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We have been developing the scale removal system utilizing superconducting magnet that can remove iron scale from boiler feed-water in a thermal power plant. The scale removal prevents the plants from the reduction in power generation efficiency. Iron oxide scale consists of the ferromagnetic and the paramagnetic particles, and the optimal separation conditions largely differ depending on the magnetic properties of the particles. So, single separation condition may cause the filter blockage by over capture or inadequate capture. We proposed the two-stage magnetic separation according to the magnetic properties of the aggregates, where the ferromagnetic particles are captured in the 1st stage in low magnetic field and field gradient, and then the paramagnetic ones are captured in the 2nd stage in high magnetic field and field gradient. It was shown that two-stage magnetic separation system for the mixture of ferromagnetic and paramagnetic particles is possible by utilizing one superconducting solenoidal magnet.

We have been developing a scale removal system utilizing a superconducting magnet that can remove the iron oxide scale from the boiler feed-water in the thermal power plants. Scale removal can prevent a decrease in the power generation efficiency and contribute to reduce the carbon dioxide emissions. In our previous study, we conducted the large-scale experiments for practical use, but model particles were intensively captured by the inflow side filter. In this paper, we succeeded to homogenize the distribution of captured particles in the filter stacks by controlling the applied magnetic field strength. In addition, magnetic field strength dependency of filter blockage was examined in the lab-scale experiments to clarify a detailed mechanism of blockage.

To improve thermal power plant efficiency, we proposed a water treatment system with a high gradient magnetic separation (HGMS) system using a superconducting magnet, which is applicable in high-temperature and high-pressure conditions. This is a method to remove the scale from feed-water utilizing magnetic force. One of the issues for practical use of the system is how to extend the continuous operation period. In this paper, we succeeded in solving the problem by eliminating the deviation of captured scale quantity by each filter. In fact, in the HGMS experiment using the solenoidal superconducting magnet, it was shown that a decrease in separation rate and an increase in pressure loss were prevented, and the total quantity of captured scale increased by proper filter design. The design method of the magnetic filter was proposed and will be suitable for long-term continuous scale removal in the feed-water system of the thermal power plant.

We are developing a superconducting magnetic separation system to remove scale or iron oxide from boiler feedwater in thermal power plants. The reduction of scale improves energy conversion efficiency of thermal power plants and reduces discharged CO 2 . We have studied suitable installation locations and operation conditions and examined the separation ability of the system located near the boiler where the water is at high temperatures and pressures. We have concluded that the magnetic separation system is effective to remove scale of boiler feedwater and that the use of a superconducting magnet is essential for the system.

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 CO 2 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.

The magneto-Archimedes separation allows for separating mixtures of feeble magnetic materials into its components based on the difference of their densities and magnetic susceptibilities. So far, this technique was applied for the separation of relatively large particles of several millimeters in diameter. Here we apply this technique experimentally to the simultaneous quantitative analysis of multiple micrometer-sized particles in a fluid. It was confirmed that the magneto-Archimedes separation can be applied for the separation of mixture of microspheres larger than 20 μm. Further high performance separation efficiency is expected with the optimization of separation conditions including the control of the spatial distribution of the magnetic field.

The effect of high magnetic field on diamagnetic fluid flow has been studied by in-situ optical observation. The Schlieren optics utilizable under high magnetic fields was developed to carry out in-situ observation of the behavior of feeble magnetic fluids. Using a crystal of the diamagnetic aluminum potassium sulfate dodecahydrate, the behavior of the downward flow of high concentration solution in the sample dissolution process was observed. It was found that the direction of diamagnetic fluid flow was changed under spatially varied magnetic field. This phenomenon was understood qualitatively by considering the magnetic force acting on the high concentration solution and the surrounding solution.

A quasi-microgravity environment appears in a high-field superconducting magnet bore where a large magnetic force counterbalances gravity acting on a diamagnetic substance. This suppresses convection of the diamagnetic solution in the crystallization cell placed in the bore from which protein crystals precipitate. A 16 T class superconducting magnet has been developed with a special coil configuration; one of the component coils produces a magnetic field the direction of which is opposite to that of the other coils. Thus, a large magnetic field gradient occurs, creating a magnetic force large enough to levitate water and hinder convection. This magnet system is operated in persistent mode, which is adequate for a rather time-requesting crystallization process of proteins. Preliminary experiments have shown that the protein crystallization process is substantially retarded in the magnetic force field.

The magnetic chromatography (MC) is a very useful system for an ion and/or fine magnetic particle separation due to its strong magnetic field gradients in a very small flow channel. We have not only developed the MC system to separate the fine particles and ions, we have also developed the numerical analysis computer code based on the fluid dynamics and electromagnetism to investigate the separating characteristics and to optimize design of magnetic column. In this paper, we studied MC technology for magnetic particles and ion separations using micro-scale magnetic column with ferromagnetic wires experimentally. The influences of the strength of magnetic gradient, flow velocity and coefficient of viscosity of solvent were studied by the developed computer code.

Alumina with nanoholes was prepared by anodic oxidation of aluminium and subsequently the synthesis of Fe nanofibers was attempted using nanoholes in alumina as a template. Various Fe nanofibers were synthesized by electroplating into alumina templates and subsequent chemical treatments in mixed-acid solutions to remove the templates. Obtained Fe nanofibers had the dimension with 20 nm-30 nm in diameters and typically 500 nm-2 μm in length. Effect of anodic oxidation treatments for a template on the microstructure of Fe nanofibers was examined. The length of Fe nanofibers could be changed by modifying the synthetic conditions, such as anodic oxidation times and electroplating times.

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.

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.

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.

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.

A superconducting permanent magnet system capable of generating strong magnetic fields has been constructed by using melt-processed bulk superconductors as trapped field magnets. The trapped field in the open space between two magnetic poles that are set face to face has reached 3.15 T when magnetized by a pulsed-field magnetization (PFM) technique. That was operated at 30 K attained by GM-cycle refrigerators. The performance exceeds that of conventional rare earth magnets or large scale electromagnets by far. It was found that the iteratively magnetizing pulsed field operation with reducing amplitude (IMRA) method is very effective in magnetizing the bulk superconductors. The magnet system can be used as a high field generator in various applications.

Our research is to magnetize the high-T/sub c/ bulk superconductors and to supply magnetic field environment realized by superconducting bulk magnets to various applications. In this paper, we aim to apply the superconducting bulk magnets to the high gradient magnetic separation (HGMS). Using a face-to-face type superconducting bulk magnet system in which a pair of bulk superconductors are oppositely arranged, Y123 bulk superconductors are magnetized by the "IMRA" method (pulsed field magnetization), and consequently, a magnetic field of 1.6 T is achieved between the magnetic poles. Next, HGMS using superconducting bulk magnets is demonstrated. A separation pipe into which filter matrices composed by ferromagnetic wires are stuffed is set between the magnetic poles and the slurry mixed with fine powder of /spl alpha/-hematite (Fe/sub 2/O/sub 3/) particles is flown. As the results of HGMS, over 90% of the Fe/sub 2/O/sub 3/ was separated. Moreover, separation filters have to be washed so that they are not clogged with captured particles. We confirmed that the filter was briefly washed by flowing water after moving the separation pipe from magnetic poles.

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.

Our objective was to apply superconducting bulk magnets to a magnetic separation technique. A pair of Sm123 bulk superconductors were magnetized by the “IMRA” method and arranged opposite each other with a gap of 20mm. The maximum flux density at the surface of the magnetic poles containing the bulk magnets and at the center of the gap of the poles was 2.26T and 1.76T, respectively. We set up a magnetic separator by placing a pipe between the magnetic poles of face-to-face superconducting bulk magnets and conducted experiments for two types of magnetic separation: high gradient magnetic separation (HGMS) with the use of a stainless steel filter, and open gradient magnetic separation (OGMS) without filters. The former uses separation filters composed of ferromagnetic wires stuffed into a glass pipe, and therefore a high gradient magnetic field is generated near the wires. The latter does not use filters. The separation ratio is investigated by the experiments using water mixed with fine powder of Fe3O4 and the performance of about 100% is achieved in HGMS.

A full system of 1 kWh/1 MW superconducting magnetic energy storage (SMES) has been completed early this year. This SMES is the first step to the realization of practical SMES system for power line stabilization. Main points in its design are two module type arrangement of six coils having three coils and one converter as one unit of module, modified-D-shaped coils with mechanical supports, liquid helium vessel type cooling of coils, and high-temperature superconducting current leads. The first test experiment was carried out on the site recently. The above design points were examined. A preliminary test for power line control was also made in the distribution line at the site. Satisfactory results were obtained.

The authors are planning to build a 1 kWh/1 MW (maximum stored energy/maximum power capability) module-type SMES (named ESK; experimental SMES of Kyushu Electric Power) as a first step towards the realization of practical SMESs for power line control. The main points of the design are those of: module-type coils for the development of SMES capacity scale-up; the choice of low loss stranded cables for reducing pulse operating loss; the choices of modified D shape coils and the reduction of stresses in the conductor-which become more serious in scaling-up and high-T/sub c/ superconductor (HTSC) current leads for covering weak points due to thermal loss in a module-type SMES which need many current leads. Some other points are also studied such as the design of the cooling system in which a single coil quench does not induce that of others, and harmonics suppression in the SMES power converter system.

Aluminum stabilizer, which is used in composite superconductors, in external fields at 4.2K prvides a remarkable enhancement of magnetoresistance as compared to predictions by conventional theory. In order to study the cause of this anomalous behavior, we measured the electric resistivities of copper-clad aluminum conductors having rectangular cross-sections in various magnetic fields at 4.2K. The measured values depend on the magnitude and orientation of the applied magnetic field with respect to the sample; the resistivity being several times larger for a parallel field. We calculated the current distributions in the conductors by solving Maxwell's equations, taking the Hall effect into consideration for evaluating resistivities. The predicted resistivities were consistent with our experimental results, leading us to conclude that the current caused by the Hall effect is the main origin of the anomalous magnetoresistance and its anisotropy. Finally, we discussed a method to reduce the anomalous resistivity.

Magnetic chromatograph is a techniques that use magnetic force to separate small particles. It is interesting because the magnetic column can be used repeatedly and does not produce secondary wastes. In order to increase the efficiency of the separation, the magnetic force is desired to be as large as possible. The magnetic force increases in proportion to the magnetic field gradient, and when the source of the magnetic force is a wire, the magnetic field gradient increases in inverse proportion to the diameter of the wire. Therefore, it is estimated that an assembly of ferromagnetic nano-wires can produce large magnetic force. Anodized porous alumina has ordered and uniform nanometer-sized hole arrays. Various materials including ferromagnets, such as Fe, Ni and Co, can be easily electrodeposited from the bottoms of the holes, and the holes can be filled with nano-wires. These ferromagnetic wires have nano-meter sized diameters. Therefore, they are assumed to be able to produce strong magnetic force. We propose to apply ferromagnetic nano-wires in porous alumina arrays to magnetic force generators for magnetic chromatograph.

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.

We have developed a protein crystal formation system, which can, on the ground, suppress convections, exerting magnetic forces on the solution including proteins. The protein formation system consists of a superconducting magnet system, protein crystallization cells, and observational equipment; the latter two devices are placed in the magnet bore. The superconducting magnet system includes two coil groups, each generating a magnetic field opposing in direction to each other. The product of magnetic flux density and its spatial gradient is proportional to the magnetic force and needs to be approximately 1400 T2/m in order to levitate water. The magnet is operated in persistent current mode. The crystallization cells are made of a transparent plastic on a plate. The experimental space and cells can be controlled between 4°C and 20°C. The observational equipment, which is a kind of periscope, enables in-situ observation of protein solution in high magnetic fields. In order to optimize experimental conditions, we have also carried out a simulation study based on a solution flow model.