FAQs

CO2 Removal

If the DO removal of X-40 and X-50 fibers are identical and X-50 fiber is better suited for CO2 removal, then why not have only one product – X-50?
The answer to this question relates to another property of fibers called porosity. Porosity is basically defined as the number of pores for a given amount of surface area. In order to process CO2 in the large volumes often required, a more porous membrane is required. A more porous membrane allows more gases to be removed. However, water vapor can also pass through the membrane pores during this process. The drawback to a more porous membrane is that increased amounts of water vapor are also passed through the membrane. While not excessive, this water vapor must also be processed by the other equipment in the degassing system and the additional water vapor load must be accounted for in the vacuum portion of the design. This requires increased vacuum pump capacity. Therefore, using X-40 fiber can provide a more economical system design because a smaller vacuum pump can be used.

What kind of system do you recommend for CO2 removal?
A few options are available. A sweep only with either compressed air or a blower for suctioning atmospheric air may be used. A vacuum with atmospheric air sweep also works well.

What minimum concentration of CO2 can you obtain with a Liqui-Cel Contactor?
CO2 can be removed to as low as 0.5ppm. Our warranty guarantees down to 1ppm.

Ink Jet Ink and Coating Debubbling

What is the range of vacuum required for proper 0.5x1 SuperPhobic MicroModule operation?
A small vacuum pump capable of pulling ~50-150 Torr (~1-2acfm air) will suffice. The deeper the vacuum, the more efficient the O2 removal. It is important to not pull vacuum beyond the limits of the most volatile solvent in the ink.

Do you recommend plugging the second vacuum port, leaving it open, or drawing vacuum from both vacuum ports?
Either way yields about the same results. For applications with space limitations, one end should be plugged.

Where should my SuperPhobic Contactor be positioned in the printer?
The SuperPhobic Contactor should be placed just before the printhead. Ideally, the contactor should stand vertical with liquid flowing in through the bottom and out of the top.

How does the SuperPhobic Contactor differ from Liqui-Cel Contactors?
The membrane in the SuperPhobic device has a non-porous, gas permeable skin on the outer surface. It is a gas selective membrane and cannot be characterized by a pore size. Membranes that are porous are not gas selective.

How viscous of a solution can a SuperPhobic Contactor tolerate?
UV curable inks and coating solutions with viscosities as high as 4,000cp have been degassed using SuperPhobic Contactors.

Will the ink penetrate through the membrane into the pump?
Typically no. It is important to not pull vacuum beyond the limits of the most volatile solvent in the ink.

Which SuperPhobic Contactor is right for me?
The contactor size is determined by the flow rate. This information is available on the data sheet for each contactor.

Do I need a contactor for each ink?
Yes.

What is the priming volume of the contactor?
The priming volume is different for each contactor. This information is available on the data sheet for each contactor.

What level of gas removal can I achieve with a SuperPhobic Membrane Contactor?
An efficiency chart is available on the data sheet for each contactor. However, each ink is different and would need to be tested to determine exact performance.

How do you test ink degassing efficiency?
Most customers test by observation and print quality. A special probe capable of measuring dissolved gasses can be purchased from third party sellers, however, these meters and probes can be quite expensive.

How long does a SuperPhobic Contactor last?
Every ink is different so it is difficult to determine the life expectancy of the contactor. It can depend on how much ink and dissolved gas is passed through the contactor. 2-5 years is not uncommon for a typical SuperPhobic Contactor.

Liqui-Cel

Why would I choose Liqui-Cel^® Membrane Contactors over vacuum towers or forced draft degasifiers?
- Small footprint (10X the surface area per volume compared to vacuum towers)
- Low Operating Costs
- Clean, contamination free, degassing in a closed system
- Accurate Gas Control
- No Chemical requirements
- Modular contactors are easy to expand as flow rates increase or water specifications change
- Low pressure drop (repressurization pumps are not needed)

What are the most common applications?
- Oxygen removal (<1ppb is easily achieved)
- Carbon dioxide removal (1 ppm is easily achieved)
- Nitrogen removal
- Humidification of gasses
- Debubbling water, inks, emulsions, developers
- Hydrogenation
- Nitrogenation
- Carbonation

Are Liqui-Cel^® Membrane Contactors really economical compared to other oxygen removal technologies?
As with any purchase, you should evaluate the "cost of ownership" of each technology. Modularity, stable operation, minimal instrumentation, and no chemical introduction are all attributes of Liqui-Cel Membrane Contactors that can save you time and money. The capital and operating cost will depend on your specific needs. Generally, Liqui-Cel Membrane Contactors will be more economical than a vacuum tower, catalytic system, and some forced draft degasifiers. Chemical scavenging and steam deaerators are tough competitors, but you should evaluate Liqui-Cel Technology as an option to fully understand your alternatives.

What about Liqui-Cel^® Membrane Contactor economics for CO₂ removal?
Liqui-Cel Membrane Contactors offer great advantages over conventional technology when removing CO2 at medium flow rates or when removal of O2 is done at the same time. At large flow rates, the economics are case dependent on customer needs. Liqui-Cel Membrane Contactors are the only cost effective technology capable of removing CO2 down to 1 ppm without introducing any contaminates (including oxygen) to your pure water stream. We also commercialized a new 6-inch product variant in 2001 that was designed to meet the economic requirements of CO2 removal applications. Many customers have taken advantage of Liqui-Cel Membrane Contactor modularity by splitting the degasification processes and using the first bank of contactors to remove CO2 and some O2, and using the second bank of contactors to remove O2 to very low levels.

Are Liqui-Cel^® Membrane Contactors able to withstand free chlorine? What about ozone?
Liqui-Cel Membrane Contactors are compatible with free chlorine at pH > 7, a concentration not higher than 100 ppm, limited exposure time and ambient temperature. The following formula will give you the maximum exposure time when the contactor is exposed to Cl2. Max. Exp. time (hr) = 26000 / actual Cl2 concentration (ppm). If the contactor is overexposed, fibers will start loosing their mechanical properties. Ozone at concentrations above ppt levels is NOT COMPATABLE with Liqui-Cel Membrane Contactors.

What do you recommend for contactor servicing? Do I need special equipment?
Many of our contactors are disposable. However, our 4" contactor in a stainless housing and our 10" contactors require special tools available from Membrana - Charlotte. Assembly / disassembly guides will assist you step by step in the use of the tools and will also indicate the spare parts needed. When servicing the 10" contactors, you need to be aware that the 10" stainless steal assembly weighs around 220 lbs, therefore the use of a hoist is highly recommended, if you are planning to take the contactors out of the system.

I see a slight amount of water coming from a contactor and going to my vacuum pump. Is this normal?
The polypropylene hollow fiber used in the contactors is a hydrophobic material, preventing liquid water in your gas phase. However, when using a dry sweep gas, vacuum, or a combination, water vapor will cross through the membrane from the liquid to the gas phase (this is normal). The amount of water vapor going to the gas phase will depend on your process conditions (mainly water temperature and vacuum level). This water vapor may condense in your vacuum line if ambient temperature is low enough. If you want to determine if the amount of water you are seeing is nominal, contact your Membrana representative.

Can I use an oil ring vacuum pump?
Yes, but you need to be aware of water vapor condensation inside your vacuum pump, which means you will need to service the pump more frequently. If you are planning to use an oil seal vacuum pump, we recommended installing it down stream from a water trap. We highly recommend liquid ring vacuum pumps.

What level of filtration do I need to put in front of Liqui-Cel^® Membrane Contactors?
The level of filtration depends on your water source. If your water source is from a RO system, no filtration is needed. For all other water sources, a 10 micron filter is recommended.

How do I know how many Liqui-Cel^® Membrane Contactors I need for my application?
The Liqui-Cel Membrane Contactor team has developed an easy to use sizing program that allows you to estimate the number of contactors needed for your application. Call your Membrana representative for further assistance.

I don't want to be the first to use Liqui-Cel^® Membrane Contactors. How many installations do you have and how long have they been running?
With our different product sizes, we have thousands of systems running around the world. Flow rates range from a few ml/min to over 1600 m3/hr (>7,000 gpm). Our first systems have been running for 10 or more years and our contactors have been used for over 20 years.

What is the lead time for ordering Liqui-Cel^® Membrane Contactors?
This is a definite advantage. For small orders (less than 5 contactors), we will normally ship within 48 hours. For larger orders, lead time to ship is normally 48 hours to 2 weeks.

What do the numbers 4x28, 10x28, etc. mean?
These numbers represent the approximate dimensions of the cartridge that is inside the housing of the Liqui-Cel Membrane Contactor. The cartridges vary in dimension based on the product capacity. For example, 4x28 would indicate a 4 inch diameter cartridge that is 28 inches long.

What are the basic differences between the X-40 and X-50 fibers?
These numbers identify the type of membrane used for gas removal from water. Each fiber type has been designed with unique properties that maximize gas removal efficiency. For example, X-40 fiber is best suited for dissolved oxygen (DO) removal from water. However, because most CO2 removal applications require significantly larger volumes of gas removal than DO removal applications, the X-50 was developed with a larger fiber ID to allow more gas to sweep through the fiber. Therefore, the X-50 fiber is the better choice for carbon dioxide (CO2) removal from water.

Is there a proper flow direction for the liquid?
Liquid flows on the shell side of the device for all extra-flow membrane contactors of 2.5-inch diameter and larger. It does not matter which shell side port is selected as the inlet. The key is that the gas flow through the fiber should be counter-current to the liquid flow.

Can a membrane contactor with rotated gas ports be installed in a vertical position?
Yes. In this situation, condensation is easily drained away by gravity. There may also be a piping design where it is more advantageous to have the gas ports oriented 180º apart while installing the contactors in a vertical position. This offers the system designer another degree of flexibility in piping layouts.

Does Membrana supply complete systems or skids?
No. Membrana provides Liqui-Cel Membrane Contactors, liquid ring vacuum pumps and a few related accessories. We can refer you to an OEM who can build a complete system to your specifications.

What is the life expectancy of a Liqui-Cel Contactor?
A good estimate would be 5-10 years with clean, post RO, prefiltered water.

Can Liqui-Cel Contactors tolerate chlorine / chloramines?
The lifetime exposure limit for chlorine is 24,000ppm-hours. Assuming your water has 2ppm, this translates to an approximate life of 12,000 hours or 500 days (assuming 24 hours / day operation). It is thought that Chloramines are not as oxidative to the Polypropylene (PP) membrane as chlorine, but there is no data to confirm this.

Can Liqui-Cel Membrane Contactors remove gasses from Acetonitrile or other solvents?
Liqui-Cel Contactors have been used to remove gasses, including Argon, from solvent solutions. There is not a chemical compatibility problem, but there is a low surface tension issue similar to other chemicals such as IPA. An aqueous solution of Acetonitrile may not wet out the membrane, but pure Acetonitrile would.

If the temperature is ambient, SuperPhobic Contactors may work. The membrane in this contactor may be affected by Acetonitrile to some extent, therefore a pilot trial is recommended. Pure solvents might wet out the membrane, causing liquid to cross over to the lumen side of the contactor. Refer to the Liqui-Cel Chemical Resistance Guide for a thorough list of chemicals and the compatibility with components of the Liqui-Cel Contactor.

Can Liqui-Cel Contactors be used in desalination?
Liqui-Cel Membrane Contactors have been used in research studies for such purposes. However, no products have been commercialized due to the short life span of the membrane when used in this type of application. A capillary Hollow Fiber Membrane with large diameters and very high porosity is recommended. We have suitable membranes, but the temperature is limited to 45 C.

What is the liquid pressure drop across a Liqui-Cel Contactor?
Liquid pressure drop is determined by the flow rate and the contactor used. Pressure drops are typically low enough that a recirculation pump is not required. Actual pressure drop ranges are provided on the back of the product datasheet.

What connections are available on the Liqui-Cel Contactors?
Each contactor has various connection options. Please refer to the Liqui-Cel datasheet for the specific connections available on each product.

How do I determine which Liqui-Cel Contactor is right for me?
The flow rate and the specific application are used to determine the size and type of contactor required.

How do I determine which fiber is right for my application?
X-40 fiber is typically used for O2 removal. X-50 fiber is used for CO2 and all other gas removal. X-40 fiber is also used for carbonation or other gasifying applications.

Where can I find references of similar systems from other customers?
References can be requested from your sales representative. There is also find a list of installations online at http://www.liqui-cel.com/product-information/overview-brochures.cfm

Where can I find a general system design or P&ID for a complete Liqui-Cel system?
Generic system designs are available. Contact your sales representative or locate these designs online at http://www.liqui-cel.com/technical-resources/system-pids.cfm

How do I clean my Liqui-Cel Contactor?
Please review the Cleaning Guide. It can be found online at http://www.liqui-cel.com/technical-resources/startup-operating-guides.cfm

How frequently do I need to clean my Liqui-Cel Contactor?
This varies by application. For general guidelines, please refer to the Cleaning Guide at http://www.liqui-cel.com/technical-resources/startup-operating-guides.cfm

What can I use to clean my Liqui-Cel Contactor?
Please review the Cleaning Guide. It can be found online at http://www.liqui-cel.com/technical-resources/startup-operating-guides.cfm

What is the maximum temperature tolerance of a Liqui-Cel contactor?
Each contactor has a different operating pressure and temperature maximums. This information is available on the datasheet for each contactor and in the Operating Guide.

How do I start my Liqui-Cel Contactor system?
Refer to the Start-up Guide for your specific product. Additional information is also located in the full operating guide for contactors 2.5x8-inch and up.

Why is vertical mounting preferred over horizontal mounting?
Vertical mounting allows for contactors to be drained properly for storage when not in operation. Horizontal mountings are only recommended for continuous flow systems that will not be shut down for any significant time.

What is the preferred mounting orientation for Liqui-Cel Contactors?
Vertical mounting is recommended for optimal draining. See Operating Guidelines for special notes if horizontal mounting is preferred for your application.

How will I know if my Liqui-Cel Contactor is not working properly?
If the contactor is not degassing properly then there may be a deficiency in gas removal, an increase in pressure drop across the contactors and possibly leaks in the contactor.

What would cause leaks in the membrane?
A leak could be the result of the wetting out of the membrane, oxidized fibers, or leaks in the seals or potting.

What would cause wet out in the membrane?
Wet out usually occurs when surfactants or other low surface tension fluids enter the contactor and penetrate the pores of the fiber. This creates a wicking action that allows constant penetration of the liquid from the water to the gas side of the membrane. Some industrial caustics and other cleaning chemicals contain small amounts of surfactants. Surfactants and soaps should be avoided.

Can wet out be treated so that the contactors can be put back into operation?
Yes. Proper cleaning will usually resolve the wet out issue without requiring a replacement.

What chemicals are safe and what should be avoided in a Liqui-Cel or SuperPhobic Membrane Contactor?
A Chemical Resistance Guide is available that displays a number of chemicals that are tolerated in a Liqui-Cel Membrane Contactor. This guide can be found online at http://www.liqui-cel.com/technical-resources/startup-operating-guides.cfm

What housing materials are Liqui-Cel Contactors available in?
Each contactor has varying housing options. This information is available on the datasheet for each contactor.

What are the reasons Liqui-Cel Membrane Contactors would need to be replaced?
Oxidized fiber or irremovable particle fouling are typical reasons a Liqui-Cel Membrane Contactor would need to be replaced.

What are the benefits of a Liqui-Cel Membrane Contactor over existing technologies?
Liqui-Cel Membrane Contactors are safer and cheaper than chemical dosing. These devices can be prefabricated and skid mounted for easy building and moving. They are an in-line solution where an additional recirculation pump is not required. These features, along with minimal power costs, make them more economical than conventional methods. Reduced blow down time and ease of cleaning are additional benefits that a Liqui-Cel Membrane Contactor system has over other degassing methods. Liqui-Cel Membrane Contactors also have a short lead time.

How much does a Liqui-Cel Contactor cost?
Each contactor is priced differently and prices vary by quantity ordered. Contact a Liqui-Cel representative to size a system for your application and to obtain cost and availability.

What is the lead time for a Liqui-Cel Contactor?
Typical lead time is 1-2 weeks for MiniModules and MicroModules. Larger contactors have 2-6 week lead times.

Who do I contact for assistance regarding my Liqui-Cel Contactor?
Contact our Sales and Technical Support Team at (704) 587-8888.

How do I determine what has fouled my Liqui-Cel Contactor?
A water analysis report can be obtained to determine most contaminants. Backflushing with a screen filter is an option for catching large particles, including some carbon, to determine the nature of the fouling.

Can I remove carbon fouling from my Liqui-Cel Contactor?
Some of the carbon can likely be removed, but not all. Backflushing should be used to clean the contactor. A cleaning guide is available at http://www.liqui-cel.com/technical-resources/startup-operating-guides.cfm

Do you provide technical service and onsite service?
Yes. Sales and technical service representatives are available. On-site training and technical service is available for a small fee.

How do I change out the cartridge in my Liqui-Cel Contactor?
See the Assembly/Disassembly guides at http://www.liqui-cel.com/technical-resources/startup-operating-guides.cfm

What do I need to replace when I change out the cartridge in my Liqui-Cel Contactor?
Replacement of the cartridge and o-ring is typically recommended. Tool kits are available for this procedure. Refer to the change out guide for your contactor for specific replacement instructions and a description of the tools.

O2 Removal

Can a Liqui-Cel Membrane Contactor with X-50 fiber be used for dissolved oxygen (DO) removal?
The DO removal efficiency for X-40 and X-50 fiber is identical. Either device will work for DO removal.

What minimum concentration of O2 can you obtain with a Liqui-Cel Contactor?
Liqui-Cel Contactors can remove O2 to 1ppb.

What kind of system do you recommend for O2 removal?
A Liqui-Cel Contactor with X-40 fiber is recommended. The system can be designed to operate with vacuum only or combo vacuum with a nitrogen sweep for ultra pure water.

Other

Can Liqui-Cel Contactors remove arsenic from water?
Liqui-Cel Contactors cannot remove arsenic from water, but they can be used to deoxygenate surface water prior to injection into aquifers. It is believed that deoxygenating the water prevents oxidation of various minerals in the ground water, thereby preventing the mobilization of arsenic.

Can Liqui-Cel Contactors remove ammonia?
Liqui-Cel Membrane Contactors have been used for this application, however, each application is different. Therefore, we recommend a pilot trial to determine the actual membrane needs for your application. Liqui-Cel Contactors can remove ammonia in the NH3(g) form, but not in ammonium (NH4+) form. For efficient ammonia removal a pH >10 is required. If the pH can be adjusted, then you have a better chance of removal. Feel free to contact us to begin a pilot project with a Liqui-Cel Membrane Contactor.

Can I remove ammonia without adjusting to a higher pH?
Yes, but the removal will be low.

Can I remove THMs with Liqui-Cel Contactors?
Yes. Tech brief #12, "THM Removal with Liqui-Cel Membrane Contactors", explains the capabilities of this application.

System Building

Can I pipe my system so that the gas flows co-current to the liquid flow?
For maximum efficiency, the gas should always flow counter-current to the liquid flow. If a system is piped in a co-current configuration, it will not harm or damage the membrane contactor, but the system will operate less efficiently. All system designs and performance estimates are based counter-current flows. Therefore, it is likely that the system will not meet design effluent quality if operated in a co-current configuration.

Are any piping changes needed if the Liqui-Cel Contactors are installed in a horizontal orientation?
Yes. It is important to purchase the membrane contactors with the “R” suffix on the part number (ex: G449HR). The “R” denotes that one of the vessel end caps has been installed so that the gas (lumen side) ports are oriented (or rotated) 180º apart. Using this configuration, the membrane contactor should be installed so that one lumen side port is pointed up. The other gas port will be then be pointing downward. Sweep gas piping should be connected so the gas enters the membrane contactor through the port that is pointing upward. The gas should exit through the downward port. The purpose of this orientation is to provide a means for any condensation that occurs in the fibers to be continually drained from the fibers.

Will CO2 removal damage my vacuum pump?
There can be some corrosion in the liquid ring vacuum pump due to pH shift with CO2 removal. A liquid ring vacuum pump with stainless steel wetted parts is recommended for high levels of removal. For moderate to low levels a standard liquid ring pump with a cast iron impellor may be more economical. The cost of a pump with stainless steel wetted parts is about double that of the standard pump.

Do I really need everything in the P&ID?
The P&IDs are recommended system designs intended only to provide a guideline. They include various elements that facilitate troubleshooting and promote safety.

What kind of prefilter do I need prior to my Liqui-Cel Contactor?
A 5-10 micron filter on the liquid side will suffice. A 3 micron filter is recommended for the gas inlet.