Processing of oil by steam addition
The invention relates to injecting steam into crude oil for several benefits, primarily of which is to remove salt by transferring the salt into the condensed water from the steam. Steam transfers salt via a different transfer mechanism and therefore doesn't require the high shear mixing of conventional water injection systems. As such, steam injection through a variety of procedures, is more efficient at gathering salt into water that itself is easier to remove from the crude oil.
1. A process for removing salt from crude oil wherein the salt may be in the form of particles of crystalline salt suspended in the crude oil or as small droplets of brine water suspended in the crude oil, or both, wherein the process comprises the steps of:
a) injecting liquid water into the crude oil;
b) imposing aggressive high shear mixing on the crude oil and water in a high shear mixer to break up the injected water into smaller droplets of water and, at the same time, enhance contact of the smaller droplets of water with salt particles and brine droplets to enhance dissolving of salt particles and also coalesce droplets of water whether brine droplets or droplets of injected water;
c) after the aggressive high shear mixing, injecting steam into the crude oil in the form of steam bubbles that are quite large relative to any salt particles or relative to any brine droplets and also relative to water droplets so as to create steam bubbles that will have substantial contact with the crude oil along with any nearby suspended salt particles and other droplets, such that a single steam bubble may actually contact a number of salt particles and water droplets;
d) 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 water and brine droplets resulting in enlarged water and brine droplets having a size more amenable for separation from the crude oil; and
e) separating liquid water from the crude oil where the water includes the salt dissolved therein, wherein the process is more particularly characterized in that it does not include imposing high shear mixing of uncondensed steam bubbles within the crude oil.
2. The process for removing salt from crude oil according to claim 1 wherein the step 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.
3. The process for removing salt from crude oil according to claim 2 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 3 wherein the step of injecting steam further includes injecting the steam into a vertically oriented chamber where the crude oil and steam flow vertically as the steam bubbles condense.
5. The process for removing salt from crude oil according to claim 4 wherein the vertical flow in the chamber is downward.
6. The process for removing salt from crude oil according to claim 4 wherein the vertical flow in the chamber is upward.
7. The process for removing salt from crude oil according to claim 2 wherein the step of injecting steam further includes injecting the steam into a vertically oriented chamber where the crude oil and steam flow vertically as the steam bubbles condense.
8. The process for removing salt from crude oil according to claim 7 wherein the vertical flow in the chamber is downward.
9. The process for removing salt from crude oil according to claim 7 wherein the vertical flow in the chamber is upward.
10. The process for removing salt from crude oil according to claim 1 wherein the step of injecting steam further includes injecting the steam into a vertically oriented chamber where the crude oil and steam flow vertically as the steam bubbles condense.
11. The process for removing salt from crude oil according to claim 10 wherein the vertical flow in the chamber is downward.
12. The process for removing salt from crude oil according to claim 10 wherein the vertical flow in the chamber is upward.
13. 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 first step of separating the liquid water from the crude oil.