Oil Degassing

Electrical and thermal stresses can degrade dielectric oil contained in electrical current transformers, evolving a range of 'fault gases', including hydrogen, methane, ethane, ethylene, acetylene, carbon monoxide and carbon dioxide. Air and water may be present as well.  Monitoring and detection of these gases in dielectric oil (U.S. Patent #6,217,634) can result in cost-effective “condition-based maintenance” of ailing yet operating electric power transformers, circuit breakers and load tap changers.  Early detection and subsequent monitoring of developing faults has been shown to prevent catastrophic failure of critical power system components, especially very large power transformers.

CMS membrane contactors have been demonstrated to degas napthenic oils (e.g. Shell Diala A & AX) at temperatures as high as 100°C.  This capability has allowed the development of commercial gas detection systems for on-site monitoring of dissolved fault gases in real time. 

Conventional microporous membranes, including those of polypropylene and polytetrafluoroethylene, will rapidly wet-out and lose performance when used to degas oils and other low surface tension liquids.

Certain polymer production processes require deoxygenated liquids to avoid poisoning of catalysts.  Propylene, hexene, octene, butene, benzene and styrene are all examples of monomers requiring degassing to ≤1 ppm prior to polymerization.  In particular, deoxygenation is required to avoid poisoning of downstream catalysts and corrosion of process equipment and piping.  The typical degassing process now is energy intensive, and involves heating the stream and flowing it through a column to degas it, then cooling it again prior to use.

CMS membrane contactors may offer improved performance and value over other convention unit operations for degassing certain feedstocks.  Potential applications may include absorption and gas stripping processes currently performed by spray, tray bubble and packed towers, venturi injectors and wet scrubbers, distillation columns, and falling film/wetted wall reactors.

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