The art of candle filter wetting

When candle filter mist eliminators installed in the absorption towers in sulphuric acid plants are not sufficiently wet, problems can occur such as free SO3 at the stack, NOx issues and emission non-compliance. Craig Cassells of Begg Cousland Envirotec discusses how these problems can be overcome by the installation of an annular wetting ring solution.

Candle filter mist eliminators are used widely in the sulphuric acid industry across the world. Located in the absorption towers as well as drying towers, they play a pivotal role in reducing air pollution as well as operational problems caused by the formation of sulphuric acid mists. Their successful operation is vital for achieving a plant’s operational capacity, protecting downstream equipment, and reducing the need for stoppages and maintenance interventions.

Fig. 1 shows a typical hanging type candle arrangement in an intermediate or final absorption tower.