Aerobic oxidation reactions present unique process safety challenges.  In order to obtain reasonable oxidation rates it's usually necessary to operate in flammable solvents with oxygen concentrations near the limiting oxygen concentration (LOC) for combustion, and at elevated temperatures and pressures.  This presents a process design challenge, especially given the fact LOC values at elevated temperature and pressure are only publicly available for a limited number of solvents.A fuel-oxidizer mixture is capable of combustion if there is sufficient fuel, oxidizer, and ignition energy (i.e., if the fire triangle is satisfied).  In the chemical process industries the elimination of oxygen is typically the basis of safety.  For aerobic oxidation reactions, selection of a safe oxygen concentration range requires measurement or estimation of the LOC under planned processing conditions, as well as application of an appropriate safety margin.  Elimination of ignition sources alone is rarely considered an adequate basis of safety.  This is especially true when operating at extreme conditions when Minimum Ignition Energies (MIEs) are lower and reliable prevention of ignition sources becomes exceedingly difficult.  Operating below the Lower Flammability Limit (LFL) for the fuel is another strategy that can sometimes be used.  LFLs are also a function of temperature and pressure.If it's necessary to operate above the LOC and LFL, it's also necessary to assume ignition is possible.  The equipment set (or bunker if used) would need to be designed to contain the explosion.This presentation covers the effect of temperature and pressure on LOC, MIE, and LFL values, and protection measures that can be taken to minimize consequences in the event of ignition.

Safety considerations for aerobic oxidation reactions at elevated temperature and pressure

246th National Meeting (2013)

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