It s the coal Rod Hatt

Transcription

1 It s the coal Rod Hatt [email protected]

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6 Gas Coal Molecular Structure

7 CAPP is easiest coal to use: Easy to Low NOx Little to no Slag Little to no Corrosion Easy on Operators

8 NAPP is easier coal to use: High Btu High HGI Grind Low ash =Less Slag Can be Easy Operators

9 PRB Coal: Handling Issues Low Sulfur Good Low NOX Slagging & Fouling Low Btu/Low Price

10 Illinois Basin: Plant Operators have to stay on top of their game Not low NOX friendly Slagging & Fouling Best Value

11 Measuring Coal Quality Power plant operators rarely get CQ info Coal Sales Data Actual ASTM Analyses On-Line information Lots of Confusion Major impacts Design and Operation of plant

12 Measuring Coal Quality ASTM only produces average data Power plants respond to swings in quality

13 60 Pure Coal Analyses Ash What is Easy to sell What causes plant problems

14 Lowest cost coal is always raw.

15 Small and Large Variability ASTM reports same ash level

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18 Plant Limit Average Does this coal met spec?

19 Slag potential of fuel

20 Washed Coal is: More Consistent Little to no OSD (rocks) Typically Lower Fusion

21 Self Heating Temp Bituminous A, B = Low Bituminous C Sub Bituminous = Medium = High Gillette PRB = Very High

22 Pulverizers Dry and Grind More Moisture - Lower Outlet Temp Lower Kg/Kcal - Higher Tonnage Rate - Higher PA Flow 22

23 Moisture sensitive only three values High, Medium, Low

24 Mill Capacity And HGI

25 Sizing Set for Coal type Set for Slag control May be opposite directions 25

26 Ash Wears Them Out Impacts load High Maintenance Performance Testing Most miners I know will sell you rocks at the price of coal. rmh

27 Raask Quartz %Quartz ~ SiO 2 1.5x Al 2 O 3 % Quartz X Kg ash/mkcal = Kg Quartz per Million Kcals

28 Mill Outlet Temperature Usually lower with ILB coals verses CAPP and NAPP Typically o F.

29 Bituminous Coal Combustion 1.Maintain 70% passing 200 mesh screen 2.High Calorific Value and low moisture allow for low mill loading 3.Lower Primary Air due to lower coal flow can allow for rejects 29

30 Bit Coal Combustion 30

31 Coal Combustion Sub - Bituminous 1.Maintain 60-70% passing 200 mesh screen to increase though put. 2.Low Calorific Value and high moisture make for high mill loading 3.High Primary Air for drying and high coal flow sends reject material into the furnace 31

32 Sub-Bit Coal Combustion 32

33 Coal Combustion Sub - Bituminous 1.Hence sub-bit coal. 2.Low Calorific Value and high moisture make for high mill loading 3.High Primary Air for drying and high coal flow sends reject material into the furnace 33

34 Coal Combustion 34

35 Coal Combustion 35

36 Coal Combustion 36

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38 Causes Fuel Related Pyrite Clays Alluminosilicates Organic Alkalis

39 Causes Equipment Soot Blowers Pulverizers Air to Fuel Ratio Burners Changes

40 Causes Design Furnace Size Tube Material/Spacing Soot Blower Coverage Observe/Measure Slag

41 The Many Faces of Slag Kansas Style Washington State Style Ohio Style Texas Style

42 Common Denominator? Not the Coal Not Sulfur or Minerals Not the Boiler Not the Company Low NOx Burners Over Fire Air

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44 Most Slag Starts on walls

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46 Waterwall deposits force heat to convection pass.

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48 FeS2

49 Coal Combustion Chemistry Sulfur 101 or why rocket scientists have it easy Member: American Society of Mechanical Engineers American Chemical Society Society for Mining, Metallurgy, and Exploration North Carolina Coal Institute Contacts: sponsor

50 Sulfur in Coal Bad to the bone Slag Fouling deposits Pluggage Corrosion Pollution Money $

51 All coal has sulfur It comes from sea water vs. fresh water environment

52 Sulfur in Coal Coal typically is 0.3 to 4.0% Sulfur

53 Sulfur can be in two main forms: Organic Pyritic

54 Organic H-C-C-S-C-C-H sulfur is attached to coal carbon

55 Pyritic FeS 2 sulfur is attached to iron in fool s gold

56 FeS2

57 Large sulfur balls can be washed out or rejected by pulverizers Small framboids (raspberries) of pyrite are mixed in with the coal 50 microns

58 Cleat pyrite has to be ground up

59 Chemistry Issues FeS 2 High Sulfur Coal Low NOx Poor Fineness H 2 S + FeO Corrosion and Slag

60 Fusion Spread Ox-Red Iron Level delta Temp

61 Role of Iron Acid Base Fe2O3 Oxidized FeO Fe3O4 Reduced Good Poor

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63 Slag is a build up of rate process so, the amount of ash should matter.

64 Lbs. of ash/mbtu = %ash / (Btu/10,000)

65 Lbs. of element/mbtu = %ash / (Btu/10,000) X (%Element/100)

66 Many slagging concerns have been addressed using Ash Loading and Elemental loading levels; especially Fe 2 O 3, CaO, Na 2 O

67 Common Denominator? Not the Coal Not Sulfur or Minerals Not the Boiler Not the Company Low NOx Burners Over Fire Air

68 With low NOx Waterwall Corrosion Tube Leaks

69 Slag Related to: Coal Quality Getting Worse? Plant Equipment Boiler/Mills Fixed Combustion Process - NOx and Air distribution Superior Mill Performance Maintain Mills to Preserve BOILER

70 FeS2

71 Chlorine waterwall corrosion issues are minimal in oxidizing atmosphere (not lowest NOX) First 200 years of use Oxidizing atmosphere also Minimizes pyrite related corrosion Minimizes slag (raises ash fusion temperatures degrees)

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74 Coal Combustion 74

75 Pulverizers 70 % passing a 200 mesh screen Minimum or Maximum? Old School! Need 75% for high pyrite low NOx

76 POST MORTUM Microscopic Investigation of Deposits

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80 CaO + SO3 = CaSO4 Think Fluid Bed Boiler & Fouling Deposits

81 What does the SO3 represent? SO3 CaO

82 Organically Bound Alkalis COAL -O- -O- -O-

83 Sodium Condenses on Surface

84 Causing a Molten Layer on Surface

85 Fouling Index = B/A x Na2O works on ILB

86 Iron, Fe2O3 Calcium, CaO Sodium, Na2O are the glues

87 Chemistry Issues Sulfur & FeS 2 SO 2 + SO 3 SO 3 + NH3 Air Heater Pluggage

88 Choke Point

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90 SO2 to SO3 Conversion is excess oxygen sensitive

91 Sulfur burns to SO 2 Then some SO 2 burns Fe 2 O 3 pyrite, boiler, slag SO 2 + ½ O 2 SO 3 V 2 O 5 Oil, Petcoke, SCR

92 More Reactants? Sulfur in Coal --- SO2 Excess Oxygen (helps slag) More catalyst? Pyrite FeS 2 Slag Fe 3 O 4, Fe 2 O 3 SCR Vanadium V 2 O 5 in fuel

93 SO 3 Zone

94 SO 3 Zone H 2 SO 4 Zone

95 Fouling Deposits Think Fluid Bed Boiler CaO + SO 3 = CaSO 4 PRB convection pass fouling and it can be harder to measure SO3 with high alkalis (Na, K) and alkaline earths (Mg, Ca) in coal

96 After the economizer SO 3 combines with H 2 O SO3 + H 2 O H 2 SO 4 to form sulfuric acid

97 thanks Cal

98 H 2 SO 4 combines with all sorts of stuff to plug, foul, corrode and then it can leave the stack and form a visible plume of smoke sulfuric acid mist SAM

99 Industry Examples Walhco SO 3 Orimulsion Cold End Corrosion

100 Chemistry Issues Cl HCl + H2O Cl - = Soluble Chlorides Scrubber Blowdown Ponds Release off to the sea

101 Thank you!