Gas Purification Units for Glove boxes
Gas purification units are combined with glove boxes under controlled atmosphere. Generally, it implies an elimination of residual traces of oxygen (O2) and moisture (H2O) contained in an already pure gas, such as nitrogen (N2), argon (Ar) or a mixture with helium (He). For very specific applications, by passing the neutral gas over a heated titanium-based compound, it is also possible to remove traces of nitrogen (N2) in argon (Ar). Gas purification units are designed to remove traces in gases constituting the pure atmosphere of the glove box, and not as air purifiers.
When starting up an installation, it is necessary to evacuate the air contained in the glove box before starting the gas purification unit. This operation to remove the air from the glove box is often carried out by a neutral gas purge, also called “flushing” (flushing gas method).
Purification Unit Working Principle
The principle of a purification unit consists in continuously circulating, in a closed loop, the gas from the glove box through the purification unit. Once passed through the purification unit, the freshly purified gas is returned to the glove box. This permanent glove box-purification unit exchange allows a renewal of the glove box atmosphere that can be measured and controlled, and that constitutes the basis for maintaining a internal purity. Then, purification of the gas passing through the purification unit is essential to eliminate any micro-pollution effect in the glove box.
A well-dimensioned purification unit connected to a class 1 glove box (ISO 10648-2 standard) allows obtaining and maintaining of residual H2O and O2 contents at a very low level of purity, in a range of 0 to 5 ppm, but often at values in ppm or less.
Components of Purification Units
A purification unit includes certain components that are critical in the final performance: a stainless-steel purifier is the reactor in where two chemical species will allow the adsorption of oxygen and moisture from the carrier gas are located. A molecular sieve consisting of small zeolites to adsorb H2O and a granular copper catalyst to adsorb O2. A hermetic fan, the heart of the installation, allows the gas to circulate between the glove box and the purification unit.
A control box with a PLC (Programmable Logic Controller) ensures the automation of many operations, including pressure regulation that maintains the glove box at a pressure slightly above atmospheric pressure, but also the automatic regeneration of the purifier, which is similar to a reactivation of the purifier loads when they are saturated.
A color touch screen, connected to the control box and connected to all the sensors of the installation on where all the important data, H2O, O2, temperature, pressure values, but also graphs, alarms and other configurable operations are displayed continuously.
A whole set of stainless-steel piping and automated valves for the management of the purification circuit and whose characteristics are also important for the final quality.
Glove Boxes Equipped with Gas Purification Units
Glove boxes equipped with gas purification units are classified in a large “product protection” category, compared to another category of operator protection-oriented products. Both are not contradictory.
“Product protection” includes the use in the storage and use of compounds that cannot be handled in the open air due to their very high chemical reactivity, such as alkali metals or compounds based on transition metals. Some materials would lose their physical or chemical properties, as their surfaces may oxidize in air or degrade in the presence of moisture, while others, such as sodium, present very high pyrophoric risks simply by contact with humid air.
Because of their potential, purified glove boxes have quickly found increasing acceptance in many fields of research and industry. They are widely used in the fields of chemistry (synthesis, organometallic chemistry…), physics (ultra-high vacuum thin film deposition techniques…), biology in order to reproduce anaerobic atmospheres. In the industrial sector, purified glove boxes can be made with larger dimensions, real professional workstations in aeronautics, defense and space (additive manufacturing, titanium welding, encapsulation of electronic boxes …).
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