| Summary: | 碩士 === 義守大學 === 材料科學與工程學系 === 91 === The Gasification and Oxidization of Organic Wastes in Near and Supercritical Water
ABSTRACT
Oil- and sewage-sludges from Chinese Petroleum Company and toluene were thermally gasified in near and supercritical water. The gasification was an isochoric process in a batch reactor. The investigated temperatures ranged from 360 to 420 ℃, and the final pressures achieved were between 26 and 33 MPa. The gas product is mainly composed of C1 ~ C4 , hydrogen and carbon dioxide. In the gasification of oil- and sewage-sludges, methane is the most abundant product, ~50%, and hydrocarbons of C2, C3 and C4 take up ~18%, ~ 11%, and ~7%, respectively. Hydrogen gas contributes less than 10%. Carbon dioxide content is close to 6%. When toluene were gasified, methane is the most abundant product, ~51%, and hydrocarbons of C1, C2, C3 and C4 take up ~15%, ~ 5%, ~ 2%, and ~1%, respectively. Carbon dioxide contributes almost 26%. Without the addition of nickel to the sewage sludge, the temperature dependence of the product distribution were found to be mild over the entire range of temperatures. However, the nickel effect on the oil sludge is quite complicated.
Toluene and Di-Methyl Formamide (DMF) were also oxidized in supercritical water. Hydrogen peroxide , oxygen gas or air is employed as the oxidant to destruct toluene and DMF. The experiments of toluene were carried out with a batch reactor and that of DMF was with a continuous system. Liquid effluent is analyzed for the concentration of toluene or DMF to investigate the Destruction and Removal Efficiency (DRE). The effects of temperature, reaction time, density in the reactor, the weight fraction of toluene or DMF, and the weight ratio of oxidant to toluene or DMF on the DRE are investigated. It is found that the DRE increases with temperature, reaction time, density in the reactor, and the weight ratio of oxygen to toluene or DMF. Increasing the amount of loading and the weight fraction of toluene or DMF in the feed will significantly decrease DRE. In the case of oxidation with air, 99.9% DRE was achieved when the weight ratio of air to DMF is larger than 6.77. This work provides useful information for recycling wastes from industrial sites, and the role of water in pyrolyzing them.
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