Multiphase Flow regimes
Multiphase Flow regimes
(OP)
My SAGD plant uses flash treaters to drive off residual water from our oil product. The pressure drop is induced by a pressure control valve upstream of the flash treater vessel. We experience severe erosion issues in the spool pieces downstream of the control valve. There is very likely sand in this stream that is being moved at high velocities once flashing in the line occurs.
The liquid and vapour velocities through the line place the flow regime as Slug Flow. I’ve read that this is an undesirable flow regime but I’m not sure if it’s for erosion issues or other various reasons. Increasing the amount of water in the oil would result in greater gas velocities and would move the flow regime into the Annular region. Would this help or perhaps make things worse?
The liquid and vapour velocities through the line place the flow regime as Slug Flow. I’ve read that this is an undesirable flow regime but I’m not sure if it’s for erosion issues or other various reasons. Increasing the amount of water in the oil would result in greater gas velocities and would move the flow regime into the Annular region. Would this help or perhaps make things worse?





RE: Multiphase Flow regimes
Annular flow will not cause such wide variations in control parameter swings and usually result in more stable and constant operations, but may invite other problems if the erosive particles or corrosive compounds are mostly contained in the liquid as opposed to the gas, etc. however annular flow is otherwise and generally a more desireable process control regime. I think annular flow would be the better option, simply due to the inherent control difficulties with slug flow, but wouldn't think that it would be any better in the long run over slug flow for erosion control purposes.
The best treatment for erosion is to either remove the offending particles, or if that is impossible, slow the velocity, but then you may get back into slug flows. Slower velocities are usually much more cost effective than increasing the hardness of materials, although I suppose you could find some specific examples to the contrary. This might be one of them. Evaluate your production rate in the annular flow regime, your maintenance cost and see if one pays for the other. Otherwise slow down and live with the wide variation in control parameters.
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