Flue gas desulphurization

Flue gas desulfurization is commonly known as FGD and is the technology used for removing sulfur dioxide (SO2) from the exhaust combustion flue gases of power plants that burn coal or oil to produce steam for the turbines that drive their electricity generators.

1. Gajendra Singh (MSDIT/18/02) Department of Mechanical Engineering NIT, ARUNACHAL PRADESH Flue Gas Desulphurization

2. Introduction Coal 40.80% Natural Gas 21.60% Hydro 16.40% Nuclear 10.60% Oil 4.30 % Other 6.30 % Emission   Combustion of fossil fuels (e.g., coal and oil)   2014 World Electricity Generation Source : IEA Electricity Information 2016

3. Influence of Sulphur Oxides ( )   Decrease of Visibility Range Bad Influences on Green Plants Bad Influences on Human Body Destruction of Ecosystem

4. Air Pollution (TPP) – Current Regulation in India as per MoEF The data mentioned above is for TPPs (Thermal Power Plants) > 500 MW

5. How to Control Sulphur Oxides ( )   1. Fuel Desulphurization Process Method to remove in the fuel prior to combustion.   2. Flue Gas Desulphurization (FGD) Process Method to remove from emitted gas after combustion.  

6. Types of FGD Process Source : US EPA published fact sheet

7. Classification Based on Process Wet Semi-Dry Dry Characteristics Slurry or Solution  Slurry or Sol. Slurry or Solution  Dry Powder Dry Powder  Dry Powder Main Reactor Wet Scrubber Semi Dry Reactor Dry Injector Application Large / Medium Scale Medium / Small Scale Medium / Small Scale Removal Efficiency Waste water treatment Necessary unnecessary unnecessary Investment cost High Medium Low Operating Cost Low Medium High Wet Semi-Dry Dry Characteristics Slurry or Solution  Slurry or Sol. Slurry or Solution  Dry Powder Dry Powder  Dry Powder Main Reactor Wet Scrubber Semi Dry Reactor Dry Injector Application Large / Medium Scale Medium / Small Scale Medium / Small Scale Removal Efficiency Waste water treatment Necessary unnecessary unnecessary Investment cost High Medium Low Operating Cost Low Medium High

8. Classification Based on Chemicals Lime(Stone) Scrubbing Magnesium Scrubbing Sodium Scrubbing Ammonia Scrubbing Kind of Chemical Reactivity Low Medium High High Phase of Product (Solid) Gypsum (Slurry) (Solution) (Solid) Application Power Plant Small Power Plant Industrial Boiler Power Plant Removal Efficiency Waste water System Small Big Big Small Capital cost High Medium Low Highest Operating Cost Low Medium High Medium Lime(Stone) Scrubbing Magnesium Scrubbing Sodium Scrubbing Ammonia Scrubbing Kind of Chemical Reactivity Low Medium High High Phase of Product Application Power Plant Small Power Plant Industrial Boiler Power Plant Removal Efficiency Waste water System Small Big Big Small Capital cost High Medium Low Highest Operating Cost Low Medium High Medium

9. 1 . Dry Sorbent Injection Process Flue Gas Dry Absorbent Injector Mixing Section Reaction Chamber Additional Acid Gas Clean Air Filter Cake Collected Solid Particulates Recycled Absorbent Absorbent

10. 2 . Wet Limestone Gypsum Process Absorbent : Limestone Stoichiometric Ratio : 1.03-1.05 By Product : Gypsum   Chemical Reaction + + + +  

11. 2 . Wet Limestone Gypsum Process

12. 2 . Wet Limestone Gypsum Process : System Mass Balance Untreated Gas Oxidation Air M/E Wash Water Limestone FDG System T reated Gas Gypsum Cake Waste Water

13. 2 . Wet Limestone Gypsum Process Wet Absorber Types 1 . Spray Tower 2 . Venturi Scrubber 3 . Packed Tower or Trayed Tower Absorption Efficiency Depends upon 1 . Amount of Scrubbing Liquid 2 . The Size of Particles 3 . Velocity of Gas 4 . Contact Duration 5. Ration B/W Gas/ Liquid

14. However , emerging technologies have the potential to reduce SO2 and NOx emissions for less than the combined cost of conventional FGD for SO2 control and selective catalytic reduction (SCR ) for NOx control. fairly complex and costly . Most processes are in the development stage. some processes are commercially used on low to medium-sulphur coal-fired plants . Future Scope : Combined / Removal Process  

15. Flue gas desulfurization scrubbers have been applied to combustion units firing coal and oil that range in size from 5 MW to 1500 MW. Dry scrubbers and spray scrubbers have generally been applied to units smaller than 300 MW. The highest SO2 removal efficiencies (greater than 95%) are achieved by wet scrubbers and the lowest (less than 80%) by dry scrubbers. However, the newer designs for dry scrubbers are capable of achieving efficiencies in the order of 90%. Miscellaneous fact and statistic

16. Reference MoEF : Environmental Standards IEA Coal : FGD US EPA : Laboratory Analysis of FGD US EPA : Air Pollution Control Technology Fact Sheet IDC Technologies : FGD KC Cottrell : KC-Cottrell-India , Brochure_Gas_Treatment_Systems Siemens Environmental Systems & Services (SESS) : Flue-Gas-Brochure ANDRITZ

17. Thank you