Crude oil desalting by counterflow electrostatic mixing

Chlorides in crude oil which are normally contained in finely dispersed connate brine are detrimental to refinery processes from both corrosion enhancement and catalyst degradation considerations. These have been removed historically by mechanically mixing the crude oil with fresh water and separating the phases with the aid of heat, chemicals, and electric fields. A new process has been developed which produces both mixing and coalescence by an electrostatic field allowing multiple contact stages to be realized with countercurrent flow in a single vessel. The improvement in separation is similar to that of a multi-tray distillation column as compared to a single stage flash drum. Because the energy of the electrostatic field is expended primarily on the transport of the polar phase (water), mixing efficiency is much greater that can be obtained with conventional means using differential pressure across an adjustable orifice. A controlled and varying DC field is employed in the process and is adjusted to achieve both effective mixing and maximum coalescence. This results in a much drier oil than is obtained by conventional means. A refinery installation of the system is now under evaluation. Although only limited information can be made public at this time regarding this system,more » some of the concerns which have surfaced and their resolution will be discussed.« less