SPS Systems designs and manufactures two types of oil desalination units.
- Multi-effect evaporators (MEE) for seawater or brines
- Reverse osmosis (RO) units for seawater desalination
Multi-effect evaporators are used to concentrate and reduce the volume of waste water produced in the oil field by converting it to distilled water through a series of stages or “effects.” 75% of oilfield brine volume can be distilled to potable water depending on TDS concentration. Waste heat from engines, gas turbine exhaust, or other sources is usually used in place of expensive energy sources. Mult-effect can be used in parallel with gas turbine driven pump power in a large reverse osmosis unit where the turbine exhaust would drive the multi-effect evaporator.
Reverse osmosis is typically used for seawater desalination and for predictable process separations such as cooling tower make-up and food process separations. Overcoming the osmotic pressure and hydraulic resistance can require pressure from 700-900 psig. For seawater desalination typically a 30-40% permeate (potable water) recovery is possible. The pump Bhp is significant and some power recovery can be achieved with power recovery turbine. The RO membranes are very susceptible to fouling and multi-media filters and ultra-filtration is usually required. Periodic membrane flushing is necessary. RO is not recommended to treat water produced from oil fields.
Multi-effect evaporation is cost-effective, using four to six effects when waste heat is available. Brackish water is more treatable with MEE than RO because of unpredictable total dissolved solids (TDS) composition and concentration. However, MEE is more expensive than RO for conventional seawater desalination.
SPS Systems designs the necessary feed water intake, pretreatment filter, Multi-effect or reverse osmosis evaporator and concentrate disposal systems.