Effectively removes pollutants from gases with dry sorbent injection systems.

Dry Sorbent Injection Systems (DSI systems) are a perfect solution in the control of pollutant gas emissions in industrial processes. These systems stand out for their ability to effectively reduce emissions of acid gases (SOx, HCl, HF), heavy metals, dioxins and furans among others.

In essence, a DSI system works by the absorption method, where dry sorbents are introduced into the flue gas, reacting with the pollutants and neutralising them before they are released into the atmosphere. This method is widely known for its versatility and effectiveness in reducing harmful emissions.

As mentioned above, the operating principle of DSI systems is to inject a suitable dry sorbent for the pollutants present in the gas stream which will mix and absorb the pollutants to discharge the clean gases into the atmosphere.

In order to maximise collection efficiency and thereby reduce the operating costs of the system, the installation must be designed and dimensioned correctly. The different processes and equipment that make up a DSI installation are specified below:

• Reagent dosing:
  The reagents must be correctly selected according to the pollutants present in the gases. Normally salts such as calcium hydroxide (Ca(OH)2 or sodium bicarbonate (NaHCO3) are used to treat acid gases, while activated carbon is used to capture heavy metals, furans and dioxins.
  Depending on the consumption ratios, these absorbents are stored in silos or big bags and are dosed by means of a controlled dosing system according to the amount of pollutants present in the gas stream. Accurate dosing is essential to ensure an efficient chemical reaction as well as to control operating costs.
  
  

• Reactor:
  In order to be able to mix correctly and to give a reaction time between the absorbents and the pollutants, the gases with the absorbents are introduced into a reactor, where part of the chemical reaction takes place.
  
  

• Dust Collector:
  After the reactor, the gases with the absorbents pass through a dust collector where the chemical reaction is completed, particles such as ash or process dust and the reacted absorbent are filtered out and discharged through the discharge elements of the filter. At the same time the gas leaves the clean air chamber free of dust and pollutants and is directed into the chimney.
  
  

• Recirculation:
  As the absorbent has a very high absorption capacity, it is useful to offer recirculation of the absorbent in cases where the absorbent consumption is estimated to be very high. Recirculation works by sending part of the product discharged through the filter back to the reactor injection point, while another part of the discharged product is considered as reject and is normally sent to the reject silo.
  
  

• Rejection:
  The material collected by the filter that is not recirculated is considered as reject. Depending on the type of absorbent and its composition, it can be recycled after use by a waste manager.
  
  

• Control system:
  In order to control absorbent consumption and check stack emissions, a CEMS (continuous emission monitoring system) unit measures the pollutants indicated to adjust the absorbent dosage rate.