The addition of the adsorbent takes place on the pneumatic way. The hydrated lime is taken out of a silo through a slide gate, a rotary valve and a screw conveyor. In an intermediate vessel the adsorbent will be weighted and blown into the ductwork. The dosing quantity can be adjusted by a frequency drive so that the necessary amount of adsorbent can be adapted.
Additive Dosing Systems can be placed under a Silo for smaller amounts of additive consumption. Additives can be Hydrated Lime (separation of HCL or HF), Activated Carbon (separation of dioxines) or a mixture of both (for small amount of dioxines).
![Addative Dosing red](/-/media/mikropul/addative1.jpg?h=248&w=300&la=en-us&rev=88af26a0b80f481a9740f630b62c5b37&hash=949D214094653BB64E48B072C886C4F8)
Different Additives
There are basically three different uses of additive:
- Chemical reaction / chemical reaction. - This mostly eliminates acidic pollutants, such as sulphurous acid (SO2), hydrochloric acid (HCl) or hydrofluoric acid (HF). Almost exclusively lime-based products are used here, such as hydrated Lime or Sodium Bicarbonate
- Adsorption for reducing of volatile hydrocarbons, dioxins and mercury -
Products such as activated carbon or hearth furnace coke are used. Disadvantage here is the explosiveness of these substances.
Mixture of carbohydrate and activated carbon may be employed, or a zeolite material, e.g. Minsorb.
These additives bind through a very porous structure (about 1000m² / g) the above mentioned substances.
There is no chemical reaction but a purely physical binding / adsorption.
- Binder used for oily exhaust air. -
Construction Lime or Stone Meal. Gives a protective layer for the filter bags made of needle felt or cartridges.
![Activated Carbon](/-/media/mikropul/activated-carbon.jpg?la=en-us&hash=CD89761D0BF61971434B43F2ABD9676C)
Sorption of acidic gases (often from thermal furnace processes)
All acids are chemically converted to salts.
These salts can be cleaned and disposed of in the filter system as a normal dust filtration process.
- Ca(OH)2 + 2HCl → CaCl2 + 2H2O - Calcium Chloride
- Ca(OH)2 + SO2 → CaSO3 + H2O - Calcium Sulphite
- CaSO3 · H2O + ½O2 + H2O → CaSO4 · 2H2O - further reaction to Calcium Sulphate dihydrate (gypsum)
- Ca(OH)2 + 2HF → CaF2 +2H2O - Calcium Fluoride
- Ca(OH)2 + CO2 → CaCO3 + H2O - Calcium Carbonate
Additive Dosing System Versions