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Some safety aspects on the design of sparger systems for the oxidation of organic liquids



This article summarizes all important parameters for a proper and safe design of the sparger system for large bubble columns, used for the oxidation of organic liquids with air or oxygen enriched air. As an example, this is done for the oxidation of cumene (isopropylbenzene), which is worldwide used in phenol processes. Based on data in the literature and newly measured flammability limits at 100° C and 5 barg, the potential hazards from uncontrolled gas reactions can be avoided, ultimately avoiding an explosion in the sparger system. For normal operation, a minimum flow of gas is necessary to ensure a uniform flow through all outlets, which are typically holes with a diameter of several millimeters. All holes should be directed towards the vessel bottom to self-drain the sparger. For start-up, a previous inerting of the sparger with nitrogen is preferable. Nevertheless, a certain amount of organic liquid may still be in the sparger system prior to start up. Therefore, the compressed air/oxygen should have a temperature below the Oxidation Initiation Temperature to avoid any initiation of a liquid phase oxidation within the sparger. In addition, the pressure in the sparger system should be high enough to keep the gas phase concentration of the organic liquid below the Lower Flammability Limit. © 2006 American Institute of Chemical Engineers Process Saf Prog, 2006

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