Processing of oil by steam addition
The invention relates to injecting steam into crude oil in two separate desalting steps to remove salt by transferring the salt into the condensed water from the steam and gravity separating the water from the crude oil. Steam transfers salt from crude oil via a different transfer mechanism and therefore doesn't require the high shear mixing of conventional water injection systems. In the invention, salt is also removed via a first step of adding water with harsh mixing of the added water with the crude oil.
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 liquid water into the crude oil;
b) imposing 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 high shear mixing, injecting a first stream of steam into the crude oil in the form of steam bubbles that are larger 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 contact with the crude oil along with any nearby suspended salt particles and other droplets, such that a single steam bubble may contact a plurality 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 creating 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;
e) separating liquid water from the crude oil including water with salt dissolved therein to form a first pass desalted crude oil;
f) injecting a second stream of steam into the first pass desalted crude oil in the form of steam bubbles that are larger relative to any remaining salt particles or relative to any remaining brine droplets so as to create steam bubbles that will have contact with the first pass desalted crude oil along with any nearby suspended salt particles and other droplets, such that a single steam bubble may contact a plurality of salt particles and water droplets;
g) condensing the steam bubbles into droplets of liquid water while at the same time dissolving available salt particles forming new brine droplets and also delivering liquid or vaporous water from the steam bubbles into any available water droplets and any remaining available brine droplets resulting in enlarged water and brine droplets having a size more amenable for separation from the first pass desalted crude oil; and
h) separating and removing liquid water from the first pass desalted crude oil where the water includes the salt dissolved therein that was previously suspended in the crude oil, 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 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.
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 first 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 steps 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 steps 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 steps 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.