1. Combustion Products and Emission Controls CHE 450

2. Combustion C x H y +(x+0.25y)*(O 2 +3.76N 2 )=xCO 2 +0.5yH 2 O+3.76(x+0.25y)N 2 Ex: CH 4 + 2(O 2 + 3.76N 2 ) = CO 2 + 2H 2 O + 7.52 N 2

3. Combustion Pollutants Particulate Matter (PM) SOx NOx CO-usually not an issue with large, well- controlled power plants CO 2

5. PM Particulate Matter-very small diameter solids or liquids suspending in gases. (ash/soot/gas conversion). PM 10, PM 2.5 >10 um-nasal passage/mucus <0.1 um-bronchial tree/mucus 0.1<10 um-respiratory problems

6. PM – Gravity Settler/Cyclone – Fabric Filter/Baghouse – Electrostatic Precipitator – Wet scrubbing

7. Fabric Filter Shaker

8. Fabric Filter

10. ESP Use electric field to attract PM “Negative Corona” – Strong E-field generates high energy electrons – Electrons create ionized gas species – Ions are absorbed onto particles – Particles absorb onto plates

11. ESP

12. Advantages – High Efficiency – Low pressure drop – Low operating costs Disadvantages – High capital costs – Large – Not flexible to changes in operating conditions

13. Sulfur SO 2 (and some SO 3 ) is emitted SO 2 oxidized to SO 3 in atmosphere SO 3 + H 2 O = H 2 SO 4 = ACID RAIN

14. Sulfur Pre-combustion or post combustion Most common: limestone scrubbing CaCO 3(s) +H 2 O+2SO 2 = Ca 2+ +CO 2 + 2HSO 3 - CaCO 3(s) +2HSO 3 - +2Ca 2+ =2CaSO 3 +CO 2 +H 2 O

15. SOx Scrubbing

16. Nitrogen High Temps: NO, NO 2 formed 95% of stationary source NOx is NO Thermal NOx, Fuel NOx Brownish color In combination with VOCs, form O 3

17. Nitrogen O +N 2 →NO+N N+O 2 →NO+O N 2 +O 2 →2NO K~10 -3 @2500K

18. Nitrogen SCR=Selective Catalytic Reduction 300-400 ˚C ~80% effective 4NO + 4NH 3 + O 2 → 4N 2 + 6H 2 O 2NO 2 + 4NH 3 + O 2 → 3N 2 + 6H 2 O NO + NO 2 + 2NH 3 → 2N 2 + 3H 2 O

19. SCR

20. Carbon Capture and Storage

21. Capture Use temperature swing to absorb/desorb

22. Storage Reduces delivered electricity by at least 25%

24. The Thermodynamic System The System Contains some energy, E The Surroundings (i.e., the rest of the Universe…)

25. First Law – Conservation of Energy “energy can be converted from one form to another but cannot be created nor destroyed” 1 2 Q W

26. “Enthalpy” - H Enthalpy measures total energy of the system. Internal energy (energy required to create system) Energy required to make room for it by displacing its environment: function of volume and pressure

27. PV and work In general, work is given by PV P V 1 2 B A Question: is work done by path A same as by path B? Work done depends on path taken! d signifies an exact differential  signifies an inexact differential

28. Second Law – Quality of Energy Decreases “energy flows from a higher potential (higher quality) to lower potential” Q W High TLow T Q A couple other statements of this: Clausius: No process is possible whose sole result is the transfer of heat from a body of lower temperature to a body of higher temperature Kelvin: No process is possible in which the sole result is the absorption of heat from a reservoir and its complete conversion into work

29. “Entropy” - S Entropy measures “disorder” of the system. (“quality”) For a “reversible process” “reversible process” ≡ process that can be carried out and reversed without leaving traces on the surroundings

30. Reversible Systems For a reversible process involving heat transfer at T 0,

31. Irreversible Systems Clausius inequality: T S 1 2

32. Isentropic Compression Isothermal Expansion Isentropic Expansion Isothermal Compression http://en.wikipedia.org/wiki/Carnot_cycle Carnot Cycle

33. Heat Engine Want colder T cold and hotterT hot

34. Carnot Cycle Isothermal Expansion Isentropic Expansion Isothermal Compression Isentropic Compression http://en.wikipedia.org/wiki/Carnot_cycle

35. Brayton Cycle http://commons.wikimedia.org/wiki/File:Brayton_cycle.svg