Cascade Control for Hydrodynamic Slugging in Fluid Pipelines
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Solution Overview
Problem
Existing control schemes for hydrodynamic slugging in fluid processing systems are impractical due to difficulties in determining setpoints for pseudo-flow control, leading to inefficient management of slugging behavior.
Innovation Solution
A cascade control scheme using a master pressure controller and a slave pseudo-flow controller, which calculates pseudo-flow rate based on differential pressure and density measurements to modulate the control valve opening, facilitating more practical control of hydrodynamic slugging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If pseudo-flow control is used to control hydrodynamic slugging, then slugging behavior can be controlled, but setpoint determination becomes difficult and requires trial and error
Solution Approach 1:
The patent introduces an intermediary relationship between pressure control and pseudo-flow control through a cascade control architecture. The pressure controller serves as a master loop that indirectly determines the pseudo-flow setpoint, eliminating the need for direct trial-and-error pseudo-flow setpoint determination. This intermediary pressure control mechanism translates difficult pseudo-flow setpoint selection into more intuitive pressure-based control.
Solution Approach 2:
The patent replaces the direct pseudo-flow control mechanism with a pressure-based control system. Instead of directly controlling pseudo-flow rate (which requires difficult setpoint determination), the system controls upstream pressure, which naturally influences pseudo-flow. This substitution transforms an operationally difficult control problem into a more manageable pressure control problem.
2Reliability
If control valve opening is reduced to control slugging, then slugging size and frequency are reduced, but production rate decreases
Solution Approach 1:
The patent implements dynamic control of the control valve through a cascade control system that continuously adjusts valve opening based on real-time pressure measurements and pseudo-flow calculations. Rather than static valve positioning, the system dynamically modulates valve opening to maintain optimal balance between slugging control and production rate, allowing the valve to respond adaptively to changing flow conditions.
Solution Approach 2:
The patent employs feedback mechanisms where upstream pressure measurements and differential pressure across the control valve are continuously monitored and fed back to the control system. This feedback enables the controller to adjust valve opening in real-time, preventing excessive valve closure that would reduce production while still effectively controlling slugging behavior through continuous adaptation to actual system conditions.
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 proposed method effectively reduces the size and frequency of hydrodynamic slugging, providing a more practical and efficient control mechanism compared to existing approaches.
Implementation Method 1
a densitometer for measuring density of the produced fluids
Implementation Method 2
a pressure sensor upstream of the control valve
Implementation Method 3
a differential pressure sensor for measuring the differential pressure across the control valve
Data Source
AI summary
A method and a control system are provided for reducing the size and/or the frequency of hydrodynamic slugging in a fluid processing system. The fluid processing system includes a pipeline for conveying produced fluids and a vessel for receiving the produced fluids from the pipeline. A control valve is provided in the pipeline upstream of the vessel. A pressure sensor is provided upstream of the control valve. Pressure information from the pressure sensor is sent to a master control loop in a cascade control scheme in which the master control loop controls a slave control loop which in turn controls the control valve. The master control loop determines a set point of the slave control loop coupled to the control valve to achieve a pressure setpoint. The slave control loop, also referred to as a pseudo-flow controller, determines whether the control valve opening needs be modulated to achieve the setpoint of the slave control loop. A method is also provided for retrofitting an existing fluid processing system.