Sunday, June 18, 2017

Rigid Sided Anaerobic Glove Boxes - Theory of Design

Rigid anaerobic chamber glove box with airlock
Rigid construction anaerobic glove box with airlock
Courtesy Coy Lab Products
There are numerous threads of scientific research that require small environments with extremely low levels of oxygen. This anaerobic environment requires isolation from the surrounding atmosphere and a means to scavenge trace amounts of oxygen that inevitably get into the closed environment. It is also, in many cases, necessary to provide a means to transfer materials into and out of the chamber during use, as well as to allow operators to manipulate materials within the chamber.

One method applied to remove infiltrated oxygen is through the use of a catalyst within the chamber to react the oxygen with hydrogen, producing water vapor. This can be accomplished with a small fan enclosure that continuously or intermittently circulates chamber air across a palladium chloride coated alumina substrate. The palladium chloride supports the oxygen-hydrogen reaction, while the alumina substrate serves to absorb the water vapor. The fan must be properly sized and operated on a schedule that will treat the chamber atmosphere at a rate that is suitable for the application. Larger fan and catalyst combinations will produce larger turnover rates for the chamber atmosphere, along with faster recovery of anaerobic conditions.

For the movement of materials into and out of the work zone, an airlock is provided. The airlock enables isolation of the chamber interior work zone from the surrounding atmosphere and limits that amount of atmospheric air entering the chamber when materials are introduced to the anaerobic work zone. The capacity of the catalyst system is coordinated with the size of the airlock to provide rapid removal of the known quantity of oxygen introduced to the chamber each time the airlock is cycled.

Sealed glove ports provide an operator with the ability to hold and manipulate the contents of the chamber. Proper maintenance of the gloves and their mounting to the ports is essential to maintaining anaerobic conditions in the chamber. Because some degree of physical stress is placed on the glove mountings during normal use of the chamber, regular inspection of their seals is good practice.

Oxygen will diffuse into the chamber during normal operation. A source of hydrogen gas must be used to provide sufficient quantities to enable effective catalyst operation. A special gas mix can be used to purge the airlock that serves to reduce the oxygen level of the airlock and provides sufficient hydrogen to process the introduced oxygen, as well.

This is but a general description of how the system functions. Share your anaerobic process and research challenges with a product application specialist, combining your own process knowledge and experience with their product application expertise to develop the best solution for your application.

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