Engineers at the Massachusetts Institute of Technology have devised a process that they say could clean water used for hydraulic fracturing at relatively low cost. The new technology is described in a series of papers recently published in three journals: the International Journal of Heat and Mass Transfer, Applied Energy and the American Institute of Chemical Engineers’ AIChE Journal.
The method is a variation of the standard distillation process, in which salty water is vaporized and then condensed on a cold surface; the salt separates out during evaporation. But this process is energy-intensive — and therefore costly — because all the water must be heated to the boiling point, while the condensing surfaces must be kept cold.
In the new process, water well below the boiling point is vaporized by direct contact with a carrier gas; the moist air is subsequently bubbled through cooler water where the purified vapor condenses. But the temperature difference between the warm and cool water is much less than in conventional dehumidifiers, and the surface area provided by the small bubbles is much greater than that of a flat condenser surface, leading to a more efficient process.
The traditional version of this process is called a humidification dehumidification (HDH) desalination system. While other groups have designed HDH systems, this new version requires far less energy than previous systems, the team says. The researchers have already filed for patents on the system, and the team has set up a company to commercialize the process in collaboration with another MIT group that has been pursuing a related system for desalination.
While the ultimate goal of the project is desalination in developing countries, the researchers say their technology is also especially well suited for treating the produced water that comes from natural gas wells through the hydraulic fracturing process. This water is typically several times saltier than seawater, which makes it a particularly good candidate for treatment with the HDH process since, unlike membrane-based desalination systems, this system’s efficiency is unaffected by saltier water.
Source: MIT
The method is a variation of the standard distillation process, in which salty water is vaporized and then condensed on a cold surface; the salt separates out during evaporation. But this process is energy-intensive — and therefore costly — because all the water must be heated to the boiling point, while the condensing surfaces must be kept cold.
In the new process, water well below the boiling point is vaporized by direct contact with a carrier gas; the moist air is subsequently bubbled through cooler water where the purified vapor condenses. But the temperature difference between the warm and cool water is much less than in conventional dehumidifiers, and the surface area provided by the small bubbles is much greater than that of a flat condenser surface, leading to a more efficient process.
The traditional version of this process is called a humidification dehumidification (HDH) desalination system. While other groups have designed HDH systems, this new version requires far less energy than previous systems, the team says. The researchers have already filed for patents on the system, and the team has set up a company to commercialize the process in collaboration with another MIT group that has been pursuing a related system for desalination.
While the ultimate goal of the project is desalination in developing countries, the researchers say their technology is also especially well suited for treating the produced water that comes from natural gas wells through the hydraulic fracturing process. This water is typically several times saltier than seawater, which makes it a particularly good candidate for treatment with the HDH process since, unlike membrane-based desalination systems, this system’s efficiency is unaffected by saltier water.
Source: MIT
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