Processing of oil by steam addition
The invention relates to injecting steam into crude oil via a hydrocyclone to remove salt by transferring the salt into the condensed water from the steam. Steam transfers salt from crude oil via a different transfer mechanism and the water is separated from the crude oil leaving desalted crude oil for refining.
1. A process for removing salt from crude oil wherein the salt is in the form of particles of crystalline salt suspended in the crude oil or as droplets of brine water suspended in the crude oil, or both, wherein the process comprises the steps of:
a) injecting steam into the crude oil in the form of steam bubbles that are larger relative to any salt particles or relative to the any droplets of brine water so as to contact the steam bubbles with the crude oil along with any nearby suspended salt particles and brine droplets, such that a single steam bubble may contact salt particles and brine droplets;
b) condensing the steam bubbles into droplets of liquid water while at the same time dissolving available salt particles forming new brine water droplets and also delivering liquid or vaporous water from the steam bubbles into any available brine droplets resulting in enlarged brine droplets having a size more amenable for separation from the crude oil; and
c) separating liquid water from the crude oil including water with salt dissolved therein, wherein the process is more particularly characterized in that it does not include imposing high shear mixing of uncondensed steam bubbles in the crude oil, and wherein the step of injecting the steam occurs in a hydrocyclone steam-crude mixing zone where crude oil flows through a tangential inlet of the steam-crude mixing zone to create a vortex flow while the steam is injected into an inlet at the axis of rotation of the crude oil and stirred into the flow so that the steam bubbles are caused to collide with water droplets including brine water droplets and particles of crystalline salt along with making contact with the crude oil.
2. The process according to claim 1 wherein the steam is injected in a manner to deliver water droplets having an average diameter of at least 10 microns and up to about 150 microns after the steam bubbles have collapsed and condensed.
3. The process for removing salt from crude oil according to claim 1 further including the step of adding demulsifier into the crude oil prior to the step of separating the liquid water from the crude oil.
4. The process for removing salt from crude oil according to claim 1 wherein the steps for separating the liquid water from the crude oil includes subjecting the crude oil to low shear coalescer mixing followed by gravity separation of the water droplets from the crude oil.
5. The process for removing salt from crude oil according to claim 4 further including the step of adding demulsifier into the crude oil prior to the step of separating the liquid water from the crude oil.
6. The process for removing salt from crude oil according to claim 1 wherein steam is added to the crude oil at between 1 and 8 percent by weight steam to crude oil.
7. The process for removing salt from crude oil according to claim 1 wherein steam is added to the crude oil at between 2 and 6 percent by weight steam to crude oil.
8. The process for removing salt from crude oil according to claim 1 wherein steam is added to the crude oil at between 4 and 6 percent by weight steam to crude oil.