boiler operation costs
TRANSCRIPT
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Boiler Operating Costs with
Natural Gas and #6 OilDr. Herbert Eckerlin
Center for Boiler Studies
Raleigh, NC
March 27, 2002
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Why Measure Parasitic Losses?
Cost comparison based on stack loss onlyignores parasitic losses and costs associatedwith oil-firing
Important to quantify thermal losses andparasitic losses to determine the truebottom line efficiency and steam cost
Bottom line efficiency helps in choosing themost economic fuel
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Fuel
Stack Loss
Tg
% O2
Fire Tube Boiler
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Effects of Excess Air on Flue
Gas Composition15
10
5
0
-50 0 50 100 150 200
Excess Air
CO
CO2
CO2
O2
C
O2,CO,or
O2(%)
Incomplete
Combustion
Excess Air (%)
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Typical Oil Firing SetTypical Oil Firing Set--upup
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Q Stack
Thermal Losses Common forThermal Losses Common for
Natural Gas and #6 OilNatural Gas and #6 Oilstack lossstack loss
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Thermal Losses Common for
Natural Gas and #6 Oil
Stack Loss Largest single loss
Depends on flue gas temperature, ambient air
temperature, excess air and type of fuel
To determine stack loss, measure all above
parameters
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Q Stack
Q CO
Q CH
Thermal Losses Common for NaturalThermal Losses Common for Natural
Gas and #6 OilGas and #6 OilCO and UnCO and Un--burnt CHburnt CH
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Thermal Losses Common for
Natural Gas and #6 Oil
CO and un-burnt CH Caused by incomplete combustion
Lack of air to support complete combustion
Poor mixing of fuel and air
Poor atomization of fuel oil
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Q Oil Storage Tank
Q Stack
Q CO
Q CH
Parasitic Losses for #6 OilParasitic Losses for #6 Oil
Tank HeatingTank Heating
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Parasitic Losses for #6 Oil
Oil Tank Heating Fuel oil is viscous and requires heating to
facilitate pumping
Generally heated to 140 F
Heat loss can be quite high for single wall un-
insulated oil storage tanks
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Q Oil Heater
Q Oil Storage Tank
Q Stack
Q CO
Q CH
Q Oil Pumping
Parasitic Losses for #6 OilParasitic Losses for #6 Oil
Pumping & PreheatingPumping & Preheating
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Parasitic Losses for #6 Oil
Oil Pumping Pumps are required to circulate oil from storagetank to the burner
Oil Preheating To ensure proper atomization, oil must be
heated 200 220 oF
Generally heated by steam or hot water
In some fire tube boiler application, steam/hotwater heating is augmented by electric heating
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Q Oil Heater
Q Oil Storage Tank
Q Atom
Q Stack
Q CO
Q CH
Q Oil Pumping
Parasitic Losses for #6 OilParasitic Losses for #6 Oil
AtomizationAtomization
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Parasitic Losses for #6 Oil
Oil Atomization For proper combustion, oil must be broken up
into small particles
Done by injecting steam or compressed air intosmall oil supply at the burner
Q St k
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Q Oil Heater
Q Oil Storage Tank
Q Atom
Q Stack
Q SootBlowers
Q CO
Q CH
Q Oil Pumping
Parasitic Losses for #6 OilParasitic Losses for #6 Oil
Soot BlowingSoot Blowing
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Parasitic Losses for #6 Oil
Soot Blowing Soot is created by oil burning
Soot leaves deposits on boiler tubes
Reduces heat transfer to boiler fluid
Generally cleaned by steam or compressed air
Fire tube boiler generally do not use soot blowers
Soot removal must be done by punching the tubes whenstack temperature gets too high
Should be done at least quarterly to prevent high stacktemperature resulting in high stack loss
Boiler must be shut down when tubes are punched
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Flue Gas Temperature
Over Time
200
250
300
350
400
450
0 5 10 15 20 25 30
Days
D
egF
#6 Oil High Fire
Gas High Fire
Gas Low Fire
#6 Oil Low Fire
Q Stack
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Q Oil Heater
Q Oil Storage Tank
Q Atom
Q Stack
$ Water$ Chemical $ Preheating
$ Maintenance$ Fuel Oil Additives
$ Oil Inventory
$ Corrosion
Additional Makeup Water
Q SootBlowers
Q CO
Q CH
Q Oil Pumping
Parasitic Losses and Cost for #6 OilParasitic Losses and Cost for #6 Oil
Inventory, Additives, Maintenance etc.Inventory, Additives, Maintenance etc.
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Parasitic Losses and Cost
for #6 Oil Oil Storage Inventory
Storing oil on site ties up capital This investment yields no return
Oil Additives
Purposes Reduce sludge in oil storage tank
Improve combustion
Reduce soot deposits
reduce cold end corrosion
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Parasitic Losses and Cost for
#6 Oil
Corrosion and Maintenance Sulphur in oil causes cold end corrosion
Adds to maintenance costs
Reduces boiler life
Q Stack 12.4%
S f Th l d
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Q Oil Heater
0.35%
Q Oil Storage Tank8.40%
Q Atom0.93%
Stack 12.4%
Q SootBlowers
Q CO
Q CH
Q Oil Pumping
1.15%
220oF
Radiation 1.0%
$ Water$ Chemical $ Preheating
$ Maintenance3.41%
$ Fuel Oil Additives
$ Oil Inventory0.30%
$ Corrosion
Additional Makeup Water
140
o
F
Summary of Thermal andSummary of Thermal and
Parasitic LossesParasitic Losses
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Bottom Line Efficiency for
Oil Firing
100
Stack Loss 12.4
Radiation 1.0
Oil Pumping 1.15
Oil Atomization 0.93
Corrosion & Maintenance 3.41
Oil Inventory 0.3Oil Heating 0.35
Oil Tank Heating 8.4
Bottom Line Efficiency 72%
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Bottom Line Boiler Efficiency
Comparison
82.5 90
72
0
10
20
30
40
50
60
70
80
90
100
N.G. Standard
Boiler
N.G. High
Efficiency Boiler
#6 Fuel Oil
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Effect of Parasitic Losses on
Cost of Delivered Steam
$7.32
30.6
$/GJ
cents/litre
Cost of Delivered Steam(considering stack and parasitic losses)
$1.23
8.6
$/GJ
cents/litre
Incremental Cost Increase(due to parasitic losses)
$6.09$/GJCost of Delivered Steam
(considering stack and radiation losses)
22.0
$5.27
cents/litre
$/GJ
Average Fuel Cost
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Conclusions
On average, parasitic losses can add about 9cents per litre to #6 fuel oil price
Take into account all parasitic losses and
costs associated with #6 fuel oil firing while
comparing costs with natural gas
Keep boilers properly tuned for maximumefficiency