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. Several companies offer different versions of thermal distillation – these are described below. Most of them produce very clean water as a byproduct, while others evaporate the water through a crystallization step.
Thermal treatment entered the produced water treatment market by looking at niche opportunities, particularly in remote locations without well-developed infrastructure. Other forms of traditional produced water management tended to be more expensive in those applications, allowing the energy-intensive thermal processes an opportunity to be cost-effective. With the proliferation of shale gas wells in the past decade, the demand for treating frac flowback water with high total dissolved solids (TDS) has expanded the opportunities for thermal systems. Thermal processes appear to be the only practical option for treating flowback and produced water with TDS levels above 40,000 mg/L.
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 (Bruff 2010, Veil 2008).
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.
Single AltelaRain unit; source: Altela.
Multiple AltelaRain units are deployed at a well site inside of large shipping containers; source: Altela.
Water 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.
In recent test results, the system treated flowback water with 40,530 mg/L of TDS and produced water with 195,130 mg/L of TDS to clean water with less than 100 mg/L of TDS (Bruff 2010).
Halldorson (2010) describes the Aqua-Pure system. The individual units are called NOMADs; they are operated by a U.S. subsidiary, Fountain Quail Water Management. They utilize a mechanical vapor recompression process to evaporate water. Veil (2008) describes a site visit to the Barnett Shale region in Texas where he observed several Aqua-Pure thermal distillation units treating flowback water for reuse.
Aqua-Pure NOMAD unit in Texas.
In 2009, several Aqua-Pure units were licensed by Eureka Resources, a commercial wastewater treatment facility in northern Pennsylvania, to provide a high degree of TDS removal when needed.
In the NOMAD system, the incoming produced water is heated, prior to passing through a deaerator. Following heat exchange, a mixture of steam and boiling concentrate flows into the separator where steam is separated from the boiling concentrate. The steam enters a compressor, which boosts the pressure and temperature of the steam. The high temperature, high pressure steam condenses into distilled water.
212 Resources also uses a mechanical vapor recompression system combined with high velocity turbulent flow heat exchange technology. They utilize flash evaporation and submerged boiling. Their units have treated flowback water from Wyoming with TDS of 15,000 to 25,000 mg/L and flowback water from Texas with TDS of 70,000 to 100,000 mg/L to a very clean level of <250 mg/L (Dees 2010). The units are portable and skid mounted.
Intevras Evras System
In the Barnett Shale, Chesapeake Energy is running pilot tests with the Intevras Technologies Evras process to evaporate flowback. The entire volume of wastewater is evaporated and the solids are crystallized.
Evras unit at a site near Fort Worth, TX
GE has provided evaporative produced water treatment processes using mechanical vapor compression (MVC) evaporators for supplying high quality steams to oil shale operations in Canada. In September 2010, GE introduced a new mobile evaporator (GE 2010). The truck-mounted unit can process up to 50 gpm. The two-step distilling method consists of evaporator and crystallizer units. It can treat water high in TDS (up to 125,000 mg/L) to very low concentrations. The evaporation process reduces waste brine volume by up to 65% and with crystallization, by up to 95%.
Several other companies have developed thermal treatment processes that can be used to treat produced water and flowback water. A commercial oil and gas wastewater treatment facilitiy was opened for business in 2009 in West Virginia by AOP Clearwater. Although their website is vague about how the process works, they do indicate that the process will produce distilled water.
CSM (2009) includes descriptions of several other thermal treatment systems that are being used or are proposed for use to treat produced water or flowback water:
- Aquatech MoVap mobile evaporator for treating flowback water
- Total Separation Solutions PYROS system that uses cavitation to heat produced water to boiling.
Bruff, M., 2010, “An Integrated Water Treatment Technology Solution for Sustainable Water Resource Management in the Marcellus Shale,” presented at the 17th International Petroleum and Biofuels Environmental Conference, San Antonio, TX, August 31 – September 2. Available at http://ipec.utulsa.edu/Conf2010/Abstracts_2010/Bruff_34.pdf.
CSM, 2009, “Technical Assessment of Produced Water Treatment Technologies,” prepared by the Colorado School of Mines as part of RPSEA Project 07122-12, November. Available at http://aqwatec.mines.edu/produced_water/treat/docs/Tech_Assessment_PW_Treatment_Tech.pdf
Dees, D., 2010, “Flowback and Producecd Water: from Total Use to Total Discharge, presented at the 17th International Petroleum and Biofuels Environmental Conference, San Antonio, TX, August 31 – September 2. Available at http://ipec.utulsa.edu/Conf2010/Abstracts_2010/Waits_6.pdf.
GE, 2010, “Thermal Treatment for Unconventional Gas Frac Water and Produced Water,” a GE fact sheet. Available at http://www.geunconventionalgas.com/images/GEA17907%20Evaporative%20Treatment_R2.pdf.
Halldorson, B., 2010, “Successful Shale Gas Water Management - A Comparison Between US Shale Plays,” presented at the 17th International Petroleum and Biofuels Environmental Conference, San Antonio, TX, August 31 – September 2. Available at http://ipec.utulsa.edu/Conf2010/Powerpoint%20presentations%20and%20papers%20received/Halldorson_60_received9-7-10.pdf.
Veil, J.A., 2008, “Thermal Distillation Technology for Management of Produced Water and Frac Flowback Water,” Water Technology Brief #2008-1, prepared for the National Energy Technology Laboratory, May. Available at http://www.ead.anl.gov/pub/dsp_detail.cfm?PubID=2321.