3M Membrane Filtration (formerly Membrana)

TB 56: Power plant in thailand uses liqui-cel® membrane contactors to remove co2 from water


Courtesy of Courtesy of 3M Membrane Filtration (formerly Membrana)

A major power plant in Thailand is using Liqui-Cel® Membrane Contactors to remove carbon dioxide from a DI water system. The system is an expansion project and will be used to feed a high pressure boiler. Liqui-Cel Contactors are being used to lower the CO2 inlet into an Ionpure EDI system. Carbon dioxide adds an ionic load to the EDI system, which can reduce the performance of the system. Manufactures of the EDI equipment suggest lowering the inlet CO2 to reduce the load on the equipment and improve the water quality.

The system was designed, built and installed by Liquid Purification Engineering International Co., Ltd. in Bangkok Thailand. LPE designed the DI water system as an all membrane based system that does not require the use of ion exchange resin or chemicals. The system uses a double pass RO membrane, a Liqui-Cel Membrane Contactor and Ionpure EDI technology. The system produces water with a resistivity >16.0 MΩ-cm. (See water quality and flow diagram.)

The Liqui-Cel Membrane Contactor system consists of one 14-inch Membrane Contactor that operates in combination mode using vacuum and air sweep.

Liqui-Cel Membrane Contactors utilize a hydrophobic polypropylene membrane to remove dissolved gasses from water. Water flows on one side of the membrane and a vacuum or strip gas is passed on the other side of the membrane. In this system air is drawn into the membrane under vacuum. The high flow rate of air sweep under vacuum creates a driving force to move the dissolved carbon dioxide from the water into the gas phase.

Historically, forced draft deaerators have been used to remove CO2 from water. This type of deaerator uses ambient air that is fed into the tower with a blower, putting the air in direct contact with the water. This direct air-to-water contact opens the system up to possible water contamination from any contaminants that are present in the air. For this reason, using a forced draft deaerator downstream of an RO membrane system is not recommended.

Membrane Contactors, however, are well suited to remove dissolved carbon dioxide and other dissolved gasses along side of an RO membrane system because the membrane has tight 0.03 μm pores that prevent air stream contamination from coming into contact with the RO water.

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