Supercritical water oxidation (SCWO) has potential for use in on-site treatment of organic waste because organics can be rapidly decomposed in a closed system. In this study, SCWO of toxic parts of the puffer fish was examined. SCWO of the puffer fish ovary was conducted at 400°C and 25 MPa with an excess amount of oxidant. Tetrodotoxin contained in the ovary was decomposed in 1 min. The small amount of solid residue became constant after 1 min of reaction and was thought to be ash derived from the ovary. In the liquid phase, 4% of total organic carbon (TOC) remained after 10 min of reaction, and a major component was acetic acid. By increasing the reaction temperature to 500°C, remaining TOC decreased to 0.4% after 1 min of reaction. However, ammonia and other N compounds remained in liquid phase after the reaction at 500°C.
The dry-type photochlorination of poly(vinyl chloride) (PVC) was carried out by using a rotary vessel reactor and a fluidized bed reactor in order to obtain useful information for designing and industrializing a dry-type photoreactor. The results of the reaction rate analysis showed that the chlorination reaction rate could be expressed by an overall rate equation of 1st order with respect to the concentration of poly(vinyl chloride) and of 0.5-order with respect to the concentration of chlorine gas. The overall reaction rate constant K [1/min] followed the Arrhenius equation. K was also strongly correlated with the irradiated ultraviolet power per mole of PVC charged in the reaction vessel, I [mW/mol]. Furthermore, K was affected by the mixture conditions of the powder (number of rotations in the rotating vessel reactor). Hence, an optimal dry-type photoreactor can be designed by further clarifying the relationship between the overall reaction rate constant and the reaction conditions and mixture conditions.
The power produced from renewable energy sources should ideally be converted into fuel for long-term storage and long-distance transportation. In this study, it was assessed a wind turbine of 3000 kW class was installed at six locations with good wind conditions in the Tokai region, and that the electricity generated, estimated based on meteorological data, was converted into hydrogen by electrolisys of water and transported to urban consumers after (1) compression, (2) liquefaction, (3) conversion into liquefied methane or (4) conversion into organic hydride. These four procedures for conversion and transportation were assessed from the viewpoint of energy efficiency and CO2 emission. It was found that fuel consumption, CO2 emission, and energy consumed for transportation increased with transportation distance from turbine to consumer irrespective of the type of conversion and transportation procedure. Energy loss during transportation was found to be significant for the compressed hydrogen procedure, but not for the other three procedures. When the energy loss ratio is defined based on the heating value of liquefied methane, the liquefied methane procedure had the best energy efficiency for long-distance transportation, while compression of hydrogen was most efficient for short-distance transportation. On the other hand, the energy efficiency of liquefied methane procedure is decreased based on the heating value of hydrogen. It was also found that CO2 emission is lowest for the liquefied methane procedure, since fewer tank trucks are needed to transport liquefied natural gas (LNG), with the result that this has the smallest environmental impact among the four conversion and transportation procedures.