Abstract
The recovery system of methane hydrate from the deep ocean floor has not been established. As one of the recovery system of methane hydrate, gas-lift system is applied and investigated. The height 5m, diameter 0.1m, gas-lift system is experimented. The relationship between injected gas quantity and pumped water quantity is obtained. Unsteady one-dimensional two-phase flow in vertical pipe is calculated by compressible one-dimensional two-fluid model, as analysis of flow in recovery pipe of methane hydrate from the deep ocean floor. Primitive equations are mass conservation equations and motion conservation equations of each phase, relation of volume fraction and state equation of gas phase. From the calculation result, it is shown that the power requirement of the gas-lift system is 0.5 to 4% of power generated from recovered methane gas and the optimal gas injection depths exist. Next, the decomposition ratio of gas hydrate is measured using R-141b hydrate instead of methane hydrate. And it is suggested that the methane gas generated from decomposition of hydrate influences enough to decrease the injected gas flow rate. Thus, it is suggested that the gas-lift system can be economically effective recovery system of methane hydrate from the deep ocean floor.
