Definition - What does Dry Scrubber mean?
Dry scrubbers are used in the removal of pollutants from emissions, such as exhaust gases and flue gas, by use of adsorption. It is a multiple- or a single-stage system used in the treatment of gas streams by controlling the amount of acidity, particles, toxins, metals and odors before releasing it into the atmosphere. This is eventually achieved by injecting a dry adsorbent or alkaline reagent.
It is used in boilers, incinerators and regenerator towers in industries that produce acidic gaseous emissions. The pollutants occur as:
- Sulfur oxides
- Nitrogen oxides
- Metallic compounds
- Organic compounds
The reason for the removal of these pollutants is the prevention of acidic rain, which can contribute to global warming and corrosion of surrounding metallic components.
Corrosionpedia explains Dry Scrubber
Dry scrubber technology uses the principle of absorption and adsorption to trap the pollutants from the stream of exhaust gases. The technology varies depending on the form of the alkaline reagent (lime and calcium carbonate) used and methods of how the gaseous emission comes into contact with the reagent; the time at which the reagent and the gas stream remains in contact is also considered.
The system goes through a monitoring process to ensure that the entire emission is free of the major pollutants. In most cases, the presence of fabric filters and electrostatic precipitators (ESP) indicate the use of dry scrubbers. The material of the vessels should be designed with strong metals to prevent corrosion.
The reagents are made into a thick liquid or can be used dry. The reagent is later injected or sprayed into the absorber vessel where it is expected to be in contact with the exhaust gas. In liquid form, the reagent is atomized so that more contact is achieved and absorption is maximized. The injected reagent is made to flow inside the adsorber vessel to improve the mixing of the reagent with the flue gas; the use of venturi or constriction is to increase contact and velocity. Further cleaning of the gas is done by the filters to remove suspended particles. In the end solid byproducts of the pollutants are collected at the base of the vessels and later disposed of