HOW DO JOHNSON MATTHEY PURIFIERS WORK?
Palladium
Palladium membrane hydrogen purifiers operate via pressure driven diffusion across palladium membranes. Only hydrogen can diffuse through the palladium. The palladium membrane is typically a metallic tube comprising a palladium and silver alloy material possessing the unique property of allowing only monatomic hydrogen to pass through its crystal lattice when it is heated above nominally 300°C. The hydrogen gas molecule coming into contact with the palladium membrane surface dissociates into monatomic hydrogen and passes through the membrane. On the other surface of the palladium membrane, the monatomic hydrogen is recombined into molecular hydrogen - the ultrapure hydrogen used in the semiconductor process.
Palladium purifiers can provide <1 ppb impurity removal purity with any inlet gas quality including O2, H2O, CO, CO2, N2 and THCs. Palladium purifiers require heating and control systems, available from JM or provided by the customer.
Getter
Getter gas purifiers use two processes to remove impurities, adsorption and bulk diffusion. Impurities adsorb onto the surface of the getter material in the first step. The heated getter then allows the impurities to diffuse into the bulk of the getter material, binding it to the material. The reaction is irreversible, so the impurities cannot be released back into the gas stream. Getter purifiers remove O2, H2O, CO, CO2, N2 and THC. The getter is consumed during use, but the bulk diffusion provides very high capacities leading to long lifetimes.
Regenerable Catalytic
Catalytic purifiers operate via chemical and physical adsorption. Impurities react on the surface of the high surface area media and are held via chemisorption or physisorption. The reactions are reversible, so the purifier can be regenerated to purge impurities and allow the purifier to be used repeatedly. Impurities removed include O2, H2O, CO, CO2 and non-methane hydrocarbons (NMHC). Capacity for CO2 and NMHC is relatively small, so these purifiers are most often used when O2 and H2O are the key impurities to be removed. These purifiers require no heating or control system for POU applications.
HOW DO I DETERMINE WHICH TECHNOLOGY (Palladium, getter or catalytic) IS BEST FOR MY APPLICATION?
The choice of the best technology will be determined by the gas (ie, palladium is only for hydrogen), flow rate, inlet purity, duty cycle and outlet purity specification. Here are some simple tips:
Parameter
| Suggested Purifier
| Compressed hydrogen gas source
| HP or PSH Series palladium
| Liquid hydrogen source
| HP or PSH Series palladium, or PureGuard catalytic purifiers
| Need to remove N2 and CH4 from argon or helium, in addition to oxygen, moisture and carbon impurities
| PureGuard Wall Mount heated getter purifiers
| Nitrogen, argon or helium from bulk liquid source
| PureGuard catalytic purifiers
| Inlet impurity levels > 5 ppm
| HP or PSH Series for hydrogen; PureGuard regenerable purifiers for other bulk gases
|
Johnson Matthey will work with you to help select the best purifier for every application.
AT WHAT PRESSURES AND TEMPERATURES DO THESE PURIFIERS RUN?
- Palladium membrane purifiers – maximum operating pressure is 250 psig at 300 to 400 degrees Celsius
- Getter purifiers – maximum operating pressure is 250 psig at at 350 to 450 degrees Celsius
- Catalytic purifiers – maximum operating pressure is 250 psig at room temperature
WHAT IS THE LIFETIME OF THE PURIFIERS?
The palladium membrane technology used in the HP and PSH Series purifiers stops impurities on the inlet side and the impurities are vented, not adsorbed. Therefore, the palladium technology has a theoretical unlimited lifetime. IN practice, some purifiers may require replacement of the palladium tubes due to fatigue in high-volume, demanding applications. For these applications, life expectancy of the palladium membrane in hydrogen purifiers may be 5 years.
Zirconium getter used in the PureGuard Wall Mount Heated Getter purifiers, operating at the nominal flow rate with inlet gas quality of 99.999%, have a normal life expectancy of two years. The getter beds can be replaced to provide continued life.
Catalytic media used in the PureGuard catalytic purifiers, provided they are properly maintained and regenerated, can have unlimited life.
WHAT ROUTINE MAINTENANCE DO THESE PURIFIERS REQUIRE?
There is no routine maintenance required for a palladium membrane hydrogen purifier. For the catalytic purifiers, periodic regeneration is necessary, depending on the lifetime as determined by flow rates and inlet impurities.
WHAT DO YOU DO IF YOU SUSPECT PRODUCT FAILURE?
If a problem is suspected with the palladium membrane hydrogen purifier, a helium leak check should be performed. If the membrane is confirmed to be leaking please contact Johnson Matthey. Should impurity breakthrough of a catalytic POU purifier be suspected, the bed can be replaced or regenerated. Should impurity breakthrough of a heated getter purifier occur, contact Johnson Matthey about replacement of the vessel.
WHAT HAPPENS IF THE PURIFIER EXPERIENCES A POWER FAILURE?
A hydrogen purifier purge system, standard on the HP Series V-Purge and PSH purifiers, is recommended to automatically purge the hydrogen out of the palladium membrane system before the system cools down. For heated getter purifiers, the purifier will cool and manual restart is necessary when power is restored. Power failures do not affect ambient catalytic purifiers.
WHAT HAPPENS IF THE PALLADIUM MEMBRANE COOLS IN HYDROGEN?
Cooling in hydrogen leads to entrainment of the hydrogen in the palladium alloy lattice thereby causing stresses within the membrane, which over time increases the possibility of membrane failure. Purging with nitrogen is recommended.
ARE THE PURIFIERS HARD TO INSTALL?
Following the technical manual supplied, Johnson Matthey purifiers are easy to install and operate. For larger systems, onsite startup and training service is offered.
WHAT IS THE PRESSURE DROP ACROSS THE PURIFIERS?
When operating within normal parameters the pressure drop across a getter or catalytic bed is less than 1 atm. Pressure across the palladium membrane is required in order to drive the hydrogen across the palladium membrane. The larger the pressure drop the greater the flow and the smaller the palladium membrane size required, thus improving the economics. Refer to the Product Pages for access to pressure and flow curves for each product line.
WHY ARE THE CONTROL PANEL AND PURIFIER SEPARATED IN THE LARGER PALLADIUM MEMBRANE HYDROGEN PURIFIERS?
In palladium membrane hydrogen purifiers separating hydrogen components from electrical components is done to comply with codes and regulations for hydrogen safety.
SHOULD I CARRY SPARE PARTS FOR THE UNIT?
For HP Series palladium membrane hydrogen purifiers, a spare cell and/or spares of certain components are recommended if your system cannot tolerate downtime. Speak to your Johnson Matthey representative for more information on what components may be recommended for your unit. Spare getter and catalytic vessels are not required but are suggested for rapid replacement.
WHY ARE JOHNSON MATTHEY PALLADIUM PURIFIERS BETTER THAN OTHER TYPES OF HYDROGEN PURIFIERS?
Refer to the technical bulletin section of this web site for detailed information on the specific advantages of palladium purifiers.
I AM UNHAPPY WITH PURIFIERS FROM ANOTHER SUPPLIER, BUT I NEED THE SAME SIZE UNIT TO ALLOW DIRECT REPLACEMENT, CAN YOU HELP ME?
Absolutely, many of our purifiers use industry-standard dimensions to allow direct replacement. For other applications, Johnson Matthey will work to engineer a unit, or system, to fit your needs. | 
