Auxiliary Power Reduction in Thermal Power Plant
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Auxiliary Power Consumption
Reduction in Thermal PowerStations
Ramesh Bhatia
Schneider Electric
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APC Reduction In Thermal Power
Stations
> APC - Scenario of Indian Thermal Power Stations> APC - Facts
> System-wise Opportunities and results
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Indian Power Sector
Fuel MW
Total Thermal 105646.98
Coal 87,093.38
Gas 17,353.85
Oil 1,199.75
Hydro (Renewable) 37,033.40
Nuclear 4,560.00
Renewable Energy 16,429.42
Sources** (MNRE)
Total 1,63,669.80
(as on 31-07-2010 by CEA)
**include Small Hydro Project, Biomass Gasifier, Biomass Power, Urban & Industrial Waste Power, Wind Energy
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APC - Indian Scenario(Source: CEA -Performance Review of Thermal Power Stations 2007-2008)
APC - Capacity wise SHR - Region wise (2007-2008)
Capacity Group in MW
500
250
Auxiliary Power consumption in %
6.13
8.80
Region Weighted Weighted
Average average
Design SHR Operating
(kcal/kWh) SHR
(kcal/kWh)
210 8.77Northern 2347.2 2603.2
195-200 7.67Western 2371.6 2787.0
100-150 10.32
<100 10.31
National Level APC - 8.32%Best Acheived Sipat STPS of NTPC 5.04%(Source: CEA -Performance Review of Thermal Power Stations 2008-2009)
Southern 2400.6 2653.2
Eastern 2391.4 2738.5
National Level SHR
Design 2376.8 kcal/kWh
Operating2703.9 kcal/kWh
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APC Reduction In Thermal Power
Stations
> APC - Scenario of Indian Thermal Power Stations
> APC - Facts> System-wise Opportunities
and results
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APC - Elements
Draft System(ID,FD,PA /SA, HGR
Others (Air washer, ACplant etc)
Lighting
Fans
AuxiliaryPower
Feed Water System ( BFP,
CEP)
Cooling water system (ACW,
MCW, CT)
Consumption
Water Coal HandlingTreatment & Grinding
System Plant
mpressed Ash handling Air System System
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APC Break-up
Gross Generation Vs APC Typical APC Breakup
Cooling water systemNet Generation , 91.68% , 1.20%
APC, 8.32%
Feed water System , 3.22%
Coal Handling & Grinding , 0.58%
Ash Handling , 0.72%
Compressed Air System, 0.04%
Water treatment System, 0.27%
Lighiting , 0.07%
Draft System, 2.20%
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THERMAL AUXILIARIES
FOR A TYPICAL 210 MW UNIT
HT Motors LT Motors
(6.6 KV) (415 V)
43 Nos 510 Nos
17.5%
Total Connected Load
Auxiliary Consumption as % of total generation
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Auxiliary Power Consumption
Factors affecting APC
Operating the
equipment at maximum
efficiency
EnergyConservation
in PowerStations
Reduction of auxiliaryPower
consumption
Plant load factor
Operational efficiency of equipments
Startup & shutdown
Age of the plant
Coal Quality
High
Moderate*
Low
High*
Moderate to High
*Depends on R & M
Reduction of 0.2 - 0.3 % in APC with retrofits and system optimisation techniques could be achieved. Major retrofits can result into higher APC reduction
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APC IN THERMAL STATIONS
Therefore,
„ Auxiliaries may consume upto 12% of total generation
„Reduction of even 0.5 - 1.0 % can result in huge savings andadditional output of a few Megawatts
Note,- APC is measured only from difference of generated and transmitted
power, but no direct measure
- APC calculation is approximate and efficiency of eachequipment is unavailable
- Loss of efficiency due to technical/maintenance reasons cannot beascertained and isolated
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APC Reduction In Thermal Power
Stations
> APC - Scenario of Indian Thermal Power Stations
> APC - Facts
> S ystem-wise Opportunities
and results
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Auxiliary Power ConsumptionOverview
Process
Requirement Analysis
Effectiveness analysis
Break-even in terms of power consumption and process
gain
Multi level / element Control
Process Upgrades
System
Pressure drop analysis
Flow requirement, sizing And layout
System level control
System retrofits for full /
partial load requirement
System retrofits for abnormal
And normal conditions
Equipment
Actual requirement corrections
Corrections due to
Performance deterioration
Equipment control and retrofits
Internals replacement and retrofits
Energy Efficient Equipments
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System Configuration for Energy Management System in a Power PlantCONTROL ROOM
eLAN
Client
Software- 1
eLAN eLANServer Redundant
Software Software
LAN
eLAN eLAN
Client Client
Software-2 Software-3
8 Port Ethernet Switch
12 Port 12 Port 12 Port
LIU LIU LIU
12 Port Dept. A 12 Port Dept. B 12 Port Dept. C
LIU LIU LIU
8 Port Ethernet Switch 8 Port Ethernet Switch 8 Port Ethernet Switch
RS RS RS RS RS RS
485-1 485-2 485-1 485-2 485-1 485-2
1 20 1 20 1 20 1 20 1 20 1 20
EM 6400 EM 6400 EM 6400 EM 6400 EM 6400 EM 6400 EM 6400 EM 6400 EM 6400 EM 6400 EM 6400 EM 6400
10/ 100 Mbps Cat6 RS 485 Fibre 6 core Cat6 ION 7550Single ModePatch Cable patch Single Cable RTUMedia Convertorchord chord Mode Cable
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APC Reduction Measures
Boiler Feed Water System
BFP & CEP• Speed control in place of valve control
• Variable speed drive (BFP, CEP)
• Variable speed Hydraulic coupling (BFP)
• BFP scoop operation in three element mode instead of DP mode
• Avoid Recirculation
• Faulty valve • BFP Cartridge Replacement
• CEP Pressure reduction by Stage removal Scoop operation in Direct Mode
BFP re-circulation through bypass valve leakage was established through study in one of the plant (manual valve closed for 1 hour) and 45 kW (3%) power reduction in BFP was observed Operation of BFP with lower DP (14 bar to 6 bar ) in a 2 x 125 MW plant resulted in to reduction1.8 MU
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APC Reduction Measures
Draft System
FD, PA & ID FansArresting Air in-leaks in draft system (by O2 measurement)
Excess Air for combustion - Increase in FD, PA & ID fan power Leakage in APH - increase in FD, PA & ID fan power consumption Leakage in Duct & ESP body - increase in ID fan power
consumption
Comparative analysis of fan performance with respect to design
Excess Air
Air ingress
Flowincreasein ID fan
Identification of the gaps by investigation & Observation Inlet/outlet Duct connection
Fan body - for holes/cracks
Deposits formation in impellers/casings Erosion of impeller blades
Maintain Primary Air to Secondary Air ratio to reduce the PA fan power consumption
Fuel
Pulverized Coal
Type of Furnace or Excess Air
Burners (%by wt)
Completely water-cooled 15-20 Furnace or slag-
tap or dry-ash removal
Partially water-cooled 15 -40 Furnace or dry-ash
Removal
14% air ingress between APH and ID Fan was indentified in one of the plants and it was rectified to 4% , this resulted in 17% reduction in ID Fan power consumption
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APC Reduction Measures
Draft System
Elimination of damper/Inlet Guide vane based capacity
control with variable speed control system
Variable speed drive
Variable speed hydraulic coupling
Use of energy efficient fans
Fan Curve atConst. Speed Fan Efficiency 77%
700 Partially B Oversize Fan 82%closed valve
Change of impeller with energy efficient / appropriately sized
impeller
500
420
StaticPressure
A
System Curves C
Full open valve
Required Fan
Operating Points
30000 50000 Flow (m3/hr)
Efficiency improvement by replacing fans and impellers of FD, PA and ID Fan results in Energy Saving of 14.5 MU at an investment of Rs. 20 MINR
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APC Reduction Measures
Coal Handling PlantCoal Handling Plant
Proper Capacity utilization/under loading of system
Idle running of conveyors/crushers
Consumes 15 to 20% of full load power Auto Star-Delta- Star in place of DOL/Star- Delta
Minimization of motor losses for under
loaded motors (<40%)
Control of transfer point dust extraction fans and dust suppression pumps
Adequate and constant loading of crushers (often seen loading <50%)
Optimisation of crusher loading has resulted in reduction 25% of operating time and 16% in energy consumption i.e. 0.5 MU per annum
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APC Reduction Measures
Coal Milling
Coal Milling/Grinding System• Maintain proper air fuel ratio
• Periodic testing of coal particle size • To minimize fines (less than minimum required size)
• Optimized Mill parameters
•Ball loading in Ball/ tube mill
•Roller pressure with respect to grindability of coal • Mill internals replacement with regression analysis of previous and present consumption pattern (including particle distribution)
Ball Load
Power &Roller Pressure
Break-even point for replacement must be identified so as to avoid excess energy consumption in
coal mill
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Replacement Analysis
Grinding Roll Run Hours Vs Specific Power Consumption
10
9.5 9
8.5 8
7.5 7
6.5
6
5.5
5
0 500 1000 1500
y = 2E-07x2 - 0.0004x + 6.9991 R2 = 0.9685
2000 2500 3000 3500 4000 4500 5000
Run Hours
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APC Reduction Measures
Cooling Water System
Cooling Water Pumps
• Suction related issues • Mis-match of required head and rated
head
• Number of pumps operation based on vacuum during favorable condition
(careful analysis to be made between power gain and pump consumption)
• Auxiliary Cooling water Pumps
• Avoid circulation of cooling in standby systems (i.e. oil coolers etc)
• Used ACW water to condenser
Cooling tower• Nozzles to give better distribution over the fill
• Follow Manufacturers recommended clearances around cooling towers and relocate or modify structures that interfere with exhaust or air intake
• Optimize cooling tower fan blade angle on a seasonal and/ or load basis
• Correct excessive and/ or uneven fan blade tip clearance
• Replace splash bars with self extinguishing PVC cellular film fills
• Periodically clean plugged cooling tower distribution nozzles
• Maintain the Optimum L/G ratio 1.4 to 1.6 ( Rectify distribution problems)
Old cooling water pumps operating at 52% efficiency and developing only 70% of
the rated head has been replaced and saved 0.8 MU per annumDetailed study of cooling tower capability, L/G ratio, gas exit velocity, air flow and
recirculation to operate 7 CTs instead of 8 CTs has resulted in to energy saving
of 0.43 MU per annum
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Water Treatment Plant and Water
Pumping
Avoid over sizing and improper selection of pump Using start stop control
Eg: filling the tank with level based control
Variable speed drives with feedback control Impeller Trimming to permanently reduce the capacity Proper maintenance
Periodic checking of valves Cavitation
Leakage in gland sealing Deposits on impeller/casing
Change the RO discharge Pressure setting with respect to raw water TDS
Multiple pumps in parallel operation as per flow requirement
APC Reduction Measures
Detailed study of entire system from intake to make-up water has potential in optimisation
complete system (intermittent operation of additional pump, avoiding recirculation,
installation of VFDs (raw water make-up, cooling tower make-up, ash water make-up, service wate make-up, drinking water make-up). Estimated annual savings of these measures is 1.38 MU with
investment payback of 20 months
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APC Reduction Measures
Compressed air System
Air CompressorAir Optimizing discharge air pressureInstrument air application - 6 bar(g)
Ash Conveying - 3 bar(g)Open ended cleaning houses- 2 bar(g) Optimum capacity utilization Loading > 80%
Capacity control
Cascading operationCylinder cut off
Variable speed
Energy efficient compressorsScrew in place of reciprocation
Other Steps
Take cool, Dry & clean air
Reduction of generation pressure (identified areas), additional piping to reduce pressure drop, improvement of Volumetric efficiency, separation of cleaning air network with PRV and cleaning
nozzles has potential to save 1.2 MU (8 x 120 MW )
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APC Reduction Measures
Supply Side: Compressor ControlInternal Control: Most common foun
Load/Unload control
Our benchmarking values:
High Efficiency: Unloading rate < 20%
Average Efficiency: 50% >Unloading rate > 20%
Bad Efficiency: 70% >Unloading rate > 50%
Very Bad Efficiency: Unloading rate >70%
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APC Reduction Measures
Compressed air System
Distribution SystemReduce the compressed air leakage Low pressure drop network
Maximum Pr drop 0.6 to 1.0 bar
DriersUse of heat of compression air dryer
instead of electrically heated air dryer
User EndOpen ended usage - use nozzles
& pressure regulator
Separation of cleaning air network and reduction of service air generation pressure in a PP resulted in stopping of one air compressor 0.35 MU
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APC Reduction Measures
Power Distribution
MotorsLoading < 30% - Stat Delta Star
connection to minimize motor losses
Example: CHP conveyor Motors Energy Efficient Motors
TransformersOptimizing Voltage level of distribution
Transformer Loading Optimization
Optimum loading 50 to 60%Shifting of loads to under loaded
Transformers
Power Factor Improvement(Applicable only on selected areas)
Benefitsreduced kVA drawn , KVAR & current reduction of transformer load
reduction of cable losses, reduction of switch gear rating Enhanced life of equipment
Fixed capacitor banks
(Shunt Connected) at major load ends
15 - 20 years old rewound and under load (<40% loading) motors are Candidates for replacement with Energy Efficient Motors
BoP area distribution transformersBoP area, ESP, AHP transformers could be considered for PF Improvement
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Conclusion●Yesterday, we operated plant processes, systems and equipments manually
●Today, we are operating these with localised controls and partial integrated control
●Tomorrow, we will have to operate with full integrated and intelligent controls with innovative solutions
where we do more than we can imagine today, with
less than we used yesterday!
●The key to success is changing our behaviour…
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Make the most of your energy™