The Next Level In Water Purification
Centrifugal Vapor Distillation
Vapor compression distillation (VCD) has been the gold standard in water purification: the phase change results in a pure water distillate free of non-volatile contaminants. However, VCD is not cost-effective for widespread use because of its high-energy requirement, and it is susceptible to scaling. VCD can also cause “bumping” where micro-droplets of water can be ejected from a hot boiling surface and carry contaminants to the condenser, thus reducing purity.
Pristill has developed an advanced version of VCD called Centrifugal Vapor Distillation (“CVD”) or “Pristillization”. CVD eliminates many of the drawbacks of VCD including:
Reduced Energy required to distill water by more than 93% compared to VCD
Increased contaminant removal to 99.99% by reducing or eliminating bumping
Self-cleaning feature that reduces scaling, and allows units to process high salinity water sources or wastewater with limited pre-treatment
Centrifugal Vapor Distillation is a Game Changer in Water Purification
High Heat Transfer Coefficient
The efficiency of any boiler or condenser is determined by the overall heat transfer coefficient. A typical Vapor Compression Distillation (VCD) system has an overall heat transfer coefficient of 1,500 Watts per square meter per degree Kelvin.
By comparison, the Rotary Vapor Distiller designs showed consistent heat transfers nearly ten times higher than VCD.
The Pristiller CVD has a target overall heat transfer coefficient of 40,000 W/m^2/K. This is achieved by creating exceptionally thin films on the boiler and condenser surfaces. Pristill aims to constantly improve on the overall heat transfer of its systems.
High Energy Efficiency
High heat transfer efficiency leads directly to the CVD design having exceptionally low energy requirement to distill water. The energy required to distill seawater is 99.6% lower than standard distillation and 93% lower than VCD systems.
DOE/Sandia measured the energy required to purify seawater to be 2.6kWh/m^3 which is less than most RO systems. Pristill aims to improve on this energy efficiency further.
Contaminant Removal of 99.99+%
Early versions of the Pristiller technology (technically rotary vapor distiller) were tested and shown to remove ions to 99.95% purity. As a phase change system, the same level of purification would apply to any non-volatile contaminant including silica; non-volatile organic compounds; endocrine disruptors and active pharmaceuticals; biological contaminants such as bacteria, viruses and endotoxins; and micro- and nano-plastics.
Centrifugal Vapor Compression can deliver even higher levels of purity. In designing the CVD, many improvements were made to limit possible contamination including improvements to pumps and seals, and optimizing centrifugal purification to eliminate bumping.
Pristill’s goal is to consistently achieve 99.99% purity or higher. This level of purity is needed in order to achieve the exacting requirements of the most ultra-pure water needed for the electronics and semi-conductor industry, as well as for all pharmacological grades of ultrapure water.
Self-Cleaning, Anti-Scaling, Degassing, VOC Removal Capability
CVD Pristillers have a self cleaning capability in which the boiler surface is swept up to 20 times per second. The sweeping action disrupts the formation and attachment of precipitated salts and scale compounds: any solids are quickly swept into the waste stream. The room temperature operating conditions (~85 degrees F) also ensures that temporary hardness ions to not fall out of solution.
The self-cleaning design allows a Pristiller CVD to purify high-salinity water streams, with a goal of handling up to 250,000ppm. Pristill is designing systems to removal scaling ions and silica, so it can purify water without the need for softeners.
Pristill is also developing a Pristiller+ which will remove dissolved gases and many VOCs without the need for carbon filters.
Both carbon filters and water softeners are areas of vulnerability in ultrapure applications because they can act as reservoirs for bacteria, and amplify the release of endotoxins. Water softeners are also believed to be a source of high levels of polystyrene nano-plastics.
Simplified design for Ultrapure Water
With the development of Pristill’s anti-scaling technology, as well as dissolved gas/VOC removal of a Pristiller+, our goal is to simplify the number of steps in production of ultrapure grades of water. Should they be needed, additional purification steps can always be added post distillation, such as zeolite or carbon filter, to further remove compounds like ammonia down to sub 0.01ppb levels.
