Sulphur dioxide scrubbing from flue gas

In the scenario of flue gas treatment, sulfur dioxide is one of the dangerous compound if it increases in the atmosphere, it will change the Earth to become another Mars. Flue gas is treated to remove the sulphur dioxide by scrubbing operation. Using a low concentrated liquid alkali solution the sulphur dioxide is absorbed from the flue gas generated from steam generation plants and fossil fuel combustion industries. The model shown here is a preliminary form of design explains about the flow pattern of the process streams.

Important operations in process flowsheet:

  • A blower feeds flue gas to absorber through the quencher.
  • Soda ash in dilute form is sprayed on the packed bed system of absorber to remove the traces of sulphur dioxide from the flue gas.

Neutralization chemical reaction takes place during the contact of flue gas and scrubbing solution. SO2 scrubbing with sodium carbonate solution is done based on below reaction,

  • Na2CO3 + SO2  → Na2SO3 + CO2

The solid formed in the scrubbed solution are purged out in frequent intervals by blow out pump of the solution tank.

sulphur dioxide scrubbing system flow diagram

Sulphur dioxide removal from flue gas by scrubbing

 

 

 

 

 

 

 

 

In place of soda ash, gas expanded liquids and multi absorbent solution can be used in the above system. The operation remains same for any absorbing solvent when used in liquid state only. To make the process completely environmental friendly and make a model of green technology two important aspects must be included into the system.

  • Using solar planes that uses solar energy and give power to pump and blower motors.
  • Using organic adsorbent, means organic leaves grounded and made into solution that can absorb the SO2 gas by simple liquid-gas contact. This provides the facility to us the final solution as fertiliser that comes out of the scrubber mostly saturated with SO2 .

Business improvements in sulphur dioxide scrubbing process:

Supplier for the scrubbing unit have a demand in supplying absorption chemicals on monthly basis. This type of plant requires gaskets and maintenance materials during the periodic maintenance, by the corrosive nature of the chemicals the life of equipments decrease then the specification. This is why replacement of accessories is done as per safety rules. Even simple wetted wall column models can be setup with solvents like sodium chlorite absorption chemicals. Wetted wall column models have less maintains problems when compared to the packed scrubbing systems that face the scaling, clogging and choking during continuous running. This type of chemical absorbers not only removes SO2 but also they have capability to remove CO, NO and CO2 gas. This model can eliminate the old flue gas desulphurization and denitrification dry technique. SO2 removal efficiency of the wetted wall column highly depends on the pH of the solution. Due to the acidic nature of the pollutants, the pH value should be high for the absorbent. Even the molar ratio show significant effect on the column absorption capacity the higher the ratio the better the desulfurization takes place.

Research and development in sulphur dioxide scrubbing:

Important research is done now for the chemicals and in the design of the equipments to improve the performance and efficiency. Scrubber design is major concern for a researcher to develop a real time perfect system that needs less maintenance and remove SO2 completely.