1. Industrial environmental issues Flue gas purification processes
Theme 4
Industrial environmental issues
Flue gas purification processes

2. Schedule for Theme 4 Monday 25/11, 08.15 -- 10.00 (DC:Lhö):
Lecture on “Flue Gas Cleaning” (Hans)
Tuesday 26/11, (Hall C):
Lecture on “Gas-Liquid Reactions” (Hans)
Wednesday 27/11, (Hall C):
Lecture on “Absorber design” (Hans)
Wednesday 27/11, (Seminar room L):
Exercises demonstrated on whiteboard (Hans)
Note: Disregard Tasks 4.1 and 4.2
Presentation of compulsory task 4 (Anders)
Thursday 28/11, (Seminar room L):
Try yourself, examination exercise 4.5 (Hans)
Friday 30/11, (Seminar room M):
Work with compulsory task (Anders)

3. Hand-outs for Theme 4 PPT material on Flue gas cleaning
Absorption with chemical reaction
PPT material
Gas-Liquid Reactions (mini-compendium)
Absorber Design (mini-compendium)
Solutions to exercises
Text description of compulsory task 4

4. Flue gas cleaning
Removal of gaseous and particulate polutants from flue gases generated by stationary combustion plants
Coal or oil fired power plants
Gas turbines
Soda boilers
Biomass fired heating plants
Waste fired combustion plants
Flue gas cleaning is only one of generic technologies for emissions control

5. Proclamation in 1276
”Whosoever shall be found guilty of burning coal, shall suffer the loss of his head”
King Edward I

6. Roster (moving grate) boiler

7. “Plug-flow” boiler (PB)

8. Atomspheric fluidized bed (AFBC)

9. Circulating fluidized bed (CFBC)

10. Pressurized fluidized bed (PFBC)

11. Exampel of different cleaning technologies

12. Generic problems
Combustion plants are not classified as traditional process industry
Flue gas cleaning plants are based on technology emerged from the process industry
Utility companies require simple technology, the process industry uses complex technology but cheap feed-stocks
The utility industry requires 25 years of capital depreciation, the process industry 10 years at the most

13. Flue gas content Inert components Toxic components Acidic species
Nitrogen, water and oxygen
Toxic components
Fly ash, trace metals, hydrocarbons, dioxines and POM
Acidic species
Sulfur oxides (SO2, SO3), nitrogen oxides (NO, NO2) and halogen acids (HCl, HF, HBr)
Greenhouse gases
Carbon dioxide (CO2) and laughing gas (N2O)

14. Decision tree for emissions control

15. Feed-stocks and products
Principle:
Pollutant + Reagent  Product
Problem
Cost of reagent
Secondary pollutants
Alternatives:
Reagent
Throwaway
Useful by-product
Becomes inert
Recycled
No reagent
Pollutant

16. Residual products Residual products might contain Waste-water
Solid waste
Sludge
By-products
Residual products might contain
Ash
Sulfur species
Nitrogen species
Chlorides
Heavy metals
Traces of organics

17. Removal of particulates
PRINCIPAL SOURCES OF PARTICULATES
Ashes from the fuel
Minerals, un-combusted, trace elements
Bottom ash
Fly ash
Reagents and products
Calcium compounds, etc.
Generic removal principles
Cyclones
Wet scrubbers/Absorption towers
Electrostatic precipitators
Baghouse filters

18. Trace metals
Content of trace metals in waste product from desulfurization process based on spray drying. Major constituents are calcium sulfite and fly ash.

19. Cyclones for particulate removal

20. Electrostatic precipitators

21. ESP Unit

22. Baghouse filter

23. Flue-gas desulfurization
The Wellman-Lord Process
Sulfuric acid, elemental sulfur or sulfur dioxide
The Walter Process
Ammonium sulfate
The activated coke
Sulfuric acid
Spray-Dry Scrubbing (Wet-Dry Scrubbing)
Dry calcium sulfite
Dry injection
Mixed product containing calcium sulfite
Wet FGD
Gypsum or sludge of calcium sulfite

24. Spray-Dry Scubbing Spray-drying of a lime slurry
Ca(OH)2 + SO2 F CaSO3 + H2O

25. Wet Flue Gas desulfurization Process
Typical Process schematic

26. Wet Flue-Gas Desulfurization (WFGD)
The process is based on a slurry of slaked lime
Ca(OH)2 + SO2  CaSO3 + H2O or
Limestone
CaCO3 + SO2  CaSO3 + CO2
Oxidation may occur
CaSO3 + ½ O2  CaSO4
Limestone is a mineral that has to be ground, lime is obtained by calcination (heat requirement) of limestone and slaked by the use of water
CaCO3  CaO + CO2
CaO + H2O  Ca(OH)2
Presently, the cost determines how reagent is selected!!!!

27. Schematic reaction mechanism
Absorption step
SO2 + H2O  HSO3- + H+
H+ + SO32-  HSO3-
Limestone dissolution
CaCO3 + 2H+  Ca2+ + H2O + CO2
Oxidation
SO32- + ½ O2  SO42-
Precipitation
Ca2+ + SO32-  CaSO3
Ca2+ + SO42-  CaSO4

28. Important design considerations
Oxidation or not?
Natural oxidation
Forced oxidation
Inhibited oxidation
Important parameters
Removal efficiency
Scrubber design
Limestone grinding
Process chemistry and pH
Additives
Scaling (incrust formation)
Degree of oxidation
Corrosion pH
Materials of construction
Chloride content
Cost
Scrubber size
Energy consumption

29. Additives and auxillaries
Adipic acid
Magnesium ion
Thiosulfate or elemental sulfur
Sodium salts
Auxillary equipment
Pre-quencher
Demister/Mist eliminator
Reheater
Grinder
Sludge treater
Thickener
Filter system

30. The FLOWPAC System

31. The FLOWPAC Reactor

32. The Karlshamn Plant

33. Flue Gas Denitrification
Nitogen oxides coinsist of 95% NO and 5% NO2 from combustion processes. Fluidized beds might generate some N2O
The generic problem: NO has a low solubility and is not very reactive.
Wet methods
Potasium permanganate
Sodium chlorite
Iron- EDTA
Oxidation-Absorption
Pre-oxidation of NO to NO2 using ozone or chlorine dioxid
Dry processes
The cupper oxide process
Alkalized alumina
Electron beam
Selective non-catalytic oxidation
Selective catalytic oxidation

34. SCR Design

35. How to operate an SCR

36. Carbon capture Pressure swing adsorption Scrubbing with water
Chilled ammonia absorption
Absorption in aqueous amine systems
Leading system: MDEA and Piperazine
CO2 + A*H2O  HCO3- + AH+

37. PSA for a biogas plant

38. The Chilled ammonia process

39. Wet Amine based CO2 absorption

40. Integrated systems

41. Prescrubber and absorber

42. The NID System

43. SYSAV Flue gas cleaning