Auxiliary power consumption is
directly related with power plant profit. Lesser the APC more will be the power
export & hence more profit. So it becomes duty of every power plant professions
to strive to reduce APC wherever possible.
Below table gives the area wise APC in Bagasse/coal based
power plants
Sl
No.
|
Area
|
APC
in %
|
1
|
Boiler fans
|
35-38%
|
2
|
Boiler feed water pumps
|
35-36%
|
3
|
Turbo generator & its auxiliaries
|
10-12%
|
4
|
Bagasse feeding system
|
2-2.5%
|
5
|
Coal feeding system
|
1%
|
6
|
Bagasse handling system
|
4-4.5%
|
7
|
Coal handling system
|
1.5- 2%
|
8
|
Ventilation, AC & Air Compressors
|
4-5%
|
9
|
Water treatment plant
|
2-3%
|
Note: Bagasse based Cogeneration
plant have incorporated coal handling system as supporting system & also
run the power plant in non-season days. So APC for bagasse handling/feeding
& coal handling/feeding has been considered separately.
Now a day there is huge scope for
reduction of plant APC. Here scope of APC reduction at various areas of plant
has been discussed.
A-Boiler:
1-Improve the
combustion efficiency:
Combustion efficiency improvement
will directly relate to the air consumption. Improved combustion will reduce
load on FD, SA & ID fans, hence power consumption will reduce. In
cogeneration plants or ion any power plants Boiler fans consume around 35-38%
of total auxiliary power consumption.
In order to reduce the air
requirement & to improve the combustion efficiency need to concentrate on
bellow areas
- Select good quality of fuel, if using bagasse the moisture should be 49 to 50%, as the moisture increases excess air required will also increases. This loads the FD, SA & ID fans more than requirement.
- Arrest all leakages in air & flue gas paths
- Modify combustion air ducts to reduce resistance to air flow
2-Boiler fans:
As discussed above Boiler fans consume 35-38% of total APC,
so need to concentrate on Boiler fans efficient operation.
- Operate boiler fans in VFD mode at optimum speed
- Incorporate inlet guide vanes to the system
- For high speed fans, ensure the silence fitted at suction size has sufficient opening & at lesser height
- Ensure all inspection & man way doors are sealed properly
- Ensure clearance between inlet cone & impeller suction neck is minimum
- Monitor draught losses in flue gas duct, air ducting, APH, Economiser & ESP regularly
- Follow lubrication schedule, replace damaged bearings to reduce vibrations & bearing temperature. High vibration bearings consume more power
Boiler feed water consume around
35% of total APC of the plant. Hence it is utmost important to reduce the BFP
power consumption. Attention must be given on following points to reduce BFP
power consumption.
- Select optimum capacity BFPs, Under load running pumps have low efficiency
- Better to install HT drives for BFP
- Incorporate VFD to BFPs
- Operate BFP in Auto mode based on discharge header pressure & drum pressure
- Do not operate the pump with discharge valve throttled
- Ensure BFP ARC valve has no leakage
- Ensure BFP has sufficient suction pressure
- Maintain Deaerator level on higher set point side.
- Replace worn out balance & counter balance discs
- Schedule pumps servicing as per OEM guidelines. And replace impeller wear rings or impellers if clearance found more. More clearance between wear ring & impeller will lead to higher power consumption
- Follow lubrication schedule, replace damaged bearings to reduce vibrations & bearing temperature.
- Do not uses BFP discharge water for de-super heating of LP process steam, instead use CEP discharge water
- Clean suction strainers regularly
- Implement hopper heater automation by thermostat
- Optimize the charge ratio of Transformer
Fuel feeding system consumes
around 2-4% of total APC. Hence it need to give attention to reduce APC in this
area. Following are the some listed action points to reduce APC.
- Incorporate VFDs to all fuel feeding systems, as fuel feeding system never run on 100% load.
- Select planetary type gear boxes to fuel feeding system, as planetary gear boxes found of higher efficiency
- Follow regular preventive maintenance to reduce wear, tear & friction of rotating parts, which ultimately lead to more power consumption
- Replace all loose V belts. Loose V belts lead to increased power consumption
Turbine auxiliary consume around
10-12% of total APC of the plant. Following are the areas where we can monitor
the APC
- Maintain lube & control oil filters clean
- Maintain optimum lube oil temperature
- Maintain cooling tower fills & drift eliminators clean to get required cooling water temperature
- Incorporate VFDs to all cooling water pumps
- Set CT blade angle at 11-14 degree.
- Replace CT fan aluminium blades by FRP
- Ensure cooling tower surrounding area is free of trees & structures for free flow of air
- Incorporate VFDs to Condensate extraction pumps (CEP)
- Ensure hot well make up is going on from gravity water from feed tank or surge tank
- Schedule regular cleaning of heat exchangers like steam condenser, oil cooler, ejectors & Generator air cooler & gland steam condensers
- Replace TG building exhaust fans by turbo ventilators
- Ensure motors selected for all Bagasse belt conveyors are of optimum rating
- Incorporate planetary gear boxes to belt & chain conveyors
- Replace all damaged idlers regularly. Damaged idlers lead to more friction in the system
- Ensure Vertical gravity take up height is optimum (1 to 1.5% of conveyor length)
- Ensure belt scrapers (cleaners) & skirt boards are not over rubbing the belt to avoid friction & wear/tear
- Follow regular preventive maintenance & lubrication schedule for conveyor pulleys bearings & idlers
- Remove saturated bagasse/coal from deck plates of conveyors regularly to avoid friction
For air compressors optimise
discharge air pressure & set loading & unloading times as per
requirement
- Clean air filters regularly
- Replace all globe valves by gate valves or ball valves
- Ensure compressor discharge air line is of correct size to avoid pressure drop in the line
- For pneumatic ash handling system operate ash handling plant in probe mode or else optimize cycle time & conveying time
- Incorporate VFDs to ventilation system
- Optimize the usage of Air conditioning system in offices, meeting halls etc
- Avoid compressed air for cleaning applications
Thumb rules water treatment plant
- Ensure enough capacity of tanks for DM water storage, so that the operation time of the plant can be reduced
- Plan to get more quantity of return condensate from process
- Optimize boiler & CT blow down to reduce pumping power
- Incorporate drain condensate recovery system to reduce pumping power as well as to conserve thermal energy
- Operate DM plant at its full capacity & carryout regeneration as per out put OBR given by OEM to reduce pumping power as well as water consumption
- Use treated N-pit water as service water
1-Motor
- Provide proper ventilation to the motors. For every 10 °C increase in motor operating temperatures over recommended peak, the motor life is estimated to be halved.
- Synchronous motors are more suitable to improve power factor.
- Balance the three phase power supply, an unbalanced voltage can increase motor input power by 3–5%.
- Ensure the motor proper rewinding, an improper rewinding could lead to efficiency reduction.
- Ensure proper alignment between motor and load ends (fans, pump, gear box, blower etc.) to avoid more power consumption and failures.
2-Lighting
Incorporate timers for plant lighting systems like
conveyors, street, bagasse & coal yards etc
Replace all CFL & incandescent bulbs by LED
bulbs
Read POWER PLANT CALCULATIOS
its very useful sir, i got some notes from here.
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