(210a) Offshore Floating Packed-Bed Reactors: Current Status, Key Challenges and Potential Solutions

Packed beds as classical multiphase contactors and reactors are widely employed in offshore oil and gas industries to treat and refine hydrocarbons extracted from undersea reservoirs [1]. Such packed beds are embarked on ships such as floating production, storage and offloading (FPSO) and floating liquefied natural gas (FLNG) for onboard treatment in the vicinity of the extraction site [2]. Nevertheless, operation of floating reactors and separators on embarked FPSO or so-called mini-refineries undergoes remarkable technical and operational challenges stemming from the complex sea conditions.

Thanks to a new state-of-the-art experimental setup combining a hexapod robot with six-degree-of-freedom motions and an embarked column instrumented with capacitance wire-mesh sensors, the hydrodynamic behavior of floating packed beds with different gas-liquid contacting modes was examined. Ship motions and inclination initiated by marine swells were inferred to impact the performance of onboard packed-bed reactors. Translational and rotational motions of the column led to remarkable phase maldistribution and, consequently, loss of efficiency. Besides, in order to understand detailed features of the flow patterns and mixing behaviors inside a moving reactor, three-dimensional computational fluid dynamics (CFD) simulations of multiphase flows in floating packed beds were implemented (CFD). The sensitivity of the hydrodynamic characteristics to column oscillations was assessed based on the experimental results of residence time distribution (RTD) studies and CFD simulations.

Finally, to reduce those detrimental effects of ship oscillations on the performance of multiphase packed-bed reactors, two new operational techniques were proposed: (i) low-shear rotation of the reactor and (ii) modulation of liquid and/ gas flow at the reactor inlet. The superimposed low-shear rotation of packed beds allows controlling pressure drop, liquid saturation, liquid residence time and dispersion by tuning an appropriate rotational velocity depending on the type of imposed motions to the column. Liquid wave induced by the flow modulation technique showed its ability to reduce fluid maldistribution in oscillating packed beds. Hence, these two concepts can be regarded as potential methods for process intensification in offshore production units where packed-bed reactors are used.

References

[1] Kim, H.-J., Choi, D.-K., Ahn, S.-I., Kwon, H., Lim, H.-W., 2013. GTL FPSOâ??An Alternative Solution to Offshore Stranded Gas, Offshore Technology Conference, Houston, Texas, USA, May 6-9.

[2] Leffler, W.L., Pattarozzi, R., Sterling, G., 2011. Deepwater petroleum exploration & production: A nontechnical guide. 2nd ed. PennWell Books, Tulsa, Oklahoma, USA.