Electrostatic Separator for Subsea Oil Dehydration
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Solution Overview
Problem
Conventional oil-and-water separators are limited in capacity and effectiveness for treating high volumes of mixed oil-and-water streams, leading to inefficiencies in separating water from crude oil, as they struggle with high rag volumes and solids carryover, especially when handling slugs of water.
Innovation Solution
An electrostatic separation vessel with staggered high-voltage tubes and electrodes within the oil collection portion, subjected to an electrostatic field, allowing water droplets to coalesce and separate from oil, with the water flowing downward and oil upward, optimizing the separation process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional separators are used for low velocity feed streams, then separation effectiveness is maintained, but productivity is limited due to low treatment capacity
Solution Approach 1:
The patent replaces conventional mechanical gravity-based separation with an electrostatic field-based separation system. High voltage electrodes create electric fields that induce dipole moments in water droplets, causing them to coalesce and separate from oil. This substitution enables high velocity feed streams to be effectively separated, dramatically increasing productivity while maintaining separation effectiveness through electrostatic forces rather than relying solely on gravitational settling.
Solution Approach 2:
The patent changes the physical parameter of the separation process by applying high voltage electric fields (typically 10-100 kV) to the oil-water mixture. This parameter change creates strong electrostatic forces that accelerate water droplet coalescence and separation, allowing the system to handle high velocity feed streams that would otherwise pass through conventional separators too quickly for effective separation, thus resolving the contradiction between productivity and reliability.
2Productivity
If conventional separators treat high volumes of mixed streams, then productivity increases, but manufacturing precision deteriorates due to increased solids carryover and rag volume
Solution Approach 1:
The electrostatic separation system replaces mechanical gravity separation with electric field-based coalescence. The high voltage electrodes create electric fields that specifically target and coalesce water droplets based on their polar nature, while leaving oil and suspended solids unaffected. This selective action maintains high separation quality even at high throughput volumes, preventing solids carryover and minimizing rag volume that plagues conventional high-capacity separators.
Solution Approach 2:
The electrostatic field acts as an intermediary mechanism that selectively interacts with water droplets in the oil-water mixture. The electric field induces dipole moments in the polar water molecules, causing them to align and coalesce without affecting non-polar oil or suspended solids. This intermediary action enables high-volume treatment while maintaining high separation precision, as the electric field selectively targets only the water component for coalescence and separation.
3Adaptability or versatility
If conventional separators handle slugs of water, then adaptability is improved, but reliability deteriorates due to upset conditions affecting performance
Solution Approach 1:
The electrostatic separation system replaces gravity-based mechanical separation with electric field-based coalescence. The high voltage electrodes create electric fields that immediately coalesce water droplets upon entry, regardless of their size or distribution pattern. This mechanism is inherently insensitive to slug flow conditions, as the electric field acts on individual droplets rather than requiring a stable liquid interface. Consequently, the system maintains reliable performance even when handling slugs of water, eliminating the upset conditions that affect conventional separators.
4Volume of moving object
If separation vessel size is reduced to minimize space, then device complexity is reduced, but productivity decreases due to limited treatment capacity
Solution Approach 1:
The electrostatic separation system replaces large-volume gravity-based separation chambers with compact high voltage electrode assemblies. The electric field-based coalescence mechanism is highly efficient and requires minimal residence time, allowing the separation vessel to be dramatically reduced in size while maintaining or even increasing treatment capacity. The high voltage electrodes create intense electric fields that rapidly coalesce water droplets, enabling high productivity in a compact footprint.
Solution Approach 2:
The patent changes the physical parameter of applying high voltage electric fields (10-100 kV) within a compact vessel configuration. This parameter change creates extremely rapid coalescence kinetics that reduce the required residence time and vessel volume by orders of magnitude compared to conventional gravity separators. The intense electrostatic forces enable high treatment capacity to be achieved in a minimized vessel size, resolving the contradiction between compactness and 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
This solution enhances the separation efficiency, minimizes rag volume, improves the quality of both water and dehydrated oil streams, and reduces space requirements, effectively handling higher volumes and varying flow conditions.
Implementation Method 1
subjecting the mixture to an electric field. Oil, being a non-polar fluid, acts as a dielectric and water droplets, being polar, when subjected to an electric field are coalesced
Implementation Method 2
water droplets become polarized by the electric field. Polarized droplets are attracted to each other and move into and coalesce with each other
Implementation Method 3
Polarized droplets are attracted to each other and move into and coalesce with each other. Larger droplets tend to gravitate downwardly within the mixture
Implementation Method 4
Larger droplets tend to gravitate downwardly within the mixture and the oil, having portions of the water removed therefrom, tends to gravitate upwardly within the mixture
Data Source
AI summary
An apparatus and method for separating water from an oil-water influx are provided. The apparatus includes a separation vessel having an inlet, an oil collection portion at its upper end, and a water collection portion at its lower end. Multiple high voltage tubes, each containing an electrode, are located within the oil collection portion. These high voltage tubes are staggered in length and held in place by perforated plates. The oil-water influx flows through the inlet of the vessel into the high voltage tubes, where it is subjected to an electrostatic field. The electrostatic field causes water droplets in the influx to coalesce and form a water out-flux which flows downwardly into the water collection portion of the vessel. The remaining stream of dehydrated oil flows upwardly to the upper outlet end. The oil collection portion of the separation vessel may be oriented vertically or at an angle.