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ABSTRACT:The convective dispersion of a suspension of microscopic particles injected into an initially quiescent liquid is examined using a finite volume, Eulerian-Eulerian computational fluid dynamics model. The motion of the phases is coupled with particle-particle interactions represented using a solids pressure formulation. The solids are of greater density than the liquid and settle after injection, creating a liquid flow field that eventually results in a toroidal plume of solids descending through the liquid phase. Excellent qualitative agreement between predicted plume shapes and published experimental shapes are obtained for 50 μm particles. For particle diameters less than 50 μm, the solids plume exhibits a toroidal recirculation in the liquid and particle phases relative to the downward motion of the plume. However, for particle diameters greater than 375 μm, a toroidal liquid recirculation is not predicted within the solids plume. The initial shape of the plume immediately after injection is affected by all parameters: density ratio, liquid viscosity, particle diameter, and injection parameters. It is concluded that it is this initial shape that determines the subsequent plume shape at a particular depth of penetration for varying solids density and liquid viscosity.

Objectives/Scope Many midstream operators are developing plans to introduce Hydrogen (H2) into natural gas networks in concentrations of 0 to 20%. It is important to keep the concentration in all locations in the network within these limits, to reduce H2 induced cracking of pipelines and because most burners in the US are not designed for the different heating values (Wobbe Index) associated with the H2 mixtures, and flame speed present with H2 flames. This paper presents a model which dynamically tracks H2 concentrations, and associated Wobbe Index, in a complex delivery network and discusses the operational challenges associated with the introduction of H2 in these systems. Methods, Procedures, Process The model is based on proven technology which has been used on gases of variable quality for 30 years. The key item currently however is the new addition of H2 to the composition mix. The model is dynamic and responds to changes in the H2 concentration and flowrate. It is envisioned that the H2 supply to these networks will be variable (for example solar generated H2). This paper will present several case studies showing how H2 affects an existing gas distribution network and the paper will also discuss how H2 impacts the thermodynamics used in the calculation engine. Results, Observations, Conclusions The case studies will show that for even simple events like a customer trip, high concentration H2 packets can travel into pipelines that normally do not receive H2. As H2 travels through the pipeline, parameters within the system start to change such as the pipeline pressure drop increases and the compressor duty and outlet temperature increase. Novel / Additive Information The model tracks gas packets dynamically in the network (packet size is based on dispersion length) and calculates the density and energy content based on the local concentration. It then has a built in EOS (equation of state) based on GERG 2008 to calculate the density. Even with this complexity the model can run at speeds 100 times real-timefor a network that has approximately over 1,000 km of pipe.

Coal bed methane (CBM) operations reduce the reservoir pressure to desorb gas from the coal matrix. Internationally, this is often achieved by drawing down water through pumping from the reservoir, by surface or down-hole pump. Pumping water lowers the bottom-hole pressure and also provides a first pass separation of water and gas in the well annulus. Set-point pressure pumps are typically used to pump water up the inner tubing, whilst gas is produced in the outer annulus. In many operating CBM applications this separation is adequate, removing a large percentage of bulk and droplet-based water from gas, negating the need for secondary surface separation. Key to this separation is the ability of the water to drain downwards to the bottom of the well without being carried over with the upwards moving gas. This is a counter-current flow regime with large superficial gas velocities (as high as 30 m/s) and small superficial liquid velocities (less than 1 m/s). The annular/droplet regime is prevalent and there is potential for droplet carry-over with gas, affecting the need for further separation. Computational fluid dynamics (CFD) was used to model the process of gas and water separation down hole in the perforation zone to calculate the fate of water droplets as they pass downwards counter-current to upwards moving gas. A flow envelope was developed to calculate the carry-over liquid flow rate for a range of gas flow rates. This work assists the design requirement for wellhead surface separation or otherwise for Australian CBM applications.