It
is a known fact that pure oxygen is used in many chemical processes besides
industrial and medical applications. The oxygen enrichment for chemical
processes ranges from about 80% to 100%. Oxygen distributed to the chemical
processing industry is either generated cryogenically or generated by
pressure swing absorption and/or a vacuum-pressure adsorption method.
Different equipment are used in oxygen purity test which we are explaining
below:
Oxygen-sensing devices: Paramagnetic-type
Paramagnetic-type oxygen sensing devices are very popular equipment used
for measuring oxygen purity. These sensors are highly preferable because
they can produce highly accurate results, especially at the suppressed
ranges of 90% to 100% oxygen. But the drawback of such devices is that they
are expensive, and require extensive maintenance. Moreover, these sensors
are very sensitive to gas flow rate changes; to the presence of even small
amounts of fine particulates; and also to temperature, pressure, moisture,
and mechanical vibrations. Analyzers using these sensors require calibration
on almost a daily basis.
Micro-fuel cells
Besides the above, there are also low-cost, low-maintenance, and more
versatile tools to measure oxygen purity. Manufactures use the galvanic-type
micro-fuel cells, which are specific to oxygen and very simple to operate.
These devices have not been used to measure elevated levels of oxygen or
oxygen above 90% because their signal output drifts with time. A knowing of
the reasons for this drift needs a familiarity with the construction and
operation of a micro-fuel cell.
The basic components of a typical micro-fuel cell are shown below:
Under normal operating conditions, oxygen diffuses through a Teflon
membrane. Then the oxygen dissolves in a very thin layer of electrolyte
between the membrane and the sensing electrode. After this, the gas diffuses
to the sensing surface where it is reduced. Oxygen reduction is undertaken
by oxidation of an anode material, typically lead or cadmium. In other
words, in a micro-fuel cell, oxygen is reduced at the cathode. Thereby the
anode is simultaneously oxidized. The flow of electrons from the anode to
the cathode with the help of an external circuitry is related to the oxygen
concentration.
Purity
Testing of Oxygen
