When Vancouver-based Saltworks Technologies first made news in October 2009, it did so in a big way. Initial coverage of the company’s thermal ion exchange desalination process was reported in an upbeat, optimistic story in the Economist.
The following week, Saltworks’ CEO Ben Sparrow gave invitation-only presentations of the company’s Thermo-Ionic technology in a Dubai hotel room near the site of the IDA World Congress.
WDR attended one of the private sessions in Dubai but was disappointed that no flow diagram was made available, and a black plastic panel hid the most interesting parts of the suitcase demonstration unit.
Saltworks president and co-founder Josh Zoshi conceded that the company was cautious when it began talking publicly about its technology. “At first, we held our cards close to our chest as we sought to understand the landscape and further develop our membrane and patent portfolio. Since the Dubai IDA Congress, we have shifted our focus from desalting seawater to volume reduction of RO concentrate management and waste brines,” he told WDR.
The heart of the Saltworks Thermo-Ionic process is a desalting device that uses ion exchange membranes in an arrangement resembling electrodialysis reversal (EDR). In fact, the system employs polarity reversal to reduce scaling. Unlike EDR, however, the system uses the energy contained within a concentrated salt solution, rather than external power, to initiate the desalting process. The hypersaline solution is produced in a special evaporative unit that operates at a temperature 10°C warmer than the ambient wet bulb temperature.
The system employs a proprietary ion exchange membrane developed and manufactured by Saltworks. The robust, highly conductive membrane is a novel, functionalized polymer that leverages technology from engineered plastics and films. “It is very different from the commercial styrene-DVB membranes used in electrodialysis, and much more cost-effective,” said Sparrow.
According to Sparrow, the energy requirements for the system are a fraction of that required by conventional brine management systems. “Besides solar heat, or another low-grade heat source for the evaporative unit, the only external energy requirement is the electricity needed to run the circulation pumps and fans. The remaining energy needs are produced by the hypersaline solution,” he said.
Because the unit relies on salinity gradients for internal voltage generation, the net salt flux, or current density, is lower than EDR, requiring more membrane area.
The company has partnered with SPX Cooling Technologies to develop an air-cooled tower that is able to achieve zero liquid discharge (ZLD) and harvest the precipitated salts without scaling. Like most of the Saltworks system, the evaporative unit is constructed primarily of nonmetallic materials.
For most standalone applications, the Thermo-Ionic system can operate over a feedwater TDS range of 20,000 to 80,000 mg/L. When combined in a hybrid configuration with RO, the system is practical with a feedwater salinity as low as 2,000 mg/L TDS.
In addition to more than one year of fully automated bench testing on a variety of feedwaters, the company has a seawater pilot unit that has been operating for 1-1/2 years, which continues to provide long-term operational data.
A 100 m3/d (26,420 GPD) demonstration plant is now being constructed to demonstrate the process as a ZLD alternative for a Canadian oil sands project. They have also started bench trials on an oilfield produced water application to recover water and reduce the concentrate discharge volume. This project has led to a $3.5 million investment from Teck Resources, Canada’s largest mining firm, and a major Canadian oil and gas company.
Plans call for having a commercial unit in operation in the summer of 2012.
WDR’s CDR rating for this technology is 8.6.