Population balance model for nucleation, growth, aggregation, and breakage of hydrate particles in turbulent flow

Numerical simulation of sulfur particle agglomeration at bends of high sulfur natural gas gathering pipelines based on Euler-PBM coupling

Sulfur deposition can result in an increase in the wall thickness of high-sulfur natural gas gathering pipelines, leading to issues like unstable pipeline flow. It is crucial to reveal the aggregation of sulfur particles at key locations of high-sulfur natural gas gathering pipelines to predict the location and amount of sulfur deposition in the pipelines. In this paper, the Euler-PBM (Population balance model) coupling is used to establish a numerical simulation model of gas-solid two-phase pipe flow accompanied by sulfur particle agglomeration in the pipe bends, focusing on the influence of sulfur particle volume fraction, pipe inclination angle and inlet flow velocity on sulfur particles agglomeration behavior. The results show that the sulfur particles have a significant agglomeration effect at the bend of the collecting pipeline, and the agglomeration growth occurs to different degrees throughout the bend, and the main area of sulfur particles agglomeration is near the top wall of the pipeline, followed by other areas near the wall of the pipeline. When the inlet volume fraction of sulfur particles was increased from 0.05 to 0.25%, and the inclination angle of the pipe was increased from 30° to 90°, the distribution range of sulfur particle size after agglomeration became wider, and the maximum size of sulfur particles was 187.56 μm, and the effect of sulfur particle agglomeration was enhanced; the inlet flow rate was increased from 3.0 to 9.0 m/s, and the reduction range of sulfur particle size after agglomeration was 5.68-9.87 μm. The maximum particle size of sulfur particles also decreased, and the effect of sulfur particle agglomeration was weakened.

Mesomorphology of clathrate hydrates from molecular ordering

Clathrate hydrates are crystals formed by guest molecules that stabilize cages of hydrogen-bonded water molecules. Whereas thermodynamic equilibrium is well described via the van der Waals and Platteeuw approach, the increasing concerns with global warming and energy transition require extending the knowledge to non-equilibrium conditions in multiphase, sheared systems, in a multiscale framework. Potential macro-applications concern the storage of carbon dioxide in the form of clathrates, and the reduction of hydrate inhibition additives currently required in hydrocarbon production. We evidence porous mesomorphologies as key to bridging the molecular scales to macro-applications of low solubility guests. We discuss the coupling of molecular ordering with the mesoscales, including (i) the emergence of porous patterns as a combined factor from the walk over the free energy landscape and 3D competitive nucleation and growth and (ii) the role of molecular attachment rates in crystallization-diffusion models that allow predicting the timescale of pore sealing. This is a perspective study that discusses the use of discrete models (molecular dynamics) to build continuum models (phase field models, crystallization laws, and transport phenomena) to predict multiscale manifestations at a feasible computational cost. Several advances in correlated fields (ice, polymers, alloys, and nanoparticles) are discussed in the scenario of clathrate hydrates, as well as the challenges and necessary developments to push the field forward.

Numerical Simulation Study on the Flow Field and Separation Efficiency by Built-In Twisted Tape in the Hydrocyclone

Aiming at the separation of mud and sand in natural gas hydrate, for the designed built-in twisted tape hydrocyclone, the numerical simulation method was used to study the effects of different types of built-in twisted tape and operating conditions on the internal flow field of the hydrocyclone, separation efficiency, and influence of hydrate particle size distribution. The research results show that the built-in twisted tape has the same swirling direction as the hydrocyclone, which is beneficial to improving the swirling intensity, and the ability to carry and separate solid particles is obviously enhanced. The built-in twisted tape hydrocyclone with a length of 300 mm has better separation efficiency and internal flow field stability. By changing the conditions of the inlet velocity and the initial concentration of hydrate particles, the comparison shows that when the inlet velocity is 8 m/s, the volume of mud and sand is 25%, the initial concentration of hydrate particles is 15%, and the built-in tape is 300 mm long. The tape hydrocyclone has the best separation efficiency. Compared with the basic hydrocyclone, the built-in twisted tape hydrocyclone with a length of 300 mm increases the separation efficiency of mud and sand by 7.49%, while the pressure drop only increases by 2.67%, showing the superiority of the built-in twisted tape structure.