1) The document discusses optimization of compressed air usage at a thermal power plant in India. It was observed that a significant portion (around 1/3rd) of total compressed air consumption was used for igniter cooling in the plant's boilers. 2) By improving the control system optimization of the air compressors and monitoring consumption patterns, the plant was able to reduce compressed air usage by 1135 cubic meters per hour. This led to estimated annual savings of 1.172 crore rupees. 3) The key optimization made was reducing the threshold current limit for the partial loaded air compressor, which improved efficiency. Monitoring consumption patterns also revealed igniter cooling as the major area for optimization, as it accounted

1. OPTIMIZATION OF COMPRESSED AIR IN THERMAL POWER PLANT-A
NOVEL APPROACH.
RD Katre*, Ashish Bahety**, Daitary Tripathy**, Vishal laddha**
*Sr, GM(C&I), Dy. Manager** (Control & Instrumentation)
Jindal Power Limited, 4 X 250 MW, Tamnar.
Energy conservation is the burning issue now- a- days due to the tremendous scarcity of electricity across the world and
sustainability of the globe. In order to reduce environmental pollution, either energy consumption should be reduced or energy
should be generated more with higher efficiency and low auxiliary power consumption in power generation. In power plants,
Compressor is the most inefficient auxiliary; therefore, specifically optimum use of compressed air is must. An attempt is
therefore made to improve the optimum use of compressed air in this case study. Compressed air is used as a driving force for
pneumatic instruments as a instrument air and for service air purpose in power plants. In addition to it, it is used for
miscellaneous purpose like furnace Igniter’s cooling and cleaning. It is unaccounted and uncontrolled in most of the power
plants. In the case study of JPL 4X250MW plant, during demand side management of compressed air, it is observed that there
is a lion’s share of igniter cooling air in total compressed air consumption. Case study reflects that there is huge potential of
saving in compressed air used for this purpose and the most potential conservation area for costly compressed air is Igniter
Cooling and Cleaning System in PF boiler, which consumes about 1/3rd of the total air consumption quantity in the plant. This
untouched area was explored for scope of reduction in air consumption; accordingly data was collected, analyzed and studied
with collective wisdom. Incorporated modification with use of state of art technology, through which it is possible to monitor
air consumption with high accuracy. Finally, succeeded in reduction of compressed air consumption quantity by 1135M3/Hr
which saves about Rs 1.172cr annually.
Key words: Energy conservation, sustainability, compressed air, Igniter cooling, conversion efficiency.
INTRODUCTION:
Auxiliary power consumption is considered as one of the major performance indices in thermal power plants.
Generally, 6-10% of total generated power is consumed in the power plant itself for running various auxiliaries and
processes. Air compressors accounts for significant amount of electricity ranges from 2 to 5 % of total auxiliary power
consumption of the plant. Air compressors are used in a variety of industries to supply process requirements, to operate
pneumatic tools and equipment, and to meet instrumentation needs. Only 10 – 30% of energy reaches the point of end-use,
and balance 70 – 90% of energy of the power of the prime mover being converted to unusable heat energy and to a lesser
extent lost in form of friction, misuse and noise.
APPLICATION OF COMPRESSED AIR:
Compressed air is mainly used in thermal power plants for following applications:-
A. Instrument air: It is used as driving fluid in pneumatic equipments and instruments used for control, protection,
measurement and process applications. It requires high quality air free from dust, humidity and oil.
B. Service air: Pressurised air is used for cleaning and cooling activities in the plant.
C. Miscellaneous Process applications: It is used for air motors, L.D.O. atomization, igniter cooling etc.
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2. CONFIGURATION OF COMPRESSED AIR SYSTEM:
O P Jindal Super Thermal Power Plant, Tamnar, Raigarh (C.G.) 4x250 MW plant has the common compressed
air set up for the entire plant as shown in fig.No.-1. It comprises of three Nos. centrifugal compressors having capacity of
127nm3/min, and two screw compressor having capacity of 44nm3/min each. Prior to this setup it was 3 centrifugal
compressors, with two compressors in loaded condition with some spare capacity and another one in unloaded condition. The
need was felt to introduce two additional screw compressors as capacity optimization and in view to run one Nos. each
centrifugal and screw compressor.
Fig-1 Schematic of compressed air system and its consumption pattern
In the journey of reduction in auxiliary power consumption, auxiliary wise consumption data was captured with the help of
Energy management system (EMS). It is observed that, Air compressors monthly consumption is about1.2 MU i.e.2 % of
total auxiliary power consumption of the plant.
Conventional methods like arresting leakages and wastage of air could not be relieved significantly but, this proved to be just
beating around the bush and the energy scenario was same with two screw and one centrifugal compressor, hence there was a
need to think out of the box and scratch grey cells to discover the high potential areas of energy consumption as well as
exploit operating margins provided by manufacturer in equipment and it’s control. Systematic study of the system carried
out. The efforts taken in this journey were proper experimental method with noncompromisation on stability, reliability and
sustainability of the pneumatic system and overall plant.
The concerted team effort has given the result and the innovative approach applied is very much justified.
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3. Power consumption data captured from energy management system is as shown in table No.1
Date - 19-Apr-13
SL No. Name of Feeder Running Hours
MWH
Consumption
Avg. PF
Avg.
CurrentImport Export
1 AIR COMPRESSOR 01 24 19.09 0.00 0.92 75.3
2 AIR COMPRESSOR 02 0 0.00 _ 0.00 0.00
3 AIR COMPRESSOR 03 24 19.95 0.00 0.92 79.24
4 AIR COMPRESSOR 04 0 0.00 0.00 0.00 0.00
5 AIR COMPRESSOR 05 0 _ _ _ _
Total AIR COMPRESSORS 39.04 0
Date - 20-Apr-13
SL No. Name of Feeder Running Hours
MWH
Consumption
Avg. PF
Avg.
CurrentImport Export
1 AIR COMPRESSOR 01 24 18.79 0.00 0.92 75.33
2 AIR COMPRESSOR 02 0 0.00 _ 0.00 0.00
3 AIR COMPRESSOR 03 24 20.56 0.00 0.92 81.64
4 AIR COMPRESSOR 04 0 0.00 0.00 0.00 0.00
5 AIR COMPRESSOR 05 0 _ _ _ _
Total AIR COMPRESSORS 39.35 0
Date - 21-Apr-13
SL No. Name of Feeder Running Hours
MWH
Consumption
Avg. PF
Avg.
CurrentImport Export
1 AIR COMPRESSOR 01 24 18.79 0.00 0.92 75.31
2 AIR COMPRESSOR 02 0 0.00 _ 0.00 0.00
3 AIR COMPRESSOR 03 24 20.83 0.00 0.92 82.56
4 AIR COMPRESSOR 04 0 0.00 0.00 0.00 0.00
5 AIR COMPRESSOR 05 0 _ _ _ _
Total AIR COMPRESSORS 39.62 0
Table no.1-EMS data before control system optimization
JOURNEY TOWARDS SUCCESS:
Step-I Optimization of control system:
One centrifugal compressor at full load and another on partial load was the normal plant operation. Partial loaded
compressors bypass valve was getting open at 71 Amp minimum limits to meet out demand. Threshold limit optimized to 67
Amp gradually so that inlet valve position reduced for same discharge quantity and subsequently reduction in power
consumption.
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4. Date - 22-Apr-13
SL No. Name of Feeder Running Hours
MWH Consumption
Avg. PF Avg. CurrentImport Export
1 AIR COMPRESSOR 01 24 18.00 0.00 0.92 72.37
2 AIR COMPRESSOR 02 0 0.00 _ 0.00 0.00
3 AIR COMPRESSOR 03 24 19.37 0.00 0.92 80.84
4 AIR COMPRESSOR 04 0 0.00 0.00 0.00 0.00
5 AIR COMPRESSOR 05 0 _ _ _ _
Total AIR COMPRESSORS 37.37 0
Date - 23-Apr-13
SL No. Name of Feeder Running Hours
MWH Consumption
Avg. PF Avg. CurrentImport Export
1 AIR COMPRESSOR 01 24 17.36 0.00 0.92 70.17
2 AIR COMPRESSOR 02 0 0.00 _ 0.00 0.00
3 AIR COMPRESSOR 03 24 19.94 0.00 0.92 79.94
4 AIR COMPRESSOR 04 0 0.00 0.00 0.00 0.00
5 AIR COMPRESSOR 05 0 _ _ _ _
Total AIR COMPRESSORS 37.3 0
Date - 24-Apr-13
SL No. Name of Feeder Running Hours
MWH Consumption
Avg. PF Avg. CurrentImport Export
1 AIR COMPRESSOR 01 24 17.37 0.00 0.92 70.21
2 AIR COMPRESSOR 02 0 0.00 _ 0.00 0.00
3 AIR COMPRESSOR 03 24 19.64 0.00 0.92 78.52
4 AIR COMPRESSOR 04 0 0.00 0.00 0.00 0.00
5 AIR COMPRESSOR 05 0 _ _ _ _
Total AIR COMPRESSORS 37.01 0
Table no.2-EMS data after control system optimization
Comparing both table no.1 and Table no.2, it directly shows that MWH consumption reduced from 39.5MWH to 37.4MWH
after reducing threshold limit value of current, Effect of control system optimization reflects that there is saving of approx
2000 kWH per day.
Step- II Study of consumption pattern:
Measurement is the first step in any conservation activity. As compressed air is ancillary system in power
generation plants, its instrumentation and control is also undermined compared to main plant. Here also, online flow
measurement instruments were not installed properly or not properly calibrated. Hence, in a first stroke, all compressors
discharge, instrument and service air header flow meters were made ready. Also, there was no flow meter installed in the
header of igniter cooling and L.D.O. atomization air. It was not easy to get line shut down for installation of online air flow
meter as it is the only source for all the four units. Hence individual compressor’s output, instrument and service air header
flow actual measured and remaining igniter cooling line flow calculated from it.
As shown in Fig. No.1 and table No.1 mWH consumption of compressor to support pneumatic requirement of 4X250MW at
OPJSTPP stands at approx. 39.5mwh per day.
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5. As per fig.1, before optimization of air pressure at igniter cooling and cleaning line, air flow was
1) Total air flow-8530m3/hr
2) Service air line flow-1250m3/hr
3) Instrument air line flow-4645m3/hr
4) Igniter cooling and cleaning line flow-2550m3/hr
Observations were very surprising and eye opener. Igniter cooling air was shortlisted as the major stakeholder; about31% in
total compressed air consumption and targeted to explore any opportunity for conservation.
IGNITER COOLING AIR NECESSITY AND CONFIGURATION: High Energy Arc (HEA) Igniters are used in BHEL
plants. It is used for igniting oil as a fuel in initial light up condition or in plant exigencies. Igniters are placed in each corner
adjacent to oil guns. In 4X250 MW tangential coal fired furnace total 12 Nos. of igniter are used in all three elevations and
four corners. Igniter comprises of guide pipe assembly, Igniter rod made up of stainless steel braided hose and fix rod, igniter
spark tip and conducting Teflon coated cable inside the rod. Igniter rod moves inside guide pipe assembly in advance-retract
direction. External cooling air is provided for protection of igniter components from excessive heating and as well as
cleaning the passage between igniter and its assembly.
Igniter data sheet, general arrangement of igniter and cooling air arrangement is shown in igniter datasheet, Fig. No. 2, & 3
IGNITER ROD DATASHEET:
SPARK ROD PART No.
Type & Model No Flexible / CBLS . 1000.025
Operating Temp. 540C AT TIP,150 C AT CABLE END
Tube SS.304
Flex Section SS.316
Pin/ Socket BRASS/55-316
Insulation Of wire TEFLON
Insulation Of Socket CERAMIC
Spark Tip 185 MM
Type & Model SEMI CONDUCTIVE TYPE &157.900.003
Operating Voltage 2000
Tip Life
106
sparks
Material SPECIAL ALLOY
Casting SS.316
Tip SPECIAL ALLOY
Coating SEMI CONDUCTIVE
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6. Fig.2 HEA igniter arrangement
01-HEA RETRACTOR 8 INCH STROKE, 02-HEA FLEX SPARK ROD W/O TIP,
03-HEA SPARK TIP 04-HEA EXCITOR,
05-HEA FLEX CABLE ASSEMBLY 06-SS HOSE, 07-AIR SET W/MB
Fig.3 igniter cooling air arrangement
External cooling air is connected with 1/2” line to igniter assembly and air passes through annulus between the
igniter rod and assembly to furnace. Direct discharge air of about 7 Kg/cm2 is applied for igniters .There is no
regulation on air flow through it and it is only depend on the annulus space.
IGNITER COOLING LINE AIR PRESSURE OPTIMIZATION:
It is observed that, this air is unaccounted and uncontrolled in M/s BHEL make plants, while, its contribution is about
one third of total consumption of air in plant. Also, from data sheet study it reveals that, most heat sensitive materials are
Teflon coating and porcelain insulator which minimum withstanding temperature is 250 degree C. Air pressure or flow
measurement arrangement to individual corners was not available. Hence, pressure gauge provided for it.Regulated air
pressure of individual corner gradually from 7.0 kg/cm2 to 2.2 kg/cm2 with observation of its impact on igniter life and its
operation. Also, air flow pattern is observed in overhauling from inside of furnace. in all units after mounting of air pressure
regulator, with close observation of igniter tip and rod temperature.
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7. MONITORING OF IGNITER ROD
Location
Pressure ( Kg/cm2) Spark Tip( deg cel) Spark Rod ( deg cel)
EF elevation, 7.0 117 49
EF elevation 2.2 134 68
Table No. 3 Igniter rod temp monitor
These repeated exercises proved handy in going further, repeated spark checks were carried out for around 4 months at
regular intervals, the conditions at the spark tip and spark rod were monitored and thus pressure was optimised.After
confirming the experiment in one unit, it is implemented in all the remaining units. This need not required any additional
instruments but, only pressure gauge in all corners.
After optimization of air pressure at igniter cooling and cleaning line air flow was
1) Total air flow-7410m3/hr
2) Service air line flow-1250m3/hr
3) Instrument air line flow-4645m3/hr
4) Igniter cooling and atomizing line flow-1415m3/hr
Sr. no. DESC. FLOW BEFORE REGULATION
OF IGNITER COOLING LINE
(6.5KG/CM2)
FLOW AFTER
REGULATION OF
IGNITER COOLING LINE
(2.5KG/CM2)
SAVING IN
FLOW(M3/HR)
1 IGNITER &
ATOMISING AIR LINE
FLOW
2550 M3/HR 1415 M3/HR 1135M3/HR
After completion of air pressure optimization at igniter air cooling line results are as below mentioned table
Report Type :- Daily
Summary
Energy Report Date - 21-Oct-13
SL No. Name of Feeder Running Hours
MWH
Consumption Avg. PF
Avg.
Current
Import Export
1 AIR COMPRESSOR 01 24 0.00 0.00 0.00 0.00
2 AIR COMPRESSOR 02 0 20.76 _ 0.92 0.00
3 AIR COMPRESSOR 03 0 0.00 0.00 0.00 0.00
4 AIR COMPRESSOR 04 24 8.15 0.00 0.84 35.17
5 AIR COMPRESSOR 05 24 0.00 0.00 0.00 0.00
Total AIR COMPRESSORS 28.91 0
Total AIR COMPRESSORS 28.91 0
Table no.3-EMS data after air flow optimization at igniter cooling line
ENERGY ECONOMICS:
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8. SR.NO. NAME OF ACTIVITY
BEFORE
CONSUMPTION
AFTER
CONSUMPTION
TOTAL
SAVINGS
DATE OF
IMPLEMENTATION
1
CONTROL SYSTEM
OPTIMIZATION 39.62MWH 37.02MWH 2.6MWH 22/04/2013
2
IGNITER AIR COOLING LINE
PRESSURE OPTIMIZATION 37.02MWH 28.91 MWH 8.11MWH 20/10/2013
TOTAL MWH SAVING PER DAY=39.62-28.91=10.71MWH/DAY
TOTAL MWH SAVING PER YEAR=10.71*365 =3909MWH
SO TOTAL KWH SAVING PER YEAR=3909*1000 =3909000KWH
TOTAL MONETARY SAVINGS PER YEAR=3909000*3=1.172Cr
JOURNEY STARTED WITH 39.5MWH/DAY AND AFTER COMPLETING THIS PROJECT CONSUMPTION IS
28.91MWH/DAY
Also, it is observed that, frequency of guns proving at single stroke improved a lot after optimization of air pressure. It may
be due to elimination of cooling air curtaining around the spark. This is an additional inadvertent outcome of the activity.
OTHER MEASURES FOR ENHANCING RELIABILITY AND STABILITY OF PNEUMATIC SYSTEM:
• To provide isolating valve for less critical air supply like AHP, coal reject system, igniter air cooling line which
needs to get closed in exigency conditions like black outs, compressor tripping etc .
• Providing air accumulators at far/important pneumatic instruments to provide buffer stock during exigencies.
• In addition to above ,to identify and arrest air leakages
CONCLUSION:
Since the task was done for probably first time in M/s BHEL plant and being novel, this can be considered as an exemplary
success story to think out of the box and the result speaks.
This was an endeavor in Auxiliary Power Conservation in one of the most inefficient system .The measures discussed above
were success story after huge brainstorming and many pitfalls. This may be an example for the upcoming and existing power
plants which has more or less same system characteristics.
REFERENCES:
1) HEA igniter installation–DWG NO.-2-41-500-00320/REV 04
2) Igniter datasheet-cbl/combustion system:12-26470-DS01
3) Energy meter reading-energy management system supplied by arreva
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9. 4) Compressor datasheet –OEM/IR
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10. 4) Compressor datasheet –OEM/IR
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