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Energy Efficient Process Heating. Energy Balance on Furnace.

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Presentation on theme: "Energy Efficient Process Heating. Energy Balance on Furnace."— Presentation transcript:

1 Energy Efficient Process Heating

2 Energy Balance on Furnace

3 Energy Saving Opportunities From Energy Balance  Reduce opening losses: radiation and air exchange  Reduce cooling losses  Reduce conveyance losses  Reduce storage losses  Reduce wall losses  Reduce flue losses –Improve internal heat transfer –Reduce air leakage into furnace –Control combustion air / oxygen  Reclaim heat –Pre-heat combustion air –Pre-heat load –Cascade heat to lower temperature processes

4 Reduce Opening Losses

5 Reduce Radiation Losses: ‘Room’ for Improvement

6 Reduce Radiation Losses: ‘Better’

7 Cover Charge Wells  2 ft x 4 ft open charge well radiates and convects heat  Cover charge well with mineral fiber insulation 75% of time  Savings = $1,500 /yr

8 Preheating Ladles: Too Much Space

9 Preheating Ladles: Nice Tight Fit

10 Reducing Air Exchange in Continuous Ovens By Modifying Entrance/Exit

11 Reduce Cooling Losses

12 Reduce Conveyance Losses  Slow conveyor –Brazing oven at 1,900 F –Conveyor runs at 0.7 ft/min –Conveyor loaded 30% of time –Slow conveyor to 0.3 ft/min when unloaded –Reduces conveyor losses by 40%

13 Reduce Conveyance Losses Lighter conveyance fixtures reduce energy carryout losses

14 Reduce Storage Losses Larger batch sizes to reduce number of loads in heat treat ovens

15 Reduce Storage Losses Reduce bricks (thermal mass) on transport cars

16 Reduce Storage Losses Increase batch sizes in arc furnaces

17 Reduce Wall / Surface Losses

18 Insulate Hot Surfaces  Insulate four lids at 400 F  Induction furnace efficiency = 51%  Savings = $17,0000 /yr

19 Insulate Extruder Barrels

20 Turn Off Heat When Not in Use

21 Reduce Flue Losses

22 Flue Losses  Flue losses increase with: –Temperature –Flow

23 Reduce Flue Losses  Reduce Temperature –Improve internal heat transfer  Reduce Flow –Reduce air leakage into furnace –Combustion air control –Use O 2 instead of ambient air for combustion

24 Counter Flow Heat Transfer Reduces Exhaust Temperature Q T T x x Q Parallel Flow Counter Flow

25 Convert Batch Cross Flow Processes to Continuous Counter Flow Batch crucible melting Counter-flow cupola melting

26 Replace Reverb (Cross Flow) with Stack (Counter Flow) Furnace and Pre-heat Charge Reverb Furnace Stack Furnace

27 Lead Melt Furnace: Place Scrap on Top and Drain Molten Lead From Bottom

28 Molten Glass Transport: Each Exhaust Port Is A Zone

29 Relocate Exhaust Ports to Increase Counter-flow Within Zones Increases convection heat transfer by 83% Contact length = 2 x ( ) = 30 feet Contact length = ( ) = 55 feet

30 Set Exhaust Dampers to Increase Counter Flow in Dry Off Oven Product In Product Out 100% open 75% open 50% open 25% open 12% open

31 Set Exhaust Dampers to Increase Counter Flow in Tile Kiln Tile Exit Tile Entrance

32 Reduce Flue Flow

33 Heat in Flue Gases Air LeaksCombustion Air Fuel Reduce Air Leakage Negative Pressure

34 Seal Furnace Openings Seal opening around lid with mineral fiber blanket

35 Flue damper Hydraulic power unit Controller Compensating line Pressure tap (not in line with opposing burner) Hydraulic cylinder Counterweight Use Draft Control to Balance Pressure

36 Reduce Flue Flow: Control Combustion Air

37 Combustion with Air Minimum Combustion Air (Stoichiometric ): CH (O N 2 ) CO H 2 O N 2 Excess Combustion Air: CH (O N 2 ) CO H 2 O N O 2

38 Excess Combustion Air Decreases Flame Temperature and Efficiency Flue gas temperature) % Excess Air (% O2) in flue gases Air Preheat temperature) % Available Heat

39 Reduce Excess Air To 10% or CO Limit

40 Reduce Flue Flow: Replace Air with Oxygen

41 Combustion with Oxygen Eliminates Unnecessary Nitrogen  Combustion with Air –CH (O N 2 ) > CO H 2 O N 2 –Mair / Mfuel = [ (4 x 16) + (4 x 3.8 x 14) ] / (12 + 4) –Mair / Mfuel = 17.6  Combustion with O 2 –CH O 2 > CO H 2 O –Mo 2 / Mfuel = (4 x 16) / (12 + 4) –Mo 2 / Mfuel = 4.0

42 Combustion with Oxygen Increases Flame Temperature

43 Combustion with Oxygen Increases Efficiency

44 Reclaim Heat  Preheat combustion air  Preheat load/charge  Cascade to lower temperature process

45 Preheat Combustion Air with External Recuperator

46 ex. gas in T h1 = 1,465 F ex. gas out T h2 = 950 F comb. air in T c1 = 95 F comb. air out T c2 = 615 F

47 Preheat Combustion Air with External Recuperator

48 Preheat Combustion Air with Bayonet Recuperator

49 Preheat Combustion Air with Tube-in-Tube Heat Exchanger

50 Preheat Combustion Air with Regenerators

51 Pre-heat Load Using Counter-flow Burners Stack Current Design Recommended Design

52 Preheat Load Using Counter-flow

53 Preheat Load Using Preheating Shed

54 Cascade Heat to Lower-Temperature Process High Temperature Oven Low Temperature Oven

55 Cascade Heat to Waste Heat Boiler

56 VOC Destruction with Thermal and Catalytic Oxidizers  Reduce VOC Stream  Pre-heat VOC Stream with Recuperator  Pre-heat VOC Stream with Regenerator  Use Thermal Oxider Exhaust

57 Reduce VOC Stream with Carbon Adsorber  Inlet: 50,000 cfm with 50 ppm  Outlet: 5,000 cfm with 500 ppm (10x concentration)  Outlet (BAC): 50 cfm with 50,000 ppm (1,000x concentration)

58 Preheat VOC Stream in Thermal Oxidizer with Regenerator

59 Preheat VOC Stream in Catalytic Oxidizer with Recuperator Texhaust stream = 300 F

60 Use Thermal Oxidizer Exhaust: Direct Contact Water Heater

61 And Don’t Get Covered with Molten Metal !

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