Oxygen monitoring in reactor processes is essential for safety but presents challenges. Jason Byrne, Product Manager at Michell Instruments, compares some of the oxygen sensors that can be applied to this safety critical application.
Pharmaceuticals and speciality chemicals are typically produced in batches by mixing several components in a reactor. The reactors used vary in size from table-top glass jars to large stainless steel or glass-lined vessels with a mixer.
The ingredients within the reactor are often highly corrosive chlorinated compounds that, when mixed with solvents, can result in the void between the top of the reactor and the liquid level being filled with highly inflammable vapours. When combined with oxygen and a potential source of ignition (such as a static discharge, a spark generated by metal-on-metal contact or hot spots due to friction or mechanical wear) there can be a risk of explosion.
One way of ensuring that the mixture of air and solvent vapours stays below flammable levels is to use a nitrogen purge. In the past, operators would constantly feed nitrogen to the process and not worry about the oxygen level. However, nitrogen is a consumable with an associated cost and its use should be limited.
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