Continuous flow bubble column reactor for the photocatalytic causticisation of sodium oxalate

The photo-oxidative degradation of Na oxalate has been carried out in an ae rated bubble column reactor. Batch (liquid phase) rate data were adequately described by a Langmuir-Hinshelwood kinetic model based,sed on a dual-site mechanism. In view of the obvious advantages of a continuous liquid flow o peration on a commercial scale, experiments were conducted with co-current upward liquid and gas flows through the reactor. Whilst conversion decrease d with slurry flow rate as may be expected, increased gas Bow rate, however , improved conversion. In comparison to conventional multiphase reactor, th is is somewhat counterintuitive but may be explained in terms of better lig ht-harvesting characteristics - a factor irrelevant to traditional slurry r eactors - as increased gas velocity would lead to greater swirling motion a nd thus, longer particle residence time and/or solid recirculation, especia lly at low liquid flow rates which in turn permits greater UV exposure. For the present system, an optimum L:G ratio of 1 yielded a conversion of 75%. (C) 1999 Elsevier Science Ltd. All rights reserved.