Modelling agglomeration and deposition of gas hydrates in industrial pipelines with combined CFD-PBM technique

Study on Continuous Hydrolysis in a Microchannel Reactor for the Production of Titanium Dioxide by a Sulfuric Acid Process

The development of a continuous hydrolysis process of titanium sulfate is an innovation to the traditional production process of titanium dioxide by the sulfuric acid process. In the experiment, a microchannel reactor was designed, and the hydrolysis rate of titanium sulfate, the particle size, and particle size distribution of metatitanic acid agglomerates were used as indicators to investigate the effect of operating conditions on the continuous hydrolysis of titanium sulfate. The results have shown that as the amount of dilution water increased, the hydrolysis rate of titanium sulfate decreased, and the particle size of primary aggregates of metatitanic acid increased from 39 to 54 nm. As the alkali mass concentration of dilution water increased, the hydrolysis rate of titanyl sulfate increased, and the particle size of primary aggregates of metastatic acid first decreased and then increased, and the particle size range was 40-48 nm. As the flow rate increased, the hydrolysis rate of titanyl sulfate increased, and the particle size of primary aggregates of metatitanic acid dropped from 59 to 43 nm. Compared with the batch hydrolysis operation, the continuous process has stronger anti-disturbance ability, significantly shorter operation time of the reaction section, and narrower particle size distribution of the product metatitanic acid.

Opportunities and Challenges to Develop Digital Twins for Subsea Pipelines

A vision of the digital twins of the subsea pipelines is provided in this paper, with a coverage of the current applications and the challenges of the digital twins in the design, construction, service life, and assessments of life extension. Digital twins are described as a paradigm combining multi-physics modelling with data-driven analytics, which are used to mirror the life of its corresponding twin. Realistic virtual models of structural systems are shown to bridge the gap between design and construction and to mirror the real and virtual worlds. Challenges in properly using the new tools and how to create accurate digital twins considering data acquired during the construction phase are discussed. The key opportunities for improved integrity management using the digital twin are data contextualization, standardization, automated anomaly detection, and learning through sharing. The collection, interpretation and sharing of data, and cyber-security are identified as some of the main challenges.

Numerical Simulation of Swirl Flow Characteristics of CO2 Hydrate Slurry by Short Twisted Band

The development of oil and gas resources is gradually transferring to the deep sea, and the hydrate plugging of submarine pipelines at high pressures and low temperatures is becoming an important problem to ensure the safety of pipeline operations. The swirl flow is a new method to expand the boundary of hydrate safe flow. Numerical simulation of the hydrate slurry flow characteristics in a horizontal pipeline by twisted band has been carried out, and the flow of CO₂ hydrate slurry in low concentration has been simulated by the RSM and DPM models. The results show that the heat transfer efficiency is also related to Re and particle concentration. The velocity distribution has the form of symmetrical double peaks, and the peaks finally merge at the center of the pipeline. Vortexes firstly appear on both sides of the edge of the twisted band, and then move to the middle part of the twisted band. Finally, the vortex center almost coincides with the velocity center. The rotation direction of hydrate particles is the same as the twisted direction of the twisted band, twist rate (Y) is smaller, Re is larger, and the symmetric vortex lines merge farther away. The initial swirl number is mainly related to Y, but not Re. The swirl flow attenuates exponentially, and its attenuation rate is mainly related to Re, but not Y. Compared with ordinary pipelines, the swirl flow can obviously improve the transportation distance of hydrate slurry.

Effects of Solid Precipitation and Surface Corrosion on the Adhesion Strengths of Sintered Hydrate Deposits on Pipe Walls

A hydrate directly growing and sintering on a pipe wall is an important hydrate deposition case that has been relatively unexplored. In the present study, the adhesion strengths of a sintered cyclopentane (CyC5) hydrate deposit under different solid precipitation and surface corrosion conditions were measured and discussed. It was found that the hydrate adhesion strengths increased by 1.2-1.5× when the soaking time of the carbon steel substrate in a 5 wt % NaCl solution increased from 24 to 72 h, which reduced the water wetting angle from 112 ± 3.5° to 94 ± 3.3°. The wax coating reduced the strength of CyC5 hydrate adhesion by up to nearly 20-fold by reversing the substrate wettability and affecting the hydrate morphology. The measurements performed on scales indicate that calcium carbonate scales strengthen the adhesion strength because of the decrease in the water wetting angle. In addition, honeycomb holes on the surface reduce amplification. Furthermore, settling quartz sand on the wall reduced the adhesion strengths by decreasing the effective sintering area of the hydrate on the underlying base. Finer sand and higher concentrations led to lower strengths. On the basis of the verified linear correlation between the hydrate adhesion strength and the adhesion work of droplets on different substrates and the influence of water conversion during deposition, both an equation and a key constant parameter were obtained to predict the sintered hydrate deposit adhesion strengths on substrates.