Scrubbing systems, process emissions

In the direct neutralization process, ammonia is distributed using a perforated pipe (sparger) positioned beneath the bed of material in the granulator. If sulfuric acid is used, it too is usually distributed through a sparger beneath the bed of material whereas the phosphoric acid, if used, is most often sprayed or dribbled on top of the bed of material. When sulfuric acid is used, precautions should be taken to ensure that the acid is added at a particular location with respect to the ammonia to ensure quick and uniform neutralization and thus minimize the unwanted reaction of sulfuric acid with muriate of potash (MOP) that is usually present in most NPK formulations. This acid/MOP reaction causes the formation of very corrosive hydrochloric acid, which reacts rapidly with ammonia to form a dense fume of ammonium chloride that is very difficult and costly to collect in the plant s emission control (scrubbing) system. 

The Alka/Sorb air pollution control system is designed to remove dioxin, furans, toxic metals, acid gases, and particulates from industrial and medical incinerator off-gas. The Alka/Sorb system consists of a dry treatment/wet scrubbing process during which incinerator off-gas is cooled, contacted with an alkaline powder, injected with a sorbent, filtered by a baghouse and then wet-scrubbed for final removal of trace acid gases. Two central parts of the Alka/Sorb system include a wet-acid scrubber and a patented sorbent called Diox-Blok, which prevents the formation of dioxins and furans in air emissions. 

The detrimental effects of acid rain are a major reason why legislation such as the Clean Air Act places strict limitations on sulfur and nitrogen emissions. It is also a reason why low sulfur coal is preferred over high sulfur coal. To reduce sulfur dioxide emissions, industry also uses a technique call scrubbing. Industrial scrubbers employ a variety of physical and chemical processes to remove sulfur dioxide from emissions. Another technique used to combat acidification of lakes is to treat these systems with lime. The lime acts to neutralize the acid, but such techniques are usually costly and are only a temporary remedy for combating the problem. 

---