Power fluidics SCRUBS PARTICULATES
15 Jan 2000
Increasingly, the process industries, and notably the pharmaceuticals industries, are adopting power fluidics to reduce particulate levels in process gases, writes Matthew Peach. The technique, originally devised by AEATechnology within the nuclear industry, is now scrubbing particulates from vent gases produced at companies as diverse as Smithkline Beecham, Zeneca, Glaxo Wellcome, Eli Lilly and ASTEC.
The technique is based on the gas-liquid contactor, a device that can give the same mass transfer performance as a traditional packed column but which is only a fifth of its volume, and has no need for packing.
Gas-liquid contactors can be used for a range of mass transfer operations including distillation, steam stripping and gas cleaning applications. They are often lighter and cheaper than conventional mass transfer equipment and are more resistant to fouling than packed columns, the company claims.
Gas to be cleaned enters the flat, circular chamber of the contactor through a series of vanes around the rim of the chamber. It moves inwards towards the outlet port on the central axis. As the rotating gas stream moves towards the central outlet, the tangential velocity increases to typically 15m/s. A radial diffuser on the outlet minimises the gas pressure drop.
Simultaneously, the liquid phase is sprayed into the centre of the chamber through opposing jets that creates a `sheet' of droplets which fly outwards towards the edge of the chamber. On contact with the gas the droplets remove suspended particulates and the scrubbed gas vents to the atmosphere. If one stage does not clean the gas enough several systems can be arranged in series. Powder fluidics, claims AEAT is suited to handling process streams with solids or those which are prone to crystallisation. The gas vortex and liquid sprays created by the tangential and radial flows produce a `self cleaning mechanism' and eliminate stagnation zones.
AEA TECHNOLOGY ENTER 291
