No abstract

No abstract

The performance of Luvicap EG was investigated to verify the efficacy of mixing kinetic hydrate inhibitors (KHIs) and monoethylene glycol (MEG) while varying the pH conditions in an aqueous phase. The relative torque changes were relatively stable in an early stage of hydrate formation; however, they started to increase and showed fluctuation when the hydrate fraction was larger than the transition value. Interestingly, the transition value was smaller for the base solution, suggesting that the efficacy of Luvicap deteriorated at high pH conditions. MEG was added to the Luvicap solution to confirm its synergistic effect at low and high pH conditions. The addition of MEG effectively slowed down the growth rate and the relative torques for the acid and the neutral solutions. However, for the base solution, dramatic changes in the growth rate were observed, followed by a severe fluctuation of the relative torque. Visual observation suggested that the catastrophic hydrate growth had occurred, and the formed hydrate particles were prone to deposit on the autoclave wall and to the impeller. Additional experiments varying the impeller speed indicated the occurrence of a thick hydrate film on the interface between the gas and the aqueous phases at a slow impeller speed, which increased the resistance-to-flow. Under all pH conditions, at 200 rpm, fluctuation of the relative torque was observed, and a high relative torque or severe fluctuation was observed at high pH conditions than in other pH conditions. It can be concluded that Luvicap EG would perform well under a high pH and a high impeller speed with an enhanced effect by the addition of MEG. However, a low pH and a low impeller speed would be the worst combination of exacerbating the agglomeration of hydrate particles, which would result in hydrate blockage.

No abstract

No abstract

The free-surface motions interacting with structures are investigated numerically using the Moving Particle Semi-implicit (MPS) method proposed by Koshizuka et al. (1996) for solving incompressible flow. In the method, Lagrangian moving particles are used instead of Eulerian approach using grid system. Therefore the terms of time derivatives in Navier-Stokes equation can be directly calculated without any numerical diffusion or instabilities due to the fully Lagrangian treatment of fluid particles and topological failure never occur. The MPS method is applied to the numerical study on the fluid impact loads for wet-drop tests in a LNG tank, and the results are compared with experimental ones.

No abstract

No abstract