experimental results of the removal system.

Removal of arsenic from geothermal water by high gradient magnetic separation

On-site experimentation of high gradient magnetic separation (HGMS) for arsenic removal from geothermal water has been conducted using a high-T/sub c/ superconducting magnet. This development of an effective method for decontamination of geothermal water is currently being done at the Kakkonda geothermal power plant in Shizukuishi, Iwate, Japan. In order to enhance the magnetic properties of the arsenic-containing particles in geothermal water, three different pretreatment methods were used: (I) the ferrite formation method; (II) the ferric hydroxide coprecipitate method; and (III) the modified ferric hydroxide coprecipitate method. The conditions of the HGMS experiments were a 1.7 T applied magnetic field and 100/spl deg/C water at a flow rate of 10 L/min. Percentages of the arsenic-removal were strongly dependent on the pretreatment methods, because of a very small magnetization of the arsenic. Arsenic-removal rates of 40%, 80%, and 90% were obtained by pretreatments I, II, and III, respectively. Although the environmental standard for arsenic is 0.01 mg/L, corresponding to a 99% removal rate, could not be achieved in the present experiments, it can be thought that HGMS substantiates the achievement of environmental standards for arsenic, if an optimized pretreatment method is taken.

Feasibility study of the new rutile extraction process from natural ilmenite ore based on the oxidation reaction

Phase relations in the Fe2O3-FeTiO3-TiO2 system were investigated by equilibrating synthetic samples in evacuated sealed quartz tubes at a temperature of 1373 K. The equilibrium partial pressure of oxygen was measured by the electromotive force (EMF) method in the temperature range of 1273 to 1373 K. The phase diagram and oxygen partial pressure diagram in the titanium-iron-oxygen ternary system were then constructed at 1373 K. Rutile extraction from natural ilmenite ore was discussed from the thermodynamic viewpoint. It is found that rutile can be produced from common natural ilmenite ores not only by the reduction as the conventional titanium-rich slag process but also by an oxidation. Then, the oxidation experiment was conducted in air using Australian ilmenite ore to obtain rutile as one of the coexistent phases. Magnetic separation and leaching experiments for synthesized pseudobrookite and reagent rutile were conducted to confirm the possibility of separation of rutile from pseudobrookite. A new rutile extraction process was then proposed.

High gradient magnetic separation using superconducting bulk magnets

Abstract We aim to apply the superconducting bulk magnets to high gradient magnetic separation technique. Two bulk magnets are face-to-face arranged and a pipe stuffed magnetic filters composed of ferromagnetic wires is placed between the magnetic poles. We setup the magnetic separation system and test it using slurry mixed with hematite particles (Fe2O3). Y123 bulk superconductors are magnetized by the “IMRA” method (pulsed-field magnetization), and consequently a magnetic field of 1.59 T is generated at the center of 20 mm gap between the magnetic poles. As a result of experiment on the magnetic separation, hematite particles of over 90% were removed from slurry at the flow rate of 2 l/min.

High gradient magnetic separation for weakly magnetized fine particles [for geothermal water treatment]

We measured the removal efficiency of hematite (Fe/sub 2/O/sub 3/) and iron (III) hydroxide (Fe(OH)/sub 3/) fine particles suspended in water in a high gradient magnetic separation (HGMS) system. Fe/sub 2/O/sub 3/ and Fe(OH)/sub 3/ have relatively small magnetic relative susceptibilities (MKS) near 10/sup -3/ and average particle diameters near 1 /spl mu/m. We demonstrated that HGMS is able to effectively separate weakly magnetized particles.

Removal of Aerosol by Magnetic Separation

We concluded high gradient magnetic separation experiments of iron (ferromagnetic) nano-particles with a nominal diameter of 50 nm by using a superconducting magnet. In the experiment, we fabricated fine iron particles using a thermal reactive plasma method in argon and hydrogen mixed gas and sent them directly to the magnetic separator. We present the experimental results, functions of the capture ratio on the magnetic flux density, and velocity of flow. We conclude that high gradient magnetic separation can separate nano-particles and is useful for nano-technology

A 3 T magnetic field generator using melt-processed bulk superconductors as trapped field magnets and its applications

Abstract An intense magnetic field generator yielding 3.15 T in the open space between the magnetic poles has been constructed by using a pair of melt-processed bulk superconductors as trapped field magnets. The field was measured in a 2 mm gap between the magnetic poles set face-to-face after the pulsed-field magnetization “IMRA” method. This field generator is composed of Sm-based 123 compounds, vacuum pumps, pulsed-field coils and GM refrigerators with compressors. The system can be used in various applications. We investigated, for instance, the application to a high gradient magnetic separation system. It was found that the alpha hematite fine particles mixed in the flowing water was completely removed by this technique which was operated in the field of 1.7 T in the gap of 20 mm.

Removal of Iron Oxide With Superconducting Magnet High Gradient Magnetic Separation From Feed-Water in Thermal Plant

By the accident of Fukushima Daiichi Nuclear Plant, all the nuclear plants have stopped in Japan. As a result, the operation rate of thermal power plants has been increased. It caused growth in CO2 emission, which requires some kind of countermeasure. We focused on the iron oxide scales deposited on the piping system and boiler which declines the heat exchange efficiency of thermal power plants. In this study we attempt to remove the iron scales from the piping system and the boiler to maintain the power generation efficiency. In the current thermal plant treated by All Volatile Treatment (AVT) the iron elutes to the feed water in the low-temperature part which changes into iron ion or the paramagnetic fine iron oxide particles. On the other hand at the high-temperature part the main component of the scales is large ferromagnetic particles of magnetite. Therefore the magnetic separation at the high-temperature part is the more effective to remove the scale than that at the low-temperature part. For the reason, the existing method using the electromagnetic filter placed in the low-temperature part is not effective to remove the scales. We studied the high gradient magnetic separation (HGMS) at high-temperature part to remove a large amount of the scale. In this study, we assumed to install the HGMS system using the superconducting magnet at the inlet of the boiler.

Simulation of fluid flow during protein crystal growth in magnetic fields

We are developing a superconducting magnet system to grow high-quality protein crystals. The gravity-controlled environment, based on magnetic forces, can suppress thermal convection and may give rise to a variety of additional effects on the protein crystal growth. To design suitable magnetic force conditions for protein crystal growth in protein solutions, we are studying a gravity-controlled environment by magnetic forces in the crystal growth process by computer simulations. In this study, we derived a modified Navier-Stokes equation with gravity and static magnetic force and numerically solved the equation. The obtained results show that the temperature dependence of the magnetization modifies the levitation condition and the magnetic force gives rise to an unexpected change of fluid motion.