005 energy saving tips

Anil Palamwar
anilpalamwar@yahoo.com
Energy Saving methods with typical
examples and exercises for power
stations
1

General
• Undertake regular Energy Audits.
• Plug all Oil Leakages.
• Leakage of one drop of oil per second amounts
to a loss of over 2000 liters/year.
• Filter Fuel oil in stages.
• Impurities in Fuel oil affect combustion.
• Pre-heat the oil. (Reduces viscocity)
• For proper combustion, oil should be at right
viscosity at the burner tip.Better atomisation.
2

General
• Provide adequate Pre-heat capacity for fuel oil.
• Incomplete combustion leads to wastage of fuel.
• Observe the colour of smoke emitted from
chimney.
• Black smoke indicates improper combustion and
fuel wastage.
• White smoke indicates excess air & hence loss of
heat.
• Hazy brown smoke indicates proper combustion.
• Use of Low air pressure “film burners” helps save
oil up-to 15% in furnaces.
3

Furnace
• Recover & utilize waste heat from furnace flue gas
for preheating of combustion air. (Air-pre-heater)
• Every 21°C rise in combustion air temperature results
in 1% fuel oil savings.
• Control excess air in furnaces.
• A 10% drop in excess air amounts to 1% saving of
fuel in furnaces.
• For an annual consumption of 3000 kl. of furnace oil.
• This means a saving of Rs 3 Lacs. (Cost of furnace oil-
Rs. 10 per litre).
4

Furnace
• Reduce heat losses through furnace openings.
• Observations show that a furnace operating at a
temperature of 1000°C having an open door
(1500mm*750mm) results in a fuel loss of 10 lit/hr.
• For a 4000 hrs. furnace operation this translates
into a loss of approx. Rs. 4 Lacs per year.
• Improve insulation if the surface temperature
exceeds 20°C above ambient.
• Studies have revealed that heat loss form a furnace
wall 115mm thick at 650°C amounting to 2650
Kcal/m2/hr can be cut down to 850 kcal/m2/he by
using 65 mm thick insulation on the 115 mm wall.
5

Boiler
• Remove soot deposits when flue gas
temperature rises 40°C above the normal.
• A coating of 3mm thick soot on the heat
transfer surface can cause an increase in fuel
consumption of as much as 2.5%.
• Recover heat from steam condense.
• For every 6°C rise in boiler feed water
temperature through condensate
return, there is 1% saving in fuel.
6

• Improve boiler efficiency.
• Boilers should be monitored for flue gas
losses, radiation losses, incomplete
combustion, blow down losses, excess air etc.
• Proper control can decrease the consumption up-
to 20%.
• Use only treated water in boilers.
• A scale formation of 1mm thickness on the
waterside would increase fuel consumption by
5-8%.
• Stop steam leakage.
• Steam leakage from a 3 mm-diameter hole on a
pipeline carrying steam at 7kg/cm2 would waste
32 kl of fuel oil per year amounting to a loss of Rs.
3 Lacs.
7

• Maintain steam pipe insulation.
• It has been estimated that a bare steam
pipe, 150 mm in diameter and 100m in
length, carrying saturated steam at 8kg/cm2
would waste 25 kl of furnace oil in a year
amounting to an annual loss of Rs. 2.5 Lacs.
• Frequently, insulation is not restored after
maintenance work.
8

D.G. Sets
• Maintain diesel engines regularly.
• A poorly maintained injection pump increases fuel
consumption by 4Gms/KWH.
• A faulty nozzle increases fuel consumption by
2Gms/KWH.
• Blocked filters increase fuel consumption by
2Gms/KWH.
• A continuously running DG set can generate 0.5 Ton/Hr
of steam at 10 to 12 bars from the residual heat of the
engine exhaust per MW of the generator capacity.
• Measure fuel consumption per KWH of electricity
generated regularly.
• Take corrective action in case this shows a rising trend.
9

Electrical Energy Conservation
• Improve power factor by installing capacitors
to reduce KVA demand charges and also line
losses.
• Improvement of power factor from 0.85 to
0.96 will give 11.5% reduction of peak KVA.
• And 21.6% reduction in peak losses.
• This corresponds to 14.5% reduction in
average losses for a load factor of 0.8.
10

• Avoid repeated rewinding of motors.
• Observations show that rewound motors
practically have an efficiency loss of up-to 5%.
• This is mainly due to increase in no load
losses.
• Hence use such rewound motors on low duty
cycle applications only.
• Use variable frequency drives, and fluid
couplings for variable speed applications such
as fans, pumps etc.
• This helps in minimizing consumption.
12

Illumination
• Electronic ballast in place of conventional choke
saves energy up-to 20%.
• CFL lamp in place of GLS lamp can save energy
up-to 70%.
• Clean the lamps & fixtures regularly.
• Illumination levels fall by 20-30% due to
collection of dust.
• Use of 36W tube-light instead of 40 W tube-light
saves electricity by 8 to 10%.
• Use of sodium vapour lamps for area lighting in
place of Mercury vapour lamps saves electricity
up-to 40%.
13

Compressed Air
• Compressed air is very energy intensive.
• Only 5% of electrical energy are converted to
useful energy.
• Use of compressed air for cleaning is rarely
justified.
• Ensure low temperature of inlet air.
• Increase in inlet air temperature by 3°C increases
power consumption by 1%.
• It should be examined whether air at lower
pressure can be used in the process.
• Reduction in discharge pressure by 10% saves
energy consumption up-to 5%.
14

• A leakage from a ½” diameter hole from a
compressed air line working at a pressure of
7kg/cm2 can drain almost Rs. 2500 per day.
• Air output of compressors per unit of
electricity input must be measured at regular
intervals.
• Efficiency of compressors tends to deteriorate
with time.
15

Refrigeration & Air Conditioning
• Double doors, automatic door closers, air
curtains, double glazed windows, polyester sun
films etc. reduce heat ingress and air-
conditioning load of buildings.
• Maintain condensers for proper heat exchange.
• A 5°C decrease in evaporator temperature
increases the specific power consumption by
15%.
• Utilisation of air-conditioned/refrigerated space
should be examined and efforts made to reduce
cooling load as far as possible.
16

• Utillise waste heat of excess steam or flue
gases to change over from gas compression
systems to absorption chilling systems and
save energy costs in the range of 50-70%.
• Specific power consumption of compressors
should be measured at regular intervals.
• The most efficient compressors to be used for
continuous duty and others on standby.
17

Cooling Towers
• Replacement of inefficient aluminium or fabricated
steel fans by moulded FRP fans with aerofoil designs
results in electricity savings in the range of 15%.
• A study on a typical 20ft. diameter fan revealed that
replacing wooden blade drift eliminators with newly
developed cellular PVC drift eliminators reduces the
drift losses from 0.01-0.02% with a fan power energy
saving of 10%.
• Install automatic ON-OFF switching of cooling tower
fans and save up-to 40% on electricity costs.
• Use of PVC fills in place of wooden bars results in a
saving in pumping power of up-to 20%.
18

Pumps
• Improper selection of pumps can lead to large
wastage of energy.
• A pump with 85% efficiency at rated flow may
have only 65% efficiency at half the flow.
• Use of throttling valves instead of variable speed
drives to change flow of fluids is a wasteful
practice.
• Throttling can cause wastage of power to the
tune of 50 to 60%.
• It is advisable to use a number of pumps in series
and parallel to cope with variations in operating
conditions by switching on or off pumps rather
than running one large pump with partial load.
19

• Drive transmission between pumps & motors
is very .
• important. Loose belts can cause energy loss
up-to 1-20%.
• Modern synthetic flat belts in place of
conventional V-belts can save 5% to 10% of
energy.
• Properly organized maintenance is very
important. Efficiency of worn out pumps can
drop by 10-15% unless maintained properly.
20

HEAT RATE
AND
AUXILIARY POWER CONSUMPTION
IMPROVEMENT
REDUCTION OF APC
21

Gross TG Heat Rate
= {(Main Steam Flow X MS Enthalpy)
- (FW Enthalpy at Eco I/L X Feedwater flow at I/L)
+ CRH Steam Flow X (HRH Enthalpy - CRH Enthalpy)
+ RH Spray X (HRH St Enthalpy - FW Enthalpy at Eco I/L)}
Gross Generation
xxxxxxxxxxxxxxxxxxx
Gross Unit Heat Rate =
Gross TG Heat Rate / Boiler Efficiency
22

Heat Rate in Short
• Therefore the heat rate in K.Cal / KWh
• =
• Net heat used by the System in K.Cal/
Electrical output in KWh.
23

24
HEAT INPUT TO TURBINE AND HEAT RETURN
HOT R/H
LIVE STEAM
COLD R/H
TO ECONOMISER
HPT IPT
HPH
RH
LPHDEA
LPTLPT
C
Maximum effort is made to return as much heat as
possible to the Boiler, But latent heat is lost in the
Condenser.

THERMAL POWER PROCESS – INPUT & OUTPUT
25
C.W.OUTLET
C.W.INLET
253.03 MW
FEEDWATER
CONDENSATE
HEAT INPUT BY
FUEL FIRING=
585.28 MW
(2397K.Cal/KWH)
BOILER
EFFICIENCY
= 86.17 %
STEAM OUTPUT
FROM BOILER &
INPUT TO TURBINE
=504.34 MW
2065 K.Cal / KWH
EFFICIENCY=92.41 %
GENERATOR
EFFICIENCY
=98.58%
LP & HP
HEATERS

Heat Energy To Electrical Energy
• Conversion Factor :- 860 Kcal = 1 Kwh
• TG Heat Rate = 2065 Kcal / Kwh
At 33 deg. C.W. Inlet
• Gross TG Efficiency (860/2065) = 41.65 %
• Boiler Efficiency = 86.17 %
• Gross Unit Heat Rate (2065 / 0.8617) =
2397 Kcal / Kwh
• Gross Unit Efficiency (860 / 2397 ) =
35.88 %
26

WHY A.P.C.Reduction ????
• A TPS is like any other factory.
• A TPS has to handle the INPUTS and discharge the
OUTPUTS of its process of power generation.
• COAL – AIR – WATER are the inputs .
• FLUE GASES – ASH – are the outputs.
• Fans – Pumps –Crushers –Conveyors – Feeders etc. are
needed to handle these.
• These auxiliaries use a motor as the prime mover.
• The motors consume part of the electricity produced.
• The export of power is reduced by Auxy. Consmn.
27

Boiler Auxiliaries - Schematic
28

FD Fan-A
FD Fan-B
W
I
ND
B
OX
FD Fan / Secondary Air Circuit
Scanner Air Fan
Igniter Fan
APH-B
APH-A
SCAPH-A
SCAPH-B
FLUE GAS
FLUE GAS
PRDS
PRDS
29

PA Fan-A
PA Fan-B
Filter
Filter
SA Fan-B
SA Fan-A
HotAirToMills
ColdAirToMills
COLDPAHEADER
Primary Air Circuit
To Mills
A/H
A
A/H
B
SCAPH
SCAPH
HotPAHeader
30

Flue gas
PA SA
Flue gas
SAPA
A
I
R
S
I
D
E
G
A
S
S
I
D
E
Regenerative Air Heater
31

Air Circuit
Cold Secondary
Air Hot Secondary Air to Wind Box
Cold Primary
Air
Hot Primary Air
to Bowl Mills
TemperingAir
Bowl
Mill
Pulverized Coal & Air
Mixture to Burners
Atmos
Air
Atmos
Air
Seal Air
Fan
Scanner
Air Fan
To
scanners
To Mills
PA
Sector
SA
Sector
F/Gas
Sector
Tri-sector Air
Pre-Heater
33

Wind box – Secondary Air Dampers-Coal & Oil
Burners –Igniters.
34

Secondary Air Dampers – (S.A.D.)
35

Louvres & Drift Eliminators
36

Efficiency – Loading of the Plant
• If the auxiliaries do not work efficiently, they will
consume more power.
• This will reduce the export and the Efficiency of the
plant as a whole.
• Proper maintenance of the auxiliaries will reduce
APC.
• Every auxiliary has a no-load power consumption.
• When it runs at less capacity than design, then %
consumption will be high.
• Hence the need to run the PLANT at OPTIMUM
capacity.
37

Reasons for inefficiency
• Auxiliary not running as designed.
• Due to wear and tear in operation.(Neck Rings)
• Worn Grinding elements, fan blades.
• Dampers not functioning properly
• Inadequate Loading on the TG Set.
• Deposition of soot / ash on heat transfer surfaces.
• Water side deposition on tubes of Boiler / Condensor.
• Poor D.M. water chemistry.
• Poor Cooling water chemistry and Poor C.W. system.
• Poor vacuum condition.
38

Boiler Efficiency by Loss Method
• Boiler Losses Design Value %
1. Un-burnt Carbon (In B/A & F/A) 0.331
2. Dry Gas Loss 4.918
3. Moisture in Fuel 1.243
4. Hydrogen In Fuel 5.217
5. Moisture in Air 0.074
6. Radiation Losses (Fixed) 0.200
7. Sensible Heat in Bottom Ash 0.071
8. Sensible Heat in Fly Ash 0.102
9. Unmeasured Losses[1.5+(7)+(8)] 1.673
10. TOTAL 13.83
11. Design Blr.Effi. (100-13.83) = 86.17
39

Turbine Losses
• Internal Losses
• A] Friction Losses
• Nozzle Friction
• Blade Friction
• Disc Friction
• B] Diaphragm Gland & Blade Tip Friction
• C] Partial Admission (Throttling)
• D] Wetness
• E] Exhaust (Leaving Loss)
40

• External Losses
• – A] Shaft Gland Leakage
• – B] Journal & Thrust Bearing.
• – C] Governor & Oil Pump
41

Turbine Cycle Heat Rate Deviations
• Due to
• 1]] Main Steam Pressure
• 2]] Main Steam Temp..
• 3]] HRH Steam Temp..
• 4]] Pressure Drop Across Re-Heater
• 5]] Condenser Vacuum
• 6]] F.W..Temp at Economiser Inlet
42

Loading of HPT – IPT -LPT
• Design Turbine Cylinder Efficiency & Load
Sharing of 210 MW LMZ M//C—
Load -%- Load MW Cylender ῇ
• HPT : 24.76 % 52 MW 88.11%
• IPT : 45.24 % 95 MW 89.93%
• LPT : 30.00 % 63 MW 85%
• TOTAL: 100 % 210 MW
43

Generator Losses
45
Losses MW %
% of Total
Losses
Iron Loss (Core
Loss)
0.436 0.208 14.63
Windage & Friction
Loss (Core Loss)
0.720 0.343 24.16
Stator Copper Loss 1.010 0.481 33.89
Rotor Copper Loss 0.814 0.388 27.32
Total Losses 2.980 1.420 100.00

46
0.000
0.200
0.400
0.600
0.800
1.000
1.200
Iron Loss
(Core Loss)
Windage &
Friction Loss
(Core Loss)
Stator
Copper Loss
Rotor
Copper Loss
GENERATOR LOSSES - MW
MW

WHY ENERGY EFFICIENCY IS IMPORTANT ?
• Depleting fossil fuel-Resources are scarce
• Optimum plant utilization-Competitiveness
• Global warming-Carbon Credit
• Designated consumer-E.A. made it
Mandatory.
• Generate more energy with same fuel
47

PERIOD STEAM PRESSURE&
TEMPERATURE
UNIT SIZE
(MW)
TURBINE
Heat Rate
(Kcal/kWh)
Unit Heat Rate
(Kcal/kWh)/
Efficiency
1951-60 60 kg/cm2, 482oC 30 – 57.5 2470
1961-75 70 kg/cm2, 496oC to
90 ata 538oC
60 – 100 2370
1961-75 130 ata 535/535oC 110 – 120 2170 – 2060 2552-2423
1977-82 130 ata 535/535oC 210 (Russian) 2060 2423/
35.4%
1983+ 150 ata 535/535oC 210 (Siemens) 2024 2335
36.8%
1984+ 170 ata 535/535oC 500 1950 (TDBFP) 2294
37.4%
1990+ 150 ata 535/535oC
170 ata 538/538 oC
210/ 250
250/ 500
1950 (MDBFP)
1950 (TDBFP)
2294
2294
*Above are best design values (design rates of individual unit varies based on reference
ambient, coal quality, design and supply dates)
48

EFFICIENCY IMPROVEMENT CAN GIVE YOU
For an average increase of 1 % in the Efficiency
would result in:-
 Coal savings of approx. 11 million tons per annum
worth Rs.13,000 Million
 CO2 reduction about 13.5 million tons per annum
 Lower generation cost per kWh- as more efficient
the unit works, the more economical it is
 1% increase in efficiency for 210 Mw unit with
heat rate 2335 kcal/kwh means heat rate
improvement to 2275 kcal/kwh
49

MAJOR CAUSE OF INEFFICENCY IN POWER
PLANT
• High Flue gas exit Temp
• Excessive amount of excess air(O2)
• Poor Mill/Burners performance causing high
unburnt carbon in fly and bottom ash
• Poor insulation
• Poor house Keeping
• Poor instrumentation and automation
50

MAJOR CAUSE OF INEFFICENCY IN POWER
PLANT (Cont…)
• Not running the units on design parameter
• Heaters not in service or poor performance of
regenerative system
• Poor condenser vacuum
• Excessive DM water consumption- passing and
leakages
• Use of Reheat spray to control Reheat
Temperature
• Poor Cylinder Efficiency of turbine
51

CONTROLLABLE PLANT PARAMETERS
• M.S. & R.H. Steam Temperatures
• M.S. Steam Pressure
• Condenser Vacuum
• Final Feed Water Temperature
• DP Across Feed Regulation Station
• Auxiliary Power Consumption
• Make Up Water Consumption
52

SYNERGIZE OPERATION
OF UNIT
Need to clearly understand the relation between
performance & fuel, operation and design
parameters
Operational behavior and performance
Impacts of operating efficiency of Boiler, Turbine and
their auxiliaries on Net Unit Heat Rate
Maximum Achievable Load, Maintenance &
Availability
53

SOME CRITICAL FACTORS AFFECTING BOILER
PERFORMANCE
• Fuel:- Heating Value, Moisture Contents, Ash Composition,
Ash Contents,& Volatile Matter.
• Operational Parameter:- Level of Excess Air, & operating
Condition of Burner Tilt Mechanism.
• Design:- Heating input per plan area, Height of Boiler,
Platens & pendants heat transfer Surfaces, Burner & wind
Box design.
54

BEHAVIOURAL IMPACTS
• Low heat value results in over firing of fuel causing more heat availability
for super heater and re-heater thus more attempration spray
requirement. Hence increase in THR, overloading of ash handling system,
fans and increased soot blowing
• Moisture content increase causes increase in heat transfer to S.H, and
R.H. Hence again increase in attempration spray and THR (Turbine Heat
Rate)
• Ash composition and contents increases damage to pressure parts
surfaces because of melting behavior of low fusion ash temperature of
blended coal in particular
• In consistency in fired fuel characteristics results in variation in excess air
requirement thereby increasing stack loss and hence boiler efficiency
reduction, overloading of ID Fan and ultimately unit load limitation
• High heat value causes excessive radiant heat transfer to water walls
thereby leaving lesser heat for super heater and re-heater
• .
55

Normally excess air ranges from 15% to 30% of stoichiometric
air.
• High O2 % and presence of CO at ID Fan outlet are indicator of
air in leakages and improper combustion in furnace
• Poorly effective damper control also is the cause of higher SEC
of fans both primary and secondary
• The quality and purity of feed water and make up water is
also required to be maintained in a meticulous way by limiting
blow down losses to nearly 1% and by checking the passing
and leakages of valves. However, maximum 3% of flow can be
taken as make up for these causes including soot blowing
requirements
• Soot blowing is dependent on ash contents and is unit
specific. Intelligently devised soot blowing can result in saving
the fuel
BEHAVIOURAL IMPACTS
56

• Cascading effects on efficiency, loading and
availability because of following systems and
equipments performance also needed to be looked
into. The systems are:-
Fuel receiving, preparation and handling systems.
Pulverizing system
Air Heater
Fans
Electrostatic Precipitator
Fly ash handling system
Bottom ash handling system
Waste disposal system
BEHAVIOURAL IMPACTS
57

PERFORMANCE IMPACTS ON STEAM CYCLE
, UNIT HEAT RATE & OUTPUT
• Various design & operating parameters of a
unit are responsible for its cycle
performance, heat rate,& out put
58

CRITICAL FACTORS AFFECTING CYCLE
PERFORMANCE
1. Re-heater & its system pressure drop
2. Extraction line pressure drop
3. Make up
4. Turbine exhaust pressure
5. Air preheat
6. Condensate sub-cooling
7. S/H & R/H spray flows
8. Wet Bulb Temp
9. Top Heaters out of service
10. H.P. heater drain pump
11. Type of BFP drives & method of flow control
59

RH & ITS SYSTEM PRESSURE DROP….
• Every one 1% decrease in drop can improve
THR and output by 0.1% & 0.3% respectively
• Normally designed for pressure drop
equivalent to 10% of HP exhaust pressure
• Causes are
Feed Heater abnormalities
R/H safety valve passing
60

EXTRACTION LINE PRESSURE DROP…
• Permissible pressure drop between stage
pressure & Shell pressure is maximum 6%
• For every 2% increase in this pressure drop,
THR would be poorer by 0.09%
61

CYCLE MAKE-UP….
• Acceptable value of make up water is 3% to
offset cycle water losses
• For every 1% increase in make up 0.4%
increase in THR & 0.2% reduction on output is
there
62

EXHAUST PRESSURE…
• Increase & decrease in exhaust pressure do
affect the THR.
• Though no valid thumb rule has been devised
so far, however last stage blade design &
exhaust area of turbine do affect the impact of
changing exhaust pressure.
63

AIR PRE-HEAT….
• Air preheating of combustion air before entry to
regenerative air heater is done with either steam
coil air pre - heater or hot water pre heating coil to
maintain Average Cold End Temperature (ACET) to
escape dew point temperature complications
• Condensate retrieval is necessary to avoid
deterioration to THR depending upon unit load and
combustion pre heating duty
64

CONDENSATE SUB-COOLING…
• For 30% total flow and 2.5 deg C sub-cooling
,an increase of 0.001% in THR can be there for
every subsequent 10% increase in flow
65

R.H & S.H. SPRAY FLOW…
• Spray water whether drawn from BFP or after
the final heater, it is always less the generative
and less productive as well
• Every 1% spray flow, correction need to be
done in THR & load computed from the curves
supplied with the machine
66

TOP HEATER OUT OF SERVICE….
• Extraction steam flow meant for top heater is
required to pass through turbine thereby
increasing the output.
• But at the same time final feed water temp. Is
lowered resulting in poor THR.
• The % loss increases from lowest stage (.5 to
.6 ) to highest stage (1.2 to 1.5%)
• Roughly each Deg C in TTD will result in a loss
of 0.25% efficiency.
67

PERFORMANCE MONITORING
• Analyze the poor efficiency areas from previous
record
• Go down to specific system and then to component
• Carry out performance/diagnostic study as suggested
in the Auditing Manual & operating manual
• Devise a unit specific efficiency control sheet for few
terminal conditions (Act vs Des)
• Monitor once per shift to know the operating
efficiency and check any deterioration
68

Coal Handling Plant
• Coal Crushers-
• If significant quantity of coal >20 mm size is observed
on down side of crusher then it may led to
substantial decrease in mill performance.
• Identification of combination of various least power
consuming equipmen and recommending merit
order operation.
• Use of natural daylight through conveyor galleries
and use of fire resistant translucent sheet.
69

Soft Starters- V.F.D.
• Explore Installation of power saver device in major LT
motors. (Conveyor belt etc.):
• Major HT /LT motors i.e. conveyors, crushers etc. are
often partially loaded & also there is frequent starts
/stops.
• Explore the possibility of providing power saver
devices (soft starters) in major motors.
70

Power Factor of Motors.
• Power factor correction possibility: Induction motors
may have vey low power factor, leading to lower
overall efficiency. Capacitors connected in parallel
with the motor are used to improve the power
factor. The PF correction reduces KVA demand,
reduced I2R losses in cable upstream of capacitor,
reduced voltage drop in cables (leading to improved
voltage regulation), and an increase in the overall
efficiency of the plant electrical system.
71

Chemicals for Dust Suppression
• Explore the possibility of using chemicals for reduced
water spray:
• Mixing of chemical compounds in water provides
much better atomization of water spray, by reduction
in surface tension of water.
• Thus for the given application of dust suppression,
lesser quantity of water is sprayed which also results
into lesser wastage of latent heat in the steam
generator.
72

Use of Bull Dozers ?
• Maximum Mechanical Handling: Minimum Bulldozing:
Receipt, unloading, stacking and reclaiming and the selection
of machinery should be such that all the handling operations
are accomplished without the use of semi mechanized means
like bulldozers which are more energy intensive equipment.
• When coal is stocked in yard for more than incubation period
(duration between coal mined and getting self
ignited), special precautions like compacting water spraying
must be taken.
•
73

Bunkering Frequency
• Reduced Number of Fillings:
• Live storage capacity of raw coal bunkers and the
filling pattern of bunkers is so planned that,
• 24 hours coal requirement of the generating units is
met by not more than two fillings per day.
• This will eliminate frequent starting and stopping of
the CHP system.
74

75
Electric Motors
1. Induction Motors. (Wound Rotor, Squirrel Cage Rotor)
2. Direct Current Motors.
3. Synchronous Motors.
Motor Speed (RPM) = 120 x Frequency /No.of Poles.
If f=50 c/s, Then motors speeds will be
2 pole = 3000 rpm; 6 pole = 1000 rpm
4 pole = 1500 rpm; 8 pole = 750 rpm.
10 pole =600 rpm; 12 pole = 500 rpm.

76
Slip
Actual motor speed of an Induction Motor is less than
the synchronous speed.
The difference is called slip.
Slip (%) = (S.S.-F.L.S) x 100 / S.S.
S.S. = Synchronous Speed
F.L.S.= Full Load Speed.
Power Factor = KW / KVA = Cos. Ф
If SS = 1500; and FLS = 1440; then ,
Slip (%) = (1500 – 1440) x 100 / 1500
= 4 %.

77
Motor Efficiency and p.f.
Efficiency = Mech. Power Output /Electrical Input
Power factor – like in inductive loads , is less than one.
So for same real power the current drawn will be more for
the lower power factor.
High efficiency and p.f. close to unity for efficient overall
plant operation.
Squirrel Cage motors are more efficient.
Similarly, higher speed, higher rating, and better cooling
result in better efficiency.

78
Losses
Intrinsic losses depend on the design.
Fixed losses = magnetic core loss + Friction + Windage.
Variable losses depend upon load =Cu.Loss in Stator
+Cu.Loss in Rotor + Stray losses.
Part load performance also depends upon design.
Efficiency and p.f. are low at lower loads.
No load test – Rated voltage is applied and motor is
brought to full speed. Note the following:-
(i)Input power,(ii)Current ,(iii) frequency,(iv)Voltage.
Input Power at No-Load = Stator Cu.loss +[Friction
+Windage]

79
Friction & Windage (F & W)losses
If we plot No-load input versus Input voltage, the
intercept will be F&W (Friction & Windage)component.
Also,
F&W and Core loss = Input Power – Stator Cu.Loss.
Stator & Rotor Cu.Loss –Stator resistance measured by
bridge or Volt-Amp method.
Resistance must be corrected for temperature.
R2/R1 = (235+t2)/ (235 + t1)
*t1 – Ambient temperature in deg.C.
*t2 –Operating temperature in deg.C.

80
Rotor Resistance & Cu.Loss
Rotor resistance can be determined by Locked Rotor test
at reduced frequency.
However Rotor Cu.Loss is measured from measurement
of slip, by Stroboscope or Tachometer.
Rotor Cu.Loss = Slip x (Stator Input – Stator Cu.Loss –
Core loss )
Stray Load Losses IS & IEC take it as 0.5% of output.
IEEE Table-for stray losses-
1 - 125 HP –1.8% 125 – 500 HP – 1.5%
500 – 2500 HP –1.2 % Above 2500 HP – 0.9%

81
Example
Motor Specifications-
Rated power =34 KW / 45 HP. Voltage =415 Volts
Current =57 Amps Speed = 1475 rpm.
Insulation class =F; Frame = LD 200 L; Connection = Delta
No load test data –
Voltage = 415 V; Current = 16.1 Amps; Frequency = 50 Hzs.
Stator phase resistance at 30 deg.C.= 0.264 Ohms.
No-Load –Power (PnL) = 1063.74 Watts.
Calculate (a)Core +F&W loss; (b) Stator resistance at 120 deg.C.
(c) Stator Cu.Loss at 120 deg.C.; (d)Full load slip and rotor
input.assume Rotor losses = slip x rotor input.
(e)Motor Input (assume 0.5% stray loss of motor rated power)
(f) Motor full load Efficiency and Power factor.

82
SOLUTION
(a)Let Pi = Core (Iron)loss and Fw = Friction + Windage loss.
No load power =PnL = 1063.74 Watts (given)
Stator Cu.Loss at 30 deg.C. = 3 x (16.2/cube root 3)x (16.2/cube root 3) x 0.264
=68.43 Watts.
Pi + Fw = PnL – Stator Cu.Loss = 1063.74 – 68.43 = 995.3 Watts.
(b) Stator resistance at 120 deg.C.
R120 = 0.264 x (120 + 235 )/(30 + 235 ) = 0.354 Ohms per phase.
(c) Stator Cu.Loss at Full load =Pst Cu.120 =
3 x (57/cube root 3)x (57/cube root 3)x 0.354 = 1150.1 Watts.
(d) Full load slip = S = (1500 – 1475 ) / 1500 = 0.0167
Rotor Input = Pr = Poutput /(1-S) = 34000 /(1-0.0167) = 34577.4 Watts.
(e) Motor Full load Input power = P input =Pr + P st Cu 120 + (Pi +Fw)+P stray
=34577.4+1150.1+995.3 + (0.005* x 34000) = 36892.8 Watts.
•Stray losses =0.5 % of rated output.(assumed)
(f) Motor Efficiency at Full Load =100 x ( P output / P input)
=100x(34000/36892.8) = 92.2 %

83
Full Load P.F.
Full Load P.F. = P input / Cube root 3 x V x I fl
=36892.8 / (1.732 x415 x 57 )
=0.90
Comments –
Measurement of stray losses is very difficult. Actual stray losses for
motors below 200 HP may be 1% - 3 %.
Slip from name plate data is not accurate.Actual speed should be
measured.
When a motor is rewound, resistance per phase may increase due
to material quality.Losses will increase.
Calculate losses if winding resistance increases by 10% per phase.

84
Energy Efficient Motors (EEM)
To improve Efficiency, the Losses must be reduced.
Stator & Rotor Cu.Loss – 55% to 60% 0f total losses.
Suitable cross section of conductors will reduce resistance.
To reduce motor current, the flux density has to be lowered.
For this the air gap has to be minimum permissible.
Rotor Cu.Loss can be reduced by selecting Copper bars in stead of
Aluminum bars.
Reducing the Slip will also reduce Rotor Cu.Loss as it is a function of
Slip.
Motor running closer to Synchronous speed will be more efficient.
Core Loss due to hysterisis and eddy currents.These are
independent of load. And are about 2-025% of total losses.
Use of thinner laminations for core reduces this loss.

85
Loss reduction . . . . .
Friction & windage loss –8-12 % of total losses.These
are also independent of load.
When Cu. Losses in Stator & Rotor are reduced, less
heat is generated. Then Smaller cooling fans can be
used to reduce windage.
Proper bearings and lubrication reduces friction loss.
Stray load losses. – Are proportional to Square of load
current.These are caused by LEAKAGE FLUX induced by
the load current in the laminations and are 4-5 % of
total losses.
Careful selection of slot numbers, tooth / slot geometry
and air-gap reduce these losses.

86
Factors affecting Efficiency
Quality of Input Power.
Actual voltage and Frequency.
B.I.S. specifies voltage variation of +/- 6% and frequency variation of
+/- 3% in which the motor should deliver its rated output.
Greater fluctuations are observed in our system and badly affect the
motor performance.
Voltage un-balance i.e. voltages in 3 phases not being equal are
more detrimental to motor performance and its life.
Any single phase loads must be distributed equally among all three
phases. OR,
Single phase loads should be fed from a separate line/transformer.

87
MOTOR LOADING
Input Power drawn by Motor (KW) x 100
% Loading =
% Loading =
Input Power drawn by Motor (KW) x 100
Name Plate 3 x KV x I x Cos Phi.
(Name plate KW / Name plate efficiency)
•Never assume Power Factor.
•Loading should not be estimated as the
ratio of Currents.

88
Questions
1. A 4-pole induction motor operates with 5% slip at full load.
Calculate the full load RPM of motor when the frequency is
50 c/s ; 40 c/s ; 45 c/s ; and 35 c/s.
2. List the losses and their approximate % in Induction Motors.
3. List the factors affecting efficiency of motors.
4. The p.f. of an Induction Motor – i)Increases with load ii) falls
with load, iii) Remains constant with load iv) Is not related to
load.
5. List methods of speed control of Induction Motors.
6. A 50 KW motor of 86 % efficiency is replaced by a motor of
89% efficiency.Calculate Annual savings for 6000 Hrs operation
and tariff Rs.4.50/KWH.

89
Steam for Heating
Use steam at lowest possible pressure for indirect heat
exchange.
LATENT HEAT is more at lower pressure.
Steam at 3 bar will release 134 KJ/Kg heat than at 10 bar.
Latent & Sensible Heat in Steam
0
200
400
600
800
0.1 0.15 0.2 0.25 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 2 5 10
Sensible Heat Latent Heat in K.Cal

90
Chimney smoke colour
BLACK SMOKE – Low air to fuel ratio.
Oxygen deficient combustion,
Incomplete combustion,
High un-burnt losses.
WHITE(or Invisible) SMOKE – High air to fuel ratio,
Oxygen rich system
Complete combustion but heat loss by excess air.
Excess fuel consumption due to higher stack loss.
GREY SMOKE – Optimum air to fuel ratio.
Complete combustion with least losses.
Optimum fuel consumption.

91
Recover Condensate
Condensate holds about 20% fuel energy.
Latent & Sensible Heat in Steam
0
200
400
600
800
0.1 0.15 0.2 0.25 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 2 5 10
Sensible Heat Latent Heat in K.Cal

92
Distribute steam at highest possible pressure
Steam volume is less at higher pressure.
This reduces piping cost.
Specific Volume M3/Kg
0
5
10
15
20
0.1
0.15
0.2
0.25
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.013
2
5
10
Absolute Pressure Bars
VolumeinCubic
Meters

93
Steam Traps remove condensate from steam line,
Condensate film reduces heat transfer
160
120
80
40
0
STEAM AT
3 BARS
AIR
0.2 MM
CONDENS
ATE FILM
1 MM
PIPE WALL
6 MM
TEMPERATURE DROP
THROUGH AIR AND
CONDENSATE FILM

94
INSULATION
Keep the insulation DRY.
Heat loss through wet insulation can be 30 times more.
Conductivity of wet insulation is much higher than that
of dry insulation.

95
Steam Tapping must be from the top of the pipe.
Otherwise condensate may also flow out with the
steam and affect the process.

96
Condensate in steam line can accumulate and cause
hammering.It also erodes the bends.
Erosion seen in secondary condensate lines.
Not in Steam or Water lines.

97
Recover Heat in FLASH Steam
Flash steam may
be only 10-15%
but it holds nearly
50 % heat.
This heat must be
recovered to
improve efficiency.

98
Drain size must be properly selected
In adequate
sized pipe will
not drain drain
away the
condensate
fully.
This will affect
the process.
Drain pockets
are useful for
effective
draining.

99
Avoid group tapping of Dains
High pressure drain may block the draining of
other drains.

100
Convert Group Tapping To Individual Tapping

102
Steam Heating V/s Thermic Fluid
 1 Kg of steam is equal to 27 Kg of thermic fluid for
the same amount of heat transfer.
 Steam carries latent heat which is a major part of
total heat in the steam.
 Thermic Fluids carry only sensible heat.
 Smaller heat exchangers are possible with steam.

103
SATURATED V/S SUPERHEATED STEAM
 Superheated steam has to first cool to
saturation temperature and
 then it can give up its latent heat by
condensing.
 Thus the heat transfer coefficient of
superheated steam is lower than of saturated
steam which does not have to lose any
sensible heat before condensing.
 Thus use of saturated steam is preferable.

104
Enthalpy components of
STEAM at 10 Bar & 300 deg.C.
Latent
Heat
66%
Superheat
9%
Enthalpy
of Water
25%

/mydocuments/adp/npti/auxyConsmn. 105
Generation & Auxiliary Consumption
Sr.No. Generation
Auxy
Consmn.
% Auxy.
Consmn.
1 5.04 0.425 8.43
2 4.536 0.425 9.37
3 4.0824 0.404 9.89
4 3.67416 0.384 10.44
Generation reduced by 10 %
Auxy. Consumption reduces by 5 %
% Auxy Consumption rapidly rises.

AUXY CONSUMPTION
Factors-
•Plant Layout-
• C.H.P. , A.H.P. , W.T.P. ETC.
•Bhusawal TPS has two stage pumping of ash
slurry.
•Parli TPS water is pumped in two stages from
20 Km. Distance.

• WTP for Koradi & Khaperkheda TPS is situated
at opposite side from the water source.
• Some TPS have two stage coal crushing in CHP.

Condition of Auxy.
Similar P.A. Fans draw different current for same
load.(Air flow)
Boiler feed pumps are not opened until a pump fails.
Coal mills loading is different for same coal feeding.
These indicate loss of efficiency.
Maintenance spares must be selected wisely.
Cheap spares may prove costly in the long run.
Purpose of maintenance should be restoring original
efficiency of the auxy
and not just restoring it back in service.

Availability of Key auxy.s
•Oil Burners-
•Coal Mills
•Hot P.A. fans.
Availability of above auxiliaries greatly affects
GENERATION
and hence % auxy consumption.

Use of Design capacity
•C.H.P.- Loading of conveyor belts.
•Poor loading will result in more running time of CHP.
•Inadequate belt maintenance –More power
consumption.
•A.H.P. – Wet slurry disposal-
•If slurry concentration is poor, running hours will
increase.
•Boiler & Gas ducts – Excessive air ingress will overload
I.D.Fans and finally reduce generation.
•Filters – Choking affects power consumption/Output.
•Condenser cleanliness- Higher D.P. Power loss.

Coal Mills - Pulverisers
Performance depends upon air flow.
Air flow may be less due to
1. Blocked air inlet. This may be due to
i) Broken scrapper. Accumulation of coal in air path.
ii) Incorrect throat gap.
iii) Incorrect gap at inverted cone
1. Clogged classifier.
Close attention to these is necessary.

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