Fact Sheet - Thermal Distillation
This fact sheet describes thermal distillation, a process that has been used for decades to desalinate seawater for drinking water. Historically, thermal distillation has not been cost-effective for treating produced water. A new version of thermal distillation has recently been introduced for treating produced water. The AltelaRain technology is based on internal heat transfers that reuse the latent heat of condensation. Since the technology recaptures the energy previously used to evaporate water, energy costs fall to approximately 25% of comparable distillation/evaporation processes (Godshall 2006, Bruff 2006).
The system recirculates a carrier gas, which has the ability to absorb and desorb pure water from the produced water several times over, resulting in extremely high energy efficiencies. Ambient-temperature air is brought into the bottom of the tower on the evaporation side of a heat transfer wall. After entering the evaporation side at the top of the tower, the produced water spreads over and coats the heat transfer wall in a thin film. As the air moves from the bottom to the top of the tower, low-temperature heat is transferred into the evaporation side through the heat transfer wall. This raises air temperatures and evaporates water from the brine coating the wall.
Water, now highly concentrated in contaminants, leaves from the bottom of the tower, while warm saturated air rises to the top of the tower. Steam is added to further heat the warm air. This hotter saturated air is then sent back down through the tower on the condensation side of the heat transfer wall. Since the evaporation side of the tower is slightly cooler than the condensation side, the air cools and transfers the latent heat from the condensation to the evaporation side. Meanwhile, pure distilled water condensate leaves the condensation side of the tower at the bottom of the tower.
Individual AltelaRain units are capable of processing produced water at a rate of about 8 barrels per day.
The technology is modular. Multiple units, run in parallel, are able to process larger volumes.
As of late 2006, the AltelaRain process has been pilot-tested in New Mexico. The water quality test results show significant removals of produced water contaminants. Total dissolved solids were reduced from 41,700 mg/L to 106 mg/L; chlorides from 25,300 mg/L to 59 mg/L; and metals and organic chemicals to non- or barely detectable (Godshall 2006, Bruff 2006).
References
Bruff, M.J., 2006, "An Exciting New Produced Water Concentrator Technology for Tail and Brine Waters: AltelaRainTM," presented at the 13th International Petroleum Environmental Conference, San Antonio, TX, Oct. 17-20. Available at http://ipec.utulsa.edu/Conf2006/Papers/Bruff_25.pdf.
Godshall, N.A., 2006, "AltelaRainTM - State of the Art Produced Water Treatment Technology," presented at the 13th International Petroleum Environmental Conference, San Antonio, TX, Oct. 17-20. Available at http://ipec.utulsa.edu/Conf2006/Papers/Godshall_129.pdf.
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