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Industrial environmental issues Flue gas purification processes

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Presentation on theme: "Industrial environmental issues Flue gas purification processes"— Presentation transcript:

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

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