Drawdown Pipe Separation Vessel for LPG Recovery
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Solution Overview
Problem
Current methods for de-inventorying LPG or HVL pipelines, such as dual phase flare stacks and multi-phase cross-compression units, result in significant product loss and prolonged downtime, with flaring methods wasting most of the product and cross-compression methods being inefficient for longer pipelines.
Innovation Solution
Incorporating a separation vessel between the drawdown section and flare, equipped with liquid pumps and a flow control valve, to separate and pump out the liquid phase while controlling gas flow, thereby maximizing product recovery and reducing combustion emissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If dual phase flare stack is used to burn evacuated fluids, then the pipeline draw-down operation can be completed, but most of the product is treated as waste and combustion emissions increase
Solution Approach 1:
The patent segments the draw-down process into two distinct phases: (1) liquid recovery phase where liquid product is separated and pumped to recovery vessels, and (2) vapor flaring phase where only remaining vapors are burned. This segmentation allows selective recovery of valuable liquid product while minimizing flaring, directly resolving the contradiction between operational completion and product loss.
Solution Approach 2:
The invention extracts the liquid phase from the mixed vapor-liquid flow using a separation vessel, removing it from the flaring process entirely. By taking out the liquid product before combustion, the system recovers valuable material that would otherwise be lost to the flare, addressing the product loss issue while maintaining operational effectiveness.
2Loss of substance
If multi-phase cross-compression unit is used to pump product into adjacent section, then most product can be recovered, but time required increases significantly for pipelines above 5000 ft
Solution Approach 1:
The patent introduces a spatial dimension to the problem by using elevation changes and gravity-assisted flow in the separation vessel. Liquid product separates and accumulates at the bottom due to gravity, allowing continuous pumping without requiring the extended time needed for compression-based methods to move equivalent volumes through pressure differentials alone.
Solution Approach 2:
The invention employs hydraulic principles by using gravity-driven liquid separation and pumping rather than pneumatic compression. The liquid phase is pumped directly from the separation vessel to recovery vessels, eliminating the need for prolonged compression cycles required by multi-phase compressors, thus reducing draw-down time while maintaining high recovery rates.
3Loss of substance
If cross-compression unit operates on longer pipeline sections, then product can be recovered, but the process becomes cost prohibitive due to extended downtime
Solution Approach 1:
The patent segments the pipeline into a drawdown section and recovery section separated by a valve, allowing independent operation. The separation vessel with liquid pumping capability enables rapid liquid removal from the drawdown section, significantly reducing the time the pipeline remains out of service and lowering operational costs for long pipeline sections.
Solution Approach 2:
The separation vessel acts as an intermediary device between the drawdown section and recovery vessels. It enables efficient liquid-vapor separation and continuous liquid pumping, facilitating rapid product recovery without the extended compression cycles that make long pipeline draw-down operations cost prohibitive.
4Ease of operation
If flare receives multi-phase fluid with high vapor content, then vapor can be discharged, but liquid flow slows causing wave action and repeated slugging
Solution Approach 1:
The patent extracts the liquid phase from the multi-phase flow before it enters the flare system. The separation vessel removes liquid product, which is then pumped to recovery vessels, leaving primarily vapor to be discharged through the flare. This extraction eliminates the liquid-vapor interaction that causes slugging and wave action, simplifying flare operation.
Solution Approach 2:
The separation vessel serves as an intermediary between the drawdown section and the flare, filtering out the liquid phase that would otherwise cause slugging problems. This intermediary device allows the flare to receive mostly vapor, eliminating the complex liquid-vapor flow dynamics and associated control issues.
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
This approach achieves higher product recovery (40-80%) within the same time frame as traditional flaring, minimizing atmospheric emissions and operational downtime, thus improving both financial and environmental aspects of the drawdown process.
Implementation Method 1
a separation vessel between the drawdown section and flare, equipped with liquid pumps and a flow control valve, to separate and pump out the liquid phase while controlling gas flow
Implementation Method 2
equipped with liquid pumps and a flow control valve, to separate and pump out the liquid phase
Implementation Method 3
equipped with liquid pumps and a flow control valve, to separate and pump out the liquid phase while controlling gas flow
Implementation Method 4
dual phase flare stack designed to burn the evacuated fluids
Data Source
AI summary
A method to drawdown pipe sections with the use or regulation control of flaring and cross-compression technique. The method allows to evacuate a fluid mixture from a drawdown section. The fluid mixture typically contains a liquid phase and a gas phase. The method includes flowing the fluid mixture from the drawdown section towards a separation vessel, and then out of the separation vessel to simultaneously flow the gas phase towards a flare for burning and flow the liquid phase towards one or more pumps towards an adjoining section. The proposed method allows recovering a higher proportion of the fluid mixture, as recycled product, and therefore limiting the combustion of the gas phase towards the atmosphere.