AMI Water Treatment Capabilities

About AMI Degasifiers with Liqui-Cel® Membrane Contactors

AMI water degasifier systems use Liqui-Cel membrane contactors, leading gas transfer devices that have been used in many industries around the world for over 20 years. Carbon dioxide removal and deoxygenation are among the common applications. Capable of achieving <1ppm CO2 and <1ppb O2, AMI Water Degasifiers using Liqui-Cel membrane contactors provide significant benefits to industrial processes by removing gases from liquids. For example, carbon dioxide and oxygen removal can reduce the impact of corrosion on boilers and piping to protect captial investments and reduce operating costs. Removing these gases can also improve process efficiency and prevent negative impacts on production yields related to dissolved gases. Because of their cleanliness and predictability, Water Degasifier systems using Liqui-Cel Membrane Contactors are the standard degassing technology installed in ultrapure water systems for the semiconductor, microelectronics and many other industries.

Although other degassing technologies, such as vacuum towers and forced draft dearators have existed for many years, these older methods are being rapidly replaced by degasification systems using Liqui-Cel Membrane Contactors due to the smaller footprint, lower installation costs and the modular nature of the membrane contactor system.

How Water Degasifier Membrane Contactors Work

AMI water degasifiers use Liqui-Cel Membrane Contactors with a microporous hollow fiber membrane to remove gases from liquids. The hollow fiber is knitted into an array and wrapped around a center tube inside of the contacter housing.

During typical operation, liquid flows over the shellside (outside) of the hollow fibers while a vacuum is applied to the lumenside (inside) of the fibers. Because the membrane is hydrophobic it acts as an inert support that allows direct contact between a gas and liquid phase without dispersion. Applying a higher pressure to the liquid stream relative to the gas stream creates the driving force for dissolved gas in the liquid to pass through the membrane pores. The gas is carried away by the vacuum pump.

What is Reverse Osmosis?

Reverse Osmosis (RO) is a membrane separation water purification process in which feed water flows along the membrane surface under pressure. Purified water permeates the membrane and is collected, while the concentrated water, containing dissolved and undissolved material that does not flow through the membrane, is discharged to the drain.

The key requirements of Reverse Osmosis (RO) process are a membrane and water under pressure. Other requirements include prefiltration to remove suspended impurities and carbon to remove chlorine (damages the membrane).

Most membranes remove 90-99+ % of the dissolved impurities depending on the impurity and the composition of water.

Reverse Osmosis, combined with pre-filtration, is able to remove 90 to 99.99% of the dissolved impurities that reside in your water.

Reverse osmosis systems (RO Systems) remove salts, microorganisms and many high molecular weight organics. System capacity depends on the water temperature, total dissolved solids in feed water, operating pressure and the overall recovery of the system.

What is Ultrafiltration?

Ultrafiltration is a separation process using membranes with pore sizes in the range of 0.1 to 0.001 micron. Typically, ultrafiltration will remove high molecular-weight substances, colloidal materials, and organic and inorganic polymeric molecules. Low molecular-weight organics and ions such as sodium, calcium, magnesium chloride, and sulfate are not removed. Because only high-molecular weight species are removed, the osmotic pressure differential across the membrane surface is negligible. Low applied pressures are therefore sufficient to achieve high flux rates from an ultrafiltration membrane. Flux of a membrane is defined as the amount of permeate produced per unit area of membrane surface per unit time. Generally flux is expressed as gallons per square foot per day (GFD) or as cubic meters per square meters per day. Ultrafiltration membranes can have extremely high fluxes but in most practical applications the flux varies between 50 and 200 GFD at an operating pressure of about 50 psig in contrast, reverse osmosis membranes only produce between 10 to 30 GFD at 200 to 400 psig.

Ultrafilter vs. Conventional Filter

Ultrafiltration, like reverse osmosis, is a cross-flow separation process. Here liquid stream to be treated (feed) flows tangentially along the membrane surface, thereby producing two streams. The stream of liquid that comes through the membrane is called permeate. The type and amount of species left in the permeate will depend on the characteristics of the membrane, the operating conditions, and the quality of feed. The other liquid stream is called concentrate and gets progressively concentrated in those species removed by the membrane. In cross-flow separation, therefore, the membrane itself does not act as a collector of ions, molecules, or colloids but merely as a barrier to these species. Conventional filters such as media filters or cartridge filters, on the other hand, only remove suspended solids by trapping these in the pores of the filter-media. These filters therefore act as depositories of suspended solids and have to be cleaned or replaced frequently. Conventional filters are used upstream from the membrane system to remove relatively large suspended solids and to let the membrane do the job of removing fine particles and dissolved solids. In ultrafiltration, for many applications, no prefilters are used and ultrafiltration modules concentrate all of the suspended and emulsified materials.