energy efficient process heating
DESCRIPTION
Energy Efficient Process Heating. Energy Balance on Furnace. 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 - PowerPoint PPT PresentationTRANSCRIPT
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Energy Efficient Process Heating
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Energy Balance on Furnace
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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
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Reduce Opening Losses
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Reduce Radiation Losses: ‘Room’ for Improvement
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Reduce Radiation Losses: ‘Better’
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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
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Preheating Ladles: Too Much Space
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Preheating Ladles: Nice Tight Fit
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Reducing Air Exchange in Continuous Ovens
By Modifying Entrance/Exit
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Reduce Cooling Losses
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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%
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Reduce Conveyance Losses
Lighter conveyance
fixtures reduce energy
carryout losses
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Reduce Storage Losses
Larger batch sizes to reduce number of loads in heat treat ovens
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Reduce Storage Losses
Reduce bricks
(thermal mass) on transport
cars
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Reduce Storage Losses
Increase batch sizes
in arc furnaces
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Reduce Wall / Surface Losses
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Insulate Hot Surfaces
Insulate four lids at 400 F
Induction furnace efficiency = 51%
Savings = $17,0000 /yr
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Insulate Extruder Barrels
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Turn Off Heat When Not in UseHeat Loss at Contant Temperature
50
100
150
200
250
300
350
400
0.1 1.1 2.1 3.1 4.1 5.1 6.1 7.1 8.1 9.1
Tem
p (F
)
Heating Energy
Heat Loss With 8-hour Cooldown and 2-hour Reheat
50
100
150
200
250
300
350
400
0.1 1.1 2.1 3.1 4.1 5.1 6.1 7.1 8.1 9.1
Tem
p (F
)
Heating Energy
Heating Savings
50
100
150
200
250
300
350
400
1 11 21 31 41 51 61 71 81 91
Tem
p (F
)
Savings
Heating Energy
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Reduce Flue Losses
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Flue Losses
Flue losses increase with:– Temperature– Flow
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Reduce Flue Losses
Reduce Temperature– Improve internal heat transfer
Reduce Flow– Reduce air leakage into furnace – Combustion air control– Use O2 instead of ambient air for combustion
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Counter Flow Heat Transfer Reduces Exhaust Temperature
Q
T
T
x
x
Q
Parallel Flow
Counter Flow
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Convert Batch Cross Flow Processesto Continuous Counter Flow
Batch crucible melting Counter-flow cupola melting
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Replace Reverb (Cross Flow) with Stack (Counter Flow) Furnace and Pre-heat Charge
Reverb Furnace Stack Furnace
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Lead Melt Furnace: Place Scrap on Top and Drain Molten Lead From Bottom
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Molten Glass Transport:Each Exhaust Port Is A Zone
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Relocate Exhaust Portsto Increase Counter-flow Within Zones
Increases convection heat transfer by 83%
Contact length = 2 x (5 + 4 + 3 + 2 + 1) = 30 feet
Contact length = (10 + 9 + 8 + 7 + 6 + 5 + 4 + 3 + 2 + 1) = 55 feet
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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
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Set Exhaust Dampers to Increase Counter Flow in Tile Kiln
TileExit Tile
Entrance
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Reduce Flue Flow
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Heat inFlue
Gases
Air LeaksCombustion AirFuel
Reduce Air Leakage
Negative Pressure
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Seal Furnace Openings
Seal opening
around lid with
mineral fiber
blanket
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Flue damper
Hydraulicpower unit
Controller
Compensating linePressure tap
(not in line withopposing burner)
Hydraulic cylinder
Counterweight
Use Draft Control to Balance Pressure
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Reduce Flue Flow: Control Combustion Air
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Combustion with Air
Minimum Combustion Air (Stoichiometric):CH4 + 2 (O2 + 3.8 N2) CO2 + 2 H2O + 7.6 N2
Excess Combustion Air:CH4 + 4 (O2 + 3.8 N2) CO2 + 2 H2O + 15.2 N2 + 2 O2
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Excess Combustion AirDecreases Flame Temperature and Efficiency
Flue gas temperature)
% Excess Air (% O2) in flue gases
Air Preheat temperature)
% A
vaila
ble
Heat
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Reduce Excess Air To 10% or CO Limit
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Reduce Flue Flow: Replace Air with Oxygen
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Combustion with Oxygen Eliminates Unnecessary Nitrogen
Combustion with Air– CH4 + 2 (O2 + 3.8 N2) > CO2 + 2 H2O + 7.6 N2
– Mair / Mfuel = [ (4 x 16) + (4 x 3.8 x 14) ] / (12 + 4) – Mair / Mfuel = 17.6
Combustion with O2
– CH4 + 2 O2 > CO2 + 2 H2O– Mo2 / Mfuel = (4 x 16) / (12 + 4) – Mo2 / Mfuel = 4.0
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Combustion with Oxygen Increases Flame Temperature
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Combustion with OxygenIncreases Efficiency
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Reclaim Heat
Preheat combustion air Preheat load/charge Cascade to lower temperature process
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Preheat Combustion Air with External Recuperator
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Preheat Combustion Air with External Recuperator
ex. gas inTh1 = 1,465 F
ex. gas outTh2 = 950 F comb. air
inTc1 = 95 F
comb. air outTc2 = 615 F
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Preheat Combustion Airwith External Recuperator
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Preheat Combustion Air with Bayonet Recuperator
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Preheat Combustion Air with Tube-in-Tube Heat Exchanger
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Preheat Combustion Air with Regenerators
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Pre-heat Load Using Counter-flow
BurnersStack
Current Design
Recommended Design
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Preheat Load Using Counter-flow
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Preheat Load Using Preheating Shed
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Cascade Heat to Lower-Temperature Process
High Temperature Oven Low Temperature Oven
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Cascade Heat to Waste Heat Boiler
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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
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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)
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Preheat VOC Stream in Thermal Oxidizerwith Regenerator
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Preheat VOC Stream in Catalytic Oxidizer with Recuperator
Texhaust stream = 300 F
Burner Catalytic Oxidizer
Tc,1 = 72 F Counter-Flow Heat Exchanger
Tc,2
Tc,3 = 560 F
Th,1 = 625 F
Plant Air
Exhaust AirQcQNG
QHXR
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Use Thermal Oxidizer Exhaust: Direct Contact Water Heater
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And Don’t Get Covered with Molten Metal !