Strong Acid System - Mist Eliminators - Impaction Candles
July 28, 2003

Introduction

Impaction type devices rely on inertial impaction and interception as the mechanism for mist collection.  The collection and removal efficiency of impaction devices are higer than mesh pads but lower than Brownian diffusion type mist eliminators.

Impaction type devices are generally constructed in a cylindrical forn commonly referred to a candle element.  Extremely fine glass fibres are packed or wound around an inner metal wire cage to the required density and thickness.   An outer metal wire cage serves to keep the fibre bed in place.  A typical installation will consist of multiple elements mounted on a tubesheet either in the hanging or standing position.

Damaged Candles

Candles are generally robust pieces of equipment and are not easily damaged.  They are subject to corrosion which can weaken the cages and lead to failures.  The following photos shows an unusual failure of a candle.  Top cover of the candle has been completely blown off.  The cause in this case was probably a defect in the fabrication of the candle since it has only affect one element.  The damaged element would have had the effect of completely bypassing the mist eliminator elements resulting in high carry over into the downstream equipment.