中部電力

Ammonia-coal co-firing for thermal power generation has recently attracted considerable attention as a game-changer for decarbonization. However, its combustion with a 20 % or higher ammonia (NH3) ratio emits higher amounts of nitrogen oxides (NOx) than coal-fired combustion, surpassing the denitration capabilities of existing selective catalytic reduction (SCR) systems, resulting in excessing the regulation value determined by agreements on environmental conservation. To eliminate the NOx remaining after SCR, we propose a plasma-chemical hybrid process (PCHP) as a NOx treatment technology that can be easily retrofitted into existing exhaust gas treatment equipment. PCHP consists of NO oxidation using plasma ozonizers and NO2 reduction by existing desulfurization equipment. Assuming the ozone injection in the flue gas duct between the SCR and desulfurization equipment, we conducted NO oxidation and the simultaneous removal of NOx and sulfur oxides (SOx) for a simulated flue gas comprising low-concentration NO and high-concentration sulfur dioxide (SO2). This was achieved using an ozone injection tower that simulated the flue gas duct and a calcium carbonate-slurry based SO2 absorption tower that simulated the desulfurization equipment. The results show that even under conditions containing SO2 at a concentration 46-fold higher than that of NO, the NO oxidation by O3 was achieved without the effect of SO2. When the SO2 removal efficiency reached 99 %, which is equivalent to that of an actual facility, an NOx removal efficiency of 45 % was attained. Therefore, an NOx removal efficiency of 45 % can be also expected for an actual facility, contributing to further reductions in NOx.

In recent years, microgrids powered by Grid-Forming (GFM) inverters have attracted increasing attention as a means of maintaining power supply during disasters when existing transmission networks are disrupted. Generally, the rated capacity of GFM inverters is limited, and when an overload causes the current limiter to activate, the resulting voltage drop makes it difficult to continue operation. This study proposes a Hybrid Demand Response (DR) scheme for Variable Refrigerant Flow (VRF) air conditioners, which performs both active power DR and reactive power DR simultaneously to reduce GFM inverter current and maintain the microgrid. Simulations were conducted for a 1 MW class microgrid model. The results show that Hybrid DR reduces inverter peak current by about 5%, limits the rise in indoor temperature to approximately 0.3 °C. In addition, Hybrid DR suppresses the post-DR active-power rebound by roughly 10% compared with conventional active-power DR.

The Aso-3 tephra is one of the most significant widespread marker layers from the Middle to Late Pleistocene, generated by a large caldera-forming eruption at the Aso volcano in Kyushu, southwestern Japan. Despite its importance, a distal co-ignimbrite ash correlative has yet to be clearly identified, primarily because although volcanic glass shows a broad chemical composition range, available refractive index and major-element glass data remain limited. This issue has made it difficult to identify the distribution area of the widespread Aso-3 tephra and utilize it as a marker layer. Consequently, the ability to synchronize terrestrial and marine records from Japan and the northwestern Pacific during the Marine Isotope Stage (MIS) 6/5 transition is limited. This study reports the identification of a previously unrecognized tephra layer (SKR tephra) within the basal part of the Furuya Formation in the Omaezaki area of central Japan as Aso-3 tephra. Petrological and geochemical analyses reveal that the SKR tephra consists of two compositionally distinct glass groups, whose major element composition closely corresponds to that of the Aso-3B unit within the Aso-3 pyroclastic flow deposits. Furthermore, the glass composition of SKR tephra matched that of cryptotephra (MD26.70 tephra) contained within a sample taken from marine core MD012422 off the coast of Shikoku at a depth of approximately 26.7 mbsf. The MD26.70 tephra was deposited during the MIS 6/5 transition, demonstrating that the SKR tephra represents a valuable stratigraphic marker synchronizing terrestrial and marine records for this period. Consequently, the SKR tephra contributes to refining the regional tephra chronology of central Japan. It serves as an indicator layer enhancing the potential for high-resolution paleoenvironmental reconstruction of the Japanese archipelago and the northwestern Pacific during the MIS 6/5 transition.

Changes in the characteristics of the insulating materials that compose the Capacitor Voltage Transformers (CVT) or insulation abnormalities in the oil-impregnated paper capacitors in the CVT are manifested as changes in the CVT transformation ratio. In this paper, a diagnostic method based on the measurement of CVT secondary voltage was investigated. The change in the CVT secondary voltage (calculated value) in the event of a single element breakdown of oil-impregnated paper capacitors is sufficiently large compared to the dispersion in the secondary voltage (measured value) of actual CVTs used in the substation. It was shown that CVT diagnosis is possible by comparing the secondary voltages of CVTs connected to the same bus bar in the substation with each other. A concrete example of the CVT diagnosis flow when applied to an actual substation is also presented.

Compact cyclotrons are required to produce radiopharmaceuticals used in targeted alpha-particle therapy, which is a promising treatment for patients with intractable cancers. To realize a compact cyclotron, we have proposed “Skeleton Cyclotron”—an air-core compact cyclotron using high-temperature superconducting (HTS) technology. This cyclotron consists of circular and non-circular coils, all wound with REBCO tape using a no-insulation (NI) winding technique. We have fabricated a 1/2-scale REBCO coil system of Skeleton Cyclotron called “Ultra-Baby-Skeleton Cyclotron”. In the experiment, the quench of the REBCO coil was observed at a current of 258 A before reaching the target current of 540 A. Mechanical deformation was confirmed in the quenching REBCO coil. Because the REBCO coils in Ultra-Baby-Skeleton Cyclotron are non-impregnated and non-insulated, they are considered vulnerable to deformation, such as the formation of gaps between the winding and the external reinforcement after cooling. Therefore, it is susceptible to the stress due to thermal shrinkage and additional stress due to the screening current. Numerical simulations also indicated that the screening current in the REBCO windings can exceed the energizing current. In this study, we analyzed the experimentally observed coil degradation in terms of stresses caused by electromagnetic forces, including the effect of screening currents.