Investigation on hydrates blockage and restart process mechanisms of CO₂ hydrate slurry flow

Abstract

Being an alternative environment-friendly fluid for the refrigeration process, CO 2 hydrate slurry is undesired to result in hydrate blocking in the system.A series of water-based CO 2 hydrate slurry experiments were conducted to investigate hydrate blockages in a high-pressure flow loop. Blocking would occur soon after CO 2 hydrate formation onset. Rapid restart process after the first blocking was found to have serious consequence by inducing a fast hydrate regrowth and an irreversible secondary blocking. The mechanisms of the first blocking and the secondary blocking after the restart process were proposed, based on the observed phenomena and the particle chord length distribution data recorded by focused beam reflectance measurement probe.The influences of the initial flow rate on the supercooling, the induction time, the restart time, and the required time for the secondary blocking after the restart process were analyzed. The understanding on the blocking and restart process mechanisms of CO 2 hydrate slurry is important not only in the development of hydrate-based refrigeration system but also in the field of flow assurance in the oil and gas pipeline or for other applications such as the replacement of methane by CO 2 in the naturally occurring hydrate exploration.

Hydrate Deposition Model and Flow Assurance Technology in Gas-Dominant Pipeline Transportation Systems: A Review

“…Schematic diagram of the FBRM and its working principle. This figure was reprinted with permission from ref . Copyright 2018 Wiley-Blackwell.…”

Study on the blockage mechanism of carbon dioxide hydrate slurry and its microscopic particle characteristics

“…29 For the further explanation of the phenomenon that under the different ow rates, the number of large particles in the system increased aer hydrate formation, a method of square weighted particle chord length was introduced here in order to signicantly characterize the changing trend of large particle chord length aer hydrate formation. 36 The details were shown as Fig. 15-17.…”

“…This trend has been conrmed by some researchers. 23,29,[31][32][33][34][35][36] 3.4.2 The distribution of the average and square weighted particle chord length. In order to better understand the particle chord length at different time during the CO 2 hydrate formation, we specially studied the average particle chord length and square weighted particle chord length in this process, as shown in Fig.…”

“…It proved that square weighted particle chord length was more sensitive to the collision and coalescence of particles. 33,36 The uctuated period aer hydrate formation reected that the large particles experienced breakage and coalescence at the same time under the shear effect, which was a dynamic equilibrium process, as shown in Fig. 21.…”