ECS_NB2

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Anonymous
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78711
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ECS_NB2
Updated:
2011-04-10 20:53:00
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Energy conversion systems
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Engineering energy conversion systems
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  1. What are the four types of pulverized coal plants?
    • Wet bottom (slagging T>Tmelt ash)
    • Dry bottom ( >85% fly ash)
    • Front Fired
    • Tangental Fired
  2. Give the steps in pulverized coal firing.
    • Coal -> Crushed -> Screen -> Pulverized -> Burner -> Ash
    • 0.3-0.4m <10mm <74micron air^
  3. Rank fuels on volumetric heat release rate (High to Low)
    Gasoline, Oil, Anthracite, Bituminous, Lignite, Biomass
  4. Rank fuels on capacity required (high to low)
    Lignite, High VOC Bituminous, Medium Bituminous
  5. Rank fuels on Height to pipes distance.
    Anthracite, Bituminous, Oil
  6. What effect does capacity and temperature have on grate heat rate?
    As both increase heat rate increases.
  7. How do you convert to steam boiler capacity?
    t/h(steam) = 0.75 MWth heat input
  8. Give three characteristics of Fluidized Bed Boilers
    • 1) Fuel burns in fluidized suspension of inert particles.
    • 2) Combustion zone is kept low by extracting heat directly from combustion zone.
    • 3) Exceptionally high degree of heating.
  9. What is the difference between FB and other boilers?
    Difference lies in how the gas and solids move around in the furnace.
  10. What are the main advantages of FB boilers?
    • 1) Low emission of SO2 and NOx
    • 2) Very fuel flexible
    • 3) Easy to operate and stable
    • 4) Lower maintenance
    • 5) Cost less than PC for lignite fuels
    • 6) Cost less than PC if FGD and SCR is required?

    **Note FB has a higher N20 (GHG) emssion than PC.
  11. What are the two main types of FB?
    • 1) Bubbling - Low Speed (1-2m/s), 10mm dp
    • 2) Circulating - High speed (4.5-5.5m/s), 6mm dp
  12. What kind of fuel can FB IDEALLY burn?
    FB can burn any fuel that has energy sufficient to raise itself and combustion gas above its ignition temperature.
  13. Why is FB insensitive to quality of fuel (2)?
    • 1) Large thermal inertia allows most fuels to be heated to ignition without losing too much heat from the boiler.
    • 2) Mixing makes it possible to dissipate the released heat and fresh fuel particles around the bed for easy ignition.
  14. Why is FB low acid rain emissions (2)?
    • 1) Low combustion temp allows limestone to capture Sulfur in combustion zone.
    • 2) Low temp and stagged air does not allow nitrogen to form NOx.
  15. Rank fuels on volumetric heat release rate (High to Low)
    Gasoline, Oil, Anthracite, Bituminous, Lignite, Biomass
  16. Rank fuels on capacity required (high to low)
    Lignite, High VOC Bituminous, Medium Bituminous
  17. Rank fuels on Height to pipes distance.
    Anthracite, Bituminous, Oil
  18. What effect does capacity and temperature have on grate heat rate?
    As both increase heat rate increases.
  19. How do you convert to steam boiler capacity?
    t/h(steam) = 0.75 MWth heat input
  20. Give three characteristics of Fluidized Bed Boilers
    • 1) Fuel burns in fluidized suspension of inert particles.
    • 2) Combustion zone is kept low by extracting heat directly from combustion zone.
    • 3) Exceptionally high degree of heating.
  21. How does circulating fluidized bed boiler work (2)?
    • 1) CFD Loop of solids
    • 2) Convection loop of gas
  22. Give the steps to operate a FB boiler (4).
    • 1) Preheat bed solids
    • 2) Let T increase until > Tign
    • 3) Extract heat
    • Water tubes in bed
    • Regulating air passing through bed
    • 4) Ash either stays in bed or entrained as fly ash.
  23. Give 3 advantages to keeping FB temperature low.
    • 1) Avoid melting or agglomerating bed solids
    • 2) Reduction of NOx
    • 3) Allows for Sulfur removal.
  24. What are the FB rules of thumb (6)?
    • 1) A = Vgas/Uf
    • 2) Hb = 0.4 - 1.5m (Hb = 0.7Uf - Gives residence time of 0.7s)
    • 3) Dp ~ 0.75mm
    • 4) Uf = 2.5Umf
    • 5) Qgrate = 3.3*Uf|300k/excess air (1.2 = 20% excess) (Mw/m2)
    • 6) About 2.908 MJ/kg heat is generated when 1kg of dry air is consumed.
  25. What temp and pressure do super critical boilers work above?
    • P>220.9 bar
    • T>374.3 C

    **Efficiency increases with both temperature and pressure.
  26. What are advantages of Super Critical Boiler?
    • 1) High efficiency
    • 2) Lower emissions
    • 3) Lower cost
    • i) Once through is simpler
    • ii) No drum
    • iii) Smaller diameter tubes
  27. Give 3 reasons why CFB is better than PC for SCB?
    • 1) For CFB highest heat flux region is in the water heating section.
    • 2) For PC highest heat flux is near water-steam transition region.
    • 3) Highest heat flux is much higher than average in PC.
    • 4) Much more uniform heat distribution
  28. In a gas turbine what happens to efficiency as pressure ratio increase?
    It increases in a logarithmic fashion.
  29. What two types of gasification are used for IGCC?
    • 1) Air blown - 0.5 heating value of O2 blown
    • 2) Oxygen blown - Much better for CO2 capture as flue gas is only CO2 and H2O
  30. What are benefits of IGCC (4)?
    • 1) Low emissions
    • 2) High efficiency
    • 3) Best for CO2 capture
    • 4) Can produce H2
  31. Give some barriers to IGCC deployment.
    • 1) PC can meet current standards
    • 2) IGCC financing costs are higher
    • 3) No reward for risk taking
    • 4) Bottle neck construction
    • 5) More project planning
  32. Rank types of gas turbine cycles by efficiency.
    • Simple cycle (36.4%)
    • Combined cycle (52.7%)
    • Co generation cycle (85.1%)
    • Combined cycle with Cogen (89.3%)
  33. What are some ways to meet zero emission technology?
    • 1) In-situ carbon capture (oxygen firing and chemical looping)
    • 2) Gasification systems (e.g. IGGC)
  34. What was the US zero emission project?
    • Futuregen
    • Annouced by bush in 2003
    • in 2007 Mattoon Township
    • in 2009 funding was pulled
  35. What are some benefits for vertical axle wind turbines?
    • 1) Independent of wind direction
    • 2) Low rotational speed (Torque up, Power down)
    • 3) Mechanical components are on ground level for easy access.
    • 4) Expensive tower is not required.
  36. What is the betz limit?
    • 0.5926
    • Theoretical maximum efficiency
  37. What is the ideal tip speed ratio for 2 and 4 blades?
    • 2 blades (5)
    • 4 blades (3)

    **Efficiency increase with number of blades but noise increase with tip speed ^5
  38. What are the components of the wind turbine?
    • Hub height - Height to middle of props
    • Blade
    • Gearbox and generator - Found in hub
    • Swept blade area
    • tower
  39. What are general cut in and out speeds?
    • Cut in 7-10mph
    • Cut out 45-80mph
    • Rate speed 25-35mph (where design power is found)
  40. What are the parts of a hydro turbine?
    • 1) Spillway - Release water downstream that is not used to make energy
    • 2) Penstock - Collects water from upstream leading it to turbine
    • 3) Draft tube - Passage directly below turbine
    • 4) Tailrace - Passage from draft tube downstream
    • 5) Surge tank - Reservoir that vents sudden pressure build up if required.
    • 6) Intake - Leads to the penstock
    • 7) Reservoir - Upstream water source
  41. What are the types of turbines?
    • 1) Reaction (Static pressure changes)
    • Converts both flow and kinetic energy
    • Axial flow - Kaplan
    • Radial or mixed flow - Francis
    • 2) Impulse (Static pressure is constant)
    • Converts only kinetic energy
    • Tangental bucket flow - Pelton
  42. What is Kaplan used for?
    • 1) Very low head
    • 2) High volume flow
  43. For differnt turbines what are the specific speeds (non-dimensional)?
    • Axial Flow 7-14
    • Mixed flow (Francis) 3.5-7
    • Centrifugal or radial flow (Francis) 1-3.5
    • Impulse (Pelton) 0-1
  44. Random facts about micro-hydro.
    • 1) Typically produce up to 100kw power
    • 2) 2000MW installed in Canada
    • 3) 40 in NS supplying 11% of provincial capacity
  45. What are the things that must be taken into account in LCA?
    Material extraction, Material Production, Product manufacture, Distribution, Retail, Use, Disposal

    **There is also transportation throughout
  46. What are the steps of LCA?
    • 1) Goal and scope definition
    • 2) Inventory analysis
    • 3) Impact assessment
  47. What are the applications of LCA for companies?
    • 1) Product development and improvement. (Product comparison)
    • 2) Strategic planning (Product assessment)
    • 3) Public policy making
    • 4) Marketing (Eco-Labeling)
  48. What are the applications of LCA for comsumers?
    • 1) Product comparison
    • 2) Product assement
    • 3) Eco-labeling
  49. What are some global warming potentials?
    • CH4 - 25
    • N2O - 298
    • HFC - 124-12800
    • PFC 7000-12000

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