Overview – NATCO DUAL POLARITY Electrostatic treater
More efficient dehydration and desalting at lower operating temperatures
The NATCO DUAL POLARITY electrostatic treater outperforms both mechanical and AC electrostatic treaters in upstream crude oil dehydration and desalting applications and as a first-step desalter in refining operations.
Using both AC and DC fields from a power unit that has become the benchmark for reliability in the industry, the NATCO DUAL POLARITY treater more efficiently coalesces water droplets, enabling it to run at higher throughputs than conventional electrostatic treaters. Other internal components, such as composite electrodes that resist solids loading and a high-flow distributor that improves vessel hydraulics, also support increased throughput while reducing maintenance and opex.
NATCO LRC-II smart interface, an optional load-responsive controller, enhances emulsion resolution via voltage modulation. This enables you to operate at the optimal voltage for a variety of crude feedstocks while managing upsets more rapidly and effectively.
The NATCO DUAL POLARITY treater handles a wider range of inlet water cut and provides higher treating capacities at lower operating temperatures, reducing capex and opex. The treater requires less washwater than an AC desalter because of improved mixing from electrophoretic movement of the water droplets in the electrostatic field. The treater can be delivered as a heater treater, providing heating and dehydration in a single vessel and eliminating the need for externally heated heat transfer fluid.
Using AC and DC fields for more effective removal of formation water from crude oil
The NATCO DUAL POLARITY treater uses the extremely efficient HiFlo spreader to evenly distribute the incoming wet crude and create a uniform vertical flow upward through the treater. This method eliminates grid bypass and local recirculation areas.
The bulk water and larger water drops are coalesced and separated by gravity in the weaker AC field that exists between the grounded water phase and the electrodes. The stronger DC field between the electrodes causes rapid movement of the remaining small water droplets through electrophoretic attraction, causing the water droplets to collide, coalesce, and settle by gravity.
In desalter applications, washwater is added upstream of the mixing valve in the treater’s inlet piping. Together with the electrophoretic movement of the water droplets, this provides a very high degree of mixing with the brine. Superior mixing and improved dehydration make the NATCO DUAL POLARITY treater much more effective than AC desalters of similar size.
Application of NATCO DUAL POLARITY Electrostatic treater
The treater’s dual-polarity design enables it to split the voltage with rectifiers into positive and negative components. Pairs of vertical electrodes are charged in opposition. The oil-water emulsion from the distributor enters the DC field between electrodes, and the water droplets will accept the polarity of the closest electrode. Once the emulsified water droplets approach an electrode plate, they accept the charge of that plate. The water droplets are moved by electrophoretic force toward the electrode of opposite polarity, causing head-on collisions and coalescence. When the droplets are large enough, gravity will overcome the DC field, and the droplets will separate by gravity into the water phase.