Method and apparatus for treatment of fluids
A method of fluid treatment of a feed comprising oil and water, the method comprising: supplying the feed into a flotation cell, the feed having an oil concentration, the flotation cell containing a working fluid and the working fluid having a surface; removing an oil phase from the surface of the working fluid; removing fluid from the flotation cell through one or more outlets below a working fluid level in the flotation cell; and controlling flow through the one or more outlets to maintain the working fluid level in the flotation cell within a predetermined range independent of variations in the oil concentration of the feed. A related apparatus is also disclosed.
1. A method of fluid treatment of a feed comprising oil and water, the method comprising:
supplying the feed into a flotation cell at a flow rate under control of a controller, the feed having an oil concentration, the flotation cell containing a working fluid and the working fluid having a working fluid level forming a surface of the working fluid;
removing an oil phase from the surface of the working fluid;
removing the working fluid from the flotation cell by flow through one or more outlets below the working fluid level in the flotation cell;
sensing the working fluid level; and
in response to the sensed working fluid level, using the controller, controlling flow through the one or more outlets and the flow rate of the feed to maintain the working fluid level in the flotation cell within a predetermined range independent of variations in the oil concentration of the feed by applying a priority to the flow rate of the feed into the flotation cell so that the flow rate of the feed is adjusted only if the flow through the one or more outlets is outside of an operating range.
2. The method of claim 1 in which the feed is supplied from a phase separator that uses energy from fluid passing through a restriction to effect a phase separation.
3. The method of claim 1 in which the feed comprises a foam mixture of oil, water and gas.
4. The method of claim 1 , further comprising monitoring the working fluid level in the flotation cell by sensing a pressure of the working fluid in the flotation cell.
5. The method of claim 4 in which the pressure is sensed at a base of the flotation cell.
6. The method of claim 1 in which the oil phase is removed from the flotation cell over a weir.
7. The method of claim 1 in which at least an outlet of the one or more outlets is from a base of the flotation cell.
8. The method of claim 1 in which the feed is supplied into the flotation cell at the surface of the working fluid.
9. The method of claim 8 in which the feed is at least partially spread across the surface of the working fluid.
10. The method of claim 1 , further comprising:
supplying fluid removed from the flotation cell into a second flotation cell, the second flotation cell containing a second working fluid and the second working fluid having a surface;
removing a second oil phase from the surface of the second working fluid;
removing fluid from the second flotation cell through one or more outlets below a working fluid level in the second flotation cell; and
controlling flow through the one or more outlets in the second flotation cell to maintain the working fluid level in the second flotation cell within a predetermined range independent of variations in the oil concentration of the fluid supplied to the second flotation cell.
11. The method of claim 10 in which fluid removed from the flotation cell is supplied into the second flotation cell through a phase separator, which uses energy from fluid passing through a restriction to effect a phase separation.
12. The method of claim 11 in which the phase separator agitates the fluid removed from the flotation cell in the presence of a gas to cause the fluid to foam.
13. The method of claim 10 in which the oil phase removed from the second flotation cell is removed over a weir.