Vessel Internal Electrostatic Coalescer (VIEC™)

Vessel Internal Electrostatic Coalescer (VIEC™), is a technology for enhancing liquid-liquid separation by using alternating high voltage electrical fields.

Information

The modular construction consists of several electrodes, where each electrode is electrically insulated and has its own dedicated transformer for transforming a low voltage feed to high voltage.

It tolerates 100% water and 100% gas without short circuiting or arcing, making it ideally suited for use in any three-phase separator to speed up the separation of water dispersed in oil and/or to resolve stable oil-continuous emulsions.

The VIEC can be installed in new separators or retrofitted into existing three-phase separators with no hot work required.
Pairs of energized electrodes are supplied by a low voltage feed from dedicated external VIEC frequency cards, giving excellent reliability and robustness.


Techincal data

The VIEC system consists of the following building blocks:

1.  VIEC elements comprising an energized electrode with an inbuilt transformer in a single fully insulated unit 
2. VIEC cable conduit providing low voltage power distribution through a conduit system inside the separator
3. VIEC cassettes supporting the elements and providing earthed electrodes on either side of each energized electrode 
4.  VIEC steel structure for supporting the VIEC cassettes with VIEC elements 
5.  VIEC penetrator (ATEX/UL) consisting of a pressure barrier and junction box to enable low voltage power feed into the vessel shell 
6.  VIEC frequency converters to provide low voltage power to the individual VIEC elements             
7.  VIEC converter cabinet for control and communication with the VIEC frequency converters

The VIEC cassettes are stacked side by side to form a regular matrix of electrodes covering the oil-continuous layer inside the separator, which is normally from the normal interface level to the normal liquid level. One or more walls of elements can be installed, depending on the process conditions and requirements.


Applications

The VIEC technology offers a wide range of applications for optimizing and/or de-bottlenecking oil separation trains, depending on the process scenarios and client requirements. Typical applications include the following:

  • Tie-ins/capacity increase: The enhanced separation effect offered by the VIEC reduces the required retention time in the separator to achieve specification. Thus, by retrofitting the VIEC into existing production separators, the throughput can be significantly increased without compromising oil quality
  • Heavy oil: Conventional processes for heavy crudes require higher temperatures than medium and light crudes due to higher viscosity. With VIEC, heavy crudes can be separated at significantly higher viscosities since the positive effect of enhanced droplet growth outweighs the negative effect of high viscosity. This allows for a significant reduction in process temperatures. The benefits can be substantial energy savings and a reduction in the operational complexity of the process
  • Desalting: Conventional desalting is performed using conventional two-phase electrocoalescers in the final stage, after all the gas has been removed and the water content reduced sufficiently. Using VIEC technology, desalting can start earlier in the process train at higher water cuts with gas present. By achieving low water contents in the oil stream early in the process, the number of required desalters downstream could be reduced in process schemes where a conventional approach calls for two or more desalters. Additionally, the required injection rate of wash water could be reduced significantly
  • Light oil: For light oils, the VIEC can contribute to a more compact process with savings in both process equipment, weight and space. Due to lower viscosities, export quality can be achieved with less electrostatic treatment time than for heavier crudes. Since VIEC technology can be applied in any three-phase separator where there is gas present and high water contents, final separation of the crude can be performed further upstream with VIEC technology than in a conventional process. This could potentially remove the need for a conventional dehydrator downstream, providing a more compact separation scheme
  • Pre-treatment skid: VIEC technology can be used in pre-treatment skids upstream of existing process facilities to ensure that the existing facilities are not overloaded as the rate of produced water and/or crude increases. This allows for a minimally invasive intervention that minimizes the interruption to the existing facilities, while at the same time increasing its capacity for processing crude
  • Emulsion breaking/de-bottlenecking: The presence of, for example, surfactants, a high viscosity or the mixing of incompatible well streams could lead to stable emulsions that severely limit the capacity of separators. Electrocoalesence is a well proven principle for breaking stable emulsions. Thus, by installing VIEC technology at the appropriate stage in the separation train, troublesome emulsion can be resolved, which ensures the optimal operation and performance of the separation facilities

Key benefits

The enhanced separation efficiency provided by VIEC electrostatic coalescence can offer several benefits with respect to both CAPEX and OPEX. These include one or several of the following:

  • CAPEX savings
    • Reduced size of separator
    • Less number of separation stages
    • Separation at lower temperatures for heavy crudes. Higher temperatures require more expensive separation and utility equipment
  • OPEX savings
    • Reduced costs for fluid heating
    • Increased production/de-bottle necking
    • Reduce demulsifier consumption
    • Reduced fresh water requirement for desalting
  • Additional operational benefits include
    • Improved level of control
    • Reduced water content at earlier stages
    • Provides stable and predictable inlet conditions for process equipment downstream
    • Improved robustness of the separation process

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Applications