Fig. 5-Schematic diagram of Anti-agglomerants affecting hydrate bridge in pure water system
3.2 Effect of initial flow rate on flow characteristics. The flow curves of hydrate slurry under different initial flow rates in pure water system were showed in Fig. 6 . The flow characteristics of hydrate slurry under the initial flow rates of 230 L / h, 380 L / h and 550 L / h were investigated. The stable flow time of hydrate slurry was 23 min, 25 min and 30 min, respectively. Obviously, increasing the initial flow rate can significantly prolong the plugging time of hydrate slurry. From the perspective of hydrate nucleation, this may be due to the inhibition or delay of hydrate nucleation caused by high shear, which makes it difficult to reach the critical size required for hydrate formation. Moreover, high flow rate increases the flow friction ( heat generated ), weakens the cooling effect of temperature control system, inhibits the nucleation and growth of hydrate in the pipeline transportation system, and thus prolongs the induction period of hydrate. From the perspective of hydrate plugging mechanism, high-velocity fluid can not only destroy the formed hydrate polymer, but also reduce the probability of coalescence between hydrate particles, which greatly reduces the risk of plugging. Excessive flow velocity also increases the wall shear rate, making it difficult for hydrate particles to adhere to the wall. Hydrate deposition on the wall surface can reduce the flow area of slurry, so the flow shear rate of the deposition surface increases rapidly during hydrate deposition. When the surface flow shear rate reaches the critical point, the sediment will begin to fall off.