Brine dispersal system
A desalination brine dispersal apparatus and method employ airlift to remove, oxygenate and disperse brine from a desalination apparatus. The apparatus includes a brine removal conduit having a brine inlet that receives brine from the desalination apparatus, a plurality of brine outlets submerged in seawater and one or more air introduction points located at depths below the brine outlets. The supplied air oxygenates and moves brine through the brine removal conduit and outlets via airlift and disperses the brine into seawater away from the brine removal conduit. The apparatus avoids the formation of concentrated, high shear brine plumes and can disperse brine into seawater over a wide area well away from the brine removal conduit.
1. A wide-area desalination brine dispersal system comprising a brine removal conduit having:
b) a brine inlet that receives brine from a desalination apparatus;
c) a plurality of brine outlets submerged in seawater; and
d) one or more air introduction points located at depths below the brine outlets, for oxygenating and moving brine through the brine removal conduit and outlets via airlift and dispersing the brine into seawater away from the brine removal conduit,
wherein the brine removal conduit has a first air introduction point, a first brine outlet from which brine leaves the conduit, a first length between such first air introduction point and first brine outlet, and the air lifts brine as averaged over such first length using an air fraction of at least 5% and up to 95%.
2. A system according to claim 1 wherein the desalination apparatus is an onshore apparatus.
3. A system according to claim 1 wherein the desalination apparatus is an offshore platform-mounted or ship-borne apparatus.
4. A system according to claim 1 wherein the desalination apparatus is a distillation or evaporation apparatus.
5. A system according to claim 1 wherein the desalination apparatus is a reverse osmosis apparatus.
6. A system according to claim 5 wherein the desalination apparatus employs reverse osmosis membranes, and when carrying out continuous desalination and continuous brine airlift, operation of the brine airlift reduces salinity buildup at the reverse osmosis membranes and increases the flow rate or output of product water from such membranes.
7. A system according to claim 6 wherein the desalination apparatus is submerged.
8. A system according to claim 7 wherein the membranes are not encased in a surrounding pressure-resistant housing.
9. A system according to claim 7 wherein the desalination apparatus is deployed at a depth that enables hydrostatic pressure to drive seawater through the membranes.
10. A system according to claim 1 wherein the system does not include submerged frictional sliding surfaces, a submerged mechanical pump or a submerged valve.
11. A system according to claim 1 wherein the air lift is provided by an onshore, ship-borne, submerged or surface platform-mounted compressor unit.
12. A system according to claim 1 wherein the air lift is provided by a compressor unit powered at least in part by energy derived from waves, wind or sunlight.
13. A system according to claim 1 wherein the air lifts the brine in a slug or churn flow regime.
14. A system according to claim 1 wherein the air fraction is less than 60%.
15. A system according to claim 1 wherein the brine removal conduit has a first length between such first air introduction point and first brine outlet of at least 1 meter, and a second length between such first brine outlet and the distal end of the brine removal conduit of at least 5 meters.
16. A system according to claim 15 wherein the second length is at least 50 meters.
17. A system according to claim 15 wherein the second length includes openings that allow diluting seawater to be drawn into flowing brine within the brine removal conduit, and the brine outlets extend along at least 30% of the second length.
18. A system according to claim 1 wherein the system provides increased oxygenation of nearby seawater and a consequent reduction in hypoxia or dead zones in nearby seawater.