Dry deacidification

The acid gases within the flue gas (SOx, HCl, HF) may be removed with the requested levels of efficiency through the dry injection of a low-granulometry basic solid reagent.


Generally, hydrated lime, sodium bicarbonate and sodium carbonate (soda ash) can be used. In modern, efficient plants, double injections of the same or different reagents may also be used.

The parameters that have to be managed to ensure an effective reaction are the so-called “3 Ts”: Temperature, Turbulence, and (Reaction) Time.


The choice of the most suitable reagent is based on an analysis of various different aspects:


– requested levels of efficiency


– type of acids to be broken down and relevant concentration ratio


– management of the residue


– reaction temperature


The reaction temperature can be adjusted through flue gas conditioning.


The reagent is normally injected by means of a pneumatic transport, either with a dosage and preparation system or with a static mixer inserted into a reactor or onto a flue gas duct.

On the basis of the distance to the de-dusting point, a decision can be taken on whether or not to insert a proper reaction chamber; the reaction can also take place on-line inside the ducts.


The dosing of the reagent may be carried out on the basis of volumetric weight. This can be managed manually, automatically with feedback adjustment, or – for feeder applications – with feed-forward support .

The recirculation of the byproducts of the reaction may, in certain cases, deliver notable advantages in terms of consumption.