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Blockage of pipelines due to hydrate formation is a major problem for subsea flow assurance. Induction time for hydrate formation from the multiphase system within a pipeline is a critical parameter to determine whether hydrates may form at a given time. In this work, the induction time for hydrate formation in water-in-oil emulsions was investigated under different conditions. For this purpose, an autoclave with an online viscometer was designed and built. Based on the viscosity variation observed in the experiments during hydrate formation, a new avenue for defining induction time is proposed, which should be more convenient for determining the hydrate formation time in some pipelines. As hydrate formation in emulsions is more complicated than in pure water, the effects of several factors were considered in this study, including water cut of the emulsions, shear rate, driving force, and memory effect. Additionally, wax precipitation is also a common problem in subsea pipelines and can impact flow assurance when hydrate formation and wax precipitation both occur. Consequently, the effect of wax solid particles on hydrate formation was also considered in this work. The presence of wax particles is observed to impede hydrate formation. In this work, it is determined from induction time that the hydrate formation is initiated at the water–oil surface for water-in-oil emulsion. Moreover, the memory effect can shorten induction times of hydrate formation due to the remaining small CO2 bubbles at the surface of water droplets.

In situ gasification chemical looping combustion (iG-CLC) is a promising coal combustion technology for implementing CO 2 capture with a low energy penalty. A novel iG-CLC cold experimental system was developed in the authors' previous work (Ind. Eng. Chem. Res. 2013, 52, 14208). It mainly consists of a high-flux circulating fluidized bed (HFCFB) riser as the fuel reactor and a cross-flow moving bed as the air reactor. As an extension of that work, in this study, we further optimized the iG-CLC system by redesignung the air reactor to enhance the carrying capacity of the gas flow and developing a two-stage separation system by adding a second-stage cyclone to the original first-stage inertial separator. Stability in operation and flexibility in adjusting operating parameters were achieved with the improved system. In the riser (fuel reactor), higher solids fluxes and solids holdups were achieved, which should enhance the gas−solid contact and promote the complicated heterogeneous reactions. In the moving bed (air reactor), the carrying capacity of the gas flow was significantly enhanced, which should lead to a great increase in the system power capacity. The confirmation of the ability to control the gas flow directions in the two reactors means that the gas bypassing between the two reactors can be restrained so as to ensure a high CO 2 concentration in the exhaust of the fuel reactor. The high global separation efficiency and selective separation efficiency of the new two-stage separation system for fine particles indicate that a high combustion efficiency of coal can be achieved with a hot iG-CLC system.

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