Rotten citrus fruits, which spread odor gas during shipping season, pose a severe problem in Jeju Island, Republic of Korea. The existing methods for food waste management such as composting using electro-drying and microorganisms have a high electricity cost and require a precise temperature control, respectively. Herein, we conducted a basic numerical study on a plasma reactor using microwave plasma and liquefied petroleum gas as a combined heat source for drying and composting rotten citrus fruits. To determine the design and operating conditions of the plasma reactor, the thermal flow characteristics inside the reactor were analyzed using a computational fluid dynamics code in ANSYS-fluent. In particular, the temperature distribution in the plasma reactor was simulated at different air flow rates of the centrifugal fan. The numerical simulation accuracy was evaluated by comparing the numerical results and actual experimental data. The temperature of the reactor decreased with the increase in the air flow rate of the centrifugal fan. Above 10 m/s, the temperature of the drying chamber and the exhaust gas remained almost constant at 507 K. In the present work, the calculated temperature shows a difference 1.13 % from the measured temperature at the combustion chamber.

We performed a synthesis of metal-boride nanoparticles, which can shield both gamma rays and neutrons, and investigated the radiation shielding performance of the material. Titanium and nickel boride nanoparticles were synthesized in a triple thermal plasma jet system using titanium (Ti), nickel (Ni), and amorphous boron (a-B). The average sizes of the titanium boride and nickel boride were 46.3 and 31.4 nm, respectively. In the titanium boride, the TiB 2 phase was the major crystal structure with TiB as a minor phase, and the peak of the starting materials could not be observed. On the other hand, the nickel boride indicated a major crystal structure of NiB with an Ni peak observed from X-ray diffraction graphs. The synthesized powders were applied as a coating material to shield the radiation. The shielding performance of the coating material made with synthesized powder was analyzed using 137 Cs source (662 keV). The attenuation coefficient of the nickel boride and titanium boride was 0.246 and 0.197 cm −1 , respectively. Boron-rich boride is stable when confronting neutron and other types of radiation. Therefore, synthesized metal-boride nanoparticles can be used as substitutes for heavy metals, which become radioactive on account of neutron exposure.