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Energy Audit andEnergy Efficiency improvement of Thermal Power Plant

Presentation by Group#B3 Anusha KolliSumit Kumar VijaySandeep Gurnani

Abhinav AgarwalMukund Chandak


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Presentation by Group#B3

Abraham Lincoln (1809-1865)


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Energy Audit

An energy audit is an inspection,survey and analysis of energy flows for energy conservation in a building,process or system to reduce theamount of energy input into the systemwithout negatively affecting theoutputs(s).

The energy audit evaluates theefficiency of all building and processsystems that use energy. The energyauditor starts at the utility meters,locating all energy sources coming intoa facility. The auditor then identifiesenergy streams for each fuel, quantifiesthose energy streams into discretefunctions, evaluates the efficiency of

each of those functions, and identifiesenergy and cost savings opportunities.


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Flow chart of Energy Audit process



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Energy audit methodology

Historical reviewPre planned walkthrough sheet

Make a detailed list of data requirements

Compute the mass and energy flow

Energy conservation opportunities

Energy saving options

Cost analysis

Final recommendationPrioritizing



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Energy consuming parts of a typical thermal power plant

Boiler Condenser

Cooling water from sea

Chimney

Generator

Steam Line

Turbine



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Typical Plant Losses Typical Boiler Losses



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Typical Cycle Losses



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Energy Audit of BoilersPerformance of Boiler and APH be established by measuring exit flue gas

TemperatureHeat loss due to heat in dry flue gas.Heat loss due to moisture in as fired fuel.Heat loss due to moisture from burning of hydrogen in fuelHeat loss due to moisture in air.

Heat loss due to surface radiation and convection.Heat loss due to formation of carbon monoxide.Heat loss due to combustibles in bottom and fly ash

Recommendations: Analyze Flue Gas for Proper Air/Fuel Ratio

Install Economizer to Preheat Boiler Feed Water Direct Warmest Air to Combustion IntakeReplace Obsolete Burners With More Efficient Ones



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Methods to improve boiler efficiency

Increasing boiler efficiencies by 1 to 3 percent equivalent to savings of $600,000

to $1,700,000 per 450 MW boiler.

Optimizing fuel/air ratio

Installing economizer Reducing scale and deposits

Reducing blow down

Operating at peak efficiency

Preheating combustion air

Switching from steam to air atomization



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Optimizing fuel/air ratio:- If the fuel is too much as compared to the air, incomplete combustion occurs. This will give

rise to carbon soot deposits inside the combustion chamber or even over the boiler tubes

- When there is more air than is required for combustion, the extra air becomes heated upand is finally discharged out to the atmosphere thereby wasting heat. N0x formation mayalso take place

- However, there are reasons for putting in some extra air for combustion - to compensatefor imperfect burner fuel-air mixing conditions, air density changes, control system "slop",

burner maintenance, fuel composition and viscosity variation, and imperfect atomizingsteam or air controls for burners.

Installing Economizer:- This is only appropriate if there are insufficient heat transfer surfaces in the boiler. The

economizer tubes may contain either circulating boiler water or circulating feed water.Because the temperature of the exhaust gases can be quite high, the economizer tubes

may be fitted with safety valves to avoid over-pressure damage. Also temperature controlof feed water is required to prevent pump airlock. To avoid corrosion, careful design isneeded to ensure that the exhaust flue gas temperature does not drop below the dewpoint.



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Reducing scale and deposits:- For any boiler operation, this is a must. The safety of the boiler is at stake. Any

- scale or deposits will lead to reduced heat transfer that will eventually lead to- overheating, reduction of mechanical strength of the steel and finally to bursting

Reducing blow down:- Blow down of boiler water is discharging hot water into the drains.

- However, blow down is necessary to maintain the boiler water concentration of - dissolved solids that are necessary for conditioning the boiler water. The

- dissolved solids are necessary for preventing boiler corrosion and scaling.

- As steam is generated from the evaporation of water, the remaining water

- in the boiler becomes more and more concentrated. This must be drained away- during blowdown.



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Operating at peak efficiency:- When operating two or more boilers, improved efficiency can sometimes be

obtained by unequal sharing of the load so that the combined load operates atpeak efficiency

Preheating combustion air:- Any heat loss from the skin of the boiler to the boiler room can be utilized back

for combustion

- By preheating the intake air the combustion in the furnace becomes moreefficient

Switching from steam to air atomization:- For burners with steam atomization, switching to air atomization will naturally

- result in less steam consumption overall and better boiler efficiencies. This is- only applicable for heavy fuel oil burners



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Energy Audit of steam Turbine cycles and its auxiliaries

Turbine cycle heat rateHP and IP cylinders efficiencyTurbine pressure surveyTTD & DCA of HP / LP heaters performance

Condenser performance i.e- Condenser back pressure after duly considering the effect of present C.W inlet temp.

C.W flow, heat load on condenser and air ingress to condenser vis--vis designconditions

- C.W side pressure drop in condenser

Cycle lossesPerformance of turbine glandsEjector performance



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Energy Audit of steam turbine

Performance parameters need to be determined are (according to ASMEPTC 6)

heat rate (b) generator output (c) steam flow,

(d) steam rate (e) feed water flow



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Energy Audit of CHP

Major equipment:- Crushers

- Conveyors

- Feeders

- Tipplers- Stacker-Reclaimers



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Measurement andObservation to be made- Drive speed, belt speed, roller

conditions, belt conditions andbelt loading with respect to

design- Power consumption of equipments (load and no-loadconditions)

- Loss of energy in the coal instock yard due to spontaneouscombustion

- Equipments operations andthroughout comparison withdesign conditions



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Data collection of CHP

Design details of overall CHP- Capacity, specific power consumption etc.

Process flow diagramTrack hoppers

- Number, length, capacity, power, layout etc.Paddle feeders- Number, capacity, travel, speed, power

Wagon tippler - Number, type, capacity, maximum weight, time cycle, motor rating



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Crushers- Number, type, capacity, coal size at inlet and outlet, motor rating, power

consumption, number of vibrating feeders

Coal Design parameters and sizesBelt Conveyors- Capacity , number, speed, width, motor rating power consumption

Stacker Reclaimer - Quantity, capacity, travel speed. Number of buckets and length of boom, motor

rating

Other EquipmentsVibrating feeders, dust suppression system pumps , belt feeders,

dust extraction fans etc



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Energy conservation possibilities

Performance improvement options:- Possibilities in Improving the throughput this is a major energy saving area

which offers substantial saving at minimum investment.

- Reducing the idling time.

- Increasing the loading.- Modifications and changes in coal feeding circuits.

- Need for automation and controls.

- Identification of combination of various least power consuming equipments andrecommending merit order operation.

- Use of natural daylight through conveyor galleries and use of fire resistanttranslucent sheet.



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Ash Handling Plant

Major Energy Consumers

Ash water pumps

Ash slurry series pumps

The contribution of wet ash handling plant in auxiliary power consumptionvaries between 1.5 to 2%Major Objectives in AHP

Evaluation of ash water ratio

Analysis of higher consumption of water if anyComparison of the ash water ratio with design value, P.G. Test value andprevious energy audit valuesEquipment's performance


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Data collection of AHP

Line diagramDetailed Specification pertaining to- Type

- Handling capacity

- Percentage ash collection rates- Fly ash and bottom ash extraction capacities

- Operating hours



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PG test values/design values of - Coal parameters

- Ash generation

- Ash to water ratio

- Slurry velocities- No.of pumps involved

Energy consumption details

Water consumption details

Performance characteristic curves of all pumps



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Operating parameters of AHP

Water supply rate

Water velocity

Discharge

HeadValve position

Temperature

Operating hours and schedule

Pressure drop in systemPump/motor speed

Load of the plant

Discharge throttle valve positionFlow control frequency

% loading of pump on flow andhead

% loading on motor



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While conducting the energy audit of the pumping, the following aspects needto be explored in detail for Optimization / improving the ash to water ratios

- Possibilities of reducing the operating hours of the AHP- Adequacy of pipe sizes- Improvement of pumping systems and drives.- Use of energy efficient pumps

- Replacement of inefficient pumps

- Use of high efficiency motors

- High Performance Lubricants: The low temperature fluidity and high temperature

stability of high performance lubricants can increase energy efficiency byreducing frictional losses.

- Booster pump application



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Electrical Systems

Transformers: Assessment of the health & Transformer load loss of GT, UAT, Station Servicetransformers etcIdentification of possible Energy conservation options in this area

Motors: Assessment of Loading condition of HT and LT motors of Boiler area, Turbine area andBalance of Plant area

Assessment of operating parameters like load variation, Power factor, of HT and LTmotors consuming power more than 50 KWIdentification of possible Energy conservation options in this area (with latest techniques)Recommendations:

Replace Over-Size Motors and Pumps with Optimum SizeUtilize Energy-Efficient Belts and Other Improved MechanismsUse Most Efficient Type of Electric Motor



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Energy Audit of BoP

Compressed Air system:Free Air Delivery i.e. Capacity evaluation of the Plant and Instrument air compressorsChecking volumetric efficiency of compressors

Assessment of compressed air leakage quantity

Assessment of Energy performance of the air compressors/ specific power consumptionStudy of the compressed air network and suggest suitable energy savingoptionsRecommendations:

Install Compressor Air Intakes in Coolest locationsReduce the Pressure of Compressed Air to the Minimum RequiredEliminate Leaks in Inert Gas and Compressed Air Lines/Valves



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Ash Plant:Performance of ash Slurry pumps through power measurement and flow measurement

Ash water ratio assessment and recommendations for optimization in water and power consumption

Cooling Tower Performance: It shall include establishment of Liquid/Gas ratioFan efficiency as the ratio of shaft power developed and the work done by the fanCooling Tower Effectiveness, approach and range.Cooling capacity.

Coal Handling Plant:

Input Power measurement of all the key equipment of the CHP area like: Paddlefeeders, Conveyors, Stacker & Re-claimer, Wagon Tipplers, Crushers,

Establishment of specific energy performance indicators.



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Instrumentation and control

Evaluate the instrumentation available in the plant and identify the locations here onlinemeasurements are necessary for efficiency calculations however unavailable

Recommendation regarding type of instrument, installation details, make etc.

Measuring instrumentation at coal handling plant, ash handling system, Raw water andwaste water system

Thermal Insulation including radiation losses:

Heat loss calculationInsulation of Boiler, Air and Flue gas path and Steam pipingSurface temperature measurement at the damaged and Hot spot area by infraredtemperature indicator.Estimation of Heat loss in the hot spots and damaged insulation area

DM PlantCapacity utilization and power consumption of all major drives.Performance evaluation of pumps.


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Cooling water system

Assessment of cooling tower capacity and efficiency / effectiveness

Evaluate circulating water pump flow rate, head developed, pressure of pumping systemand power consumption

Assessment of condenser heat load, deviation indicated in respect of the CW pumpperformance

Water circulation, condenser efficiency, and turbine heat rate

Assessment of Vacuum system and fan performanceFire Fighting system

Input Power measurement of all the key equipment of the Fire system like hydrant, spray(Electric & Diesel),Jockey Pump, Booster PumpEstablishment of specific energy performance indicators

APC & performanceEvaluation of unit auxiliary power consumption & performance including specific energyConsumption ( SEC) of critical drives where output parameters is available on line, coolingwater pumps, CHP (including Performance of Locomotives, Loaders, Dozers, Proclaim andtipplers), AHP, FOPH, WTP and Cooling Towers using power analyzers.


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Water system


Water consumption in a coal based thermal power plant

Area Quantity with ashwater recycling(m 3 /hr)

Consumption(m 3 /MW)

%

Ash handling 4180 2.0 41.4

Cooling towers 3270 1.5 30.4

DM water 260 0.13 2.6

Drinking water (colony +plant)

640 0.32 6.3

Coal handling 130 0.065 1.3

Fire fighting 476 0.37 4.7Others 1334 0.66 13.2

total 10090 5.0 100


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A thermal power plant of 210 MW capacity recycles approximately 2000m3/hr ash water.

Reducing water consumption from 5.86 liter/kWh to 4.9 liter/kWh resultsin reduction of 16 percent in water consumption and savings of Rs.15.8million/annum in water bill

By systematic water audit and quantifying water flows at each pumpingstation, one can carry out water balance with a reasonable accuracy.

Based on water audit studies in a number of thermal power stations,some of the measures can be taken which will give major savings both in

terms of water and Energy



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Measures

Optimizing ash water ratioRecycling ash water from ash dyke

Increasing cycles of concentration (COC)

Reducing drinking water consumption

Reducing leaks and over flows

Installation of effluent treatment plant



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Optimizing ash water ratio

In wet ash handling power plants, about 50-60 percent of water isconsumed just for ash handling.

Typical design ash water ratios are around 1:5 for fly ash and 1:8 for bottom ash. However, the actual combined ash water ratios are around1:20.

For every percent reduction of ash water ratio, there is a saving potentialof 60 m3/hr of water. In addition to water savings, the associated auxiliarypower consumption reduction would be 0.2 MU/annum for every ashwater ratio reduction

After initiating water conservation measures, many thermal power plantshave brought down their ash water ratios to a reasonable level to 1:10 to1:12.



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Recycling ash water from ash dyke

About 60 percent of water is consumed for ash handling purpose alone.The ash slurry is sent to ash dykes, which are normally located about 14-15 km away from the main power plant. After the ash gets settled in theash dyke, the clear water can be recycled. This water can be re-used for ash handling purpose after minor treatment (if necessary).

A thermal power plant of 210 MW capacity recycles approximately 2000m3/hr ash water. By reducing water consumption from 5.86 liter/kWh to4.9 liter/kWh results in reduction of 16 percent in water consumption andsavings of Rs. 15.8 million/annum in water bill (@ Rs. 1/kL of raw water).



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Increasing cycles of concentration (COC)

The maximum water loss in the thermal power plants is in the cooling towers,in the form of evaporation. We need around 180 m3/hr cooling water flow tothe condenser to generate 1 MW.Expected evaporation ratio for every 1 MW of power generation is 2.6 m3/hr.For a 210 MW power plant, the expected evaporation loss would be 550m3/hr. To compensate this evaporation loss, the blow down losses and driftneed to provide make up water Normally the cooling towers are designed for a COC(ratio of dissolved solidsin circulating water to make up water) of around 3. To keep COC of 3, weneed to provide a blow down of around 275 m3/hr, for a 210 MW power plant.By increasing COC, the blow down quantity can be reduced. By externalwater treatment and adding water treatment chemicals, COC of even 10 canbe reached. By increasing COC from 3 to 10, we can reduce the blow downquantity drastically from 275 m3/hr to30 m3/hr, which is a savings of 88percent.



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Reducing leaks and over flows

Lot of water leaks from Valves, Flanges, Taps, Fire fighting hoses, under ground fire fighting lines, cooling tower basin, gardening hoses etc takesplace

Overflows from cooling towers of AC plants, Air washers, and Overheadtanks due to non-functioning of float systems are also there

Huge water leaks from the condenser pipe ducts are noticed.

By bringing underground fire fighting lines to over ground, attendingvarious water leaks, providing ball and cock float systems for overheadtanks and smaller cooling towers, 3-5 percent water consumption can

easily be reduced.



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Installation of effluent treatment plant

A typical thermal power plant will have a 3-4 main drains. All this drainwater gets collected and finally goes out of the plant boundary.The measured drain quantities alone are found to be in the range of 800-1000 m3/hr.

By installing effluent water treatment plants and recycling this water for

the ash handling purpose, 80-90 percent of this water can be saved.


Based on the water flows measurements in different thermal power stations and comparing them with design values and practically achievablefigures, savings worth Rs. 3.3 crore/annum, equivalent to 40 percent water use reduction have been identifiedSince there is a close nexus between water and energy, energy savings to

the tune of 3.57 MU/annum is also identified

.

Potential


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Total Electrical System Audit Including Lighting

Assessment of the loading pattern of installed transformer to identify measures for reduction of lossesPower consumption by each AC system by using power measurement analyzersincluding Cooling effect and humidityPerformance of air compressors by using power measurement analyzersElectrical parameters like current, voltage, power factor and power by using power

measurement analyzers Assessment of health of capacitors and adequacy of the existing VAR compensationsystemHT/LT motor consuming power more than 50 KW need to be checked for measuringelectrical parameters and performanceLighting of Main plant including office building lux measurement and power consumption(day/night phase wise)Distribution lossesHarmonic analysisIdentification of Energy Conservation opportunities



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Cost Analysis of Heat Exchanger


Cost of Heat Exchanger, Pump, Piping ,Insulation and Storage Tank: Rs1,65,000(Approximate)

COP of Refrigerator increases by roughly 15%.Savings:308 units per month

Savings from Water Heaters : 2928 units(Replacing 9 geysers)

Total Monthly Savings:3236 unitsTotal Monthly Savings in Rupees: Rs 18,768


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Cost analysis


S.No Recommended measure Electricitysaved per month

Savings inRs per month

Capitalinvestment

Pay backperiod

1 Use solar water heater instead of geyser

3600Kwh 20,880 7,80,000 3 years

2 Use automatic washingmachine instead of manual

48Kwh 278.4 10,075 3.1years


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Final recommendation

Heat Exchanger must be implemented, as its payback period is least andeffectiveness highest.

Solar Water Heaters are generally efficient but water temperatures would

slightly decrease in the rainy season.

Automatic washing machines saves more energy and its payback periodis also less. In the long run they are more efficient than manual machines.

The total amount of electricity that can be saved=6884 Kwh per month.Roughly Rs40,000



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References

Energy Audit done Energo Engg Projects Ltd at Kolaghat unit ASME standards (PTC)

Wikipedia

www.google.com

www.sciencedirect.com

www.googlesholar.com

www.cea.nic.in

www.actsys.com

www.indiapower.org

www.iea-estap.org

http://www.reduct.com/news/BoilerEfficiency1.ht m

http://www.google.com/http://www.sciencedirect.com/http://www.googlesholor.com/http://www.cea.nic.in/http://www.actsys.com/http://www.indiapower.org/http://www.iea-estap.org/http://www.reduct.com/news/BoilerEfficiency1.htmhttp://www.reduct.com/news/BoilerEfficiency1.htmhttp://www.iea-estap.org/http://www.indiapower.org/http://www.actsys.com/http://www.cea.nic.in/http://www.googlesholor.com/http://www.sciencedirect.com/http://www.google.com/


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THANK YOU

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