“Water is … a pre-requisite to the realization
of all other human rights.”
(UN Committee on Economic, Cultural, and Social Rights)
CryoDesalination: Saltwater Desalination by Freezing
CryoDesalination is a new low cost desalination process that will provide access to fresh water and improve the lives of millions of people worldwide.
Life on our planet requires fresh water. According to WHO, water scarcity affects roughly one-third of the world’s population, approximately 2.3 billion people. The World Water Council states that this water crisis will become more acute over the next fifty years as the world population increases. Yet, water covers nearly three quarters of our planet -- 97.5% of this water is saltwater. Therefore, a practical, economically viable desalination process is crucial to overcoming this crisis.
Present State of the Art in Desalination
Today, the most commonly used desalination processes are variations of thermal processes (multistage distillation and vapor compression) and membrane processes (reverse osmosis). These systems have steadily evolved and improved in performance over the years but have not yet attained the elusive goals of environmental friendliness and low operating costs needed by a thirsty world. They have systemic problems: polluting chemicals, membrane fouling, capacity limitations, expensive construction materials, and high-energy demands.
Much research in desalination by freezing took place in the decades from 1950 to 1980 motivated by an interesting natural phenomenon: ice made from saltwater is salt-free. Desalination by freezing sparked considerable interest due to its inherent advantages of low energy requirements, low cost, relative simplicity, and small environmental footprint. However, researchers encountered a major obstacle. They found it difficult to separate the ice from the brine and obtain salt-free water. Due to this separation problem, interest in the freezing process waned.
Our Process – Original and Distinctive Features
We have solved the problem of separating ice from brine by a method never previously used in freeze desalination: flotation.
Simply stated, the method works as follows: ice floats on water. Many fluids also float on water. By selecting a fluid that floats in-between ice and brine we can effectively separate the ice from the brine. Harvesting this separated ice produces fresh water.
The science underlying the freezing desalination process is simple. When saltwater freezes, the resulting ice consists of salt-free water. As ice forms, it rejects the salt, which remains in the brine.
In saltwater, ice forms as irregular ice crystals. When in contact with a liquid, these crystals become slush. Brine adheres to the crystals and becomes trapped. Complete removal of brine from slush is difficult to achieve. As a result, when the ice melts becoming water, the residual brine in the slush makes the water salty. This is the reason freeze desalination failed in the past.
Our approach overcomes this problem and successfully achieves ice-brine separation by interaction of oil, brine, and ice in a separation column. CryoDesalination is highly energy efficient. The efficiency approaches the thermodynamic minimum. This efficiency is achieved by using the “cold energy” in the ice to condense the refrigerant vapors, thereby recapturing a substantial portion of the energy expended to make the ice.
CryoDesalination has lower capital and operating costs than any other desalination process because:
· Freezing water to ice and then melting it to obtain fresh water, requires considerably less energy than either thermal or membrane processes require to produce an equal quantity of fresh water
· We use low-cost materials because we experience little corrosion as a result of operating at low temperatures
· We require less maintenance because we have neither scaling nor membrane fouling as occur in thermal and membrane processes
· We do not incur the cost of chemicals required in thermal and membrane processes to prevent scaling and membrane fouling (and importantly, we do not pollute the environment because we do not use these or any other chemicals)
· We realize economies of scale because we have no constraints on equipment size. We do not require multiple trains to increase capacity.
· We pump all fluids, ice being always present as slurry in either brine or oil, which enables us to break the plant capacity barrier. This is an extremely important feature of our process because it is now possible to increase plant throughput to any desired capacity without duplicating equipment as required in other desalination processes.
Our goal is to disseminate CryoDesalination as rapidly as possible. Currently, the process has two broad applications:
1. Desalination of saltwater for human consumption and agriculture
2. Desalination of produced water from oil & gas exploration
Environmental Help for the Oil and Gas Industry
In addition to our main goal of providing water to improve living conditions, the CryoDesalination process also provides a needed solution to a major environmental problem.
Newer environmental regulations now require the oil and gas industry to treat huge quantities of water. These waters are by-products of oil and gas production and hydraulic fracturing and are known as “produced waters”. A major component of most produced waters is salt.
Typically, each barrel of oil produces three to seven barrels of produced water. Previously, these waters were disposed untreated into streams, lakes, oceans, or abandoned wells. More recently, produced water is often trucked to centrally located treatment centers. Trucking is costly. It uses energy resources, causes air pollution, and increases road congestion. Most treatment centers cannot remove the salt from produced waters that have high salt concentrations, however these high salt concentrations are not an obstacle for the CryoDesalination process.
The need to desalinate produced waters from oil and gas operations is urgent. Currently, there is no economical and environmentally sound method for removing the salt from produced waters. Successful field tests of CryoDesalination units will hasten their acceptance and use. CryoDesalination units installed at the wellhead would eliminate the expense of trucking, decrease pollution, provide fresh water, and enable greater compliance with environmental regulations.
Win-Win: Linking with LNG Vaporization Facilities
Besides capital costs, the major expense of our process is the cost of energy for refrigeration. Under certain circumstances, we can obtain “free energy” by linking CryoDesalination units with Liquid Natural Gas (LNG) vaporization facilities.
By linking the vaporization and CryoDesalination plants, saltwater can be frozen without incurring refrigeration costs. As LNG vaporizes, it provides the refrigeration needed to freeze the saltwater. By the same token, as saltwater is chilled, it provides the heat needed to vaporize LNG. This is a win-win situation for both plants: such an arrangement drastically reduces the production cost of drinking water as well as the cost of vaporizing LNG. Linking of plants would benefit the many countries that simultaneously import LNG and suffer from water scarcity, such as India and Spain. Other countries suffering from water shortages are now building LNG import facilities. They would benefit from linking.
CryoDesalination was invented by Norbert Buchsbaum, a veteran chemical engineer. He started his career with a major engineering and construction company. As a process engineer, he participated in the design of numerous chemical, petrochemical, and pharmaceutical plants. He has a number of patents in the fields of crystallization, distillation, and energy recovery. His successful innovations in plant design led to management positions: Director of Engineering of a large international pharmaceutical company and later, Vice President Corporate Engineering of one of the “Seven Sisters” group of major oil companies.
In the 1960’s, as a young engineer, Norbert lead a team designing a US government sponsored freeze desalination demonstration plant installed in Wrightsville Beach, North Carolina. Like all other demonstration plants of the time, it confirmed that problems with ice-brine separation and scale-up were major obstacles to further development.
Norbert is fully cognizant of the ravages caused by the lack of fresh water, which he personally experienced as a child refugee during World War II. Spurred by these experiences and new ice-brine separation concepts he developed, he saw an opportunity of resuscitating a technology that has the potential of saving lives and improving the well-being of many people.
CryoDesalination has the potential of helping those endangered by water scarcity, of bringing relief to the millions who lack water -- improving health, saving lives, irrigating crops, and liberating future generations from dismal conditions.
CryoDesalination has the potential of delivering invaluable help to the victims of unexpected catastrophes: earthquakes, tsunamis, hurricanes, floods, etc. During such events, water is among the first and most vital needs. In the wake of the 2010 Haiti earthquake the lack of fresh, clean water resulted in a cholera outbreak that so far has killed over 7,900 people. Immediate intervention providing clean water can prevent epidemic disease outbreaks and save lives. Prefabricated CryoDesalination package units can meet this need and can rapidly be shipped and placed into operation.
Even in situations that are not dire, there is much benefit from access to inexpensive and plentiful water. Obtaining water via less costly methods can free funds for other worthwhile causes such as schools, hospitals, and other activities -- raising the overall quality of life in many communities.