@phdthesis{oai:nagoya.repo.nii.ac.jp:00007944,
 author = {廣坂, 和馬 and hirosaka, kazuma},
 month = {Mar},
 note = {Wet biomass is hard to handle as a fuel because it contains high moisture content and its drying process needs more energy input than it produces. Hydrothermal oxidation is one of the promising technologies to overcome this problem because this process does not need drying process at all. Thermal energy production from wet biomass by hydrothermal oxidation can be an innovative technology. Thermal energy production by hydrothermal oxidation of ethanol in subcritical water is experimentally and numerically studied as a fundamental research to develop a new concept of thermal energy production system. Experimental results using a lab-scale, plug-flow reactor system show that the moderate exothermic reaction occurs through subcritical water oxidation of ethanol. The conversion of ethanol depends on the preheating temperature and the concentration of oxidizer. At a lower concentration of oxidizer, the decomposition of ethanol is dominant and methane, carbon monoxide, and hydrogen are produced. At a higher concentration of oxidizer, the hydrothermal oxidation of ethanol is dominant and carbon dioxide is produced as well as thermal energy up to 576 kJykg-1. The rate of ethanol oxidation with oxygen in subcritical water is also investigated at temperatures between 170 and 230 °C and a fixed pressure 23.5 MPa. The residence time ranges from 180 to 580 s. The initial concentration of ethanol is set to 25 mmolyl-1 and the initial concentration of oxygen is changed from 50 mmolyl-1 to 150 mmolyl-1, which corresponds to the variation of equivalence ratio from 0.5 to 1.5. The first-order oxidation rate is derived from the experimental data at the equivalence ratio of 0.5. A global oxidation rate including the dependence on oxygen concentration is derived from the complete set of experimental data using a least-square method. The reaction orders for ethanol and oxygen are 0.86±0.03 and 1.15±0.05, respectively. The　resulting activation energy and the pre-exponential factor are 61±3 kJymol-1 and 102.05±0.24, respectively. Numerical simulation of subcritical water oxidation of ethanol is conducted in order to confirm whether the oxidation rate obtained in experiments using low ethanol concentrations is applied to the condition of higher ethanol concentrations. Steady-state solutions are obtained by solving governing equations and the conversion of ethanol and the temperature increase are compared with the experimental results. The simulation results agree with the experimental results qualitatively. It is found that the derived oxidation rate is generally applicable to the subcritical water oxidation of ethanol. The quantitative discrepancy is attributed to a neglecting the further oxidation of acetic acid into carbon dioxide, which generates additional heat. Thermal energy produced by hydrothermal oxidation is useable for electric power plants. Two kinds of hydrothermal oxidation power plants, direct and indirect type power plants are investigated. In the direct type power plant, the reactant is oxidized in a reactor and flows directly into a turbine. In the indirect type power plant, the reactant is oxidized in a reactor and the reaction heat is conveyed to the main water, which flows into a turbine. The amount of electric power and the energy conversion efficiency are calculated with ethanol, glucose, and peat solutions used as reactants. In both types of power plant, one steam turbine is employed for generating electricity with the maximum turbine inlet temperature of 650 °C. As the ethanol concentration increases, the amount of electric power and the energy conversion efficiency become higher. The maximum efficiency for the direct type power plant using ethanol solution is about 26.4% for 17.6 wt% EtOH solution at the reactor pressure of 10 MPa. The efficiency of the indirect type power plant is much lower than that of the direct type, but by pressurizing main water up to 4 MPa, the efficiency becomes higher up to 20.9% for 21.5 wt% EtOH solution., 名古屋大学博士学位論文 学位の種類:博士(工学)(課程) 学位授与年月日:平成20年3月25日},
 school = {名古屋大学, Nagoya University},
 title = {Thermal Energy Production by Hydrothermal Oxidation},
 year = {2008}
}