Electrostatic treaters are used in the oil/gas industry to help facilitate oil/water separation by breaking emulsions by applying electrical charges. Electrostatic treaters are similar to horizontal heater treaters in design and operation. The main difference between the two units is the electric coalescing section in the electrostatic treater which replaces the hay section in the heater treater.
An electrical grid installed in the coalescing section with 440 volt alternating electric current produces an electrical field in the coalescing section as electric current passes through the grid. Power is supplied to the grid through a transformer mounted on the vessel and a control box mounted on a nearby pole. Almost all the electrocoalescers in the petroleum industries use AC electric fields for the separation of water-in-oil emulsions.
The operating temperature of the electrostatic treater is normally lower than that of the heater treater. In some instances the emulsion will break without heat being applied to the emulsion. The produced fluids enter the treater and any gas is vented. The liquid passes over the fire tubes and is heated if heat is applied.
Free water falls to the water section of the vessel and the emulsion rises to the coalescing section. As the emulsion passes through the electrical field the water droplets in the emulsion become electrically charged and they move about rapidly and collide with one another. As they collide the droplets grow in size forming larger droplets, until they become large enough to settle. In a water-in-oil emulsion with a high content of dispersed water, insulating the electrode may be necessary. This is because the high water content tends to produce over-stressing of the electrical coalescer due to a direct conductive path between the electrodes, which can cause the grid to short out and become non-functional.