Subsea Multiphase Pump Recirculation via GLCC Separator
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Solution Overview
Problem
Subsea twin-screw multiphase pumps face challenges in maintaining continuous liquid flow due to gas slugs and low liquid content, leading to pump shutdowns, efficiency losses, and potential damage from overheating, particularly in subsea applications where recirculation systems are inefficient and impractical.
Innovation Solution
A subsea multiphase pumping system incorporating a Gas Liquid Cylindrical Cyclone (GLCC) with a recirculation arrangement and a liquid slug distributor, which separates and recirculates liquid to maintain a minimum flow threshold, using a baffle plate to prevent gas and particulate entrainment, and a choke valve to regulate pressure, combined with a liquid slug distributor to manage unsteady flow patterns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If recirculation is used to ensure continuous liquid flow, then pump reliability is improved, but pump efficiency deteriorates due to reduced capacity and increased energy consumption
Solution Approach 1:
A Gas Liquid Cylindrical Cyclone (GLCC) separator is introduced as an intermediary device between the pump discharge and suction. The GLCC separates gas and liquid phases, allowing liquid to be recirculated while gas is vented, thereby maintaining continuous liquid flow to the pump without requiring recirculation of the entire multiphase mixture, thus improving reliability while minimizing energy consumption and capacity loss.
2Reliability
If recirculation is used to maintain liquid flow, then pump reliability is improved, but device complexity increases
Solution Approach 1:
The GLCC separator performs multiple functions: it separates gas and liquid phases, provides liquid storage volume, and enables passive recirculation of liquid to the pump suction. This multi-functionality achieves reliable continuous liquid flow while avoiding the need for additional complex recirculation piping, valves, and control systems that would otherwise be required.
3Productivity
If pump operates without sufficient liquid, then productivity is maintained, but pump temperature increases causing potential damage
Solution Approach 1:
The GLCC separator is positioned to receive liquid from the pump discharge before the liquid can be heated by gas compression in the pump. By separating and recirculating liquid in advance, the system ensures cool liquid is continuously supplied to the pump, preventing temperature buildup and potential damage while maintaining productivity.
4Reliability
If liquid recirculation is implemented, then pump reliability is improved, but volumetric efficiency decreases
Solution Approach 1:
The GLCC separator extracts only the liquid phase from the multiphase mixture for recirculation, while allowing the gas phase to be vented or processed separately. This selective extraction ensures that recirculation is limited to the minimum liquid volume required to maintain pump reliability, thereby minimizing the impact on volumetric efficiency and overall productivity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system ensures continuous operation by maintaining a minimum liquid flow, reducing energy consumption, and preventing overheating, while optimizing pump efficiency and reliability in subsea environments by effectively handling varying flow profiles and gas-liquid ratios.
Implementation Method 1
Separation of the multiphase fluid occurs due to centrifugal, gravitational and buoyancy forces
Implementation Method 2
Separation of the multiphase fluid occurs due to centrifugal, gravitational and buoyancy forces
Implementation Method 3
Separation of the multiphase fluid occurs due to centrifugal, gravitational and buoyancy forces
Implementation Method 4
a choke valve to regulate pressure
Data Source
Figure 1
Figure 2
Figure 3A~3C
AI summary
In subsea multiphase pumping systems, the use of a gas -liquid cylindrical cyclone (GLCC) as a separator to recirculate liquid from pump discharge to pump suction, especially during high gas inlet conditions from a multiphase petroleum stream. Further contemplated is protection of the pump from momentary high gas inlet conditions due to an incoming slug flow profile from a petroleum stream, via transforming a naturally varying multiphase petroleum stream into separated phases for measured distribution to the pump suction and ensuring a minimum liquid flow.