How to Increase boiler Efficiency? 20 proven methods that save up to 30% in fuel costs

1. ByBy
Improving Boiler EfficiencyImproving Boiler Efficiency

2. Utility and power plant Course
Assistant Chief Engineer
Qusay A.M.Saeed
Participant
for

3. How to Increase boiler Efficiency?
20 proven methods that
save up to 30% in fuel
costs

4. Efficiency Equation

5. Boiler heat losses

6. Efficiency
improvements
without Expenses

7. Method 1
Reduce Excess Air
Potential savingPotential saving :5%-10%
ProblemProblem :unneeded excess air is used, probably to dilute the flue gas so that
smoke is not seen.
SolutionsSolutions: reduce excess air to the minimum 10%-15% requird.

8. Typical Excess Air Values

9. Excess Air

10. Normal combustion efficiencies for natural gas at different amounts of
excess air and flue gas temperatures are indicated below
68.271.975.679.382.810.081.6
72.175.278.281.284.17.044.9
74.076.779.582.184.75.028.1
75.477.980.482.885.23.015
76.078.480.883.185.42.09.5
600500400300200OxygenAir
Net Stack Temperature1)
(o
F)Excess %
Combustion Efficiency (%)

11. Flue Gas Loss Combustion Oil
The relationship
between temperature
difference flue gas and
supply air,
CO2concentration in
the flue gas, and the
efficiency loss in the flue
gas combustion oil, is
expressed in the
diagram below.

13. Method 2
Decrease Flue-Gas Temperature
Potential savingPotential saving :1% for every 40°F.the potential saving are 3%,since many
stacks run 120°F too high.
ProblemProblem :Either excess air or fouling water and /or fire side tubes.
Solutions:Solutions:
1- If there is excess fuel,the fuel rate can be decreased to decease the
temperature .
2- if the tube are fouling up, steam production will suffer ,and the only solution
is to shut down and clean them up or blow soot on fireside.
2- An economizer may be economical (see method 15)

14. The TDS inside a boiler should be maintained at recommended levels else it can
lead to scaling of the boiler tubes and eventually failure of the tubes which is a
safety hazard.

15. Energy Loss from Scale
Deposits

16. Commerce
Increased Boiler Heating Time
due to Scale

18. Method 3
Reduce Boiler Pressure
Potential savingPotential saving :1%for every 70psig reduction
Problem :the boiler is being operated at a pressure higher
than necessary.
Solution :slowly reduce boiler pressure to a point where
the amount of steam produced is sufficient to fulfill plant
requirements

19. Method 4
Increase Fuel Oil Temperature
Potential saving : 5%
Problem :Atomize the fuel at the right
viscosity .Too high or too low a viscosity
will yield poor atomization and poor
efficiency .
Solution:
Preheat the fuel at 212°F-230°F or more so
that the fuel viscosity will be 100-300 sus

20. Fuels oils - their viscosity versus
temperature

21. Fuel Oil Heating System

22. Method 5
Optimize Fuel Atomization Pressure
Potential saving: 1%
Problem :The fuel atomization pressure is
lower or higher than that specified by the
nozzle or burner design
Solution: Adjust fuel pressure according to
nozzle operating instructions

23. Method 6
Reduce Boiler blowdown
Potential saving : 1%
Problem :excessive blowdown due to poor water
treatment and /or poor operating practices .the
hot blowdown stream has energy that is lost
unless it is recovered (see Method 16)
Solution: control feed water quality with the
appropriate water treatment; review operation
Procedures

24. Flash tank

25. Method 7
Optimize Single-boiler Firing
Potential saving :5%-10%
Problem: A boiler may come on for afew
minutes and then be off for several
minutes, resulting in large energy losses
due to the removal of useful heat when the
boiler is off; or a boiler may “hunt” i.e. the
firing rate is continually adjusting ,resulting
in much more excess air.

26. • Solution :for an on –off boiler ,fire the
boiler at an intermediate rate or buy a
smaller boiler ; for boiler that “hunt” adjust
the firing so that larger steam – pressure
fluctuation are allowed.

27. Method 8
Optimize multiple-boiler operation
Potential saving :2%-5%
problem: A plant have tow or more boilers
operates them without distributing the load
according to the efficiency each boiler .
Solution : Obtain the efficiency of each
boiler vs. load ; adjust each boiler to
operate at peak efficiency.

28. boiler efficiency vs. load

30. Method 9
Stop Steam Leaks
Potential :5%-10%
Problem: piping leak
Solution: plug leak as soon as they appear

32. • The biggest steam losses are caused by failing steam
traps or leaks into the steam system net. These
uncontrolled leaks can lead to enormous losses and also
enormous costs. The leaking traps can cause problems
with tracing of your equipment, problems with back
pressure into the condensate lines (which causes failure
of groups of steam traps), and make your cost for the
production of steam much higher. Problems with tracing
in one unit can be caused by leaking traps in a other unit
on the other side of the plant which indicates that
monitoring steam traps important is for the proper
working of your steam system.

33. Flange Leak Repair

34. Piping System Leaks 90ELL Enclosure

35. Flange Clamps

36. Valve Packing Leaks
Before - Steam Leak on Valve Packing
After - Repaired Steam Leak on Valve Packing

37. Steam leak rates

38. Steam leak rates

39. In addition to costing energy, steam leaks waste boiler
water and chemicals, and it can be dangerous to people
and equipment.

40. NOTE:
One pound of 100 psi steam contains about 1,200 BTUs. If
the steam is produced at 85% efficiency, the input
energy is 1,200 / 85% = 1,411 BTUs per pound.
Therefore, 1,000 pounds of steam requires at least 1.4
million BTUs to produce it. (1,411 BTUs per pound x
1,000)
1 MCF of Natural Gas contains 1 million BTUs
Cost to produce 1,000 lbs of steam from natural gas = 1.4 x
$ per MCF of Natural Gas
When natural gas costs $7.00 per MCF, 1,000 lbs of steam
costs (1.4 x $7) = $9.80

41. Method 10
Stop Steam-Trap Leaks
Potential saving :5%-10%
Problem: steam trap malfunctioning and
leaking steam.
Solution : check steam trap routinely and
repair them.

42. Steam trap leak

43. checking steam trap

44. Steam trap piping system

45. Efficiency
Improvements with
some Expenses

46. Method 11
Reduce Deposits in Burner
Potential saving : 1%-5%
Problem : organic and inorganic deposits
build in burner, reducing atomization
efficiency and therefore reducing
combustion efficiency .
Solution : use a fuel oil additive with
detergent dispersant to keep burners
clean

47. Burner
Clean burnerDeposit burner

48. Tips

49. Replacement and cleaning burners

50. Method 12
Reduce Scale and Soot Deposits on Fireside
Potential saving : 2% - 9%
Problem : soot and /or vanadium-based deposit
decrease the heat transfer rate. If all condition
are constant ,this decrease is noticeable when
the flue gas temperature increase with time.
Solution : treat fuel with additives to minimize
either soot deposits or vanadium-based scale.
Use soot blowers if available

51. Combustion
products
resulting from
burning of
fuels.

52. Layers of deposit associated with
coal-ash corrosion.

53. The flue pipe over half filled with
soot and deposit

54. Soot and scale do not only
increase energy consumption but
are as well a major cause of tube
failure

56. Fuel energy loss due to soot
Effect of Soot on Fuel Consumption
0
2
4
6
8
10
0.5
1.5
2.5
3.5Thickness of Soot Layer, mm
%FuelEnergyLoss

57. Warning triangle - risk of soot fire

58. Boiler Sootblowers

59. Soot Blower

60. Method 13
Reduce Scale and Deposits on Waterside
Potential saving : 2% - 4%
Problem : inorganic scale and deposits
decrease heat transfer rate ; i.e. flue gas
temperature increase with time.
Solution : treat feed water properly using
guidelines of boiler manufacturer or water
boiler standardizing

61. Energy loss due to scale deposits

62. Fuel energy loss due to scale
Effect of Scale on Fuel Energy Losses
0
2
4
6
8
10
12
0
0.25
0.5
0.75
1
1.25
1.5
1.75
2
Scale Thickness,mm
%FuelLoss
High density
Medium Density
Low Density

63. Water tube with soot outside and
scale inside

64. Fire tube with soot inside and
scale outside

65. Method 14
Increase Combustion Air
Temperature
Potential saving : 1%
Problem : preheat combustion air .every 40 °F rise
yields a 1% gain in efficiency.
Solution : there are several possible solutions:
relocate air intake duct so that a maximum air
duct temperature is obtained ,or install an air
preheater if possible and economically feasible.

66. Recoverable heat from boiler flue
gases

67. Air Heaters
Air heaters cool flue gases before they pass into
the atmosphere, increasing fuel-firing efficiency
and raising the temperature of the incoming air
of combustion. In low pressure gas or oil-fired
industrial
boilers, air heaters function as gas coolers
as there is no need to preheat the oil or gas
in order for it to burn.

68. Air Heaters

69. Method 15
Increase Feedwater Temperature
Potential saving :3%
Problem : raise water temperature
Solution : the equipment needed is an
economizer that uses the heat from flue gases, if
economically feasible. Also , the water can be
preheated using the waste heat from blowdown
(method 16).
10°F rise in feedwater temperature raisea
efficiency 1%

70. Economizers
Economizers help to improve boiler efficiency by
extracting heat from the flue gases discharged
from the final superheater section of a
radiant/reheat unit or the evaporative bank of a
non-reheat boiler. Heat is transferred to the
feedwater, which enters at a much lower
temperature
than saturated steam.

71. Economizes

72. Location of Air heaters and Economizers

73. Dew point of the flue gas

74. Method 16
Recover Heat Energy From Blowdown
Potential saving : 1%
Problem : preheat water by recovering energy from
blowdown.
Solution : add flash tank to system .the blowdown is
flashed by lowering the pressure in the flash tank;
the steam produced is then vented into the feed
water to boiler .some 50% of the heat in the
blowdown is recovered. Send blowdown at 220°F
to wast.

75. • Also aflash tank may be added ,followed
by aheat exchanger to extract one-third
more energy from the blowdown before
going to wast.

76. Recoverable heat from boiler
blowdown

79. Boiler Blowdown Heat Recovery
exchanger System

80. Install an Automatic Blowdown
Control System

82. Saving through Installion of
Automatic Blowdown
Control System

83. Method 17
Energy Recovery From Excessive Steam
Pressure
Potential saving :variable
Problem : use throttling or back pressure
turbine .
Solution : the idea is to utilize the energy
from steam rather than to decrease its
pressure though a throttling valve

84. Steam turbines
back pressure steam turbine Condensing Steam Turbine

85. Back-Pressure Steam Turbine

86. Condensing Steam Turbine

87. Replace Pressure-Reducing Valves
with Backpressure Turbogenerators
Many industrial facilities produce steam at a higher pressure than is demanded
by process requirements. Steam passes through pressure-reducing valves
(PRVs,
also known as letdown valves) at various locations in the steam distribution
system to let down or reduce its pressure. A non-condensing or backpressure
steam turbine can perform the same pressure-reducing function as a PRV,
while
converting steam energy into electrical energy.
In a backpressure steam turbogenerator, shaft power is produced when a
nozzle
directs jets of high-pressure steam against the blades of the turbine’s rotor. The
rotor is attached to a shaft that is coupled to an electrical generator. The steam
turbine does not consume steam. It simply reduces the pressure of the steam
that is subsequently exhausted into the process header.

88. Consider Installing High-Pressure Boilers
with Backpressure Turbine-Generators
When specifying a new boiler, consider a high-pressure boiler with a backpressure
steam turbine-generator placed between the boiler and the steam distribution
network. A turbine-generator can often produce enough electricity to justify the
capital cost of purchasing the higher-pressure boiler and the turbine-generator.
Since boiler fuel usage per unit of steam production increases with boiler pressure,
facilities often install boilers that produce steam at the lowest pressure consistent
with end use and distribution requirements.
In the backpressure turbine configuration, the turbine does not consume steam.
Instead, it simply reduces the pressure and energy content of steam that is subsequently
exhausted into the process header. In essence, the turbo-generator
serves the same steam function as a pressure-reducing valve (PRV)—it reduces
steam pressure—but uses the pressure drop to produce highly valued electricity
in addition to the low-pressure steam. Shaft power is produced when a nozzle
directs jets of high-pressure steam against the blades of the turbine’s rotor. The
rotor is attached to a shaft that is coupled to an electrical generator.

89. Method 18
Reduce Heat Losses in Boiler, Steam and
Valves
Potential saving :5% - 8%
Problem : heat is lost by radiation and convection
through the walls of uninsulated or poorly
insulated boiler surfaces and piping.
Solution : use a surface thermometer and
determine where heat losses are present ; then
insulate.

90. Surface Thermometer
Digital Surface Thermometer
Infrared (IR) Thermometer

91. Boiler Wall Insulation

92. Heat loss of uninsulated steam line

93. Pipe and Fitting Insulation

94. Tank Insulation

95. Valve Insulation
Jacket

97. Flue Duct

98. Method 19
Use Fuel Oil Rather Than Natural Gas
Potential saving : 2%
Problem : If the price of natural gas is the
same or higher than that of fuel oil,which is
more economical?
Solution: use fuel oil.even if both cost the
sam per MMBtu,fuel oil gives about a 2%
higher efficiency than natural gas ,the

99. • The reason for this is that natural gas has
more hydrogen atoms per unit weight than
fuel oil. therefore, more water is formed
from the gas, the the latent heat of
vaporization of water is lost when the
water vapor leaves the stack.
• MMBtu=Million Metric British Thermal
Units

103. Method 20
Change From Steam to Air Atomization
Potential saving : 1%
Solution : use are atomization for fuel oils.
The energy required to produce the are of
atomization is a small fraction of the
energy required to produce the steam of
atomization.

104. Air Atomization burner

105. References
• Manual for improving boiler and furnace
performance –borras
• Improving Steam System Performance
U.S. Department of Energy