(713f) Continuous-Flow Reforming of Hydrocarbons Underground: Kinetic Analysis

Water-producing oil wells are potential candidates for clean and economic production of hydrogen, syngas and low sulphur fuels. This may be achieved by transforming the passive production well into a high-pressure, high-temperature, continuous-flow reactor, eliminating the need for above surface reforming steps, and reducing the carbon footprint. As a part of this study, thermodynamic analysis of hydrothermal gasification of hexadecane, a heavy-saturate oil model was carried out and presented in the AIChE meeting 2010. The present work reports the experimental analysis of the hydrothermal gasification of hexadecane at various reaction residence times , temperatures, and H₂O₂ concentrations. The aim is to develop an uncatalysed continuous-flow hydrothermal reactor model for hydrogen generation from hydrocarbon resources. While some researchers have studies hydrothermal reactions of hydrocarbons in batch-type reactors, none has determined the kinetic data of heavy-saturate hydrocarbons in continuous flow systems (Arai et al, 2000, Watanabe et al, 2001, Watanabe et al, 2000, and Tsuzuki et al, 1999). Continuous flow systems offer high potential for commercial scale-up compared with batch systems. Online gas analysis was carried out using a quadruple mass spectrometer while produced oil-water residue was analysed using GC-MS. Moderate yields of syngas, and cracked n-alkanes/1-alkenes (C₉-C₁₅) were produced at 300 – 565 ^oC and 250 bar. The conversion of hexadecane has been found to be inversely proportional to the residence time, and directly proportional to the water density. In addition, increasing the concentration of H₂O₂ enhanced the gasification of hexadecane as observed by the significant rise in the gas flowrate. On the other hand, coke formation due to hexadecane thermolysis was experienced at 565 ^oC and 250 bar. It was also found that increasing the pressure at a constant temperature and H₂O₂ concentration reduces the formation of n-alkanes/1-alkenes products while it negatively causes the undesirable oligomerisation of hexadecane. Results produced were compare with previously reported catalytic batch systems (Arai et al, 2000, Watanabe et al, 2001). Additional improvements have been introduced into the experimental system including mixing the reactants at the desirable reactor temperature, and decomposing the H₂O₂ in a separate reactor prior to oxidising the hexadecane feed. This experimental analysis is also complimented with heat, mass and momentum balance using COMSOL enabling direct characterisation of the hydrothermal reactor.